Composting of yard

Trimmings and

Municipal solid Waste

U.S. Environmental Protection Agency

Office of Solid Waste and Emergency Response
EPA would like to thank the following individuals for their contributions to the manual:

Jan Beyea National Audubon Society

Charlie Cannon Solid Waste Composting Council

Steve Diddy Washington State Department of Ecology

Dr. Melvin Finstein Rutgers University

Dr. Charles Henry University of Washington

Francine Joyal Florida Department of Environment Regulation

Jack Macy Masshusettts Department of Environmental Protection

Randy Monk Composting Council

Dr. Aga Razvi University of Wisconsin

Dr. Thomas Richard Cornell University

Connie Saulter Northeast Recycling Council

Dr. Wayne Smith University of Florida

Roberta Wirth Minnesota Pollution Control Agency

In addition, EPA thanks Wayne Koser of City Management Corporation and Steve Diddy

for their contributions to Appendix B: Composting Equipment.

. . ii

Acknowledgments
Chapter 6 - The composting Process:

Appendix A- Additional Sources of

Chapter Overview

Chapter 1- Planning

Describes the importance of planning and discusses some

of the preliminary issues that decision-makers should examine before embarking on any type of composting program including waste characterization, operation plans, 

facility ownership and management, community involvement, vendors, and pilot programs.

Chapter 2- Basic Composting Principles

Provides a brief scientific overview of the composting

proms. Discusses the physical, chemical, and biological

factors that influence composting including the type and

number of microorganisms present, oxygen level, moisture content, temperature, nutrient levels, acidity/alkalinity, and particle size of the composting material.

Chapter 3-Collection Methods

Describes options for collecting yard trimmings and

municipal solid waste (MSW) along with the advantages

and disadvantages associated with each option. Highlights

the critical role that source separation plays when

composting MSW

Chapter 4- Processing Methods,

Technologies, and Odor Control

Discusses the three stages of composing (preprocessing,

processing, and postprocessing). Introduces the types of

equipment associated with each stage, which are examined

in detail in Appendix B. Describes the methods currently

used to compost yard trimmings and MSW in the United

States, and provides a detailed discussion of odor control.

Chapter 5- Facility Design and Siting

Describes factors to consider when siting and designing a

composting facility including location, site topography

and land requirements. Also discusses design considerations for preprocessing, processing and postprocessing areas; buffer zones; access and onsite roads; and site facilities

and security.

Environmental, Health, and Safety Concerns

Focuses on how to prevent or minimize the potential environmental impacts associated with composting including the potential for water pollution, air pollution,odor

Vector, fires, noise, and litter. Dicsusses the safety and

health risks including bioaerosols to workers at composting facilities and ways to minimize these risks.

Chapter 7- State Legislatian and Incentives

Presents an overview of state legislation activity throughout the country. Also discusses state incentives to stimulate yard trimmings and MSW composting.

Chapter 8- Potential End Users

Describes the potential end users of compost derived from

 yard trimmings and MSW (agriculture, landscaping nurseries, silviculture, public agencies, and residents). Discusses how compost is currently utilized by these end

users as well as the potential for expanded use.

Chapter 9- Product Quality and Marketing

Emphasizes the importance of securing markets for the

finished compost product. Provides a detailed discussion

of quality and safety concerns that could affect the marketability of compost. Also discusses key factors associated

with marketing including pricing, distribution, education

and public relations, and program assessment.

Chapter 10- Community Involvement

Discusses the importance of developing strong local support

for a composting operation. Also discusses ways to involve

and educate the community throughout the planning siting,

operation, and marketing phases of a composting program.

Chapter 11- Economics

Introduces the economic and financial issues that must be examined when planning a composting facility Discusses capital

cost, operation and maintenance costs, and potential benefits

associated with starting up and maintaining facility.

Information on Composting

Lists publications related to composting as well as EPA

contacts.

Appendix B - Composting Equipment

Describes the cost, efficiency, and major advantages and disadvantages of the equipment commonly used at a composting facility.

Appendix C- Glossary of Composting Terms

Defines terms used throughout the guidebook.

. . .

III
Contents

Page

Introduction . . . . . . . . . . . . . . . . . . . .

Composting as a Component of Integrated Solid Waste Management . . .

What Is Composting? . . . . . . . . . . . . . . . . .

Status of Composting Yard Trimmings and MSW in the United States

Chapter One - Planning

Goal Setting . . .

Waste Characterization

Operational Plans . .

Community Involvement

Facility Ownership and Management

Composting Vendors . . . . .

Pilot Programs . . . . . . .

Summary . . . . . . . .

Chapter Two - Basic composting Principles

Overview of the Composting Process . . .

The Role of Microorganisms . . . . .

Factors Influencing the Composting Process .

Oxygen . . . . . . . . .

Particle Size . . . . . . . .

Nutrient Levels and Balance . . .

Moisture . . . . . . . . .

Temperature . . . . . . . .

1

1

2

3

11

11

11

12

12

13

14

14

14

16

16

16

17

18

18

19

19

19

v
Table of Contents

Chapter Two - Basic composting Principles (Continued)

Acidity/Alklalinity(pH) . . . . . . . .

Summary . . . . . . . . . . . . . . .

Chapter Three - Collection Methods . . . . .

Factors in Yard Trimmings Collection . . . . . .

Public Drop-Off Sites for Yard Trimmings . .

Curbside Collection of Yard Trimmings . . .

Factors in MSW Collection . . . . . . . . . .

Source-Separated MSW . . . . . . . .

Commingled MSW . . . . . . . . .

Summary. . . . . . . . . . . . . . .

Chapter Four - Processing Methods, Technologies, and Odor Control

Preprocessing . . . . .. .. . . . . . . . . . .

Sorting . . . . . . . . . . . . . . . . . .

Reducing the Particle Size of the FeedStock . . . . . . .

Treating Feedstock Materials to Optimize composting Conditions

Mixing . . . . . . . . . . . . . . . . . .

Processing . . . . . . . . . . . . . . . . . . . .

The composting Stage . . . . . . . . . . . . .

The Curing Stage . . . . . . . . . . . . . . .

Odor Control . . . . . . . . . . . . . . . . . . .

Process Control . . . . . . . . . . . . . . . .

Engineering Controls . . . . . . . . . . . . . .

Postprocessing . . . . . . . . . . . . . . . . . . .

Summary. . . . . . . . . . . . . . . . . . . .

Chapter Five - Facility Siting and Design . . . . . . . .

Siting . . . . . . . . . . . . . . . . . . . . . . .

Location . . . . . . . . . . . . . . . . . . . .

Topography . . . . . . . . . . . . . . . . . . .

Land Area Requirements . . . . . . . . . . . . . . .

19

20

21

21

21

22

28

28

29

30

31

31

31

37

37

39

40

40

47

47

48

48

51

53

56

56

56

59

59

vi
Table of Contents

Chapter Five - Facility Siting and Design (Continued)

Other Factors Affecting Siting Decisions 60

60

60

60

62

63

63

64

64

65

65

65

68

68

70

70

70

70

71

71

71

72

73

73

73

74

76

76

77

Design . . . . . . . . .

Preprocessing Area . . .

Processing Area . . .

Postprocessing Area .

Buffer Zone . . . .

Access and Onsite Roads

Site Facilities and Security

Summary . . . . . . .

Chapter Six - The Composting Process: Environmental, Health, and Safety Concerns

Environmental Concerns During composting . . . . . . . . . . . . . . . .

Water Quality . . . . . . . . . . . . . . . . . . .. .

Run-On/Ponding . . . . . . . . . . . . . . . . . . . . . .

Air Quality . . . . . . . . . . . . . . . . . . . . . . . .

Odor . . . . . . . . . . . . . . . . . . . . . . . . . .

Noise . . . . . . . . . . . . . . . . . . . . . . . . . .

Vectors . . . . . . . . . . . . . . . . . . . . . . . . .

Fires . . . . . . . . . . . . . . . . . . . . . . . . . .

Litter . . . . . . . . . . . . . . . . . . . . . . .. .

Occupational Health and Safety Concerns During composting . . . . . . . . . .

Bioaerosols . . . . . . . . . . . . . . . . . . . . . . . .

Potentially Toxic Chemicals . . . . . . . . . . . . . . . . . . .

Noise Control . . . . . . . . . . . . . . . . . . . . . . .

Other Safety Concerns . . . . . . . . . . . . . . . . . . . .

Worker Training . . . . . . . . . . . . . . . . . . . . . . . . .

Summary . . . . . . . . . . . . . . . . . . . . . . . . ...

Chapter Seven - State Legislation and Incentives . . . . . . . . . . . . . .

Composting Legislation Overview. . . . . . . . . . . . . . . . . . . . . . .

Permit and Siting Requirements . . . . . . . . . . . . . . . . . . . . .

vii
Table of Contents

Chapter Seven - State legislation and Incentives (Continued)

Facility Design and Operations Standards . . . . . . . . . .

Product Quality Criteria . . . . . . . . . . . . .

Bans Landfilling Combustion . . . . . . . . .

Recycling Goals . . . . . . . . . . . . . . .

Requirements for Local Governments to Implement composting

Requirements for State Agencies to Compost . . . . . .

Separation Requirement . . . . . . . . . . . . .

Yard Trimmnings and MSW composting Incentives . . . . . . .

State Encouragement and Local Authority to Implement Programs

Grants . . . . . . . . . .

Procurement . . . . . . . .

Encouragement of Backyard Composting

Education Programs . .

Summary. . . . . . . .

Chapter Eight - Potential End Users

The Benefits of Finished Compost

Agricultural Industry . . . . .

Landscaping Industry . . . .

Horticultural Industry . . . .

Silviculture.. . . . . . .

Public Agencies . . . . . .

Residential Sector . . . . . .

Summary . . . . . . . .

Chapter Nine - Product Quality and Marketing . .

Product Quality . . . . . . . . . . . . .

Yard Trimmings Compost Quality . . . . .

MSW Compost Quality . . . . . . . .

Product Specifications . . . . . . . . . . .

. . . Vlll

77

78

79

79

79

79

79

79

80

80

80

80

80

81

87

87

87

91

92

92

93

94

96

98

98

98

99

102
Table of Contents

Chapter Nine - Product Quality and Marketing (Continued)

Product Testing . . . . . . . .

Market Assessment . . . . . . .

Private vs. Community Marketing

Pricing . . . . . . . .

Location/Distribution Issues . .

Education and Public Relations .

Updating the Market Assessment

Summary. . . . . . . . . .

Chapter Ten - Community Involvement

Planning the Composting Project . . .

Community Involvement in Siting Decisions . .

Public Participation in the Composting Project . .

Community Education at the Marketing Phase . .

Summary. . . . . .

Chapter Eleven - Economics

Cost/Benefit Analysis . . .

Capital Costs . . . . .

Site Acquisition . .

Site Preparation/Land Improvements . .

Vehicle and Equipment Procurement . .

Training . . . . . . . . . . .

Permits. . . . . . . . . . .

Operating and Maintenance (O&M) Costs . . .

Collection Costs . . . . . . . .

Labor Costs . . . . . . . . . . .

Fuel, Parts, and Supplies . . . . . . .

Outreach and Marketing Costs . . . . .

Other Costs . . . . . . . . . . .

. 102

103

. 104

. 104

. 107

. 108

. 108

. 108

111

111

. 112

. 113

. 114

. 114

. 115

. 115

. 116

. 116

. 116

. 116

. 117

. 117

. 117

. 117

. 118

. 118

. 119

. 119

ix
Table of Contents

Chapter Eleven - Economics (Continued)

Benefits from Composting . . . . . . . . . . . . . . . . . . . . . . . ...119

Avoided Costs . . . . . . . . . . . . . . . . . . . . . . . . ...119

Revenues . . . . . . . . . . . . . . . . . . . . . . . . . . ...119

Summary, . . . . . . . . . . . . . . . . . . . . . . . , . . . ...120

Appendix A - Additional EPA Sources of Information on Composting . . . . . . . . 124

Appendix B- Composting Equipment . . . . . . . . . . . . . . . . . . . 126

Appendix C- Glossary of Compost Terms . . . . . . . . . . . . . . . . . 138

x
Introduction

composting is a firm of recycling. Like other recycling effort, the composting of yard trimming and municipal solid waste can help decrease the amount of solid waste that must be sent to a landfill or combustor,

thereby reducing disposal costs. At the same time, composting yields a valuable product that can be used by

farmers, landscapers, horticulturists, government agencies, and property owners as a soil amendment or mulch.

The compost product improves the condition of soil reduces erosion, and help suppress plant diseases.

The purpose of this manual is to aid decision-makers in planning, sitting, designing and operating composting

facilities. It also will be useful to managers and operators of existing facilities, as well as to citizens, regulators,

consult-anti, and vendors interested in the composting process. The manual discusses several approaches to comporting and outlines the circumstances in which each method should be considered

AS detailed in the manual a composting operation should be designed according to the need and resources of the

community. For example, a municipal composting effort can entail simply collecting yard trimmings on a seasonal basis and using a simple “windrow and turn” technology to produce the compost, or it can mean siting and

designing a large facility that is capable of handing several tons of mixed municipal solid waste a dry.

When considering any type of composting effort, however decision-makers must plan ahead to avoid potential

obstacles that could hinder the operation. The most common challenges are siting the facility ensuring that the

facility is properly designed mitigating and managing oak, controlling bioaerosols and investing adequate

capital to cover unforeseen costs. This manual helps decision-makers understand and prepare for these challanges

so that they can develop a successful composting program in their community

In 1990, Americans generated over 195 million tons of disposal costs avoided through composting and reduced

municipal solid waste (MSW). The amount of waste gen- expenditures on soil amendments for municipal parks and

erated annually in this country has more than doubled in

the past 30 years (EPA, 1992). While MSW generation

rates have increased, however, the capacity to handle these

materials has declined in many areas of the country. Many

landfills have closed because they are full. Others are

choosing to shut down rather than meet stringent new

regulations governing their design and operation. In addition, new landfills and combustors are increasingly difficult to site. In conjunction with this growing gap in

disposal capacity, tipping fees at solid waste management

facilities are rising in many communities, and the trend

does not appear to be changing. As communities search

for safe and effective ways to manage MSW, composting

is becoming a more attractive management option.

In some communities, composting has proven to be more

economical than landfilling, combustion, or constructing

new landfills or combustors, especially when considering

lawns. In addition, composting can help communities

meet goals to recycle and divert substantial portions of the

MSW stream from disposal. Many states are now setting

ambitious recycling goals for their jurisdictions. Because

composting can potentially handle up to 30 to 60 percent

of a community’s MSW stream (EPA, 1993), it can play a

key role in helping communities meet these goals. Finally,

as a type of recycling, composting in many ways represents a more efficient and a safer use of resources than

landfilling or combustion.

Composting as a Component of

Integrated Solid Waste Management

EPA encourages communities to use a mix of management techniques (an approach called integrated solid

waste management) to handle their MSW stream since no

1
Each year, a Seattle-area chain of grocery stores called Larry's Markets compost almost 500 tons of fruits, vegetables,food, and flowers that cant be sold andwoulf otherwise be thro

Composting Food Scraps

taxes costs $100 per ton. The difference between composting and landfilling for Larry's is a total saving of approximately $15,000 each year.

cut Larry's disposal costs. Composting a ton of material costs Larry's $67, while running compactors, hauling mterial to local landfills, and paying landfill fees and

of this composting project, Larry's Markets has reduced the amount of materials being landfilled by nearly 40 percent. This project has also significantly

months to complete. Recently, Larry's has begun to buy back this misture for use on company landscaping projects, thereby "closing the recycling loop." As a result

are mixed with soil, yard trimmings, and ither organic materials to make a rich mixture that is sold for use as topsoil. The entire composting process takes 3 to 5

Once a week, Lawson's Disposal, a local hauler, picks up the materials and transports them to Iddings, Inc., a nearby topsoil company, for composting. The materials

organic material is placed in specially marked dumpsters at Larry's five stores. Coffee residuals, called "chaff" are used to control moisture and reduce odors in the dumps

Introduction

single approach can meet the needs of all communities.

EPA suggests a hierarchy of management methods for officials to consider when developing a solid waste management plan. Source reduction is the preferred management

option. Source reduction can be defined as the design,

manufacture, purchase, or use of materials or products

(including packages) to reduce their amount and toxicity

before they enter the MSW stream. Recycling, including

composting is the next preferred management option.

While lower on the hierarchy than source reduction and

recycling combustion (with energy recovery) and landfilling also are options to manage materials that cannot be

reduced, reused, recycled, or composted. Combustion

reduces the amount of nonrecyclable materials that must

be landfilled and offers the benefit of energy recovery.

Landfillng is needed to manage certain types of nonreusable, nonrecyclable materials, as well as the residues generated by composting and combustion.

In any case, consideration of a composting program

should be part of a community’s comprehensive approach

to solid waste management. AS decision-makers evaluate

their options for managing solid waste, many will look to

composting as an attractive and viable option for handling a portion of their MSW stream,

What Is Composting?

Biological decomposition is a natural process that began

with the first plants on earth and has been going on ever

since. As vegetation falls to the ground, it SlOWly decays,

providing minerals and nutrients needed for plants, animals, and microorganisms. Composting is often used

synonymously with biological decomposition. As the term

is used throughout this guidebook, however, composting

refers to the controlled decomposition of organic (or carbon-containing) matter by microorganisms (mainly bacteria and fungi) into a stable humus material that is dark

brown or black and has an earthy smell. The process is

controlled in that it is managed with the aim of accelerating decomposition, optimizing efficiency, and minimizing

any potential environmental or nuisance problems that

could develop.

Composting programs can be designed to handle yard

trimmings (e.g., leaves, grass clippings, brush, and tree

prunings) or the compostable portion of a mixed solid

waste stream (e.g., yard trimmings, food scraps, scrap paper products, and other decomposable organics). These

materials are the feedstock or “find” for the composting

process. Composting programs also have been designed

for sewage biosolids, agricultural residues and livestock

manures, food processing by-products, and forest industry

by-products. Because these materials are not considered

part of the MSW stream, however, they are not discussed

at length in this guidebook. Some facilities compost

MSW with sewage biosolids, which is a form of co-composting. Co-composting is not discussed in detail in this

guidebook.

During the composting process, feedstock is placed in a

pile or windrow (an elongated pile) where decomposition

takes place. The rate of decomposition depends on the

level of technology used as well as on such physical,

chemical, and biological factors as microorganisms, oxygen levels, moisture content, and temperature. Composting works best when these factors are carefully monitored

and controlled.

The end products of a well-run composting process are a

humus-like material, heat, water, and carbon dioxide.

Compost is used primarily as a soil amendment or mulch

by farmers, horticulturists, landscapers, nurseries, public

agencies, and residents to enhance the texture and appearance of soil, increase soil fertility, improve soil structure

and aeration, increase the ability of the soil to retain water

and nutrients and moderate soil temperature, reduce erosion, and suppress weed growth and plant disease. Figures

I-1 and I-2 at the end of this introduction illustrate the

steps involved in composting yard trimmings and MSW.
Introduction

Trimmings MSW in the

United States

Nationwide, nearly 35 million tons of yard trimmings

were generated in 1990, accounting for nearly 18 percent

of the MSW stream (EPA, 1992). About 2,200 facilities

for the composting of yard trimmings were operating in

the United States in 1991 (Goldstein and Glenn, 1992).

Approximately 12 percent or 4.2 million tons of the yard

trimmings generated in 1990 were composted by these facilities (This estimate> however, does not include the

amount of yard trimmings composted through “backyard” composting projects and other individual efforts.)

(EPA, 1993).

In 1990, the United States also generated over 16 million

tons of food scraps, 12 million tons of scrap wood, and 73

million tons of paper waste, which together account for

51 percent of the MSW stream (EPA, 1992). Although

over 28 percent of all paper waste was recycled in 1988, a

negligible amount of this material is currently composted

(EPA, 1992). While composting of MSW has been practiced in other countries for many years, interest and commitment to MSW composting on a large scale is a recent

development. As of 1992,21 full-scale MSW composting

facilities were in operation in the United States (Goldstein

and Steuteville, 1992). Capacities of most of these facilities range from 10 to 500 tons of MSW feedstock per day.

Minnesota leads the way with eight operational facilities;

Florida has three, and Wisconsin maintains two MSW

composting facilities (see Table I-1). Minnesota’s leading

position is due, in part, to available state funds and technical assistance for MSW composting systems (Crawford,

1990). A number of facilities also are in the planning or

construction stages (see Table I-2). Table I-3 provides a

brief comparison of the composting of yard trimmings

and MSW in reference to several operational and program

parameters.

AS these numbers indicate, composting is currently receiving a substantial amount of attention. Among other

factors, this interest is due to regulatory and economic

factors. In recent years, a number of communities and

states have banned yard trimmings from disposal in landfills. As mentioned earlier, some states also have established ambitious landfill diversion goals, along with

financial assistance programs that support alternative

management projects. Several states also have adopted

MSW compost regulations and more states are likely to

follow. Another important legislative development is that

several states currently require state agencies to purchase

and use compost if it is available and if it is equivalent in

quality to other soil amendments (Crawford, 1990).

Another indication of the headway being made in

composting is the increasing number of vendors marketing their composting systems to public offcials, haulers,

and landfill operators (Goldstein and Glenn, 1992). In

addition, many companies that are in the process of

constructing new waste management facilities are planning to incorporate composting into their operations to

reduce the amount of residuals that must be landfilled

(Goldstein and Glenn, 1992). Additionally many communities and commercial establishments are now attempting to compost a larger portion of the MSW stream

in an effort to reuse materials, rather than landfill or combust them. Several municipalities have established pilot or

ongoing programs to collect mixed MSW for composting.

Others are conducting pilot projects for collecting sourceseparated food scraps. In addition, many restaurants and

grocers are composting leftover or unusable food scraps at

their operations.

Introduction Resources

Crawford, S. 1990, Solid waste/sludge composting International perspectives and U.S. opportunities. Proceedings

of the sixth international conference on solid waste management and secondary materials. Philadelphia, PA. December 4-7.

Glenn, J. 1992. The state of garbage in America Part I.

BioCycle. April, 33(4):46-55.

Goldstein, N., and J. Glenn. 1992. Solid waste composting plants face the challenges. BioCycle. November,

33(11):48-52.

Goldstein, N., and R Steuteville. 1992. Solid waste composting in the United States. BioCycle. November,

33(11):44-47.

METRO. 1989. The art of composting A community

recycling handbook. Portland, oregon Metropolitan

Service District.

Taylor, A., and R. Kashmanian. 1989. Yard Waste Composting A Study of Eight Programs. EPA1530-SW-89-

038. Washington, DC: Office of Policy, Planning and

Evaluation and Office of Solid Wrote and Emergency

Response.

U.S. Environmental Protection Agency (EPA). 1992. U.S.

Environmental Protection Agency. Characterization of

Municipal Solid Waste in the United States. EPA/530-R019. Washington, DC: Office of Solid Wrote and Emergency Response.

U.S. Environmental Protection Agency (EPA). 1993. U.S.

Environmental Protection Agency. Markets for compost.

Washington, DC: Office of Solid Waste and Emergency

Response and Office of Policy, Planning and Evaluation.
200

12

100

Introduction

Table 1-1. Summary of operating MSW plants.

Current Amount of Proprietary

Year MSW Composted Technolgy or

Plant Name started (tons/day) System(1) Ownership/Operation

Lakeside, AZ

New Castle, DE

Escambia County, FL

Pembroke Pines, Ft.

Sumter County, FL

Buena vista County, IA

Coffeyville, KS

Mackinac Island, Ml

Fillmore County, MN

Mora, MN (East

Central SWC)

Lake of the woods

County, MN

Bennington County, MN

St Cloud, MN

Swift County, MN

Truman, MN

(Prairieland SWB)

Wright County, MN

Sevierville, TN

Hidalgo County, TX

Ferndale, WA

Columbia County, WI

Portage, WI

1991

1984

1991

1991

1988

1991

1991

1992

1987

1991

1989

1987

1988

1990

1991

1992

1992

1991

1991

1992

1986

10-12 bedminster

Bioconversion

200-225 Fairfield

digesters

200 Buhler

50

4000/yr. Lundell (for

processing)

50

8 (inc. MSW, —

Sludge, manure) (2)

250 Daneco

5

12 Lundell (for

processing)

60 Eweson digester

w/Royer ag. bed

12

55 OTVD

165 Buhler

150 (design) Bedminster

Bioconversion

70

Royer ag. bed

40-45 —

20

Joint Venture

Public/Private

Public/Public

Private/Private

Public/Private

Private/Private

Private/Private

Public/Public

Public/Pubic

Public/Private

Public/Public

Public/Private

Private/Private

Public/Public

Public/Public

Public/Private

Public/Private

Public/Public

Private/Private

Public/Public

Public/Public

(1) This category is limited to compost system vendors and not other proptietary technologies/equipment

in use at these facilities.

(2) Amount for Mackinac island indicates average daily flow due to park population during the summer

months,

Source: Goldstien and Glenn, 1992.

4
ARIZONA 1. Pinetop-Lakeside Operational

Consideration of pilot (Cocomposting)

Consideration of pilot In-Vessel (Seerdrum) (by American Materials Recyc.)

Status System

Windrow

500-800 w/sludge)

In-Vessel/ Enclosed

Enc.aerated windrow

Operatiional

KANSAS

Operational Windrow

LOUISIANA

MAINE

1/month

Tons/Day (Unless noted)

sluge)

Proposal review Pilot planning(1)

(Source sep. organics)

Construction

Landfill)

Introduction

Table 1-2. Nationwide listing of MSW composting facilities.

Facility

Digester (Bedminster) 12-14 (w/6 wet tpd

40(100-150 at full scale ARKANSAS 1. Madison Pilot

CALIFORNIA 1. Chowchilia Planning Windrow (enclosed) (Madera County)

2. San Diego (City) Vendor negotiation A-SP (Daneco)

3. Tulare County Proposal review Windrow or in-vessel

4. Ventura County Proposal review for solid

300,000/year

900-1,000(w/sludge) 3,000 (total Stream) waste management

CONNECTICUT 1. Northeastern Conn. Proposal review Res. Rec. Auth.

(Brooklyn)

DELAWARE 1. Del. Reclamation Project Operational

200

In-vessel (Fairfield) 200-225 (w/150-200 wet (New Castle) tpd sludge)

FLORIDA 1.Cape Coral

2. Charlotte County 3. Escambia County 4. Manatee County

5. Monroe County 6. Palm Beach County

7. Pembroke Pines

8.Sumter County

IOWA 1. Buenvista County

2.Cedar Rapids

3. Council Bluffs 4. Harden County

(w/Butler,Wright counties)

1.Coffeyville

1. Tri-Parrish SWC (St. Martin, Iberia

Lafayette)

1. Bowdoinham

2. Machias

MARYLAND 1. Baltimore

2. Brandywine

3. Salisbury

(wicomico Cty.

vendor negotiation Windrow

Amerrecycle) 200

400 (w/sludge)

200 (400 design) 1,000 (total Stream)

75,600yr. (total Stream)

Proposal review Operational Vendor negotiation Windrow Windrow

(Amerecycle)

(RDF, RDF rejects, mixed paper) Operational

Agitated bed (IPS)

550 (650 design))

50

(Buhler) Windrow (Amerecycle)

Windrow (w/ Lundell

processing line

4,000/yr.

wet/dry separation)

Consideration 75-80 Windrow (w/ Lundell 60

processing line

50

700 (total Stream)

A-SP

2,500 pop. (Source sep. Orangnics

In-vessel (A-S-H) (2) (FERST Co.) 520(700 design)

340

20(300 design)

2.Brandywine Enc. A-SP (Rader Co.)

5
Nantucket Northampton Northfield

100

Digester w/ agitated bed

MISSOURI 1. Springfield

2. Cape May County 3. Ocean County

NEW YORK 1.Camillus Delware County 3. East Hampton 

Pilot (Residential source sep. organics) 2/wk.

Status Facility System

Massachusetts

Michigan

Operational

Operational

Planning 20-40

Operational Windrow

County

Operational

Windrow 

Operational

Operational

Permitting Enc. A-SP (Daneco) 500

400-500

Planning

Consideration Windrow 300

orgnics; sludge

construction) Aerated Windows

sep. organics) 

A-SP

septage

Landfill Corp.) Propsal review

organics)

Tons/Day (Unless noted)

Introduction

Table 1-2. (Continued).

consideration (Market/odor 15 control studies needed) siting(for source sep. In-Vessel 100

Proposal review Enc.-aerated 100 Consideration Proposed by Bennett Tunnel w/enc. windows 200 Construction, Inc. Proposed by ERS 700

Propose by ERS 800(W/180 tpd sludge)

1.Berkshire county (Southern) 2.Franklin county

6. Somersat 7. Wrentham

l. Mackinac Island A-SP 8 (w/sludge, manure)

MINNESOTA 1. Fillmore County A-SP;Enc.windrow(in 12

2. Freeborn/Mower

counties 3. Goodhue 4. Kandiyohi County

5. Lake of the wood

6. Mora (East Central SWC)

7.Pennington County 8.Rice County

Planning(source

Proposed by ERS

80

450

5

Enc,A-SP (Danco) 250

Operational Planning (w/ addtl. Counties) Planning (by Ceres for RDF residuals MSW, other organics) Operational by Recomp)

Windrow

Aeratedwindrow

40(80 tpd disign))

9. Rosemount

l0. St.Cloud 60(l00tpd design)

11. St.Louis County

12. Swift County Aerated Windrow In-vassal (OTVD)

250 12 (5.5 to Composting) 13. Truman (Prairieland 55 (100 design)

Solid Waste Board) 14. Wright County Operational (RDF residuals

from Anola County)

Enc. aerated Windrow

(Buhler)

165

NEW HAMPSHIRE

1. Ashuelot Valley Refuse Disp. Dist.

2. Hooksat

Consideration

Proposed by Aware Corp. Windrow 800

NEW JERSEY

l. Atlantic County Design(Source Sep. In -Vessel (agitated bed) 159 ( w/sludge)

Permitting Enc. A-SP (Daneco) 600 Pilot (source sep. In-Vessel 300 (design) oganics by Ocean Cty.

4. Ocean Township

In-Vessel 50-100 Consideration In-Vessel l00 (desgn} Feasibility study In-Vessel 1l0 (Total stream) (source sep. Organics; MRF under construction) 4. Eastern Rennselaer Vendor negotiation Enc. A-SP(Daneco) 100-150 (w/sludge, County SWMA

5. Madison County

6. Monroe County
NORTH CAROLINA 1.Buncombs County

Enc. aerated windrow

Consideration

Pilot

Counties

A-SP

Tons/Day (unless noted)

Drum w/windrows

Introduction

Table 1-2. (Continued).

7. NewYork City

8. Riverhead

Pilot (Residential source

Permitted by omni Tech Serv. (Procuring waste contracts)

(voter ref.on

11/31/92)

Windrow 4.5-5/wk

Agitated bed (Koch) 250(500 design)

9.South Hampton

Windrow 200(total for pilot) 300-350 (design)

0REGON 1. Portland

PENNSYLVANIA l. Adams County 2 .Blair County

TENNESSEE 1. Sevierville (Sevier) Solid Waste)

1.Big Sandy

Temporarily closed

(vendor negotiation)

600 (design)

Feasibility study Consideration

In-vessel 150 (total stream) 240 (total Stream)

Digester w/aerated 150(w/75 wet tpd Windrows (Bedminster) Sludge)

Operational by

Bedminster (research) facility) Operational Proposal by WPF Corp.

35 w/ sludge (seasonal)

70 (300 design)

3,800wk (total stream) 368,500 cy/yr.

2. Hidalgo County

4.Stephenville

VERMONT 1.Central Vermont SWMD

VIRGlNIA 1.Loudon County

Aerated Windrow

Planning (Source sep. Organics by priv. co.)

125-180

100

WASHINGTON l. Ferndale Operational by Recomp Digester w/agitated

bed (Royer)

WEST VIRGINIA

1. Leestown Pilot (Source sep. Organics)

Static pile, Windrows

WISCONSIN 1.Adams County 2. Burnett & Washburn

3. Columbia County

4. Portage 5. Vilas County

Consideration (wet/dry) Consideration

Operational

Operational Pilot(in planning)

Windrow Windrow & A-SP 20

50

Drum w/enc. curing 40-45w/sludge (80 design) 20 (w/sludge) 30-50 for pilot 20 tpd (total stream)

Source: Goldstein and Glenn, 1992.

7
Seasonal variations in the flow of feedstock waste stream assement that will require planning and resource to complete. 

Planning Yard trimmings composting often require planning for Large-scale MSW composting will require a detailed

I

Introduction

Table 1-3. A brief comparison of yard trimmings and MSW composting.

Parameter Yard Trimmings composting MSW composting

separation Easy to separate yard trimmings feedstock from the rest Feedstock for MSW composting can be separated by

of the MSW stream for collection and composting since residents or at the facility into recyclable, compostable,

yard trimmings are normally gathered by the and/or noncompostable components.

homeowner separately from other materials.

Technology Yard trimmings composting can be done using relativety MSW composting requires mare complex technology

simple technologies. because it processes a mixed feedstock that can include

varied contaminants.

Leachate Control Leachate collection systems might be required, Due to the diversity of materials in MSW feedstock,

particularly for larger facilities and those in areas of Ieachate collection systems ore generally required.

moderate to high rainfall.

Odor Control Yard trimmings compost facilities can often employ MSW composting facilities are likely to require

simple siting, process, and design controls to minimize

Colors.

sophisticated technologies to control odors. More

stringent siting and design measures also are typically

needed.

Regulations yard trimmings composting is not governed by stringent MSW composting is more stringently regulated or

regulations. controlled than yard trimmings composting, and may

require compliance with state or local permitting

procedures.

Product Quality medium- to high-quality compost can be produced Extensive preprocessing is required to achieve mediumusing relatively simple technology and can be easily to high-quality compost that can overcome public

marketed to end users perception problems of impurity and be marketed easily,

Economics A low-technology yard trimmings composting facility Siting, equipment, and permitting costs can add up to a

can be financed with a relatively small capital large initial and ongoing investment for a MSW

investment and low operating casts (mostly labor). composting facility, particularity for a large operation.

8
Operational Plans Facility Ownership/Management Finding Composting Vendors Siting Odor Control

Facility Design Requirements Collection Methods

Public Drop-Off Sites Curbside Collection Bagged Loose

Passive Piles Turned windrows Aerated Sttic Piles Curing/Storage 

Marketing Product Demand End Iser Requirements Pricing Location/Distribution Issues education and Public Relations

Agriculture Landscaping Horticulture

Silviculture Public Agencies Residential Sector

Introduction

Community Involvement

I

Planning

. Goal Setting

I

I

● Land Area Requlrements

I

Processing Methods

sorting

Process Selection

I

Environmental Concerns

. Odor Control

. Leachate Control

. Occupstional Health and Safety

!

Product Quality

● Compost Quality

. product Specifications 4

● Product Testing

Potential End Users I

Figure 1-1. Overview of a yard trimmings composting program.

9
Communtiy Involvement Planning Goal setting Waste Characterization Operational Plans Facility Ownership/Management Finding Composting Vendors

Introduction

Siting Odor Control Land Area Requirements

Facility Design Requirements

Collection Methods

Curbside Collection Source-Separated MSW Commingled MSW

Processing Methods

Sorting

Houehold Hazardous Waste and Noncompostables

Recycables Separation Technologies

Size Reduction Process Selection

Aerated Static Plies In -Vessel Systems

Turneed Windrows Suction System Positive Pressure System Rotating Drum Tank System

Curing/Storage

 Environmental Concerns Odor Control Vector Control Leachate Control Occupatioanl Health and Safety

Production Quality Compost Quality Production Specifications Product Testing

Marketing

Product Demand End User Requirements Pricing Locaton/Distribution Issues Education and Public Relations

Potential End Users

Agriculture Landscaping Horticulture Silviculture Public Agencies

Residential Sector

Figure 1-2. Overview of an MSW composting program.
Chapter One

Planning

C

ommunities that are considering incorporating composting into their solid waste management strategy need

to conduct thorough planning to decide what type of program best fits the needs and characteristics of their

locality Because each community possesses its own set of financial climactic, socio-economic, demographic,

and land use characteristics, there is no formula dictating how to incorporate composting into an integrated waste

management plan; these issues must be decided on a case-by-case basis for each community or region. This chapter describes some of the preliminary steps that a community should take before embarking on any composting

program. Addition planning requirements are addressed throughout the guidebook.

Goal Setting and quantifying the components of the local MSW

An important first step for public officials considering a

stream should be an integral part of preliminary planning

for every program. One way to obtain this information is

composting program is to determine what they want the . . -

to conduct a waste stream characterization study. These

program to achieve. Typical goals of a composting pro- studies range in price from $35,000 to $400,000, dependgram include ing on the type and quality of information needed. A

Reducing the flow of materials into landfiils or

combustors.

Diverting certain types of materials from the MSW

stream.

Complying with state or local regulations or recovery goals.

Providing a practical management option for a single community or a larger region.

Once a community has clearly defined the goals of its program, it will be easier to evaluate available technologies and

determine the role that composting will play in the community’s overall management strategy. In addition to goal-setit is important to evaluate the economic and technical

feasibilty of composting in the context of other waste management techniques, such as landfilling and combustion, to

determine which alternatives are most suitable for the community The costs and benefits of each option as well as relevant political and public opinion considerations can be

evaluated to ascertain which mix of solid waste management

approaches will best serve the community

Waste Characterization

A municipal composting program must be implemented

with a full understanding of the MSW stream. Identifying

co-reprehensive waste characterization study involves analyzing the local MSW stream by separating and sampling

waste. Sampling can take place at the local waste management facility or at a transfer station. If a large-wale MSW

composting facility is being contemplated, a detailed

waste stream characterization study is necessary to ensure

proper design (this would not be necessary in advance of a

large-scale yard trimmings composting program). Publications, including the Solid Wrote Composition Study 1990-

1991: Part 1 published by the Minnesota Pollution

Control Agency, are excellent references for more detailed

information on conducting MSW stream assessments

(this document is cited in the resources list at the end of

this chapter). While a waste stream characterization study

can provide information on the anticipated quantity of

materials generated, it will not necessarily discern the

amount of materials that will actually be collected or

dropped off in the composting program since that will depend on factors such as the percent of homes or facilities

that provide organic material for composting.

Although a comprehensive waste characterization study is

the most accurate way to obtain data on the local MSW

stream, the analysis involved can be very expensive and

time consuming, Therefore, many communities might

simply want to examine state or national MSW generation patterns, using these figures as a basis for determining

local waste flow and characterization. Planners should,

11
Planning

however, take into consideration any local factors that

could influence the composition and amount of their

MSW stream including

Season and climate - In certain parts of the country,

the amount and type of yard trimmings generated

will vary dramatically from season to season and as

the climate changes. For example, an abundance of

leaves are generated in autumn in many localities.

Climate also can affect the composition and

amount of the MSW stream. During warm seasons, for example, the quantity of beverage containers might be expected to rise. During the

December holiday season, municipalies might expect a large amount of gift-wrapping paper or

Christmas trees.

Regional differeces - Communities in Florida, for

example, might discover that palm fronds constitute a large amount of their local MSW stream,

while municipalities along the Maine seacoast must

take into account large amounts of fish scraps generated in their region.

Demographics - Population variations can have a significant impact on the MSW stream. These include

temporary population changes (particularly in popular tourist or seasonal resort areas and college towns);

the average age, income and education of the population, age of neighborhoods; and population densities.

State of the economy - The economic state of an area

also can affect the composition of the MSW

stream. For example, the increase in consumption

that can be associated with good economic times

might be reflected in an increase in packaging and

other goods in the MSW stream.

Locall source reduction and recycling programs - Programs that aim to reduce or divert certain components of the MSW stream from disposal can affect

the amount and type of materials that can be collected for composting.

For more accurate estimates, information from communities with similar demographic characteristics and sources

of discards can be extrapolated to fit the local scene. Local

collection services and facility operators also can be consulted. These individuals might have written records of

the amount and type of discards collected on a yearly or

even a monthly basis.

Operational Plans

An operational plan should be drafted to assist local officials and community members in understanding the

proposed composting program and their roles in that program. An operational plan can be used as the basis for

community discussion about the proposed program and

for developing strong political support and consensus.

The operational plan will be the community’s road map

for implementing and operating a successful composting

program. Therefore, the more detailed the plan, the more

useful it will likely be. The operational plan can be revised

throughout the planning process as necessary to reflect

major changes or alterations.

The operational plan should stipulate the chosen composting technology (e.g., turned windrows, aerated static

piles, in-vessel systems, etc.); the equipment needed; proposed site design; and the pollution, nuisance, and odor

control methods that will be employed. In addition, it

should specify the personnel that will be required to operate the program as well as the type and extent of training

they will require. The plan also should contain procedures

for marketing or otherwise distributing the compost

product.

When developing a plan, it is important to remember that

all of the elements of a composting program (e.g., buying

equipment, siting a facility, marketing the finished product, etc.) are interrelated. For this reason, all elements of a

composting program should be chosen with other elements in mind. For example, composting site design can

be influenced by a variety of factors. Site design might be

influenced by the type of material that the site will process. A site which processes large quantities of a readily putrescible material and has close neighbors can require an

enclosed design. Site design might also be influenced by

compost markets. A site with screening capabilities and

flexible retention time could be needed to meet the demands of end users. In addition, site design might be influenced by long-term considerations. A site with the

potential to expand can be more appropriate for the community that expects its materials stream to grow in volume. As this example makes clear, decision-makers should

accommodate the interrelated nature of the elements of a

composting program throughout the planning process.

Community Involvement

Throughout the planning process, officials should work

closely with collectors, haulers, processors, the recycling

industry, local utilities, private citizens, and others to

develop a safe, efficient, and cost-effective program.

Providing these groups with a forum to express their concerns and ideas about composting will build a sense of

ownership in the project as a whole. In addition, cooperation will enhance the understanding of the concerned

groups about the compromises needed to make the program work; as a result, objections to siting or collection

programs, for example, should be lessened. These groups

also can provide invaluable information on vital aspects of

12
y Type Owner Operator Municipal Municipality Municipality Privatized Private vendor Private vendor

Merchant facility Private vendor Private vendor Contract services Municipality private firm

revenue from tipping fee and service charges. No contract between vendor and municicpality exits, however.

basis of private capital

Municipality carries no financial or opertional risk.

Private vendor designs, finances, constructs, and operates facility on expectation of sufficient

Problems occur with the

tipping fees. The public risk is

tied to the possibility of the

a composting operation (see Chapter 10 for more information on community involvement).

Facility Ownership and

Management

One of the basic decisions that must be addressed in the

early planning stages is composting facility ownership and

management. There are essentially four options for site

ownership and operations, as shown in Table 1-1. These

are municipal facilities, merchant facilities, privatized facilities, and contract services.

The option chosen for ownership and management of the

composting facility will depend on many factors such as

Table 1-1. A comparison of facility ownership options.

Plannin g

feedstock supply land size and location, personnel resources, experience, costs, liability, financing methods,

and political concerns. composting facilities can be

located on municipally or privately owned land, for

example. When a community has available land and resources, it might consider owning and operating the facility itself If the municipality has the land but not the

resources for operation, it could contract out to an independent management firm. Communities might also consider encouraging the development of a privately owned

and operated facility that works on a long-term contract,

with the municipality guaranteeing tipping fees and feedstock. This facility might be owned and operated by a

landfll owner or a refuse hauler that could serve the needs

of all the communities it services. For larger facilities, in

Arrangement Advantages

Municipality Municipality

Municipality has full control of

operations.

and provides its own

equipment.

Vendor works under Iong-term Municipality uses franchises

service agreement with and operating licenses to municipa lity to compost

feedstock. Vendor designs

minimize competition far the

vendor and thereby minimize

and constructs facility an the investment risk for the vendor.

attracted by the predictable

revenue stream created by the

long-term contract.

Long-term contract with Municipality retains significant

community for operation and maintenance of facility. Private service company upon

cord since it can change

company receives tipping fee. Municipality might staff the

expiration of the contract.

site or the private company might bring its own labor

resources.

Disadvantages

Municipality shoulders all

financial and performance

risks associated with starting

and operating the facility. If

facility (e.g.,traffic,odor,etc

the municipality might have to

oddress political issues as well.

Municipality does not have full

control over operations.

High risk to vendor because of

absence of contract

guaranteeing feedstock and. .

vendor failing and leaving the

community with reduced waste management capacity. Also,

community has no input on the

level of service and no control

of costs.

Municipality shoulders funding

of facility.

Source: Gehr and Brawn, 1592.

13
Pilot Program in Seattle, Washington From 1980 until 1989, the City of Seattle, Washington conducted a yard trimmings composting pilot

and curbside collection of yard trimmings (ILSR,1992).

Program consisting of a variety of demonstration project aimed at determing the success of composting as a management option. Demonstration projects 

community education on composting, Christmas tree recycling, and a 3-month "Clean Green" drop-off program for yard trimmings at the city's two

transfer stations. In October 1988, Seattle passed an ordinance requiring residents to separate yard trimmings from recyclables and refuse. Based on the 

of the city's pilot program, today Seattle maintains a thress-pronged composting program: "Clean Green" drop-off centers for yard trimmings, backyard co

I

Planning

particular, municipalities should consider regional approaches to ownership and management. For example,

one town might supply the site with others providing

equipment and staffing. Such approaches offer both large

and small communities advantages in financing, management, marketing and environmental protection. Regional

approaches also can help communities accomplish together what they cannot attain alone.

Composting Vendors

Many communities do not have the technical personnel

and resources to develop and design a composting program and facility. It is not uncommon therefore to solicit this expertise from the private sector through a

Request For Proposals (RFP). The purpose of an RFP is

to encourage the submission of proposals from vendors

that can conduct composting operations for the community. A well thought out and carefully worded RFP

should include the broad operational plan for the community’s composting program. This will give potential

vendors the proper frame of reference for proposal development. In addition, the RFP should encourage the

vendors to develop creative as well as low-cost options

for composting. Finally, the RFP must provide a strong

basis for reviewers to evaluate the different proposals

and choose the vendor that offers the best mix of technical expertise, program design, and cost effectiveness

for the community (Finstein et al., 1989).

Officials should consider hiring outside services to perform meticulous technical and economic analyses of

any RFPs to determine their suitability to the community’s specific solid waste characteristics. Given the

plethora of source reduction, recycling, composting,

and disposal options, many experts recommend the use

of an RFP particularly for more complex composting

operations, in order to identify opportunities to maximize cost effectiveness and ensure the resulting composting operation will meet its goals.

Pilot Programs

Before implementing a full-fledged composting program, many communities first conduct pilot programs

to determine the costs and prospects for success of a

full-scale project. Pilot programs enable communities to

experiment with different components of a program

(such as composting technologies, collection strategies,

and marketing techniques) to ascertain the most effective approaches for the community. Start-up costs for a

pilot program are greater than for an ongoing composting program, however, and should not be used to estimate the start-up costs of a fill-scale or long-term

program.

14

Summary

n order to ensure a successful composting progwm,

communities must plan ahead Thorough planning will enable communities to detect any major

problems with a composting operation that could

jeopardize its success, such as an unacceptable siting

decision, a lack of consistent feedstock, or a shortage

o f demand for the final product. Among the prrliminary planning steps that a community should undertake are setting gosh, conducting a waste stream

characterization study or assessment, devloping in an

operational plan, soliciting the viewpoints of affected

parties, determining site ownership and management, securing a vendor and considering the value of

conducting a pilot program. Official should view

composting as one alternative in their MS W management program and analyze its effectiveness in

comparison with management alternatives including

source reduction, landfilling and combustion.

Chapter One Resources

Finstein, M., P. Strom, F. Miller, and J. Hogan. 1990.

Elements of a request for proposal (RFP) for sludge and

municipal solid waste composting facilities Scientific and

technical aspects. New Brunswick NJ: Rutgers Cooperative Extension, New Jersey Agricultural Experiment

Station.
Plannin g

Gehr, W., and M. Brown. 1992. When privatization O’Leary P., P. Walsh, and A. Razvi. 1990. Composing

makes sense. BioCycle. July, 33(7): 66-69. and the waste management plan. Waste Age. February,

21(2): 112-117.

International City/County Management Association

(ICMA). 1992. Composting Solutions for waste management. Washington, DC: ICMA U.S. Environmental Protection Agency (EPA). 1989. Decision-Maker’s Guide to Solid Waste Management.

Institute for Local Self-Reliance (ILSR). 1992. In-depth EPA1530-SW-89-072. Washington, DC Office of Solid

studies of recycling and composting programs: Designs, Waste and Emergency Response.

costs, results. Volume III.

Minnesota Pollution Control Agency (MPCA). 1992. Walsh, P., A. Razvi, and P.

Solid Waste Composition Study 1990-1991: Part 1. St. successful compost facility.

Paul, MN: Ground Water and Solid Waste Division. 100-106.

O'Leary. 1990. Operating a

Waste Age. January, 21(1):

15
Chapter Two

Basic Composting

Principles

composting relies on a natural process that results from the decomposition of organic matter by microorganisms. Decomposition occurs wherever organic matter is provided with air and moisture; it occurs naturallyon the forest floor and in open field composting, as the term is used in this guidebook, is distinguished

from this kind of natural decomposition in that certain conditions parameters such as temperature and moisture.) are controlled to optimize the decomposition process and to produce final product that is sufficiently stable for storage and application to land without adverse environmental impacts. This chapter provides a brief

introduction to the biology involved in composting It also describes the physical and chemical parameter that influence the process. Chapter 4 of guidebook discusses how to control these parameter to optimize composting.

Overview of the Composting Process

The composting process occurs in two major phases. In

the first stage, microorganisms decompose the composting feedstock into simpler compounds, producing heat as

a result of their metabolic activities. The size of the composting pile is reduced during this stage. In the second

stage, the compost product is “cured” or finished. Microorganisms deplete the supply of readily available nutrients

in the compost, which, in turn, slows their activity. As a

result, heat generation gradually diminishes and the compost becomes dry and crumbly in texture. When the curing stage is complete, the compost is considered

“stabilized” or “mature.” Any further microbial decomposition will occur very slowly.

The Role of Microorganisms

Composting is a succession of microbial activities whereby

the environment created by one group of microorganisms

invites the activity of successor groups. Different types of

microorganisms are therefore active at different times in

the composting pile. Bacteria have the most significant effect on the decomposition process, and are the first to

take hold in the composting pile, processing readily decomposable nutrients (primarily proteins, carbohydrates,

and sugars) faster than any other type of microorganism.

Fungi, which compete with bacteria for food, play an important role later in the process as the pile dries, since

fungi can tolerate low-moisture environments better than

bacteria. Some types of fungi also have lower nitrogen

16

requirements than bacteria and are therefore able to decompose cellulose materials, which bacteria cannot. Because fungi are active in composting piles, concern has

arisen over the growth of opportunistic species, particularly those belonging to the genus Aspergillus. Chapter 6

discusses the potential health risks associated with this

fungus.

Microorganisms also play a role in the composting process. Rotifers, nematodes, mites, springtails, sowbugs, beetles, and earthworms reduce the size of the composting

feedstock by foraging, moving in the compost pile, or

chewing the composting materials. These actions physically break down the materials, creating greater surface

area and sites for microbial action to occur.

The microorganisms necessary for composting are naturally present in most organic materials, including leaves,

grass clippings, and other yard trimmings, and other organic materials. Products are available that claim to speed

the composting process through the introduction of selected strains of bacteria, but tests have shown that inoculating compost piles in this manner is not necessary for

effective composting of typical yard trimmings or MSW

feedstock (Rynk et al., 1992; Haug, 1980; Gray et al.,

1971a).

The bacteria and fungi important in decomposing the

feedstock material can be classified as mesophilic or

thermophilic. Mesophilic microorganisms or mesophiles (those that grow best at temperatures between 25

and 45°C [77 to 113oF]) are dominant throughout the
Process

Basic composting Principles

Figure 2-1. Temperature and pH variation with time phases of microbial activity.

A = mesophilic, B = thermophilic, C = cooling, D = maturing.

composting mass in the initial phases of the process when

temperatures are relatively low. These organisms use available oxygen to transform carbon from the composting

feedstock to obtain energy, and, in so doing, produce

carbon dioxide (C02) and water. Heat also is generated

as the microorganisms metabolize the composting feedstock. As long as the compost pile is of sufficient size to

insulate internal layers from ambient temperatures and

no artificial aeration or turning occurs, most of the heat

generated by the microorganisms will be trapped inside

the pile. In the insulated center layers, temperatures of

the composting mass will eventually rise above the tolerance levels of the mesophilic organisms. Figure 2-1

shows a typical temperature pattern for natural composting processes. When the temperatures reach toward

45°C (113oF), mesophiles die or become dormant,

waiting for conditions to reverse.

At this time, thermophilic microorganisms or thermophiles (those that prefer temperatures between 45 and

70oC [113 and 158°F]) become active, consuming the materials readily available to them, multiplying rapidly,

and replacing the mesophiles in most sections of the composting pile. Thermophiles generate even greater quantities of heat than mesophiles, and the temperatures reached

during this time

and weed seeds.

are hot enough to

Many composting

kill most pathogens

facilities maintain a

temperature of 55°C (131°F) in the interior of the compost pile for 72 hours to ensure pathogen destruction and

to render weeds inviable. (See Chapter 6 for a detailed discussion of pathogens and Chapter 7 for a discussion of

different states’ requirements for ensuring pathogen and

weed destruction.)

The thermophiles continue decomposing the feedstock

materials as long as nutrient and energy sources are

plentiful. As these sources become depleted, however,

thermophiles die and the temperature of the pile drops.

Mesophiles then dominate the decomposition process

once again until all readily available energy sources are

utilized. Table 2-1 shows the density of microorganisms as

a function of temperature during composting.

Factors Influencing the Composting

Because microorganisms are essential to composting, environmental conditions that maximize microbial activity

will maximize the rate of composting. Microbial activity is

influenced by oxygen levels, particle sizes of the feedstock

material, nutrient levels and balance (indicated by the

carbon-to-nitrogen ratio), moisture content, temperature,

and acidity/alkalinity (pH). Any changes in these factors

are interdependent; a change in one parameter can often

17
Bacteria Mesophilic Thermophilic

Care

Basic Composting Principles

1

result in changes in others. These factors and their interrelationships are discussed briefly below and in more detail

in Chapter 4.

Oxygen

Composting can occur under aerobic (requires free oxygen) or anaerobic (without free oxygen) conditions, but

aerobic composting is much faster (10 to 20 times faster)

than anaerobic composting. Anaerobic composting also

tends to generate more odors because gases such as hydrogen sulfide and amines are produced. Methane also is produced in the absence of oxygen.

Microorganisms important to the composting process require oxygen to break down the organic compounds in

the composting feedstock. Without sufficient oxygen,

these microorganisms will diminish, and anaerobic

microorganisms will take their place. This occurs when

the oxygen concentration in the air within the pile falls

below 5 to 15 percent (ambient air contains 21 percent

oxygen). To support aerobic microbial activity, void spaces

must be present in the composting material. These voids

need to be filled with air. Oxygen can be provided by mixing or turning the pile, or by using forced aeration systems (Chapter 4 discusses mixing and aeration methods

in more detail).

The amount of oygen that needs to be supplied during

composting depends on:

n The stage of the process - Oxygen generally needs to

be supplied in the initial stages of composting; it

usually does not need to be provided during curing.

n The type of feedstock - Dense, nitrogen-rich materials (e.g., grass clippings) will require more oxygen.

Table 2-1. Microbial populations during aerobic compacting.a

The particle size of the feedstock - Feedstock materials of small particle size (e.g., less than 1 or 2 inches

in diameter) will compact, reducing void spaces

and inhibiting the movement of oxygen. For this

reason, the feedstock should not be shredded too

small before processing (see below and Chapter 4

for information on size reduction).

The moisture content of the feedstock - Materials with

high moisture content (e.g., food scraps, garden

trimmings) will require more oxygen.

must be taken. however. not to provide too much

aeration, which can dry out the pile and impede

composting.

Particle Size

The particle size of the feedstock affects the composting

process. The size of feedstock materials entering the composting process can vary significantly. In general, the

smaller the shreds of composting feedstock, the higher the

composting rate. Smaller feedstock materials have greater

surface areas in comparison to their volumes. This means

that more of the particle surface is exposed to direct microbial action and decomposition in the initial stages of

composting. Smaller particles within the composting pile

also result in a more homogeneous mixture and improve

insulation (Gray et al., 197 lb). Increased insulation capacity helps maintain optimum temperatures in the composting pile. At the same time, however, the particles

should not be so small as to compact too much, thus excluding oxygen from the void spaces, as discussed above.

(Chapter 4 describes techniques for size reducing composting feedstock prior to processing.)

Number per Wet Gram of Compost

Mesophilic Initial Thermophilic Mesophilic Numbers of

Microbe Temp (40oC) (40-70°c) (70°C to Cooler) Species Identified

Actinomycetes

Thermophilic 1 0

4

108 105

14

aComposting substrate not stated but thought to be garden-type meterials composted with little mechanical agitation.

bActual number present is equal to or less than the stated value.

Source: Haug, 1980.

18
Basic Composting Principles

Nutrient Levels and Balance

For composting to proceed efficiently, microorganisms require specific nutrients in an available form, adequate

concentration, and proper ratio. The essential macronutrients needed by microorganisms in relatively large amounts

include carbon (C), nitrogen (N), phosphorus (P), and

potassium (K). Microorganisms require C as an energy

source. They also need C and N to synthesize proteins,

build cells, and reproduce. P and K are also essential for

cell reproduction and metabolism. In a composting system, either C or N is usually the limiting factor for efficient decomposition (Richard, 1992a).

Composting organisms also need micronutrients, or trace

elements, in minute amounts to foster the proper assimilation of all nutrients. The primary micronutrients needed

include boron, calcium, chloride, cobalt, copper, iron,

magnesium, manganese, molybdenum, selenium, sodium,

and zinc (Boyd, 1984). While these nutrients are essential

to life, micronutrients present in greater than minute

amounts can be toxic to composting microorganisms.

Even if these nutrients are present in sufficient amounts,

their chemical form might make them unavailable to

some or all microorganisms. The abilty to use the available organic compounds present depends on the microorganism’s “enzymatic machinery” (Boyd, 1984). Some

microorganisms cannot use certain forms of nutrients because they are unable to process them. Large molecules,

especially those with different types of bonds, cannot be

easily broken down by most microorganisms, and this

slows the decomposition process significantly. As a result,

some types of feedstock break down more slowly than

others, regardless of composting conditions (Gray et al.,

1971a). For example, lignin (found in wood) or chitin

(present in shellfish exoskeletons) are very large, complex

molecules and are not readily available to microorganisms

as food. These materials therefore decompose slowly.

The C:N ratio is a common indicator of the availability of

compounds for microbial use. The measure is related to

the proportion of carbon and nitrogen in the microorganisms themselves. (Chapter 4 discusses the C and N content of different types of feedstock.)

High C:N ratios (i.e., high C and low N levels) inhibit the

growth of microorganisms that degrade compost feedstock. Low C:N ratios (i.e., low C and high N levels)

initially accelerate microbial growth and decomposition.

With this acceleration, however, available oxygen is

rapidly depleted and anaerobic, foul-smelling conditions

result if the pile is not aerated properly. The excess N is released as ammonia gas. Extreme amounts of N in a composting mass can form enough ammonia to be toxic to

the microbial population, futher inhibiting the composting process (Gray et al., 1971b; Haug, 1980). Excess N

can also be lost in leachate, in either nitrate, ammonia, or

organic forms (Richard, 1992b) (see Chapter 6).

Moisture

The moisture content of a composting pile is interconnected with many other composting parameters, including moisture content of the feedstock (see Chapter 4),

microbial activity within the pile, oxygen levels, and temperature. Microorganisms require moisture to assimilate

nutrients, metabolize new cells, and reproduce. They also

produce water as part of the decomposition process. If

water is accumulated faster than it is eliminated via either

aeration or evaporation (driven by high temperatures),

then oxygen flow is impeded and anaerobic conditions result (Gray et al., 1971 b). This usually occurs at a moisture

level of about 65 percent (Rynk et al., 1992).

Water is the key ingredient that transports substances

within the composting mass and makes the nutrients

physically and chemically accessible to the microbes. If

the moisture level drops below about 40 to 45 percent,

the nutrients are no longer in an aqueous medium and

easily available to the microorganisms. Their microbial activity decreases and the composting process slows. Below

20 percent moisture, very little microbial activity occurs

(Haug, 1980).

Temperature

Temperature is a critical factor in determining the rate of

decomposition that takes place in a composting pile.

composting temperatures largely depend on how the heat

generated by the microorganisms is offset by the heat lost

through controlled aeration, surface cooling, and moisture

losses (Richard, 1992a) (see Chapter 4). The most effective composting temperatures are between 45 and 59°C

(113 and 138°F) (Richard, 1992a). If temperatures are

less than 200C (68°F), the microbes do not proliferate and

decomposition S1OWS. If temperatures are greater than

59°C (138°F), some microorganisms are inhibited or

killed, and the reduced diversity of organisms results in

lower rates of decomposition (Finstein et al., 1986; Strom,

1985).

Microorganisms tend to decompose materials most efficiently at the higher ends of their tolerated temperature

ranges. The rate of microbial decomposition therefore increases as temperatures rise until an absolute upper limit is

reached. As a result, the most effective compost managing

plan is to maintain temperatures at the highest level possible without inhibiting the rate of microbial decomposition (Richard, 1992a; Rynk et al., 1992).

Acidity/Alkalinity (pH)

The pH of a substance is a measure of its acidity or alkalinity (a function of the hydrogen ion concentration), described by a number ranging from 1 to 14. A pH of 7

indicates a neutral substance, whereas a substance with

pH level below 7 is considered to be acidic, and a substance with a pH higher than 7 is alkaline. Bacteria prefer

19
NY.

Basic composting Principles

a pH between 6 and 7.5. Fungi thrive in a wider range of

pH levels than bacteria, in general preferring a pH between 5.5 and 8 (Boyd, 1984). If the pH drops below 6,

microorganisms, especially bacteria, die off and decomposition slows (Wiley, 1956). If the pH reaches 9, nitrogen is

converted to ammonia and becomes unavailable to organisms (Rynk et al., 1992). This too slows the decomposition process.

Like temperature, pH levels tend to follow a successional

pattern through the composting process. Figure 2-1, on

page 17, shows the progression of pH over time in a composting pile. As is illustrated, most decomposition takes

place between pH 5.5 and 9 (Rynk et al., 1992; Gray et

al., 197 lb). During the start of the composting process,

organic acids typically are formed and the composting

materials usually become acidic with a pH of about 5. At

this point, the acid-tolerating fungi play a significant role

in decomposition. Microorganisms soon break down the

acids, however, and the pH levels gradually rise to a more

neutral range, or even as high as 8.5. The role of bacteria

in composting increases in predominance again as pH

levels rise. If the pH does not rise, this could be an

indication that the compost product is not fully matured

or cured.

Summary

c

omposting is a biological process influenced by a

variety of environment factors, including the

number and species of microorganisms present . .

oxygen levels,particle size of the composting materials

als nutrient levels, moisture content, temperature,

and pH. All of these factor are interrelated, and

must be monitored and controlled throughout the

composting process to ensure a quality product.

Chapter Two Resources

Alexander, M. 1961. Introduction to soil microbiology.

New York, NY: Wiley Publishing Co. As cited in: Gray,

K.R., K. Sherman, and A.J. Biddlestone, 1971b. A review

of composting Part 2- The practical process. Process Biochemistry. 6(10):22-28.

Boyd, RF. 1984. General microbiology. Wirtz, VA: Time

Mirror/Mosby College Publishing.

Finstein, M. S., F.C. Miller, and P.F. Strom. 1986. Waste

treatment composting as a controlled system. As cited in:

H.J. Rehm and G. Reed, eds.; W. Schonborn, vol. ed.

Biotechnology A comprehensive treatise in 8 volumes

Volume 8, microbial degradations. Weiheim, Germany

Verlagsangabe Ver. Chemie (VCH).

Golueke, C.G. 1977. Biological reclamation of solid

wastes. Emmaus, PA: Rodale Press.

Gray K.R., K. Sherman, and A.J. Biddlestone. 1971a. A

review of composting Part 1- Process Biochemistry.

6(6):32-36.

Gray, K. R., K Sherman, and A.J. Biddlestone. 1971b. A

review of composting Part 2- The practical process. Process Biochemistry. 6(10):22-28.

Haug, R.T. 1980. Compost engineering principles and

practice. Ann Arbor, MI: Ann Arbor Science publishers,

Inc.

Massachusetts Department of Environmental Protection

(MA DEP). 1991. Leaf and yard waste composting guidance document. Boston, MA: MA DEP, Division of Solid

Waste Management.

May, J. H., and T.W. Simpson. Virginia Polytechnic Institute and State University. 1990. The Virginia yard waste

management manual. Richmond, VA: Virginia Department of Wrote Management.

McGaughy, P.H., and H.G. Gotaas. Stabilization of municipal refuse by composting. American Society of Civil

Engineers. Paper No. 2767. As cited in Haug, 1980.

Compost engineering principles and practice. Ann Arbor,

MI: Ann Arbor Science Publishers, Inc.

Poincelot, R.P. 1977. The biochemistry of composting. As

cited in: composting of Municipal Residues and Sludges:

Proceedings of the 1977 National Conference. Rockville,

MD: Information Transfer.

Richard, T.L. 1992a. Municipal solid waste composting

Physical and biological processing. Biomass & Bioenergy.

Tarrytown, NY: Pergamon Press. 3(3-4):163-180.

Richard, T.L. 1992b. Personal communication. College of

Agriculture and Life Sciences. Cornell University. Ithaca,

Rynk, R, et al. 1992. On-farm composting handbook.

Ithaca, NY: Cooperative Extension, Northeast Regional

Agricultural Engineering Service.

Strom, P.F. 1985. Effect of temperature on bacterial species

diversity in thermophilic solid waste composting. Applied

Environmental Microbiology 50(4): 899-905. As cited in

Richard, 1992a. Municipal solid waste composting Physical and biological processing. Biomass & Bioenergy. Tarrytown, NY: Pergamon Press. 3(34):163-180.

Wiley, J.S. 1956. Proceedings of the 1lth industrial waste

conference. Purdue University, series 91, p. 334.

20
Chapter Three

Collection Methods

T

he cost, ease, and effectiveness of implenenting a composting program is affected by the method chosen for

collecting the compost feedstock. Communities can select from a variety of collection systems to develop a

composting progam to meet their specific needs. Programs can be designed to collect just yard trimmings, or

yard trimming and MSW. Collection can occur at curbside, where the municipality picks up the materials directly from household or through drop-off sites, where residents and commercial producers deliver their compostable material to a designated site. Most communities will want to build on their existing refuse collection

infrastructure when implementing a composting program. This will ease the implementation of composting into a

community overall MS W management program and help contain costs. This chapter describes the advantages

and disadvantages of various collection methods and examines some of the factors that decision-makers should

consider when examining the applicability of different systems. Because collection is very different depending on

whether yard trimming, MSW or both am being collected this chapter is divided two babes. The first portion of

the chapter discusses yard trimmings collection; the second section focuses on source-separated and commingled MSW

Collections.

Factors in Yard Trimmings Collection tent of grass can, however, cause odor problems during

the composting process if not balanced with sufficient carWhen developing a yard trimmings collection program,

officials must take into account the length of the growing

season, which affects both the amount of feedstock to be

collected as well as the duration of collection. In the more

temperate climates of the southern and southwestern regions of the United States, collection can take place

throughout the year. In other areas of the United States,

collecting yard trimmings is largely a seasonal matter.

Grass can be collected from spring through fall (the average growing season is 24 to 30 weeks). Leaves usually can

be collected from mid-October through December and

once again in the spring. Brush typically is collected in

spring and fall. Depending on the season and the region,

the brush, grass, and leaves can be collected together or

separately. Ideally, brush should not be mixed with grass

cuttings and leaves during collection without first being

processed into smaller pieces because large branches tend

to decompose more slowly. Because large volumes of

leaves are generated within a relatively short time span,

many communities find it cost-effective to collect and

compost them separately from other yard trimmings.

Leaves can be composted with other materials, usually

grass, whose high nitrogen content can accelerate the

composting process and result in a higher quality finished

product (see Chapters 2 and 4). The high nitrogen conbonaceous material and managed properly (see Chapters 4

and 6 for more information).

There are two basic options for collecting yard trimmings:

public drop-off sites and curbside collection. When establishing a collection program, community leaders must

consider the program’s convenience for the public, as well

as the level of interest displayed by citizens participating

in the program. A drop-off program in a small, denselypopulated community with residents well-educated about

the importance of composting might garner high participation rates. By contrast, in a community that is uninterested or uneducated about composting, even a curbside

program-which is typically more convenient for community residents-might fail to bring in large amounts of

yard trimmings. Drop-off and curbside collection methods are described below.

Public Drop-Off Sites for Yard Trimmings

Public drop-off sites are specified locations where residents

and businesses can take their yard trimmings. Drop-off sites

can be an effective, low-cost option for some municipalities

since they allow communities to operate a composting program while avoiding the labor and capital investment costs

associated with curbside collection operations.

21
Home Composting and "Don't Bag It" Programs

be composted as well.

Collection Methods

R

esidents can be encouraged to let grass clippings

remain on the lawn. The clippings will decompose

and add nutrients to the soil. This eliminates the

need to bag and remove the cuttings. Although exact

recommendations depend on the variety of grass, it is

generally advisable to not cut more than one-third of

the blade, and not more than 1 inch total at any time.

Leaves also can be mulched with a lawn mower into

the Iawn if cut finely enough.

Home composting of yard trimnings also serves to divert material from being collected and recovered or disposed of, Additionally, residents are provided with

compost for gardening and landscaping. Home composting is particularly appropriate for residential lots of

one-half acre or larger. Many types of food scraps can

To encourage individual to leave clippings on the

lawn, perform mulching, or compost at home, municipalities must educate residents about the “whys” and

“hews” of these procedures. Many towns and cities,

states, anti university extension service across the

country have published local guides and brochures on

how to mulch and compost. Also, incentives such as

providing simple compost bins at no cost ear encourage residential composting.

Drop-off stations can be located at established recycling

centers, landfills, and transfer stations or at the composting facility itself In addition, some localities employ a system of collection trailers, which can travel to different

locations in the community for added convenience to area

residents. In all cases, yard trimmings should be collected

frequently from drop-off centers to prevent the formation

of odors and attraction of vectors (see Chapters 4 and 6).

Drop-off collections typically have low participation rates

primarily because residents must assume the responsibility

for collection (Richard et al., 1990). In communities

where citizens are accustomed to delivering their household waste to landfills or transfer stations, drop-off collections of yard trimmings are more likely to succeed.

Drop-off programs in communities with curbside collection of MSW however, could witness lower collection

rates at first due to residents’ lack of familiarity with this

collection method. To encourage participation, communities should strive to make the collection as convenient as

possible. some programs, for example, allow participants to

pick up finished compost, firewood or d chips on the

same day they drop off compostable materials. In addition,

the public should be informed of the specifics of the

community’s collection program, as well as the rationale

for and benefits of composting (see Chapter 10 for more

information on community involvement).

In addition to residents, other sectors of the community

can be encouraged to participate in yard trimmings dropoff programs. For example, businesses that generate a substantial amount of yard trimmings (such as landscape

contractors) might be allowed to drop off the material. In

areas where tipping fees are charged for municipal solid

waste disposal, businesses might be offered a recked fee

as an incentive for bringing in yard trimmings for composting. This would mean, however, that incoming shipments would need to be measured. To eliminate the need

for measuring shipments on site, communities could calculate the average amount of yard trimmings per truckload (based on tons or pounds per cubic yard) for each

business and draft permits for a limited number of dropoffs based on these calculations. Figure 3-1 presents a

sample yard trimmings drop-off permit.

Curbside Collection of Yard Trimmings

In a curbside collection program, the municipality picks

up the yard trimmings that residents have placed outside

of their homes. Curbside collection of yard trimmings

typically offers the advantage of higher participation rates

than drop-off programs. Overall, curbside collection is

more expensive than drop-off colleetion due to the added

equipment and labor resources needed. Nevertheless, additional costs are frequently justified by the volume of

yard trimmings that is diverted and recovered.

The frequency of pickup will depend on such factors as

the type and amount of yard trimmings being collected,

the size and makeup of the community, and the budget.

Schedules for curbside collection can range from weekly

collections for grass in the summer to a single annual collection for brush.

Communities also must decide which collection method

to employ for curbside yard trimmings collection. The

material either can be collected in a container set out by

the household or collected loose with the aid of a front

loader or other equipment (see Appendix B). Several programs, such as those in Columbia, South Carolina, and

Sacramento, California, have been collecting loose yard

trimmings since the 1950s or earlier (Glenn, 1989). Collection of containerized yard trimmings, on the other

hand, is relatively new. The advantages and disadvantages

of both collection strategies arc examined below.

Loose Yard Trimmings

Picking up loose yard trimmings at the curbside, a practice known as bulk collection, is most frequently used for

collecting leaves during fall when communities generate

large volumes of this material. Bulk collection avoids the

cost of providing bags or special containers to residents

22
NO CASH WILL BE ACCEPTED

Collection Methods

Permit # Mo. Day Yr. Disposal Amount Quantity Unused

Quantity Paid (S) used Cu. Yd.

Purchased (Cu. Yd.

Last Name First Cu. Yd.

Name

Street P.O. Box

city Zip Phone

(x) one)

( ) 1.individual residence 5. commercial property

2.commericial ( ) 6. public Utility

( ) 3. tree surgeon ( ) 7. local goverment

 4. school/college ( ) 8. other goverment unit

( ) 9. other (specify)

—Leaf Disposal Information for Commcercia Haulers l -

❵ There will be a petmit fee of $ per each vehicle for dumping at this site. The permit

will be affixed on the inside of the windows of the driver's side, and be in plan view upon

entering the composting site.

Permits may be obtain at the compost site or city hall, Monday through Friday from

9:00AM to ll:00)AMody. Payment shall be a certified check or money order made out

the Town of .

the hours of operation will be Monday through Friday from 7:00AM to 5 PM beginning

. There will be no dumping on Veteran’s Day and Thanksgiving Day. Dumping will terminate on . or sooner, at the discretion

of the public works Superintendent if the yard becomes full.

Haulers depositing yard waste will enter and exit from

The DPW requests the cooperation of all permit holders and reminds everyone that no plastic

bags or any other foreign are to be included with the yard waste. Failure to follow

any of the above mentioned, or the instructions of the site attendant, may result in the foreiture of one’s permit.

Permits are granted as an exclusive right of the DWP and are to be used only at the compost

site. Said permits are non-transferrable and may be revoked for just cause at any time.

Source: Richard et al., 1990.

Figure 3-1. Yard trimmings drop-off permit application farm from New York State.

23
I

Collection Methods

(or requiring residents to purchase these items). In addition, bulk collection facilitates the unloading of material

at the facility since no debagging is necessary.

Bulk collections are a long labor-intensive process, however, and could require the community to purchase new

Collection Strategies in Two

Massachusetts Towns

Melrose, Massachusetts, opened a leaf composting Facility in October 1990 in response to a state landliil

ban on leaves and other yard trimmings. To cover

costs, the Boston suburb invited other regional communities to send leaves to the facility for a moderate

tipping fee with one stipulation-that the leaves be delivered loose or in biodegradable paper bags.

several towns and cities its the area responded immediately, including Stoneham and Burlington. Stoneham

officials decided to collect leaves at the curbside

throughout the entire town on two Saturdays at the

beginning of November and December, respectively.

Six biodegradable paper bags would be provided at no

cost to each household, with extra bags available at the

Stoneham Department of Public Works are the cost of

three for $1. Stoneham also established a 40-cubicyard container at the Department of Public Works

where residents could drop off leaves from October 1

through December 15, 1990. Because of Stoneham’s

compact size-no household was located more than 5

minutes from the drop-off site—the combination of

limited curbside collection and a drop-off container

worked to capture about 60 percent of the estimated

leaf stream available.

Burlington officials, on the other hand, decided against

a drop-off center in favor of more frequent curbside

collections, This was due primarily to the more dis

persed population of the town. (A central drop-off location would make it inconvenient for some

households to drive the 20 minutes necessary to deposit their leaves.) Burlington officials contracted with

the town collector to pickup all available leaves for 6

weeks in the fall and 3 weeks in the spring each year.

The paper bags were distributed through the town’s

public work department. Like their neighbors in

Stoneham, Burlington residents recovered about 60

percent of&e Ieaves that normally went to the landfill

in the first year of the program. Both Stoneham and

Burlington officials carefully examined the factors that

could influence the outcome of their collection programs. In each case, they tailored the programs to the

conditions in their respective towns to recover a majority of the leaves.

equipment. AS a result, the community might be able to

afford only a reduced pickup schedule. Many different

types of equipment are used to pick up unbagged leaves

mechanically. Vacuum trucks are commonly used to collect piles of leaves. These trucks often can mix leaves with

glass, sand, and other undesirable substances found on the

road, however, and are not effective when the leaves become wet or frozen (See Appendix B for more information). Front-end loaders can be used under these

conditions but are not effective with dry leaves. Specialized vehicles, such as tractors equipped with a claw or leafloaders that quickly sweep material from the curb to the

transportation truck, are becoming available for bulk collections of yard trimmings. (See Appendix B for descriptions and costs for specialized equipment.)

Communities must consider several potential problems

inherent in bulk leaf collections. First, loose leaves are susceptible to being mixed with unwanted objects such as

glass, cans, and ear batteries (Richard et al., 1990). The

leaves also become difficult to collect after they have

blown around or children have played in them. In addition, loose leaves can catch fire from hot automobile exhaust systems.

Bulk collection of unbagged brush and grass clippings is

problematic. Piles of grass left on the sidewalk are very

difficult to collect, and in most communities this option is not cost-effective. Brush collections require special handling. Because brush does not readily compact,

mobile wood chippers might be needed to reduce the

volume of brush, thereby facilitating collection and cutting down on handling and transportation costs. Alternatively, brush can be collected in bundles and taken to

a central processing facility for chipping. While brush is

produced year round, it is impractical to have a yearround collection program because of the relatively small

amount of material involved. Many communities have

organized monthly or annual brush collection days

(Mielke et al., 1989).

Bagged or Containerized Yard Trimmings

Collecting bagged or containerized yard trimmings at the

curbside is typically a neater and more efficient operation

than collecting in bulk. Moving the materials to the transportation vehicle is relatively quick and the bags or containers are not affected seriously by weather conditions.

Communities generally can use a standard compactor

truck for collection. Furthermore, existing programs have

found that bagged yard trimmings typically contain less

noncompostable material than unbagged yard trimmings.

Several types of containers can be used for collection.

Common containers include plastic and degradable plastic bags, paper bags, and specialized marked trash containers. Table 3-1 lists the major advantages and disadvantages

of each type of bag and bin. Another alternative the

24
Plastic Bags $0.12/bag

Paper Bags $0.25- 0.45/bags

If paper bags gettorn or crushed early in the composting process, uch as in the compactor truck, the composting process is enhanced because paper bags are degradable.

Degradability is uncertain. Some studies

have shown that these bags

Can off additional holding strength over lightweight plastic bags. Can be more expensive than plastic bags.

Bins are large enough to be practical yet

prohibitive expenditure for some

form the bin and transported unbagged.

Collection Methods

Table 3-1. A comparison of yard trimmings collection containers.

Type of Container Cost Advantages Disadvantages

"Biodegradable” $0.20/bag Plastic Bags

Rigid plastic Bins $50-60/bin

Inexpensive and readily available. Can be torn open, scattering materials; also

true for for other types of bags, Require an

Reduce the amount of time collection vehicles extra debagging step because plastic con

spend on routes because the yard trimming clog he tines on the turning eqipment and separated and easily handled by were out grinding blades in other machines. workers; a so true for other types of bogs.

plastic does not decompose and is Materials in bags are less likely to contain considered undesirable in the compost.

unwanted materials since they are not

exposed; also true far other types of bags, As grass clippings decompose in plastic

bags, they will became anaerobic and

therefore malodorous. Workers and nearby

residents might find these odors

unacceptable when these bogs are opened

at the composting site.

Supposed to degrade by microbial action or

in the presence of sunlight, eventually

becoming port of the compost.

 can take several

years to fully degrade, so its of plastic still will be visibl e when the compost is finished.

These contaminants can reduce the

marketability of finished compost.

small enough to be handled by the collection

The initial costs of the bins might represent a

crews and residents without undue strain. cummities, however. Fees are

Bins range in size from small, basket-sized to frequently passed on to homeowners to pay

30- and 90-gallon well-marked containers. far the start-up cask.

Bins allow for neat storage of yard trimmings Might require extra collection time to empty while awaiting collection. bins and collect materials.

The time that yard trimmings spend in

anaerobic conditions is often minimized

(depending on how long the material is in

the bin) since the yard trimmings are emptied

This, is turn reduces the potential for odor

problems.

Source Wagner, 1991.

community can choose is to require residents to separate

yard trimmings into color-coded or otherwise marked

bags that can be sorted easily at the processing facility.

Some communities provide bags at no cost to residents

and cover the cost as part of their solid waste management budget. Others sell bags to the residents at full

price or at a discount. If bags are sold to residents, incentives to purchase the bags and participate in the program must be provided to discourage individuals from

mixing their yard trimmings with refuse. In areas of the

country that charge for general refuse collection by the

barrel and maintain a bagged yard trimmings collection

program, residents might be tempted to conceal noncompostable materials in composting bags as a way to decrease

their own disposal costs. To minimize this problem, transparent plastic bags can be used. This strategy is being

employed by a number of communities, including

Brookline, Massachusetts. These bags allow sanitation

workers to easily identify the contents of the bag, as

well as any undesirable objects that might be readily

visible. Town ordinances prohibiting the mixing of yard

trimmings with refuse also might be considered. Figure

3-2 provides an example of a town ordinance.

25
Collection Methods

AN ORDINANCE.

AMENDING TITLE 7, CHAPTER 7.16 OF THE REVISED ORDINANCES OF THE

CITY OF SPRINGFIELD, 1986, AS AMENDED

Be it ordained by the City Council of the City of Springfield, as follows:

Title 7, Chapter 7.16 of the Revised. Ordinaces. of the City of

Springfield, 1986, as amended, is hereby further amended by inserting the

following new section 7.16.041 Mandatory Yard and Leaf Waste Composting.

7.16.041 ManndatoryLeaf and Yard Waste Composting

A. There is hereby established a program for the mandatory separation

of certain compostable leaf and yard waste material from garbage or rubbish

by the residents of the City of Springfield and the collection of these

compostable leaf and yard waste materials at the residents” curbside. The

collection of separated compostable leaf and yard waste material shall be

made periodically under the supervision of the Director of Public Works.

B. For the purposes of this ordinance the following definitions

apply:

1. Leaves- Deciduous and coniferous seasonal deposition.

2. Yard Waste- grass clippings, weeds, hedge clippings, garden

waste. and twigs and brush not longer than two (2) feet in length

and on-half (1/2) inch in diameter.

3. Paper Leaf Bag- A paper leaf bag “shall be a Sanitary Kraft

Paper Sack or equal of thirty (30) gallon capacity, two (2) ply

fifty (50) pound wet strength with decomposing glue and reinforced

self-supporting square bottom closure.

4. Leaf and Yard Waste collection season- the autumn leaf season

beginning the first full week of October and ending the second

full week of December.

C. Separation of Compostable Leaf and Yard Waste Material and

Placement for Removal.

During the Leaf and Yard Waste Collection Season Residents shall place

their leaf and yard waste material into paper leaf bags as defined in

Section 7.16.041.B. of barrels. These paper bags or barrels shall be place

on the curbside or treebelt in accordance with section 7.16.060 on the

special leaf and yard waste collection days specified by the Department of

Public Works and advertised in the Springfield daily newspapers.

Figure 3-2. Mandatory yard trimmings and leaf composting ordinance from the City of Springfield, NewYork.

26
Collection Methods

No material other than that specified in Section 7.16.041.B shall be

placed in these paper bags or barrels.

Compostable leaf and yard waste material shall not be placed in

plastic trash bags during the Leaf and Yard Waste Collection Season. Leaves

and yard waste shell not be placed in the same refuse Container aS or

otherwise mixed with other fores of solid waste for collection, removal, or

disposal during Leaf and Yard Waste Collection SeaSOn. Any violation of

this Section C or any part thereof shall be punishable by a fine not to

 exceed fifty dollars.

When the Owner has failed to comply with the requirements of Section C

of this Ordinance, the Director of the Department of Public works in his

discretions, my refuse to collect the leaf and yard waste material and all

garbage, or paper, ashes, or rubbish of the owner until the next regular

pick- up, and the owner shall remove from the curb such garbage, leaf and

yard waste material, and all other paper, ashes, and rubbish.

1). Ownership of Compostable Leaf and Yard Waste Materials.

Upon placement of compostable leaf and yard waste material for

collection by the City at the curbside or treebelt in accordance with the

special collection day, pursuant to this ordinance, such materials shall

become the property of the City. It shall be a violation of this ordinance

for any person; other than authorized agents of the City acting in the

course of their employment, to collect or pick up or cause to be collected

or picked up any compostable leaf and yard waste material so placed. Each

and every such collection or pick up in violations hereof from one or more

locations shall constitute a separate and distinct offense. The compostable

leaf and yard waste material collected by the City shall be transported to

and composted at a designated Leaf and Yard Waste Composting Site. Any

violation of this paragraph D or any part thereof shell be punishable by a

fine not to exceed one hundred ($100.00) dollars.

E. All ordinance, resolutions, regulations or other documents

inconsistent with the provisions of this ordinance are hereby repealed to

the extent of such inconsistency.

F. This ordinance and the various parts, sentences, and clauses

thereof are hereby declared to be severable. If any part, sentence, or

clause is adjusted invalid, it is hereby provided that the remainder of this

ordinance shall not be affected thereby.-

G. This ordinance shell take effect for the Leaf and Yard Waste

Collection Season commencing in 1988.

Approved:

Effective :

October 3, 1988

October 7, 1988

Attest : City Cler k

Source: Richard., 1990.

Figure 3-2. (Continued).

27
materials. Facility empolyees can look for and separate out unwanted materials (see Chapter 4)

Avoiding Undesirable Materials in Feedstock Collections Both yard trimmings and collected MSW can contain materials that might affect processing and prod

quailty. These materials can include glass, metals, beverage containers, plastics, household hazardous waste, and other undesirable materials. Collecting c

should be trained to recognize and separate these types of materials whenever possible. Because of the variety of materials collected, MSW feedstock is likely to

larger amounts of undesirable materials than yard trimmings feedstock. Although yard trimmings can contain pesticides and herbicides commonly used b

residents and businesses, the compsoting process will break down many of these substances, limiting their impact on the final product (see Chapter 6 for a more detai

Communties can takesteps to reduce the amount of undesirable materials in the feedstock. These include passing ordinances, posting warning notices, and i

finess for mixing noncompostables with compostables. In addition, bagged yard trimmings and MSW bins can be opened at the curb to detect undesirab

I

Collection Methods

Whichever curbside collection system is used, if the containerized yard trimmings are collected on the same day as

discards, provisions must be made for keeping the compostable materials separate after pickup. Compartmentalized vehicles can be used to accommodate this need; they

are especially efficient if all factions of the collected material will be processed at the same facility. Since the late

1980s, a number of compartmentalized trucks have come

on the market, some of which have compaction devices

for each compartment (see Appendix B). Using compartmentalized trucks can avert the expense of an extra pickup

crew. The amount of yard trimmings must be estimated

fairly accurately however, to prevent one compartment of

the truck from falling up before the other, forcing the crew

to deliver the materials before the entire vehicle is full.

(Although, on average, yard trimmings constitute 18 percent of the nation’s municipal discards, local factors such

as climate and demographics can affect the amount of

leaves or grass generated. Collection offficials often have

information pertaining to waste stream composition.) Another alternative that the community can choose is to require residents to separate yard trimmings into

color-coded or otherwise marked bags that can be sorted

easily at the processing facility.

Factors in MSW Collection

Communities that decide to collect MSW for composting

can opt to source separate or commingle this material.

Source-separated MSW involves varying degrees of materials segregation, which is performed where the MSW is

generated. Commingled MSW is not separated by the

generator. The decision to collect source-separated or

commingled MSW is a significant one and affects how

the material is handled at the composting facility, the preprocessing and processing costs, and the quality and marketability of the finished compost. Table 3-2 summarizes

the major advantages and disadvantages of each collection

method.

Source-Separated MSW

Source separation of MSW entails the segregation of compostables, noncompostables, and recyclable by individuals at the point of generation. The community then

collects and transports the separated materials accordingly.

Source-separation strategies can remove:

Compostable materials, such as certain grades of paper, that can be more economic.ally recycled than

composted. In some areas, markets for certain

grades of paper are strong. Therefore, a community

could opt to sell collected paper for its resource

value rather than compost it.

Noncompostable recyclable such as aluminum,

glass, and plastic beverage containers.

■ Materials that are difficult to compost such as

brush.

 Household hazardous waste such as paints, batteries, pesticides, and used oil.

n Noncompostable nonrecyclables such as light bulbs

and toothpaste tubes.

The primary benefit of source separation is that the feedstock tends to contain fewer unwanted materials, particularly heavy metals (Glaub et al., 1989). In addition, source

separation can help remove those items from the waste

stream that are difficult to separate at the facility, such as

plastic, which is often shredded; and glass, which can

shatter into small, hard-to-remove pieces. This produces a

higher quality compost, Most MSW composting facilities

in communities with source-separation programs peform

an additional sorting of incoming materials to produce a

still cleaner compost feedstock. Communities with MSW

composting facilities can combine source separation of

compostable materials with source separation of other recyclable materials such as glass, aluminum, and plastic.

A study conducted in 1990 revealed that a majority of

MSW composting facilities prefer processing source-separated over commingled MSW (Goldstein and Spencer,

1990). The study indicated that recycled materials are

cleaner and more marketable if source separated since they
Source Separatioin MSW

Collection of Commingled MSW

As of August 1993, plans were underway to open a 139,00 ton per year facility, including a 44,000 ton per year "wet" composting plant and an 85,000 ton peryear "dry" 

Wet/Dry Separation Strategies for Composting

Some communites in Canada and Europe are using or experimenting with the separation of materials into

wet and dry components. the City of Guelph in Ontario, Canada, reported a diversion rate of more than 60 percent using this collection strategy (Hoornweg

The wet stream includes all organic kitchen scraps, yard trimmings, nonrecyclable paper, and some noncompostable elements. the dry stream comp

dry noncompostables and recyclables. the dry waste stream is sent to a landfill or materials recovery facility (MRF) where recyclabes are removed for rec

Since 1989, Guelph has been conducting a pilot program to test four different material separation techniques in over 500 households. The city has fo

and placeing these components in green and blue plastic bins, respectively. The ciity currently is investigating other aspects of the program, including se

multi-family dwellings and commerical and educational institutions.

the highest diversion rates were achieved by citizens dividing the MSW stream into wet and dry components

materials are sent to a compost facility.

Collection Methods

Table 3-2. Source separation vs. commingling of MSW.

Advantages Disadvantages

Less chance of collecting unwanted object, which can result in a Can be less convenient to residents.

higher quality compost product. Might require the purchase of new equipment and/or conjoiners.

Less money and time spent an handling and separation at facility Might require additional labor for collection.

Provides an educational benefit to residents and might encourage

source reduction.

Usually done with existing equipment and labor resources. Higher potential for collecting unwanted objects, which can result in

a lower quality compost product.

Convenient to residents since no separation is required. Higher processing and facility costs.

are not mixed with undesirable materials. Moreover, the

amount of noncompostable material received at the composting facility is reduced. This means freer noncompostables must be separated out on site and sent to

landfills or recycling centers, resulting in lower transportation and labor expenditures. Finally, the quality and appearance of the compost can be improved and therefore

command a higher price. (Chapter 4 discusses the role of

source separation on preprocessing at the composting ficility in more detail; Chapter 9 discusses the role that

source separation can play in reducing heavy metals and

other contaminants in the final compost product.)

Source separation of MSW for composting can be done in

bins or bags. Some programs require that compostables,

noncompostables, and recyelables be placed in different

bins for curbside collection. While a large number of collection containers can be unsightly to some citizens, the

containers themselves are usually small since each one

holds small volumes of materials. Some municipalie.s

even use small baskets (similar to milk crates) to collect

glass, paper, and metals.

While source separation can avert many of the expenses

associated with preprocessing compostables, other costs

must be considered. The community very likely will have

to devote more labor to the collection process. In addition, containers or bins must be purchased either by the

municipality or citizens. The degree of participation is a

variable also, so a thorough public education and awareness campaign is necessary to encourage residents and

businesses to separate out noncompostables (see Chapter

l0).

Commingled MSW

Commingled MSW collection is the method that municipalities traditionally have used to pick up materials from

residents and businesses. Commingling allows residents to

combine trash, compostables, and recyclables in the same

containers. The municipality then collects and transports

the materials to the composting facility. Commingled

MSW collections usually can be done with existing equipment. Collection time and cost per ton often are less than

29
terial they discard

Collection Methods

those for separated materials since sanitation collectors

can fit more into single unit packer trucks at a faster rate.

Commingled commercial materials are deposited in large

metal or plastic bins equipped with hinged lids. These

bins are designed for easy transport to the processing facility. Some bins are equipped with a compactor, making it

possible to increase the capacity of each container.

Compaction can make separation more dificult, however,

and can greatly complicate the procedures and equipment

that will be used to compost.

The primary disadvantage of a commingled MSW collection program is that the separation must be performed as

soon as possible once the material arrives at the facility. At

the facility, the organic materials are typically separated by

both manual and mechanical means (see Chapter 4) in order to remove them from the recyclable and other noncompostable materials-a process that requires significant

labor and specialized equipment. Additionally commingling does not require individuals to change their behavior

thereby becoming more aware of the resource value of maSummary

w

hether designing a yard trimmings or MSW

composting program, collection is a key factor in ensuring the program's success. Not

only does collection have a direct bearing on the willingness of household to participate in and endorse a

program but the collection strategy chosen also influences the way that the feedstock is handled and processed at the facility as well as the quality and

marketability of the final product. Additionally collection can be one of the most expensive aspects of a

composting program and influences labor equipment, processing, and other resource needs. For these

reasons, decision-maken should carefully examine

and weigh all possible collection methods to determine the best approach for their community.

Chapter Three Resources

Appelhof, M., and J. McNelly. 1988. Yard waste composting guide. Lansing, MI: Michigan Department of Natural

Resources.

Ballister-Howells, P. 1992. Getting it out of the bag. BioCycle. March, 33(3):50-54.

Cal Recovery Systems (CRS) and M. M. Dillon Limited.

1989. composting A literature study. Ontario, Canada:

Queen’s Printer for Ontario.

Darcey, S. 1993. Communities put wet-dry separation to

the test. World Wastes. 36(98):52-57.

Glaub, J., L. Diaz, and G. Savage. 1989. Preparing MSW

for composting. As cited in: The BioCycle Guide to Composting Municipal Wastes. Emmaus, PA: The JG Press, Inc.

Glenn, J. 1992. Integrated collection of recyclable and

trash. BioCycle. January, 33(1):30-33.

Glenn, J. 1989. Taking a bite out of yard waste. BioCycle.

September, 30(9):31-35.

Goldstein, N., and B. Spencer. 1990. Solid waste composting facilities. BioCycle. January, 31(1):36-39.

Hoornweg, D., L. Otten, and W. Wong. 1991. Wet and

dry household waste collection. BioCycle. June, 32(6):

52-54.

Mielke, G., A. Bonini, D. Havenar, and M. McCann.

1989. Management strategies for landscape waste. Springfield, IL: Illinois Department of Energy and Natural ReRichard, T., N. Dickson, and S. Rowland. 1990. Yard waste

management A planting guide for New York State. Albany,

NY: New York State Energy Research and Development

Authority, Cornell Cooperative Extension, and New York

State Department of Environmental conservation.

U.S. Environmental Protection Agency (EPA). 1989. Decision-Maker’s Guide to Solid Waste Management.

EPA1530-SW-89-072. Washingron, DC: Office of Solid

Waste and Emergency Response.

Wagner, T.C. 1991. In search of the perfect curbside system. BioCycle. August, 32(8).

Wirth, R. 1989. Introduction to composting. St. Paul,

MN: Minnesota Pollution Control Agency, Ground

Water and Solid Waste Division.

30
Chapter Four

Processing Methods,

Technologies, and

Odor Control

T

his chapter describes the three stages of composting (preprocessing, processing and postprocessing) for both yard

trimming and MSWcomposting. It examines the operations that must be performed at each step in the process

and describes ways for optimizing those conditions that influence the process. In addition, this chapter discusses

the differnt technologies currently used to compost yard trimmings and MSW feedstocks in the United States. These

can range simple, low-technology systems that require minimal attention and maintenance to complex systems

that use sophisticated machinery and require daily monitoring and adjustment. The design and complexity ofa composting operation are determined by the volume, composition, and size distribution of the feedstock; the availability of

equipment the capital and operating funds; and the end-use specification for the finished product. This chapter also

examines the potential problems associated with odor and describes the measures a composting facility can take to prevent or minimize odor. A system flow chart for a typical operation that compost yard trimmings is shown in Figure 4-

1. Figure 4-2 outlines a process diagram for a typical MSW composting facility. For more information on costs

and effectiveness of the equipment described in this chapter, see Appendix B. Two case studies illustrating the process of

composting yard trimmings and MSW are included the back of this chapter.

Preprocessing

During preprocessing feedstock is prepared for composting.

Preprocessing has a significant impact on the quality of the

finished compost product and the speed at which processing

can be conducted. In general, the more effective the preprocessing the higher the quality of the compost and the greater

the efficiency of processing. Three procedures are typically

peformed during preprocessing 1) sorting feedstock material and removing materils that are difficult or impossible to

compost; 2) reducing the particle size of the feedstock material; and 3) treating feedstock to optimize composting conditions. These composting procedures are described below for

both yard trimming and MSW

Sorting

The level of effort required to sort and remove unwanted

materials from the composting feedstock depends on several factors, including the source of the feedstock, the end

use of the product, and the operations and technology

involved. The more diverse the feedstock material, the

more sorting and removal will be required. For this reason, yard trimmings (which tend to be relatively uniform)

generally require little sorting while MSW (which comprises heterogeneous materials) can require extensive sorting and separation. The end-use specifications for the

finished compost product also affect the level of effort involved as some end uses require a higher quality product

than others. For example, compost that will be used as

landfill cover can have higher levels of unwanted materials

than compost that will be used on food crops. Composting operations designed to produce landfill cover can

therefore utilize simpler and less thorough sorting and removal methods.

Sorting Techniques for Yard Trimmings Feedstock

Upon delivery to a composting site, yard trimmings

should be visually inspected to detect any materials that

could affect the composting process. Visual inspection can

be readily accomplished by spreading out the material on

31
Curside Preprocessing

Collection Yard Waste Drop-Off Site Sorting Shredding (Optionl) Add Water (If Needed)

MSW

End Markets 

Glass Plastic Paper Metal

To Recycling Facility

Add Water (If Needed)

Commingled Collection

Source-Seprated Collection

Preprocessing Sorting (Degree of sorting will depend on whether and how thoroghly the materials have been source separated) Screening Conveyor/ Hand Separation 

Processing Curing Composting Control Temperature Control Oxygen Control Moisture

Processing Methods, Technologies, and odor Control

Postprocessing

Shredding

and/or

Screening

(Optional)

Residuals

I

Residuals

Processing I

Bloprocessing

- i

Turn Combine

Curing Windrows Form

Windrows (Optional) Windrow

I I

Figure 4-1, Typical yard trimmings composting operation.

Separated

Collection

Sorting

(

whether and how

t

m

b

● 

. 

 SeparationTechniques

. Magnetic Recovery

. Eddy Current

separation Systems

● Air Classification

.Wet separatlon

Technologies

● Ballistic or Inertial

separation

Size Reduction

● Hammermills

• Shear Shredders

. Rotating Drums

Postprocessing

 Post-Processing

● Shredding

● Screening

. Bagging

Figure 4-2. Typical MSW composting operation.

32
Processing Methods, Technologies, and odor Control

the tipping floor where the feedstock is unloaded. Workers can then physically remove any undesirable objects

present. Materials that should be removed are those that

would interfere with mechanical composting operations,

inhibit the decomposition process, cause safety problems

for those working with or using the compost, or detract

from the overall aesthetic value of the finished compost

product. Plastic bags are the chief problem at most yard

trimmings composting facilities.

Feedstock with a significant amount of unwanted objects

can be hand-sorted more efficiently with a mechanical

conveyor belt. With this approach, the feedstock material

is loaded into a hopper that discharges at a slow speed

onto a conveyor belt. Workers on either side of the moving belt manually pick out glass, plastic, and other visible

noncompostables. To facilitate sorting, the belt width

should allow the workers to reach the center of the belt,

and the trimmings should not be more than 6 inches

deep. Materials removed from the conveyor belt are deposited into storage containers that can be moved easily to

other storage/processing areas. These noncompostable

materials are considered residuals from the composting

process and generally are recycled or disposed of by landfilling.

For reasons of health and safety, it is important that workers avoid physical contact with undesirable materials during manual sorting and removal. The sorting area should

be well-lit and properly ventilated, and the conveyor belt

should be setup to minimize motion injuries such as back

strain. Those handling the materials should wear heavy

gloves and follow specified hygiene practices (see Chapter

6 for more information on worker health and safety).

Sorting Techniques for MSW Feedstock

In general, sorting of MSW prior to composting requires

more labor and machinery than sorting yard trimmings

because of the diversity of MSW. As mentioned earlier,

MSW is extremely heterogeneous in size, moisture, and

nutrient content, and the organic fractions can contain

varying degrees of noncompostable and possibly hazardous waste. Both physical and chemical materials found in

the feedstock can have a negative impact on the marketability of the finished product, and their removal forms a

large part of the expense of modern MSW composting facilities (Richard, 1992). Both manual and mechanical

techniques can be used to sort feedstock materials and remove unwanted items.

Many items in the MSW composting feedstock are recyclable, such as aluminum cans, ferrous materials, and plastic bottles. Because of the potential value of these

recyclable, the separation, removal, and collection of

these items should be pursued. Although the MSW feedstock can be sorted after being subjected to size-reduction

processes, it is advisable to remove recyclable before size

reduction (this also will improve the value of recyclable).

Sorting before size reduction also will prevent recyclable

from being pulverized and mixed into the feedstock,

which can cause a variety of problems. For example, plastics are difficult to remove after they are shredded and

mixed with compostable materials. Shattered glass generates shards that can remain in the compost and devalue

the finished product as well as present a safety hazard both

to workers sorting the compost and to compost users.

Materials targeted during manual separation include recyclable and inert materials. As in the case of yard trimmings, manual separation along a conveyor belt represents

the most effective method to remove noncompostable

materials and chemicals from feedstock. Health and safety

provisions for manually sorting are particularly important

in the case of MSW feedstock, which might contain potentially dangerous items such as syringe needles, pathogenic organisms, broken glass, or other materials that

could cause injury or infection (see Chapter 6).

Mechanical sorting and removal techniques are based on

the magnetic and physical (i.e., weight and size) properties

of the feedstock materials. Magnetic-based systems separate

ferrous metals from the rest of the feedstock eddy-current

machines separate out nonferrous metals; size-based systems

such as screens separate different sizes of materials; and

weight-based systems separate out heavier noncompostable

materials such as metals, glass, and ceramics.

Table 4-1 outlines mechanical separation technologies

that are currently used in MSW composting. These technologies are discussed briefly below and in more detail in

Appendix B.

Screens - Screens are used in most MSW composting facilities to control the maximum size of feedstock and to separate materials into size categories.

The main purpose of this size fractionation is to Facilitate further separation. Screens separate small

dense materials such as food scraps, glass, and

small, hard plastic pieces from the bulky, light fraction of the feedstock. The type of screen used depends on the moisture content, cohesiveness,

heterogeneity, particle shape, and density of the

feedstock to be segregated. Trommel screens are

commonly used for initial materials processing at

MSW facilities. Figure 4-3 illustrates a trommel

screen.

Magnetic-based separators - Magnetic separators create magnetic fields that attract ferrous metals and

remove them from the rest of the feedstock stream

as it travels along conveyors. Magnetic separators

are among the most effective and inexpensive unit

processes available for sorting and removing contaminants from the feedstock. The economic benefits of these devices are enhanced by selling the

33
ening Large: Film plastic, large paper cardboard. Mid-sized: recyclable, most organics, Fine: Organics, metal fragments. 

Wet Separation Floats: Organics. Sinks: Metals, glass, gravel.

Air Classificaion Light: Paper, plastic. Heavy: Metals, glass, organics. 

Eddy-Current Separation Nonferrous metals.

Processing Methods, Technologies, and Odor Control

Table 4-1. Processing MSW feedstock separation

techniques.

Technology Materials Targeted

Magnetic Ferrous metal.

Separation

Ballistic Separation Light: Plastic, undecomposed paper. Heavy: Metals, glass, gravel.

Source: Richard, 1992.

scrap metals these units separate from the compostable materials. The efficiency of magnetic separators depends primarily on the quantity of

materials processed and the speed at which they

pass through d-se magnetic field. The size and shape

of the ferrous objects, as well as the distance between the magnet and the objects, also are important variables. To increase the efficiency of the

separation process, more than one magnetic separation technology can be used in series with another.

Applying air classification (described below) prior

to magnetic separation minimizes the contaminants in the scrap ferrous even further.

Eddy-current machines - Eddy-current machines

separate aluminum and other nonferrous metals

from MSW. These machines generate a high-energy electromagnetic field that induces an electrical

charge in nonferrous metals (and other materials

that conduct electricity). The electrical charge

forces these materials to be repelled from noncharged fractions of the feedstock material. The

feedstock should be conveyed to eddy-current machines after magnetic separation to minimize contamination by ferrous metals. Recovery rates for

eddy-current separators vary with the depth of the

material on the conveyor belt, belt speed, the degree of preprocessing and the strength of the magnetic field. Full-wale trials and manufacturer

■

■

estimates of separation efficiency in MSW applications range from 50 to 90 percent. Figure 4-4 illustrates an eddy current separator.

Air classifiers - Air classifiers separate feedstock materials based on weight differences; for example, the

heavier fractoions (metals, glass, ceramics, and

rocks) are removed from the lighter materials. The

heart of an air classification system is an air column

or throat into which the materials stream is fed at a

metered rate. A large blower sucks air up through

the throat, carrying light materials such as paper

and plastic. These then enter a cyclone separator

where they lose velocity and drop out of the air

stream. Heavy materials fall directly out of the

throat. An important consideration when using air

classifiers is that although most of the heavier materials separated out are noncompostable, some materials that fall out (e.g., certain food materials and

wet paper) can be composted (Glaub et al., 1989).

Air classifiers typically are used after the feedstock

has been size-reduced. Separation efficiency in experimental application of air classification systems

has reached 90 percent for plastics and 100 percent

for paper materials. In combination with screening

and size reduction, air classification can be used to

significantly reduce metal contaminant levels. Figure 4-5 illustrates an air classification system.

Wet separation technologies - Wet separation technologies are similar to air classification systems in

that they separate materials based upon density, but

water replaces air as the floating medium in these

technologies. After entrainment in a circulating

water stream, the heavy fraction drops into a sloped

tank where it moves to a removal zone. The lighter

organic matter floats and is removed from the recirculating water using stationary or rotating screening systems similar to those employed by

wastewater treatment facilities. This technology is

particularly effective for removing glass fragments

and other sharp objects.

Ballistic or inertial separation - This technology separates inert and organic constituents based upon

density and elasticity differences. Compost feedstock is dropped on a rotating drum or spinning

cone and the resulting trajectories of glass, metal,

and stones, which depend on density and elasticity,

bounce the materials away from the compost feedstock at different lengths. Figure 4-6 illustrates a

ballistic separator.
Feed

External Drum (rotates at Slow speed) Alternating Polarity Rotor(rotates at high speed) Non-Conductors 

Prcessing Methods, Technologies, and Odor Controli

Oversize

Fine Medium

Undersize

Source: Richard, 1992.

Figure 4-3. Trommel screen.

Feedstock

v

External

(rotates at SI

Conductors

(wood, paper (aluminum, brass,

plastic, glass) copper, etc.)

Source: Richard, 1992.

Figure 4-4. Eddy-current separator.

35
Blower Exhaust Air Cyclone Separator

MSW Infeed Light

Airstream

Airlock

Heavy

Processing Methods, Technologies, and Odor Control

Rotary

Source: Richard, 1992.

Figure 4-5. Air classification system.

Light Fraction

Fraction

Light Organic Dense Organic Source: Richard, 1992, inorganic

Figure 4-6. Ballistic separator.

36
Processing Methods, Technologies, and Odor Control

Reducing the Particle Size of the Feedstock

Size reduction usually is performed after noncompostables

have been separated from the compostable feedstock.

Some separation technologies, including magnetic separation, air classification, and wet separation, achieve greater

levels of removal only after size reduction, however. The

exact order of steps varies in different composting operations depending on the type and volume of feedstock to

be composted. Proper sequencing of the-se preparation

processes can have a significant impact on system

performance.

The primary reason for performing size reduction is to increase the surface area to volume ratio of the feedstock

materials. This enhances decomposition by increasing the

area in which microorganisms can act upon the composting materials. If composting materials are too small, however, air flow through the compost pile will be reduced.

This reduced oygen availability has a negative impact on

decomposition. Maximizing composting efficiency requires establishing a balance between reducing particle

size and maintaining aerobic conditions. A study of the

tradeoff between increased surface area for decomposition

and reduced pore size for aeration concluded that particle

sizes of 1.3 to 7.6 cm (O. 5 to 3.0 inches) are most efficient

(Gray and Biddlestone, 1974). The lower range is suitable

for forced aeration systems while the larger range is preferred for windrows and other systems supplied with oxygen by passive diffusion and natural convection.

Yard Trimmings

Size reduction of most types of yard trimmings can help

accelerate the composting process. Size reduction is warranted for woody material mixed with other yard trimmings since wood decomposes at a very slow rate and

might delay the development of the compost end product. Some facilities have found that shredding leaves as

well will reduce the time required to produce finished

compost from 18 months to 9 months (Richard et al.,

1990). Excessive size reduction of leaves and grass could

prove undesirable, however, because small particles can inhibit aerobic conditions and impede release of heat from

the composting masses. If grass clippings become compacted, they can restrict oxygen flow and create anaerobic

pockets in the composting mass. Finely shredded yard

trimmings must be turned more frequently to prevent

these anaerobic conditions. Tub grinders are a common

piece of size reduction machinery at large Facilities for composting yard trimmings. These grinders use a rotating tub to

feed a horizontal hammermill (see following section).

MSW

Size reduction homogenizes MSW feedstock materials,

achieving greater uniformity of moisture and nutrients to

encourage even decomposition. A variety of size-reduction

devices are available, the most common of which are

hammermills, shear shredders, and rotating drums. This

equipment is outlined below and described in more detail

in Appendix B.

Hammermills - Hammermills reduce the size of

feedstock materials by the action of counter rotating sets of swinging hammers that pound the feedstock into smaller sized particles. The hammer axles

can be mounted on either a horizontal or a vertical

axis and usually require material to pass through a

grate before exiting. Mills that lack the exit grate

are termed flail mills. Figure 47 illustrates a

hammermill.

Shear shredders - Shear shredders usually consist of

a pair of counter rotating knives or hooks that rotate at a slow speed with high torque. The shearing

action tears or cuts most materials, which helps

open up the internal structure of the particles and

enhances opportunities for decomposition.

Rotating drums - Rotating drums use gravity to

tumble materials in a rotating cylinder. Material is

lifted by shelf-like strips of metal along the sides of

the drum, which can be set on an incline from the

horizontal. Some of the variables in drum design include residence time (based on length, diameter,

and material depth), inclination of the axis of rotation, and the shape and number of internal vanes

(which lift materials off of the bottom so they can

fall through the air). Figure 4-8 illustrates a rotating drum.

If materials such as gas cylinders and ignitable liquids are

present in MSW feedstock, there is a potential for explosions during size reduction. Visual inspection, along with

sorting and removal procedures, can minimize this potential. Nevertheless, size reduction equipment should be isolated in an explosion-proof area within the composting

facility, and proper ventilation for pressure relief should be

provided.

Treating Feedstock Materials to Optimize

Composting Conditions

To enhance composting, both yard trimmings and MSW

feedstock can be treated before processing. Such treatment

can optimize moisture content, carbon-to-nitrogen (C:N)

ratio, and acidity/alkalinity (pH). (These parameters were

introduced in Chapter 2.)

Moisture Content

Maintaining a moisture content within a 40 to 60 percent

range can significantly enhance the composting process.

Before composting begins, the feedstock should be tested

for moisture content. The “squeeze test” is a simple

37
Grate

Hammer

Processing Methods, Technologies, and Odor Control

method of determining whether the moisture content falls

within the proper range. If just a few drops of water are

released from a handful of the feedstock when squeezed,

the moisture content is acceptable. If a more definitive determination of moisture content is needed, a sample of

the feedstock can be weighed, oven-dried at about 104°C

Feedstook

-Free Swining

Rotating Hammermil l

Source: Richard, 1992.

Figure 4-7. Hammer-mill.

(219°F) for 8 hours, and weighed again. The moisture

content can be derived by the following formula:

moisture content = (wet weight – dry weigh)wet weight

With yard trimmings, the moisture content of leaves

tends to be lower than optimal. The moisture content of

grass tends to be higher than optimal. Moisture, therefore,

should be added to dry leaves, generally at a level of about

20 gallons of water per cubic yard of leaves (Richard et al.,

1990). During the early stages of composting leaves must

be mixed during wetting to prevent the water from running off the pile surface. On the other hand, grass should

be mixed with drier materials (such as leaves or wood

chips) or turned more frequently during the initial stages

of processing to facilitate the evaporation of excess water.

Moisture content in the MSW feedstock varies widely.

Significant attention, therefore, should be paid to assessing moisture levels of MSW and mixing materials streams

to optimize moisture content of the composting feedstock. For high-rate MSW composting, a minimum moisture content of 50 to 55 percent is recommended

(Goluek, 1977). Since MSW feedstock is often drier

than this, water must be added during the composting

and curing singes to bring the moisture content into the

optimal range. MSW compost mixtures usually start at

about 55 percent moisture and dry to 35 percent moisture

(or less) prior to find screening and marketing (CC, 1991).

Mechanical aeration and agitation directly influence the

moisture content of the composting pile. Aeration increases flow through the composting pile, inducing

evaporation from the interior spaces. Turning composting piles exposes the interior of the piles, releasing

heated water as steam. This moisture loss can be beneficial, but if excess moisture is lost (i.e., the moisture

content falls to 20 percent), rewetting might be required (Richard, 1992). MSW composting piles usually

require additional water.

lnfeed

I Source: Richard, 1992.

Outfeed

1

Figure 4-8. Rotating drum.

38
Mixed MSW 50-60:1

Leaves (fresh) 30-40:1

Mixed Grasses 19:1

Nonlegume Vegetalbe Scraps 11-12:1

Poultry Manure 15:1

Biosolids 11:1

Weeds (fresh) 25:1

Seaweed 19:1

Food scraps 15:1

Fruit Scraps 35:1

Grass Clippings 12-20:1

Hay(dry) 40:1 

Horse Manure 25:1

Humus 10:1

Cow Manure 18:1

High Nitrogen Content

Wood 700:1

Straw (dry) 100:1

Paper 170:1

Sawdust 500:1

Leaves and Weeds (dry) 90:1

Foliage 40-80:1

Corn Stalks 60:1

Bark 100-130:1

High Carbon Content

Processing Methods, Technologies, and Odor Control

Finally temperature determines how much moisture will be

lost with turning and aeration; the higher the temperature,

the more water will be lost via evaporation. In turn, moisture

loss afects the temperature of the piles.

Carbon-to-Nitrogen (C:N) Ratio

Most of the nutrients needed to sustain microbial decomposition are readily available in yard trimmings and MSW

feedstocks. However, carbon and nitrogen might not be

present in proportions that allow them to be used efficiently by microorganisms. composting proceeds most efficiently when the C:N ratio of the composting material is

from 25:1 to 35:1. When the C:N ratio is greater than

35:1, the composting process slows down. When the ratio

is less than 25:1, there can be odor problems due to anaerobic conditions, release of ammonia, and accelerated

decomposition.

Generally, the C:N ratio for yard trimmings can be

approximated by examining the nature of the feedstock;

green vegetation is high in nitrogen and brown vegetation

is high in carbon. While the diversity of MSW feedstock

material makes an estimation of the C:N ratio somewhat

difficult, a precise C:N ratio can be determined by laboratory analysis. Feedstock materials with different C:N ratios

can be mixed to obtain optimal levels of carbon and nitrogen when necessary (see Table 42 for carbon-to-nitrogen

ratios for various organic materials).

Acidiiy/Alkalinity (pH)

The closer the pH of the feedstock material is to the neutral value of 7, the more efficient the composting process

will be. Fresh leaves tend to have pH levels of approximately 7 (Strom and Finstein, 1989). Fruit scraps generally are acidic with a pH below 7 (CRS, 1989). Kits to

test pH levels are readily available and easy to use. If pH

levels are significantly higher than 8 (an unusual situation), acidic materials, such as lemon juice, can be added

to the feedstock. If the feedstock has a pH significantly

below 6, buffering agents, such as lime, can be added. Because pH levels are largely self-regulating, actions to bring

pH to optimum levels are rarely necessary (CRS, 1989;

Strom and Finstein, 1989).

Mixing

Mixing is often required to achieve optimal composting

conditions. Mixing entails either blending certain ingredients with feedstock materials or combining different types

of feedstock materials together. For example, bulking

agents (such as wood chips) are often added to feedstock

materials that have a fine particle size (such as grass).

Bulking agents have the structural integrity to maintain

adequate porosity and help to maintain aerobic conditions in the compost pile. Bulking agents are dry materials

and tend to have a high carbon content. Therefore,

Table 4-2. Carbon-to-nitrogen ratio of various materials.

Type of Feedstock Ratio

Source: Golueke, 1977; Richard et al., 1990; Gray et al., 1971b.

whenever bulking agents are used, are should be taken to

ensure that C:N ratios do not become too high.

Mixing is most efficient when it is conducted after feedstock sorting and size reduction and before processing begins. This can minimize the quantity of materials that

must be mixed because noncompostables have been removed. In addition, once piles have been formed for processing adequate mixing becomes extremely difficult.

For simple composting operations that do not require

high levels of precision, mixing can be performed during

size reduction or pile formation by feeding different

ingredients or types of materials into these operations.

When higher levels of precision are required, mixing

equipment (such as barrel, pugmill, drum, and auger

39
Processing Methods, Technologies, and Odor Control

mixers) M be used (see Appendix B). Most mixers also

compress materials, which can reduce pore space in the

feedstock and inhibit aeration in the compost pile. Mixers

also have relatively high capital and operating and maintenance costs so it might be impractical for smaller facilities

to use them, particularly those that compost only yard

trimmings.

Processing

After yard trimmings and MSW feedstock

preprocessed, they can be introduced into

materials are

the compost

processing operations. During processing, various m&hods can be employed to decompose the feedstock materials and transform-them into a finished compost product.

Processing methods should be chosen to maximize the

speed of the composting process and to minimize any

negative effects, such as odor release and leachate runoff.

The level of effort required for processing composting

feedstock depends on the nature of the feedstock, the desired speed of production, the requirements for odor and

leachate control, and the quality requirements for the finished compost. A facility’s financial resources and available

space also are important. In general, the greater the speed

of the process, the more odor and leachate control necessary. Where greater space or level of effort is needed, more

financial resources will be required.

In general, more resources and higher levels of effort are

necessary to compost a MSW feedstock than a yard

trimmings feedstock, largely because of the diverse nature of MSW. For composting either yard trimmings or

MSW, processing occurs in two major phases: the composting phase and the curing phase. These stages are discussed below.

The Composting Stage

Microorganisms decompose the readily available nutrients

present in the feedstock during composting. Because most

of the actual change in the feedstock occurs during this

stage, the most intensive methods and operations tend to

be used here. Compost processing can occur in simple environments that are completely subject to external forces

or in complex and highly controlled environments. The

composting methods currently employed are (in order of

increasing complexity):

■ Passive piles

■ Turned windrows

■ Aerated static piles

■ In-vessel systems

Passive Piles

Although this method is simple and generally effective, it

is not applicable under all conditions or to all types of

4 0

materials. composting under these conditions is very slow

and is best suited to materials that are relatively uniform

in particle size. Although passive piles theoretically can be

used for composting either yard trimmings or MSW, the

propensity for odor problems renders them unsuitable for

MSW feedstock materials or even large quantities of grass

or other green materials that have a high nitrogen content.

Passive piles require relatively low inputs of labor and

technology. They consist of piles of composting material

that are tended relatively infrequently usually only once

each year. Tending the piles entails turning them (i.e.,

physically tearing down and reconstructing them), Figure

4-9 illustrates the proper method of turning a compost

pile. Such an effort requires only a few days’ use of personnel and equipment, making this a relatively low-cost

composting method.

Before piles are turned, the moisture content of internal

and external layers of the compost pile should be checked

using the methods discussed in the preprocessing section

of this chapter. If the moisture content is too low, water

can be added by manually spraying the pile with hoses or

by using automatic sprinklers or irrigation systems. If the

moisture content is too high, turning can be conducted

more frequently to increase evaporation rates.

With all composting methods, regular monitoring of the

temperatures of composting materials is recommended. A

variety of long-stem (3-foot) digital and dial-type thermometers and infrared scanners are available that can read

temperatures up to 93°C (199oF).

Passive piles should be constructed large enough to conserve sufficient heat but not so large as to overheat. If temperatures of the composting mass exceed 60oC (140o

F),

composting materials can combust, and/or microorganisms needed for decomposition can be killed. Compost

piles should be turned if this temperature is exceeded.

Even if temperature and moisture are not monitored with

the passive pile composting method, the periodic turning

of the piles will adjust the oxygen level, moisture content,

and temperature to some degree. The movement created

by turning aerates the pile, and the anaerobic center is replaced with oxygen-rich external layers of the material. In

addition, dry internal materials are exposed to the outer

layers of the pile where they are more susceptible to wetting by rain or snow. The increased aeration and wetting

caused by turning also serve to reduce temperatures in the

internal layers, preventing excessive heat buildup. Temperature and oygen levels also can be controlled somewhat by forming piles of the appropriate size. The larger

the pile, the greater the insulation and the higher the temperature levels that can be reached. The larger the pile,

however, the lower the degree of oxygen penetration and

the greater the potential for anaerobic conditions forming

in the center of the pile.
Processing Methods, Technologies, and Odor Control

they are exposed to higher temperatures and more intensive microbial activity. The turned windrow method results in the completion of the composting process for yard

trimmings in approximately 3 months to 1 year (UConn

CES, 1989).

Turned windrow operations generally can be conducted

outdoors. To increase the operator’s ability to control

composting conditions, however, windrows can be placed

under or inside shelters. Leachate problems should be

minimized by constructing windrows on firm surfaces

surrounded by vegetative filters or trenches to collect runoff (see Chapter 6). (A paved surface might be helpful, depending on the size and location of the facility and how

muddy it might get.) Run-on controls also are helpful as

is careful balancing of the C:N ratio. Progressive decomposition of the composting materials reduces the size of

the windrows, allowing them to be combined to create

space for new windrows or other processes,

As with passive piles, forming windrows of the appropriate size helps maintain appropriate temperature and oxygen levels. The ideal height for windrows is from 5 to 6

feet (CRS, 1989). This height allows the composting materials to be insulated properly but prevents the buildup of

excessive heat. Windrow heights vary, however, based on

the feedstock, the season, the region in which the

composting operation is being conducted, the tendency of

the composting materials to compact, and the turning

equipment that is used. Windrow widths generally are

Lift compost high with bucket loader and let compost fall to new

location to create a cascading mixing effect.

Note: The principle of the mixing technique is to

move the top of the pile to the bottom of

the pile being formed mixing the material

Adapted from: UConn CES, 1989. well during this process.

Figure 4-9. Pile turning for aeration and mixing.

Several disadvantages are associated with passive pile methods. Unlike more intensive composing processes that can

produce a finished product in a few weeks to a few months,

passive piles can require over 1 year for the composting process to be completed. In addition, the minimal turning of

passive piles results in the formation of anaerobic conditions

so that when piles are eventually turned (especially for the

first year or two of the process) significant odors result. Passive piles consequently cannot be placed in densely populated areas, and a large buffer zone is recommended between

residents and composting operations (Strom and Finstein,

1989). The untended passive piles also might resemble

dump sites to community members who might discard trash

at the site. Some means of controlling access to the passive

pile site is, therefore, recommended. Finally large, untended

piles have the potential to overheat and combust, creating a

possible fire hazard.

Turned Windrows

Tinnedwindrows are a widely used method for composting yard trimmings and MSW. This method generally is

not appropriate, however, for MSW containing significant

amounts of putrescible materials due to odor concerns.

Tuned windrows are elongated composting piles that are

turned frequently to maintain aerobic composting conditions. The frequent turning promotes uniform decomposition of composting materials as cooler outer layers

of the compost pile are moved to inner layers where

41
Processing Methods, Technologies, and Odor Control

twice the height of the piles. Factors such as land availability, operating convenience and expedience, type of turning equipment used, and interest in the end product

quality also affect the chosen windrow width. Careful

monitoring of width is unnecessary, however, to ensure

that proper oxygen and temperature levels are maintained;

windrow height determines aeration levels to a far greater

degree than windrow width. Windrow length also has little impact on the composting process.

Windrow shapes can be altered to help maintain appropriate composting conditions (primarily moisture levels).

For example, windrows with concave crests are appropriate during dry periods and when the moisture content of

the composting material is low to allow precipitation to

be captured more efficiently. Peaked windrows are preferable during rainy periods to promote runoff of excess

water and to prevent saturation. Illustrations of these

windrow shapes are presented in Figure 4-10.

The same types of operations used to monitor critical

composting conditions in the passive pile method also can

be used with turned windrow composting. The more frequent turning of composting materials with the turned

windrow technique does tend to maintain oxygen, moisture, and temperature at appropriate levels, however.

Where odor control and composting speed are a high priority, oxygen monitoring equipment can be installed to

alert operators when oxygen levels fall below 10 to 15

percent, which is the oxygen concentration required to

encourage aerobic decomposition and minimize odor

problems (Richard, 1992).

Turning frequencies for this method can range from twice

per week to once per year. In general, the more frequently

that the piles are turned, the more quickly the composting

process is completed. Some materials do not need to be

turned as frequently to maintain high levels of decomposition. For example, structurally firm materials have greater

porosity and therefore can maintain aeration for greater

periods of time without turning. Ideal turning patterns

should move the outside layers of the original windrow to

the interior of the rebuilt windrow (this pattern is shown

in Figure 411). If this pattern is not feasible, then care

should be taken to ensure that all materials spend sufficient time in the interior of the pile. Inefficiencies in the

turning pattern can be compensated for by increasing the

frequency with which the windrows are turned.

The turning equipment used will, in part, determine the

size, shape, and space between the windrows. Front-end

loaders are commonly used in smaller operations. The

quantity of materials that they can handle as well as the

control that they can exercise over the turning process is

limited, however. When this equipment is used, enough

space must be maintained between windrows to allow the

front-end loaders to maneuver and turn the piles. Windrow turners are larger machines that are often used at

Landspreading

and spreadhg involves the placement of organic

materials on the ground for decomposition under

uncontroled conditions. A few simple interventions, however, such as reducing feedstock particle size

or periodically turning materials with a plow, can be

used to accelerate decomposition. Landspreading requires very low inputs of labor and technology and is;

therefore relatively inexpensive.

Unlike composting, material that have been landspread are first degraded by the actions of soil dwelling

microorganisms such as worms and insects. Once the

feedstock is size reduced by these Macroorganisms,

mesophilic microorganisms begin decomposition

which proceeds at low temperatures and slow rates

(CRS, 1989). Since the feedstock is applied to the

land before any processing is conducted, this method is

not appropriate for MSW, which is more likely to conrain pathogenic and chemical materials than yard trimmings. Yard trimmings that have been exposed to high

pesticide levels also should not be landspread.

TO increase the efficiency of the landspreading the ,

feedstock materials can be shredded prior to application. This increases the uniformity of the particle size

of the materials, thereby accelerating composting,

Some states govern the level of application of materials

to acreage according to water quality concerns and agronomic soil tests. Siting the operations as close to the

source of the feedstock materials as possible also should

be pursued to minimize transportation costs, For these

reasons, careful consideration should be given to siting

landspreading operations,

Landspreading of materials that decompose rapidly

can enhance plant growth. If the feedstock is applied

at the appropriate time, the decomposition process

will be completed before crops are planted, The de-

 composed feedstock materials will then act as a soil

 amendment product and assist in crop growth. If

 however, crops are planted before the decomposition

is completed, landspread leaves can reduce crop yield

 by tying up otherwise available nitrogen and reduc-

: ing oxygen availability. Also, extensive separation op-

 erations might be needed to remove unwanted

materials such as brush and glass. Finally, raw leaves

and grass can be diffcult to handle and have a ten-

 dency to clog farm machinery.

facilities that compost large volumes of material. These

machines can be either self-propelled or mounted to

front-end loaders. Self-propelled windrow turners can

straddle windrows, minimizing the required space between windrows and consequently reducing the space

42
Processing Methods, Technologies, and Odor Control

requirements for the composting process. Windrow turners should peform several functions including increasing

porosity of the pile, redistributing material to enhance process homogeneity, and breaking up clumps to improve product homogeneity.

Aerated Static Piles

Aerated static piles, sometimes called forced aeration

windrows, are a relatively high-technology approach that

can be used to compost both yard trimmings and MSW.

This approach is effective when space is limited and the

composting process must be completed within a year. In

this method, piles or windrows are placed on top of a grid

of perforated pipes. Fans or blowers pump or pull air

through the pipes and, consequently through the composting materials. This maintains aeration in the compost

pile, minimizing or eliminating the need for turning. In

some operations, the pipes are removed her 10 to 12

weeks of composting and the piles or windrows are then

turned periodically.

Aerated static piles are 10 to 12 feet high on average. To

facilitate aeration, wood chips (or other porous materials)

are spread over the aeration pipes at the base of the pile.

The feedstock is then added on top of the wood chips. It

might be necessary to top off the pile with a layer of finished compost or bulking agent. This protects the surface

of the pile from drying, insulates it from heat loss, discourages flies, and filters ammonia and potential odors

generated within the pile (Rynk et al., 1992). It can take

as little as 3 to 6 months to produce finished compost

with this method.

Air can be supplied to the process through a suction system or a positive pressure system. The suction system

draws air into and through the pile. The air then travels

through a perforated pipe and is vented through a pile of

finished compost, which acts as an odor filter (see Figure

4-1 1). With this system, condensate from water vapor

drawn from the pile must be removed before the air

reaches the blower. The ability to contain exhaust gases

for odor treatment is an important advantage of suction

aeration. The presence of this odor filter, however, more

than doubles the pressure losses of suction aeration.

The positive pressure aeration system uses a blower to

push air into the compost pile. The air travels through the

pile and is vented over its entire surface. Because of the

way air is vented, odor treatment is difficult with positive

pressure aeration. The absence of an odor filter, however,

means lower pressure losses with this system, which results

in greater air flow from the same blower power. Therefore,

positive pressure systems can be more effective at cooling

the pile and are preferred when warm temperatures are a

major concern (Rynk et al., 1992).

To ensure that decomposition proceeds at high rates, temperature and oxygen levels must be closely monitored and

maintained with aerated static pile composting. Aeration

management depends on how the blower is controlled.

The blower can be run continuously or intermittently.

Continuous operation of the blower permits lower air flow

rates because oxygen and cooling are supplied constantly

however, this leads to less uniform pile temperatures. Intermittent operation of the blower is achieved with a

r ?

Concave Shape - Traps Water Peak Shape- sheds water

Source: Richard et al., 1950

Figure 4-10. Windrow shapes for maximum and minimum water adsorption.

43
Pile height H = 5-8 feet 6-inch cover layer 6-to 12-inch base Pile width W=2H

View B-B

Pressure

of

Blower

Well-mixed

Perforated

cover

Pipe

Processing Methods, Technologies, and odor Control

Suction

Cover layer

finished compost

raw material

Porous

base Condensate trap

- .-------- - ---.A- ----- -

Pile width l/3w

W=2 H to B

(10-16 feet) 1/4W 

---- - --- - ----- - - -

A Compos t

70-90 feet maxium

H 5-8fee t

Source: Rynk et al., 1992.

Figure 4-11. Aerated static pile.
Raw materials Exhaust air

Rotation

materials

Compost to

Processing Methods, Technologies, and Odor Control

programmed timer or a temperature feedback system.

Triers are a simple and inexpensive method of controlling blowers to provide enough air to satisfy oxygen requirements and control temperatures. This approach does

not always maintain optimum temperatures, however. A

temperature feedback system does attempt to maintain

optimum pile temperatures, for example, within the range

of 54 to 60°C (129 to 140°F) (Rynk et al., 1992). Electronic temperature sensors, such as thermocouples or thermistors, switch the blower on or off when the temperature

exceeds or falls below a predetermined level. The blower

switches on to provide cooling when the temperature rises

above its high temperature, usually around 570C (135°F),

and switches off when the pile cools below a set point (Rynk

et al., 1992).

In general, the aerated static pile method is best suited for

granular and relatively dry feedstock materials that have a

relatively uniform particle size of less than 1.5 to 2 inches in

diameter. This is because large or wet materials and materials

of diverse sizes have a tendency to clump. Clumping constricts air flow through the piles, leads to short circuits of air

pumping equipment, produces anaerobic pocks, and otherwise limits the rate of decomposition. Aerated static piles

are commonly used for composting wet materials (such as

biosolids), however. Clumping is controlled by proper mixing of bulky materials that adjust porosity and moisture.

In-Vessel Systems

In-vessel systems are high-technology methods in which

composting is conducted within a fully enclosed system.

All critical environmental conditions are mechanically

controlled with this method, and, with most in-vessel

systems, they also are fully automated. These systems are

rarely used to compost yard trimmings because it is expensive to maintain this degree of control. More and

more facilities are selecting in-vessel systems for their

MSW composting program. An in-vessel system can be

warranted for MSW if 1) the composting process must

be finished rapidly, 2) careful odor and leachate control

are a priority, 3) space is limited, and 4) sufficient resources are available.

In-vessel technologies range from relatively simple to extremely complex systems. Two broad categories of in-vessel technologies are available: rotating drum and tank

systems. Rotating drum systems rely on a tumbling action

to continuously mix the feedstock materials. Figure 4-12

illustrates a rotating drum composter. The drums typically

are long cylinders, approximately 9 feet in diameter,

which are rotated slowly, usually at less than 10 revolutions per minute (CRS, 1989). Oxygen is forced into the

drums through nozzles from exterior air pumping systems. The tumbling of the materials allows oxygen to be

maintained at high and relatively uniform levels throughout the drum. The promotional literature for rotating

drums indicates that composting materials must be retained in the drums for only 1 to 6 days (CRS, 1989).

Complete stabilization of the composting material is not

possible within this timeframe, however, and further composting and curing of from 1 to 3 months is necessary

(CRS, 1989),

Tank in-vessel systems are available in horizontal or vertical varieties. Rectangular tanks are one type of horizontal

in-vessel system. These tanks are long vessels in which

aeration is accomplished through the use of external

pumps that force air through the perforated bottom of the

tanks. Mixing is accomplished by mechanically passing a

Air

source: Rynk et al.,1992.

Second stage

Figure 4-12. Rotating drum composter.

45
Compost discharge

Air plenum or gravel Turning machine

Carriage machine

base with aeration pipe underneath

Blowers

Processing Methods, Technologies, and Odor Control

moving belt, paddle wheel, or flail-covered drum through

the composting material. This agitates the material, breaks

up clumps of particles, and maintains porosity. Composting materials are retained in the system for 6 to 28 days

and then cured in windrows for 1 to 2 months.

The agitated-bed system is an example of this type of

horizontal in-vessel system. Figure 4-13 illustrates a rectangular agitated-bed composting system. composting

takes place between walls that form long narrow channels

(called beds). A rail or channel on top of each wall supports and guides a compost-turning machine. Feedstock is

placed at the front end of the bed by a loader, and the

turning machine mixes the composting material and

discharges it behind the machine as the material moves

forward on rails. An aeration system in the floor of the

bed supplies air and cools the composting materials. In

commercially available systems, bed widths range from 6

to 20 feet, and bed depths are between 3 and 10 feet. Suggested composting periods for commercial agitated-bed

systems range from 2 to 4 weeks (Rynk et al., 1992).

Vertical tank in-vessel systems use a vertical tank orientation. Forced aeration and stirring also are used with this

method. These systems can consist of a number of tanks

dedicated to distinct stages of the composting process or

of one tank (which might be divided into different

“floors”). Vertical tank in-vessel systems might use conveyors,

(one for each aeration

zone in everv bed)

(moves towards raw

materials loading end)

Raw materials loaded

to transport the turning

to the next bed

Sources Rynk et al., 1992.

Figure 4-13. Rectangular agitated-bed composting system.

46
Processing Methods, Technologies, and Odor Control

rotating screws, air infeeds, or air outfeeds to agitate compost, move compost between tanks, and maintain proper

levels of oxygen and moisture. A problem with vertical

tank in-vessel systems is the difficulty of maintaining an

equilibrium of moisture and air between the layers inside

the tank. In an attempt to adequately aerate the top layers

of the compost, these systems can cool down the bottom

layers of compost. Furthermore, excessive condensation

can form at the top of vertical tanks where moisture and

temperature levels are uncontrollable.

The Curing Stage

Once the materials have been composted, they should be

cured. Curing should take place once the materials are

adequately stable. While testing for stability is an inexact

science, oxygen uptake and C02 evolution tests can be

considered to discern the degree of maturity of compost

derived from MSW feedstock. For compost derived from

yard trimmings, simpler methods can often suffice. One

method is to monitor the internal temperature of the

compost pile after it is turned. If reheating of the pile occurs, then the material is not ready for curing. Another

method is to put the compost material in a plastic bag for

24 to 48 hours. If foul odors are released when the bag is

opened, the materials are not ready for curing.

During the curing stage, compost is stabilized as the remaining available nutrients are metabolized by the microorganisms that are still present. For the duration of the

curing stage, therefore, microbial activity diminishes as

available nutrients are depleted. This is a relatively passive

process when compared to composting stage operations so

less intensive methods and operations are used here. In

general, materials that have completed the composting

stage are formed into piles or windrows and left until the

specified curing period has passed. Since curing piles undergo slow decomposition, care must be taken during this

period so that these piles do not become anaerobic. Curing piles should be small enough to permit adequate natural air exchange. A maximum pile height of 8 feet often is

suggested (Rynk et al., 1992). If compost is intended for

high-quality uses, curing piles should be limited to 6 feet

in height and 15 to 20 feet in width (Rynk et al., 1992).

Curing operations can be conducted on available sections

of the compost storage or processing area. In general, the

area needed for the curing process is one-quarter of the

size needed during the composting process. The curing

process should continue for a minimum of 1 month

(Rynk et al., 1992). A curing process of this duration will

allow decomposition of the composting materials to be

completed and soil-dwelling organisms to colonize the

compost. It is important to note, however, that curing is

not just a matter of time, it also depends on the favorability of conditions for the process to be completed.

Once the curing process is completed, the finished compost should not have an unpleasant odor. Incompletely

cured compost can cause odor problems. In addition,

compost that has not been cured completely can have a

high C:N ratio, which can tie up otherwise available nitrogen in the soil and be damaging when the compost is

used for certain horticultural applications since immature

compost can deprive plants of needed oxygen (Rynk et al.,

1992). The C:N ratio of finished compost should not be

greater than 20:1. C:N ratios that are too low can result in

phytotoxins (substances that are toxic to plants) being

emitted when composts are used. One group of phytotoxins is produced when excess nitrogen has not been utilized

by microorganisms. Nitrogen reactions ultimately can occur, causing the release of ammonia and other chemicals.

These chemicals “burn” plant roots and inhibit growth.

Therefore, proper end uses for incompletely cured composts are limited (see Chapters 8 and 9).

Odor Control

While odor might seem to be a superficial measure of a

composting Facility’s success, odor is potentially a serious

problem at all types of composting facilities and has been

responsible for more than one MSW composting plant

shutdown. In the planning stage of a facility, decisionmakers should examine composting conditions and odor

prevention and control approaches at existing facilities to

develop a control strategy for their operations. If nuisance

odors still develop, a facility will need to:

Identity the principal sources of odor.

Identify the intensity, frequency, characteristics,

and meteorological conditions associated with the

odors. A facility might consider establishing an

“odor standard” above which residents consider the

odor a nuisance. An odor panel, made up of community members who volunteer (or are chosen) to

represent the community’s level of acceptability,

can help judge the odor intensity and detectability

at their residences.

Develop limits for odor emissions on site based on

maximum allowable odors off site.

Measure odor release rates from suspected sources

for comparison with emission limits.

Select suitable controls for each source of odor.

Source.s of odors include various compounds that maybe

present in composted organic wastes (such as dimethyl disulfide, ammonia, and hydrogen sulfide). These odors

can be produced during different stages of the composting

process: conveying, mixing processing, curing, or storage.

Methods exist for measuring the quantity, intensity pervasiveness, emission rate, and transport of odors and for establishing odor standards. For example, odor quantity

can be expressed as the number of effective dilutions (ED)

required so that 50 percent of a panel of 10 people can

47
long enough to retrofit the plant and install engineering controls.

ms Facility managers should anticipate potential odor problems and incorporate ordor prevention and control methods from the start. The following are

amples of how complaints about odor can lead to setback or even failure: On Illlinos, a state law banning yard trimmings from

 failed when hastily built composting facilities produced unacceptable odor. The Illinois Composting Council was formed to address odor and

management issues. Neighbors of the St. Cloud, Minnesota, MSW composting facility complained about the odors emanating

ity, resulting in a year-long suspension of large-scale production while the facility constructed an enclosed system and engineered odor controls.

posting facility in Florida was forced to shut down, partly because of odor complaints. Neighbors would not allow the facility to remain in operation 

Processing Methods, Technologies, and Odor Control

still detect the odor; this quantity is known as the ED50.

Odor standards can be based on odor measurements (e.g.,

an ED10), the number of odor complaints, or an existing

legal standard. Data on relevant meteorological conditions, such as wind speed and direction, temperature, and

inversion conditions, often can be obtained from local

weather stations. For more information on methods of

measuring odors and setting odor standards, see Control of

composting Odors (Walker, 1993) and EPA’s Draft Guidelines for Controlling Sewage Sludge Composting Odors (U.S.

EPA, 1992).

The types of odor controls chosen depend on the odor

sources, the degree of odor reduction required, and the

characteristics of the compounds causing the odor. Odor

reduction efforts should incorporate both prevention and

control measures. In addition to the process and engineering controls described below, careful monitoring and control of the composring process will help avoid anaerobic

conditions and keep odors to a minimum. In-vessel composting tends to cause fewer odor problems, but in-vessel

systems still must be operated and monitored carefully.

Proper siting (discussed in Chapter 5) and effective public

involvement (see Chapter 10) also will help minimize

problems resulting from odors.

Process Controls

At facilities that compost yard trimmings, facility managers can implement a number of procedures to minimize

odors in the tipping and staging areas. Assuming that

grass is cut over the weekend, managers that have control

over the collection schedule can arrange for feedstock to

be delivered at the beginning of the week to minimize the

amount of time that grass is held in closed containers. If

grass coming to the facility is already odorous, it should

be mixed with a bulking agent (e.g., wood chips) as

quickly as possible so that the C:N ratio is approximately

30:1 (Glenn, 1990).

At facilities that compost yard trimmings and/or MSW

procedures that can help prevent or minimize odors include

Forming incoming materials into windrows

promptly.

Making sure windrows are small enough to ensure

that oxygen can penetrate from the outside and

guard against the formation of a foul-smelling anaerobic core but large enough for the interior to

reach optimal temperatures. For an aerated pile

composting system, the pile height should be limited to 9 feet high (Walker, 1993).

Providing aeration by completely mixing the feedstock and regularly turning the piles (see Engineering Controls below). Because turning can release

odors, however, a windsock can be used for

determining when conditions are right for turning

so as to keep odors from leaving the site.

Breaking down piles that are wet and odorous and

spreading them for drying. Mixing in dried compost that has been cured also can help.

Covering compost piles with a roof to help control

temperature and moisture levels.

Avoiding standing pools of water or pending

through proper grading and use of equipment (see

Chapters 5 and 6).

Engineering Controls

Facilities that compost yard trimmings typically rely on

regular turning of windrows to mitigate odors. Many

MSW composting facilities, however, are beginning to use

sophisticated odor control technologies to treat exhaust

gases from decomposing feedstock. Some facilities collect

and treat odorous gases from the tipping and composting

areas. Such systems are necessary if simpler odor control

measures are unsuccessful. Table 4-3 describes and compares the effectiveness of several odor control methods:

odor piles, biofilters, wet scrubbers, adsorption, dispersion

enhancement, and combustion. Combustion is effective

but can be expensive (Ellis, 1991). Biofilters and air scrubbers, however, are gaining acceptance as effective means

for odor control. These two methods are described below.

48
Odor Pile Odorous gases from compoting pile are diverted tp flow over finished compost. Questionable.

Wet Scrubbers packed tower Mist scrubbers Odorous compounds are absorbed into a liquid then extracted with chemicals. Up to 70 % per stage. < 90%.

Dispersion Enhancement Site modification Tall stack Facilitates greater dispersion of odorous gases. Moderate Potentially good. 

Processing Methods, Technologies, and Odor Control

Table 4-3. Effectiveness of composting odor control technologies.

Technology Description Effectiveness

Biofilter Controlled application of odor pile approach, incorporating filter 90%+ removal.

media to which microorganisms are attached.

Adsorption GaSSeS are passed aver an inert medium to which the odor-causing Effective for poIishing and

compounds attach, thereby “cleaning” the gases. control of volatile organic

compounds.

Combustion Gases are captured and odorous compounds burned. 99% removed.

Biofilers

Biofilters have been used to treat odorous compounds and

potential air pollutants in a variety of industries. The

composting industry is expanding its use of biofilters as

engineering design criteria for this technology have become increasingly available (Willams and Miller, 1992a).

In a biofiltration system, a blower or ventilation system

collects odorous gases and transports them to the biofilter.

The biofilter contains a filtration medium such as finished

compost, soil, or sand. The gases are evenly distributed

through the medium via a perforated piping system surrounded by gravel or a perforated aeration plenum (an enclosure in which the gas pressure is greater than that

outside the enclosure). The incoming gas stream is usually

moisturized to keep the filter medium from drying out

(Williams and Miller, 1992a).

As the gases filter up through the medium, odors are removed by biological, chemical, and physical processes.

Biofilters have an enormous microbial population. For example, soil biofilters contain 1 billion bacteria and

100,000 fungi per gram of soil. These microorganisms

oxidize carbon, nitrogen, and sulfur to nonodorous carbon dioxide, nitrogen, sulphate, and water before those

compounds can leave the filter medium (Bohn and Bohn,

1987). The biofilter medium acts as a nutrient supply for

microorganisms that biooxidize the biodegradable constituents of odorous gases. Biofilters also remove odorous

gases through two other mechanisms that occur simultaneously adsorption and absorption (Naylor et al., 1988;

Helmer, 1974). Adsorption is the process by which odorous gases, aerosols, and particulate accumulate onto the

surface of the faltering medium particles. Absorption is the

process by which odorous gases are dissolved into the

moist surface layer of the biofilter particles (Williams and

Miller, 1992a). As microorganisms oxidize the odorous

gases, adsorptive sites in the filtering medium became

available for additional odorous compounds in the gas

stream. This makes the process self-sustaining (Willams

and Miller, 1992a) and results in long-term odor removal.

Several different biofilter designs have been used in the

composting industry. Figure 4-14 illustrates open and enclosed biofilter systems. In an open system, the biofilter is

placed directly on the soil surface, or portions can be

placed below the soil grade. Typically an appropriate area

of soil is excavated, an aeration pipe distribution network

is placed in a bed of washed gravel, and the area is filled

with the filter medium. A closed system consists of a vessel constructed of concrete or similar material with a perforated block aeration plenum. The vessel is filled with

the biofilter materials.

The type of design chosen depends on the amount of land

available, climate, and financial resources. Both open and

closed systems can be covered to minimize the effects of

precipitation (Williarns and Miller, 1992a).

For successful odor control using biofilters, only a few design limitations must be kept in mind:

The vessel and the medium must be designed to ensure a suitable environment for microbial growth.

The moisture content in the biofilter must be optimal for the resident microorganisms to survive and

metabolize gases (Williams and Miller, 1992b). It

can be very challenging to maintain the proper

moisture conditions within the biofilter.

The biofilter medium must have a large reactive

surface area, yet be highly porous. These two characteristics tend to be mutually exclusive in naturally occurring soils and compost therefore, porous

material is often mixed with the soil or compost to

49
Compost Filter Bed (about 1 meter deep)

Foul Air

Processing Methods, Technologies, and Odor Control

Open Blofliter System

Ground

Note: Precipitation cover and sprinkler system can be added

-—— —

 Grave l

closed Biofliter System Exhaust Air

Water Sprinkler

to Moisten Air

Compost Filter Bed

Perforatad

Support

Plate

Heat Exchange

Steam injector

source: Williams and Miller, 1992a.

I

Drain

Figure 4-14. Bulk media fiber designs.

50
Methylformiate 35.0 g/kg media/ day Van Lith et al., 1990

Butylacetate 2.14 g/kg dry peat/ day 1 Ottengraf,1986.

N-butanol 2.40g/kg dry, compost/day. Helmer,1984.

Toluene 1.58g/kg dry peat/day.1 Ottengraf

Methanethiol 0.90g S/kg dry peak/day Cho et al., 1991.

Dimethylsulfide 0.30g S/kg dry peat/day. Cho et al., 1991. 

peat/day.

Processing Methods, Technologies and Odor Control

obtain a more suitable biofilter medium (Williams

and Miller, 1992a).

The filtration medium should have a significant

pH buffering capacity to prevent acidification from

the accumulation of sulfates.

Compaction of the medium over time should be

minimized.

Uniform air distribution should be designed into

the system. If the odorous gases are not distributed

evenly throughout the filter medium, “short circuiting” of exhaust gases and inadequate odor control

can result (Kissel et al., 1992; Williams and Miller,

1992a).

Table 4-4 presents the maximum removal capacities of

various compounds through biofilters. To effectively remove ammonia from composting exhaust gases, other removal technologies such as acid scrubbing (discussed

below) might be needed in addition to biofilters.

The initial cost of biofilters is usually less than the installation costs of other odor control methods, and the savings in operation and maintenance are even greater

because biofilters require no fuel or chemical input and

little maintenance (Bohn and Bohn, 1987). The initial

cost of biofilters is $8-10 per cubic foot of air passing

through the filter per minute (cfm).

Air Scrubbers

Air scrubbers use scrubbant solutions to remove odorous

compounds through absorption and oxidation. A variety

of air scrubbers exist. In packed tower systems, the scrubbant solution is divided into slow-moving films that flow

over a packing medium. The air stream being treated is

usually introduced at the bottom of the packing vessel

and flows upward through the medium (Lang and Jager,

1992). The scrubbant solution is recirculated to minimize

chemical usage (Ellis, 1991). In mist scrubber systems,

the scrubbant solution is atomized into very fine droplets

that are dispersed, in a contact chamber, throughout the

air stream being treated. Mist scrubbers use a single pass

approach: the chemical mist falls to the bottom of the

chamber and is continuously drained (Lang and Jager,

1992; Ellis, 1991).

Recent evidence suggests that multiple stages of scrubbers,

called multistage scrubbers, often with different chemical

solutions, are required to achieve adequate odor removal

effciency (Ellis, 1991). Figure 4-15 illustrates a multistage

odor-scrubbing system for a compost operation.

Research by the Washington Suburban Sanitary Commission at the Montgomery County Regional composting

Facility has identified dimethyl desulfide (DMDS) as the

primary odorant in air from the composting process

(Hentz et al., 1991). This research has led to the development of a three-stage scrubbing process shown to remove

97 percent of the odor in composting exhaust gases. This

process involves an acid/surfactant wash in the first stage

to remove ammonia and certain organics, a hypochlorite

oxidation stage to remove DMDS and other organic sulfides, and a final hydrogen peroxide wash to dechlorinate

and furher remove organics (Murray, 1991).

Multistage scrubbing systems require effective operation

and maintenance procedures to ensure optimum performance. Therefore, before selecting a multistage scrubbing

system for odor control, it is important to consider its

maintenance requirements in comparison to other odor

control technologies.

Postprocessing

Postprocessing is optional but normally is performed to

refine the compost product to meet end-use specifications

Table 4-4. Removal capacities of various compounds

through biofilters.

Maximum

Compound Removal Rat. Reference

Hydrogen Sulfide 5.0g s/kg dry Cho et al., 1991.

Butanol 2.41 /kg dry

peat/day.

Ethylacetate 2.03 /kg1dry

/

Ottengraf, 1986.

peat day.

Methanol 1.35 g/kg dry Van Lith et al., media/day.1

1990.

Dimethyl Disulfide 0.68 g S/kg dry Cho et al., 1991.

peat/cloy.

Ammonia 0.16g N/kg dry Shoda, 1991.

1Converted from g/m3/hr, assuming a media bulk density

of 40 lb/CF

Sources Williams and Miller, 1992a.

51
0.5- 1.0% Bleach Solution 3gpm (Atomizing Nozzles) Air Out Recirculation 50 gpm Fogging Nozzle) 

Water Bleach

Air in

Recirculation 60 gpm (fogging Nozzle)

2-3.0 % Sulfuric Acid Solution 3 gpm (Atomizing Nozzle)

0-1.0% Sulfuric Acid Solution 3 gpm (Atomizing Nozzle) Acid

Processing Methods, Technologies, and Odor Control

or market requirements. During postprocessing, compost

can be analyzed to ensure that stabilization is complete.

Compost also can be tested for chemical or pathogenic

contamination and tested to determine nutrient levels,

cleansed of unwanted material, sorted by size, screened,

size reduced, blended with other materials, stored, and/or

bagged.

Sorting and removal operations can be conducted to remove any remaining large particles that could lower the

quality of the compost or be aesthetically displeasing.

Sorting and removal also may be performed to generate

composts of uniform size for end uses where such uniformity is important (such as in horticultural applications). The same equipment can be used in both

preprocessing and postprocessing, but for composting operations with continual rather than seasonal inputs of

feedstock materials, dedicated equipment provides for a

more reliable and convenient systems flow. Where size reduction of finished compost particles is desired for aesthetic or marketing reasons, the use of simple shredding

mechanisms should suffice.

Proper storage is necessary to maintain the quaky of the

compost product. The most common storage problem is

inadequate drainage controls, causing the compost to become saturated. Overly wet compost can become malodorous and is heavy and difficult to handle. Provision for

adequate drainage is essential when storing compost. In

general, the storage area should be large enough to hold

25 percent of the compost produced by the facility each

year as well as a large supply of bulking agent, if needed

(Alexander, 1990).

During postprocessing, compost that will be used as soil

amendment should be tested to ensure that it has been

properly cured. Compost stability can be assessed by seed

germination tests or by analyzing factors that indicate the

level of compost maturity. In seed germination tests, sensitive plant species are planted in the compost and in a

soil medium. Germination rates for the plants grown in

the compost are compared to those grown in the soil and,

if the rates are comparable, they show that the compost

has been properly stabilized. Laboratory analyses of important compost parameters such as oxygen consumption,

Stage I Stage Stage II

Ammonia Removal

I

Oxidation with Final wash

I

I

-

Source: Goldstein, 1989.

I

Figure 4-15. Process odor-scrubbing system for compost operation.

52
Processing Methods, Technologies, and Odor Control

carbon dioxde production, C:N ratios, and cation exchange capacity also can be conducted (see Chapter 9).

Laboratory analyses also ears be conducted to determine if

phytotoxic or pathogenic contaminants are present in the

compost. Nutrient levels can be determined through

laboratory tests as well. Several states and localities have

imposed compost quality requirements (see Chapter 7’),

and laboratory analysis is often needed to ensure that

these requirements are met.

Once contaminant and nutrient levels have been determined, results can be incorporated into compost labels.

This will allow end users to obtain composts with

contaminant and nutrient levels that fall within ranges acceptable to their specific needs. Labels also can include information on the types of feedstocks used for composting,

weight or volume of container contents, suggested uses for

the compost, appropriate application rate, warnings or restrictions on compost use, and the name and address of

the compost producer.

Finally compost can be bagged before it is distributed if it

is economically feasible. Bagging facilitates transporting,

marketing, and labeling of compost. Because it is relatively labor intensive (and therefore costly), however, bagging should be conducted only if buyers for the compost

have been secured and the cost of bagging can be justified

by an increase in expected revenues.

Summary

T

here are three stages in the composting process:

preprocessing, processing and postprocessing.

Different method, operations, and and equipment

are associated with each of these stages. Th e level of 

effort applied at each stage depends on the desired

quality of the final product, the type and amount of

feedstock, the speed at which the process must be completed the emphasis placed on odor and leachate control, the resources available, and the level of effort

applied at the other composting stages. An understanding of the range of methods and operations that

can be used during compost processing will facilitate

planning and development as well as maintenance

and improvement. composting facility managers aslo

must consider the potential for odor problems when

designing processing operations. Odor is a potentially

serious problem that has led to the closure of several

composting facilities in recent years. Many steps can

be taken, however to address odor formation before

it becomes a public nuisance.

Chapter Four Resources

Alexander, R 1990. Expanding compost markets. BioCycle. August, 31(8):54-59.

Appelhof, M., and J. McNelly. 1988. Yard waste composting guide. Lansing, MI: Michigan Department of Natural

Resources.

Bohn, H. L., and R. K. Bohn. 1987. Biofiltration of odors

from food and waste processing. As cited in Proceedings

of Food Processing Waste Conference, Georgia Technological Research Institute, Sept. 1-2, 1987.

Buckner, S.C. 1991. High volume yard waste composting.

BioCycle. April, 32(4):48-49.

Cal Recovery Systems (CRS) and M.M. Dillon Limited.

1989. composting A literature study. Ontario, Canada:

Queen’s Printer of Ontario.

composting Council (CC). 1991. Compost facility planning guide. Washington, DC: composting Council.

Ellis, S. 1991. Air pollution and odor control methods.

Proceedings of the Northeast Regional Solid Wrote Comporting Conference, June 1991. Washington, DC: Comporting Council. pp. 23-26.

Glaub, J., L. Diaz, and G. Savage. 1989. Preparing MSW

for composting. The BioCycle Guide to composting Municipal Wastes. Emmaus, PA: The JG Press.

Glenn, J. 1990. Odor control in yard waste composting.

BioCycle. November, 3 1(11):38-40.

Glenn, J. 1991. Upfront processing at MSW composting

facilities. BioCycle. November, 32(11):30-33.

Goldstein, N. 1989. New insights into odor control. BioCycle. February, (30)2:58-61.

Golob, B. R., R. Spencer, and M. Selby. 1991. Design elements for solid waste composting. BioCycle. July,

32(7):50-53.

Golueke, C.G. 1977. Biological reclamation of solid

wastes. Emmaus, PA: Rodale Press.

Gray, K.R., K. Sherman, and A.J. Biddlestone. 1971a. A review

of composting Part 1- Process Biochemistry 6(6): 32-36.

Gray, K.R., K. Sherman, and A.J. Biddlestone, 1971b. A

review of composting: Part 2 - Process Biochemistry

6(10): 22-28.

Gray, K.R., and A.J. Biddlestone. 1974. Decomposition

of urban waste. As cited in: Richard, 1992. Municipal

solid waste composting: Physical and biological processing. Biomass & Bioenergy. Tarrytown, NY: Pergamon

Press. 3(3-4): 195-211.

53
I

Processing Methods, Technologies, and Odor Control

Processing Yard Waste

T

he Town of Islip, New York has been operating a large-scale yard trimmings composting facility on a 40-acre site since ‘

1988. Approximately 60,000 tons of grass leaves, and wood debris is collected from town residents, municipal agencies, and commercial landscapers every year and transported via packer trucks to the facility.

Isip’s composting facility comprises preprocessing, processing, and postprocessing operations. During the preprocessing ;:

stage, a shredder debags the composting feedstock and size reduces larger materials. This machine is capable of processing

25 tons of yard waste per hour. Once shredded, the feedstock is conveyed to a trommel screen where it is sorted and aerared. A high percentage of plastic is removed during this preprocessing stage. Once size reduced and screened, moisture is

added to the feedstock to obtain an initial moisture content of 50 percent.

During processing, the feedstock is transported via dump trucks to the composting area, where it is formed into windrows

on a woodchip base. This base absorbs leachate, increases porosity, and improves drainage conditions at the bottom of the

windrows. Twenty-five acres of the facility has been sited for windrow formation. The size of the windrow formed depends

upon the nature of the feedstock material and the time of year composting takes place. Feedstock containing mostly leaves

can be formed into windrows 12 feet high by 26 feet wide. The size of the windrow formed from feedstock containing

predominancy grass depends on the bulking material used, however, these are generally no larger than 6 feet high by 14

feet wide. To maintain aerobic composting conditions, smaller windrows are turned with a rotary-drum turning machine,

while a front-end loader is used to turn larger windrows. The frequency of turning varies depending on the windrow size,

feedstock composition, stage of decomposition, and moisture content and is adjusted so that aerobic conditions are

maintained.

Leaves usual1y remain in windrows for at least 16 weeks before being placed in curing piles for further stabilization. Grass

remains in windrows from 6 to 8 weeks before being placed in curing piles where it will stay for another 4 to 6 weeks, The

facility ensures continual processing of fresh material delivered to the site by closely controlling the decomposition rate

and windrow size.

Once cured, postprocessing takes place to produce the final product. This involves screening the material to remove woodchips and any plastic fractions remaining in the compost. An air classifier is to be added to the system to separate the plastic from the woodchips so that the chips can be recycled back to the windrows.

The finished compost is available to residents of Islip free of charge and can be purchased by landscape contractors, turf

growers, topsoil suppliers, and nurseries for $6 per yard (Buckner, 1991).

Source: Buckner, 1991.

Helmer, R 1974. Desodorierung von geruchsbeladener

abuft in bodenfiltern. Gesundheits-Ingenieur. 95(1):21.

As cited in: Williams and Miller, 1992a. Odor control using biofilters, Part I. BioCycle. October, 33(10):72-77.

Hentz, L. H., C.M. Murray, J.L. Thompson, L. Gasner,

and J.B. Dunson. 1991. Odor control research at the

Montgomery County regional composting facility. Water

Pollution Control Federal Journal v. 26, Nov/Dec. As

cited in: Murray, 1991. Controlling odor. Proceedings of

the 1990 Solid Waste composting Council Conference,

November 1990. Washington, DC: composting Council.

pp. 93-96.

Illinois Department of Energy and Natural Resources

(IDENR). 1989. Management strategies for landscape

waste. Springfield, IL Office of Solid Waste and Renewable Resources.

Kissel, J.C., C.H. Henry, and R.B. Harrison. 1992. Potential emissions of volatile and odorous organic compounds from municipal solid waste composting facilities.

54

Biomass & Bioenergy. Tarytown, NY: Pergamon Press.

3(3-4):181-194.

Lang, M. E., and R.A. Jager. 1992. Odor control for municipal sludge composting. Biocycle. August, 33(8):76-85.

Murray C.M. 1991. controlling odor. Proceedings of the

1990 Solid Waste composting Council Conference, November 1990. Washington, DC: composting Council. pp.

93-96.

Naylor, L.M., G.A. Kuter, and P.J. Gormsen. 1988. Biofilters for odor control: the scientific basis. Compost Facts.

Hampton, NH: International Process Systems, Inc.

Richard, T., N. Dickson, and S. Rowland. 1990. Yard

waste management: A planning guide for New York State.

Albany NY: New York State Energy Research and Develop

ment Authority, Cornell Cooperative Extension, and New

York State Department of Environmental Conservation.

Richard, T.L. 1992. Municipal solid waste composting

Physical and biological processing. Biomass & Bioenergy.

Tarrytown, NY: Pergamon Press. 3(3-4):195-211.
Processing Methods, Technologies, and Odor Contro l

Composting Municipal Solid Waste Using Enclosed Aerated Windrows

T

he MSW composting facility in Wright County, Minnesota has been operational since 1991. This facility processes approximately 165 tons per day (TPD) of MSW and its composting, curing, and storage areas are sized m accommodate

up to 205 TPD. Incoming MSW is weighed and discharged onto the concrete tipping floor of the receiving area

 where some hand separation of recyclables occurs. The receiving area has a storage capacity of approximately 330 tons.

 The preprocessing operations at the facility include screening handsorting, size reduction, and mechanical sorting. The ‘

composting feedstock is transferred from the receiving building to a preprocessing building where it is discharged into a

trommel screen equipped with knives to facilitate bag opening. Two conveyors transfer the screened material to the handsorting area. One conveyor transports the fines that pass through the screen openings, and the other transports oversized

materials. During this stage, handsorting personnel remove recyclables such as high-density polyethylene and polyethylene

terephthalate plastics and aluminum arts. Once handsorted, the feedstock is size reduced by a hammermill located in an

explosion-proof enclosure with explosion venting. Following this, the shredded feedstock passes underneath an overhead

electromagnet to remove ferrous metals.

At this stage the feedstock material is discharged into a mixing drum and water is added to raise the moisture content to 

an optimal level. The purpose of the mixing drum is to adjust the moisture content, homogenize the waste stream, and

screen oversized and nondegradable material that would inhibit downstream process steps. Three separate feedstock

streams are generated by this operation. Material less than 2 inches in size is transported to thecomposting area, material

greater than 2 inches but less than 8 inches undergoes additional shredding and screening, and material greater than 8

inches is disposed of in a sanitary landfill.

Composting takes place in an open-sided covered hangar, sired to contain 12 windrows. Feedstock material is placed in

one of two primary windrows formed in the middle of the hangar by a central belt conveyor equipped with a traveling

tripper and cross belt conveyor assembly. When one primary windrow has been formed, a windrow turning machine will

move through the pile and reposition it to the second row, and from there to the third row, and so on. An aeration system

draws air through the primary and secondary windrows. The exhaust air passes through a biofilter for odor control (see

Section 6). The facility has an extensive leachate collection system.

The composting feedstock remains in the composting area for approximately 60 days after which it is transferred to a

hammermill for further size reduction. A screening drum is then used to separate nondegraded materials from this material. The finished compost is stored on an asphalt pad.

Source: Golob et al., 1991.

Rynk, R., et al. 1992. On-farm composting handbook.

Ithaca, NY: Cooperative Extension, Northeast Regional

Agricultural Engineering Service.

Strom, P.F., and M.S. Finstein. 1989. Leaf composting

manual for New Jersey municipalities. New Brunswick,

NJ: Rutgers State University.

University of Connecticut Cooperative Extension Service

(UConn CES). 1989. Leaf composting: A guide for

municipalities. Hartford, CT: State of Connecticut Department of Environmental Protection, Local Assistance

and Program Coordination Unit, Recycling Program.

Walker, J.M. 1993. Control of composting odors. In: Science and engineering of composting. Hoitink and Keener,

eds. Worthington, OH: Renaissance Publications.

Williams T.O., and F.C. Miller. 1992a. Odor control using biofilters, Part I. BioCycle. October, 33(10):72-77.

Williams T.O., and F.C. Miller. 1992b. Biofilters and facility operations, Part II. BioCycle. November, 33(11):

75-78.

Wirth, R 1989. Introduction to composting. St. Paul,

MN: Minnesota Pollution Control Agency.

U.S. EPA. 1992. Draft guidelines for controlling sewage

sludge composing odors. Office of WasteWater Enforcement and Compliance, Washington, DC.

55
Chapter Five

Facility Siting and

Design

P

roper siting and design are prerequisites to establishing safe and effective composting facilities. Decisionmakers should take care in selecting a suitable site and developing an appropriate design so as to control

both construction costs and operational probems over the life of the facility This chapter describes factors

that should be considered when siting and designing facilities for the composting ofMSWor yard trimmings. In

general the primary issues to consider involve odor control (see Chapter 4) and bioaerosol concerns (ice Chapter

6). While both types of facilities have similar siting and design requirements, more stringent measures are typically needed at MSW composting facilities. Throughout the siting and design process, it is crucial that the needs

of the community be accommodated since public acceptance of a facility is key to its success. Local and state

requirements aso should be reviewed prior to siting and designing composting facilities. Many states have established specific criteria that composting facilities must address during siting and design. The criteria address many

technical concerns, including those rekzted to protecting human health and the environment, and can have an

impact on facility location, land use, size, and other considerations. In general detailed engineering plans typically must be approved by the state environmental protection agency in order to obtain a permit to construct and

operate a MS W compost facility (Chapter 7 discusses state legislation including the specific siting, design, and

permitting requirements of several states.)

Siting

Finding a suitable location for a composting facility will

help a community achieve its composting goals while

avoiding a variety of complications that could slow the

composting process. A number of technical, social,

economic, and political factors will shape decisions on

locating a facility. Some of the major factors in facility

siting include:

■

■

■

■

Convenient location to minimize hauling distances.

Assurance of an adequate buffer between the facility and nearby residents.

Suitable site topography and soil characteristics.

Sufficient land area for the volume and type of material to be processed.

These factors are described in more detail below. Figure 5-

1 presents a site assessment form used in New York State

for the composting of yard trimmings. This form is

56

designed to obtain an objective assessment of proposed

sites for facilities that compost yard trimmings. Various

factors affecting siting are rated from 1 to 5, with 1 being least desirable and 5 being most desirable. These

ratings are then added to give a total rating for each

site. This rating evaluation makes it easier to choose the

most appropriate site for a facility that composts yard

trimmings. The same form also could be used for a

MSW composting facility.

Location

Potentially suitable locations for composting facilities

include areas adjacent to recycling drop-off centers and

in the buffer areas of existing or closed landfills, transfer

stations, and wastewater treatment plants. Current Federal Aviation Administration (FAA) guidelines prohibit

siting any type of solid waste facility, including composting facilities, within 10,000 feet (almost 2 miles) of

an airport. This is to prevent birds, which could be attracted to the site by potential food sources, from interfering with airplanes.
Facility Siting and Design

Site Name Date of Inspection

Site Location Description Inspected by:

This form is designed for use in the field, to obtain an objective assessment of the proposed site.

The various “factors” considered at each site receive a rating from 1 to 5, with 1 being least desirable

and 5 being most desirable.

FACTORS

1.

2.

3.

4.

5.

6.

7.

Site Preparation Costs

a) compost area development

b) access road construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

c) security set-up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Site Characteristics

a)

b)

c)

d)

e)

soil characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

proximity to water; streams, lakes . . . . . . . . . . . . . . . . .

Slope and topography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

acreage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Access by Public Roads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Infrastructure

a)

b)

c)

d)

e)

f)

water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

existing access road . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

storage

telephone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

electric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Proximity to Homes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Proximity to Town in Need . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Regional Site Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 5-1. Yard trimmings site assessment form.

5 7
Facility Siting and Design

1-

Figure 5-1. (Continued).

A centrally located facility close to the source of the compost

feedstock will maximize efficiency and convenience while reducing expeses associated with hauling these materials and

distributing the finished compost product. Siting a facility

that can be accessed via paved, uncrowded roads through

nonresidential areas will further contain transportation expenses. If necessary, however, a busy local road network

can be compensated for by scheduling feedstock and compost product deliveries during off-peak road use times, A

centrally located facility can offer a further advantage to

communities operating drop-off collections since convenient siting often encourages greater resident participation

in such programs.

FACTORS COMMENT

8. Land Ownership

9. Environmental Impact

a) tree removal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

b) habitat disturbance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10. Impact on Current Use

a) visual

b) physical. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

11. Impact on Future Use

a) visual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

b) Physical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12. DEC Criteria (minimum distances)

a) property line, 50 ft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

b) residence or business, 200 ft . . . . . . . . . . . . . . . . . . . . . . . .

c) potable water well, 200 ft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

d) surface water supply, 200 ft. . . . . . . . . . . . . . . . . . . . . . . . . . .

e) drainage swale, 25 ft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

f) water table, 24 inches . . . . . . . . . . . . . . . . . . . . . . . . . . . ...*.....

TOTAL RATING . . . . . .

General comments relative to suitability of site to serve as a municipal composting facility:

Source: Richard et al., 1990.

Often, however, the concerns of local residents (particularly about potential odors) force a composting facility to

be sited away from ideal collection and distribution locations. This is especially true for MSW composting facilities. Locating a site with an extensive natural buffer zone,

planted with trees and shrubs, is an effective way to reduce the potential impacts that a new composting facility

might have on the surrounding neighborhoods. If natural

buffers do not exist, artificial buffer zones might need to

be constructed. visual screens, such as berms or landscaping, can be designed to protect the aesthetic integrity of

the surrounding neighborhoods. (Buffer zones are discussed in more detail later in this chapter.)

58
Odor Evaluation

Facility Siting and Design

A

most important consideration in the siting and

design of a composting facility is the potential for

odors and for odor transport to the community.

When planning a facility, it is important to predict potential sources of odors along with their emission rates,

detectability, and intensity. This information can be obtained from Literature studies and visits to other composting sites. In order to predict how these odors will

be transported, information on meteorological conditions (e.g., wind speed and direction, temperature, and

inversion conditions) in the vicinity of the site can be

obtained from a local weather station. This information then can be used to conduct dispersion modeling

to predict how odors could be transported into the

community and how potentially bad they will smell.

Data from the modeling can assist decision-makers in

choosing a suitable site and in selecting a composting

system whose design will help minimize odors (Wa1ker,

1992). (See Chapter 4 for a more in-depth discussion

of odor control and management.)

Topography

Potential sites should be evaluated in regard to the

amount of alteration that the topography requires. Some

clearing and will be necssary for proper composting,

but minimizing this work is desirable in order to reduce

expenses and maintain trees on the perimeter of the site,

which act as a buffer. A composting site should be appropriately graded to avoid standing pools of water and runoff. To avoid pending and erosion, the land slope at a

composting site should be at least 1 percent and ideally 2

to 4 percent (Rynk et al., 1992). U.S. Geological Survey

topographic maps and a plot plan survey can provide information on the natural drainage characteristics of a site.

The type and structure of the soil present at the site

should be assessed to control run-on and runoff. If the site

is unpaved, the soil on the site should be permeable

enough to ensure that excess water is absorbed during periods of heavy precipitation and that the upper layers of

the soil do not become waterlogged (this can create pooling and limit vehicular access). If the soil is impermeable

or the site is paved, a range of drainage devices can be

used to divert precipitation away from the composting

pad and storage areas (see Chapter 6 for more information

on these devices).

Proximity to certain water sources also must be considered. Floodplains, wetlands, surface watters, and ground

water all need to be shielded from runoff or leachate that

can originate at the site. The height of the water table is a

crucial factor in protecting these water sources. The water

table is the upper surface of the “zone of saturation,”

which is defined as the area where all available spaces or

cracks in the soil and rock are filled with water. In general,

the water table should be no higher than 24 inches below

the soil surface. Otherwise, flooding can occur during

times of heavy precipitation, which can potentially wash

away windrows and carry compostable materials off site.

Pooling also can result, slowing composting significantly

(Richard et al., 1990). In addition, leachate from composting operations is more likely to contaminate ground

water when there is less soil to naturally falter the leachate

as it seeps downward (Richard, 1990).

Some states have stringent regulations concerning the protection of ground water at a composting site (see Chapter

7). The state of Illinois does not allow the placement of

compost within 5 feet of the high water table North

Carolina requires composting pads and storage areas to be

at least 2 feet above the seasonal high water table and

Pennsylvania does not allow a composting facility to be

sited in an area where the seasonal high water table is less

than 4 feet from the surface (WDOE and EPA, 1991).

Flood hazard maps, available from local soil conservation

offices, can help show the hydrologic history of a site. In

addition, municipalities should research the guidelines

that apply in their area as many states have regulations restricting composting operations on floodplains or wetlands. In areas where no local or state regulations exist,

Section 404 of the Clean Water Act, administered by the

U.S. Army Corps of Engineers, regulates siting issues in

proximity to wetlands.

The composting site should have a water source for properly controlling the moisture content of the composting

process. The amount and source of the water to be supplied depends on the nature of the compostables, the

composting technology used, the size of the operation,

and the climate. For example, dry leaves generally require

20 gallons of water per cubic yard of leaves (Richard et al.,

1990). Feedstocks with high moisture content (e.g., food

scraps) will require less water (see Chapter 2).

Onsite water sources are needed for composting that requires substantial water use. Possible sources include city

water hookups, stormwater retention facilities, and wells

or surface pumping from nearby lakes or streams. For

smaller sites or those requiring minimal amounts of water,

mobile water sources can be used. Potential sites should be

able to accommodate both the present and future water

requirements of the composting program.

Land Area Requirements

To operate efficiently, a composting facility must allot

sufficient space to the preprocessing, processing, and

postprocessing compost stages as well as to the

surrounding buffer zone. Typically, the bulk of the site

will be occupied by the composting pad and the buffer

zone. (The size of the composting pad and buffer zone

5 9
Facility Siting and Design

-

are discussed in more detail later in this chapter.) Administrative operations and equipment also need to be housed

on site and should be planned for when determining land

area requirements for the facility.

Communities should be careful not to locate a facility on

too small a site as this can decrease plant efficiency and increase operational costs. The land area of a composting ficility must be large enough to handle both present and

future projected volumes. Ideally a composting facility

should have, at a minimum, enough acreage to accommodate an entire year’s projected volume of incoming feedstock on the site (Richard et al., 1990).

Other Factors Affecting Siting Decisions

Municipalities must consider a number of other factors

when siting a composting facility. These factors include

The existing infrastructure - The presence of

existing utiliy hookups, storage space, and paved

access roads could significantly reduce costs of site

preparation.

Zoning issues - Themconstruction of composting facilities is permitted only on certain tracts of land within

a community as dictated by local zoning laws.

Site ownership - Potential sites could be owned by a

public or private entity ownership will affect cost

and control of the composting facility.

Nearby land uses - Sites near schools or residential

areas could provoke objections from citizens concerned about potential odor or noise.

Design

Once a site has been identified, a facility must be designed

to meet the community’s composting needs. It is a good

idea to visit other composting facilities to view different

designs and operations first-hand. (Figures 5-2 and 5-3 illustrate sample composting site designs.) When developing the initial facility design, future expansion possibilities

should be considered in the configuration. Different

scenarios should be developed to account for feedstock

type and volume changes, facility modifications, system

alterations, and other potential revisions in facility design

or capability (CC, 1991).

The following are critical to the design of a facility

Preprocessing area

Processing area

Postprocessing area

Buffer zone

Access and onsite roads

Site facilities and security

Preprocessing Area

A preprocessing or staging area offers room to receive collected feedstock and sort or separate materials as needed.

Receiving materials in a preprocessing area will eliminate

the need for delivery trucks to unload directly into windrows in poor weather conditions. The size and design of

the preprocessing area depends on the amount of incoming materials and the way the materials are collected and

sorted (see Chapters 3 and 4). Some facilities also find it

advantageous to use a staging area to store separated materials and to wet and hold the materials briefly to prepare

them for windrow formation.

The tipping area (the part of the preprocessing area where

incoming feedstocks are unloaded) is often roofed in areas

subject to severe weather conditions. The floor should be

strong enough to support collection vehicles and

hardened to withstand the scraping of equipment such as

front-end loaders. The tipping floor also should contain

no pits, which can attract vermin. Concrete floor slabs

and pushwalls to run the front-end loaders against when

scooping MSW will increase the efficiency of the operation. The minimum ceiling height of an enclosed tipping

area depends on the clearances that the various types of

hauling vehicles require to discharge their MSW The tipping floor area should allow a minimum maneuvering distance of no less than one-and-a-half times the length of

the delivery vehicle.

The preprocessing area is also frequently used to shred the

. . . . . . . . . compostable material or separate the bags in which the

feedstock has been collected. The size of this area depends

on the volume of material that the site handles and the sophistication of the system design. For example, the required floor area for a simple system consisting of infeed

and discharge conveyors, a single shredder, and a trommel

is approximately one-half of that required for a more

complex system that also includes vibratory screens, a

preshredding flail mill, and postprocessing equipment. A

composting site that will sort out recyclable from the

MSW received will require additional space and containers for holding these materials.

Some composting facilities use a truck weigh scale to keep

track of the weight of feedstock being hauled into the facility

as well as the amount of finished compost produced and distributed. Weigh scales of varying lengths can be purchased to

accommodate large vehicles. Designed to operate under a

variety of weather conditions, they often are located outdoors on the entrance roadway. A scale should be used unless

the composting operation is very small.

Processing Area

The processing area, composed of the composting pad

and the curing area, must be carefuly designed for effi

cient composting. Design specifications for this area will
Staging Area Windrows Gate Trailer 40 x 60 Building Finished Product Screen Area Curing Area

Trees and a berm can provide a visual and sound barrier Property Line well Residence or Business 

Facility Siting and Design

BUFFE R ZON E

Source: Appelhof and McNelly, 1988.

Figure 5-2. Generic compost site layout.

T 200 ft. 200 ft.

(not to scale)

Direction of slope

Source: Richard et al., 1990.

Figure 5-3. Compost facility site layout.
Facility Siting and Design

differ considerably depending on whether the composting

facility processes yard trimming or MSW feedstocks.

The composting pad surface in a yard trimmings composting facility does not have to be paved; however, it

must be firm and absorbent enough to prevent pending

around the windrows or erosion from runoff. Grading the

surface of the pad to meet the optimal slope also will help

prevent erosion by allowing for gentle drainage. Maintenance of the composting site should include annual regrading to preserve this slope. As a further protection

against erosion, windrows should be arranged parallel to

the grade to allow runoff to flow between the piles instead

of through them (Richard et al., 1990; Mielke et al.,

1989). Precipitation moving onto the composting pads

can be diverted from compost piles through the use of

drains and conduits. Adequate drainage at composing

facilities is essential. Poor site drainage leads to pending of

water, saturated composting materials, muddy and unsightly

site conditions, bad odors, and excessive runoff and leachate

from the site (Rynk et al., 1992).

Some states have additional requirements for the processing area. For example, to minimize leachate from migrating into subsurface soils, ground water, or surface water,

Minnesota requires MSW composting operations to be

placed on liners made of synthetic materials, such as high

density polyethylene plastics, or natural soils, such as clay.

Soil liners must beat least 2 feet thick and compacted to

achieve a permeability of no greater than 1 x 10-7 centimeters per second (WDOE and EPA, 1991). Minnesota

regulations also require that MSW composting facilities

be designed to collect and treat leachate. The preferred

method is to collect, pump, and haul the leachate to the

municipal wastewater treatment plant if the plant accepts

the leachate. Iowa regulations require composting facilities

to use an impervious composting pad with a permeability

coefficient of 1 x 10-7 centimeters per second (WDOE

and EPA, 199 1). Florida regulations require MSW composting facilities to conduct their composing operations

on surfaces such as concrete and asphalt. They also require

a leachate collection system. Municipalities should check

with their state to be sure composting pad designs comply

with existing guidelines (see Chapter 7).

The size of the composting pad depends primarily on the

amount of material that the facility receives for composting and the level of technology that will be used. The required area also depends on the characteristics of the

feedstock; the initial and final density of the composting

material and the moisture content will affect the amount

of material that will fit on the pad. The windrow turning

equipment influences aisle width, which in turn influences the size of the composting pad (see Chapter 4). A

common design is to line the windrows in pairs 5 feet

apart with 15-foot aisles between each pair. This method

uses space efficiently but is only possible when straddletype turning equipment is available (Mielke et al., 1989).

62

Operations that use a front-end loader to turn the material require individual rows and aisles between the windrows of 15 to 20 feet. Some composting pad areas are

housed under structures with movable side walls. In dry

climates, where water is scarce or expensive, a roof over

the composting area reduces evaporation and process

water requirements. In areas of high precipitation, a roof

prevents overly wet compost and anaerobic conditions

from developing. In regions that experience severe winters, all or part of the composting area can be located

within a heated or insulated building to avoid arresting

the biological process due to freezing. Because the composting process requires the use of moisture and enclosed

composting operations can create extremely damp conditions, wood structures are not recommended unless they

are well treated to withstand high moisture levels.

Proper ventilation is required in enclosed preprocessing and

processing areas because the air within the structure can be a

source of bioaerosols, odors, dust, and excess moisture. Air

filters can be used to clean the exhaust air. Biofilters can be

used to absorb odor-producing compounds (see Chapter 4).

Adequate vents situated over preprocessing equipment can

reduce dust and odors, and fires can be used to help disperse

nonpervasive odors in the facility

A curing and also should be part of the design of the

processing site. This area is used to hold the compost for

the last phase of the composting process, to allow the material to stabilize and mol. The space requirement for curing is based upon the amount of organic material

composted, the pile height and spacing and the length of

time that the compost is cured (Rynk et al., 1992). Locating this operation is less problematic than finding a suitable site for the composting pad provided that the

composting process has been carried out properly. If this is

the ease, the material should be fairly stable and many of the

runoff, ground-water contamination, and other siting concerns are mitigated. In addition, the curing area needs less

space, requiring only about one quarter of the area of the

compost pad (Richard et al., 1990 UConn CES, 1989).

Postprocessing Area

A postprocessing area at composting facilities can be used

to conduct quality control testing of compost to perform

screening, size reduction, and blending operations; to

compost in preparation for market; and to store the compost. A space about one- fifth the area of the composting

pad is sufficient (Richard et al., 1990).

If the finished compost will not be delivered to the end

user within a relatively short period of time, the compost

should be covered. Otherwise, winds can transport weed

seeds into the piles, which can support the growth of unwanted plants and devalue the product. Backup storage

and disposal capacity also should be planned for seasonal

markets. Cured compost should be stored away from surface water and drainage paths. A storage capacity of at
Navigable lake or pond 1,000 feet

State, federal, or interstate highway or public pard boundary 1,000 feet

Public or orivate water supply well 1,200 feet

Facility Siting and Design

least 3 months should be incorporated into site designs

for composting Facilities. Cured compost, which is a

source of odors in some meteorological conditions, might

be better stored away from the site.

Buffer Zone

The buffer zone frequently needs to be several times the

size of the composting pad, particularly when the composting operation is adjacent to residential areas or businesses. Enclosed or higher technology facilities might

require less of a buffer zone, since many of the operations

are by design closely controlled and contained.

During site design, the direction of the prevailing wind (if

one exists) should be noted and the buffer zone extended

in this direction. This will help minimize the transport of

odor and bioaerosols downwind of the facility Figure 5-4

shows a sample buffer zone design.

In general, the larger the buffer zone, the greater the acceptance of the facility among residents. The buffer zone

required by a composting facility depends largely on the

type of feedstock being composted and the level of technology (in terms of monitoring and odor control) employed at the facility. State and local regulations frequently

require minimal buffer zone sizes or specify the distances

that composting operations must be from property lines,

residences, or adjacent businesses and from surface water

or water supplies (see Chapter 7).

New Jersey regulations recommend a buffer zone for leaf

composting facilities of 150 feet (high-level technology,

less than one-year cycle) to 1,000 feet (minimal technology, two- to three-year cycles) (WDOE and EPA, 1991).

Buffer zone recommendations are wider in New Jersey

(from 150 to 1,500 feet) when grass is included in the

composting feedstock because of the greater potential for

odors. Iowa regulations require MSW composting facilities to be located at least 500 feet from any habitable residence. Table 5-1 lists the minimal separation distances

allowed by the State of Wisconsin for facilities that compost yard trimmings or MSW.

Municipalities should check state and local regulations to

be sure all applicable guidelines are being incorporated

into their buffer zone design. Because odor problems can

force a multimillion dollar facility to shut down, communities might extend composting buffer zones beyond the

minimum required. (Other steps to control odors are discussed in Chapter 4.)

Access and Onsite Roads

The type and amount of traffic into and out of a facility should be considered in the design process. Traffic at

a site is largely dependent on the volume of materials

that flows through the facility and the type of collection

system in place. For example, operations that compost

municipal yard trimmings will involve intensive use of

Note: Depending on site constraints such as property

lines, buildings and surface water, available

acreage for composting will Vary. Area loss

could be significant.

Source UConn CES, 1989.

Figure 5-4. Site setback distances.

the roads during periods of peak collections. MSW com

posting operation, on the other hand, will usually receive a

more consistent schedule of deliveries. Although an extensive

onsite road network usually is not necessary, there should be

permanent roads leading to the tipping and storage areas.

These access roads should be graveled or paved to handle

large vehicles during adverse weather conditions. This surfacing is expensive, however, and the resulting run-on and runoff must be managed to prevent erosion.

If drop-off collections will occur at the facility, the design

should accommodate a greater flow of automobile and

light truck traffic. A circular traffic flow can accommodate

rapid deliveries, effectively reducing congestion. A

Table 5-1. Setback requirements for Wisconsin

composting facilities.

Navigable river or stream 300 feet

Airport runway 1,000 feet

Source: WDOE and EPA, 1991.

63
Facility Siting and Design

separate access road to the tipping area also can be constructed for these vehicles (Richard et al., 1990, Strom and

Finstein, 1989). Ideally the road used by the public to deliver materials or to pick up finished compost should be different from the heavy equipment access road. Roads should

also be designed to provide adequate turning and dumping

areas to accommodate delivery by all types of vehicles.

Site Facilities and Security

composting operations might require one or more buildings to house various site functions, from maintenance

and administrative work to personnel facilities. This is

true even for smaller operations such as sites that compost

yard trimmings, which might need only a small receiving

post. Site buildings should have, at a minimum, electricity, heat, air conditioning a toilet, and drinking water. All

facilities should have a telephone or radio in case of emergencies. In larger facilities (sites with a daily capacity

greater than 50 tons), a personnel area containing an office, shower, locker room, and lunch room might be appropriate. A maintenance area that includes a workshop

and storage rooms to keep parts and other maintenance

materials also might be needed.

Access to the site must be controlled to prevent vandalism, especially arson, and illegal dumping. At a minimum, the access roads must be secured with a fence,

cable, locked gate, or other type of constructed barrier.

Usually the surrounding buffer zone will eliminate offroad vehicular access, but if natural geographic barriers do

not exist, fencing the entire site might be necessary

Summary

T

oday municipalities face major challages when

attempting to site and design compost processing

facilities. When developing a composting facility

municipalities must consider a number of factor ineluding location, topography zoning laws, land

availability and ownership. The facility needs to be

designed to accommodate both current and projected

operations. To ensure that the facility is well sited

and designed input should be sought regarding the

technical and economic aspects of a composting system from a range of specialists including engineers,

biologists, system managers, and equipment suppliers.

Municipalities also must accommodate the needs of

local residents throughout the siting and design process to ensure the construction of a facility that the

whole community will find acceptable. Community

involvement is critical since one of the major factors

in the shutdown of many composting operations has

been complaints from neighboring household and

businesses about odors.

Chapter Five Resources

Albrecht, R. 1992. National Solid Waste Management Association (NSWMA). Seminar on composting. Ft. Lauderdale, FL. November 19-20.

Appelhoff, M., and J. McNelly. 1988. Yard waste composting Guidebook for Michigan communities. Lansing,

MI: Michigan Department of Natural Resources.

composting Council (CC). 1991. Compost facility planning guide. Washington, DC: composting Council.

Darcey, S. 1993. Communities put wet-dry separation to

the test. World Wastes. 36(98):52-57.

Mielke, G., A. Bonini, D. Havenar, and M. McCann.

1989. Management strategies for landscape waste. Springfield, IL: Illinois Department of Energy and Natural Resources, Office of Solid Waste and Renewable Re.sources.

Richard, T., N. Dickson, and S. Rowland. 1990. Yard

waste management A planning guide for New York State.

Albany, NY: New York State Energy Research and Development Authority, Cornell Cooperative Extension, and

New York State Department of Environmental

Conservation.

Rynk, R, et al. 1992. On-farm composting handbook.

Ithaca, NY: Cooperative Extension, Northeast Regional

Agricultural Engineering Service.

Strom, P., and M. Finstein. 1989. Leaf composting manual for New Jersey municipalies. New Brunswick, NJ:

New Jersey Department of Environmental Protection, Division of Solid Wrote Management, Office of Recycling.

University of Connecticut Cooperative Extension Services

(UConn CES). 1989. Leaf composting A guide for municipalities. Hartford, CT: State of Connecticut Department of Environmental Protection, Local Assistance and

Program Coordination Unit, Recycling Program.

Washington Department of Ecology (WDOE) and U.S.

Environmental Protection Agency (EPA). 1991. Summary

matrix of state compost regulations and guidance.

Minneapolis, MN.

Walker, J. 1992. Control of composting odors. As cited in

Hoitink, H., and H. Keener, eds. Science and engineering

of composting An international symposium. Worthington,

OH: Renaissance Publications. March 27-29,1992, Columbus, OH.

6 4
Chapter Six

The Composting Process:

Environmental, Health,

and Safety Concerns

Some aspects of the composting process can pose potential environmental, health, and safety problems. Decision-makers must be aware of these possible complications before proceeding with composting facility planning so that measures can be taken to avert difficulties. This chapter will help official understand the

potential risks involved with composting. Over the past several yearn several composting facility closures have

occurred due to some of the problems mentioned in this chapter, particularly odor The firrst portion of this chapter

describes the possible environmental concerns associated with the composting process such as water and air pollution. The second section discusses potential worker health and safety issues. Potential environmental health, and

safety concerns associated with the compost product are discussed in Chapter 9.

Environmental Concerns During

composting

If not carefully controlled, the composting process can

create a number of environmental concerns including air

and water pollution, odor, noise, vectors, fires, and litter.

Many of these concerns can be minimized through the

proper design and operation of a facility. In addition, simple procedures often can be implemented to reduce the

impact of the facility on the environment.

Water Quality

Water pollution from leachate or runoff is a potential concern at composting facilities. Leachate is liquid that has

percolated through the compost pile and that contains extracted, dissolved, or suspended material from the pile. If

allowed to run untreated and unchecked from the composting pile, leachate can seep into and pollute ground

water and surface water. Runoff is water that flows over

surfaces without being absorbed. Contaminated runoff

from composting sites can be a problem (particularly at

MSW composting facilities) in areas with high rainfall or

during periods of heavy rain. Both runoff and leachate

also can collect in pools around the facility, producing

odor problems. In addition, runoff can cause erosion.

There are many ways to prevent and control leachate and

runoff at composting operations, as described in the following sections.

Leachate

Leachate from the composting of yard trimmings can

have elevated biochemical oxygen demand (BOD) and

phenols, resulting from the natural decomposition of organic materials. High BOD depletes the dissolved oygen

of lakes and streams, potentially harming fish and other

aquatic life. Naturally occurring phenols are nontoxic but

can affect the taste and odor of water supplies if they

reach surface water reservoirs. Natural phenols and BOD

do not appear to pose a problem to ground water supplies, however, as they are substantially reduced by soil biota through degradation processes (Richard and Chadsey,

1990). Table 6-1 shows elevated levels of phenols and

high BOD in leachate from a leaf composting facility in

Croton Point, New York.

Another potential water contamination problem at facilities that compost yard trimmings is nitrate generation

caused by composting grass clippings along with leaves.

Because grass clippings have a low carbon to nitrogen

(C:N) ratio, an initial burst of microbial activity depletes

oxygen in the composting pile before the grass is

completely composted. The lack of oxygen causes aerobic

65
Cd ND

Ni ND

Zn 0.11 0.13

Fe 0.57 0.78

K 2.70 0.99

NO 3-N 0.96 1.00

Phosphorus 0.07 0.08

COD 56.33 371.22

pH 7.75 0.36

Odor ND

The Composting Process: Environmental, Health, and Safety Concerns

Table 6-1. Croton Point, New York, Yard trimmings

compost leachate composition.

Compost Leachate (16 samples)

Avarage Standard

(mg/L) Deviation (mg/L)

Cu ND

Cr ND

Al 0.33 0.38

Pb 0.01 0.02

NH4-N 0.44 0.35

NO2-N 0.02 0.02

Phenols (total) 0.18 0.45

BOD >41a>60

Color ND

a

Includes 3 samples above detection limit of 150 mg/L.

ND - Not Determined.

COD - Chemical Oxygen Demand.

Source: Richard and Chadsey,1990.

microorganisms to die, releasing nitrates in their cells.

One way to avoid nitrate generation is to monitor the

C:N ratio, adjusting the feedstock to keep it at optimum

levels (see Chapters 2 and 4). At the Croton Point facility

(Table 6-l), nitrates were not a problem because grass was

not included in the feedstock. Grass clippings can be

composted suecessfully, however, if appropriate material

mix ratios, methodology, and equipment are used. In a 3-

year study conducted in Massachusetts, very little leaching

of nitrate was noted from windrows consisting of one part

grass to three parts leaves. Leaching did occur, however,

when windrows consisting of grass and leaves in ratios of

(or higher than) one part grass to two part leaves were

subjected to heavy precipitation or watering (Fulford et

al., 1992).

Leachate from yard trimmings and MSW composting

operations can also contain potentially toxic synthetic

compounds, including polychlorinated biphenyls (PCBS)

from treated wood; chlordane, a pesticide and polycyclic

aromatic hydrocarbons (PAHs), combustion products of

gasoline, oil, and coal. PCBS and chlordane are resistant

to biodegradation and so generally are not broken down

during the composting process (Gillett, 1992). While microorganisms can degrade PAHs during the composting

process, the compounds formed as a result of this process

can be more toxic than the original PAHs (Chancy and

Ryan, 1992; Menzer, 1991). Monitoring incoming feedstock to remove pesticide containers and other foreign

materials can help reduce the occurrence of synthetic

chemicals in leachate.

Leachate generation can be reduced or prevented by

monitoring and correcting the moisture levels in the composting pile. In addition, the windrows or piles can be

placed under a roof to prevent excessive moisture levels

due to precipitation. If the composting materials contain

excess moisture, leachate will be released during the first

few days of composting even without added moisture or

precipitation. Following this initial release of leachate, the

amount of leachate formed will decrease as the compost

product matures and develops a greater capacity to hold

water.

The age of the pile also affects the composition of

leaehate. As the pile matures, microorganisms break down

complex compounds and consume carbon and nitrogen.

If the C:N ratio is maintained within the desired range,

little excess nitrogen will leach from the pile since the microorganisms will use this element for growth. A study

conducted by Cornell University researchers supports this

theory (Rymshaw et al., 1992). Table 6-2 summarizes the

results of the one portion of the Cornell study in which

water was added to columns of manure-bulking agents

and the leachates tested for nitrogen content. The leachate

produced from 19 weeks of composting and longer was

much lower in total nitrogen content than it was in the

begining of the study. Table 6-3 shows concentrations of

nitrogen from leachate collected under an actual composting windrow of manure and sawdust. This portion of the

study shows an initial peak of nitrogen concentration followed by a subsequent decrease over time. Therefore, as illustrated by this study the older the composting pile, the

less nitrogen will leach from the pile.

Many composting Facilities use a concrete pad to collect

and control any leaehate that is produced (see Chapter 5).

The primary task here is to watch the edges, catching any

leachate before it leaves the pad. The simplest way to handle leachate is to collect the water and reintroduce it into

the compost pile. This should not be done once the composting materials have passed the high-temperature phase,

however, as any harmful microorganisms that were inactivated by the high heat can be reintroduced with the

leaehate (CC, 1991).

66
mg/L

Nitrate 0.0/13.0 0.0/526.0 7.0/ 134.0

Organic Nitrogen 957.4/17.5 702.6/25.9 747.3/71.0

Total Organic Carbon 1,780.8/1,318.1 829.1/1,201.6 1,443.8/995.4 %Water Retained 92.00/85.00 6.67/70.00 781.00/71.25

1.0 10.00 28.53 109.90 138.25 8,743.71

2.0 10.50 21.00 105.00 126.00 6,258.96

5.0 3.00 29.80 32.20 62.00 3,715.66

8.5 4.00 14.84 58.80 73.64 50.80 2,459.63

1.5 13.00 12.95 115.50 128.45 9,384.00

2.5 9.00 25.20 86.80 112.00 5,372.81

3.0 15.00 8.40 134.40 142.80 14,174.92

8.0 3.00 39.91 39.91 75.90

The Composting Process: Environmental, Health, and Safety Concerns

Excess amounts of leachate beyond the moisture needs of

the composting facility can be transported to a municipal

wastewater treatment plant if the plant will accept them.

If the plant indicates that the contaminant levels in the

leachate are too high, an onsite wastewater pretreatment

system might be needed. If leachate is stored, treated on

site, or discharged to a municipal wastewater treatment

facility, facility operators must comply with federal, state,

and local requirements such as regulations covering storage, pretreatment, and discharge permits. It is unlikely

that pretreatment will be necessary, however, if the feedstock is monitored carefully. Measures to control leachate

include

Table 6-2. A summary of column study concentrations.

Diverting leachate from the compost curing and

storage areas to a leachate holding area.

Installing liner systems made of low-permeability

soils such as clay or synthetic materials.

Using liners under drain pipes to collect the

leachate for treatment.

Curing and storing compost indoors to eliminate

infiltration of leachate into the ground (With,

1989).

Chip/Newspaper straw Sawdust

Initial/Final Initial/Final Initial/Final

Ammonia 239.4/1 1.2 293.1 /17.5 800.8/8.71

Total Nitrogen 1,1 96.8/28.7 995.7/45.4 1,548.2/79.7

Laboratory experiment used 10-inch diameter, 24-inch deep columns of manure-bulking agent (woodchips and newpaper, straw, or sawdust) to which

water was added. Volumes of water applied corresponded to 2.1 to 12.4 cm of rainfall. Samples were collected from the bottom of the columns over 20

weeks, 21 week, or 19 weeks (for chips/newspaper, straw, and sawdust, respectively.

Source: Rymshaw et al., 1992.

Table 6-3. A summary of windrow leaehate concentrations.

Organic Total Total Organic

Weeks NO3 NH4 Nitrogen Nitrogen P04 Carbon

Leachate was collected from under a composting windrow of manure and sawdust.

Source: Rymshaw et al., 1992.

67
The Composting Process: Environmental, Health, and Safety Concerns

Runoff

Runoff can be caused both by heavy precipitation and by

the many aspects of the composting process that use

water. For example, the water used to wash trucks and stationary machinery can contribute to runoff. Highly polluted water can be spilled in the tipping area of MSW

composting facilities when packer trucks and compaction

boxes from restaurants, grocery stores, and food processors

are emptied. While MSW facilities are more prone to polluted runoff problems, operations that are composting

yard trimmings can also produce runoff containing small

quantities of heavy metals, pesticides, and inorganic

nutrients.

For both yard trimmings composting facilities and MSW

composting facilities, water that has come into contact

with incoming raw materials, partially processed materials, or compost should not be allowed to run off the site.

Figure 6-1 shows several options for diverting water from

composting windrows and for containing runoff from the

piles. The facility design must include provisions for isolating, collecting, treating and/or disposing of water that

has come in contact with the composting feedstock. These

provisions can include:

Maintaining sealed paving materials in all areas.

Grading facility areas (1 to 2 percent grade) where

contaminated water will be collected.

Erecting containment barriers or curbing to prevent contaminated water from coming in contact

with adjacent land areas and waterways.

Covering processing areas (composting beds and

compost product processing areas).

Percolating contaminated water through soil so as

to absorb and break down organic compounds.

Creating detention ponds to prevent the discharge

of runoff to surface water.

If runoff contains significant amounts of solids (often the

case for truck or floor wash-down water), screening, settling, or skimming might be necessary. If runoff is stored,

treated on site, or discharged to a municipal wastewater

treatment facility, facility operators must comply with federal, state, and local requirements such as regulations covering storage, pretreatment, and discharge permits.

Because runoff can contribute to soil erosion at and

around a facility, some simple steps can be taken to avoid

soil loss:

■ Choosing erosion control measures that are appropriate for the given soil type more stringent measures are needed for less permeable soil.

■ Avoiding sites with steep slopes.

68

Grading the site properly (see Chapter 5).

Minimizing the disruption of existing surfaces and

retaining as much vegetation as possible when clearing the site.

Using proper fill and compaction procedures.

Prompt seeding and mulching of exposed areas.

Using erosion screens and hay or straw bales along

slopes.

Using grass filter strips to intercept the horizontal

flow of runoff When runoff passes through the

grass strip, pollutants usually settle out of the water

or are physically filtered and adsorbed onto the

grass.

Run-On/Ponding

Run-on also can be a problem at yard trimmings and

MSW composting facilities if the water enters the facility

during storms. The site should have a slight slope with

windrow piles oriented parallel to the slope to prevent

pending of rainwater among compost piles (Walsh et al.,

1990). (See Chapter 5 for more guidance concerning siting and site design.) Pending or pooling of water on the

site also can be a problem if the composting piles rest on a

soft suface. Loaders can dig up the dirt base with the

piles as they are turned, forming pits that allow water to

stand. To remedy this, new fill (e.g., soil, sand, or gravel)

should be brought in to replace the excavated material.

Equipment that is operated in mud also can create ruts in

which pending can occur. Avoiding work during wet conditions can prevent this problem, although the best way is

to compost on paved surfaces.

Air Quality

In general, air pollution is not a major concern at composting facilities, with the exception of the odor problems

discussed in the next section. Minor problems could arise,

however, from vehicle traffic. The amount of air pollution

from vehicle emissions can be reduced by organizing

drop-off points to minimize queuing or by restricting

feedstock delivery to compaction trucks. Finally any mobile equipment used at the facility should be well maintained to keep it operating cleanly.

Dust can frequently be a problem at composting facilities,

particularly in the dry summer months. Dust is generated

from dry, uncontained organic materials, especially during

screening and shredding operations, and from vehicle traffic over unimproved surfaces. Dust from composting operations can clog equipment, and carries bacteria and

fungi that can affect workers at the facility (see Occupational Health and Safety Concerns During composting

on page 71). As long as there is an adequate buffer zone

around the facility, however, residents near the Facility
Runof diversion channel Dike Pad length and windrow/pile length 2-4% slope Pad runoff collection channel Dike Possible holding pond or infiltration area View through the composting pad length 

Clean runoff Clean runoff Diversion terrace (dike and channel) Seepage from hill Composting pad Sub-suface drain leading to open surface outlet away from pad

Composting pad

Dike Dike Runoff diversion channel Compacted sand or gravel pad Composting pad cross section

(c) Diversion channel 1-to 3-foot depth

‘width determined

by runoff volume

Source: Rynk et al., 1992.

6 9

(6 inches minimum)

(a) Interceptor trench

Diversion terrace

(dike and channel

Sub-Surface drain

leading to open surface

outlet away from pad

(b) Dike
Hydrogen Sulfide Dimethyl Disulfide

Ammonia Trimethylamine Aminomethane 3-methylindole (skatole) Dimethylamine

Methanoic (formic) Butanoic ( butyric) Ethanoic (acetic) Pentanoic (vaaleric) Propanoic (propionic) 3-mehtylbutanoic (isovaleric) 

Propanone (acetone) 2-pentanone (MPK) Butanone (MEK)

Benzothiozole Phenol Ethanal (acetaldehyde)

Carbon Oxysulfide Methanethiol

Carbon Disulfide Methanethiol

Dimethyl Sulfide Ethanethiol

The Composting Process: Environmental, Health, and Safety Concerns

generally will not be affected by dust (Lembke and Kniseley 1980), and environmental effects are not likely. Methods for controlling dust on site are discussed later in this

chapter.

Odor

As discussed elsewhere in this manual, odor is a significant

concern. Many stages in the composting process can release odors. The feedstock can contain odorous compounds; odors can be produced during collection,

transport, and storage of the feedstock or discards; and

improper composting procedures can encourage the formation of odorous compounds (Kissel et al., 1992). Anaerobic conditions encourage generation of odorous

compounds like organic acids, mercaptans, alcohols,

amines, and hydrogen sulfide gas, and other odorous

sulfur compounds (Williams and Miller, 1992a; Diaz,

1987). Ammonia can be released under anaerobic conditions and aerobic conditions if the C:N ratio is less

than 201 (Kissel et al., 1992). The compounds thought

to be responsible for odors at composting facilities are

listed in Table 6-4. Chapter 4 discusses process and engineering controls for reducing nuisance odors.

Table 6-4. Compounds either specifically identified or

implicated in composting odors.

Sulfur Compounds

Ammonia and Hitrogon-Containing Compounds

Volatile Fatty Acids

Ketones

Other Compounds

Source: Williams and Miller, 1992a,

Noise

Noise is generated by trucks entering and leaving a

composting facility and by equipment used in composting operations. Hammermills and other shredding/grinding machines are the noisiest of this

equipment, generating about 90 decibels at the source.

Many states have noise control regulations that limit

noise at the property line.

Measures that can reduce noise emanating from the facility include

Providing an adequate buffer zone around the Facility with plenty of trees.

Including specifications for noise-reducing design

features, such as mufflers and noise hoods, when

procuring equipment.

Properly maintaining mufflers and other equipment components.

Coordinating hours of operation with adjacent

land uses.

Taking steps to limit traffic to and from the facility

(see “Controlling Air Pollution”).

These measures will not always protect workers from exposure to excessive noise on site, however. Further noise

control methods are described below under “Occupational Health and Safety.”

Vectors

Vectors are small animals or insects that can carry diseases.

Mice, rats, files, and mosquitoes are potential visitors to

facilities that compost yard trimmings and/or MSW. Rodents can be attracted by the food and shelter available at

composting facilities (particularly MSW composting operations) and can be difficult to eliminate. Where proper

operating procedures do not control rodents, the help of a

professional exterminator might be required.

Flies, which can transmit salmonella and other food-borne

diseases, are often carried in with the incoming material and

are attracted to windrows that have become anaerobic. Research has shown that all life stages of the housefly are killed

by the temperatures reached in the comparing pile

(Golueke, 1977). Mosquitoes, which can transmit disease,

breed in standing water. Insects can be controlled by keeping

the processing area neat, maintaining aerobic conditions and

proper temperatures in the windrows, and grading the area

properly to prevent pending.

Fires

If the compost material dries out and becomes too hot,

there is a potential for spontaneous combustion to occur

at composting facilities. Organic material can ignite

spontaneously at a moisture content of between 25 and

70
Mix Area 110 to 120

Near tTear Down Pile 8 to 24

Periphery of Compost Site 2 Centrifuge Operating Room 38 to 75 Grit Building 2 Pump House 10 backgraoung Level 2

Compost Pile 12 to 15 Front-End Loader Operations 11 to 79

The Composting Process: Environmental, Health, and Safety Concerns

45 percent. This is unlikely however, unless the material

reaches temperatures higher than 93°C (199°F), which

typically requires a pile over 4 meters high. Keeping the

windrows about 3 meters high and turning the compost

when temperatures exceed 60°C ( 140°F) will prevent

fires. In addition to these precautions, the site must be designed for access by firefighting equipment, including

clear aisles among windrows, and must have an adequate

water supply (see Chapter 5) (Richard et al., 1990).

Other steps that can reduce the risk of fire include preventing accumulation of dust produced by shredding operations and preventing in-vessel composting systems

from becoming too dry. Adequate site security is necessary

to ensure that composting sites do not become a target for

arson. Site security will also ensure that the facility does

not become a dumping ground for used oil, appliances, or

other unacceptable materials.

Litter

Littter from the composting facility can be a source of

complaints from nearby residents. Litter can come from

yard trimmings and MSW brought to the facility in open

loads, plastic and paper blowing from windrows, and rejects (such as plastic) blowing away during screening. Litter can be controlled by:

Requiring loads of incoming material to be covered.

Using movable fencing or chain link fences along

the site perimeter as wind breaks and to facilitate

collection of litter.

Enclosing receiving, processing, and finishing

operations.

Collecting litter as soon as possible before it

becomes scattered off site.

Removing plastic bags before windrowing or

collecting in paper bags, in plastic bins, or in bulk

(for leaves and woody materials) (Wirth, 1989).

Occupational Health and Safety

Concerns During composting

Potential health and safety problems at facilities for composting yard trimmings and MSW include exposure to

bioaerosols, potential toxic chemicals, and other substances. Excessive noise and injuries from equipment used

at the facility also can be concerns. These problems can be

minimized by proper siting, design, and operation of the

facility and by adequate worker training and education.

Additional information about recognizing and controlling

job risks can be obtained from Occupational Safety and

Health Administration (OSHA) regional offices or from

state agencies responsible for occupational health and

safety.

Bioaerosols

A variety of biological aerosols (bioaerosols) can be generated during composting. Bioaerosols are suspensions of

particles in the air consisting partially or wholly of microorganisms. These microorganisms can remain suspended

in the air for long periods of time, retaining viability or

infectivity. The bioaerosols of concern during composting

include actinomycetes, bacteria, viruses, molds, and fungi.

Aspertgillus fumigatus is a very common fungus that is

naturally present in decaying organic matter. The spores

of this fungus can be inhaled or can enter the body

through cuts and abrasions in the skin. The fungus is not

considered a hazard to healthy individuals. In susceptible

individuals, however, it can inhabit the lungs and produce

fungal infections. Conditions that predispose individuals

to infection by Aspergillus fumigatus or other molds and

fungi include a weakened immune system, allergies,

asthma, diabetes, tuberculosis, a punctured eardrum, the

use of some medications such as antibiotics and adrenal

cortical hormones, kidney transplants, leukemia, and lymphoma (Epstein and Epstein, 1989; Wirth, 1989; USDA

and EPA, 1980). Effects due to Aspergillus fumigatus exposure are hard to predict because infection depends on

worker susceptibility.

Aspergillus fumigatus often colonizes the incoming material at both yard trimmings and MSW composting facilities, and is readily dispersed from dry and dusty compost

piles during and after mechanical agitation. The levels of

Aspergillus fumigatus decrease rapidly only a short distance

from the source or a short time after activity stops

(Epstein and Epstein, 1989). Table 6-5 shows levels of

Aspergillsu fumigatus in different areas of a biosolids composting facility in Windsor, Ontario. While these data are

not from yard trimmings or MSW composting facilities,

Table 6-5. Levels of Aspergillus fumigatus at a sewage

biosolids composting facility.

Concentration

Location (CFU/m2

)

CFU = Colony-forming units.

Source: Epstein and Epstein, 1989

71
Biosolids Compost 3.9-6.3

Sheep Manure Compost 4.9

Using aeration sysems instead of mechanical

The Composting Process: Environmental, Health, and Safety Concerns

they do demonstrate the direct relationship between fungus levels and activity levels (Roderique and Roderique,

1990). Similar results have been seen in MSW composting plants in Sweden (Clark et al., 1983).

Another health concern at composting facilities is exposure to endotoxins. Endotoxins are toxins produced

within a microorganism and released upon destruction of

the cell in which it is produced. They can be carried by

airborne dust particles. Table 6-6 shows the levels of endotoxins in composts from various sources (Epstein and Epstein, 1989). The levels of endotoxins in the air at one

yard trimmings composting facility ranged from 0.001 to

0.014 mg/m3 (Roderique and Roderique, 1990).

Because bioaerosols and endotoxins are both carried as

dust, dust control measures should be incorporated into

the design and operation of the facility. These measures

help control worker exposure to and reduce the the risk of

disease from these airborne hazards. Several steps can be

taken to minimize dust generation at the Facility

Keeping compost and feedstock moist.

Moistening compost during the final pile teardown and before being loaded onto vehicles, taking

care not to over wet the material, which can produce leachate or runoff.

constructing driving surfaces from asphalt or concrete (or water can be applied to roadways to minimize dust) (Roderique and Roderique, 1990).

Minimizing dust from enclosed operations through

engineering controls such as collection hoods, negative air pressure at dust generation points, and baghouse technology. These controls, however, tend to

be expensive.

Isolating workers from spore-dispersing components of the composting process such as mechanical turning (for example, using tractors or

front-end loaders with enclosed air-conditioned or

heated cabs).

Table 6-6. Comparison of endotoxin levels in composts

from Various sources.

Source Levels ng/g)

Cattle Manure Compost 2.3

leaf Compost 4.5

Souce: Epstein and Epstein, 1989.

72

turning.

In addition to these control measures, workers should be informed that disease-producing microorganisms are present

in the composting environment and that, although the risk

of infection is low in healthy individuals, the following precautions should be adhered to for personal protection

Workers should wear dust masks or respirators under dry and dusty conditions, especially when the

compost is being turned (charcoal-filled respirators

also reduce odor perception).

Uniforms should be provided to employees, and

workers should be instructed to wash hands before

meals and breaks and at the end of the work shift.

Shower facilities should be available, and clean

clothing and shoes should be worn home by each

employee.

Cuts and bruises should receive prompt attention

to prevent contact with the incoming loads or

feedstock.

If the facility is enclosed, proper ventilation is

required.

Individuals with asthma, diabetes, or suppressed immune

systems should be advised not to work at a composting facility because of their greater risk of infection.

Potentially Toxic Chemicals

Some volatile organic compounds (VOCs), such as benzene, chloroform, and trichloroethylene can present potential risks to workers at MSW composting facilities

(Gillett, 1992). Certain solvents, paints, and cleaners contain VOCs. The combination of forced aeration (or periodic turning in the ease of window systems) and elevated

temperatures can drive VOCs from the composting material into the surrounding atmosphere, much as the aeration and heating of activated biosolids does. Workers are

more likely than compost users to be exposed to VOCs.

Modeling suggests that this is because most of the VOCS

in the feedstock should volatilize from mechanically aerated composting piles within 1 or 2 days (Kissel et al.,

1992). To avoid worker exposure to VOCs in enclosed

spaces, adequate ventilation is required. Control technologies developed for odor control also apply to VOC control. While misting scrubbers have been used to control

VOCs (Li and Karrell, 1990), biofilter design for removing VOCs is not fully developed, however (Kissel et al.,

1992). The best method of controlling VOC emissions is

to limit their presence in the feedstock. Limiting MSW

composting to residential and high-quality commercial

feedstocks, instituting source separation, and implement-
Tipping Floor 85-90

Primary Shedder 96-98

Secondary Shredder 91-95

Shop 78

Offices 67

Shredder Operator 83

OSHA 8-hr Standard

The Composting Process: Environmental, Health, and Safety Concerns

ing effective household hazardous waste collection and

education programs can minimize the amount of VOCs

in MSW (see Chapter 3).

More persistent organic compounds also pose a potential

threat to workers. Workers can be exposed to polychlorinated biphenyls (PCBs), dioxins, pesticides, and polyaromatic hydrocarbons (PAHs) from the composting

feedstock and compost itself, although the extent of exposure varies and is hard to determine (Gillett, 1992). Effects on worker health have not been observed from

exposure to metals during composing or from the finished compost itself Mozzon et al. (1987) found that airborne lead and cadmium concentrations were below levels

of concern at MSW processing sites (less than 0.003

mg/m3. Gillett (1992) suggests that compared to workers’ exposure to metals in polluted air and food, exposure

to metals in compost can be insignificant.

Noise Control

The best way to prevent health effects from excessive

noise is to use engineering controls that reduce worker exposure to noise. Regional OSHA offices can provide information to workers and employers regarding sources

and control of noise. To prevent hearing loss, workplace

noise levels should not exceed 85 decibels (dB). Table 6-7

shows that noise levels in some areas of yard trimmings or

MSW composting facilities can exceed 85 decibels. Composting equipment that creates excessive noise should be

avoided. It is often possible to purchase screening plants,

shredders, and other equipment that do not necessitate

the use of ear protection for workers (Appelhof and

McNelly 1988). Simple design control measures such as

lowering the height from which feedstock is dropped into

processors, rearranging machinery inside the facility, and

installing mufflers, can bring noise levels down. Hearing

protection should be provided until noisy equipment is

repaired or replaced.

Other Safety Concerns

Safe design and operation of equipment used at the composting facility are essential. For example, specialized windrow turning equipment typically has mixing flails that rotate

at high speeds and must be well shielded from human contact. Because stones and other objects can be thrown a long

distance from turning equipment, operators must ensure a

safe clearance around and behind this equipment. Devices

that prevent access to equipment undergoing servicing or

maintenance might be necessary since unexpected ignition

could cause injury to workers. The potential for shredder explosions is discussed in Chapter 4.

Table 6-7. Reported noise levels in resource

recovery plants.

Noise Level

location (dBA)

Shredder Infeed 85-90

Magnetic Separator 90-96

Air Classifier Fan 95-120

Control Room 70

Maintenance Laborer 89

OSHA Hearing Conservation Requirements 85

OSHA 4-hr Standard 95

dBA - A-weighted sound-pressure Ievel.

Adapted from: Robinson, 1986.

Worker training is an essential part of ensuring a safe

workplace. The objectives of employee safety and health

training are

To make workers aware of potential hazards they

might encounter.

To provide the knowledge and skills needed to perform the work with minimal risk to health and

safety.

To make workers aware of the purpose and limitations of safety equipment.

To ensure that workers can safely avoid or escape

from emergencies

Topics that should be covered in health and safety training

include the rights and responsibilities of workers under

OSHA and/or state regulations; identification of chemical, physial, and biological risks at the site; safe practices

and operating procedures; the role of engineering controls

and personal protective equipment in preventing injuries

and illnesses; procedures for reporting injuries and illnesses; and procedures for responding to emergencies.

Worker Training Chapter Six Resources

73
The Composting Process: Environmental, Health, and Safety Concerns

Summary

 nvironmental and worker health and safety

 problems can arise during processing. Environ-

 mental problems during composting such as

water and air pollution, odor, noise, vectors, fires,

and litter can be prevented or minimized through

proper facility design and operation. Facility planners and managers must also take steps to ensure a

safe workplace by reducing potential exposure to

pathogens, hazardous substances in composting feedstock, and excessive noise; by ensuring that equipment is design and maintained to prevent injuries;

and by providing worker training in safety and

health concerns.

Appelhof, M., and J. McNelly. 1988. Yard waste composting; Guidebook for Michigan communities. Lansing; MI:

Michigan Department of Natural Resources.

Canarutto, S., G. Petruzzelli, L. Lubrano, and G. Vigna

Guidi. 1991. How composting affect heavy metal content. BioCycle. June, 32(6):48-50.

composting Council (CC). 1991. Compost Facility planning guide. Washington, DC: composting Council.

Chancy, RL., and J.A. Ryan. 1992. Heavy metals and

toxic organic pollutants in MSW composts: Research results on phytoavailability, bioavailability, fate, etc. As cited

in H.A.J. Hoitink et al., eds. Proceedings of the International composting Research Symposium. In press.

Chancy, R.L. 1991. Land application of composted municipal solid waste Public health, safety, and environmental issues. As cited in: Proceedings of the Northeast

Regional Solid Waste composting Council Conference,

June 24-25,1991, Albany NY. Washington, DC.

Cimino, J.A. 1982. Carbon monoxide levels among sanitation workers. Proceedings of the 42nd annual AMA

congress on occupational health. Tampa, FL. As cited in:

J.A. Cimino and R. Mamtani. Occupational Hazards for

New York City Sanitation Workers. Journal of Environmental Health. 50(1):8-12.

Clark, C. S., R Rylander, and L. Larsson. 1983. Levels of

gram-negative bacteria, Aspergillus fumigatus, dust, and

endotoxins at compost plants. Applied Environmental

Microbiology. 45(5): 1501-1505.

de Bertoldi, M., F. Zucconi, and M. Civilini. 1988. Temperature, pathogen control and product quality. BioCycle.

February, 29(2):43-47.

Diaz, L.F. 1987. Air emissions from compost. BioCycle.

August, 28(8):52-53.

74

Dunovant, V.S. et al. 1986. Volatile organics in the wastewater and airspaces of three wastewater treatment plants.

Journal of the Water Pollution Control Federation. Vol.

58.

Epstein, E., and J.I. Epstein. 1989. Public health issues

and composting. BioCycle. August, 30(8):50-53.

Fulford, B.R, W. Brinton, and R DeGregorio. 1992.

composting grass clippings. BioCycle. May, 33(5):40.

Gillett, J.W. 1992. Issues in risk assessment of compost

from municipal solid waste: Occupational health and

safety, public health, and environmental concerns.

Biomass & Bioenergy. Tarrytown, NY: Pergamon Press.

3(3-4):145-162.

Golueke, C.G. 1977. Biological reclamation of solid

wastes. Emmaus, PA: Rodale Press.

Gordon, R.T., and W.D. Vining. 1992. Active noise control: A review of the field. American Independent Hygiene Association Journal. 53:721-725.

Kissel, J. C., C.H. Henry, and R.B. Harrison. 1992. Potential emissions of volatile and odorous organic compounds from municipal solid waste composting facilities.

Biomass & Bioenergy Tarrytown, NY: Pergamon Press.

3(3-4):181-194.

Lembke, L. L., and RN. Kniseley 1980. Coliforms in

aerosols generated by a municipal solid waste recovery system. Applied Environmental Microbiology. 40(5):888-

891.

Li, R, and M. Karen. 1990. Technical, economic, and

regulatory evaluation of tray dryer solvent emission control alternatives. Environmental Progress 9(2):73-78. As

cited in: Kissel, J. C., C.H. Henry, and R.B. Harrison.

1992. Potential emissions of volatile and odorous organic

compounds from municipal solid waste composting facilities. Biomass & Bioenergy. Tarrytown, NY: Pergamon

Press. 3(3-4): 181-194.

Menzer, R.E. 1991. Water and soil pollutants. As cited in:

Amdur, M. O., J. Doull, and C.D. Klaassen, eds. Casarett

and Doull’s Toxicology The Basic Science of Poisons, 4th

ed. New York, NY: Pergamon Press. pp. 872-902.

Mozzon, D., D.A. Brown, and J.W. Smith. 1987. Occupational exposure to airborne dust, respirable quartz and

metals arising from refuse handling, burning, and landfilling. Journal of the American Industrial Hygiene Association.48(2):111-116.

Naylor, L.M., G.A. Kuter, and P.J. Gormsen. 1988. Biofilters for odor control: The scientific basis. Compost Facts.

Hampton, NH: International Process Systems, Inc.

Pahren, H.R. 1987. Microorganisms

waste and public health implications.

environmental control. Vol. 17(3).

in municipal solid

Critical reviews in
The Composting Process: Environmental, Health, and Safety Concerns

Richard, T., N. Dickson, and S. Rowland. 1990. Yard

waste management A planning guide for New York

State. Albany, NY: New York State Energy Research and

Development Authority, Cornell Cooperative Extension,

and New York State Department of Environmental

Conservation.

Richard, T., and M. Chadsey. 1990. Environmental impact of yard waste composting. BioCycle. April, 31(4):42-

46.

Robinson, W. D., cd., 1986. The solid waste handbook.

New York John Wiley and Sons.

Roderique, J.O., and D.S. Roderique. 1990. The environmental impacts of yard waste composting. Falls Church,

VA: Gershman, Brickner & Bratton, Inc.

Rymshaw, E., M.F. Walter, and T.L. Richard. 1992. Agricultural composting Environmental monitoring and

management practices. Albany, NY: New York State Agriculture and Markets.

Rynk, R, et al. 1992. On-firm composting handbook.

Ithaca, NY: Cooperative Extension, Northeast Regional

Agricultural Engineering Service.

U.S. Department of Agriculture (USDA) and U.S. Environmental Protection Agency (EPA). 1980. Manual for

composting sewage sludge by the Beltsville aerated-pile

method. EPA1600-8-80-022. Washington, DC: EPA.

U.S. Environmental Protection Agency (EPA). 1989.

Characterization of Products Containing Lead and Cadmium in Municipal Solid Waste in the United States,

1970-2000. EPA/530-SW-89-015B. Washington, DC:

Office of Solid Waste and Emergency Response.

Walsh, P., A. Razvi, and P.O’Leary. 1990. Operating a

successful composting facility. Waste Age. January,

21(1):100.

Williams, T. O., and F.C. Miller. 1992a. Odor control using biofilters, Part I. BioCycle. October, 33(10):72-77.

Williams, T. O., and F.C. Miller. 1992b. Biofilters and facility operations, Part 11. BioCycle. November, 33(11):75-

79.

Wirth, R 1989. Introduction to composting. St. Paul,

MN Minnesota Pollution Control Agency.

75
I

Chapter Seven

State Legislation

and Incentives

Because of the lead role that states have assumed in regulating composting, this chapter focuses on state activities. State legislation has greatly influenced the development of composting approaches in many areas of the

country and a full understanding of early state legislative activity will confer a broad appreciation of legislation issues throughout the country related to the composting of yard trimmings and MSW This chapter presents an overview of existing state legislation on both yard trimmings and MS W composting and discusses state

incentive programs to stimulate yard trimmings and MS W composting. The chapter discusses permit and siting

requirements, facility design and operational standards, product quality criteria, bans on landfilling or combustion of organic material, recycling gosh, requirements directed at local governments to implement composting

programs, requirements directed at state agencies, and requirements the separation of yard trimmings and organics from MSW

Composing Legislation Overview

Adoption and implementation of composting legislation

is a cumbersome process, and the status of composting

legislation generally lags behind public and legislative interest in the issue. Very few states have composting laws

that have been fully implemented, but many states are in

the process of enacting legislation or promulgating regulations. In recent years, a surge in legislative activity concerning recycling and composting has occurred, and more

composting legislation can be expected in the near future.

In the absence of specific composting legislation, many

states and localities regulate yard trimmings and MSW

composting facilities under related environmental statutes.

For example, many jurisdictions have already implemented regulations governing the composting of sewage

biosolids. These jurisdictions often use these regulations

to control yard trimmings and MSW composting and, in

addition, usually borrow from EPA and state biosolids

composting laws when developing specific legislation for

the composting of yard trimmings and MSW. In November 1992, EPA issued 40 CFR Part 503, which pertains to

the land application, surface disposal, and combustion of

biosolids (sewage sludge). Many of the standards promulgated in this rule can be applicable to MSW compost.

Many states, in lieu of specific composting standards for

MSW, are using these standards as guidelines or as models

for regulations. State water and air pollution control laws,

solid waste management laws, and environmental protection laws also can be utilized to regulate composting. Of

special relevance is Part 503, which governs land application of biosolids and biosolids composting. In addition, a

wide range of local ordinances often are applicable, including zoning and building codes, regulations governing

materials that can be landfilled or incinerated, fire codes, and

safety regulations.

The use of a wide variety of nonspecific local and state ordinances to manage yard trimmings and MSW composting can create a complex regulatory framework. Because

of the benefits that can be accrued from composting (e.g.,

landfill diversion and production of valuable soil amendment products), some states and localities are seeking to

stimulate composting by minimizing this regulatory

complexity.

There are notable differences between legislation for

MSW and yard trimmings composting. The composting

of yard trimmings is much more widespread than MSW

composting. Consequently, more states have adopted specific legislation regulating the composting of yard trimmings. In general, however, because the composting of

yard trimmings poses freer problems than MSW

76
State Legislation and Incentives

composting, requirements for the composting of yard

trimmings are less stringent than those developed for

MSW. Legislation for the composting of yard trimmings

is usually general in scope and applies to operations that

handle leaves, grass clippings, brush, or some combination

of these materials. Legislation in a few states (such as New

Jersey), however, targets specific yard trimmings, such as

leaves. State MSW composting legislation generally covers

household MSW. When any amount of sewage biosolids

is co-composted with other materials such as yard trimmings or mixed MSW, it is regulated under EPA’s 40 CFR

Part 503 regulations.

Table 7-1 presents a summary of legislation at the state

level to encourage or mandate composting Table 7-2 describes specific state legislation used to regulate yard trimmings and MSW composting. These tables can be found

at the end of this chapter. The remainder of this chapter

discusses specific examples of state legislation pertaining

to yard trimmings and MSW composting.

Permit and Siting Requirements

To date, most states (especially those in the central and

western United States) have not established specific permit or siting requirements for facilities that compost yard

trimmings. In addition, because of minimal environmental impacts generally associated with the composting

of yard trimmings, a few states (Delaware, Michigan, and

Pennsylvania) have expressly exempted these facilities

from any requirements (CRS, 1989). Other states exempt

certain types of composting operations from permit and

siting criteria. For example, Florida has exempted backyard composting and normal farm operations from composting regulations (FDER, 1989). Wisconsin does not

require permits for operations that compost yard trimmings and that are less than 38 m3 in size (Wk. Stat.,

1987-1 988). New York also exempts small operations as

well as operations that compost only food scraps or livestock manure (N.Y. Gen. Mun. Law, 1990). Illinois does

not require permits for composting operations that are

conducted on sites where yard trimmings are generated.

composting operations that compost materials at very

low rates and most on-farm composting operations also

are exempt from permitting (111. Rev. Stat., 1989).

Those states that do have siting and permitting requirements for yard trimmings and MSW composting attempt

to minimize the impact of composting operations on surrounding property and residences, ensure appropriate

composting operations are conducted, and prevent environmental problems associated with leachate runoff. For

example, Illinois prohibits siting of facilities for the composting of yard trimmings within 200 feet of a potable

water supply or within 5 feet of a water table, inside the

10-year floodplain, or within 200 feet of any residence. In

addition, the legislation states that the location of a composting facility shall “minimize incompatibility with the

character of the surrounding area” (Ill. Rev. Stat., 1989).

New Jersey legislation requires every Soil Conservation

District in the state to develop site plans for leaf composting facilities that are to be constructed within their jurisdictions. These site plans must include any information

required by the state’s Department of Environmental Protection (N.J. Stat., 1990).

Permitting and siting regulations for MSW composting

are usually more stringent than those for yard trimmings.

Florida regulates mixed MSW composting facilities to the

same degree as solid waste disposal sites. These regulations

prohibit siting MSW composting facilities in geologically

undesirable areas (such as in open sink holes or gravel

pits), within 500 feet of a shallow water supply well,

within 200 feet of a water body, in an area subject to

flooding, within public view from any major thoroughfare

without proper screening, on the right-of-way of a public

road, or near an airport (FDER, 1990).

Pennsylvania has also adopted a strict set of standards for

permitting and siting MSW composting facilities. In order

to receive a permit for MSW composting plans must be

submitted to the state’s Environmental Quality Board. These

plans must describe facility siting and design; facility access;

control of leachate, soil erosion, sedimentation, odor, noise,

dust, and litter alternative management of feedstocks or

compost in case processing operations or end-use markets;

ground-water monitoring and revegetation and postclosure

land use for the site (Penn. Env. Qual. Board, 1988). Strict

siting regulations to prevent contamination of surface or

ground-water resources are also included in the Pennsylvania

rules. For example, siting a facility within the 100-year

floodplain or within 300 feet of “an important wetland” is

prohibited (Penn. Env. Qual. Board, 1988).

Facility Design and Operations

Standards

Most states have not adopted specific regulations for the

design and operation of yard trimmings and MSW composting facilities. The legislation that has been adopted attempts to minimize negative impacts associated with

composting and to protect public health and the environment. New Jersey has adopted a relatively extensive set of

regulations concerning leaf composting operations. These

regulations restrict access to composting facilities; limit

the maximum quantity of leaves to be composted per

acre; limit windrow size, govern windrow placement; restrict the grade of compost pads; establish a minimum

turning frequency for windrows; limit the quantity of

compost that can be stored on the site; and require the use

of leachate, odor, dust, noise, and fire controls. In addition, representatives from the Soil Conservation Districts

are required to conduct annual inspections of leaf

77
State Legislation and Incentives ,

composting facilities operating within their jurisdiction to

ensure that the facilities are properly managed and maintained. Other states have adopted portions of these regulations for facilities that compost leaves and yard trimmings

in general.

Florida regulations are similar to those that have been

implemented in New Jersey but include some specific

requirements geared toward controlling the potential

safety, health, and environmental impacts that might be

associated with operations that compost mixed MSW.

These requirements include prohibitions on the composting of biohazardous wastes and hazardous wastes, except

for small quantities of household hazardous wastes. The

Florida regulations also include requirements for temperature monitoring and recordkeeping and specify the following that appropriate stormwater management systems

must be implemented at composting facilities; all-weather

access roads to the facility must be provided; detailed

signs indicating the name and telephone number of the

operating authority, hours of operation, charges, etc.,

must be posted; and litter control devices must be installed (FDER, 1989). In addition to operational requirements similar to those of Florida, Pennsylvania’s

regulations require that feedstocks are weighed when received, composting equipment is properly maintained,

salvaging of materials is strictly controlled, unloading of

feedstocks is conducted in a safe and efficient manner,

point and nonpoint source pollution of water resources is

prevented, soil erosion and sedimentation does not occur,

soil and ground-water monitoring is conducted, and residues from composting operations are “disposed or processed at a permitted facility for municipal or residual

waste” (Penn. Env. Qual. Board, 1988).

New Jersey regulates mixed MSW composting under the

same rules as sewage biosolids composting. Pathogen contamination is consequently regulated in a strict manner

and only three specific methods of mixed MSW composting can be used:

78

windrow composting- Under this method, aerobic

conditions must be maintained, temperatures

within 6 to 8 inches of the surface of the windrow

must remain above 55°C (131 ‘F) for at least 15

consecutive days, and the windrow must be turned

at least five times during this 15-day period.

Aeratedstatic pile - With this method, the pile must

be insulated and temperatures of at least 55°C

(131°F) must be maintained for a minimum of 3

consecutive days.

In-vessel composting - In this method, the composting mixture must be maintained at a minimum

temperature of 55°C (13 1°F) for at least 3 consecutive days (N.J. Dept. Env. Prot., 1986).

Product Quality Criteria

A few states have adopted a variety of criteria to classify

different grades of compost. Criteria covering yard trimmings and MSW composts have been developed that concern the degree of stabilization, particle size, moisture

content, levels of organic vs. inorganic constituents, and

contaminant content. Florida’s regulations governing

compost product quaky are some of the most well-developed to date. Under these regulations, finished compost

products must be tested by approved methods and information must be recorded on the following parameters:

percent moisture content; percent of total dry weight of

nitrogen, phosphorus, and potassium percent organic

matter pH; percent foreign matter mg/kg dry weight of

cadmium, copper, lead, nickel, and zinc; and most probable number of feed coliform. After testing, the quality of

the compost is classified based on the type of feedstocks

processed as well as strict specifications concerning the

maturity of the product, the foreign matter content, the

particle size, and metal concentrations. Seven levels of

compost quality have been specified:

Type Y composts use yard trimmings as the only feedstock; are mature or semimature have fine, medium, or coarse particle size; and have a low foreign

matter and metal content.

Type YM composts have the same characteristics as

Tpye composts but can also use livestock manure

as a feedstock.

Type A composts use MSW as the feedstock, are mature, have a fine particle size, and have a low foreign matter and metal content.

Type B composts use MSW as the feedstock, are mature or semimature, have a fine or medium particle

size, have an intermediate foreign matter content,

and have low or intermediate metal concentrations.

Type C composts use MSW as the feedstock are mature or semimature, have free, medium, or coarse

particle size, have high foreign matter content, and

have high, intermediate, or low metal

concentrations.

Type D composts use MSW as the feedstock; are

fresh; have fine, medium, or coarse particle size

have a high foreign matter content; and high, medium, or low levels of metals.

Type E composts use MSW as the feedstock and

have very high metal concentrations (FDER, 1989).

Under Florida regulations, distribution of compost Types

Y, YM, and A are not restricted. Distribution of Type B

or C compost is restricted to commercial, agricultural,
State Legislation and Incentives

institutional, and governmental use. In addition, according to the regulations, if the compost “is used where contact with the general public is likely, such as in a park,

only Type B maybe used” (Fla. Stat., 1989). Distribution

of Type D is restricted to landfills or land reclamation

projects with which the general public does not generally

come into contact. Finally, Type E composts must be

disposed of in a solid waste facility (FDER, 1989).

Approaches of this kind to regulate compost quality currently are being pursued by several other states.

Pennsylvania has adopted a case-by-case approach for

regulating the quality of MSW compost. The state requires that a chemical analysis of MSW compost products be performed and submitted to the Department of

the Environment before sale and distribution of the

material. The regulations state that “if the Department

determines that the compost has the potential for causing air, water, or land pollution,” the compost facility

operator will be informed that the compost must be

“disposed of at a permitted disposal facility” (Penn.

Env. Qual. Board, 1988).

Bans on Landfilling or Combustion

Several states have restricted the use of certain disposal options (particularly landfilling and combustion) for yard

trimmings. Usually, legislation of this kind is coupled

with state efforts to implement composting programs.

Even where no overt state efforts exist to initiate the composting of yard trimmings, however, disposal bans indirectly stimulate the composting of yard trimmings.

Currently 21 states have enacted a disposal ban on yard

trimmings or components of yard trimmings. Wisconsin

and Iowa, for example, have adopted legislation that bans

both the landfilling and combustion of yard trimmings

(FDER, 1989; Iowa Adv. Legis. Serv., 1990). Illinois,

Florida, Minnesota, and Missouri ban disposal of yard

trimmings in landfill (Ill. Rev. Stat., 1989; Fla. Stat.,

1989 Minn. Stat., 1990; Mo. Adv. Legis. Serv., 1990).

New Jersey has banned disposal of leaves in landfills (N.J.

stat., 1990).

Recycling Goals

Recycling goals have been established at the state or local

level in many areas. It is generally not mandated that

composting be performed in order to meet these goals; the

establishment of such goals, however, enhances the attractiveness of composting to states and localities. Some experts believe that without composting it will be difficult

to achieve recycling goals of 20 percent or more. Maine

and West Virginia are examples of states that have set recycling goals that specifically mandate the composting of

yard trimmings (W.Va. Code Ann., 1990, Me. Rev. Stat.,

1989).

Requirements for Local Governments to

Implement Composting

Some states do require local governments to implement

composting programs. For example, state legislation in

Minnesota mandates that local governments develop programs for the composting of yard trimmings as part of

their overall recycling strategy (Minn. Stat., 1990). Similarly, New Jersey legislation directs localities to develop

programs for collecting and composting leaves (N.J. Stat.,

1990).

Requirements for State Agencies to

Compost

In several states, legislation requires state agencies to participate in composting. For example, Wisconsin legislation mandates that state agencies comply with the state’s

100 percent yard trimmings ban (WI Stat 1.59). Some

agencies, like the University of Wisconsin-Stevens Point,

have complied by creating onsite composting Facilities.

Other agencies, like the State Capitol Building have complied by contracting with existing composting facilities.

Wisconsin’s Department of Administration is responsible

for seeing that agencies meet the 100 percent requirement

and that no yard trimmings go to landfills from state

agencies. Alabama and New Mexico require state environmental departments to evaluate their state agencies’ recycling programs (including the composting of yard

trimmings) and develop new programs if necessary

(Michie’s Code of Ala., 1990; N.M. Ann. Stat.).

Separation Requirement

bother method of stimulating the composting of yard

trimmings without directly mandating that it occur is to

require that yard trimmings be separated from MSW before they are collected. Household separation of yard

trimmings facilitates composting by minimizing the need

for intensive sorting and removal procedures during compost preprocessing. Legislation in Delaware requires the

state’s solid waste authority to consider the separation of

yard trimmings for potential recycling programs (Michie’s

Del. Code Ann.). Iowa legislation directs local governments to require residents to separate yard trimmings.

Under this legislation, local governments are also instructed to collect yard trimmings if they normally collect

other forms of MSW (Iowa Adv. Legis. Serv., 1990).

Yard Trimmings and MSW

Composting Incentives

Several states have opted to stimulate yard trimmings and

MSW composting through a variety of incentive programs, whether they also subscribe to legislative mandates.

State composting incentives include encouraging localities

79
State Legislation and Incentives

1

to implement programs ardor giving them specific

authority to do so; providing grants to local governments

or private firms to develop composting programs; emphasizing market development for compost products; and developing educational programs on backyard composting.

State Encouragement and Local Authority

to Implement Programs

MSW management has traditionally been handled at the

local level. Many states have consequently opted to maintain and promote such local control. Some of these states

have also passed legislation that clearly communicates

their support of composting to local governments,

however. For example, legislation in both Florida and

North Carolina does not mandate that the composting of

yard trimmings occur at the local level, but encourages local governments to recycle yard trimmings (Fla. Stat.,

1989; Michie’s Gen. Stat. of N.C.). Similarly Iowa legislation does not require composting at the local level, but directs the state to “assist local communities in the

development of collection systems for yard waste . . . and...

the establishment of local composting facilities” (Iowa Adv.

Legis. Service, 1990).

Other states have supported local control by specifically

granting local governments the authority to mandate yard

trimmings and MSW composting. For example, legislation in New York gives municipalities the authority to

adopt laws requiring that materials, including garden and

yard trimmings, be “separated into recyclable, reusable or

other components” (N.Y. Gen. Mun. Law, 1990). Massachusetts’ legislation has a similar clause that applies to

MSW which states that local governments may establish

recycling programs mandating the separation, collection,

and processing of recyclable including “compostable

waste” (Mass. Ann. Laws, 1990).

Grants

Many states have sought to promote yard trimmings and

MSW composting by providing grants to local governments and private businesses to establish composting facilities. For example, Iowa law authorizes the state to

“provide grants to local communities or private individuals” that are establishing recycling facilities, including facilities for the composting of yard trimmings (Iowa Adv.

Legis. Serv., 1990). In Minnesota, those entities that develop yard trimmings and MSW composting projects can

receive “grant assistance up to 50 percent of the capital

cost of the project or $2 million, whichever is less” (Minn.

Stat., 1990). The state of Washington provides funds, as

available, to local governments submitting a proposal to

compost food scraps and yard trimmings (Wash. Rev.

Code, 1990).

Procurement

State agencies that work to build roads, control erosion,

construct buildings, and maintain land consume large

quantities of topsoil and organic materials. Many states

have committed to developing markets for yard trimmings and MSW compost by setting procurement policies for these agencies. Procurement policies encourage

state agencies to buy compost by (1) requiring that state

agencies give preference to compost when making purchase decisions or (2) requiring that a given percentage of

a state’s topsoil/organic material purchases are purchases

of compost.

As of April 1993, agencies in Georgia are required to give

preference to compost when purchasing topsoil and organic material. The legislation even specifies that the state

of Georgia give preference to compost made from sourceseparated, nonhazardous organics. Several states require

agencies to give preference to compost when it is cost

effective to do so. These agencies include Florida, Maine,

Minnesota, and North Carolina.

Encourgement of

Backyard Composting 

Several states are encouraging backyard composting or 

ganics. Legislation in Connecticut requires regional jurisdictions to foster recycling through a variety of

mechanisms, including backyard composting. These jurisdictions are directed to develop and then implement recycling plans that will facitate backyard composting of

organics. States such as Massachusetts, New Jersey, New

York, and Rhode Island have published manuals and brochures that explain backyard composting operations.

Education Programs

Several states encourage yard trimmings and MSW

composting through educational and public awareness

programs. Massachusetts has initiated a technical assistance program for yard trimmings and MSW composting. The state conducts hands-on workshops and

provides guidance materials on designing and operating

municipal compost facilities. In addition, state officials

visit compost facilities and potential composting sites

to provide expert guidance. In Seattle, Washington, an

urban, organic gardening organization, Seattle Tilth Association, trains volunteers to teach other city dwellers

how to compost yard trimmings and food scraps. The

volunteer educators, called “master composers,” are

thoroughly trained in basic composting methods, compost biology, system design, and troubleshooting. The

Seattle Tilth Association also operates a hotline to answer questions about composting.

80
State Legislation and Incentives

Summary

s

ignificant legislative activity has occurred at the

state level in recent years on both yard trimmings and MSW composting. States have

adopted legislation concerning permitting and siting 

of compost facilities, compost facility design and operation, compost product quality, landfilling or combustion of organic material, recycling goals, local

government implmentation of composting programs,

state agency composting policy and the separation of

yard trimmings and other organics from MSW. In

addition, many states have promoted yard trimmings

and MSW composting through a variety of incentive

programs that encourage heal development of composting and grant loca government the authority to l

implement such programs, provide find to local governments or private firms to develop composting programs, stimulate market development for compost

products, encourage backyard composting and advance educational programs.

Chapter Seven Resources

Cal Recovery Systems (CRS) and M. M. Dillon Limited.

1989. Composting A literature study. Ontario, Canada

Queen’s Printer for Ontario.

Florida Department of Environmental Regulation

(FDER). 1990. Florida Administrative Code. Solid Waste

Management Facilities. Rule 17-701.

Florida Department of Environmental Regulation (FDER).

1989. Florida Administrative Code. Criteria for the Production and Use of Compost Made from Solid Waste. Rule 17-

709.

Florida Statutes (Fla. Stat.). 1989. Title XXIX, Public

Health. Chapter 403, Environmental Control. Part IV,

Resource Recovery and Management, Fla. Stat. 403.70.

Glenn, J. 1992. Solid waste legislation: The state of garbage in America. BioCycle. May, 33(5):30-37.

Harrison, E. Z., and T.L. Richard. 1992. Municipal solid

waste composting policy and regulation. Biomass &

Bioenergy. Tarrytown, NY: Pergamon Press. 3(3-4):127-

141.

Illinois Revised Statutes (Ill. Rev. Stat.). 1989. Chapter

111 1/2, Public Health and Safety Environmental Protection Act.

Iowa Advance Legislative Service (Iowa Adv. Legis. Serv.).

1990. Seventy-Third General Assembly. Ia. ALS 2153;

1990 Ia. SF 2153.

Maine Revised Statutes (Me. Rev. Stat.). 1989. Title 38,

Waters and Navigition. Chapter 13, Wrote Management.

Subchapter I, General Provisions, 38 M.R.S. 1302.

Annotated Laws of Massachusetts (Mass. Ann. Laws).

1990. Part I, Administration of the Government, Title

VII, Cities, Towns and Districts. Chapter 40, Powers and

Duties of Cities and Towns, §8H.

Michie’s Code of Alabama (Michie’s Code of Ala.). 1990.

Title 22, Health, Mental Health and Environmental Control. Subtitle 1, Health and Environmental Control Generally. Chapter 22B, Recycling by State Agencies, Code of

AM. 22-22b-3.

Michie’s Delaware Code Annotated (Michie’s Del. Code

Ann.). Title 7, Conservation. Part VII, Natural Resources.

Chapter 64, Delaware Solid Wrote Authority. Subchapter

II, Recycling and Waste Reduction, 7 Del. C. 6453.

Michie’s General Statutes of North Carolina (Michie’s

Gen. Stat. of N.C.). Chapter 130A, Public Health. Article

9, Solid Materials Management. Part 2A, Nonhazardous

Solid Materials Management, N.C. Gen. Stat. 130A-309.

Minnesota Statutes (Minn. Stat.). 1990. Environmental

Protection. Materials Management, Ch. 115A.

Missouri Advance Legislative Service (Me. Adv. Legis.

Serv.). 1990. 85th General Assembly, Second Regular Session. Conference Committee Substitute for House Committee Substitute for Senate Bill No. 530. 1990 Mo. SB

530.

New Jersey Department of Environmental Protection

(N.J. Dept. Env. Prot.), Division of Solid Materials Management. 1986. Compost Permit Requirements, August 1.

New Jersey Statutes (N.J. Stat.). 1990. Title 13, Conservation and Development-Parks and Reservations. Chapter

lE, Solid Materials Management, 13:1 E-99. 12.

New Mexico Annotated Statutes (N.M. Ann. Stat.).

Chapter 74, Environmental Improvement. Article 9, Solid

Materials Act, N.M. Stat. Ann. 74-9.

New York General Municipal Law (N.Y. Gen. Mun.

Law). 1990. Article 6, Public Health and Safety, NY CLS

Gen Mun 120-aa.

Pennsylvania Environmental Quality Board (Penn. Env.

Qual. Board). 1988. Municipal Materials Management

Regulations. Chapter 281, composting Facilities. Pennsylvania Bulletin, April 9.

Revised Code of Washington (Wash. Rev. Code). 1990.

Title 70, Public Health and Safety. Chapter 70.95, Solid

Materials Management-Reduction and Recycling, RCW

70.95.810.

Washington Department of Ecology (WDOE) and the

U.S. Environmental Protection Agency (EPA). 1991.

Summary Matrix of State Compost Regulations and

81
State Legislation and Incentives

Guidance. Prepared for the Focus Group Meeting on and Regional Solid Materials Authorities, W. Va. Code

Compost Quality and Facility Standards. Minneapolis, 20-9-1.

MN.November 6-8 . Wisconsin Statutes (Wis. Stat.). 1987-1988. Chapter 144,

Water, Sewage, Refuse, Mining and Air Pollution. SubWest Virginia Code Annotated (W.Va. Code Ann.). chapter IV, Solid Materials, Hazardous Waste and Refuse,

1990. Chapter 20, Natural Resources. Article 9, County wk. stat. 144.79.

82
Alabama 25% Arkansas 40% Yes

California 50% Funds spent on topsoil organic materials must be spent on compost (20% by1993; 40% by 1995).

composting

Delware 21% recycling alone, which includes yard trimming compsoting; not mandated.

Florida 30% source reduction and recycling, which includes yard trimming composting. Yes State agenices and local governments m ust procure compost when price is equivalent, 

Hawaii 59% Yes

Indiana 50% Yes

Iowa

Kentucky 25% State agenciesmust give preference to compost.

Maine 50% recycling and composting; not mandated Yes All state agencies and public-funded construction/land maintenance activities will use composted and recycled prganic material 

Massachusette 21% composting specifically. Yes Michigan 8-12% composting specifically; not mandated Yes

State agencies must use compost where cost effective. Mississippi 25%

Missouri 40% Yes Montana 25%; not mandated

Nebraska 25% Yes State agencies and local governments must give preference to compost.

Nevada

District of Columbia 45% recycing alone, which included yard trimming composting Yes 

especially for highways, recultivation, and erosion control.

where economically feasible and environmentally sound.

Maryland 25% recycling alone, which includes yard trimmings composting Yes State agenciesand local governments must give preference to compost in any public-funded land maintenance activity.

State Legisiation and Incentives

Table 7-1. State legislation to encourage or mandate yard trimmings and MSW composting,

Solid Waste Management Goals Yard

(includes source reduction, recycling, and composting unless Trimmings

State otherwise specified; mandated unless otherwise specified) Bans Procurement

Connecticut 25% recycling alone, which includes yard trimmings

Georgia 25% State agencies must give preference to compost

for all road building, Iand development, and

land maintenance.

Illinois 25% recycling alone, which includes yard trimmings

composting.

50% Yes State and local agencies are directed to give

preference to the use of compost in land maintenance.

Louisiana 25%

25%

83
New Hampshire 40%

New Mexico 50% State and local agencies are directed to give preference to the use of compost in land maintenance

New York

North Carolina 25% Yes State agencies and local agencies must give preference to compost if it does not cost more.

Ohio 25% Yes

Oregon

25% recycling alone, which includes yard trimming composting. Yes (leaves and brush only).

Rhode Island

30% Yes State agencies and public funded projects must purchase compst where economically practicable.

25% Yes

40% ; not mandated

25% recycling alone, which includes yard trimmings composting. 

50% The State Department of General Administration must spend at least 25% of its budget on compost products for use as landscape materials and soil amendment; in 

Wisconsin Yes

July 1994, this figure will e raised to 50% for contracts that use soil cover on state and local rights-of-way, compost products must comprise 25% of 

July 1993, this figure will rise to 50% for state roads and in July 1994, the figure will rise to 50% for local roads.

State Legislation and Incentives

Table 7-1. (Continued).

Solid Waste management Goals Yard

(includes source reduction, recycling, and composting unless Trimmings

State otherwise specified; mandated unless otherwise specified) Bans Procurement

New Jersey 25% recycling , which includes yard trimmings composting Yes (leaves State agencies and local governments must

but excludes leaf composting as port of the goal. only). give preference to compost for public-funded

land maintenance activities.

60%; not mandated. State agencies must give

recycled materials, including compost.

Norfh

Dakota

Pennsylvania

South

Carolina

South Dakota

Tennessee

Texas*

Vermont

Virginia

West

Virginia

40%

50% State agencies must purchase compost to the

“maximum extent economically feasible”.

15% recycling alone, which includes yard trimmings

composting.

50%; not mandated. Yes

40%

50% Yes Agencies and instrumentalities of the state must use compost in all landscaping and

land maintenance activities.

“The Department of Health must compost 15% of the state’s solid waste stream by 1994.

Sources Glenn, 1992; WDOE and EPA, 1991.

84
Delware Contaminant Standards.

Design and sitting criteria exit for landscape composting.

Requirement for buffer distance and impermeable ground surfaces. Classifications for animal manures and vegetable trimmings.

Minnesota Sepearate requirements for yard trimmimg and MSW composting.

New Jersey Criteria for yard trimmings composting; separate criteria fo leaf composting alone. Requirements and guidelines for yard Trimmings composting.

Must be promulgated by the Department of General Services

type of material composted, maturity of compost, foreign matter content,

State Legislation and Incentives

Table 7-2. Legislation to regulate the composting of yard trimmings and MSW.

Requirements for Operating

State Compost Facilities

California

. Requirements for

Designing/Siting Compost Compost Classification/Quality

Facilities Standards

Connecticut Specific requirements far leaf

composting; leaf composting is

exempt from solid waste permitting

requirements.

Florida separate requirements exist for yard

trimmings and MSW composting.

Illinois Requirements exist for operating

landscape composting operations.

Iowa separate, extensive requirements far

yard trimmings and MSW composting.

Maine Specific requirements for “vegetative

requirements apply to biosoolids

composting, co-composting and

composting of vegetative trimmings.

Massachusetts MSW composting subject to state

solid waste management regulations

for

as for landfills); guidance is available

yard trimmings composting.

Missouri Minimal requirements for yard

trimmings composting.

New York Facilities that compost yard trimmings

or MSW must comply with regulations

for solid waste management facilities 

ond must also comply with specific

yard trimmings and MSW composting

requirement.

North Carolina Specific requirements for operating MSW composting facilities; also

requirements for yard trimmings,

agricultural, and silvicultural

composting.

same requirements exist far yard Compost must be classified based an

trimmings and MSW composting

additional restrictions are place on MSW composting. particle size, an heavy metal

content; restrictions on use of certain

categories of compost exist; compost

testing required.

Design criteria far MSW composting; pathogen control standards far

siting criteria far bath yard trimmings finished compost; finished compost

and MSW comnposting (slightly mare must be innocuous and free of

restrictive for MSW composting). sharp-edged objects.

MSW composting, some requirement Requirement for MSW compost;

as landfills; separate requirements guidelines for yard trimmings compost.

and guidelines far facilities that

compost yard trimmings.

Requirements MSW composting Classification standards and use

but not yard trimmings compacting. restrictions for some categories.

Siting criteria for facilities that Only yard trimmings can be used in

compost yard trimmings. the compost; compost from yard

trimmings is regulated as fertilizer or

soil conditioner, depending on how it

is Iabeled.

separate yard trimmings and MSW Classification requirement for MSW

facility design requirements; siting composting but not far yard trimmings.

criteria far solid waste management

facilities.

Specific requirement for designing

facilities;

specific classification system and

and siting MSW composting quality standards far MSW compost;

also siting and design requirements also requirement far yard trimmings,

far yard trimmings, agricultural, and agricultural, and silvicultural compost.

silvicultural composting.

85
Requirements for 

Virginia Separation operations criteria exit for yard trimmings and MSW composting, and no mixing is allowed.

scale, yard trimmings composting on a large scale (over 20,000 cubic

State Legislation and Incentives

Table 7-2. (Continued).

Requirements for Operating

State Compost Facilities

Pennsylvania

operating all compost facilities, but

these are to targeted at biosolids

composting; specific requirements

exist for operations that compost yard

trimmings.

South Carolina

Wisconsin Separate operations criteria exist far

yard trimmings composting on a small

yards annually), MSW composting,

and biosolids and Iivestock manure

composting.

Designing/Siting Compost Compost Clasaification/Quality

Facilities Standards

General requirements exist for siting No compost classification system or

and designing all compost facilities,

but these are targeted at biosolids

quality standards exist far MSW

composting, although some standards

composting; specific siting exist for biosolids composting and the

requirements exist for yard trimmings biosolids can be composted with

composting but no specific MSW; a classification scheme for

requirements for facility design. yard trimmings compost is in place.

Quality standards for yard trimmings

compost are being promulgated.

separate design and siting criteria Yard trimmings and MSW must be

exist far yard trimmings and MSW composted separately; MSW may be

Composting. composted with biosolids..

Siting criteria exist far all compacting Composting is classified into the

operations; in addition, operations following categories: household

that compost yard trimmings and are composting, neighhorhood 

20,000 cubic yards per year must composting, community yard

submit a design plan to state. trimmings composting, solid waste

composting, and biosolids and

livestock manure composting; yard

trimmings compost may be used without a permit, but a permit is

required to Iandspread MSW compost.

Sources: WDOE and EPA, 1991; Harrison and Richard, 1992.

86
Chapter Eight

Potential End

Users

C

ompost currently is used in a variety of applicatiom in the United States, from agriculture and landscaping

to reforestation projects and residential gardening. When planning a composting facility, decision-makers

should identify potential end users to determine the type of compost that is required For example, if a facility only produces low-quality unscreened compost and end users demand high-quality screened compost the product might not be used. By identifying potential end users, a facility can ensure that the compost product can be

marketed MSW composting facilities and large yard trimmings composting facilities might identi~ market for a

spectrum of end uses, from low- to high-quality compost, since the finished product does not always meet the desired specifications. This chapter discusses the potential end users ofcompost derived from MSW or yard trimming.

The Benefits of Finished Compost

Compost can benefit the biological, chemical, and physical properties of soil. Biologically compost enhances the

development of fauna and microflora, renders plants less

vulnerable to attack by parasites, and promotes faster root

development of plants. Chemically, compost benefits soil

in a number of ways. Compost increases nutrient content,

turns mineral substances in soil into forms available to

plants, and regulates the addition of minerals to soil, particularly nitrogenous compounds. In addition, compost

serves as a buffer in making minerals available to plants

and provides a source of micronutrients. Furthermore,

compost improves many physical properties of the soil,

including the soil’s texture, water retention capacity, infiltration, resistance to wind and water erosion, aeration capacity, and structural and temperature stability. Table 8-1

summarizes potential end users and their quality requirements for finished compost. These end-use markets are

examined in more detail in this chapter.

Agricultural Industry

A market assessment was conducted in 1991 to estimate

the potential demand for compost in the United States

(Slivka, 1992). This survey identified agriculture as the

largest potential end-use market for compost, accounting

for over 85 percent of potential use. At present, however,

the amount of compost used in large-scale agricultural applications is small.

Council survey of

According to a 1992 composting

126 yard trimmings and 20 MSW

composting programs, only four yard trimmings and three

MSW facilities mentioned the agricultural sector as an

end-use market.

Agricultural use of compost remains low for several reasons. One, the product is weighty and bulky, which can

make transportation expensive. The nutrient value of

compost is low compared to fertilizers. In addition, agricultural users might have concerns regarding potential levels of heavy metals (particularly lead) and other possible

contaminants in compost, particularly mixed MSW compost (see Chapter 9). The potential for contamination becomes an important issue when compost is used on food

crops. This concern is mitigated if compost is applied well

in advance of planting. Many experiments examining the

effects of MSW compost application on the physiochemical characteristics of soils have indicated positive results as

outlined in Table 8-2 (Shiralipour et al., 1992).

To successfully market a compost product to the agricultural sector, therefore, the compost must be available at

the appropriate time of year, be consistent in composition

and nutrient content, contain low levels of potentially

toxic substances, and be offered at a low cost. Additionally

difficulties associated with bulkiness must be resolved,

distribution channels established, and the positive effect of

compost on crop yields demonstrated (EPA 1993).

If these issues are addressed, compost has the potential to

be used in large quantities by the agricultural industry.

Compost can be used to increase the organic matter, tilth,

and fertility of agricultural soils. Compost also improves

87
120 100

80 60 40 20

compost application over a 14- year period

140

Source: Mays and Giordano,1989

160 200 T/A annullay 1969 -1973 8 T/A annually 1969- 1973 

No compost applied

(Kashmanian et al., 1990)

Potential End Users

the aeration and drainage of dense soils, enhances the

water-holding capacity and aggregation of sandy soils, and

increases the soil’s cation exchange capacity (i.e., its ability

to absorb nutrients) (Rynk et al., 1992). In addition, compost enhances soil porosity, improves resistance to erosion,

improves storage and release of nutrients, and strengthens

disease suppression (EPA, 1993). The near-neutral pH of

compost also is beneficial for growing most agricultural

crops.

An important potential use of compost in the agricultural

industry is its application as a soil amendment to eroded

soils. Farmers in the United States are increasingly concerned

about the depletion of organic matter in soil and are acutely

aware that fertilty is dependent upon maintaining a sufficient amount of organic matter in the soil (EPA, 1993).

Compost is an dent source of organic matter that can

enrich soil and add biological diversity. When applied to

eroded soils, compost can help to restore both organic

content and the soil structure

The use of compost can help restore and build up nutrients in soil. The nutrients in compost are released slowly

to the roots of plants through microbial activity over an

extended period of time, thereby reducing the potential

for nutrients to leach from the soil. The gradual dissipation of nutrients from compost also indicates that only a

fraction of the nitrogen and phosphorus available in compost is available to the crop in the first year. When applied

continuously, the supply of plant nutrients from compost

is enough to keep plants healthy for several years. Studies

on the residual properties of compost on agricultural soils

have reported measurable benefits for 8 years or more after the initial application (Rynk et al., 1992).

Effects of Compost Application on Crop Yields in Johnson City, Tennessee

c

ompost has been demonstrated to improve crop yields. A study was conducted in Johnson City, Tennessee, from 1968

to 1972 that involved applying compost made from mixed MSW to test plots. During the period of the study 13 successful corn crops were produced and yield increases due to compost application were noted. The total increase in

yield ranged from 55 percent with an application rate of 40 tons of compost per acre to 153 percent with an application

rate of 1,000 tons per acre (Mays and Giordano, 1989). The figure below outlines the increases in crop yields following

196 9 197 1 197 3 197 5 197 7 197 9 198 1 198 3

88
hardware/ lumber outlets

Greenhouses

Potential End User s

Table 8-1. Potential users and uses of compost.

User Group Primary Uses for Compost Products Compost Productsa

Agricultural and residential

Forage and field- Soil amendment, fertilizer supplement top

crop growers dressing for pasture and hay crop maintenance

Unscreened and

screened compost

Fruit and vegetable soil amendment fertilizer

farmer’s supplement, mulch for fruit trees

Unscreened and

screened compost

Homeowners Soil amendment, mulch, fertilier supplement,

and fertilizer replacemant for home gardens

and lawns

screened compost,

high-nutrient compost, mulch

Organnic farmers Fertilizer substitute, soil amendment Unscreened and

screened compost,

high-nutrient compost

Turf growers Soil amendment for turf establishment, top

dressing

Screened compost,

topsoil blend

Commercial

Top dressing for turf, soil amendment for

turf establishment and landscape plantings

Screened compost

General screened

compost product

Discount stores,

supermarkets

Resale to homeowners

Garden centers, Resale to homeowners and small-volume users screened compost, mulch

Golf courses Top dressing for turf, soil amendment for greens

and tee construction, landscape plantings

screened compost

topsoil blend

Potting mix component, peat substitute,

soil amendment for beds

High-quality, dry,

screened compost

Land-reclamation

contractors

Landscapers and

land developers

Nurseries

Topsoil and soil amendment for disturbed

landscapes (mines, urban renovation)

Unscreened compost,

topsoil bland

Topsoil substitute, rnulch, soil amendment,

fertilzier supplement

screened compost

topsoil bland, mulch

Soil amendment and soil replacement for

field-grown stock, mulch, container mix

component, resale to retail and landscape clients

Unscreened and

screened compost

composted bark mulch

Municipal

Landfills Landfill cover material, primarily final cover Unscreeneded lowquality compost

PubIic works Topsoil for road and construction work, soil Unsreened and screened

departments amendment end mulch for landscape plantings compost, topsoil bland

Schools, park Topsoil, top dressing for turf and ball fields, Screened compost,

and recreation soil amendment and mulch for landscape topsoil blend, mulch

departments plantings

Note: Unscreened compost with a consistent texture and few large particles maybe used in place of screened compost.

aTopsoil blend is a mixture of compost, soil, or sand to make a product with qualities similar to topsoil or loam. Mulch includes

unscreened, coarse-textured compost such as composted wood chips or bark.

Source: Rynk et al., 1992.
Msw N-P-K 35,70 2 years Feild Phosphate maine sand tailings Increased C.E.C a, E.C.b, O.M.c, Hortenstine and Rothwell, 1972 

MSW 37-99 3 years Field Clay Made the heavy soil more friable, promoted a crumbly structure, permitted better moisture absorption, reduced erosion, improved aeratioin, and increased pH. Duggan, 1973

MSW + SS 80,112,143 2 years Field Songo silt loam, clay loam Increased water holding capacity, O.M., pH, and K, Ca, Mg, Zn levels. Decreased bulk density and compression strength.Terman and Mays,1973

MSW+SS+N 124,248,496 5 year Field Halston loam Increased K, Ca, Mg, Zn, but decreased P levels in the soil. Duggan and Wiles, 1976

MSW 112,224,448 5 years Field Myakka-Basinger fine sand About 50%of the applied inorganic P was converted to organic P and remained in the zone of compost placement.

MSW+SS 3 years Field Alluvial, loamy Increased C, N, P, K levels. del Zan et al., 1987

MSW 25 Field and climate controlled pots Loamy and sand/vermiculite Did not execessively increase the heavy metals. Increased pH. Bauduin et al 1987 

MSW

MSW 15, 30 2 years, 6 months Field, greenhouse Increased macro amd micro elements, pH, E.C., and O.M. Manios and syminis, 1988

MSW N

MSW N

Metals were distributed in 0 to 23 cm depth

Fiskell and Pritchett, 1980

Potential End Users

Table 8-2. Effect of MSW compost application an physiochemical characteristics of soil.

Changes in Soil

Compost compost Duration of Experiment Physiochemical

Type Rate (mt/ha) Experiment Condition Soil Type Characteristics Reference

4.4,44 2 years Field Sandy soil Increased water holding

capacity,O.M.,pH Cornette, 1973

exchangeable Co, Mg, and K

Pelletized 8,16,32,6 4 16 months Greenhouse Arredondo Increased water holding Hartenstine

MSW, N-P-K

fertilizer

capacity, C. E.C., N, K, Ca, and Rothwelll,

Mg, B, Mn, and Zn levels. 1972

22,44,80, 2 years Field Songo silt Increased water holding Terman and

(ammonium 160,325 loam, clay capacity, O.M., pH, and K, Co, Mays, 1973

nitrate) loam Mg, Zn levels. Decreased bulk

density and compression

strength.

Field. Redish-brown Increased O.M. and water Wang, 1977

clay holding capacity.

MSW+SS — Field Sandy loam Increased H and P, K, Co, Mg Sanderson,

(mulching) levels. Reduced erosion. 1980.

MSW+SS — — Greenhouse Loamy sand Increased

Pb

, O.M., and Cd, Chu and

Cu, Mn, , Zn levels. Wong, 1987

6, 15,40 3 years Field. — Increased pH, O.M., and total N. Paris et al.,

1987

MSW, MSW+ — 24 pars Field Luvisol derived lncreased total C and total N. Werner et al.,

s s from Less 1988

90
MSW + SS+ N-P-K fertilizer 98.8 to2,470 7 years Field Alluvial, loamy Increased O.M.,C.E.C., pH, macro and micro elementrs, and heavy metals. Decreased bulk density Mays and Giordano 1989

MSW 15, 30, 60 7, 900, 180 days In chabers Typic Haploxeralt Increased aggregate stability, water holding capacity , and pH. No change in C.E.C. Hernando et al., 1989

Potential End Users

Table 8-2. (continual).

Changes in Soil

Compost Compost Duration of Experimental Physiochemical

Type Rate(mt/ha) Experiment Condition Soil Type Characteristics Reference

MSW 14 — Field Alluvial No change in available P levels, Cabrera et al.,

but increased K, and available 1989

levels of Cu, Zn.

Source: Shiralipour et al., 1992.

aC.E.C. = cation exchange capacity

bE C = . . electrical conductivity

cO.M. = organic matter content

Applying compost to soils reduces the likelihood of plant

diseases. This is due to several factors. First, the high temperatures that result from the composting process kill pathogens and weed seeds. The frequent turning of windrows and

the insulating layers in static piles ensure uniform high temperature exposure and, therefore, uniform pathogen reduction. Second, beneficial microorganisms in compost kill,

inhibit, or simply compete with pathogens in soil, thereby

suppressing some types of plant disease caused by soil-borne

plant pathogens and reducing the need to apply fungicides

or pesticides to crops. Microorganisms use the available nutrients in compost to support their activity. Organic matter

within compost can replenish the nutrients in soil that has

low microbial activity and, as a result, is susceptible to developing soil-borne diseases. Finally, physical and chemical

characteristics such as particle size, pH, and nitrogen content

also influence disease suppression. Research indicates that

some composts, particularly those prepared from tree barks,

release chemicals that inhibit some plant pathogens (Hoitink

and Fahy 1986; Hoitink et al., 1991).

Another potential use of compost in the agricultural industry is the prevention of soil erosion. Soil erosion has a

direct financial impact on food production and the economy. composting is one of the few methods available for

quickly creating a soil-like material that can help mitigate

this loss. Soil erosion also has a serious impact on the

quality of the nation’s surface water supply. Agricultural

runoff fromcroplands, pasture lands, rangelands, and livestock operations is estimated to be responsible for over 50

percent of the nonpoint source-related impacts to lakes and

rivers (Kashmanian et al, 1990). Encouraging farmers to use

compost made on and off the farm can bath reduce erosion

and improve water quality. Some counties in Tennessee and

Minnesota are allowed to “east-share” the agricultural use of

compost. The state helps farmers in these areas defray the

cost of purchasing or transporting the compost Kashmanian et al., 1990).

Landscaping lndustry

The landscaping industry is another potential outlet for

compost. According to the composting Council survey,

the majority of composting facilities surveyed sell compost to landscapers (79 yard trimmings facilities and 12

MSW facilities market to this industry). Landscapers use

compost in direct soil incorporation, in the production of

outdoor growing mixes, in the manufacture of topsoil for

new planting, as a soil amendment, and in turf establishment and maintenance projects. Landscapers require a

premium compost. In general, this means that the product should have minimal odor, particle sizes of no greater

than 1/2 inch in diameter, less than 50 percent moisture

content, and no plant or human pathogens (see Table 8-

3). Compost with a near-neutral pH is most suitable for

this industry. Every effort should be made, therefore, to

avoid using liming or acidifying agents during composting. Landscapers must have the flexibility of raising or

lowering pH themselves so the compost can be useful for

growing plants with different pH requirements.

The landscaping industry also requires that the materials

used in its projects meet the specifications of the landscape architect or inspector. Therefore, compost marketed

to this sector must be demonstrated to meet these specifications. Since landscapers also have expressed concern

about the possible presence of potentially toxic compounds in MSW compost and of viable seeds, herbicides,

and pesticides in yard trimmings compost, tests should be

conducted on the final compost product and the results

made available to potential users.

91
Montgomery Count, Maryland, sells, most of its compst to landscapers and nurseries in minimum loads of 10 cubic yards (epa,1993). The facility screens its finished compo

Using Yard Trimming Compost in Landscaping

from leaves and grass clippings, and tests it for weed seeds and heavy metals. Montgomery County has dfound the peak market demand for its finished product occurs in 

Potential End Users

The amount of compost used by the landscaping industry

depends on economic cycles in the construction and housing industries. For example, new construction projects such

as residential housing developments and commercial buildings can create a high demand for compost. The amount of

compost used by landscapers also is affected by price, availability and ease of compost application (EPA, 1993).

Landscapers have successfully used compost as a top dressing to reduce weed growth and improve the appearance of

soil and as a mulch to reduce evaporation and inhibit

weed growth. Compost is used in the manufacture of topsoil due to its ability to improve the quality of existing

soil, which is beneficial to new planting. This use of compost is attractive to landscapers because it can reduce the

amount of new topsoil needed, thereby reducing costs.

Other uses of compost in the landscaping industry include maintenance of lawns and parks, highway landscaping, and sod production. Athletic field maintenance,

renovation, and construction are other strong potential

uses for compost in this industry (Alexander, 1991).

Compost can be used as a soil amendment in the renovation of athletic fields, as a turf topdressing to help maintain the quality of the turf surface, and as a component of

athletic field mixes, which are used in the construction of

new fields.

Horticultural Industry

The horticultural industry is one of the largest potential

markets for compost of uniform consistent high quality.

Compost is attractive to the horticultural industry because

it is a source of organic matter and essential trace plant

nutrients, increases the water-holding capacity of soil, improves the texture of soil, and enhances a soil’s ability to

suppress plant diseases. The use of compost in potting

mixtures and in seedling beds has helped to reduce the

need to apply soil fungicides in the production of certain

horticultural crops (Rynk et al., 1992).

The use of compost by the horticultural industry depends

upon the quality of the compost, the consistency and

availability, and the cost. As is the case with landscapers,

the use of compost in this industry also depends upon the

state of the economy, particularly the housing industry.

The number of new single-family dwellings built and the

number of homes sold have a direct impact on the demand

for horticultural products. When home sales rise, the demand for nursery products increases as well (EPA, 1993).

The products distributed to the horticultural industry

must be of the highest quality and almost always must be

unlimed. Because of its higher pH, limed compost has

fewer applications than unlimed compost (Gouin, 1989).

To improve the quality of compost earmarked for the horticultural industry, the compost should be thoroughly

stabilized. composting in smaller piles and for longer periods of time aid the stabilization process. It is also impor92

tant for the compost to be odor free. This can be achieved

by ensuring that the compost does not become anaerobic

during curing or storage. In addition, the compost should

be stored either under cover or outdoors in low windrows

not to exceed 6 feet in height. Table 8-4 outline compost

quality guidelines based on certain horticultural end uses.

These suggested guidelines have received support from

producers of horticultural crops (Rynk et al., 1992).

One of the primary uses of compost in horticulture is as a

growing medium for plants. Approximately 60 percent of

all nursery and greenhouse plants currently marketed are

grown in containers. Because 60 to 70 percent of the container-growing medium is organic matter, the potential

market for high-quality compost is substantial (Gouin,

199I). As with farmers, however, the high value of the

horticultural industry’s crops also make this sector very

cautious and resistant to change (Alexander, 1990; Gouin,

1989). In addition, the horticultural industry already has

a dependable supply of products containing organic material. One of these products is peat moss. Significant

amounts of peat moss are used by nurseries for potting

mixes. Compost could be used as a substitute for peat

moss because it is a relatively inexpensive local source of

organic matter. In order for compost to take over a substantial amount of the market share currently held by peat

moss, laboratory analyses and field tests must be conducted

to demonstrate the benefits, safety, and reliability of the material (see Chapter 9).

Silviculture

Silviculture or forestry applications area potentially large

market for compost. A national study estimated that the

aggregate potential for silviculture application was 50 million metric tons annually (Slivka, 1992). Four segments of

this market present viable opportunities: forest regeneration, nurseries, Christmas tree production, and established

forest stands.

Regenerating forests represents the largest potential market for compost in a silvicultural application (Shiralipour

et al., 1992). Results from limited experimentation with
Low: Able to support grass Low Medium-high Medium-low

Agricultural Industry High Low concentration of physical/ chemical contaminants High organic content 1/2 particle size No phytotoxicity Low soluble salts Good water-holding capacity

Highe: pH 6.0-7.0 1/2 particle size Low soluble salts Good nutrient content Low concentration of physical/ chemical contaminnts 

Residential Sector High: Minimal odor 1/2 particle size <40% moisture content Low: concentration of physical. chemical contaminants Dark color 

Low soluble salts No olant/humn pathogens No weed seeds Dark color

High: Mature(stable) compost Low concentration of physical/chemical contaminants 1/2 particle size Good nutrient content No weed seeds Low Able to support grass/wildflowers

Sod farms

Potential End Users

Table 8-3. (Continued).

Potenial Compost

Users

Landscaping Industry

Horticultural

Industry/Nurseries

Public Agencies

Other

Land reclamation

Dedicated land

Golf courses

Quality Requirements

High: Minimal odor

pH 6.0-7.0; adjustable

5 1/2” particle size

2% moisture content

aphysical contaminants are visible, noncompostable particles; chemical contaminants include heavy rnetals and toxic substances.

Sources: EPA, 1993;Rynk et al., 1992.

compost applications during forest regeneration have

shown that compost applications have improved the

physiochemical properties of soil and have led to excellent

seedling survival and sustained growth advantages (Shiralipour et al., 1992). One long-term study, in which

MSW compost was applied during forest planting determined that MSW compost can provide forest growth advantages while causing no detectable problems

(Shiralipour et al., 1992).

Forest nurseries and Christmas tree production represent

potentially low-volume/high-value applications of compost. Organic amendments increase plant vigor, facilitate

improved root proliferation, and enhance survival in outplanning (Shiralipour et al., 1992). Approximately 123.5

acres of forest nurseries in Florida produced approximately 106 million seedlings for a 1990 planting of

150,670 acres of new plantations (Shiralipour et al.

1992). An average of 53.5 tons per acre of organic matter

are added annually to maintain Productivity of the seed

beds. Compost could

ralipour et al., 1992).

be used in- such applications (ShiThe option to usc compost in established forests is not as attractive as those opportunities outlined above due to difficulties associated with gaining adequate access to these areas

with compost spreading machinery Recently planted forests,

however, could be treated before canopy closure and while

access still is possible (Shiralipour et al., 1992).

Public Agencies

Compost uses that are applicable to the public sector include land upgrade, parks and redevelopment, weed

abatement on public lands, roadway maintenance, and

median strip landscaping. Municipalities that produce

compost should examine their internal needs for soil

amendments, fertilizers, topsoil, and other products. Since

many communities have this built-in market for compost,

they can avoid spending funds on such products, adding

to the overall cost-effectiveness of implementing a composting program. Some states have established standards

(e.g., Florida, Iowa, Maine, Minnesota, NeW Hampshire,

New York, and North Carolina) anchor procurement

93
product.

Municipalties Utilizing Compost for

alities, which make the compost available to residents in bulk form free of charge (EPA, 1993). The compost is made from yard trimmings collected from r

and landscapers

Potential End Users

The Use of Yard Trimmings Compost

in the Horticultural Industry

any facilities for the composting of yard trimmings successfully market their compost to the

horticulture industry. Some municipalities have

designed innovative marketing arrangements that

benefit both the community and the user. For example,

in Scarsdale, New York, the city works with a local

nursery in the composting of approximately 35,000

cubic yards of yard trimmings per year and in the distribution of the final compost. In return for a share of

the product, the nursery assists with turning the windrows and provides storage space for the finished compost. Twice a year, the compost is available free of

charge to residents in a “giveaway” program. The reremaining compost is marketed by the nursery as mulch

and also blended into potting soil and topsoil.

A composting facility located in Carver County,

Minnesota, has set up an enterprising arrangement

with the University of Minnesota. The composting

facility is located at the university landscape arboretum. In exchange for the site, the arboretum receives

approximately one-half of the finished compost

preferences (e.g., California, Florida, Illinois, Iowa, Kentucky, Maine, Maryland, Minnesota, Missouri, Nebraska,

New Jersey, North Carolina, Pennsylvania, South Carolina, Washington, and West Virginia) for using compost

in public land maintenance activities funded by the state

(Kashmanian, 1992) (see Chapter 7).

Public agencies can use both high- and low-quality composts. High-quality composts should be used in locations,

such as parks and playing fields, where people or animals

come in direct contact with the material or in the upgrade

of public lands. Upgraded land requires less water to irrigate, has an increased resale value, and has a higher quality

of soil (EPA 1993). In parks, high-quality compost can

be used primarily to build and maintain turf. A coarse

compost that has low water-retention capability can be

applied to areas where weed control is necessary.

Lower quality compost can be used for purposes such as

land reclamation, landfill cover, and, possibly large highway projects (EPA, 1993). Lower quality compost can be

used by public agencies (as well as private companies) to

establish vegetative growth and restore or enhance the soil

productivity of marginal lands. Uses of compost in land

reclamation include restoring surface-mined areas, capping landfills, and maintaining road shoulders polluted

with heavy metals and organic pollutants.

Reclamation of mine-spoil areas can be an excellent enduse option for large quantities of compost. Compost is

valuable for these sites because of its high water-holding

capacity. When using MSW compost in mine-spoil reclamation, soil-plant ecology must be considered in regard to

intended land use. For example, if the land is reclaimed

for a natural area, the compost will be required to aid in

the reestablishment of a natural ecosystem (Shiralipour et

al., 1992). If the land is reclaimed for future home sites,

the compost should aid in the support of typical landscape plantings and should not contain any pathogens.

Compost with excessive levels of heavy metals can be used

only for landfill cover. The composting Council’s 1992

survey reports that several communities across the nation

are using compost in the final capping of landfills. Escambia county, Florida, has been composting mixed MSW

since September 1991. From the outset, the county

planned to use the compost product for daily and final

landfill cover. The material is suitable for use as landfill

cover after four weeks of composting.

Most road shoulders are already polluted with heavy metals and organic pollutants from motor vehicles (Shiralipour et al., 1992). Therefore, the use of mixed MSW

compost would not substantially contribute to the deterioration of environmental quality and could reduce the

bioavailability of existing contaminants (Chancy, 1991).

The compost must be capable of supporting roadside

growth with minimal erosion, and the compost must

comply with both state and federal standards for land application. Federal and state highway departments have

standards or guidelines for reseeding and landscaping of

highway shoulders that might need to be modified to enable use of compost. The growth of this end use depends

on the amount of road construction and maintenance.

Residential Sector

The residential sector represents a substantial market for

compost. Gardeners frequently use compost as a soil amendment to improve the organic matter and nutrient content of

Public works Projects

ount Lebanon, in Allegheny County Pennsyivania, uses compost in parks and on the city’s golf

course (EPA, 1993). The compost is made from

leaves collected in the community. The county also is

planning to set up a series of composting areas in city

parks and to make the finished compost available to

municipalities and park departments. Compost pro- :

duced in Hennepin County Minnesota, is used by the

county’s parks department or redistribured to munici94
Improvement of agricultural

Potential End Users

Table 8-4. Examples of compost quality guidelines based on end use.*

End use of compost

Potting media Top dressing soil amendment

Characteristic Potting grade amendment grade a grade grade a

Recommened uses As a growing medium

without additional

blending

For formulating growing

media for potted crops

with a pH below 7.2

Primarily for topdressing turf soilds, restoration of disturbed

soils, establishment and

maintenance of landscape

plantings with pH

requirements below 7.2

Color Dark brown to black Dark brown to black

Odor

Dark brown to black Dark brown to black

Should have no

objectionable odor

would have no

objectionable odor

Should have no

objectionable odor

Should have good,

earthy odor

Less than 1/2 inch

(13 millimeters)

Leas than 1/4 inch

(7 millimeters)

Less than 1/2 inch

(13 millimeters)

Particle size Less than 1/2 inch

(13 milliliters)

Range should

be identified

5.0-7.6 Range should

be identified

Range should

be identified

pH

Soluble salt Less than 2.5 Less than 6 Less than 5 Less than 20

concentration

(mmhos per centimeter)

Foreign materials Should not contain

more than 5?’. by dry

weight of combined

glass, plastic, and

other foreign particles

Should not contain

more than 1% by dry

weight of combined

glass, plastic, and

other foreign particles

1/8-1/2 inch

(3-13 centimeters)

Should not contain

more than 1% by dry

weight of combined

glass, plastic, and

other foreign particles

1/6-1/2 inch

(3-13 centimeters)

Should not contain

more than 1% by dry

weight of combined

glass, plastic, and

other foreign particles

1/6-1/2 inch

(3-13 centimeters)

Should not exceed

EPA standards for

unrestricted usec

Should not exceed

EPA standards for

unrestricted use c

Should not exceed

EPA standards for

unrestricted use c

Should not exceed

EPA standards far

unrestricted use

Heavy metals

Respiration rate Less than 200 Less than 200 Leas than 200 Less than 400

(milligrams par

kilogram per hour) b

“Far craps requiring a pH of 6.5 or greater, use lime-fortified product. Lime-fortified soild amendment grade should have a soluble salt

concentration less than 30 mmhos per centimeter.

bRespiration rate is measured by the rate of consumed. It is an indication of compost stability.

cThese are EPA 40 CFR Part 503 standards for sewage biosolids compost. Although they are not applicable to MSW compost, they can be

used as a benchmark.

l These suggested guidelines have received support from producers of horticultural craps.

SourceS: Rynk et al., 1992.

95
Using Composting as a Growing Medium

MSW- derived composts as growing me

glatco-Lite is a compost produced from pulp and paper mill by-products; geophile is a compost producted from mixed MSW that has undergone ferrous metals separation prior to 

uct

Species Medium At planting At end of production Shoot Root Total

Cuban royal palm Control 126.0 171.0 45.0a 276.7 197.2 473.9aHydrolite 119.8 169.8 50.0a 252.0 93.4 345.5a

Geophile 119.4 181.2 61.8a 375.3 340.4 715.3a Glatco-Lite 117.2 172.8 55.6a samples destroyed in laboratory fire

Geophile 23.6 64.4 40.8a 121.6 69.0 190.5a Glatco-Lite 24.8 72.2 47.4a 105.3 88.6 193.9a 

Geophile 27.0 55.2 28.2bc 207.1 93.8 300.9bc Glatco-Lite26.4 56.6 29.4c 232.6 98.5 331.1c

1Value are the average of 5 determinations for the measurements,4 determinations for the biomass derteminations.Within species,mean separation is by the least significant difference test at the5%level

composting; Hydrolite is produce from composting dewatered biosolids and MSW. Source: Fitzpatrick,1989. 

Production time= 6 months for orange-jessamine and dwarf oleander, 12 months for Cuban palm

Dwarf oleander Control 26.6 50.0 23.4ab 140.7 49.4 191.1a Hydrolite 26.0n47.4 19.4a 143.8 84.0 227.7ab.

Av. height.cm Av.dry weight at end of production g

Orange-jessamine Conrol 19.6 60.2 40.6a 89.8 93.8 183.6a Hydrolite 25.0 73.4 48.4a 99.2 119.3 218.5a

Potential End Users

the soil and to increase the soil’s moisture-holding capacity. Compost also can be used as a top dressing and as a

mulch. The amount of compost used by the residential

sector depends on the ability of suppliers to consistently

produce a quality product at a reasonable cost. For example, only high-quality compost with low soluble salt concentrations should be used for home gardens (Rynk et al.,

1992). Such compost should have a goad earthy color and

odor and be free of clods. See Table 8-3 for a list of quality

requirements for the residential sector.

Homeowners are becoming increasingly familiar with the

composting of yard trimmings through community yard

trimmings collection programs and promotional backyard

composting campaigns. This familiarity encourages acceptance of yard trimmings compost as a high-quality prod-

. Developing residential markets for mixed

MSW-derived compost, however, might prove more difficult due to the reluctance of the residential sector to accept mixed MSW compost as a high-quality product.

In addition to product quality, other factors that affect the

quantities of compost used by the residential sector include

population growth, the economy and the housing indutstry Communities that have a large percentage of singlefamily homes typically have a higher demand for soil

amendments than areas of high-density housing (EPA,

1993).

Summary

c

ompost provides a stabilized form of organic

matter that improves the physical chemical

and biological properties of soils. It is currently

used by a wide range of end users, including commercial industries (e.g., agriculture, landscaping

horticulture, and silviculture), public a agencies, and

private citizens. There is great potential for expanding these end-use markets. To market compost successfully,yard trimmings and MSWcomposting facilities

must learn the specific requirements of potential endusers for quality composition, appearance, availability and price of the product.

 esearchers at the University of Florida conducted an experiment using mixed 

dium for plains. The plants used in the experiment—the Cuban royal palm, orange jessamine, and dwarf oleanderare grown commercially in tropical and subtropical climates, primarily for landscaping. The study found that the

growth rates of the palm and jessamine grown in mixed MSW compost were not significantly different than those grown

in the potting mix used as a control medium; the oleander performed better in mixed MSW composts than in the control

soil (see table below). The study concluded that the mixed MSW composts were no better or worse in terms of plant

growth than the commercial potting mix, which is sold for $35 per cubic yard.

Growth of Three Tropical Landscape Crops as influenced by MSW-Growing Media
Potential End Users

Chapter Eight Resources

Alexander, R. 1991. Sludge compost use on athletic fields.

BioCycle. July, 32(7):69-70.

Cal Recovery Systems (CRS). 1989. composting technologies, costs, programs, and markets. Richmond, VA:

U.S. Congress, Office of Technology Assessment. As cited

in: U.S. Congress, Office of Technology Asessment.

1989. Facing America’s trash: What next for municipal

solid waste? OTA-0-424. Washington, DC: U.S. Government Printing Office.

Cal Recovery Systems (CRS). 1988. Portland area compost products market study. Portland, OR: Metropolitan

Service District.

Chancy, R.L. 1991. Land application of composted municipal solid waste Public health, safety, and environmental issues. p.61 -83. As eked in Shirahpour et al.,

1992. Uses and benefits of municipal solid waste compost. Biomass & Bioenergy. Tarrytown, NY: Pergarnon

Press. 3(3-4):267-279.

composting Council (CC). 1992. Quarterly Newsletter.

October. Washington, DC: composting Council.

Gouin, F.R. 1989. Compost standards for horticultural

industries. BioCycle. August, 30(8):42-48.

Gouin, F.R. 1991. The need for compost quality standards. BioCycle. August, 32(8):44-47.

Hoitink, H.A.J., and P.C. Fahy. 1986. Basis for the Control of Plant Pathogens with Compost. Annual Review of

Phytopathology. Vol. 24:93-114.

Hoitink, H.A.J., Y. Inbar, and M.J. Boehm. 1991. Status

of compost-amended potting mixes naturally suppressive

to soilborne diseases of floricultural crops. Plant Disease.

November, Vol. 75.

Kashmanian, R. 1992. composting and Agricultural

Converge. BioCycle. September, 33(9):38-40.

Kashmanian, R.M., H.C. Gregory, and S.A. Dressing.

1990. Where will all the compost go? BioCycle. October,

31(10):38-39,80-83.

Mays, D.A., and P.M. Giordano. 1989. Landspreading

municipal waste compost. BioCycle. March, 30(5):37-39.

Mecozzi, M. 1989. Soil salvation. Wisconsin Natural Resources Magazine. PUBL-SW-093-89. Madison, WI: Department of Natural Resources, Bureau of Solid and

Hazardous Waste Management.

Rynk, R., et al. 1992. On-fare composting handbook,

Ithaca, NY: Cooperative Extension, Northeast Regional

Agricultural Engineering Service.

Shiralipour A., D.B. McConnell, and W.H. Smith. 1992.

Uses and benefits of municipal solid waste compost.

Biomass & Bioenergy. Tarrytown, NY: Pergamon Press.

3(3-4):267-279.

Slivka, D.C. 1992. Compose United States supply and

demand potential. Biomass & Bioenergy. Tarrytown, NY:

Pergamon Press. 3(3-4):281-299.

Spencer, R, and J. Glenn. 1991. Solid waste compacting op

erations on the rise. BioCycle. November. 32(11):34-37.

U.S. Congress, Office of Technology Assessment. 1989.

Facing America’s trash: What next for municipal solid

waste? OTA-0-424. Washington, DC: U.S. Government

Printing Office.

U.S. Environmental Protection Agency (EPA). 1993.

Markets for compost. EPA1530-SW-90-073b. Washington, DC: Office of Policy, Planning and Evaluation; Office of Solid Waste and Emergency Response.

9 7
1

Chapter Nine

Product Quality

and Marketing

Marketing plays a critical role in any composting operation. It is important to identify end users for the

compost product early in the planning stages of a compost facility since a customer's requirements will

have a significant impact on the dessign and operation of the facility This chapter provides information

about the quality of compost that can be expected from yard trimmings and MSWcomposting programs. It also

discusses the importance ofspecifications and testing when marketing a compost product. In addition, this chapter examines the factors that must be considered when attempting to tap into identified markets, including market assessment, pricing distribution, user education, and public education.

Product Quality

Consistent and predictable product quality is a key factor

affecting the marketability of compost. Each compost user

has different requirements for quality, however. These requirements must be understood and planned for when designing a composting system so that compost quality can

be matched to a user’s specific requirements. For example,

certain end uses of compost (e.g., application to crops) require the production of a high-quality product that does

not pose threats to plant growth or the food chain. Other

uses of compost (e.g., landfill cover) have less rigorous requirements (Section 8 discusses various end uses of compost). Some of the key concerns about the potential risks

of composted yard trimmings and MSW are discussed in

this chapter. It should be noted, however, that although

the potential risk associated with biosolids compost has

been extensively studied, less is known about mixed MSW

composts. More studies and field demonstrations are necessary to address research gaps concerning potential environmental and health effects of MSW-derived compost.

Yard Trimmings Compost Quality

Compost derived from yard trimmings contains fewer nutrients than that produced from biosolids, livestock manure, or MSW (Rynk et al., 1992); at the same time, it

contains fewer hazardous compounds and other contaminants than compost derived from biosolids, manure, or

MSW (see below). Nevertheless, concerns about the presence of heavy metals (e.g., lead, Cadmium, zinc, copper,

chromium, mercury, and nickel) and pesticides in finished

yard trimmings compost could affect its marketability.

In general, the levels of heavy metals in MSW compost

made from yard trimmings are well below those that cause

adverse environmental and human health impacts

(Roderique and Roderique, 1990). Table 9-1 shows data

on heavy metal content in yard trimmings compost from

two facilities. The content of heavy metals in the compost

varied, but in all cases was below soil concentrations of

trace elements considered toxic to plants, as well as the

maximum levels established in Minnesota and New York

for co-composted MSW and municipal sewage biosolids

(Table 9-2).

Yard trimmings compost also might contain pesticide or

herbicide residues as a result of lawn and tree spray application, High levels of these chemicals could result in a

phytotoxic compost (a compost that inhibits or kills plant

growth). Generally however, pesticides tend to have a

stronger attraction to roots and soil than to yard trimmings. In addition, pesticides and herbicides that are

found in yard trimmings feedstock are usually broken

down by microbes or sunlight within the first few days of

composting (Roderique and Roderique, 1990). This is

supported by several recent studies.

A 1990 study found low levels of four pesticides (captan,

chlordane, lindane, and 2,4-D) in leaf compost; all levels

were below U.S. Department of Agriculture tolerance levels for pesticides in food (Table 9-3). LoW levels of pesticides also were found in yard trimmings compost in

Portland, Oregon, in 1988 and 1989 (Hegberg et al.,

98
Chapter 4).

Uniform particle size of less than 1/2 inch in diameter Dark color and earthy odor Moisture contebt below 50 percent.

Cadmium (ppm) ND <0.5 10

Lead 31.7 102.7 250

Chromium 10.5 33.6 1,000

Cobalt 4.2 NS

Beryllium 15.0 NS

Sodium 1.51 0.02 NS

Aluminum 3.38 0.66 NS

 Compost Product quality depends upon the biological, chemical, and physical characteristics of the material. Some of the most desirable characteristics include:

 and stabilized). High organic matter content. Absence of viable weed and crop seeds, pathogenic organisms, and contaminants (such as bit of glass plastic, and metal).

Proper pH for the designated end use (usually between 6.0 and 7.8)

Low or undetectable levels of heavy metals and toxic organic componds.

Product Quality and Marketing

 Absence of visual, noncompostable contaminants

such as pieces of glass or plastic (Rynk et al., 1992;

CRS, 1990).

 It is important to note that storage practices can influence the quality of MSW and yard trimmings compost that is eventually marketed to end users. If piles

of compost are not kept dry and aerated, anaerobic

conditions prevail and odors and harmful anaerobic by-products will result (Rynk et al., 1992) (see

1991) (see Table 9-4). The chlordane concentration in

the Portland compost were believed to be a result of termite treatment around houses. Because chlordane is now

banned from general use, the presence of this compound

in compost should decrease in the future. The pentachlorophenol concentrations might be due to treatment of

outdoor wood such as fenceposts. Preliminary studies

conducted in Portland have shown that the presence of

these compounds does not interfere with seed germination or plant growth (Hegberg et al., 1991).

As these studies indicate, levels of heavy metals and pesticide residues detected in yard trimmings compost have

generally been insignificant. Nonetheless, compacting facilities should test their product for these and other variables (including soluble salts, viable weed seed, and

pathogens), as described later in this chapter.

MSW Compost Quality

In order to market MSW compost successfully to many

end users, concerns about potential threats to plants, livestock wildlife, and humans must be addressed. One of

the primary concerns is the presence of heavy metals (particularly lead) and toxic organic compounds in the MSW

compost product, To date, where problems have occurred

with MSW compost, they have resulted from immature

composts, not metals and toxic organics (Chancy and

Ryan, 1992; Walker and O’Donnell, 1991). Manganese

deficiency in soil and baron phytotoxicity as a result of

MSW compost application ears be potential problems,

however. Nevertheless, measures (including effective

source separation) can be taken to prevent all of these

problems and produce a high quality compost.

Heavy Metals and Organics

The bioavailability of contaminants in MSW compost describes the potential for accumulation of metals or organics in animals from ingested compost, or from

food/feed materials grown on compost-amended soils.

While research on the ingestion of MSW compost has

only begun recently, field studies on biosolids and MSW

Table 9-1. Heavy metals in yard trimmings compost.

Croton Montgomery

Heavy Pointr New County, Metals York Marylanda Standardb

Nickel 10.1 200

Copper 19.1 35.5 1,000

Zinc 81.6 153.3 2,500

Manganese 374.0 1,100. 0 NS

Titanium (%) 0.09 NS

Ferrous 2.67 0.96 NS

aAverage of 11 samples, 1984-1985.

b

For pesticides, standards are derived from USDA tolerance levels for

pesticides in food (40 CFR Chapter 1, Part 180). Far metals, standards

are Class 1 Compost Criteria for mixed MSW compost, 6 NYCRR Part

60-5-3.

Source: Roderique and Roderique, 1990.

99
Mercury 5 10 Nickel 100 200 PCB 1 1 Zinc 1,000 2,500

 Heavy Metals Crotoa Point, New York Montgomery Count Maryland Standard

Contaminant Minesota New York Cadmium 10 10

Chromium 1,000 1,000 Copper 500 1,000 Lead 500 250

Captan 0.0052 0.05-100 Total 0.0932 <1.0 0.03

Chlordane Lindane 0.1810 1.00-7.00 Total 2,4 -D 0.0025 <1.0 0.05-1.00

Product Quality and Marketing

Table 9-2. Contaminant Limits for MSW compost (mg/kg).

Source: Hegberg et al., 1991.

composts suggest that a small percentage of metals in

compost-amended soil are bioavailable to plants and other

organisms.

The bioavailability of lead in mixed MSW compost is of

concern to some end users. Lead can present a potential

risk to children who inadvertently ingest compostamended soil. A study that examined the levels of heavy

metals in MSW compost from five operating facilities

found somewhat higher lead levels in MSW composts

than the median level in biosolids (Walker and O’Donnell, 1991). Studies are necessary to determine if the

bioavailability of this lead is reduced because of binding

with hydrous iron oxide and phosphate in sewage

biosolids compost. Based on available research, Chancy

and Ryan (1992) conclude that lead concentrations in

mixed MSW compost products should be limited to 300

mg/kg. MSW compost prepared from MSW separated at

a central facility often contains lead concentrations of 200

to 500 mg/kg. Source separation of products containing

lead should help reduce the concentration of lead in the

compost product (see below). Diverting these materials

from the MSW stream in the first place (through household hazardous waste collection programs) should further

help reduce the level of lead in compost.

Researchers also have been concerned with food chain and

dietary risks posed by another heavy metal, cadmium. AS

a result of research on cadmium risk conducted during recent years, it can be concluded that uncontaminated

biosolids and mixed MSW composts pose no cadmium

risk, even in extremely worst-case risk scenarios (Chancy

and Ryan, 1992). Research also indicates that the

bioavailability of cadmium is low, even in acidic soils. In

general, absorption of heavy metals by plants increases if

the soil is acidic (i.e., pH 7.0). In addition, because zinc

(which is found along with cadmiun in biosolids and

MSW composts) interferes with cadmium uptake by

plants, mixed MSW compost is even less likely to

contribute cadmium to human and animal diets via plants

(Chancy, 1991).

It should be noted that heavy metals also appear to become less soluble (therefore less bioavailable to plants)

over time during full-scale mixed MSW composting. If

the composting process is performed properly, metals become bound to humic compounds, phosphates, metal oxides, etc. in the compost and stay bound when mixed

with soil (Chancy, 1991).

Toxic organic compounds, including polychlorinated

biphenyls (PCBs), polycyclic aromatic hydrocarbons

(PAHs), and polychlorinated aromatics (PCAs), are potential concerns with MSW compost. Research has shown

that PCBs are quite stable in the presence of both natural

soil bacteria and fungi (Nissen, 1981); therefore, any

PCBs that do find their way to the feedstock will most

likely be present in the compost. The concentration of

PCBs in MSW compost has been found to be low, however. PAHs are another potential concern in MSW compost, degrading to acids that contribute to the

phytotoxicity of unstable composts. PCAs also can pose

some risk. While they have been found to bind to the organic fraction of compost, little information is available

regarding their availability to organisms in the compost

product (Gillett, 1992). More studies are needed to better

determine the risks posed from toxic organic compounds

in MSW compost.

Boron Phytoxicity

MSW compost contains substantial levels of soluble boron

(B), Which can be phypotoxic (Chancy and Ryan, 1992).

Much of the soluble B found in MSW compost is from

glues, such as those used to hold bags together (Volk, 1976).

Table 9-3. Pesticides in yard trimmings compost.

aAverage of 11 samples, 1984-1985.

bFor pesticides, standards are derived from USDA tolerance levels for

pesticides in food (40 CFR Chapter 1, Part 180). For metals, standards

are Class 1 Compost Criteria for mixed waste compost, 6 NYCRR Part

60-5-3.

cAverage of 2 samples.

Source: Roderique and Roderique, 1990.
16 16 16 16 16 16 14 16 14 0 0 0 0 0 0 0 0 9

Pentachlorphosphates

of

2 4 1 0 0

4

Product Quality and Marketin g

Table 9-4. Pesticide analysis of Portland, Oregon, yard trimmings compost.

Number Samples Above

Pesticide Detection Meanc Rangec

Classification Residue Samples 2 Limitb

(mg/kg) (mg/kg)

Chlorophenoxy

herbicides

Chlorinated

Hydrocarbons

OrganoMiscellaneous

2,4-D

2, 4-D8

2,4, 5-T

silvex

MCPA

MCPP

Dichloroprop

Dicamba

phenol

Chlordane

DDE

DDT

opDDT

ppDDT

Aldrin

Endrin

Malathion

Parathion

Diazinon

Dursban

Dieldrin

Trifluralin

Dalapon

Dinoseb

Casoron

PCBs

19

14

14

14

16

16

16

14

14

14

15

13

10

5

8

8

17

3

0

0

0

0

1

NDd

ND

ND

ND

ND

ND

0.229

0.187

0.011

0.005

0.016

0.007

ND

ND

0.019

ND

0.129

ND

0.001-0.53

0.063-0.370

0.005-0.019

0.004-0.006

0.002-0.035

0.007

0.039

0.019

0.129

a. The number of samples is the combined total for 2 sources of compost, which were sampled in June

1988, October 1988, Apti/ 1989, July 1989 and October 1989. The number of samples taken each time

was not uniform (mostly 2 per period per source in 1988 and 1 per period per source in 1989).

b. The minimum detection limit is 0.001 ppm for pesticides and 0.01 ppm for PCBs.

c. Dry basis.

d. Not detectable (ND),

e. Residue detected but not measureable.

Source: Hegberg et al., 1991.

In general, B phyroxicity has occurred when MSW com- (de Haan, 1981). Whether Mn deficiency will occur when

post was applied at a high rate to B-sensitive crops (e.g., mixed MSW compost is applied to soil depends on such

beans, wheat, and chrysanthemums). It appears to be .

factors ax . .

more severe when plants are deficient in nitrogen, when

low humidity conditions are present, or when a great deal

of transpiration occurs (e.g., as in greenhouses) (Chancy

and Ryan, 1992). Because soluble B is more phytotoxic to

acidic soils, liming can correct the problem. In addition, B

phyrotoxicity has been shown to be short lived; it seems to occur only in the first year of application (Chancy and Ryan,

1992).

Manganese Deficiency

■

Mixed MSW compost has been found to cause a lime-in- n

duced manganese (Mn) deficiency in soils in some eases

The pHof the soil- Mixed MSW compost usually

raises the pH of soil; when it is added to naturally

low Mn acidic soils, the resultant high pH can

cause Mn deficiency.

The susceptibility of the crop - Crops that are susceptible to Mn deficiency include soybeans and wheat.

The clay content of the soil - Mn concentration appears to increase with increasing clay content.

The height ofthe water table - Soils that have been

submerged during formation leach Mn and are

101
Lead 800 700

I

Product Quality and Marketing

more susceptible to Mn deficiency (Chancy and

Ryan, 1992).

MSW compost producers need to consider the potential

of mixed MSW compost to induce Mn deficiency, particularly if soils or crops in the area that the compost will

be marketed are susceptible to Mn deficiency. If necessary,

Mn can be added during composting to ensure that Mn

deficiency does not occur.

The Effect of Source Separation

Many researchers support the use of source separation (see

Chapter 3) to remove recyclable and nonrecyclable/noncompostable components from the compostable components. Source separation is key to reducing the heavy

metal and visual contaminant concentrations in the finished compost. In a four-season discard characterization

study in Cape May, New Jersey, at least 86 percent of metals found in MSW were attributable to noncompostable

materials (plastic, wood, aluminum and tin cans, household batteries, etc.) (Rugg and Hanna, 1992). Another

study examined the influence of preprocessing techniques

on the heavy metal content in MSW compost. Looking at

the level of heavy metals in finished compost and at different separation techniques, the study concluded that finished compost contained the lowest levels of zinc, lead,

copper, chromium, nickel, and cadmium when source

separation occurred (see Table 9-5). In practice, however,

it might be very difficult to remove many of the materials

containing heavy metals. Extensive separation once these

materials have been mixed with organics can be very

costly.

Product Specifications

Developing and utilizing appropriate compost product

specifications ensures that high-quality compost will be

produced. Specifications can be established for a number

of parameters, including organic matter content, particle

size, nutrient content (especially carbon-to-nitrogen ratio), presence of toxic compounds, nontoxic contaminant

levels, concentration of weed seeds, seed germination and

elongation, soluble salts, color, odor, and water-holding

capacity (EPA, 1993).

All of these characteristics are critical to buyers. For example, high moisture content means customers receiving

bagged compost receive bagged water as well. Particle size

affects aeration, drainage, or water-holding capacity. The

compost’s pH, nutrient concentrations, or heavy metal

concentrations restrict its usefulness for certain plants. If

the compost is not stable, storage will be difficult and

might affect the compost quality, Compost stability also

has an impact on plant growth. Finally presence of visible

noncompostable contaminants might influence the

buyer’s perception of quality.

Table 9-5. Heavy metal concentrations in MSW-derived

compost.

Processing method (mg/kg dry weight)

Metal A B c D

zinc 1,700 800 520 230

420 180

Copper 600 270 100 50

Chromium 180 70 40 30

Nickel 110

Cadmium 7 2.5 1.8 1.0

A. Mixed household Waste are composted without preparation. the

process takesapproximately 12 month. After composting, the product is screened and insert are removed.

B. The collected household waste are separated into two fractions.The material container most the easily degradable organic material.

between two and-a-half and five months are needed for this

composting process.

C. The collected waste are shredded, then processsed,resulting in a

fraction to be composted. This fraction is free of most inerts, such as

glass and plastics.

D. Wastes are separated at the source. The organic components are

collected separately at households. All necessary steps are taken to

insure that components Containing heavy metals do not enter the

organic components.

Source: Oosthnoek and Smit, 1987.

Uniform product specifications have not been developed

for compost. A few states, however, have developed specifications and regulations for yard trimmings and MSW

compost (see Chapter 7 for more information on legislation). During the planning stages of a composting facility,

communities should determine what regulations and

specifications, if any, have been established in their state.

Specifications of bordering states also could be investigated in order to expand marketing options. Where a state

has not established specifications, minimum acceptable

product standards should be determined based on anticipated end uses.

The final compost product should exhibit the characteristics that are important to the customer. Prospective

clients also can be provided with samples of the compost

product and specification sheets listing the parameters

tested and the results of the tests (a sample specification

sheet is shown in Figure 9-1).

Product Testing

To ensure product quality, the compost product should be

laboratory tested frequently, Many environmental laboratories test compost. A composite sample, composed of

many small samples from different locations in the curing

piles, will provide the most representative result.

102
Zinc 929.0 PCBs 4.6 Source: Rahrbach, 1989

of Commerce were used to compile the list of potential end users. Twenty-twi end users returned the questionaire; these individuals were then personlly interview

Average Concentration of Essential Plant Nutrients (in perecnt) Kjeldahl Nitrogen (TKN) 1.40% 

Phosphorus 1.56% Potas 0.30%h

Average Heavy Metal and PBC Concentrations(in microorganism/g, dry weight basis) Cadmium2.9 Copper 332.0

Lead 499.0 Mercury 4.6 Nickel 449.0

over 130 potential users in a 15- mile radius of the proposed compost facility site. Data from local Chambers

Identified market development activites such as field and laboratory testing tailored to local end-user requirements. To identify end users, a questionnair

Reviewd compost products' chemical and physical characteristics and related these to the various end uses to applicable regulations.

Identified end-user specific requirements such as transportation, chemical and physical specifications, product pricing, application considerations, demand seasonab

MSW. Through the assessment, the county accomplished the following: Projected total county demand for compost products. 

In Wright County, Minnesota, a product end-use market assessment was conducted as part of the county's plans to develop a state of the art composting facility to ma

A Successful Market Assessment for MSW Compost in Wright County, Minnesota

Product Quality and Marketin g

Figure 9-1. Sample specifications sheet.

Among the tests most commonly conducted are those

that determine the concentration of plant nutrients and

toxic compounds. The compounds that are tested for will

depend on the feedstock and any applicable regulations.

Facility managers should be aware of possible heavy metal

contamination in mixed MSW compost, or other contaminants introduced by specific sources. Some facilities

also test for maturity and stability (by using growth

germination tests and root lengths). The present of weed

seeds and phytotoxic compounds also should be monitored. Respiration rate determinations indicate the rate of

decomposition to be expected; a reduction/oxidation test

that measures aeration status of the compost can predict

odor problems. Some composts actually suppress soilborne plant diseases, and that possibility should be assessed as well (see Chapter 8). The laboratory equipment

requirements for tests of moisture content, pH, and particle size are minimal; an outside laboratory will be needed,

however, to determine characteristics such as nutrient and

heavy metal concentrations. Larger facilities perform respiration rate tests in house smaller facilities will need to

seek an outside laboratory. Finally, as an added selling

point to potential users, field tests can be conducted,

often by university staff or extension specialists at land

grant schools, to demonstrate product utility and

effectiveness.

It would be useful to carefully record the test data (on a

computerized spreadsheet, if possible) to facilitate any reporting requirements that might have to be met and to

provide a basis for comparing information collected over a

long period of time. In this way, subtle changes in compost quality or properties can be observed.

Market Assessment

The best way to identify end users for a product is

through a market assessment. The market assessment pinpoints potential consumers, along with their product requirements. Conducting this assessment in the early stages

of the planning process and using the data as the basis for

program design will increase the likelihood of widespread

use of the final compost product and long-term stability

of the composting program. In addition, a market assessment can estimate potential revenues from the sale of the

compost. While the sale of compost is in general not a

highly profitable activity, any revenues earned can help

offset the cost of processing. Estimating revenues is also

important in determining what equipment will be needed

and what the facility’s total budget will be. Figure 9-2 provides a sample market assessment form.

Once the market assessment is performed, potential users

must be turned into real compost users. Many Factors affect this transformation. The product must be priced,

103
Product Quality and Marketing

Company Name

contact Person

Address

Phone Number

Type of Business

1. If you use or sell any of the materials Iisted below, please indicate the amount used or sold an an annual basis,

 as well as the cast per ton.

Product Used Amount Used (in tons) Amount Sold (in tons) cost Per Ton

Composted manures

Fresh manure

Sewage sludge compost

Mushroom compost

Peat

Loam

Organic fertilizers

Topsoil

Potting soils

Custom soil mixes

Bark mulch

Wood chips

2. At what percentage are your annual needs for the above items increasing or decreasing?

3. What are your current terms of purchase?

Figure 9-2. Sample market assessment farm.

104
Product Quality and Marketing

4. If yard waste or MSW compost were available in quantity on an ongoing basis, how much would you purchase?

would the purchase terms differ from your current terms?

5. Under what conditions would you be prepared to negotiate a purchase agreement for compost?

6. What are your concerns when purchasing a compost product (for example, odor, price,

nitrogen/phosphorus/potassium, fineness, packaging)?

7. When are your peak demands?

8. What are your transportation/delivery needs?

9. Would you be prepared to guarantee acceptance of a minimum quantity of Compost?

Additional comments:

Please return to:

J. Compost Farmer

100 Dairy Road

Poultryville, MA 00000

Adapted from: Rynk et al., 1992.

Figure 9-2. (Continued).
centers, and home owners for use as a potting soil, a sol amendment, or a mulch for water retention and weed control, and was also used to cap landfills (Mea

St. Cloud, Minnesota Mixed MSW and Biosolids Farm Fields,Landscapers None or $4 per yard $20 per ton

New Castle County, Delware Mixed MSWand Biosolids Landscapers, Horticulture $4.50 per yard

Skamania, Washington Mixed MSW Homeowners $5-10 per yard Montgomery County, Maryland Yard Trimmings Landscapers, Nurseries $19.20 per ton

Seattle, Washington Yard Trimmings Landscapers, Residents,City/County $7.50-12.50 per yard 

Some facilities build a customer base by giving away compost. Middlebush Compost, Inc has been composting leaves in Franklin Township, New Jerse

able to sell all of their product at $10 per cubic yard screened and $6 peer cubic yard unscreened. the compost was sold to landscapers, developer, nuserie

since early 1987. At first, in order to establish markets, the company gave the product away as part of its marketing campaign. By the end of 1989, they 

Product Quality and Marketin g

sold, and distributed, and the buyers must be educated so

they can optimize their sales efficiency.

Private vs. Community Marketing

Communities ears market compost themselves or rely on

private companies that are in the business of marketing

compost. Private marketers can advertise the product by

attending trade shows, field demonstration days, and other

events, developing a good public relations campaign;

suggesting appropriate equipment for handling the compost

and pricing the compost competitively

Municipalities also can perform all of these functions, but

this might put a burden on available resources. Some

communities find that the revenues received from marketing compost can offset administrative and promotional

costs. Others find, however, that they do not have the inhouse marketing expertise or a suitable infrastructure to

administer a program and thus choose to enlist the services of a professional marketing company.

Communities that opt to market the compost themselves should check whether they have the legislative

authority to market compost products. Cities with their

own programs also enter into the sensitive area of competing for business in the private sector. Municipal employees who sell compost to markets such as chain

stores and nurseries can be at a disadvantage compared

to salespeople who work for private firms, especially in

terms of flexibility in dealing with potential customers.

Another approach to marketing compost that is becoming

increasingly popular is to market the product through a

broker (CRS, 1990). The broker buys the compost at

a low price and takes responsibility for product testing,

compliance with regulatory constraints, and promotion.

A compost broker in the Northeast buys compost from

a number of municipalities in the region and resells it to a

network of landscapers and major topsoil users.

Pricing

A number of factors play a role in determining the final

price of the compost product, including compost quality and availability the cost of the composting

program; costs of transportation, production, marketing, and research and development the price structure

of competing products; and the volume of material

purchased by an individual customer. Since the main

objective of marketing is to sell the compost that has

been produced, the price of the compost should be set

to help achieve this. A logical strategy is to price the

product modestly at first to establish it in the marketplace and then increase the price based on demand.

Table 9-6 provides examples of prices established for yard

trimmings and mixed MSW compost.

Several communities have not charged for compost in

order to increase community awareness of the benefits

of compost. Providing compost free of charge also promotes good will in a community and is an effective way

to find commercial users who might be willing to try the

Table 9-6. Prices received for compost.

Facility or Community Materials Composted Market Price

Portage, Wisconsin Mixed MSW and Biosolids City-Owned Industrial park $8 per Yarda

Sumter County, Florida Mixed MSW Nurseries, Sod Farms Planning on $9-12 per yarda

Sources: aGoldstein and Spencer, 1990; bTayIor and Kashmanian, 1989.

106
ost Distribution The Greater Cleveland Ecological Association operates six facilities for composting yard trimmings andserves 16 communities in Cleveland, Ohio.

ng their own containers (bags or bushels) to the composting site; the cost is $0.75 per bushel. Customers pick up bulk loads of compost at the 

nursery stock. The compost has sold out every year.

composting site. Customers' truck are loaded for

ompost is bagged in 1 cubic yard plastic bags. These are sold through distributors who deal with the nursery and landscaping industries. 

given for semi-truck loads delivered to landscapers and commerical growers to encourage the use of compost on lawns and in potting media for 

Product Quality and Marketing

product. Some experts warn against “giveaway” programs,

however, because these can give the impression that the

compost has no value. Many recommend charging at least

$1 per cubic yard to associate value with the product.

Some communities charge a nominal fee to bulk users

and nonresidents but give the product free to residents.

Other communities charge residents a small fee. In

Cleveland, Ohio, the Greater Cleveland Ecological Association, which serves 16 communities and composts

approximately 250,000 cubic yards of leaves each year,

sells compost to residents. Discounts might be given for

large-volume buyers and for early payment. The pricing

structure and whether to give the compost away are determinations that should be made on a community by

community basis, depending on the amount of material

available, its quality, and the opportunities for use

(Mielke et al., 1989).

Location/Distribution Issues

Market location is of key importance for both product acceptance and transportation issues. Generally, the price of

compost does not cover the cost of transportation over

long distances (EPA, 1993). In most eases, therefore, the

market for compost is within 25 or 50 miles of the

The association sells compost in the following ways:

$13.50 per cubic yard.

● Compost is home delivered. There is a 2 cubic yard

minimum, which is sold for $55.10, and a 10 cubic

yard maximum, which is sold for $178.30. These

prices include delivery and taxes. There is art additional charge of $20 for out-of-county delivery.

composting facility (Rynk et al., 1992). Proximity to composing facilities promotes trust in the product through

name recognition, increases buyers’ access to the product,

and enables the compost to be sold at a competitive price

due to low transportation costs. Bagging the compost

product can expand the potential market area. While bagging requires a higher capital investment in machinery

and bags, the bagged product sells at a considerably higher

price than most bulk compost. The higher price might

justify higher transportation costs and, therefore, a larger

market area (Rynk, et al., 1992). Municipalities are usually better off selling in bulk.

The cost of transporting compost also depends on its

weight and bulkiness. Many compost products are marketed only locally because the bulkiness of the compost

(400 to 600 kg/m3 [700 to 1,000 lb/yd3

]) makes transportation expensive. Communities need to monitor available

transportation funds carefully during facility planning

stages so that the distance between potential markets and

the manufacturing facility can be set accordingly.

Distribution systems for compost are diverse and often

creative. A system should be developed based on a survey

of the needs of the potential users. Most compost is distributed in the following ways:

Direct retail sale or free distribution of bulk compost by truckload or in small quantities on site.

Direct sale or free distribution of bagged compost

on site or at special distribution centers.

Direct sale or free distribution to wholesalers for

processing in bulk or in bags to retailers (EPA,

1993).

Municipalities that perform composting should examine

their own public sector markets and determine how much

money is spent annually on fertilizer, top soil, and other

soil amendments by governmental agencies in the region.

A fair amount of demand often can be created internally

by passing procurement ordinances specifying recycled

materials. For example, bid proposals could require that

the topsoil used for land reclamation contain a minimum

level of compost.

Many facilities rely on local residents to transport the

compost from the composting site. This approach is not

always successful, as most residents can transport and use

compost only in small quantities. Residential users also

prefer bagged compost. Bagging requires additional investment in capital costs, which in turn requires higher

pricing. A successful marketing program for bagged compost requires a high-quality product and intensive advertising to overcome price competition from competing

products.

107
oducing more th one productcan alleviate shortfalls during peak demand periods,thereby improving distribution and reducting the amount of storage space required.

oth yard trimmings and MSW composting operations,producing a variety of product broadens the potential market base, increasing the amount of

Product Quality and Marketing

Producing several products from the feedstock also

can contact the Cooperative Extension Service to assist

them in marketing finished compost to area farmers.

Throughout the marketing process, it is critical to present

the compost as a usable product, not as a waste material

that must be disposed of. It is imperative to realize the importance of a positive attitude and how contagious enthusiasm can be when presenting ideas on the uses of

compost (Tyler, 1992). A positive approach can help reduce the potential stigma that users might assign to certain types of compost and promote acceptance of compost

. , , ,

guards against generating an oversupply. Several grades in the marketplace.

of compost products (that would be significantly different in chemical or biological properties) could be

manufactured by segregating portions of the feedstock.

For example, a facility could offer soil amedmentgrade and potting media-grade composts.

If such segregation is not possible, the compost pro

duced at the facility could be modified to make several

grades of compost. For example, the compost’s nutrient properties could be supplemented, the pH adjusted

to suit different market needs, or the particle size could

be varied by using coarser or finer screens to manufacture a rough-grade and a fine-grade compost. Wholesalers and retailers of compost sometimes add other

ingredients, like lime or sand, for special uses or markets. The costs of these options will vary according to

region.

Education and Public Relations

The results of a marketing study carried out in Port-

 land, Oregon, indicate that the quantity of compost

used by residents is largely a function of public education and the capability of a facility to produce a highquality product consistently (CRS, 1988). It is therefore

important to work closely with potential end users to

educate them about the product’s benefits and how it

should be used.

Product credibility as recognized by an independent third

party could help improve sales. Communities can obtain

several independent expert opinions to assure the user of

the benefits of the product. These might include a representative of a university, an extension service, an agricultural experiment station, or even a large greenhouse,

nursery, or farmer who has used the product and is willing

vouch for it. Landscape or nursery associations might provide opportunities for composting facility representatives

to speak at monthly meetings and offer educational information to their members. Once educational material is

developed, the involvement of an educational network is

vital (Tyler, 1992). The United States Department of

Agriculture offers an educational program to farmers

through the Cooperative Extension Service; communities

108

Updating the Market Assessment

Marketing requires continuous effort and does not stop

once end users are secured. End users must become repeat

customers if there is to be continued success of a marketing strategy. Monitoring of the marketplace is necessary to

determine if all of the compost produced is being distributed, if users are satisfied with the product, and if the

publicity strategies being employed are effective. Re-surveying potential users to determine whether they are now

willing to use the compost is beneficial, as is updating the

market assessment to identify any new market that might

have emerged since the last survey. Ongoing marker surveys

allow customers to participate in program development. Understanding customers’ feelings and emotions paves the way

for building trust in the compost product (Tyler, 1992).

Summary

T

he marketing of compost should be undertaken

 

in the early stages developing the composting

facility in order to identifiy potential end users of

compost and quality of compost they demand This

will assist decision-makers in all facets ofplanning

from desiging the size of the facility to marking financial projections of revenues. Communities should

consider all aspects of marketing including packaging, distribution, and applicable regulations. Marketing can be conducted in house or through

marketing companies and brokers. Finally community officials should keep in mind the constant need

to gauge customer satisfaction and attitudes so that

potential problems can be isolated and solved before

they affect facility performance.

Chapter Nine Resources

Appelhof M., and J. McNelly. 1988. Yard waste composting Guidebook for Michigan communities. Lansing MI:

Michigan Department of Natural Resources.
Product Quality and Marketing

Cal Recovery Systems (CRS) and M.M. Dillon Limited.

1990. composting A literature study. Ontario, Canada:

Queen’s Printer for Ontario.

Cal Recovery Systems (CRS). 1988. Portland-area compost products market study. Portland, OR: Metropolitan

Service District.

Chancy, R.L., and J.A. Ryan. 1992. Heavy metals and

toxic organic pollutants in MSW composts: Research results on phytoavailability, bioavailability, Fate, etc. As cited

in. H.A.J. Hoitink et al., eds. Proceedings of the International composting Research Symposium. In press.

Chancy, R.L. 1991. Land application of composted municipal solid waste Public health, safety, and environmental issues. As cited in Proceedings of the Northeast

Regional Solid Waste composting Conference, June 24-

25, 1991, Albany, NY. Washington, DC composting

Council. pp. 34-43.

composting Council (CC). 1992. Personal communication. Washington, DC.

de Haan, S. 1981. Results of municipal waste compost research over more than fifty years at the Institute for Soil

Fertility at Haren/groningen, the Netherlands. Netherlands Journal of Agricultural Science. 29:49-61. As cited

in Chancy and Ryan, 1992. Heavy metals and toxic organic pollutants in MSW composts Research results on

phytoavailabllity, bioavailability, fate, etc. As cited in:

H.A.J. Hoitink et al., eds. Proceedings of the International composting Research Symposium. In press.

Gillett, J.W. 1992. Issues in risk assessment of compost

from municipal solid waste Occupational health and

safety, public health, and environmental concerns.

Biomass & Bioenergy. Tarrytown, NY: Pergamon pres.

3(34):145-162.

Goldstein, N., and B. Spencer. 1990. Solid waste composting facilities. BioCycle. January, (31)1:36-39.

Harrison, E.B., and T.L. Richard. 1992. Municipal solid

waste composting policy and regulation. Biomass &

Bioenergy. Tarrytown, NY: Pergamon Press. 3(3-4):127-

141.

Hegberg, B.A., W.H. Hallenbeck, G.R. Brenniman, and

R.A. Wadden. 1991. Setting standards for yard waste

compost. BioCycle. February 32(2):58-61.

Meade, K 1989. Waiting for the leaves to fall. Waste Alternatives. March: 34-38.

Mielke G., A. Bonini, D. Havenar, and M. McCann.

1989. Management strategies for landscape waste. Springfield, IL: Illinois Department of Energy and Natural Resources, Office of Solid Waste and Renewable Resources.

New York Legislative Committee on Solid Waste Management. 1992. Earth for sale: Policy issues in municipal

solid waste composting. Albany, NY

Nissen, T.V. 1981. Stability of PCB in soil. As cited in:

M.R. Overcash, ed. Decomposition of toxic and nontoxic

organic compounds in soil. Ann Arbor, MI: Ann Arbor

Science Publishers, pp. 79-87.

Oosthnoek, J., and J.P.N. Smit. 1987. Future of composting in the Netherlands. BioCycle. July 28(7):37-39.

Pahren, H.R. 1987. Microorganisms in municipal solid

waste and public health implications. Critical reviews in

environmental control. Vol. 17(3).

Portland Metropolitan Service District (PMSD). 1989.

Yard debris compost handbook. Portland, OR: PMSD.

Roderique, J. O., and D.S. Roderique. 1990. The environmental impacts of yard waste composting. Falls Church,

VA Gershman, Brickner & Bratton, Inc.

Rohrbach, J. 1989. Delaware Solid Wrote Authority New

Castle, DE.

Rugg, M., and N.K. Hanna. 1992. Metals concentrations

in compostable and noncompostable components of municipal solid waste in Cape May County, New Jersey. Paper presented at the Second U.S. Conference on

Municipal Solid Waste Management, Arlington, VA.

Rynk, R, et al. 1992. On-farm composting handbook.

Ithaca, NY: Cooperative Extension, Northeast Regional

Agricultural Engineering Service.

Selby, M., J. Carruth, and B. Golob. 1989. End use markets for MSW compost. BioCycle. November, (30)11:56-

58.

Smit, J.P.N. 1987. Legislation for compost in the Netherlands-Part II. As cited in de Bertoldi, M. et al., eds.

Compost: Production, quality and use. New York, NY:

Elsevier Applied Science.

Taylor, A., and R Kashmanian. 1989. Yard waste composting A study of eight programs. EPA1530-SW-89-038.

Washington, DC: Office of Solid Waste and Emergency

Response, Office of Policy, Planning and Evaluation.

Tyler, R 1992. Ground rules for marketing compost. BioCycle. July, 33(7):72-74.

U.S. Environmental Protection Agency (EPA). 1989.

Characterization of Products Containing Lead and Cadmium in Municipal Solid Waste in the United States,

1970-2000. EPA/530-SW-89-015B. Washington, DC:

Office of Solid Waste and Emergency Response.

U.S. Environmental Protection Agency (EPA). 1993.

Markets for compost. EPA/530-SW-90-073b. Washington, DC: Office of Policy, Planning and Evaluation, Office of Solid Wrote and Emergency Response.

109
Product Quality and Marketing

Volk V.V. 1976. Application of trash and garbage to agri- Walker, J.M., and M.J. O’Donnell. 1991. Comparative

cultural lands. pp. 154-164. As cited in Chancy and Ryan, assessment of MSW compost characteristics. BioCycle.

1992. Heavy metals and toxic organic pollutants in MSW August, 32(8):65-69.

composts: Research results on phytoavailability, bioavailability, fate, etc. As cited in: H.A.J. Hoitink et al., eds. Williams, T.O., and E. Epstein. 1991. Are there markets

Proceedings of the International composting Research for compost? Waste Age. April, 22(1):94100.

Symposium. In press.

110
Chapter Ten

Community

Involvement

D

ecisions involving solid waste management can generate considerable controversy among local residents,

who are concerned about the safety and health of their friends and family as well as the welfare of their local environment. Therefore, it is crucial local official to develop strong support among their constituents

whenever embarking on solid waste policy-making; planning a composting facility no exception. Local support

o fa composting operation determines the ease with which the facility can be sited and the willingness ofthe public to participate in the program. Decision-makers can involve the public by inviting constituent to participate

in many decisions surrounding composting facility siting design, and operation. In addition, an educational and

public relations program must be conducted to maintain citizen enthusiasm in the program once operation has

commenced

Planning the Composting Project

A well-run public information program can help generate

support for a composting program in the planning stages.

Local officials can undertake a publicity campaign to educate citizens and the media about how composting works

and why it can be an effective waste management strategy.

The publicity campaign can also point to the planned

composting program as a source of civic pride because it is

an indication that the community is environmentally

aware. Publicity techniques can include

Paid advertising - Television or radio ads, newspaper ads or inserts, magazine ads, outdoor ads.

Public service advertising - Radio announcements,

free speech messages, community calendar notices,

utility bill inserts.

Press coverage - Briefings, news conferences, feature

stories, press releases, press kits.

Non-media communications - Presentations to civic

organizations or schools, newsletters, exhibits/displays, mailings of key technical reports, promotional materials (brochures, door hangers, leaflets).

■ Odor- It is important to acknowledge that composting can generate odors, but that-steps can be

taken to minimize their impact on the surrounding

community (see Chapter 6).

 The portion of the waste stream that can be composted -

While as much as 30 to 60 percent of the MSW

stream could potentially be composted, composting is not a panacea for managing all that a community discards.

■ Costs of composting - The sale of compost will not

generate enough revenue to support all the costs of

a municipality’s composting program. It is the cost

savings from avoiding combustion or landfilling

and the beneficial reuse of materials that make composting financially attractive.

Once the public has been informed about composting in

general and about the proposed facility, the next step is to

provide avenues through which members of the public

can express their concerns. A variety of techniques are

available for soliciting feedback from members of the Public, including advisory groups/task forces, focus groups,

while promoting the benefits of composting the public telephone hotlines, public hearings, town meetings,

information program should also foster realistic expecta- referendums, interviews with people representing key

tions. Officials must provide honest and detailed informa- groups or neighborhoods, and workshops to resolve spetion about issues such as: -.colic “issues. Some of these techniques give community

111
Decisions

Community Involvement

members decision-making roles, while others give them

advisory roles or simply provide information. The degree

of decision-making authority might depend on what local

laws require (some require that all policy and budgetary

decisions be made by local officials) or what element of

the composting program is under discussion and if it is

controversial (for example, siting might require more

decision-making by members of the community than

details of processing technologies). Cornell University is

currently doing a study on this subject, supported by

funds from the Compost Council Research Foundation.

Commnity Involvement in Siting

Siting a composting facility can be a sensitive process for

solid waste managers and site designers. The search for

sites can be stalled by local residents who do not want a

Planning a composting Facility

Through Teamwork

D

isposing of fish scraps from processing plants was

a perennial problem for communities on the

Maine shoreline until a consortium of public and

private organizations found a solution through composting, The consortium included fish processors, the.

local water company the U.S. Department of Agriculture, and the Maine Departments of Transportation,

Environmental Protection, and Agriculture. By involving these groups in the planning process, adversarial relationships were minimized and a sense of joint

ownership of the project developed.

One of the first steps of the consortium was to develop

clearly stated goals. The groups also formed special action committees—management, budget and funding,

public relations, and research-to carry out important

tasks identified in the team planning sessions. The

publicity committee, for example, was charged with

addressing the concerns of local residents about composting. The committee developed a slide show for the

public that depicted the process and benefits of largescale composting an educational project display for

municipal offices, and a high-quality brochure. In addition, the publicity committee organized two public

field days at the site and promoted the usefulness of

finished compost through an information campaign.

Today, due in part to this educational campaign, the

facility continues to compost and has gained acceptance for its finished product. Many groups, such as

the Maine Department of Transportation, along with

towns and private citizens use the compost for landscaping and soil amendment purposes (York and Laber,

1988).

composting facililty in their community (the Not In My

Backyard, or NIMBY, syndrome). People might be especially opposed to siting a facility in populated areas or in

areas located near residences, schools, and hospitals.

Residents near a site proposed for a composting facility

might be concerned about potential problems with the

operation, particularly about the potential for odor generation. Noise, traffic, visual impacts, and potential health

threats might be additional concerns of residents. Officials

should be prepared to listen to the public’s concerns and

to negotiate the site selection or the design of the facility.

Many communities have changed site or facility design on

the basis of citizens’ concerns. Involving the public in siting decisions builds a greater sense of community solidarity in the project and facilitates compromise among the

participants in the project.

Officials should assure residents that serious problems do

not occur at properly managed facilities, and that effective

corrective measures are available for any complications

that do arise. However, it is important to communicate

that composting is not risk free, just as combustion and

landilling are not risk free. Offering information about

the experiences of other communities might help to allay

concerns about the facility. Communicating information

about any risks associated with the program is critical in

building consensus for siting decisions. Because many

misgivings among the public about solid waste management facilities are based on perceived risk, officials should

be prepared to provide information dispelling or putting

into perspective any fears that arise among community

members. (Siting considerations and techniques for solving potential environmental problems are discussed in

more detail in Chapters 5 and 6.)

Site selection committees should draft a set of objective

criteria for choosing an appropriate location for the composting facility. A site selected on the basis of objective

analysis of these criteria will be more acceptable to the

public and will help counter any perceptions that the selection process is arbitrary.

Other guidelines for successful siting include:

Accepting the public as a legitimate partner.

Listening to the concerns of the different interests.

Planning a siting process that permits full consideration of policy alternatives.

Setting goals and objectives for public involvement

and risk communication activities in each step of

the siting process.

Creating mechanisms for involving the public early

in the decision-making process.

Providing risk information that the public needs to

make informed decisions.

112
to accept the site selection.

block the siting

A map showing designated drop-off collection areas (UConn CES, 1989

cerns and compromse of facility site and design, the MRF opened in the spring of 1991, and the co-composting facility opened in the fall of 1991 (ICMA and EPA, 1992).

Education Citizens About a Composting Program Information that can be provided to citizens in a notification 

about a composting program( and their role in the program) might included . A statement of the intent and communtiy benefits

of a composting program A description of the intented uses of the compost. A statement that compostable materisls must not cintain materials such as glass, metaal, 

Instructions regarding the piling of yard trimmings, or if bags are used, the type of bags and bags closure to be used; for MSW composting, it will 

to include information about source separation or commingling of compostables. Instruction regarding the placement of the material at the curb or

The dates when materials will be collected in designated districts and the locations and hours of communtiy collection stations and other dro-of

Community Involvement

Siting a Co-Composting Facility in

Wisconsin

o

fficials in Columbia County, Wisconsin, learned

the importance of public participation while attempting to site a dual materials recovery facility

(MRF) and in-vessel co-composting facility in 1989

and 1990. The officials selected a site for the facilities

in Pacific Township. Meanwhile, the township board

decided to exercise an ordinance granting it authority

to approve the siting of any solid waste authority

within township lines. When county officials purchased an option on the property prior to obtaining

township approval and applied for a Wisconsin Department of Natural Resources permit, many township

residents felt the county was trying to force the board

County officials were cordfronted with a grave public

perception and credibility problem. To avert further

misunderstanding, the county notified residents in the

area surrounding the proposed site and organized pub

lic hearings on the matter, At the same time, residents

of the township established a citizens’ committee to

Eventually the county received a permit for the facicility

from the state Department of Natural Resources with

the condition that the county agree to a number of

clauses requested by local citizens. The county agreed,

for example, to put a plastic membrane lining under

the tipping floor-of the MRF and to provide free collection of Pacific Township’s garbage. Pacific Township

also obtained authority to inspect the facility at any

time during business hours and issue citations if anything was out of order. Thanks to the willingness of the

■ Being prepared to mitigate negative impacts on the

community.

■ Evaluating the effectiveness of public involvement

and risk communication activities (EPA, 1990).

Public Participation in the

Composting Project

To ensure that the composting project runs smoothly

members of the public must have a clear idea of their role

in the program. Facility or community officals must

communicate information such as the collection schedule,

acceptable and unacceptable materials, and how the materials will get to the facility. Residents can be notified of

collection dates by letter or through announcements in

newspapers or on the radio.

Municipalities also can provide information to the public

about home composting or leaving grass clippings on the

lawn. This information can help reduce the amount of

yard trimmings that a community needs to collect. For

facilities that compost either yard trimmings or MSW,

information also should be provided about the availability

of finished compost and whether the product is free or for

sale (Wish et al., 1990).

At the composting facility, attractive and informative signs

can communicate salient information to the public, including the nature of the project, the facility name, the

hours of operation, and the business address and telephone number of the operator. Other signs can direct collection vehicles to unloading areas and indicate traffic

circulation patterns. If there is a drop-off site, signs should

guide people to the site and clearly present the rules for

delivery of the materials. The facility operator should consider including a reception area in the plant and arranging

for tours for interested members of the public and the media. Officials also can recruit volunteers from the community to participate in monitoring incoming materials and

assisting at the drop-off facility.

113
Community Involvement

Another way to maintain a positive relationship with the

community is to establish a complaint response procedure. Some municipalities, for example, recruit residents

to participate on “odor panels” that report to the facility

the detection of any odors originating from the composting site. (Most composting facilities receive some complaints, primarily about odors.) Complaints should be

logged, along with the time, name of the complainant, action taken in response to the complaint, and the date of

followup communication to the complainant. This procedure is designed to ensure that small problems are solved before they become larger ones, and will reassure neighbors

that their concerns are taken seriously (Walsh et al., 1990).

community education about composting should continue

after the composting operation begins to ensure that support

does not wane. Ongoing publicity can describe successes in

the composting project and remind the community that

composting is an important tool to manage organic materials. The effectiveness of the publicity techniques should be

evaluated periodically

Community Education at the

Marketing Phase

Community education also is important in marketing, especially if the compost will be distributed to residents.

Literature can be developed explaining the merits and uses

of the compost, how the compost will be distributed (e.g.,

in bags or in bulk), and any restrictions on use. Samples

of the product also can be provided to potential users. In

addition, some communities give away compost to residents or neighbors of the composting facility (or provide

it at a nominal charge). This can be promoted as a public

service. Such programs foster goodwill and build support

for the composting facility, although communities should

be aware that giving compost away could create the impression that it has no monetary value. Many giveaway

programs require residents to pick up compost at a centrally located site, which is sometimes combined with a

recycling center. This approach helps to raise public

awareness about composting and recycling, and provides a

tangible reward to residents for their efforts. If the compost will be distributed or sold to users other than residents, marketing research should be conducted and sales

strategies devised (see Chapter 8).

Chapter Ten Resources

International City Management Association (ICMA) and

U.S. Environmental Protection Agency (EPA). 1992.

Summary

successful management of community relations

requires the same degree of attention, systematic

planning and expertise as do the more technical

elments of designing and operating a composting

program. Officals should strive to involve the public

directly in planning and siting the facility Community involvement in decision-making builds a sense

of ownership among local residents and minimizes

confrontation among concerned parties.

A strong educational program should accompany

each phase of facility planning and operation. Public outreach should include risk communication, information on program logistics such as collection

times and places, and pubic service announcements

and advertisements aimed at raising public participation in the program.

Case studies of municipal solid waste facility sitings: Success in your community (revised draft report). 73-80.

Logsdon, G. 1991. Slowing the flow to the landfill. BioCycle. May, 32(5):74-75.

Richard, T. L., N.M. Dickson, and S.J. Rowland. 1990.

Yard waste management: A planning guide for New York

State. Cornell, NY: New York State Energy Research and

Development Authority, Cornell Cooperative Extension,

and New York State Department of Environmental

Conservation.

U.S. Environmental Protection Agency (EPA). 1990. Sites

for Our Solid Waste: A Guidebook for Effective Public Involvement. EPA/530-SW-90-O 19. Washington, DC: Office of Solid Waste and Office of Policy, Planning and

Evaluation.

University of Connecticut Cooperative Extension Service

(UConn CES). 1989. Leaf composting A guide for municipalities. Hartford, CT: State of Connecticut Department of Environmental Protection, Local Assistance and

Program Coordination Unit, Recycling Program.

Walsh, PA., A.S. Razvi, and P.R. O’Leary. 1990. Operating a successful compost facility. Waste Age. March,

21(3):137-144.

York, C. E., and D. Laber. 1988. Two c’s overcome

NIMBY BioCycle. October, 29(10):60-61.

114
Chapter Eleven

Economics

s

ound financial planning is a crucial step in the successful development ofa composting program. When considering the mulitude of options available for tailoring a composting program to the needs and resources of

the community decision-makers must weigh the costs and benefits involved and determine whether composting represents a feasible management option for their community This section describes economic factors that a

community will need to examine when designing a composting program. To give decision-makers a clear framework ofthe costs and benefits involved in setting up and managing a composting facility the primary assumption

used throughout this chapter is that the community owns and operates the facility. Communities might want to

examine other options, such as forming partnerships with other municipalities or private companies, hiring a

contractor to run the facility or trying to attract a private company to establish the facility (see Chapter 1 for

more information on planning). A financial worksheet also is included at the back of the Chapter that can be

used to analyze cost information (Figure 11-1).

Cost Benefit Analysis cost/benefit analysis, is used widely throughout the gov-

. 9

Costs for developing a composting program typically inernment and private industry to determine the costclude 1) capital costs for establishing and equipping a faeffectiveness of implementing a social program or making

an investment. To be effective, cost/benefit analyses

cility and 2) operation and maintenance (O&M) costs should be as comprehensive and derailed as possible.

associated with such activities as collection, transporta- Many communities, therefore, hire consultants to conduct

tion, processing, program administration, and marketing, this analysis.

Communities also must keep in mind the revenue-generating or cost-avoiding aspects of the various composting Decision-makers should not expect to earn money from

choices. Composting can offer several potential economic composting. Most community owned and operated manbenefits to communities: agement facilities function at some expense to the taxpay-

■ Extended landfill longevity. ers in the area. This should not diminish the feasibility of

instituting a composting facility, however. Instead, deci-

■

■

■

■

■

Avoided costs from reducing or eliminating the

need for soil amendment purchases.

Reduced or avoided landfiil or combustor tipping

fees.

Environmental benefits from reduced landfill and

combustion use.

Creation of new jobs.

Revenues from selling the finished product.

Revenues from sale of recyclable.

sion-makrs should compare the costs of composting

against the costs of landfilling and combustion. With the

rising costs of landfilling and combusting, composting

programs frequently prove to be economically sensible

management options.

Communities can choose from a host of collection methods, site designs, and equipment technologies when planning a composting program. For instance, implementing

a simple composting program for yard trimmings that requires residents to drop off their materials would require

minimal capital and operating expenses from the community. In contrast, MSW composting programs typically

The net cost of a composing program can be projected entail far greater start-up and operating expenditures and

by estimating all capital and O&M costs and subtracting are often constructed to serve more than one community.

any revenue ardor avoided costs generated from running Typically the program design that a community selects

the program. This type of economic assessment, called a for a composting project depends on the desired level of

115
I

Economics

capital expenditure and on resources, such as equipment

and labor, that are already available and can be partially or

wholly allocated to the composting program.

Capital Costs

Capital expenses must be evaluated when establishing a

compost facility. First, the community must apply resources to plan the composting facility. This involves allocating resources to hire staff or consultants to design the

facility, to hold community meetings, and to conduct outreach measures to communicate with the community on

such issues as siting. Suitable land then must be located

and purchased, the site must be prepared for the composting activity, and vehicles and equipment might need to be

purchased. Some states might require composting facilities (particularly MSW facilities) to obtain an operating

permit, a process that can involve considerable assistance

from staff and/or consultants. When projecting yearly

costs of a composting operation, communities should annualize capital expenses for equipment and site preparation on the basis of the depreciation rate and the discount

rate.

Site Acquisition

The first capital expense that a municipality must consider is site acquisition. The cost of purchasing a site will

depend on local real estate costs and on how centrally it is

located. More remote sites likely will require less capital to

obtain, but transportation costs will be higher. Communities that have land available should base the cost of using

the site for a composting facility on the rental market

value of the land.

Site Preparation/Land Improvements

Site preparation costs can vary widely, depending on the

size of the planned facility and natural characteristics of

the land. Communities will need to engage an engineer to

design the site and the facility itself. Decision-makers

must include in the economic analysis for the program the

engineer’s salary, even when assigning a staff engineer to

design the composting facility.

Most sites for composting yard trimmings will require

grading to give the processing area the ideal gradual slope

to facilitate proper drainage and efficient composting. It

might be necessary to construct drainage channels to improve control of any runofff The state of Michigan estimates that these minimal preparation measures for a

facility that composts yard trimming will total about

$17,000 on average for a small operation on a 4-acre site

(Appelhof and McNelly, 1988). Significant variables in

this estimate include the size of the site, the cost of labor,

and the difficulty of grading the slope of the site. Infrastructure and construction costs are additional expenses to

consider. Simple, seasonally oriented operations for the

composting of yard trimming are the least expensive to

116

build, since minimal infrastructure is required. Road systems can be limited and unsurfaced, and fencing can be

limited to the processing area to protect onsite equipment. For security, a gate on the access road can be constructed, as well as a simple gate house and office for

onsite administration. Construction on this scale, for a

medium-sized operation of 12 acres, has been estimated

to cost $72,000 (Mielke, et al., 1989). These costs can

vary widely however. Paving the surface is the largest

component in this estimate, but this cost might not be

necessary, depending on the soil conditions at the site.

Larger facilities for composting yard trimmings will need

to construct more road systems; to construct a fence

around most of the perimeter of the property, and to

maintain several buildings for equipment, maintenance,

and administration. Many facilities opt to cover the compost pad to provide shelter from inclement weather. These

operations will require higher capital expenditures. In addition, utility hookups will be needed. The main variable

in this expense is the distance of the site from local services such as power lines and water mains. Finally, if a

community chooses to implement drop-off collection in

its composting program for yard trimmings, it also must

consider the land needed for a drop-off area, including an

area situated at the composting facility itself or areas located at several transfer stations where residents can deliver leaves, grass, and/or brush.

MSW facilities require significant site preparation to

guard against runoff and leachate (see Chapter 6). These

facilities will need to construct a drainage system to direct

leachate away from the composting pad to a treatment

area. In addition, a typical 300-to 400-ton per day MSW

composting facility would require an office or administration area, a mixed processing building, and a composting

area, which might or might not be fully enclosed. Typical

MSW windrow composing facilities require 9 to 24 acres

for the total facility. Capital outlays easily can exceed $1

million when preparing a site for MSW composting (Resource Systems, Inc. et al., 1990).

Vehicle and Equipment Procurement

Once the site has been prepared, communities must procure equipment. Again, lower technology operations for

the composting of yard trimmings will have minimal

start-up costs. Many small facilities that compost yard

trimmings can operate with only a front-end loader for

windrow turning, depending on the size and horsepower

of the selected model, front-end loaders cost from

$55,000 to $125,000 (UConn CES, 1989; Appelhof and

McNelly, 1988). For higher throughput operations designed to accelerate the compost process, grinders or

shredders for particle reduction are necessary these cost

approximately $40,000 to $90,000 (Wirth, 1989; UConn

CES, 1989), depending on capacity. Screening equipment

might be necessary for programs that seek to produce a
Economics

high-quality compost; these units typically range from

$25,000 for portable screens to $50,000 for stationary

units (Appelhof and McNelly 1988).

Municipalities planning small- or medium-sized operations for the composting of yard trimmings can share existing equipment with their public works department or

other communities to reduce start-up costs. In addition,

they might examine the possibilities of renting equipment. Large-scale facilities that compost yard trimmings

might be interested in specialized windrow-turning equipment, which can process material more quickly than

front-end loaders. While such equipment can increase efficiency, these units can cost well over $125,000.

MSW composting facilities, especially those with on-site

MSW separation, typically require significant equipment

purchases. Magnetic separators and vibratory screens,

which are basic units commonly used in the separation

process, can cost $5,000 and $20,000, respectively

(Wirth, 1989). Shredders, grinders and trommels to

process the feedstock each cost over $100,000. Input and

output conveyors, which move feedstock to and from the

different preprocessing equipment, vary in cost according

to length, but can cost well over $100,000 for a 300 to

400-ton per day facility (Wirth, 1989). Other equipment

that can be used for MSW composting includes odor control equipment (see Chapter 6), in-vessel windrow turning systems, and aeration equipment. Each of these

systems are priced over $100,000 for the most simple versions of the technology. Equipment costs, advantages, and

disadvantages are listed in Tables B-1 through B-8 in

Appendix B.

Training

There are also start-up costs associated with personnel

training. Whether a site is small and needs only a few

part-time workers or has a large, onsite staff, training in

equipment operations, administration, and, most importantly, quality control will be required. It is crucial that

employees recognize the role they play in the production

of consistent, highly marketable compost. Employee interest in the compost product begins with training, and

proper training prevents extensive, costly trial-and-error

learning periods (Appelhof and McNelly, 1988). (Chapter 6 contains more information on safety and health

training.)

Permits

Communities must consider outlays associated with permitting. Permitting requirements vary from state to state,

but usually a municipality seeking to open a composting

facility must submit a comprehensive application detailing site design and operations. Permit applications typically include provide an engineering design report and a

description of the site layout, facilities, and equipment.

Information on specific site activities, such as active

composting monitoring, and product marketing, as well

as a plan for preventing any environmental contamination

of the site also should be included. Applications also

might include personnel training information. Experts in

the fields of engineering, compost science, finance, and

law are usually needed to prepare applications. Planners

should cheek with their state to determine the exact permit applications requirements.

Operating and Maintenance (O&M)

Costs

O&M costs are those expenses that are incurred from

running and managing a composting facility. Typical

O&M costs include dark, utilities, insurance, and

equipment repair. These costs should be estimated during

the planning process to determine the feasibility of the

composting program for the community.

Collection Costs

One of the largest cost factors connected with any composting program is the type of collection system used. For

a management system to be suceessful, the costs of collection must not exceed available resources. Solid waste managers should become familiar with all of the various

options for separating and transporting materials to their

management facility in order to select the method that

will optimize their available resources (see Chapter 3).

The O&M costs of a collection program vary according

to the features of the collection method employed and

certain variables unique to each community. These variables include local labor costs and the presence or lack of

existing collection equipment and infrastructure.

Drop-Off Collection COStS for yard Trimmings

Limited operating costs are associated with drop-off collection programs. Decision-makers must consider expenses for an ongoing education and communication

program to encourage participation. Public offcials can

notify residents about the program via press releases and

public service announcements. Informational pamphlets

or brochures also can be mailed directly to residences, and

public meetings can be held to discuss the program. Publicity campaigns can become expensive, however, since the

process must be continuous in order to maintain the community’s interest and participation (see Chapter 10 for

more information on community outreach).

MSW Curbside Collection Cost for Yard

Trimmings

Communities looking at curbside collection as a way to

encourage greater participation must decide if such a program will be cost-effective by calculating the capital and

O&M costs associated with the various types of curbside

117
In 1988, Gardner's Supply, a national mail order firm located in Burlington,Vermont, proposed to the city that it convince residents to drop off th

A Public/Private Co-Composting Venture 

create 500 tons of compost during the first year of operation. The public relations campaign cost about $2,400 (ICMA, 1992)

with incentives from Gardner's Supply, such as coupons for free finished compost and discount on the company's products, brought enough mater

cow and chicken manure and supervised the laying out of long windrows across the plot. A vigorous public education campaign consisting of flyers and si

leaves and lawn clippings at a 2-acre plot near the firm's headquarters. To supplement the yard trimmings, Gardner's Supply brough in 70 truckloa

Economics

collection programs (bulk or containerized). Curbside collection is a more costly collection method than drop-off

programs, but often the additional feedstock reduces unit

processing costs.

Bulk collection systems for yard trimmings are a fairly

labor-intensive undertaking. Personnel must spend considerable time per stop to collect the yard trimmings, resulting in higher operating costs than for containerized

collections. This method also involves additional training

expenses. Since bulk collections are more prone to contamination than containerized collections (particularly in

communities in which tipping fees are charged to residents for their solid waste), collection personnel must be

trained to spot and remove noncompostables hidden in

curbside piles of yard trimmings. A curbside collection

program that picks up containerized yard trimmings is a

less labor-intensive operation. Such a program, however,

does involve the purchase of the containers and their distribution to local residents. Chapter 3 contains detailed

cost information on the various types of bags and bins.

With some bins, collection trucks might require special

lifting equipment.

MSW curbside collections can be conducted with sourceseparated or commingled MSW. Onsite separation will

result in a large volume of recyclable and noncompostable

material, and the latter must be transported off site for

proper disposal. Source-separated MSW collection involves the costs of a continuing education program to inform residents on which components should be separated

out. Commingled collection entails intensive sorting and

removal prior to composting. Significant labor and capital

expenditures will be incurred from installing and operating

the needed preprocessing equipment. In addition, this collection procedure is not entirely free of added hauling costs.

Labor Costs

The labor required at a compost facility is contingent

upon the volume and type of material handled, as well as

the level of technology used. At a minimum, most operations require workers to receive and prepare compostable

material for windrowing form and turn the windrows;

prepare the compost product for delivery and perform

monitoring maintenance, and administration functions.

A low-technology leaf composting site, one that processes

about 3,000 to 5,000 cubic yards of leaves per acre with

windrows turned by a front-end loader, could function

with just two people working part time-one to operate

the front-end loader and one to monitor the site and to

water the windrows—or one full-time staff person. It has

been estimated that such a facility would need about 135

to 150 labor hours to produce compost.

AS the complexity of the facility and the program grows,

more employees will be needed to perform various functions in the process. A high-technology site that composts

yard trimmings and uses forced aeration and windrow

118

turners to compost 80,000 cubic yards of feedstock per

year, for instance, might need a plant manager or supervisor to oversee the site; equipment operators to handle the

machinery and vehicles; and workers to empty bagged

material, wet incoming compostable material, and maintain the site. Other workers could include a tipping floor

operator, scale operator, and maintenance personnel. For

a facility of this size, much of the staff would likely be employed full time.

Because of the amount of separation and preparation involved, mixed MSW composting facilities usually incur

the greatest labor costs. In addition, at mixed MSW facilities, more extensive administration and maintenance is

needed over all site operations. The compost process, in

particular, must be overseen carefully and detailed records

on each composting phase must be kept in order to ensure

that a consistent product is produced. This labor drives up

costs. For example, the Delaware Reclamation Project, a

1,000-ton per day mixed MSW composting site that sorts

out noneompostable material with mechanical sorting

and uses an in-vessel system for composting, requires an

annual personnel budget of several million dollars.

Fuel, Parts, and Supplies

The O&M costs for facility equipment also can be significant. To operate as cost effectively as possible, fuel,il,

parts, and other supplies must be available to keep site

machinery functioning at capacity. AS a rule of thumb,

municipalities can calculate these expenses for a yard trimmings facility as a percentage of the initial equipment

capital costs, with estimates likely ranging around 15 percent. MSW composting will have higher equipment operating costs than yard trimmings facilities, since much of

the composting is dependent on processing equipment.
Economics

For example, at a 300- to 400-ton per day MSW in-vessel

composting facility, these expenses could reach about

$150,000 (Wirth, 1989). O&M costs for odor control

equipment alone can range up to $360,000 annually, depending on the type of equipment used (see Table B-8 in

Appendix B). These costs include those for biofilter media, chemical solutions for wet scrubbers, and carbon replacement for carbon absorption systems.

Outreach and Marketing Costs

The success of any composting program relies heavily on

the individuals contributing the feedstock. The importance of public education in developing a composting

program should not be underestimated; the composting

program should be kept in the public’s attention constantly in order for a community to maintain good participation and recovery levels. Education can take on a

multitude of forms, from radio and television announcements to newspaper press releases. Communities

should take advantage of as much “free press” as possible.

Expenditures on public outreach often depend on the

level of sophistication communities choose for their publications and other informational activities. A simple brochure or Fact sheet can be written and printed for only a

few cents per copy, for example. (Chapter 10 describes

public outreach techniques, and Appendix A contains examples of public outreach material.)

Communities also can choose to market their finished

compost to a variety of potential end users (see Chapters 8

and 9). Marketing efforts should commence with a market assessment to identify such factors as the transportation needs and desired chemical and physical

specifications of each potential buyer. Municipalities often

engage private companies to conduct these surveys and to

develop creative advertising campaigns.

Other Costs

Lesser O&M costs, from utility payments to building and

grounds maintenance, are inherent in any composting

program and should be anticipated. Laboratory testing for

monitoring the quality of the compost produced is another O&M cost. In addition, virtually all composting

operations produce residual waste that must be disposed

of. Large mixed MSW composting sites that receive commingled solid waste and sort out the noncompostable

fraction will generate substantial volumes of reject material, often between 10 and 30 percent of incoming materials (Goldstein and Spencer, 1990). Yard trimmings facilities

usually receive compostable yard trimmings separated from

solid waste, and therefore extract a smaller percentage of residual waste, ranging from 1 to 10 percent (Kashmanian and

Taylor, 1989). The specific costs of rejection disposal depend

on the distance of the composing facility from the landfill,

as well as on the tipping fees for the local landfill.

Benefits From composting

Avoided Costs

The potential for avoided costs must be incorporated into

the cost/benefit analysis of a composting facility. There are

five major avoided costs associated with composting.

First, because composting reduces the need for landfilling

or combustion, some tipping fees are avoided. The

amount of money saved through composting can be substantial, especially in communities where landfill or combustion capacity is scarce. In some areas, landfill or

combustor tipping fees exceed $100 per ton. Second, a

composting program extends current landfill life and delays the construction of a more expensive replacement

landfill or incinerator. This is particularly significant for

municipalities whose landfills are nearing capacity. Third,

composting avoids the environmental costs of landfilling

operations. For example, risks such as the production of

leachate or methane gas are often not reflected by the tipping fees paid to dispose of solid waste; composting reduces these risks, although quantifying the amount of risk

reduction might be a difficult task. Fourth, with composting the community saves money it currently spends on

soil amendments, topsoil, mulch, wood chips, and other

products for municipal landscaping, landfill cover, and

reclamation programs. If a community uses the finished

compost it produces for these purposes, it will avoid such

expenditures. Folly, composting might result in costs that

can be avoided through reduced trash collection. If drop-off

or curbside programs divert enough yard trimming or compostable MSW sanitation personnel might spend less rime

collecting waste destined for the landfill or combustor.

Revenues

It is possible for communities to produce and market a

high-quaky product as a result of their composting efforts. These revenues can help defray some of the costs associated with a composting program; it is very unlikely,

however, that these revenues alone will offset start-up and

O&M costs. Compost from yard trimmings currently is

more marketable, although markets for MSW compost

might be opening up.

If revenue from the sale of compost is reported as the

price per ton of finished compost, communities should

calculate the ratio of tons of finished compost to tons of

compost feedstock (e.g., $50/ton of finished compost

where 5 tons of feedstock are used to produce 1 ton of

finished compost would translate into $10/ton of feedstock revenue stream).

Limited additional revenues might be earned by separating out recyclable materials during the collection process

or at a mixed MSW composting Facility. Finally, if a community accepts yard trimmings or MSW for composting

from neighboring communities, revenue can be generated

by collecting ripping fees.

119
Economics

Summary

T

he cost components of the various composting systerns are the major determinants in choosing a

composting system. Judging whether a composting program will save money is difficult and and

as much on local circumstances as on the chosen combination of collections and processing. A municipality's size in proportion to its labor rates, land lease or

purchase costs, and equiment cost and operating

rates will determine much of its composting costs.

While it is impossible to consider every contingency,

planners must approach the issue of costs and benefits

from this perpective, drawing all relevant fators

into the equation to make a sound decision on composting in their community. To determine the savings

{

and thus the economic feasibility o a composting facility planners should evaluate t e cost per ton of

material composted and compare these numbers with

the costs of alternative management options.

Chapter Eleven Resources

Appelhof, M., and J. McNelly. 1988. Yard waste composting guide. Lansing, MI: Michigan Department of Natural

Resources.

Dickson, N., T. Richard, and S. Rowland. 1990. Yard waste

management: A planning guide for New York State. Albany,

NY: New York State Energy Research and Development

Authority, Cornell Cooperative Extension, and New York

State Department of Environmental Conservation.

Goldstein, R and B. Spencer. 1990. Solid waste composting facilities. BioCycle. January, 31(1):36-39.

International City/County Management Association

(ICMA). 1992. composting solutions for waste management. Washington, DC: ICMA.

Kashmanian, R., and A. Taylor. 1989. Costs of composting vs. landfliing yard waste. BioCycle. October,

30(10):60-63.

Massachusetts Department of Environmental Protection

(MA DEP). 1991. Leaf and yard waste composting guidance document. Boston, MA: Division of Solid Waste

Management.

Mielke, G., A. Bonini, D. Havenar, and M. McCann.

1989. Management strategies for landscape waste. Springfield, IL: Illinois Department of Energy and Natural Resources, Office of Solid Waste and Renewable Resources.

Resource Systems, Inc., Tellus Institute, and E&A Environmental Consultants. 1990. Lowell-Chelmsford CoComposting Feasibility Study.

University of Connecticut Cooperative Extension Service

(UConn CES). 1989. Leaf composting A guide for municipalities. Hartford, CT: State of Connecticut Department of Environmental Protection, Local Assessment and

Progress Coordination Unit, Recycling Program.

U.S. Environmental Protection Agency (EPA). 1993.

Markets for compost. EPA1530-SW-90-073b. Washington, DC: Office of Policy, Planning and Evaluation, Office of Solid Waste and Emergency Response.

Wirth, R. 1989. Introduction to composting. St. Paul,

MN: Minnesota Pollution Control Agency.

120
Equiment

Labor

Related Costs

Economics

I . START-UP (CAPITAL) COSTS

 Site Preparation

Engineering design 

 Site clearing 

Grading

Drainage

Pad material

Thermometers(2 )

(For other equipment, see optional costs)

TOTAL ONE-TIME START-UP COSTS: $

TOTAL AMORTIZED START-UP COSTS/YR: $

II. OPERATIONAL COSTS

Monitoring incoming materials and directing vehicles

Forming windrows (loader operator)

Turning windrows (loader operator)

Watering windrows

Monitoring temperature

Fuel and Maintenance

Front end loader

Lab analysis of Compost 

Marketing/distribution compost

Public education

Other

TOTAL OPERATIONAL COSTS/YRS $

Figure 1-1. Composting economics worksheet.

121
Other Optional Labor

Economics

Shredder

Screene r

Chipper

Windrow turner

Other

Compactor truck

Loader w/claw

Vacuum truck

Dump truck

Street sweeper

Other

III . OPTIONAL OPERATIONAL COSTS

Equipment, Related Labor and O&M

AMORTIZED

PRICE OF

EQUIPMENT LABO R O & M

Subtotal : + + =

Debagging

Othe r

Subtotal:

TOTAL OPTIONAL OPERATIONAL COSTS/YR: $

IV. OPTIONAL COLLECTION COSTS

Equipment, Related Labor and O&M

AMORTIZED

PRICE OF

EQUIPMENT LABO R O & M

Subtotal: + + =

TOTAL OPTIONAL COLLECTION COSTS/YR: $

Figure 11-1. (Continued).

122
Economics

v . COST/BENEFIT ANALYSIS: COMPOSTING VS. CURRENT DISPOSAL

TOTAL COSTS

A. Total amortized start-up costs/yr

B. Total operational costs/yr

C. Total optional operational costs/yr

D. Total optional collection costs/yr

E. Total Costs/Yr (A + B + C + D)

TOTAL BENEFITS

F. Avoided disposal cost/yr $

G. Avoided purchases of soil amendment/yr 

H. Projected income from sale of compost/yr

I . Total Benefits/Year (F + G + H) $

TOTAL NET SAVINGS OR COST

J. Net Savings Yea r (I-EifI>E ) $

K. Net Cost/Year (E - I if E > I) $

Source: MA DEP,1991

Figure 11-1. (Continued).

123
I

Appendix A

Additional EPA

Sources of

Information on

Composting

EPA Publications on Topics Relating to Composting

The following publications are available at no charge from

the EPA RCRA/Superfund Hotline. Call 800-424-9346,

or TDD 800-553-7672 for the hearing impaired, Monday

through Friday, 8:30 a.m. to 730 p.m., EST. In Washington, DC, call 703-412-9810 or TDD 703-412-3323.

Decision-Maker's Guide to Solid Waste Management.

EPA/530-SW-89-072. 1989.

Markets for compost. EPA/530-SW-90-073b. 1993.

Promoting Source Reduction and Recyclability in the Marketplace. EPA/530-SW-89-066. 1989.

Recycling Grass Clippings. EPA/530-F-92-012.

Residential Leaf Burning: An Unhealthy Solution to Leaf

Disposed EPA/452-F-92-007.

Sites for Our Solid Waste: A Guidebook for Effective Public

Involvement. EPA/530-SW-90-019. 1990.

Yard Waste Composting: A Study of Eight Programs.

EPA/530-SW-89-038. 1989.

Yard Waste Composting. EPA/530-SW-91-009.

The following publications are available from the National Technical Information Service (NTIS). Call 800-

553-6847, Monday through Friday, 8:30 a.m. to 5:30

p.m. In Washington, DC, call 703-487-4650.

Characterization of Municipal Solid Waste in the United

States. PB92-207 166.1992.

Charging Households Waste Colletion and Disposal The

Effects of Weight- or Volume-Based Pricing on Solid Waste

Management. PB91-111 484.1990.

Variable Rates in Solid Waste: Handbook for Solid Waste

Offical. PB90-272 063.1990.

124
Additional EPA Sources of Information on Composting

U.S. Environmental Protection Agency

Regional Offices

Region 1

U.S. EPA Region 1

J.F.K Federal Building

Boston, MA 02203

617-565-3420

Region 2

U.S. EPA Region 2

26 Federal Plaza

New York, NY 10278

212-264-2657

Region 3

U.S. EPA Region 3

841 Chestnut Building

Philadelphia, PA 19107

215-597-9800

Region 4

U.S. EPA Region 4

345 Courtland Street, NE

Atlanta, GA 30365

404-347-4727

Region 5

U.S. EPA Region 5

77 West Jackson Boulevard

Chicago, IL 60604-3507

312-353-2000

Region 6

U.S. EPA Region 6

First Interstate Bank Tower

1445 Ross Avenue

Dallas, TX 75202-2733

214-655-6444

Region 7

U.S. EPA Region 7

726 Minnesota Avenue

Kansas City, KS 66101

913-551-7000

Region 8

U.S. EPA Region 8

Denver Place (811WM-RI)

999 18th Street, Suite 500

Denver, CO 80202-2405

303-293-1603

Region 9

U.S. EPA Region 9

75 Hawthorne Street

San Francisco, CA 94105

415-744-1305

Region 10

U.S. EPA Region 10

1200 Sixth Avenue

Seattle, WA 98101

206-553-4973

125
Appendix B

Composting

Equipment

Different types of equipment are used during composting

to collect and transport the feedstock materials, to remove

noncompostable materials for recycling or disposal, to increase the rate at which materials compost, to improve the

quaky of the finished compost product, to improve

worker safety and working conditions, and to prepare the

finished compost for marketing. Although the same types

of equipment can be used to compost both yard trimmings and MSW, in many cases certain types of equip

ment are more appropriate for one type of composting

than the other.

This appendix discusses the wide variety of equipment

that is available for use in composting operations. The

types of equipment discussed are divided into the following categories:

Yard trimmings feedstock collection equipment

Debagging equipment

Sorting/separation equipment

Size reduction equipment

Mixing equipment

Turning equipment

Process control equipment

Odor control equipment

Yard Trimmings Feedstock Collection

Equipment

A variety of equipment exists for the collection of yard

trimmings for processing and disposal. In most communities, yard trimmings are collected at curbside or citizens

transport their materials to a specified drop-off area or

transfer station. The main types of equipment used are

trash collection vehicles and storage containers. because

compactors and containers are so common, this equipment is not discussed here.

There are several types of equipment available for yard

trimmings collection today mechanical scoops, which use

either a bucket-like system to scoop yard trimmings or

126

pincer-like systems to grab yard trimmings; and vacuum

machines, which suck leaves through a nozzle for collection (Barkdoll and Nordstedt, 1991). These types of

equipment are briefly described below

Bucket Attachments - These are standard attachments

that can be fitted to a front-end loader and are used

to scoop up yard trimmings and place them into

holding containers.

Pincer Attachment - These attachments can be fitted

to front-end loaders or skid/steer loaders. Pincer

buckets grab, rather than scoop up, the yard trimmings and place them into holding containers, usually on dump trucks or garbage packers.

Self-Contained Mechanical Scoops - These systems use

a series of rotating paddles that scoop yard trimmings off the ground and onto a conveyor that carries the yard trimmings to dump trucks. Mechanical

scoops are usually mounted on small tractor trucks.

Vacuum Loaders - Vacuum pressure is used to suck

leaves directly into a separate enclosed container, usually built onto dump trucks.

Vacuum Collectors - These self-contained units include both the vacuum equipment and the collection/storage units.

For more information on yard trimmings feedstock collection equipment, see Table B-1.

Debagging Equipment

For yard trimmings and MSW placed in plastic bags for

collection, some system must be used to release the feedstock materials from the plastic bags and to remove the

plastic so that it does not interfere with the composting

process or diminish the quality of the finished compost

product. Although manual opening and removal of bags is

acceptable and widely used, a wide variety of commercial

debagging equipment is now available.
Well suited for collecting leaves; the system is self-contained and includes a self-dumping collection until along with the vacuum machine; a compactor is available through at least one manufacturer.

Many public works agencies have themm

gravel.

Vacuum Collectors $15,000 to $40,000. Not good for grass and leaves when they become wet or frozen; must be mounted to a collection/storage vehicle; la

Composting Equipment

Table B-1. A Comparison of yard trimmings collection equipment.

Type of Equipment Cost Major Advantages Major Disadvantages

Bucket Attachments Usually included in

available;work well on hard surface

Not very efficient for collecting Ioose yard

price of front-end trimmings; must be fitted to a ant-end

loader. loader or similar vehicle; pick up dirt and

Pincer Attachments $2,300 to $12,000. Well suited for collecting trimmings, Must be fitted to a front-end loader or similar

particularly leaves; good for wet leaves. vehicle; might need street sweeper to follow,

depending on type of pincer.

Self-Contained $85,000 to Well suited for collecting yard trimmings, Must be fitted to a front-end loader or similiar

Mechanical Scoops $100,000. particularly leaves; the unit is self-contained vehicle.

and no front-end loader is necessary.

Vacuum Loaders $6,000 to $25,000. Well suited for collecting leaves; can be Must be mounted to a collection/storage

detached from the collection vehicle to dump; vehicle; labor intensive.

can remounted to the front of the

collection/storage vehicle.

Source: Barkdoll and Nordstedt, 1991.

There are two general categories of commercially available

debagging devices: slitter trommel devices and augers. AU

of these debagging systems can be used for both yard

trimmings and MSW. Debagging can occur at the facility

or at curbside. All the equipment described below is employed at the facility, except for the compactor truck with

auger, which is attached to a collection vehicle

Slitter/Trommel Devices - A wide variety of slitter and

trommel equipment are commercially available today. With these systems, the bags are either fed directly into the slitter or are transported by conveyors

to the slitter unit. Slitters generally use counter-rotating blades to slice open the bags. The bags and their

contents then fall or are transported by conveyors

into the trommel unit. Feedstock is screened from

the bags in the trommel unit, either through vibrating action of flat screens or rotating action of drumlike screens. Bags are removed from the trommel by

hand or by air or water classifying units. Slitter/trommel systems can be used in conjunction with separation devices to remove metals, plastics, glass, etc.

Augers - With auger systems, bags are loaded into the

auger unit where a sharp-edged, screw-iii shaft rotates and slices open the bags. The bags are turned

and mixed by the auger so that their contents are released. The auger units generally are on an angle

with the infeed end higher than the discharge end.

Gravity moves the bags and feedstock materials

through these systems. The materials are released at

the discharge end and bags are removed by hand or

by classifiers.

Trash Compactor Trucks with Augers - Although the

primary purpose of these units is trash compaction,

most bags loaded into these units break during processing. The bags are dropped into the unit and are

ripped when they pass into the compactor. The turning of the auger futher rips the bags, compacts the

materials, and releases much of the material from the

bags.

Spike and Conveyor Debagging Systems - One company has developed a system where bags are loaded

into a hopper where a spiked chain grabs and drags

the bags into a trough with two counter-rotating

wheels edged with vertical spikes. The bagsy press

down on each other and the pressure causes the bags

to be gripped by the spikes and ripped open by the

counter-rotating motion. Contents of the bags spill

onto a conveyor and the bag clings to the spikes. A

vacuum machine removes the bags from the spikes.

Specially Designed Windrow Turners - The elevating

face of these windrow turners lifts the plastic bags

with paddle-like extensions. The bags are hooked by

trencher teeth on the front of the windrow turner

and ripped open. As the bags flip over the top, their

constents are spilled out and the bags remain hung

on the teeth. Common systems can be adapted with

a bar containing cutting blades to enhance bag open127
For

Composting Equipment

f

1

I

ing and with spiked teeth (rather than the normal

cup-like teeth) to increase bag retrieval. Certain

windrow turners also can be adapted to keep material in the windrow away from the bearings and can

be fitted with a radial arm to cut bags off the drum

of the windrow turner when they get wrapped

around it.

Mechanical ]aw Debagging Systems - Front-end loaders or in-line conveyors are used to feed bags into

these systems. When the upper jaws of the unit

open, the bags fall into the processing area. When

the upper jaws close, new bags cannot enter the processing unit until processing of the original bags is

completed. Bags are held in a&d position while

rippers slash them open. The lower jaws open and

drop the material and bags onto a conveyor. A system is being developed to mechanically remove the

bags, but currently manual separation of the bags is

required.

Saw-ToothedBlade Debagging Systems - These relatively small units can be used as stationary systems

or they can be pulled by tractors. Power is supplied

from the tractors, or the units can be adapted for

electric motors. Bags are manually fed onto a conveyor, which is at a 45° angle. The conveyor is

equipped with heavy, metal bars that are perpendicular to the conveyor and spaced 18 inches apart. Each

bar has two tines that hook the bags. Hooked bags

must pass under a saw-toothed blade, which tears

them open. At the top of the conveyor, the contents

of the bag are dropped into a bin. A blower blows

the materials from the bags into a hopper or a truck

or directly into a windrow for mobile systems. The

bags stay attached to the tines and dangle down until

they are caught by a double roller that pulls them

from the tines and feeds them into a baler.

more information on debagging equipment, see

Table B-2.

Sorting/Separation Equipment

Sorting and separation of both yard trimmings and MSW

usually are warranted to remove noncompostable materials and contaminants from the compost feedstock. A variety of sorting systems are available, ranging from

technologically simple and labor intensive methods like

manual removal of noncompostables and contaminants

from a conveyor to technologically complex systems that

mechanically separate noncompostables from compostables on the basis of physical characteristics such a

weight, size, conductivity, and magnetic properties. Although all sorting/separation equipment can be used for

128

both yard trimmings and MSW feedstock, certain types of

equipment are more appropriate for one type of

composting than another. The main types of sorting/separation equipment are briefly defined below.

Conveyors - Conveyors are mechanical systems with

belts that slowly pass over rotating wheels. Conveyor

belts are used in the sorting/separation phase of composting to allow a constant stream of feedstock to

pass by workers who manually remove noncompostables and other contaminants. The conveyor belt

must be narrow enough for the workers to reach its

center. Conveyors are needed primarily at MSW

composting facilities.

Screens - There are many types of screens, but all sort

materials based on their size. The following types of

screens are used in yard trimmings and MSW composting (Richard, 1992 Rynk et al., 1992):

 Stationary screen - These are grates that are held

in place while feedstock materials are dropped

onto them. They retain materials that are larger

than the mesh on the grate, while materials that

are smaller than the mesh fall through. Screens

with different mesh sizes can be positioned to

separate materials into different size categories.

■ Shaker screens - Mechanical action causes these

screens to move with an up and down motion.

This movement helps to sift the materials through

the mesh on the screens. The motion minimizes

blinding. Heavy balls can be placed on the screen

to help dislodge materials that are clogging the

screen. Screens with different mesh sizes can be

used with shaker screens to separate materials into

different sizes.

■ Vibrating screens - These are similar to shaker

screens except that the rate of motion is much

more rapid. Vibrating screens are placed on an angle to remove oversized materials. Like shaker

screens, different mesh sizes and cleaning balls

can be used.

■ Trommel screens - These are long, cylindrical

screens that are placed on an angle so that materials flow through them. Materials that are smaller

than the grate fall through. As trommel screens rotate, a brush is passed over the top of the screen to

remove lodged materials and prevent clogging of

the screen. Trommel screens can separate items of

different sizes by having a mesh gradient that increases away from the infeed end of the screen.
Manual separation or another bag removal mechanism must be used; up to 30% of the shredded plastic or paper bag pieces can remain in co

Augers

Approximately $69,000.

Approximately $49,500 Removes almost all bag contents. Must be fed by cobveyor or front-end loader.

Slitter/Trommel Devices

ed; 75 to 99% of the bag contents are removed; 15 to 40 tons of material are processed per hour (some systems can process up to 90 tons per hour for just yard trimmings); 

Bags are left whole or in large pieces; a wide variety of systems are commerically avilable with different adaptations for specific requirements. $90,000 to $270,000

1,700 bags per hour can be processed

Trash Compactor Trucks with Augers Data not available. Excellent safety features, including automated lifting of carts and the auger compaction combine, which reduce injuries to collection personnel. To be efficient enough for use with a composting operation, only papaer bags can be processed; with plastic bags, future sc

Debagging Systems

$95,000

customize the system to tailor it to specific facility.

Designed

arm o remove bags

wrapped around the

bags that become wrapped

around the windrow turner

drum of the windrow turner.

aw Debagging Systems 90% of the bags are opened; 99% of the bag contents are removed; 1,200 to 1,500 bags per hourcan be processed

$88,000.

adjusts for different sized bags

mechanical device

Composting Equipment

Table B-2. A comparison of debagging equipment.

Type of

Equipment Efficiency Cost Major Advantages Major Disadvantages

Approximately 98% of bag contents $65,000 to $75,000. Models are available with Small bags can squeeze

are removed; up to 25 tons of augers that reverse direction through the system without

material can be processed per hour. when jammed; bogs are left being opened; manual

whole or in large pieces; separation of bags is

companion baling sytems for required

bag and separation devices

Spike and 2,000 bags are opened pe r hour;

Conveyor approximately 10 tons of material

can be processed per hour.

Specially Approximate 90% of the bags

were removed with three passes of Windrow the windrow turner with one model

Turners investigated; with another model,

80% the bags were removed with

four passes; approximately 41 tons

of material can be processed per

hour; 1,172 bags were opened per

hour with one of the systems.

Debagging 100% of the bugs are removed.

Attachments

for

Compactor

Trucks

Approximately After processing, bags are It will be necessary to

whole or in large pieces; a

vacuum component removes

the bogs and there is no

need for manual separation;

virtually all bags are

retrieved with is method.

Approximately The unit also can be used for For maximum debagging

$57,000; $100,000 windrow turning; some efficiency, bags should only

to$15,000to windrow turners can be be placed three deep in a

retrofit certain purchased or retrofitted with windrow; plastic bags can

models with a radial a radial arm for removing become wrapped around the

drum. drum.

Appproximately All bogs are removed; less Labor is required to hold the

$8,750. labor and handling are bags in place while they are

required at the composting being processed; a rear-load

site, because all bags hove compactor truck is needed to

been removed; can be use this system; it is only mounted on an rear-load appropriate for small

Compactor truck. communities with 10,000 to

25,000 residents.

Saw-Toothed 1,200

Blade 

 bags per hour can be Approximately Can be used as a stationary Must be fed by conveyor.

Debagging process unit or pulled by a tractor; self

Systems with mobile units, material can

be blow from the bags

directly into the windrows; a

automatically bales the bags.

Source: Ballister-Howells, 1992.

129
I

Composting Equipment

 Disc screens - These systems consist of many rotating scalloped-shaped, vertical discs. Small items

fall through the spaces between the discs, and

large items are moved over the discs to the discharge end of the system. These systems remove

large items but do not separate the smaller pieces

by size.

 Rotary screens - Feedstock is loaded onto spinning,

perforated discs with this system. Oversized materials are thrown from the screen because of the

spinning action. Undersized materials fall through

the perforations in the discs.

 Flexing belt screens - Belts with dots or some other

type of perforation are used with these systems.

Segments of the belt are flexed and snapped in an

alternating pattern, or the belt moves with a wavelike motion. This movement helps undersized materials to fill through the belt and removes

materials that are clogging the screen.

■ Auger and trough screens - These systems use a perforated trough to screen materials, An auger rotates in the trough, helping fine material fall

through the perforations and moving oversized

material out of the trough. Auger and trough

screens with perforations of different sizes can be

used to separate materials by size. This type of

screen is primarily used to sort fine materials from

wood chip.

■ Magnetic Recovery Systems - With these systems, a

magnetic field removes ferrous metals from the rest

of the feedstock material. The following types of

magnetic separators are commonly used with yard

trimmings and MSW composting systems:

Overhead belt magnets - Cylindrical magnets are

installed over a conveyor belt, which carries feedstock. A belt is secured around the magnets,

which rotate to move the belt. The belt is made of

a material that becomes magnetized by the magnets, allowing the belt to attract ferrous metals

and remove them from the conveyor belt below.

The magnetized belt is either positioned directly

over the conveyor belt or perpendicular to the

conveyor belt. Generally, the magnetized belt

moves more quickly than the conveyor belt to improve the efficiency of the magnetic separation.

Drum magnets - Drum magnets are placed over a

conveyor at the end of a mechanism used to feed

the separation system. Ferrous metals in the

feedstock that pass under the rotating drum are

attracted to the magnet and stick to the drum. An

operation must be conducted to periodically

scrape the ferrous metals from the drum.

Eddy-Current Separation Systems - These systems are

used to separate nonferrous metals from feedstock

materials. A high-energy electromagnetic field is created, which induces an electrical charge in materials

that conduct electricity, primarily nonferrous metals.

The charge causes these materials to be repelled from

the rest of the feedstock materials.

Air Classifiers - With this technology, feedstock materials are fed through an air column at a specified rate.

The air column is created by a vacuum that sucks

light materials into a cyclone separator. As materials

lose velocity in the cyclone, they are separated out by

volume. Heavy materials are not even picked up by

the sucking action and fall directly though. Air classifiers target light objects like paper and plastic and

heavy objects like metals, glass, and organics.

Wet Separation Systems - These systems use water

rather than air to separate materials. Materials enter

a circulating water stream. Heavy materials drop into

a sloped tank, some of which vibrate. The heavy

items then fall into an area where they can be removed. The lighter materials float and are removed

from the water with stationary or rotating screens.

These systems target organics and other floatable materials and sinkable materials like metal, glass, gravel,

etc.

Ballistic or Inertial Separation Systems - These separators are based on the density and elasticity characteristics of the feedstock materials. They use rotating

drums or spinning cones to generate a trajectory difference that bounces heavy materials away from

lighter materials. These systems separate materials

into three categories: light materials, such as plastic

and undecomposed paper medium materials, such

as compost and heavy materials, such as metals,

glass, gravel, etc.

more information on sorting/separation equipment,

see Table B-3.

Size Reduction Equipment

Size reduction of feedstock materials is done with both

yard trimmings and MSW composting, primarily to increase the surface area to volume ratio of the material to

speed up the composting process. Size reduction also can

improve the effectiveness of certain sorting/separation

technologies. Although the available size reduction equipment can be used for both yard trimmings and MSW
Rotary Screens Movement helps limit clogging of the screen

Troughs with perforations of varying sizes can be used to sort materials into different size categories; movement of the auger helps move oversized materials 

Air Classifiers Light materials that are larger in size (such as plastic and paper)can be removed. Only targets and eliminates relatively light or heavy items; does not remove medium-weight 

Only targets and eliminates large item; does not sort materials by size; does not remove small pieces of glass, ,etl, plastic, and other noncompostable mecha

Movement, particularly snapping and wave action, help limit clogging of the screen.

Auger and Trough Screens Only separates by size and does not remove small pieces of glass, matel, plastic, and other noncompostables; mechanization increase 

to discharge pont; movement limits clogging of the scren' designed to remove wood chip from finer materils.

non compostables; mechanization increases expense.

Composting Equipment

Table B-3. A comparison of sorting/separation equipment.

Type of Equipment Major Advantages Major Disadvantages

Conveyors Relatively low cost; enables separation of all categories Requires manual separation of materials.

of materials.

Stationary Screens Lack of mechanization makes them relatively Screens easily became blinded; only separates b size

inexpensive; screens of different mesh sizes can be and does not remove small pieces of glass, metal

used to sort materials into different size categories. plastic, and other noncompostables.

Shaker Screens Screens of different mesh sizes can be used tO sort Only separates by size and does not remove small materials into different size categories; movemenf and pieces of glass, metal, pIastic, and other

use of cleaning balls limits clogging of the screens. noncompostables; mechanization increases expense.

Vibrating Screens some models have been adapted specifically for Only separates by size and does not remove small

compost use; screens of different mesh sizes can be

usedto sort materials into different size categories; pieces of glass, metal, plastic, and other

noncompostables; mechaniztion increases expense. slope of screen helps move oversized materials to

discharge paint; movement and use of cleaning balls

limits clogging of the screens.

Trommel Screens A screen of varying mesh size can be used to sort only separates by size and does not remove small materials info different size categories; slope of unit

helps move oversized materials to discharge point;

pieces of glass, metal, plastic, and other

noncompostables; mechanization increases expense. movement and use of cleaning brush limits clogging of

the screen.

Disc Screens Targets and eliminates large items; long history of use Only target and eliminates large items; does not sort

in other industries. materials by sizs; does not remove small pieces of

glass, metal, plastic, and other noncompostables; mechanization increases expense.

Flexing Belt Screens Only targets and eliminates large items; does not sort materials by size; does not remove small pieces of

glass, metal, plastic, and other noncompostables; mechanization increases expense.

Overhead Belt Magnets Very effective at separating ferrous metals from the rest Can only be used to separate ferrous metals from the

of the feedstock materials; relatively inexpensive rest of the feedstock materials; relatively ineffective far

system far separating ferrous matals. feedstock laced on conveyors in thick layers; a

second belt is required.

Drum Magnets Very effective at separating ferrous metals; relatively Relatively ineffctive for feedstock placed on conveyors

inexpensive; a second belt is not required. in thick layers .

Eddy Current Separation Effective at recovering nonferrous material (these If magnetic se ration is not conducted prior to this

Systems cannot be separated or recovered with traditional process, high levels of contamination with ferrous magnet systems).

f

metals occurs; can on be used to separate nonferrous metals from the rest o the feedstock materials;

relative ineffective far feedstock placed on conveyors

in thick layers.

131
Wet Separation Systems Particularty effectiveat removing organics because they float; allow heavy, sharp object (such as glass pieces to be safely removed. Size reduction is needed before tis technology is used; only targets nd separate relatively light noncompostables.

Composting Equipment

Table B-3. (Continued).

Type of Equipment Major Advantages Major Disadvantages

Ballistic or Inertial Separation sorts and separates inorganics (glass, metal, and Only targets and eliminates relatively dense items;

Systems stone fall into separate bins); can use lasers or does not remove dense noncompostables;

optical scanners to target certain inorganics, mechanization increases expense.

improving recovery rate.

Source: Rynk et al., 1992; Richard, 1992; Glaub et al., 1989.

composting, certain type of equipment are preferable depending on the type of feedstock. In the following list, the

most common types of size reduction equipment available

for use with yard trimmings and MSW composting ate

briefly described:

■ Hammermill - With these systems, either free-swinging hammers strike and crush the feedstock materials

or the feedstock materials are ground against fixed

hammers and broken into smaller pieces. Hammermills must be well ventilated to prevent explosions

that could arise from clogging. The following types

of hammermills are most commonly used for

composting

■ Horizontal hammermil - These systems use

counter-rotating hammers to crush feedstock materials. The free-swinging hammers are attached

to horizontal shafts. Size-reduced feedstock must

pass through a grate before exiting the system.

■ Vertical hammermills - These systems are similar

to horizontal hammermills, except that the freeswinging hammers are attached to vertical

shafts.

■ Flail mills - with these hammermills, size reduced

materials do not have to pass through a grate before exiting the system.

■ Tub grinders - This type of size reduction equipment is used primarily for yard trimmings. Feedstock materials are loaded into the tub, which

rotates and moves the material across a fixed floor

that holds the hammers. The movement of the

tub grinds feedstock against the hammers.

■ Shear Shredder - These systems use either fixed or

free-swinging knives to slice feedstock materials into

smaller sizes. Shredders typically require little

maintenance.

 Fixed-knife shear shredders - With these shredders, a cleated belt is used to force feedstock ma132

■

For

terials against fixed knives. The materials are

raked and shredded by the movement. With this

type of equipment, adjustable fingers catch oversized materials and push them back into the shredder. Glass items are rejected and fall through a

trash chute.

■ Rotating-knife shear shredders - This type of shredder has two shafts with hooked cutter discs attached to them. The shafts are counter rotating

and the discs interconnect. The discs slice the materials until they are small enough to fall through

the spaces between the discs. The size of the reduced materials is dependent on the size of the

cutter discs.

Rotating Drums - These systems consist of a rotating

cylinder that is positioned at an angle. Materials are

fed into the drum and the rotating motion causes

them to tumble around the cylinder. The tumbling

action breaks up the materials as dense and abrasive

items pulp the softer materials.

more information on size reduction equipment, see

Table B-4.

Mixing Equipment

Mixing is performed in both yard trimmings and MSW

composting operations to optimize several characteristics

of the composting feedstock such as moisture content,

carbon-to-nitrogen ratios, pH, and particle size. Mixing

can be done when the compost piles or windrows are being turned, which does not necessarily require special mixing equipment (this probably depends on feedstock and

odor concerns, however). When more complete mixing is

warranted, special mixing equipment can be obtained.

This mixing equipment can be used for composting both

yard trimmings and MSW Because of the expense involved, however, mixing equipment tends to be used more

frequently for MSW composting because the heterogeneity of these feedstock increases the need for mixing before

composting.
hour (or 60 to 450

cubic yards per hour, depending on the measure used). size-reduction euipment. MSW; create more noise than other types of size reduction equipment.

$11,000 to $360,000. A wide variety of shear shredders are available; materials tend to be torn apart, which open up their internal structure and speeds the composting process; often can 

$450,000

$191,400

Shear Shredders 0.4 to 110 tons oer hour (or 50 to 250 cubic yard per hour,depending on the measure used). Thin, flexible items(like plastic sheeting) might not beable to process ovversized euipm

be mounted on a trailer.

size-reduced.

removed.

Composting Equipmen t

Table B-4. A comparison of size reduction equipment,

Type of Equipment Capacity Cost Major Advantages Major Disadvantages

Hammermills 4 to 75 tons per $14,000 Tend to reduce materials into Care must be taken in selecting

smaller sizes than other on appropriate hammermill for

Tub Grinders 5 to50 tons per $20,000 to A wide variety of tub grinders Can require careful maintenance.

hour (or 80 to 100 are available; portable or

cubic yards per stationary unit are available.

hour, depending on

the measure used).

Rotating Drums One model claims $135,000. Materials are mixed while being Actual size reduction varies with

75 tons per hour. feedstock mix; long

noncompostable items (like

plastics sheeting and cabIes)

usually must be manually

Source: Barkdoll and Nordstedt,1991.

Some facilities use the same equipment for size reduction

and mixing. Mixing equipment is typically divided into

batch systems and flow-through systems. Batch systems

work with one load of material at a time. They are usually

mounted on a truck or wagon so that mixed material can

be placed directly on the windrow or composting pile.

Flow-through systems are always stationary. Usually fed

and emptied with a conveyor, they can process a continuous stream of material. Both types of mixing systems

blend material by employing one of the technologies (or a

combination of the technologies) described below

Auger Mixers- These consist of one or a number of

rotating screws that chop, turn, and mix materials;

used primarily in batch systems.

Barrel Mixers - These mixers use paddles attached to

a rotating shaft to stir material. Material is continuously fed into a vertical or inclined stationary drum;

used primarily in flow-through systems.

Drum Mixers - These are slowly turning, inched

drums that tumble and blend material. Sometimes

the drums are divided into chambers for each stage

of the mixing process.

Pugmill Mixer - These mixers blend material with

hammers attached to counter-rotating shafts; used

primarily in flow-through systems.

For more information on mixing equipment, see

Table B-5.

Turning Equipment

Because large quantities of feedstock materials must be

handled, even with small composting operations, some

type of equipment is needed to turn compost piles or

windrows with almost any municipal composting operation. This equipment can range from machinery not specifically meant for composting operations, such as

front-end loaders, to highly specific types of windrow

turners. The same types of equipment can be used to

compost both yard trimmings and MSW The following is

a list of the most common types of turning equipment

used in composting operations:

Front-End Loaders - These vehicles have a shovel-like

attachment at the front of the machine. The attachment can be raised by a hydraulic mechanism to lift

feedstock materials and tipped to release the materials into piles or windrows.

Bucket Loaders - These loaders are similar to frontend loaders except that the attachment used to raise

and tip the feedstock materials is bucket-shaped.

Manure Spreaders - With these vehicles, feedstock is

loaded in a hopper at the rear of the cab. Rotating

paddles push materials out of the back of the storage

133
If the mixer is operated for too long, compaction occurs; fibrous materials, such as straw, can wrap around the mixing mechanism; limited 

Pugmill Mixers Achieves best size reduction; produces high-quailty mix. Maintaining hammes can be costly 

Auger Mixers When used in batch system, materials can be moved to curing pad or windrow while being mixed; produces uniform mix.

After mixing, the materials can be discharged directly into a composting pile or windrow; most mixers can be mounted on an available truck or wagon; good for smaller facilities. Batch Mixers

Can shred materials and therfore reduce the effectiveness of bulking agents.

Composting Equipment

Table B-5. A comparison of mixing equipment.

Type of Equipment Major Advantages Major Disadvantages

Barrel Mixers High capacity because of continuous operation; good Do not significantly compress materials; high capitol

for large facilities. costs.

Drum Mixers Facilites composting since microbial decomposition Wet material might stick to drum at high speeds or form

can begin in drum. clumps at low speeds.

Source: Higgins et al., 1981.

container, mixing the materials as they are released.

The materials can be released while the spreader is in

a stationary position into a pile or while the spreader

is slowly moving.

Tractor/Trailer-Mounted Windrow Turners - These

turners must be pushed or pulled by a tractor or

another vehicle. They ride on the side of the vehicle

and rotating paddles or other extensions flip and

turn the material in the windrow.

Tractor-Assissted Windrow Turners - These turners are

similar to tractor/trailer-mounted windrow turners

except that they require the tractor to provide a

power source to rotate their turning mechanism.

The tractor must have a power gear or hydrostatic

drive to power the turners.

Self-Driven Windrow Turners -A wide variety of

self-driven, self-powered turners exist. Some models have turning mechanisms that ride to the side

of the vehicle. Others straddle the windrow while

the turning mechanism flips and turns the composting materials.

more information on turning equipment see

. - .

For

Table B-6.

Process Control Equipment

Two of the factors most commonly controlled with compost operations are temperature and oxygen levels. Tuning of windrows and compost piles is a common way to

control these factors. Specially designed forced aeration

equipment is available to control temperature and oxygen

levels in compost piles and windrows. The primary categories of forced aeration equipment areas follows:

Suction System -A vacuum device is used to draw air

through the composting mass. The air is collected in

an exhaust pipe and can be treated for odor control.

Leachate also is removed.

Positive Pressure Systems - With this equipment, a

blower pushes air into the composting mass.

Three types of methods can be used to control the aeration

of the composting mass. These are described below:

Continuous Aeration - With these systems, aeration

devices are run without interruption (although they

can be turned off manually).

Timer Control - With these systems, empirical data is

gathered to determine when and for how long forced

aeration equipment should be run. Timers ate then

used to turn the aeration equipment on and off

Automatic Feedback Control - With these systems,

temperature or oxygen monitoring equipment is

used to determine when critical levels of these parameters have been reached. When a critical level has

been reached, the sensors trigger a mechanism that

turns the aeration equipment on or off.

For more information on process control equipment, see

Table B-7.

Odor Control Equipment

Numerous odor control methods are used at composting

facilities, ranging from simple and inexpensive procedures

(such as adding wood ash to the compost or increasing dilution of compost exhaust air with ambient air by installing fans or raising stack height) to the more complex and

costly equipment discussed below. Appropriate odor control methods will vary for different Facilities depending on

134
3 1/4 to 4 y3 buckeet. $120,000 to 170,000. Loaders

Manure Spreaders

Tractor/Trailer- Mounted Windrow Turners 300 to 3,00 tons per hour. $15,000 to $100,000. 

 $89,000 to $250,00. Very efficient for turning windrows and mixing materials; self-driven; self powered; a variety of models exit with.

Readily available in many municipalites; self-powered and self-driven; materials are not loaded into the vehicle; can be fillted with with buckets or other attachments according to facility nee

A space the width of the loader is required between every pair of windrows; poor mixe

Tractor-Assisted Windrow Turners

Must be mounted to a tractor or another vehicle; for most models a space the width of the tractor and the turner is require

for single-pass turner models, however, a space the of the tractor and the turner is required between every 

Very efficient for turning windrows and mixing materials; self-powered; a variety of models exit with different buring mechanisms

Requires a separate power

Self-Driven Windrow Turners 1,000 to 4,000 tons per hour. For some models, a space the size of the turner is required between every windrow or pair o

differnet turning mechanisms; some models straddle the windrow and require minimal space between windrows.

Composting Equipment

the type and amount of control needed and on financial of a vessel (with a perforated aeration plenum) filled

resources. with the biofilter medium. Odorous compounds in

■ Biofilters - The exhaust air from the compost process the exhaust air are removed by the biofilter through

is passed through a biological falter medium, such as various physical, biological, and chemical processes.

soil or sand. The air is evenly distributed through the For example, odorous compounds are broken down

medium by either an open system, consisting of per- into non-odorous materials such as carbon dioxide,

forated pipes set in gravel over which the biofilter water, and nitrogen, or are absorbed or adsorbed by

medium is placed, or by a closed system, consisting the biofilter. Some researchers have recommended

Table B-6. A comparison of turning equipment.

Type of Equipment Capacity Cost Major Advantages Major Disadvantages

300 to 350 bushel $9,500 to $11,000. Mixes materials thoroughly. Materiels must be loaded into

loads. the spreader before the can be

turned; a space the width of the

spreader (end the vehicle that is

used to load materials into the

spreader) is required between

every pair of windrows; it takes

significantly mare time to

conduct the mixing operation

than with other equipment

alternatives.

300 to l,200 tons $7,400 to $68,000. Very efficient far turning

per hour. windrows and mixing materials; source; must be mounted to a 

a variety of models exist with tractor or another vehicle; for

different turning mechanisms. mast models, a space the width

of the tractor andthe turner is

required between each windrow

or pile; far single-pass turner models, however, a space the width of the tractor and the

turner is require between every

pair of windrows.

source: Barkdoll and Nordstedt, 1991.

135
Exhaust gas can be captured and treated to control odors. Suction Systems Medium

Relatively uniform temerature or oxygen levels in the compost pile oe windrow can be achieved; optimal temperature or oxygen levels can be maintained

Water vapor must be removed from the exhaust gas before it reaches the suction devices; continuous use can lead to variable temperture, oxygen, and moist

Atuomatic Feedback Control High. More powerful aeration equipment is necssary.

I

Composting Equipment

Table B-7. A comparison of process control equipment.

Type of Equipment Capacity Major Advantages Major Disadvantages

Positive Pressure Systems Medium.

Timer Control Medium.

provides more efficient and uniform aeration Odor prevention is difficult; continuous use

than suction devices. can lead to variable temperature, oxygen

and moisture levels in the compost pil e or windrow; tends to create an unpleasant

working environment.

Lower airflow rates are required; no timer or variable temperature and oxygen levels that

feedback mechanism is required. are disruptive to the composting process are

likely inside the composting pile or widrow.

More uniform temperature or oxygen Ievels Temperatures are not necessary maintained

can be achieved than with continuous at optimal levels; experimentation is needed

aeration systems. to determine the best time schedule for

aeration.

source: Richard, 1992; Rynk et al., 1992.

that further research, such as measurements of odor

pervasiveness and intensity before and after air passes

through the biofilter, be conducted to verify the

odor removal efficiency of biofilters.

Wet Scrubbers - Air from the composting process is

exposed to a scrubbing solution, which reacts with

and removes the odorous compounds in the air (e.g.,

through oxidation). Multistage scrubbers are generally needed to achieve adequate odor control. It is essential that chemical reactions in scrubbers occur in

the correct sequence.; otherwise the correct reactions

may not occur, or other, odor-forming reactions

might result. The two most common types of wet

scrubbers are packed tower and mist scrubbers.

Packed tower scrubbers pass the air through packing

media through which the scrubbing solution circulates. Mist scrubbers atomize the scrubbing solution

into droplets that are dispersed through the exhaust

air stream.

Carbon Adsorption - Air from the compost process

enters a vessel containing beds of granular activated

carbon and is dispersed across the face of the beds.

The activated carbon adsorbs the odorous compounds in the air stream.

n

For

Thermal Regenerative Oxidation - The compost air

stream is exposed to temperatures of approximately

1,400 ‘F for one second. The high temperature reduces odors.

more information on odor control equipment, see

Table B-8.

. .

Appendix B Resources

Barkdoll, A.W., and R.A. Nordstedt. 1991. Strategies for

yard waste composting. BioCycle. May, 32(5):60-65.

Ballister-Howells, P. 1992. Getting it out of the bag. BioCycle. March, 33(3):50-54.

Glaub, J., L. Diaz, and G. Savage. 1989. Preparing MSW

for composting. As cited in The BioCycle Guide to Composting Municipal Wastes. Emmaus, PA: The JG Press, Inc

Higgins, A.J., et al., 1981. Mixing systems for sludge

composting. Biocycle. May 22 (5): 18-22.

Richard, T.L. 1992. Municipal solid waste composting

physical and biological processing. Biomass & Bioenergy.

Tarrytown, NY: Pergamon Press. 3(3-4):195-211.

Rynk, R., et al., 1992. On-farm composting handbook.

Ithaca, NY: Cooperative Extension, Northeast Regional

Agricultural Engineering Service.

136
Type of Equipment Cost Biofilters Capital cost $240,000 (1,600 CFM).

n Adsoption Capital cost: $600,000. Annual O&M costs: 100,000. Thermal Regeneration Captial cost: $1,5000,000 

Composting Equipment Table B-8. A comparison of odor control technologies.

Major Advantages High removal rates at moderate cost. Major Disadvantages Possible short- circuiting of exhaust gases; tendency of media to dry out, reducing effectiveness; need to main

Carbon capacity will be exhausted, requiring costly regeneration or replacement; thus standby unit is recommended; susceptible to plu

Capable of removing a broad range of compounds. Recapture heat, reducing fuel costs.

recommended as secondary system only. Numerous mechanical problems.

$360,000.

Multistage Wet Scrubbers

Packed Tower Capital cost Effective for ammonia removal;

$1 ,000,000 recirculation of solution enhances process

(65,000 CFM). efficiency.

Annual O&M costs:

$240,000 to

$360,000.

Mist scrubber Capital cost: "Once-through” passage of solution

$1,000,000 removes odorous compounds from air

(25,000 CFM). stream permanently.

Annual O&M costs:

$240,000 to

$360,000,.

Plugged media in

recirculation of solution may reintroduce

odors into air stream.

Difficulty in maintaining effective chemical

Feedrates; plugged nozzles and filters.

Annual O&M costs

$240,000 to

Source: Based primarily on estimates from pilot tests at the Concord, NH, biosolids composting facility (total exhaust air flow rate ranging from 24,000

CFM to 65,000 CFM), as reported in Biocycle, August 1992, and on personal communications with odor control researchers.

CFM = cubic feet/minute of air

137
Appendix C

Glossary of

Compost Terms

actinomycetes - Family of microorganisms belonging to

a group intermediary between bacteria and molds (fungi);

a form of filamentous, branching bacteria.

aerated static pile - composting system using controlled aeration from a series of perforated pipes running underneath each pile and connected to a pump that draws or

blows air through the piles.

aeration (for composting) - Bringing about contact of

air and composted solid organic matter by means of turning or ventilating to allow microbial aerobic metabolism

(biooxidation).

aerobic - composting environment characterized by

bacteria active in the presence of oxygen (aerobes); generates more heat and is a faster process than anaerobic

composting.

agricultural by-products or residuals - By-product

materials produced from plants and animals, including

manures, bedding, plant stalks, leaves, and vegetable

matter.

air classification - The separation of materials using a

moving stream of air light materials are carried upward

while heavy components drop out of the stream.

anaerobic - composting environment characterized by

bacteria active in the absence of oxygen (anaerobes).

bacteria - Unicellular or multicellular microscopic

organisms.

bioaerosols - Biological aerosols that can pose potential

health risks during the composting and handling of organic materials. Bioaerosols are suspensions of particles in

the air consisting partially or wholly of microorganisms.

The bioaerosols of concern during composting include

actinomycetes, bacteria, viruses, molds, and fungi.

biochemical oxygen demand (BOD) - The amount of

oxygen used in the biochemical oxidation of organic matter; an indication of compost maturity and a tool for

studying the compost process.

biodegradability - The potential of an organic component for conversion into simpler structures by enzymatic

activity.

biooxidation - Aerobic microbial metabolism of organic

or inorganic compounds.

biosolids - Solid, wet residue of the wastewater purification process; a product of screening, sedimentation, filtering, pressing, bacterial digestion, chemical precipitation,

and oxidation; primary biosolids are produced by sedimentation processes and secondary biosolids are the products of microbial digestion.

bulking agent - Material, usually carbonaceous such as

sawdust or woodchips, added to a compost system to

maintain airflow by preventing settlement and compaction of the compost.

carbon to nitrogen ratio (C:N Ratio) - Ratio representing the quantity of carbon (C) in relation to the quantity of nitrogen (N) in a soil or organic material;

determines the composting potential of a material and

serves to indicate product quality.

cation exchange capacity (CEC) - A routine measure

of the binding potential of a soil; measures the soil’s ability to remove negative ions from metals and other compounds, allowing the ions to form insoluble compounds

and precipitate in the soil; determined by the amount of

organic matter and the proportion of clay to sand-the

higher the CEC, the greater the soil’s ability to bind

metals.

cellulose - Carbon component of plants, not easily digested by microorganisms.

co-composting - composting process milking carbonrich organic material (such as leaves, yard trimmings, or

mixed municipal solid waste), in combination with a nitrogen-rich amendment such as biosolids.

compost - The stabilized product of composting which is

beneficial to plant growth; it

rapid stage of decomposition

humification.

has undergone an initial,

and is in the process of

138
Glossary of Compost Terms

compostable - Organic material that can be biologically

decomposed under aerobic conditions.

composting - The biodegradation, usually aerobic and

thermophilic, that involves an organic substrate in the

solid state; evolves by passing through a thermophilic

stage with a temporary release of phytotoxins; results in

the production of carbon dioxide, water, minerals, and

stabilized organic matter.

composting municipal - Management method whereby

the organic component of municipal discards is biologically decomposed under controlled conditions; an aerobic

process in which organic materials are ground or shredded

and then decomposed to humus in windrow piles or in

mechanical digesters, drums, or similar enclosures.

curbside pickup - The curbside collection and transport

of used household materials to a centralized handling facility (municipal or private) such as a transfer station, a

materials recovery facility (MRF), an incinerator, or landfill. Materials at curbside might be mixed together in

common containers or source separated by the householder into separate fractions such as newspapers, glass,

compostables, or any variation of mix and separation.

curbside recycling- Residents separate recyclable from

their trash and leave the recyclable on their curbside for

collection.

cured compost - A stabilized product that results from

exposing compost to a prolonged period of humification

and mineralization.

curing - Late stage of composting, after much of the

readily metabolized material has been decomposed, which

provides additional stabilization and allows further decomposition of cellulose and lignin.

decomposition - Conversion of organic matter as a result

of microbial and/or enzymatic interactions; initial stage in

the degradation of an organic substrate characterized by

processes of destabilization of the preexisting structure.

denitrification - The biological reduction of nitrogen to

ammonia, molecular nitrogen, or oxides of nitrogen, resulting in the loss of nitrogen into the atmosphere.

digester - An enclosed composting system with a device

to mix and aerate the materials.

drop off- Individuals take recyclable materials to a recycling center.

drum compostings ystem - Enclosed cylindrical vessel

which slowly rotates for a set period of time to break up

and decompose material.

endotoxins - A toxin produced within a microorganism

and released upon destruction of the cell in which it is

produced. Endotoxins can be carried by airborne dust

particles at composting facilities.

enclosed system - See “in-vessel composting.”

erosion - The removal of materials from the surface of

the land by weathering and by running water, moving ice,

and wind.

feedstock - Decomposable organic material used for the

manufacture of compost.

finished product - Compost material that meets minimum requirements for public health, safety, and environmental protection and is suitable for use as defined by

finished product standards.

foodscraps - Residual food from residences, institutions,

or commercial facilities; unused portions of fruit, animal,

or vegetable material resulting from food production.

fungi - Saprophytic or parasitic multinucleate organisms

with branching filaments called hyphae, forming a mass

called a mycelium; fungi bring about celluolysis and humification of the substrate during stabilization.

green materials- Portion of the municipal discards consisting of leaves, grass clippings, tree trimmings, and other

vegetative matter.

hammermill - Machine using rotating or flailing hammers to grind material as it falls through the machine or

rests on a stationary metal surface.

heavy metals - Elements having a high specific gravity

regulated because of their potential for human, plant, or

animal toxicity, including cadmium (Cd), copper (Cu),

chromium (Cr), mercury (Hg), nickel (Ni), lead (Pb) and

zinc (Zn).

household hazardous waste - Products containing hazardous substances that are used and disposed of by individuals rather than industrial consumers; includes some

paints, solvents, and pesticides.

humus - A complex aggregate of amorphous substances,

formed during the microbial decomposition or alteration

of plant and animal residues and products synthesized by

soil organisms; principal constituents are derivatives of

lignins, proteins and cellulose; humus has a high capacity

for cation exchange (CEC), for combining with inorganic

soil constituents, and for water absorption; finished compost might be designated by the general term humus.

hydromulching - An application method using a water

jet to spread a mulch emulsion on a land surface.

in-vessel composting - (also “enclosed” or “mechanical”)

A system using mechanized equipment to rapidly decompose organic materials in an enclosed area with controlled

amounts of moisture and oxgen.

insert - Nonbiodegradable products (glass, plastics, etc.).

inorganic - Substance in which carbon-to-carbon bonds

are absent mineral matter.

139
Glossary of Compost Terms

integrated waste management - The complementary

use of a variety of practices to handle municipal solid waste

safely and effectively; techniques include source reduction,

recycling/composting, combustion, and landfilling.

land reclamation - The restoration of productivity to

lands made barren through processes such as erosion,

mining or land clearing.

landfilling - The disposal of discarded materials at engineered facilities in a series of compacted layers on land

and the frequent daily covering of the waste with soil; fill

areas are carefully prepared to prevent nuisances or public

health hazards, and clay and/or synthetic liners are used to

prevent releases to ground water.

leachate - Liquid which has percolated through materials

and extracted dissolved and suspended materials; liquid

that drains from the compost mix.

macronutrient - Nutritive elements needed in large

 quantities to ensure normal plant development.

mature compost- Compost that has been cured to a stabilized state, characterized as rich in readily available

forms of plant nutrients, poor in phytotoxic acids and

phenols, and low in readily available carbon compounds.

mesophili stage - A stage in the composting process

characterized by bacteria that are active in a moderate

temperature range of 20 to 45°C (68 to 113°F); it occurs

later, after the thermophilic stage and is associated with a

moderate decomposition rate.

metabolism - Sum of the chemical reactions within a cell

or whole organism, including the energy-releasing breakdown of molecules (catabolism) and the synthesis of complex molecules and new protoplasm (anabolism).

micronutrients - Nutritive elements needed in small

quantities for healthy plant development trace elements.

microorganims - Small living organisms only visible

with a microscope.

moisture content - The mass of water lost per unit dry

mass when the material is dried at 103°C (2170

F) for 8

hours or more. The minimum moisture content required

for biological activity is 12 to 15 percent it generally becomes a limiting factor below 45 to 50 percent expressed

as a percentage, moisture content is water weight/wet

weight.

mulch - Any suitable protective layer of organic or inorganic material applied or left on or near the soil surface as

a temporary aid in stabilizing the surface and improving

soil microclimactic conditions for establishing vegetation;

mulch reduces erosion and water loss from the soil and

controls weeds.

municipal solid waste (MSW) - Discarded material from

which decomposable organic material is recovered for

140

feedstock to make compost. Municipal solid waste originates from residential, commercial, and institutional

sources within a community.

nematodes - Elongated, cylindrical, unsegmented worms;

includes a number of plant parasites (a cause of root damage) and human parasites.

nitrification - The oxidation of ammonia to nitrite and

nitrite to nitrate by microorganisms.

organic - Substance that includes carbon-to-carbon

bonds.

organic contaminant - Synthetic trace organics include pesticides and polychlorinated biphenyls (PCBs).

organic matter - Portion of the soil that includes microflora and microfauna (living and dead) and residual decomposition products of plant and animal tissue; any

carbon assembly (exclusive of carbonates), large or small,

dead or alive, inside soil space; consists primarily of humus.

organic soil condition - Stabilized organic matter

marketed for conditioning soil structure it also improves

certain chemical and biological properties of the soil.

oxidation - Energy-releasing process involving removal

of electrons from a substanc; in biological systems, generally by the removal of hydrogen (or sometimes by the addition of oxygen); chemical and/or biochemical process

combining carbon and oxygen and forming carbon dioxide (CO2).

pathogen - An organism, chiefly a microorganism, including viruses, bacteria, fungi, and all forms of animal

parasites and protozoa, capable of producing an infection

or disease in a susceptible host.

persistence - Refers to a slowly decomposing substance

which remains active in the natural cycle for a long period

of time.

pH - The negative logarithm of the hydrogen ion concentration of a solution, a value indicating the degree of acidity

or alkalinity; pH 7 = neutral, pH <7 = acid, pH >7 =

alkaline (basic).

phytotoxic - Detrimental to plant growth; caused by the

presence of a contaminant or by a nutrient deficiency.

polychlorinated biphenyls (PCBs) - A class of chlorinated aromatic hydrocarbons representing a mixture of

specific biphenyl hydrocarbons which are thermally and

chemically very stable; some PCBs are proven

carcinogens.

putrescible waste - organic materials prone to degrade

rapidly, giving rise to obnoxious odors.
Glossary of Compost Terms

recyclable - Products or materials that can be collected,

separated, and processed to be used as raw materials in the

manufacture of new products.

recycling- Separating, collecting, processing, marketing,

and ultimately using a material that would have been

thrown away.

runoff - Water that flows over the earth’s surface that is

not absorbed by soil.

screening - The sifting of compost through a screen to

remove large particles and to improve the consistency and

quality of the end product.

shredder - Mechanical device used to break materials

into small pieces.

size reduction - Generic term for separation of the aggregate or for breaking up materials into smaller pieces

through abrasion, thermal dissociation, tearing, screening,

tumbling, rolling, crushing, chipping, shredding, grinding, shearing, etc.; the process makes materials easier to

separate and can increase surface area for composting.

soil amendmend soil conditioner - Soil additive which

stabilizes the soil, improves resistance to erosion, increases

permeability to air and water, improves texture and resistance of the surface to crusting, eases cultivation, or otherwise improves soil quality.

source reduction - The design, manufacture, purchase,

or use of materials to reduce their amount or toxicity because it is intended to reduce pollution and conserve resources, source reduction should not increase the net

amount or toxicity generated throughout the life of the

product techniques include reusing items, minimizing

the use of products that contain hazardous compounds,

using only what is needed, extending the useful life of a

product, and reducing unneeded package.

source separation - Separating materials (such as paper,

metal, and glass) by type at the point of discard so that

they can be recycled.

stability- State or condition in which the composted

material can be stored without giving rise to nuisances or

can be applied to the soil without causing problems there;

the desired degree of stability for finished compost is one

in which the readily decomposed compounds are broken

down and only the decomposition of the more resistant

biologically decomposable compounds remains to be

accomplished.

stabilization - Stage in composting following active decomposition; characterized by slow metabolic processes,

lower heat production, and the formation of humus.

static pile system - An aerated static pile with or without a controlled air source.

thermophilic stage - A stage in the composting process

characterized by active bacteria that favor a high temperature range of 45 to 75°C (113 to 167°F); it occurs early,

before the mesophilic stage, and is associated with a high

rate of decomposition.

tilt - The physical state of the soil that determines its

suitability for plant growth taking into account texture,

structure, consistency, and pore space; a subjective estimation, judged by experience.

topsoil - Soil, consisting of various mixtures of sand, silt,

clay, and organic matter, considered to be the nutrientrich top layer of soil that supports plant growth.

toxicity - Adverse biological effect due to toxins and

other compounds.

vector - Animal or insect-including rats, mice, mosquitoes, etc.—that transmits a disease-producing organism.

volatilization - Gaseous loss of a substance to the

atmosphere.

windrow system - Elongated piles or windrows aerated

by mechanically turning the piles with a machine such as

a front-end loader or specially designed equipment.

wood scrap - Finished lumber, wood products and prunings, or stumps 6 inches or greater in diameter.

yard trimmings - Grass clippings, leaves, brush, weeds,

Christmas trees, and hedge and tree prunings from residences or businesses.

Appendix C Resources

composting Council. 1991. Compost facility planning

guide. Washington, DC: composting Council.

*U.S. GOVERNMENT PRINTING OFFICE: 1994-520-790/81120

141