U.S. Department of Agrículture

Forest Seruíce General Technícal Report S E- 16

1Urban Waste Wood Utilization

Proceedings of a Conference

on Alternatives to Urban

Waste Wood Disposal

March 26-28,1979

Charleston, South Carolina
IIIIS pumcanon prmea on recycled paper.

xy1emLJe

C-.-L -._- l-7r 1979

Southeastern Forest Experíment Statíon

Asheuílle, North Carolína
URBAN WASTE WOOD UTILIZATION

Proceedings of a Conference on Alternatives to

Urban Waste Wood Disposal

March 28-28,1979

Charleston, South Carolina

Sponsors and Organizers:

Forest Service

U. S. Department of Agriculture

Cooperative Extension Service

Clemson University

South Carolina State Commission of Forestry

Other Supporting Organizations:

Florida Division of Forestry

Georgia Forestly Commission

For sale by the Superintendent of Documento. U.S. Ciovemment Printlng Office, Wmhington. D.C. W402

Conference Planners

Chairman

Dr. H. Ken Corden, Forest Service, Southeastern Forest Experíment Station,

Athens, Georgia

Communications

Dr. Linda M. Anderson, Forest Service, Southeastern Forest Experiment

Station, Athens, Georgia

Rosemary Jordan, Forest Service, Southeastern Forest Experiment Station,

Athens, Georgia

Program Development

Larry Biles, Forest Service, State and Private Forestry, Atlanta, GeorgiaL Chairman

Edward Banks, Georgia Forestry Commission, Atlanta, Georgia

Thomas Clements, formerly, Forest Service, Southeastern Forest Experiment

Station, Athens, Georgia

Donald Higdon, Georgia Forestry Commission, Atlanta, Georgia

Professional Group Affiliations

Mike Keel, Florida Division of Forestry, Tallahassee, Florida

Local Arrangements

Dr. Donald L. Ham, Department of Forestry, Clemson University,

Clemson, South Carolina

Sandy Conger, Forest Service, Southeastern Forest Experiment Station,

Athens, Georgia

Nancy Haynie, Forest Service, Southeastern Forest Experiment Station,

Clemson, South Carolina

Charles Rountree, South Carolina Commission of Forestry,

Charleston, South Carolina

Jimmy Walters, South Carolina Commission of Forestry, Charleston,

South Carolina
Preface

Raw materials and energy resources for production of consumer goods and services

are no longer abundant. Our Ameritan society must change its behavior and its values.

We must learn to do more with less and to overcome our habitual wastefulness.

This Conference was an attempt to make a contribution to much-needed energy

and materials conservation. Urban waste wood represents a resource that can have an

impact on resource conservation. This Conference focused on defining the urban waste

wood resource and on exploring available technologies for its utilization.

Waste wood from our cities now constitutes 10 to 20 percent of the volume of

materials going into landfills. The reasons for this situation are numerous. Among

these reasons, lack of information on the utilization potential and on available technology seems most prominent.

The Urban Waste Wood Utilization Conference brought together the most knowledgeable persons in the United States to address the resource situation, utilization

options, and planning for the future. This Conference is the first to comprehensively

address urban waste wood utilization.

The Conference audience represented a wide range of professions and interests.

Included were representatives from City and county management, urban foresters and

urban forestry consultants, extension agents and researchers, and producers and

consumers of urban waste wood from both the private and public sectors.

Special acknowledgments are due severa1 key persons responsible for this Conference. Mr. Tom Clements (formerly with the U.S. Forest Service) spent numerous

hours assembling names and information and was instrumental in compiling the

knowledge base for planning and conducting the Conference. Mr. I-arr-y Biles (U.S.

Forest Service) developed the program and organized the speakers and moderators.

MS. Linda Anderson (U.S. Forest Service) organized and managed Conference communications and assisted in organizing the Conference proceedings. Mr. Don Ham (Department of Forestry, Clemson University) managed local arrangements and Conference

disbursements. Mr. Elwood Shafer (U.S. Forest Service) was central in identifying and

securing financia1 resources for support of the Conference and for printing these

Proceedings.

Others playing key roles included Mr. Jimmy Walters and Mr. Charles Rountree

(both of South Carolina State Commission of Forestry), who assisted with local

arrangements. Mr. Joseph Riley, Jr. (Mayor, City of Charleston) and Mr. Leonard

Kilian (State Forester, South Carolina Commission of Forestry) hosted the Conference. Mr. Mike Keel (Florida Division of Forestry) and Mr. Dale Higdon (Georgia

Forcstry Commission) lined up Conference exhibitors. Mr. Ed Banks (Georgia Forestry

Commission) and Mr. A. B. Curtis (U.S. Forest Service) assisted in planning the Conference. MS. Nancy Haynie and MS. Sandy Conger managed Conference registration

and were assisted by MS. Rosemary Jordan (each with U.S. Forest Service).

íí
Very special appreciation is extended to MS. Alice Clarke and Mr. Bob Biesterfeldt

for review and editing of the Conference papers and to Mr. Rob Mallette (each with

U.S. Forest Service) for proofreading.

It is our hope that this Conference and the printed Proceedings will provide a

reliable information base for bringing about waste wood utilization through materials

recycling and energy conversion.

H. Ken Cordel1

Conference Chairman

U.S. Forest Service

Southeastern Forest

Experiment Station

iii
CONTENTS

TOPIC 1: THE RESOURCE SITUATION .......................... 1

ABST&iCTS ...................................... 2

Urban Waste Wood: A National Perspective

H. KEN CORDELL and THOMAS W. CLEMENTS ........... 3

FIBREST-A Tool for Quantifying and Qualifying Wood Residues

STEVEN E. DENNISON. ........................... 14

Composition of Landfilled Urban Waste Residues

TOMMY J. LOGGINS ............................. 22

Source Separation-Procedures and Practices

MILLARD C. DAVIS. ............................. 27

Determination of Wood Content in Demolition and

Construction Wastes

JAMES A. COMMINS .............................

TOPIC II: UTILIZATION OPTIONS. ............................

;;

ABSTRACTS ...................................... 50

Paper from Municipal Trees

DAVID F. DeVOTO .............................. 52

Mulch from Limb and Trunk Debris

DAVE WALKER. ................................. 62

Products from Municipal Trees

EDWARD A. LEMPICKI ............................ 66

Firewood from Municipal Trees

JAY W. LOWERY ................................. 68

Fuel Preparation for Waste Wood Boilers

ALEXD.COBB, JR................................ 73

Marketing Urban Wood Residues

JOHN W. HOWARD ............................... 81

Segregation Processes for Urban Waste Wood

JOHN A. STUROS ................................ 85

Importance of Wood as an Urban Energy Source

JAMESW.McMINN ............................... 95

Recovery of Energy from Solid Waste-An Alternative

to Landfill Disposal

GLORIA A. MILLS. .............................. 100

TOPIC III: PLANNING ...................................... 109

ABSTRACTS ..................................... 110

Legal and Environmental Issues Surrounding Urban Waste Wood

GEORGE L.WHITMER. ........................... 111

Coordinating Producers and Consumers of Urban Wood Residues

EDWARD A. LEMPICKI ........................... 117

Urban Waste Wood: The Challenge and the Future

RICHARD PARDO. .............................. 121

REGISTRATION LIST ...................................... 124

-íV

TOPIC 1

THE RESOURCE SITUATION

ABSTRACTS

CORDELL and CLEMENTS

Urban Waste Wood: A National Perspective.-Large amounts of metropolitan solid wastes

(MSV) are produced each year in this country. Of this potentially important resource, wood

waste is vastly underutilized. In the future, recovery and reuse of wood waste will become a

more viable and attractive option. Comprehensive study of the resource and altemative programs of utilization are needed.

DENNISON

FIBREST-A Tool for Quantifying and Qualifying Wood Residues.-A computerized

accounting system, FIBREST, has been developed to aid the assessment of wood fiber residues generated in urban areas. Computed from survey questionnaires, residue amounts can

be reported by industry, county, and town/city sources in 10 form categories and 3 disposal

classes.

LOGGINS

Composition of Landjilled Urban Waste Residues.-Purpose of the study was to determine

various quantities of wood waste being landfiied in the Atlanta metropolitan area. A survey

was completed during the summers of 1977 and 1978. Information collected emphasized a

large volume of potentially useful urban wood residue that was being wasted.

DAVIS

Source Separation-Procedures and Practices.-Urban programs in source separation of waste

wood in New Jersey center economically on two types of programs, those which expect

remuneration and those which do not. Those with a future tied only to the public-service

aspect appear to have the greatest potential for survival.

COMMINS

Determination of Wood Content in Demolition and Construction Wastes.-Demolition and

construction waste streams were evaluated on a national basis by a unique combination of

empirical and predictive techniques. National figures developed indicate 55 million tons, the

waste wood fraction of which is 22 million tons, representing 2 percent of the heating value

of all U.S. coal production.
URBAN WASTE WOOD: A NATIONAL PERSPECTIVE

H. Ken Cordel1 and Thomas W. Clements’

Abstract.-Large amounts of metropolitan solid wastes (MSW) are

produced each year in this country. Of this potentiahy important

resource, wood waste is vastly underutihzed. In the future, recovery

and reuse of wood waste wiII become a more viable and attractive

option. Comprehensive study of the resource and alternative programs of utihzation are needed.

A tour of any landfill in any metropolitan U.S. City in any year Will revea1 that

Americans, either as individuals or through business or government, are discarding

large amounts of possibly reusable material. Over 90 percent of this metropolitan

solid waste (MSW) is landfilled, burned, or dumped into the otean each year (Grinstead 1970).

Methods of raw material extraction and refinement and product manufacture

and distribution have been in the center of technological and economic concern. But

these systems, coupled with social concerns, have noticeably excluded the recovery of

solid waste. Modern methods of managing solid waste as a resource are only slowly

being incorporated. In light of a growing population, increasing prosperity and consumption, and a diminishing resource base, it is of vital importance that waste of al1

sorts be reduced through methods of solid waste recovery.

The U.S. Forest Service is charged under the National Forest Management Act of

1976 (U.S. Congress 1976a) to investigate the recovery of waste wood materials.

Through this investigation, it is hoped, a more conscientious program of resource utilization will evolve. Urban waste wood is an integral part of such management.

ESTIMATES OF QUANTITY

There are many different and somewhat conflicting estimates of the amount of

solid wastes in the Nation. Among these, figures from the Environmental Protection

Agency give an idea of the magnitude of the solid waste resource in the United States.

For 1971, EPA estimated that nationally there were 4.45 billion tons of solid waste.

These estimates include much mil1 and mining waste, most of which is rurally located.

Wood and paper, however, make up significant proportions of the solid waste total;

by weight, in 1975, about 4 percent was wood. The dramatic increase in product packaging since 1945 is largely responsible for these high percentages.

Wood reuse, particularly of manufacturing waste, is increasing. In 1974, the

USDA report entitled “The Outlook for Timber in the United States” indicated that

approximately 2.8 billion cubic feet of slabs, sawdust, veneer cores, and other such

materials were being reused for particleboard, pulp, fuel, and other products (USDA

I

r The authors are, respectively: H. Ken CordeII, Project Leader, Urban Forestry Research in the

South, Southeastern Forest Experiment Station, Forestry Sciences Laboratory, Athens, Georgia;

and Thomas W. CIements, Research Technician, Urban Forestry Research in the South, Southeastern Forest Experiment Station, Forestry Sciences Laboratory, Athens, Georgia.

3
FS 1974). This figure represents an í8-fold increase since 1952; however, in 1970,

1 billion cubic feet of manufacturing waste wood still was not being used.

It is important to note that urban waste wood in general is much more contaminated than manufacturing wood residues. EPA estimates that of the nearly 5 billion

tons of solid waste, about 9 percent (450 million tons) is classified as MSW. Of this

MSW, about 3.6 percent (16.4 miIlion tons) ís wood. This wood is mixed with and

joined to all manner of debris. Reuse of urban waste wood is a complex undertaking.

Estimates of the amounts of urban waste wood, by source and use, have been

provided by Carr (1978). Table 1 shows that urban waste wood totals about 16.4 million tons and urban waste paper about 44.5 million tons. Together these total 61 million tons of reusable resources.

Table l.-Sources and uses of urban wood waste (approximate annual figures)

Source I Quantity (airdry tons)

Million Percent

Wastepaper 44.5 15 13

Waste timber products 13.662 22

Trees 2.800 5

Total 60.977 100

Current disposals of tiese wastes are for:

Quan tity

Fiber and Allied Products Million

Wastepaper 12.330

Waste timber products 1.697

Trees 0,140

Total 14.167

Energy

Wastepaper 1.000

Waste timber products 1.814

Trees 0.280

Total 3.094

Landfill, Dump, Incineration, etc.

Wastepaper 31.185

Waste timber products 10.151

Trees 2.380

Total 43.716

Total resource recovery (fíber and allied products of energy) equals 17.261 million tons, or 28

percent of annual formation.
Of this total, only 28 percent (17 million tons) currently is bemg used (fig. 1).

Uses include fiber and allied products (14 million tons, 82 percent) and energy (3 million tons, 18 percent), as shown in figure 2. Seventy-two percent (44 million tons)

currently goes into landftis or is incinerated.

Large cities have massive amounts of waste wood. For example, Chicago has

estimated its wood to exceed 400,000 tons; Atlanta has about 75,000 tons per year

and 80,000 cubic yards of leaves; and Minneapolis-St. Paul has over 300,000 tons of

elm waste wood alone per year.

Figure l.-Chipping of Dutch elm diseased trees on the University of Georgia campus.

SOURCES OF URBAN WOOD

The major sources of urban waste wood are: municipal agencies, which remove

wood from residential trimmings, construction sites, and Street trees; commercial

users, who discard such things as pallets and packaging; and industries that manufacture fmished products such as furniture.

Waste timber products account for 13.662 million air-dry tons per year and tree

disposal 2 million air-dry tons per year. Of the waste timber products, 47 percent is

demolition debris, 31 percent is pallets and containers, 4 percent is dunnage, and

18 percent is from wood product manufacturing (Carr 1978).

According to “The Outlook for Timber in the United States” (USDA FS 1974),

about 900,000 units of housing are demolished each year. Because about 75 percent of

5
Figure 2.-Wood chips falling from a tire shredder-Cobb County, Georgia, landfii-may be utilized

by paper companies.

the U.S. population lives in urban areas, most of this housing demolition is urban.

Demolition wastes are, unfortunately, not homogeneous and thus pose problems

in the removal of contaminating nonwood materials. But the sheer volume of this

resource coming from easily identified points of origin strongly favors reusing these

wastes.

Housing starts also contribute huge volumes. Estimates are that about 2.5 million

new units of housing will be built each year during the 1970’s (USDA FS 1974).

Unused construction lumber and trimmings increase as the number of new units

increases. A report for the EPA by the JACA Corporation (1977) estimates tonnage

for construction and demolition waste at 21.9 million tons annually. Demolition waste

wood accounts for 19.3 million tons, and construction wastes account for 2.6 million

tons.

6
Certain forms of packaging, especially at the retail level, are used only once before

disposal. Heavy-duty packaging such as trates, boxes, and dunnage may be reused

industrially and commercially, even though lifespans are short. Pallets have a lifespan

of about 3 years (USDA FS 1974) before they enter the waste stream. Approximately

205 million pallets were made in 1974 (USDA FS 1974), so there should be an even

larger number entering the waste stream today. Better design and use of stronger

materials may lengthen their lifespan, but in time al1 these materials will become waste.

The greatest single contributor of waste wood in many cities is municipal government itself. Since the government must prune and remove a large number of trees on

municipal lands and streets and since the average lifespan for a city tree is only 10

years, it is not surprising that large volumes of tree removal and pruning materials are

generated.

Dutch elm disease alone has had great impact on the vegetative cover of many

cities (fig. l), especially northern cities where more than half of the planted trees were

elm. In cities such as Chicago and Minneapolis-St. Paul, there is a flood of elm wood.

Leaves and limbs of elm trees have a high volume-to-weight ratio and create problems

at landfills where fnl space is very limited. Utilization of this elm wood would be very

beneficial.

LEGISLATION CONCERNING WASTE WOOD

Laws in the United States to encourage recycling or to discourage waste are few

and weak. The problems and some opportunities with solid wastes have been recognized for many years, but the approach has been to dispose of solid waste rather than

to reuse it.

The Solid Waste Disposal Act of 1965 (U.S. Congress 1965) was one of the first

attempts by Congress to address the issue. Its main focus was on dump and landfill

practices and on environmental protection through safer disposal procedures. The Act

also called for conservation of natural resources by reducing solid waste disposal.

The Resource Conservation and Recovery Act of 1976 (U.S. Congress 1976b) is

ful1 of language encouraging-and even requiring-planning to recover materials from

solid waste. Each state is required, under the guidelines of the Act, to have in its solid

waste management plan some discussion of recovery and recycling; however, there are

no requirements for implementation of those plans, so participation is voluntary.

The U.S. Forest Service is involved in the recovery of urban waste wood through

the National Forest Management Act of 1976 (U.S. Congress 1976a). The Forest

Service has a legislative mandate to determine the reuse potential of urban waste wood,

but the reduction of waste, which is a key to the problem, is not addressed.

An innovative prograrn was begun by the State of Oregon in 1967 to encourage

recycling and environmental protection. A law was passed which provides tax relief

“to encourage the construction, installation, and use of facilities to prevent, control,

or reduce air, noise, or water pollution and to utilize solid waste by providing tax

relief for persons who do so” (State of Oregon 1967, Sec. 1). The law was amended in

1973 and 1975 to allow for tax benefits to certified solid waste facilities. “Such a

facility to be certified must produce as an end product a usable source of power or

other item of real economic value . . .” (State of Oregon 1967, Sec. 2.B).
REUSE PROGRAMS IN THE UNITED STATES

In the U.S. it is difficult to fmd successful urban waste wood recovery programs

which are not tied to energy production. Either there is not enough information about

nonenergy uses, or the economic returns from such uses have not been sufficient. Most

likely, this lack of success has been due to the new interest in recycling resources,

which has only recently prompted investigation of utilization methods.

Use of wood for energy is perhaps the easiest option, since energy is a universal

use for all forms of wood. But this is a final use; the possibility for any further reuse is

gone once the wood is converted to energy.

Other uses of wood include transformation into other products, such as particleboard or woodchip mulch. From many of these uses, production of energy from waste

wood is still an option.

USE FOR ENERGY

Numerous wood-processing companies have begun to use their own waste wood to

supplement the energy needed for their operations. It has become standard procedure

for companies such as Weyerhaeuser and Georgia-Pacific to burn waste wood for

energy rather than to dispose of it. Most of these plants are located in rural areas, so

little urban waste wood is involved, though use of urban waste wood by paper companies in Georgia has been investigated. Wood from the Cobb County landfill (in MetroAtlanta) has interested Georgia Kraft, and wood from the Chatham County (Savannah)

landfill is wanted by Union Camp. At both landfill sites, the incoming wood would be

chipped and transported to the plant site (fig. 2).

In another example, wood from the DeKalb County landfiu (mar Atlanta) is

already being chipped and sold. The results are not very promising at this time, however, because of small volumes of wood.

In Portland, Oregon, a company called Grenco, Inc., is purchasing dunnage,

pallets, demolition debris, and other waste wood from manufacturers. By a chipping

and contaminant separation process, they are creating material used as boiler fuel and

in hardboard manufacturing. Reports from the plant indicate a steady delivew of

chipped demolition debris from Portland to energy users.

Large-scale use of wood for fuel to produce electricity is underway in Burlington,

Vermont. The City is now operating a lo-megawatt generation plant fired solely by

wood. Burlington also is building a new 50-megawatt plant. Some urban garbage containing urban waste wood will be burned in this new plant . Two tons/hour/megawatt is

needed for electricity generation; thus, a larger amount of wood is needed than could

possibly be provided through use of the city’s waste wood.

Pelletizing wood to be burned for energy is apparently gaining acceptance. Aleader

in the use of this process is Woodex, Inc., of Brownsville, Oregon. The plant is particularly efficient and has a daily capacity of 125 to 300 tons of wood and agricultura1

waste. Although this plant uses mostly logging wastes, the process demonstrates a

technology applicable to urban waste wood.

Different methods to derive energy from wood are through pyrolysis and gasification. In both processes, wood is subjected to high temperatures in an oxygen-poor

8
environment, converting the wood into either oil, gas, or combustible char.

The Georgia Forestry Commission has been involved in research on these methods,

and two companies in Atlanta are currently using gasification to operate hardwood dry

kilns. Although urban wood is not currently used very much, application of this technology seems to be viable. The State of California is investigating pyrolysis of agricultural wastes. A number of cities are either burning their garbage for energy or planning

to do so. Since wood is only a small constituent of this garbage, these efforts are of

only passing interest. Ames, Iowa, is perhaps the best-known example of sohd waste

disposal through burning of refuse for fuel. The U.S. Navy has also been a leader in

this area.

Tacoma, Washington, and Columbus, Ohio, are soon to begin energy recovery

from garbage. This is “high technology” since large amounts of machinery and

energy are necessary to keep the process going. A low technology approach to the

garbage problems would be source separation where different kinds of recoverables,

such as glass, paper, metal, and wood are separated at the point of discard, such as a

home or business.

A few cities have been involved in impressive attempts to solve their waste wood

problems. In these attempts, energy production has been the major product in cities

such as Chicago, Madison, and Minneapolis-St. Paul. The amount of wood in Chicago

could be as high as 1,000 tons of ovendry material per day. Estimates are that Chicago

and surrounding municipalities remove 450,OPO tons of tree debris annually and that

dunnage and demolition waste may exceed 200,000 tons annually. The City hoped to

find someone to utilize this waste wood for conversion to energy when it began looking

at the problem in 1976.

Commonwealth Edison, the major energy producer in Illinois, had no interest in

this waste wood, however, because of perceived technical and economic drawbacks.

Other potential sources were identified, including Grenco Company of Portland, Oregon, but no guaranteed outlet for disposal was located.

The Metropolitan Sanitary District of Chicago also expressed an interest in the use

of chips with their sludge composing project. Hopes for large-scale uses of Chicago%

wood debris through burning, particleboard manufacture, or other use, however, have

not been realized. Costs of collection, separation of foreign matter, processing, storage,

and transportation have thus far seemed too high.

Madison, Wisconsin, and St. Paul are other cities which have actively studied the

possibilities of using waste wood. Only limited success has thus far been realized.

NONENERGY FORMS OF REUSE

The number of programs, successful or otherwise, involving recovery of nonenergy

waste wood is relatively small. Rut there are signs that technology is being generated

and that some success is being achieved. Perhaps the simplest type of operation is

represented by a project established in Birmingham by the Alabama Forestry Commission. At a recycling center, paper, glass, and aluminum are brought in, already separated, and exchanged for firewood or wood chips from trees on city lands. In this

manner, the recycling center is paying for itself through receipts from materials sold.
Birmingham, which earlier was uninterested in the project , has recently expressed

strong interest in becoming more active in such an operation. Huntsville, Alabama, is

undertaking a similar project. These low technology operations may be a key to future

waste disposal. The cost of separation is spread over large numbers of people, as perhaps it should be.

Other cities involved in nonconventional waste wood disposal include Toledo,

Ohio; Lansing, Michigan; and Atlanta. Lansing, forced by law to eliminate landfilling

and open burning of wood, adopted incineration and utilization through production of

firewood, rough lumber, wood chips, bark chips, and sawdust. In 1970, that utilization

program, run by a private company, went bankrupt and the city began chipping all of

its own small wood to use on trails, as mulch in flower beds, and for various uses in

parks. All other waste wood that the city generates is taken to a firewood yard which

is open, 2 days a week, to residents.

Toledo, Ohio, also forced to eliminate open burning, devised a recycling program

for brush and logs. End products anticipated from the operation were: wood chips for

mulch in city parks, logwood chips for paper companies, firewood for public sale,

fencing and pavers, and solid logs for use in playgrounds or for sale to sawmills. Down

time caused by damage to machinery from metal contaminants in the wood caused

problems in the operating costs, but officials felt that what is being learned about the

use of waste wood and the environmental benefits assure that the effort will eventually

pay off.

Atlanta has successfully implemented a program to divert City-generated waste

wood from being landftied. The city has over 5,000 miles of rights-of-way and 4,000

acres of municipal land to maintain. On these lands there are an estimated 1.5 million

trees under the city’s care. Normal maintenance produces large amounts of waste

wood from pruning and removal. The Atlanta program involves: free firewood yards,

wood chips, and composting. The programs to use self-generated waste run smoothly

in Atlanta, but thousands of tons of private waste wood are still not reused and

continue to be landfilled.

Use of wood chips with sludge composting has been subject to experimentation at

the U.S. Department of Agriculture test facility in Beltsville, Maryland. Implementation of a sludge composting project has occurred also in Ft. Lauderdale, Florida.

Wood from construction sites is purchased, chipped, and then mixed with sludge to

allow aeration, which causes quicker breakdown of the sludge.

Kellbro Corporation in Sacramento, California, makes mulch and garden additives

from mil1 wastes, demolition wastes, and Street trees. The company was producing a

fiberboard from waste until its sources were depleted, but success with its mulching

product seems to be established.

The manufacture of fiberboard and chipboard is a growing industry because of

better technology. The Medford Corporation in Medford, Oregon, makes a medium

density fiberboard utilizing plywood trim, planer shavings, and sawdust. The material

is refined and reduced to wood fiber, dried, and formed with resin into boards. Most

of this waste material is not now urban, but much of it would be landfiled or burned

if not used for fiberboard.

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Williard’s Sawmill in Trenton, New Jersey, is another example of urban waste

wood reuse. Trees cut from city rights-of-way and from private lands are purchased by

the sawmill and made into special products, including tabletops, plaques, clockfaces,

and lumber .

One successful program is administered by the New Jersey Bureau of Forestry.

Through this program, businesses generating wood residue are matched with those

which have a use for the materials. This Statewide program began with a preliminary

feasibility study in 1970 and was implemented in 1972. Currently, four people are

working with the project .

Examples of reuse include sale of turned material to a toy manufacturer and sale

of bay-window corners to a company which makes plaques and foot pedals for drums.

In 1977 about 2 million cubic feet of waste wood were recycled, with a savings of

over $900,000 to New Jersey businesses.

A thorough inventory of industry in a city or region would discover possibilities

for more efficient reuse of waste wood.

SUMMARY AND CONCLUSIONS

Our estimates of the amount of MSW are not very good at this time. Generally,

we estimate that there are approximately 500 million air-dry tons of MSW annually.

Between 16 and 17 million tons of this MSW are some form of wood. Of this, we

currently use only 28 percent for products or energy.

As is the case with solid waste in general in the U.S., we seem to be vastly underutilizing a potentially important resource. It is our strong conviction that, for a number

of reasons, recovery and reuse of urban wood waste will become a more viable and

attractive option in the near future. To realize the full potential of this option, we

should now begin planning programs and conducting research (frg. 3). Our reasons for

suggesting the growing feasibility of urban waste wood recovery include:

Figure 3.-Whole-tree chippers, as used here by Georgia Forestry Commission, may be useful in

future urban wood utilization programs.

l l
1. Rising costs and decreasing availability of forest-derived, primary wood for

paper, fiberboard, and similar manufacturing are making alternative sources of wood

fiber more attractive. Income derived from using urban waste wood, even though not

enough to cover recovery costs, will help offset the costs of waste disposal. This potential income should continue to increase at least as fast as disposal costs and thus should

be viewed as a buffer against rising costs.

2. Demand and costs for energy are rising at high rates. As the cost of energy

increases relative to other costs, the option of using wood (and other organic wastes)

for energy production becomes more attractive. The Energy Research and Development Administration has estimated that by 1985 the U.S. will have a quantity of solid

waste available to produce the equivalent of 500,000 barrels of oil per day.

3. Costs for landfilling operations and sites are increasing. In addition, space for

landfilling is becoming limited, to the extent that locations are often difficult to find.

As these costs rise, resource recovery and waste wood utilization become more and

more attractive as a means of reducing disposal costs for al1 solid wastes. Comprehensive recovery programs can reduce solid waste volumes by 7.5 to 95 percent.

4. Technology for waste wood recovery seems to be in its infancy. Systems

designed to produce energy, separate usable wood and other resources, and involve the

public have been tested in only a few locations for relatively short periods of time;

thus, some of the negative conclusions are perhaps premature. There are too many

success stories and too many changing conditions to conclude that wood recovery is

not feasible. We should keep in mind that there are many objectives involved. Among

these are: environmental protection through reduction of solid waste; resource conservation through reuse; and partial cost recovery.

If we look only at any one of these, waste wood recovery can be viewed as a failure.

If we consider all simultaneously , acceptable and sufficient returns will be realized.

One of the bigger needs in this area is for comprehensive study of the resource,

alternative programs of utilization, and the cost-return schedules associated with each

alternative. Thus far we really haven’t done this.

Ultimately we will have to reuse whatever resources we can. We should begin

planning and testing alternatives now so that we are prepared for these future needs

and so that we are creating a better urban environment .

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LITERATURE CITED

Carr, Wayne F., and John N. McGovem

1978. Report on urban wood waste in the United States of America. Unpublished report

Prepared for U.S. Dep. Agrie. For. Serv., For. Prod. Lab., Madison, Wii.

Grinstead, Robert A.

1970. The new resource. Enviromnent 12(10):2-17.

JACA Corporation

1977. Energy potential from construction and demolition wood wastes. p. 1. Off. Solid

Waste, U.S. Environ. Prot. Agency, Washington, D.C.

State of Oregon

1967. Polhttion control facility tax relief in Oregon. Chapter 52, Oregon Laws 1967.

U.S. Congress

1965. Solid waste disposal act of 1965. 79 Stat. 992. Public Law 89-272.

U.S. Congress

1976a. National forest management act of 1976. 90 Stat. 2949. Public Law 94-588.

U.S. Congress

1976b. Resource conservation and recovery act of 1976. 90 Stat. 2795. Public Law 94-580.

U.S. Department of Agriculture, Forest Service

1974. The outlook for timber in the United States. For. Resour. Rep. 20, p. 30,150-159,

174-177.

1 3
FIBREST-A TOOL FOR QUANTIFYING AND QUALIFYING

WOOD RESIDUES

Steven E. Dennison’

Abstract.-A computerized accounting system, FIBREST, has been

developed to aid the assessment of wood fiber residues generated in

urban areas. Computed from survey questionnaires, residue amounts

can be reported by industry, county, and town/city sources in 10

form categories and 3 disposal classes.

INTRODUCTION

Wood fiber waste is produced in a wide array for forms, types, and conditions.

Familiar examples are sawdust, bark, edgings, trim, and various types of paper materials. Other types include pallets, telephone poles, broken furniture, wooden containers,

and limbs and brush from yard and tree maintenance.

Depending upon the source, one or more types of residue may be generated at the

same locale. Sawmills generate bark, sawdust, edgings, trim, and chips as byproducts.

Residential and commercial sources produce newsprint, cardboard, trates, and pallets

as discards, while a printing and publishing firm may throw away paper cutoffs and

trim .

Our failure to apply either modern management or modern technology to the

ultimate disposal of this abundance has resulted in a monumental solid waste problem.

Federal legislation, such as the Solid Waste Disposal Act of 1965 (Black 1970), the

Resource Conservation and Recovery Act of 1976 (McGlennon 1977), and the National Forest Management Act of 1976 (Foley 1976), has focused attention on the

need for recovery of these materials from the Nation’s trash.

Approaching the problem from another aspect, many states and communities

(Mass. DEH 1971; Massey and Dunlap 1975; US EPA 1975) are setting specific guidelines for sanitary landfills to cope with the volume of waste material. These guidelines

may include strict regulations for burning, salvage operations, and the disposal of

woody materials. In the last decade, municipal governments, wood-using industries,

and other private firms have also been turning to these solid waste piles as a source of

material to help defray the rising costs of energy, raw material, and disposal.

WASTE MEASUREMENT

For the potential user of residue materials, information must be obtained on their

availability and reliability as a resource, their location, and the forms in which they are

generated; however, to date there have been no consistent, comprehensive methods for

collecting and reporting this information. The heterogeneous nature of residue material makes detailed measurement difficult. As a result, most of the completed inventories were done for specific reasons and the results reported in an array of units, thus

making comparisons difficult .

I

‘Graduate Research Assistant, Department of Forestry and Wildlife Management, University

of Massachusetts, Amherst, Massachusetts.

14
Severa1 efforts aimed at waste analysis (Combustion Engineering 1969; Ingram

and Francia 1968 ; Muhich and others 1968) were undertaken using funds provided by

the Solid Waste Management Act of 1965. These studies, for the most par-t, were

national in scope and resulted in the reporting of waste-per-capita averages for the

country as a whole.

A new approach in the prediction of solid waste amounts and components was

introduced by the URS Research Company (Black and others 1972) in 197 1, under

contract with the U.S. Environmental Protection Agency. This method uses a material

flow locus which assumes that waste generated in an area is derived primarily from the

goods and services consumed in that area. A synthesis approach is used in which estimates and predictions of residuals are based on knowledge of materials and quantities

before they become a part of the solid waste stream.

Despite the obvious advantages of this system, it is not without its drawbacksthe main one being the cost of implementing the system. An inventory of al1 wasteproducing activities in an area must be conducted to compile standard information on

the materials consumed per unit size and time for each activity type, as well as to define which of these materials become waste. Smith (1975) also points out that wastes

not passing through a production sector (e.g., removal of Street trees) will cause

incorrect estimates in using this type of system.

Other studies, such as those conducted by Burry (197.5), Frame (1974), and

Quink and others (1974), used surveys designed to quantify the multiple forms of

wood residues in order to encourage their utilization. These canvasses, although inexpensive to implement and designed for specific purposes, found that conversion figures

varied widely.

Because of the marginal value of wood wastes and the economic constraints

surrounding materials flow data, residue inventories usually resort to the canvassing

format. Letter questionnaires and personal interviews, if properly designed and pretested, provide a relatively easy and inexpensive method of data procurement. The

major problem with this type of system is that there is no general form to follow in

analyzing the data. Each inventory is unique when it comes to conversion figures and

measurement units.

The remainder of this paper will discuss another inventory system, FIBer Residue

ES?‘Imation (FIBREST), which deals with the problems associated with the common

canvassing format (Dennison 1977).

FIBREST SYSTEM

FIBREST is a wood residue computer-accounting system written in standard

ANSI FORTRAN; it is designed to analyze industrial wood residues in urban areas.

It examines survey returns, is flexible in its use, and attempts to present the output

data in a rational, readable fashion.

It will accept a variety of measurement units, while providing an estimate of wood

residue amounts in one reporting unit for a given region. FIBREST will report these

amounts according to their location, their form, the degree to which they are contaminated, and how they are currently disposed.

1 5
SYSTEM INPUTS

Obtaining a list of wood residue generators (the starting point for conducting the

inventory) is often the most arduous task of the whole process. Sources that would

help in compilmg this list may include state industrial directories, state and local

Chamber of Commerce indexes, Extension Service lists, and as a last resort (although

often a good source), the yellow pages and classified advertisements in the area to be

surveyed .

As this information is obtained, each waste generator should be ceded numerically

by location (town, county, state, etc.) and by its Standard Industrial Classification

(SIC) number. SIC codes can be found in the U.S. Department of Commerce’s “Standard Industrial Classification Manual” (USOMB 1972). If waste producers other than

industry are surveyed (e.g., city/town tree maintenance departments), other codes can

be added. A partial listing of the types of wood residue generators which might be

included is shown below.

SIC Descriptor

0783 Ornamental shrub and tree services

1522 General contractors

1795 Wrecking and demolition crews

2421 Sawmills and planing mills

2448 Wood pallets and skids

2499 Miscellaneous wood products

2642 Envelopes

2711 Newspapers, publishing

3732 Boatbuilding and repairing

3994 Caskets

From this listing the FIBREST system is capable of handling a 100 percent sample

or a partial sampling scheme.

SURVEY INFORMATION

Data requested on the questionnaire, in order to conform to FIBREST, should

include :

1. The amount of residue produced (an estimate often has to suffice) in some unit

and time peiiod .

2. A percentage estimate of the amount produced in any or al1 of 10 different

form classes (e.g., chips, pallets, paper).

3. A percentage estimate of the waste produced that is contaminated.

4. A percentage estimate of the waste material in each of the following categories:

waste being used by the generator, waste that is sold or given away, and

waste actually going to a disposal site.

Each survey response-the amount, the measurement unit, and the percentage in

the above categories-is recorded in a consistent manner on computer processing cards

according to SIC and locational codes.

16
AREA PARAMETERS

In order for the survey information to be properly sorted, other data must also be

compiled and ceded. These data include the SIC codes and descriptors being inveñtoried as well as the total number of firms in each class. Place names and locational codes

of the govemmental units and associated subunits of the area in the survey (e.g., counties and towns) are also used. Optional information includes populations as well as the

number (and size) of disposal facilities in each subunit.

CONVERSION PARAMETERS

The uniqueness of FIBREST lies in its ability to accept the variety of measurement

units associated with the residue amounts on the survey responses and to convert them

to a specified reporting unit. It is this capacity that also allows for a comparison with

other wood residue inventories.

The system constructs 12 tables, each containing a matrix of conversion figures.

These figures are calculated from eight variables (supplied by the user) associated with

wood fiber materials. For illustrative purposes, the variables used in a test of the program are listed below :

Moisture condition

(green basis) = OSO (dry is 50% of wet)

1 uncompacted cord= 75.0 cubic feet

1 uncompacted cord= 500.0 board feet

1 compacted cord = 128.0 cubic feet

1 cord, softwood

(uncompacted) = 2.5 tons (green)

1 cord, hardwood

(uncompacted) = 3.0 tons (green)

1 cubic yard, paper

(uncompacted) = 190.0 pounds

1 cubic yard , paper

(compacted) = 500.0 pounds

The conversion tables are then used in FIBREST as each survey return is analyzed.

Using the ceded measurement unit on each response, the total amount of residue is

converted to the predetermined reporting unit selected from the following list:

dry tons wet tons

dry pounds wet pounds

dry cubic feet wet cubic feet

dry cubic yards wet cubic yards

dry board feet wet board feet

dry cords wet cords

The system is currently being modified to include BTU as an additional reporting unit.

17
SYSTEM OUTPUTS

The residue amounts are calculated, expanded to totals, and sorted for each location

unit (e.g., SIC, governmental units). The data are then generated by FIBREST in tabular form. This accounting format allows the residue user to examine more accurately

the resource situation in the survey area.

In addition to choosing a reporting unit, the user of the system may choose any or

al1 of the following forms of output:

1. Residue account, by the source of generation (SIC).

2. Residue account, by each major administrative unit (e.g., county).

3. Residue account, by each subunit (e.g., city/town).

4. Conversion tables.

5. Return statistics of the survey .

6. Multiple listings of the above choices.

If none of these options is chosen, the output consists of a single table summarizing

the residue amounts in the surveyed area. This summary includes the physical components (forms) of the residues and how they are disposed-al1 by each SIC (source) code.

Table 1 is a partial illustration of this summary table.

Table l.-Sample summary table showing physical components and disposal methods

Type of wood residue generators

General

Physical Shrub and wood Grand

components tree services products Envelopes Caskets total

(0783)’ (2499)’ (2642)’ (3994)’

. . . . . . . . . . . . . . . . Percent. . . . . . . . . . . . . . .

Wood fines

Sawdust

Edge trim

Limbs

Chips

Bark

Paper

Misc. board

PaIIets

Other

- -

- 28

- 32

48 -

43 2

6 1

- -

- 24

- 12

3 1

- - -

- 3 18

- 3 21

-

- 16

-

- 1 5

-

- 3

100 - 0

-

- 1 6

-

- 8

- 94 3

Estimated total (Dry tons) 6,948.7 13,711.9 26.7 218.2 20,905.5

Disposal Methods Used

Internal usage

Sold OI given away

Waste disposal facility

. . . . . . . . . . . . . . Percent . . . . . . . . . . . . . . .

24 28 - - 26

54 63 - 100 60

22 10 100 - 14

r Standard industrial classification code.

18
Table 2 provides an example of the residue account for one industry type in a

region that was surveyed. Each of the other residue accounts is generated in tables of

similar construction.

Table 2.-Sample residue account for one industry’

Estimated amounts of wood fiber residues (dry tons)

Residue Survey

amount

Population

estimation

Wood fines 10.46 18.31

Edge/trim 415.50 721.13

Chips 1.20 2.10

Paper 0.00 0.00

Pallets 0.00 0.00

Sawdust 1,666.99 2,911.23

Limbs 0.00 0.00

Bark 409.50 716.63

Misc. board 0.00 0.00

Other 1,638.OO 2,866.50

Contaminated 0.00 0.00

Estimated Disposal Amounts

Interna1 usage 0.00

Sold or given away 3,638.25

Waste disposal facility 503.40

Estimated total amount 4,141.65

‘Suiurvey statistics:

Net sent 7 Percent sample 100.00

Net return 4 Percent return 57.14

Population correction factor 1.75

0.00

6,366.94

880.95

7,241.89

UTILIZATION OF FIBREST

A mail survey of 600 wood-using industries in three central Massachusetts counties

(which included 69 cities and towns) provided a practical test for the FIBREST

system.

Results tabulated by FIBREST indicated an estimated amount of 679,000

dry tons of wood fiber residues calculated from a 27 percent return of the two-page

questionnaire. Interestingly, 68 percent of that amount was contaminated, having been

generated by wrecking and demolition firms in the region.

Soon after this test, a private concern in the area, seeking to burn clean residues in

place of fossil fuels, conducted its own survey to determine the availability of uncontaminated waste wood. The findings closely paralleled those figures generated by

FIBREST in the uncontaminated categories (Johnson 1977).

To the potential user of wood residues, FIBREST provides the opportunity to

assess more accurately the availability of the resource. By tabulating, locating, and

19
describing the amounts of waste wood in an area as well as noting its current disposition, the user will be better equipped to make decisions on what is, normally, a

marginal resource. With these capabilities, the system can be used for individual assessments of the residue situation. Or, with its flexibiIity of reporting modes and conversion parameters, it could be used to compare different waste wood inventories.

In conclusion, a note of caution is in order. For any inventory, the degree of

accuracy desired (in the measurement and reporting of data) is directly dependent

upon considerations of cost and scope. If estimates of wood residue amounts are used

in FIBREST, then only extensions of those estimates will be reported.

As the potential of residues becomes more widely recognized and their need as a

resource more acute, waste wood measurements should become more than just estimates. Only then will FIBREST, and other systems like it , be precise tools for resource

management .

LITERATURE CITED

Black, R. J.

1970. Present practices and future trends in solid waste management. Zn New Directions in

Solid Waste Processing. Proc. Inst. Tech. Guid. Cent. for Ind. Environ. Control,

Amherst, Mass. p. 4-9.

Black, R. H., R. R. Fielder, M. B. Hawkms, and R. 0. Strom

1972. A planning model for the prediction of residential and commercial solid wastes. URS

Res. Co. for Off. Solid Waste Manage., U.S. Environ. Prot. Agency. 123 p.

Burry, H. W.

1975. Personal communication. Wood Util. Serv., SUNY, Syracuse, N.Y.

Combustion Englneering, Inc.

1969. Technical-economic study of solid waste disposal needs and practices. 4 ~01s. U.S.

Public Health Serv., Publ. 1886, sw-7c.

Dennison, S. E.

1977. An inventory of industrial wood fiber residues in the Connecticut River Valley counties of Massachusetts. M.S. Thesis (Unpubl.), Univ. Mass., Amherst. 207 p.

Foley, R.

1976. Report on the National Forest Management Act of 1976. Congr. Rec. 122(150):

H11837. (Sept. 30,1976).

Frame, E. D.

1974. Virginia forest products residue study, 1974. Va. Div. For. & Lumber Manuf. Assoc.

ll p.

Ingram, W. T., and F. D. Francia

1968. Quad-City solid waste project-an interim report. Publíc Health Serv., U.S. Solid Waste

Program. 153 p.

Johnston, T.

1977. Personal communication. Montgomery Rose Co., Inc. Hadley, Mass.

Massachusetts Department of Enviromnental Health

1971. Regulations for the disposal of solid wastes by sanitary landfil. Mass. Gen. Laws,

Chapter 839. Acts of 1970.

Massey, D. T., and L. H. Dunlap

1975. Solid waste management law-focus on Indiana. Natl. Tech. Inc. Serv. PB252284/AS.

20
McGlennon, J.

1977. The future of solid waste management. Environ. News (U.S. Environ. Prot. Agency,

New England Reg. Off.). Jan. 1977. p. 17-18.

Muhich, A. J., A. J. Klee, and P. W. Britton

1968. Preliminary data analysis-1968 survey of community solid waste practices. U.S.

Public Health Serv., Publ. 1867.

Quink, T. F., P. K. Whitehouse, and M. A. Brouilette

1974. Wood residues-volumes and availability in the western Massachusetts area for industrial development. Mass. Coop. Ext. Serv., Amherst. 13 p.

Smith, F. L.

1975. A solid waste estimation procedure-materials flow approach. U.S. Environ. Prot.

Agency, Publ. SW-147. 56 p.

U.S. Environmental Protection Agency

1975. Third report to Congress-resource recovery and source reduction. U.S. Environ. Prot.

Agency Publ. SW-161.96p.

U.S. Office of Management and Budget

1972. Standard industrial classitication manual. Exec. Off. of the President-Off. Manage.

Budget. Washington, D.C., USGPO. 649 p.

2 1
COMPOSITION OF LANDFILLED URBAN WASTE RESIDUES

Tommy J. Loggins’

Abstract.-Purpose of the study was to determine various quantities

of wood waste being landfiied in the Atlanta metropolitan area. A

survey was completed during the summers of 1977 and 1978. Information collected emphasized a large volume of potentially useful

urban wood residue that was being wasted.

Landfill surveys were conducted by the Georgia Forestry Commission in the

summer of 1977 and again in the summer of 1978. The majority of the landfills was

located in the Atlanta metropolitan area and a smaller number in the cities of Rome

and Macen, Georgia.

The Atlanta area has increased rapidly in population and land use in the last

decade. Correspondingly, there has been an increased volume of solid waste going to

landfills and other disposal sites. An integral part of this waste stream is waste wood of

al1 types.

New emphasis is being placed on reducing waste and recycling materials whenever

possible. Since waste volumes have grown, resource potentials have increased.

Reuse can also lessen disposal and landffl problems. Disposal problems for wood

residue are greatest in urban areas because a dense population and high industrial concentration generate great amounts of waste wood.

Disposal expense, environmental regulations, lack of disposal space, and a growing

demand for wood products create an ever-increasing need to recycle or reuse those

heretofore discarded materials.

With the growing interest in energy and recycling, the Forestry Commission

became involved in determining the volumes of various wood products going into area

landfills. A total of 22 landfils was surveyed by commission personnel to determine

the relative amounts of various wood products.

This wood comes basically in two forms. Manufactured items, such as furniture,

trates, pallets, and various manufacturing wastes, represent approximately one-half

the wood residue being landfilled in the Atlanta area, according to our study results

(fig. 1). Raw wood (stumps, tree trunks, limbs, and leaves) make up the other component (fig. 2). This amount does not include the vast quantities of paper packaging that

is discarded in the area.

The survey was conducted by stationing an individual at each landfill for a 1 -week

period, typically from 8:00 a.m. until 6:00 pm., Monday through Friday; however,

hours varied and severa1 landfills were surveyed on Saturdays ako.

As might be expected, the quantity of wood residue and its overa11 composition

varied by day of the week and individual landfills (table 1). Some landfills were

’ Forester Specialist, Gwinnett County, Georgia Forestry Commission, Lawrenceville, Georgia.

22
Figure l.-Discarded palJets are unloaded into landfii.

Table 1 .-Measured weekly totals’

Tw

Junkwood

Brush

Roundwood

Stumps

Wood chips

Total

Volume

(cu. yd.)

8,886.O

5,495.6

703.2

179.9

102.8

15,367.5

\ %

57.8

35.8

4.6

1.2

.6

100.0

Weight

(tons)

740.6

512.7

77.7

135.0

36.5

1,502.5

% Cords %

49.3 296.2 49.3

34.1 205.1 34.1

5.2 31.1 5.2

9.0 54.0 9.0

2.4 14.6 2.4

100.0 601.0 100.0

’ All tables compiled by Dale Higdon from data collected during the summer of 1977. During

this period a total of 22 landfills was surveyed. These measurements included both government and

private landfihs.

located near manufacturing plants that generated large volumes of waste wood, such as

door trimmings, edgings, and sawdust. Others would receive packing trates, pallets,

and other shipping containers. Still other landfills, which catered to residential customers, would receive a large amount of tree waste in the form of trimmings, stumpqetc.

At most landfills, the material was brought in by truck, weighed, and then taken

to the dump site. At the remaining landfills, it was dumped without being weighed. In

23
Figure 2.-Typical wood residue generated in the residential areas of an Atlanta suburb.

these instances, dumping fees were based on truck volume, not weight. Truck sizes

varied from pickup loads to tractor-trailer loads hauling 50 cubic yards or more. For

commercial haulers, 25 to 40 cubic-yard loads were the most common.

The final dumping of the wood residue was of two general types. One mixed the

wood indiscriminately with the other waste, such as household garbage, plastic, etc.

This method was by far the most common since the primary purpose was to bury al1

the residue in as small a space as possible. Most commercial landfill operators did not

have any facilities for recycling.

The second method was a separation type, where al1 wood residue went to a

separate site from other waste and garbage. Only two landfills were operated by this

method, both of which were county government operations. The advantage of this

particular system was that it allowed the separation of usable wood materials, such as

24
firewood, specialty packing trates, etc., without posing a hazard to equipment operation or violating regulations.

This second method required additional work for the hauler , for foreign materials,

such as metal, wire, and garbage, had to be separated from the wood to be dumped.

The other alternative is to haul only wood products on each load, a method that

worked particularly well for government crews that hauled debris while another truck

picked up garbage from households. Tree service companies also benefited since they

haul loads composed mostly of wood.

To obtain weights of the various components of wood debris (brush, roundwood,

stumps, chips, junkwood, etc.), each load of material was weighed and its volume

determined by measurement. From this, an average weight per cubic yard was calculated for each type 01 wood waste. Based upon the data of this type collected from the

two landfills with weight scales, conversions were possible for the remaining landfills

where only volume measurements were obtained. A correlation between weight and

volume was drawn for each category (brush, roundwood, junkwood, stumps) and

species (tables 2 and 3).

Volumes were converted to cords, using weight as a factor. An average cord

weighs 5,000 pounds, or 2.5 tons. In converting stumps to cords, 90 cubic feet were

used. Cords from wood chips were tigured, using 190 cubic feet per cord (table 4).

It should be noted that since the majority of field observations was taken during

the summer months, leaves remained attached to the brush. This factor obviously

accounts for some weight that would not be encountered in the winter months.

Further, it was assumed that due to adverse weather conditions in winter, the

flow of wood residue will result in greater variability than that encountered during

the summer. Ice storms, working conditions, etc., all have an immediate effect upon

the amount of residue hauled.

Table 2.-Species composition

Species Volume

(cu. yd.) % Cords %

Pine 5,905.3 38.4 230.8 38.4

Hardwood 9,462.2 61.6 310.2 61.6

Total 15,367.5 100.0 601.0 100.0

25
Tab[e 3.-Category of classification

Category Volume

(cu. yd.) %

Weight

(tons) % Cords %

Tree parts’ 6318.7 41.6

Junkwood 8,886.O 57.8

Wood chips 102.8 .6

Total 15,367.5 100.0

,

‘Brush + roundwood + stumps.

125.4 48.3 290.2 48.3

740.6 49.3 296.2 49.3

36.5 2.4 14.6 2.4

1,502.5 100.0 601.0 LOO.0

Table 4.-Assumptions

Brush

Roundwood

Junkwood

Average weight per cubic yard

Average weight per cubic yard

Average weight per cubic yard

= 186.6 lbs.

= 221.1 lbs.

= 166.7 lbs.

5,000 lbs. (2.5 tons) per cord

Wood chips

Stumps

z 190 cubic feet per cord

= 90 cubic feet per cord

Weight of wood chips and stumps = No. cords X 2.5 tons

26
SOURCE SEPARATION-PROCEDURES AND PRACTICES

Millard C. Davis’

Abstruct.-Urban programs in source separation of waste wood in

New Jersey center economicahy on two types of programs, those

which expect remuneration and those which do not. Those with a

future tied only to the public-service aspect appear to have the greatest potential for snrvival.

Source separation programs in New Jersey are on the increase, from about 30 programs reported in 1977 (U.S. Environ. Prot. Agency 1978) to over 130 municipally

supported programs and an unknown number of private operations as of December

1978. Until now the major impetus for these recycling efforts has been the drive of

private individuals and groups. A fluctuating balance has, in most of the privately run

projects, been struck between the provider of recyclable or secondary materials and

businesses in the secondary materials market, with homeostat feedback loops keeping

the system in equilibrium most of the time. Choosing one point of entry into this

circuit, to give an example, a group decides that it needs money, locates a market for

recyclables it might sell, collects the materials, and sells it to the market. If the market,

the secondary materials merchant, can prosper very much by receiving these materials,

it will offer a high price. If the market is down, the price will drop. Naturally the

group collecting the materials will tend to match its efforts to the strength of the

market. In this way the market receives about what it needs and suppliers are repaid

for their efforts.

In the case of municipally supported recycling programs, however, long-term

contracts between the supplier (the municipality) and the market (one or more collectors or secondary materials merchants) are being encouraged by the State of New

Jersey with floor prices and escalating clauses. Now the material will tend to have a

steady flow rather than a fluctuating one.

This sort of program brings the significance of recyclables so much to the forefront

of commerce that the use and continuing reuse of secondary materials is enhanced.

For New Jersey, the New Jersey Solid Waste Management Act (c.326, Laws of

1975) and the Federal Resource Conservation and Recovery Act (P.L. 94-580; called

RCRA) operate to promulgate strong source-separation programs. The provisions of

c.326, which divide the State into 22 Solid Waste Management Districts (the 21 counties and the Hackensack Meadowlands District), require that each district, alone or

jointly with another, prepare a master plan for solid waste management. Each plan

must include an evaluation of possible programs in source separation, with the fnst

plans required to be submitted to the Commissioner of the Department of Environmental Protection by July 26, 1979, and the last ones by January 24, 1980. Source

separation of urban waste wood will be given impetus by the support given to recyc-

‘The author is with the Solid Waste Administration, Trenton, New Jersey.

27
ling in New Jersey, which a number of sources have begun dubbing “the Recycling

State.”

How much waste wood is available from municipal solid waste? According to the

“Fourth Report to Congress: Resource Recovery and Waste Reduction” (U.S. Environ.

F’rot. Agency 1977) in 1975, 1.8 million tons of wood Fackaging were discarded from

post-consumer and commercial solid waste sources; not even 1,000 tons were reported

as recycled. Of yard wastes, 26.01 million tons were discarded, and again not even

1,000 tons were recycled. Many tons of each probably were recycled, but the relatively minute figures were dropped during the production of massive accounting. What

remains as significant is the general lack of commitment to recycling of waste wood,

much less commitment to strong municipal source-separation programs, efforts which

are economic and environmental answers to economic problems.

In New Jersey the hard economics are that, while we have over 300 landfills

(serving 567 municipalities as well as the other generators of solid waste), many are

rapidly nearing capacity and others will be phased out as not meeting the “sanitary

landffl’ definitions of RCRA. Into these landflls in 1977 went 465,348 cubic yards

of vegetative wastes. Most of that probably arrived in the form of leaves, but strong

municipal composting programs could have significantly reduced that figure where

both leaves and wood were picked up for composting. In Camden County during

1977, about 19,012 tons of tree and landscaping refuse were collected from 30 (out of

a possible 37) reporting municipalities. So tight has the situation become there that

while in 1976 the county landfills served 81 percent of the population, by the beginning of 1978 only about 34 percent (or about 146,758 tons) of the county’s total

solid waste was being shipped to landfills elsewhere (Camden County (N.J.) Solid

Waste Advis. Counc. 1978).

While tree and landscaping refuse does not play a great role in the total municipal

refuse picture (about 4 percent), even a modest source-separation program could help

in that county. Neighboring counties have shown increasing resistance to filling their

landfills from Camden’s overflow.

As the New Jersey district master plans are submitted, feasible source-separation

programs will obviously be looked upon with great favor by the State reviewing

agencies. Efforts in urban waste wood utilization can look forward to a strong positive

response from the Solid Waste Administration.

What is being done currently by municipalities in the way of source-separation

programs? Two types of programs seem popular.

A. In the first type the cost of the operation is borne by the agency, with no

direct remuneration. A savings is reckoned from the potential cost of the

only other considered alternative-landfilling. Four examples stand out:

1. Collection of trees, most notably Christmas trees, by the municipality and a

free return of them to the public as chips. Usually the trees and/or other wood residues are picked up at curbside, transported to a municipal site, chipped, and then

dumped as chips at a public site on a designated day for the citizens to come and

collect _
In ene municipahty of nearly 70,000 people, an estimated 750 yards of compacted Christmas trees were last year returned to the pu& as 180 yards of chips. The

only constraint placed upon people coming to collect, which was done in the parking

lot of a local high school on two Saturday mornings, was that they take away no more

than four containers Worth; no one monitored this closely however. Fifty yards were

left over, and these went for municipal mulching needs. The cost to the town was estimated at about $200. This amount was figured on the saving of dumping costs (about

$1,200), minus labor and other direct costs, as well as those associated with owning

two chippers, valued at about $5,700 each, which are able to cut sections of wood

6 feet by 3 inches in 1 second, large ones taking longer. Such a service has been operating for 4 to 5 years.

2. Another municipality of about 58,000 people includes free 2-foot lengths of

firewood in its program. Both chips (cut up by two municipal chippers) and fnewood

are derived from trees and branches collected throughout the year and are stored at

the end of a dead-end Street where people can come for them any time. Some of the

chips are used by the municipality itself, as mulch in parks, etc., and some of the firewood is used in one of the maintenance buildings, which is heated solely by a wood

stove. Christmas trees play no role in either aspect of this program, for they are picked

up by a private collector.

3. In the case of a County Park Commission, trees are collected if there is enough

of a load; otherwise, people are welcome to drop them off themselves. About 2,100

Christmas trees were acquired under this program last year. All the trees or parts

thereof are chipped by the park, stored until spring, and then used as mulch in ornamental beds and around the Commission buildings.

4. In still a fourth situation, a municipality of about 110,000 people collects trees

and branches (as available or necessary) and chips them. Some of the chips are used by

the municipality itself as mulch; the rest are unloaded onto State property, from which

the State takes them for use in parks and elsewhere.

B. In the second type of source-separation program, there is some direct return on

the investment by making direct sales of chips and/or fnewood to individuals.

Here three cases will suffice:

1. For 8 years a pair of municipalities, with populations of about 20,000 and

6,000, has cooperated in a broad-scale source-separation program, part of which has

included Christmas trees. The program began as far back as 1970-71 with volunteers

from the community and members of the civic environmental committees, which soon

included members of the municipal Environmental Commission. From December 1971

onward, township sanitation crews were provided to handle curbside newspaper collection and to maintain the six recycling stations; in addition, there was some private

curbside collection on the monthly basis under a contract which stipulated a return of

10 percent of the income from sale of the newspaper. Heavy use was made of reminders via local newspapers, community letters and notices, radio station broadcasts,

posters, and displays. Guidebooks and programs for schools were available, and many

community groups (ecology committees, school students, scouts, League of Women

Voters, Welcome Wagon, etc.) pitched in. The intake was annually: 250 tons of waste

29
newspapers, 125 tons of glass, 60 tons of tin and aluminum, 500 to 1,200 old telephone books, 3 to 4 truckloads of “old but still usable” household items for the

Rescue Mission, and 1,000 Christmas trees recycled into mulch and sold to residents.

The average annual profit for the town of 20,000 people was considered to be about

$3,000. Figures for 1975 show a slight loss in the Christmas tree program. One thousand Christmas trees were chipped and placed in 560 bags as mulch, then sold at 254

per bag, resulting in an income of $140. The township saved an estimated $46 in landffi and trucking costs. The chipper was paid $221. The loss of $35, however, was

obviously absorbed in the overa11 gains from the program.

The curbside recycling program has recently been dropped, and with it went the

wood source-separation project. At present, bins are available at two sites for people

to bring in newspapers and glass, separated by color, which are picked up by a private

collector. The Christmas trees are picked up by the municipality and dumped in a semiwooded area.

2. In another municipality of about 45,000 people, located in the most industrial

part of New Jersey, tree cuttings alone are sold. They are offered on Saturday mornings between 8 a.m. and 1 p.m., primarily from November to March, at 1Od per piece,

with only 30 pieces allowed to be taken away per car. This year more was sold than

ever before. The program costs the town more than it makes, primarily for the labor

of three or four men splitting wood. Though the going price of the wood sections is

only one-half that of local commercial prices, not enough is sold here to draw complaints. Still, the temptation to steal is reduced by piling the wood in a fenced-in area

behind a park.

Ahhough this municipality has a strong curbside source-separation program for

used newspaper and glass, the operation for wood is kept separate.

3. Another municipality of about 25,000 people in the same general area has a

slightly more structured price system. Here cordwood is sold by the rick (SS), quartercord ($lO), half-cord ($20) and ful1 cord ($36). Unfortunately, since the wood is

stored openly, most of it is stolen. As a result, splitting is delayed until the selling time

in October . This program is viewed as perhaps more of a liability than an asset because

of the number of serious injuries which occur to municipal employees during splitting,

which is done by a machine.

What supports apparently successful municipal programs in source separation of

waste wood?

1. Putting the program on a public service basis where there is no attempt to

create a money-making operation. Most so-called recycling programs try to appear as

economically self-supporting, even as profit-making. Rises and crashes are frequent

and, as a result, entry into such programs is often considered as political death for

elected officials.

2. Results which reach into another area, especially a nonessential but forwardlooking one. In one municipality, wood chips are not only distributed to parks and

around municipal buildings, as well as to the public, but at least one offrcial considers

them potentially useful in helping condition soil in an area which is being left “natural,”

30
essentially as a municipal wild preserve. This person also sees value in allowing the final

cover on landffls to go wild, establishing wild parks.

What can bring down urban wood programs?

1. Being tied to another program which, while presently very promising in one

place, has a history of fluctuating success elsewhere. While recycling industries in New

Jersey appear to be in excellent health, municipal programs in source separation have

had enough ups and downs to render them uncertain bases, unless perhaps the whole

recycling effort is declared a public service, or even associated with a national necessity

of broad scope.

2. Failure to accomplish the plain mechanics successfully, such as handling machinery, in a way which results in accidents that mar the program.

In conclusion, not only do the requirements of the new solid-waste laws offer a

new lift to source-separation programs, but a new operation being considered by the

Camden County Shade Tree Commission may prove to be a way of increasing markets:

Trees, tree wastes, and wood products now contribute significantly to the problem. During the sixteen-year period between 1955 and 197 1, over 120 million cubic

feet of wood residues from land clearing were destroyed in New Jersey aloneenough lumber mass for the construction of some 37,000 average homes. These

statistics were compiled at a time when open burning was the accepted means of

disposal. With 1973 came the prohibition of this method, resulting in this inordinate amount of usable wood waste becoming a key component in the solid-waste

disposal dilemma.

The implementation of a Waste Wood Recycling Facility in Camden County

shows great promise for helping to alleviate these conditions in the future. Waste

wood heretofore earmarked for disposal can be rechanneled through the facilityeither directly to the proposed Lakeland site, or indirectly through the establishment of four to six transfer stations strategically situated throughout the county.

At the facility itself, the material would be sorted first into a tree’s component

parts; i.e., tops, large branches, leaves, boles, stumps, etc. Next, further separations

as to quality and/or species would be performed (a lumber mill might be interested

in purchasing certain species of oaks for use in veneer production). A metal detector

would ensure against equipment damage due to hidden hardware within the tree.

Lower-quality logs would be cut into uniform lengths, to be split as firewood.

The Shade Tree Commission of Camden County, working in cooperation with

the Camden County Municipal Utilities Authority, the N. J. Bureau of Forestry,

and Cook College, Rutgers University, has found a great potential use for wood

chips produced at the facility in the City of Camden’s Sewage Sludge Composting

Program. Under this program, wood chips are currently being purchased on a contractual basis from a major area land-clearing operation. The chips are combined

with dewatered sludge at a ratio of two parts chips to one part sludge, then stacked

in composting piles and aerated to hasten the decomposition process. The end

product is suitable for use especially as a growth medium for nurseries, and in slope

stabilization. Tbe participants in the program have expressed a great interest in

31
obtaining wood chips for this operation from the proposed Camden County facility.

This program in particular is definitely a progressive step toward wise utilization of

two “waste” sources.

In addition, with procurement of a front-end loader equipped with power takeoff (a necessity to all operational phases) and a single attachment, leaves from

municipal collection rounds can be stacked, aerated, and decomposed into a fine

organic material perfectly suited for farm and garden soil enrichment. This material

could be made available to low- and moderate-income families who grow their own

food.

LITERATURE CITED

Camden County (NJ.) Solid Waste Advisory Council

1978. Preliminary study on solid waste planning.

U.S. Environmental Protection Agency

1977. Fourth report to Congress: Resource recovery and waste reduction.

U.S. Environmental Protection Agency

1978. Resource recovery technology: An implementation seminar workbook.

32
DETERMINATION OF WOOD CONTENT IN

DEMOLITION AND CONSTRUCTION WASTES

James A. Commid

Abstract.-Demolition and construction w&e streams were evaluated

on a national basis by a unique combination of empirical and predictive techniques. National figures developed indicate 55 million total

tons, the waste wood fraction of which is 22 million tons, representing 2 percent of the heating value of all U.S. coal production.

INTRODUCTION

Forty years ago the practice in demolition and construction was to save and se11

the used materials. In fact, many demolition and construction companies hada thriving

business in used lumber. As labor costs increased and powerful wrecking equipment

became available, hand-wrecking (which made possible the utilization of used lumber

in new construction) became economically unfeasible. Today it is practically extinct.

The wood fraction of demolition and construction waste is generally in shattered form,

mixed with other debris, and disposed of at landfills.

Two factors have signaled the need to alter this process. Regulations on solid waste

disposal were tightened, dramatically increasing the trucking distances to acceptable

disposal sites and raising the dump fees because of increased site preparation and operating costs. During the same period, the United States got its first taste of energy shortages and much higher energy costs. These two factors-h@h disposal rates and high

energy costs-are responsible for the interest in waste wood.

Prior to 1975, considerable work had been done in analyzing municipal household

wastes and examining energy options. A fundamental knowledge for any production

operation is the availability, quality (constituents in the case of waste streams), and

cost of feedstocks on which to base production estimates. While such data were generally available in the case of municipal waste, no such comparable condition prevailed

for demolition and construction waste.

In July 1976, EPA% Office of Solid Waste Management awarded to JACA Corporation a contract to determine the energy potential from construction and demolition

waste. This work was completed in February 1977, and the final report issued in April

of that year. 1 was the principal investigator for that work, which is the subject of this

paper. The interest in this work might be not only with the findings, but also in the

methodology applied, since it uses human estimates in an optimal balance between

sampling and measurement error.

Before this study was conducted, there were only sketchy data on the wood

fraction in demolition and construction wood wastes. What little data there were

exhibited large variations, some 700 percent. The goal of the study, therefore, was to

determine the flow and percentage of wood waste with a nominal predicted accuracy

of + 30 percent .

‘President, JACA Corporation, 550 Pmetown Road, Fort Washington, Pennsylvania 19034.

33
Predictive OT empirical techniques might be used in determining the combustible

fraction of demolition and construction waste. Predictive techniques involve determining the composition of buildings presently being demolished on the basis of knowledge of materials and quantities and construction techniques generally employed

during the time of construction. Information concerning the age of structures demolished, as well as the number of razed units of each construction type, is employed in

conjunction with information on number of buildings demolished, average number of

cubic yards of waste generated per building, and the density of the waste per cubic

yard to yield the total number of tons of combustibles available.

There are limitations on predictive and empirical techniques. Those affecting the

predictive technique have been summarized in a repor%.* First, estimates of building

composition at demolition will incorporate errors since alterations, additions, and

replacements take place after the building is constructed. Second, the set of buildings

being demolished is not a homogeneous combination of al1 types and sizes, and the use

of the computed content of the average building may differ significantly from those

being razed. Third, clean fil or waste not containing wood, metals, or plastics may be

short-circuited and never reach the dump site. Fourth, on many jobs, the demolition

contractor leaves any basement or foundation intact, and fills the basement with

nonwood waste from the structure. Any waste so diverted is not truly available but is

part of predictive estimates.

Empirical sampling involves actual analysis of representative waste streams and

inferences made on the total, based on this sampling. It also has some drawbacks.

First, sampling involves the random selection of sites and times of observations; it is

often not possible to achieve this randomness because of time and budget constraints.

To the extent that randomness is lacking, errors may enter into the estimation process.

Second, measurement error is involved in making the empirical fmdings.

In this study we employed a combination of empirical and predictive techniques

to develop estimates of the annual amount of construction and demolition waste and

the fraction of that waste which is wood. Our study found that the United States

annually produces 55 million tons of waste from demolition and construction activities; that waste wood accounts for 22 million tons (40 percent) of this total; that this

waste wood has a heating value of 3.75 X 1014 BTU, or about 2 percent of the energy

derived from coa1 in this country annually. The amount of waste wood and its BTU

potential discarded by various cities is shown in table 1.

An important finding for the design of any waste-process facility that uses wood

waste from demolition and construction activities is the bimodal distribution of the

wood content in the waste arriving at a landfill. A frequency distribution plot for 32

loads was developed during training of field observers (discussed later). The same general type of distribution occurred in field tests at 29 sites in 10 cities. This distribution

has important implications for the design of a recovery facility since it affects staging

area, storage, and separation.

*Wilson, David Gordon. 1976. An investigation of the potential fox resource recovery from

demolition wastes. Mass. Inst. Technol.

34
Table l.-Annual tons and BTU potential of wood waste from construction and demolition wastes

of 10 cities in 1976

City Thousand tons BTU potential

Philadelphia

Los Angeles

Chicago

Houston

Detroit

Miami

St. Louis

Atlanta

Pittsburgh

Minneapolis

Average

Total

-

190 3.3 x 1012

670 11.0 x 1012

400 6.9 x 1012

110 1.9 x 1012

490 8.5 x 1012

67 1.1 x 1012

230 4.0 x 1012

42 .72x 1012

100 1.8 x 1012

67 1.2 x 1012

237 4.0 x 1012

2,366 39.9 x 1012

METHODOLOGY

At the outset of the study, it was intended that the following equation would be

used separately for demolition and construction waste to arrive at the number of tons

of combustible debris generated annually from demolition and construction activities:

Average yd 3 tons

X -X

buildings demolished or constructed

building yd 3 year

(1) (2) (3)

X % combustible by weight

(4)

tons of combustible

=-

year

(1) was determmed from primary data obtained from members of the demolition

and construction industries;

(2) was calculated from the weights of 30 sample truckloads of demolition waste

and 30 sample truckloads of construction waste of known volumes;

(3) was determined by extrapolation from the figure on total number of residential

buildings demolished in the United States, found in U.S. Bureau of Census Report C45,

to obtain an annual figure on all categories of residential, commercial, and industrial

buildings demolished. Extrapolation was based on the ratio of residential buildmgs

constructed or demolished to nonresidential buildings (commercial and industrial)

constructed or demolished. Data were derived from the annual building construction

and demolition permit records of the 10 cities visited. These calculations are based on

35
the number of buildings demolished or constructed after issuance of a permit; they do

not cover unpermitted operations. Unpermitted operations, which occur most often in

rural areas where levels of demolition activity are low, are expected to represent a

negligible part of the total activity.

(4) was obtained from statistical analysis of the data collected at disposal sites

in Philadelphia, Los Angeles, Minneapolis, Houston, St. Louis, Miami, Pittsburgh,

Chicago, Atlanta, and Detroit. A total of 29 disposal sites was visited and 1,001 truck

dumpings observed .

TRAINING

The data-collection methodology for part (4) of the equation used visual estimation to measure percentage of combustibles by weight. Therefore, special training was

instituted. The questions to be answered in the training phase were:

1. What were the best techniques for observing and estimating the volume of construction and demolition waste in a disposal operation?

2. What was the accuracy of the estimation?

3. Was the accuracy improved significantly by averaging the estimates of two or

more observations?

A ó-week-training session was initiated during which these issues were addressed.

It was conducted at a suburban Philadelphia disposal site licensed by the State of

Pennsylvania for demolition and construction waste. After meeting with site personnel,

severa1 areas were designated and cleared so that the training loads could be kept separate for future analysis. Arrangements were made with a local demolition contractor to have his incoming 50-cubic-yard trucks stop at a nearby scale to obtain gross

and tare weight for the vehicle. Trash bins of 12 to 18 cubic yards and a dump truck

were used in the separation of the wood fraction.

When a weighed truck pulled into the landfill area, the observers positioned themselves around the rear of the truck at safe distances and at unobstructed observation

points. The best location proved to be about 30” from the rear centerline of the truck.

Observation of material was made while the load was dumped and after it was on the

ground to make an estimate of the amount of wood and wood products in the load.

Because this was a training exercise, estimates of the first loads were made on a volume

basis until the observers developed a correlation between the volume and weight

percentages.

Estimates of weight, along with date, time, source, truck weights, and general

comments were recorded on a data sheet. Al1 loads were photographed for subsequent

analysis (fig. 1).

Four JACA employees went through the training program. Two had college

degrees, and two were technlcians with severa1 years experience. It was not known

how many loads would be required to develop an acceptable degree of accuracy (20

percent). Progress was monitored and terminated at 32 loads, when accuracy was

satisfactory.

The loads were hand-separated into wood and nonwood piles. Portable trash

dumpsters and a dump truck were used to transport the separated materials back to

36
Figure l.-An unseparated load of demolition waste with a high percentage of wood.

the scale. Because of the size and weight of some of the beams and concrete blocks, a

front-end loader was occasionahy used as an aid in loading the receptacle. Since the

debris was often very small at the bottom of the pile (these smaller pieces were often

ground up when the front-end loader raked the pile), the weight percentages of the

remaining 10 percent or less were often estimated and added to the weigh-ticket

totals. The estimated remainder was less than 200 pounds. All of the debris carne

from the Philadelphia area; information about the type of structure from which it

originated was obtained from the drivers or dispatcher.

The actual percentage of combustibles was obtained in the following manner:

Percent combustibles

gross weight of separated materials

=

H

weight of container

gross weight of incoming truck weight of truck x 100

Thirty-two loads of demolition waste were hand-separated and weighed during

the training period. It was noted that demolition loads tend to occur most frequently

with high-percentage combustibles or low-percentage combustibles rather than in the

middle range. This same condition prevailed in 1,001 observations in later fieldwork.

The sampling process is subject to two types of errors. The measurement or

nonsampling error occurs because of a difference between the actual value and the

measured value; this kind of error arises from factors such as imperfect observation,

faulty questionnaires, or inaccurate tallying. The sampling error results from the chance

selection of sampling units; this error occurs when a partial observation of the universe

37
takes place. If the entire universe were studied, the sampling error would be zero.

The total error in a statistical survey such as this one is the sum of the measurement error and the sampling error. The major concern is to minimize the total error.

Reduction of the measurement error is achieved by defining precisely the population

to be studied and its traits, by refining the measurement process to the highest degree,

and by training the individuals doing the measurement as thoroughly as practicable.

These precautionary measures are usually costly, leading to the necessity of using small

samples. However, small samples tend to have larger sampling errors. Therefore, there

are two options available: the sample size can be kept small and the measurement

made in a sophisticated manner, or the sample size can be large and the measurement

made in an unsophisticated manner. The following example should help illustrate the

method of estimating the percentage of combustibles in construction and demolition

waste. Assume that a sophisticated measurement process would limit the sample size

to 50 observations; an unsophisticated technique would employ trained observers to

estimate the combustible proportion and would allow for a sample size of 300 observations. Assume that the measurement error in the fiist case would be 5 percent and in

the second case 10 percent. In estimating proportions, the formula for the maximum

sampling error is given by :

6 = sampling

z = normal curve deviate, which is determined by the leve1 of confidence

rr = universe proportion being estimated

In the absence of information concerning the possible size of rr, it is assigned a

value of ‘%, which maximizes the expression rr(l - rr), and, therefore, maximizes 6 for a

given leve1 of confidente and sample size. In the cases cited above, if a leve1 of con%

dente of 90 percent is employed :

(2) 690 = 1.645/.s)(15; .5)= .116

6 1 . 645p) (1 =

- 3

90 = .047

300

Using a leve1 of confidente of 95 percent:

(3) Sgg = 1.96~(‘5)50“5) = .139

6 95 = l.96#5)$;; ‘5) = .056

38
Since :

Total error = Sampling + Measurement error, the following results are obtained with

a 90 percent confidente:

Case 1 Total error = .166 + .05 = .165

Case 2 Total error = .047 + .lO = .147

with 95 percent confidence:

Case 1 Total error = .139 + .OS = .189

Case 2 Total error = .OS6 + .lO = .156

At both levels of confidente, the total error is smaller when the sample size is

increased at the expense of a larger measurement error. In the case of this study, we

chose the option of increasing the sample size as opposed to reducing the measurement

error, and the cost of doing so was significantly less than reducing the measurement

error.

STRATIFYING THE SAMPLE

In stratified random sampling, the universe is classilied into mutually exclusive

subgroups or “strata” and samples are drawn from each of them. Sample statistics are

calculated from each of these strata and are combined to yield an overall estimate of a

population parameter. Tl-re basic purposes of stratified sampling, as compared to simple

random sampling, are to obtain a sample that closely resembles the universe from

which it was drawn and to reduce sampling errors. These objectives are accomplished

by grouping together into strata those elements which are more alike with respect to

the characteristic under investigation than are elements in the universe as a whole.

Stratification is most effective when the elements within strata are as homogeneous

as possible, as regards the property to be studied, and the differences among strata are

as great as possible.

In this study, the demolition samples were to be stratified by type of structure.

Initially, four strata were contemplated: residential, multi-unit residential, commercial,

and industrial buildings. Experience in the field led to a reduction in the number of

strata to two: residential and other: This reduction was made because many cities did

not distinguish among the various types of structures, or because the required number

of observations to define strata was not generated in each of the four areas. The same

strata were initially proposed for the construction data. The number here was also

reduced to two for the same reasons. The stratitication by phase of construction was

also considered but was abandoned after attempts to gather the data proved highly

impractical within budget and time limitations.

In determining the geographical sites, the United States was divided into four areas

and a percentage of the total population calculated for each area. This technique

resulted in a selection of cities that would represent any regional peculiarities of

building material and techniques. Ten cities were selected on this area breakdown on

the basis of construction and demolition activity. Within each of these 10 cities,

disposal sites were chosen on the basis of activity at the site and the willingness of the

operator to cooperate by allowing field technicians to make observations.

39
Once the cities had been selected, the desired number of observations in each

stratum (residential and other) for construction and demolition was determined by

averaging the number of construction and demolition permits issued in each city

during the period 1970-75. These permits were used to establish the ratio of residential to other units constructed or demolished. This ratio was then applied to the

number 30, the desired number of observations for each City, to determine the desired

number of observations in each of the two strata for that City.

Teams of two technicians each were sent to disposal sites in each of the 10 cities.

Each technician independently observed loads as they were dumped, and the individual readings were averaged to obtain a better estimate of the percentage of combustibles. Varying lengths of time were spent in an effort to gather enough data to meet

the desired stratification, which was universally met.

Since the observed samples exceeded the required number at each location, a

weighting technique was devised to allow the use of al1 the data generated, even where

the actual number observed exceeded the desired number. Weights were assigned in

such a way as to keep the strata in the proper desired ratio. The weighted technique

calculated the percentage combustible for each city as the weighted mean of the two

strata, employing the desired number of observations in each stratum as weights.

To determine the overa11 percentage combustibles, the arithmetic mean and

standard deviation of the 10 weighted percent combustibles were calculated. Employing this datum, a confidente interval for the overall percentage of combustibles was

calculated as follows:

Xp-t e5 (s/n)i92GXp+t.0s (sin)

M P

where :

Xp = mean of the 10 weighted percent combustibles

S = standard deviation of the 10 weighted percent combustibles

t.05 = coefficient , which is determined by the leve1 of confidente

n = sample size (10)

Mp = mean percent combustible for the universe.

For demolition s = 12.12

< Mp < 38.60 + 2.262

29.92 < Mp < 47.28

For construction s=8.34

< Mp < 47.59 + 2.262

41.62 á Mp < 53.56

40
This interpretation of the confidence interval is as follows: there is 9.5 percent

certainty that the mean percentage combustible of all demolition waste is between

29.92 and 47.28 percent. The calculation of the percentage combustible of construction waste and the interpretation of the resulting confidence interval is analogous to

that for demolition. Once the mean percentage combustible was determined, the total

number of tons of combustibles was calculated by employing this percentage in conjunction with data developed on the basis of predictive techniques. The calculation for

demolition waste is:

TCD=A.D.B.P

where :

TCD = total number of tons of combustibles per year from demolition waste

A = average number of cubic yards of waste per building

D = average density of demolition waste

B = number of buildings demolished per year

P = percent combustible of demolition waste

The average number of cubic yards per building was determined from a National

Association of Demolition Contractors (NADC) cooperative questionnaire. The average

density was determined in field experiments with JACA technicians. The number of

buildings demolished per year was determined from literature searches.

In the case of construction waste, it was impossible to develop data from haulers

as to the average volume of loads from typical waste sites, as was done via tlíe questionnaire for demolition waste. These data were not available because of the long duration of construction activity.

The calculation for construction waste differs significantly from that for demolition waste :

TCC=P,W

where :

TCC = total number of tons of combustibles per year from construction

waste

P = percent of wood that is wasted in construction

w = total amount of wood consumed in building and construction

The percentage of wood that is wasted in construction was determined from

information gathered through literature searches and discussions with building contractors based on their estimating procedures. The total amount of wood consumed is

taken from existing government sources.

The primary segment of this study utilized field measurements of properly stratified samples. The plan was to use a total of at least 600 random samples from three

sites at each of the 10 cities visited. In the final analysis, 1,001 samples were obtained.

This sample size was large enough to account fully for geographical differences in

41
building sites and to allow for different sizes and types of buildings. Trained observers

were used to estimate the percentage of combustibles as the trucks dumped their loads.

A satisfactory measurement accuracy by this means would be 20 percent for all sample

totals. The training showed that even higher accuracy was obtained. The objective in

each city studied was to collect enough samples (percentage combustible values) for

demolition and construction waste to meet the previously determined requirements in

each category of a 60-sample stratified set.

The first data collection was done in the Philadelphia area. The Ammal Building

Construction Reports for the years 1970-75 were obtained to determine the stratification, in preparation for actual fieldwork. Construction and demolition permits for

the past 5 months were examined to determine the recent activity levels in each

stratum. The contractors whose names appeared frequently on these permits were

contacted to determine which Philadelphia area landfil sites they were using and

arrangements were made with landfil operators to station field observers at five

local sites.

The activity in demolition and construction was extremely low during the initial

data-collection phase when compared to the activity levels during the earlier training

session. This difference indicated that the generation of demolition and construction

waste was sporadic. As a result, the fieldwork was rescheduled to coincide with periods

of high demolition and construction activity in order to get the most samples during

field visitations.

It was evident that a refmement in the scheduling of cities was extremely important. Following discussions of our objectives with the NADC, Mr. Ron Dokell, President, offered the Association’s assistance and, together with the Energy and Recycling

Committee, provided assistance on our visits to the 10 cities. The NADC committee

supplied names of local members who aided in scheduling Iieldwork to coincide with

high demolition activity. These contacts were also helpful in directing us to the landfills where most of the waste was being hauled.

Arrangements were made to visit three landfills at each of the 10 cities. Because

one of the determining factors as to where demolition and construction debris will be

dumped is the cost of hauling based on distarme, the observation of three local sites

helped neutralize intra-city peculiarities in activity or in composition of waste.

The method of obtaining percentage combustible data followed the procedure

described in the training section. At safe observation points, each load of construction

and demolition debris was amdyzed while being dumped and while on the ground to

estimate the percentage combustible by weight. The driver of the vehicle was questioned briefly as to what building category provided the waste.

Depending on activity levels in each City, observers spent 1 or 2 weeks on site, and

in some instances had to return to a City to satisfy the stratification requirements. The

stratification for the city was referred to periodically during the week to determine

whether sufficient residential, commercial, and industrial loads were being sampled.

Photographs were taken at severa1 dumping sites for future referente.

Construction activity evidenced at the 10 cities was mainly in the form of small

truckloads and portable bins of wastes generated in renovation, roofmg, and siding l

42
projects. Very little waste was observed from new building construction. One expla-’

nation for this phenomenon is that waste generated on construction projects is disposed of on the site to avoid paying dumping fees at a landfill. Therefore, it was necessary to schedule return visits to obtain fully stratified, 60-sample sets of construction

samples.

Some of the city building reports did not distinguish between commercial and’

industrial demolitions. Therefore, these two categories were combined into “nonresidential” construction and demolition for all the cities surveyed. Decreasing the number of strata did alleviate some of the problems in obtaining a proper sample. After the

data on the 10 cities were reviewed, it was necessary to return to Miami, St. Louis, and

Chicago for sufficient data on construction. Sufficient demolition data were collected

in al1 10 cities on the first visit because the demolition volume to building volume ratio

is so large that continua1 landfill dumping is necessary.

Individual observers’ estimates were averaged at each of the 10 cities, and the

difference between one observer’s average for the entire sample and the average of two

observers for the entire sample was negligible. Therefore, one observer was sent to each

of the three cities where insufficient data had been collected on the first visit.

The field data results collected on percentage of combustibles in the 10 cities are

tabulated in table 2.

The density of the loads was a second piece of primary data to be obtained in the

field. During the initial training session, 32 loads of demolition waste were weighed

and separated at a local landfill site. A value for the average density of demolition

waste was needed. The concentration of the various components of demolition waste

(such as wood, brick, concrete, and dirt) and the permitted road weight of a particular

truckload help determine the density of the load and the volume to which the truck

Table 2.-Weighted percentage of wood in demolition and construction waste I

-Field DataCity Wood demolition Wood construction

Philadelphia

Los Angeles

Chicago

Detroit

Houston

St. Louis

Miami

Pittsburgh

Atlanta

Minneapolis

Average weighted

percent combustible

. . . . . . . . Percen t . . . . . . .

41 42

63 48

44 60

42 43

27 63

51 50

37 43

27 36

20 40

34 51

39 48

43
can be filled. Often a 50-cubic-yard-capacity demolition truck with high density components may be filled to only 20 cubic yards; a truck with a high percentage of wood

is generally filled to volume capacity. The average volume of 32 truckloads averaged

40 cubic yards.

When the average densities for the 32 truckloads were calculated, the value for the

density of demolition waste was found to be 25 pounds per cubic foot. This figure was

considered accurate for this study because the percentage combustible values for the

32 training loads had good distributive representation from both low-percentage and

high-percentage combustible loads.

In order to use the equation presented in the National and Area Estimates section,

a value for the average number of cubic yards of waste generated per type of building

demolished or constructed was needed:

Average yd 3 tons bldgs. (const ./demo.) % combustible

X - x

(const./demo.) yd 3

X by weight

year

tons of combustible

=

year

To determine the volume of waste generated in the demolition of buildings, the

NADC cooperated with JACA Corporation in administering a response-card program,

which supplied data collected by 17 volunteer members of NADC.

Respondents remained anonymous through a respondent numbering system, and

the geographical distribution was statistically sound. One card was completed for each

demolition job. The information entered on the card included duration of job, type of

building, number of units if residential, number of loads, and the truck size.

The NADC response-card program ran for approximately 3 months, yielding 200

responses from the 17 respondents. Following completion, cards were separated

according to building category, and the average volume of waste per demolished

building was calculated for residential, commercial, and industrial buildings.

Residential

Commercial

Industrial

Overa11

Average volume of waste per building

450 yd3 /bldg.

2,022 yd3 /bldg.

3,860 yd3 /bldg.

1,370 yd3 /bldg.

From other information included on the response cards, the average duration of

a demolition job could also be determined.

4 4
Average duration of demolition job

(dw)

Residential 3.87

Commercial 9.56

Industrial 14.7

Overall 6.92

Lengthy job duration, variation in methods of disposal of construction waste, and

the inability of members of the hauling industry to provide average estimates of volume of waste generated by each construction job frustrated attempts to determine the

volume of wood waste generated in the construction of a residential building, a commercial building, and an industrial building. Therefore, it became necessary to develop

data on the basis of estimates made by construction contractors on the percentage of

wood waste generated on their jobs. Contractors were requested to estimate the wood

waste as a percentage of wood ordered for each construction job. The results of this

survey of 20 contractors indicated that an average of 7.4 percent of wood delivered is

wasted in the process of construction. The average was tested for significance by the

following equation: Xw-to.5 - á/1W&iwtty5 1A )

-

( Jn 1

At a 95 percent leve1 of confidence, 5.28 < pw < 9.52.

TOTAL ANNUAL ESTIMATES

Annually, the U.S. Department of Commerce, Bureau of the Census, issues a

report entitled “Housing Units Authorized for Demolition in Permit-Issuing Place.”

The report gives the total number of permits issued for demolition annually.

Using the figures presented for the number of housing units demolished in cities

over 50,000 population (0.34 of total U.S. population, 1970 Census) as well as the

cities’ populations, a statistical evaluation was conducted to determine whether a

linear relation existed between population and number of units demolished, using

methods of linear regression analysis. The equation y = -3.05 + 0.0018x was derived

where y = number of units demolished and x = size of population. This equation explained 61 percent of the variation for this relation. Therefore, there would be a certain degree of error in pursuing the calculation of a total for demolition of housing

units by this method.

While the above equation might be useful in predicting the amount of demolition

for an area, a more reliable estimate was needed. Therefore, it was decided that the

figures for U.S. total number of housing units demolished based on reports from

permit-issuing places authorizing the demolition of one or more housing units would

be used. The Bureau of the Census states that these annual figures are based on reports

from areas which represent about 80 to 85 percent of the population and would therefore imply that these figures probably represent 95 percent of the total U.S. housingunit-demolition rate.

45
To convert from units demolished per year to residential btCldings demolished per

year, the average number of units per building demolished from the building reports of

the 10 cities was calculated. This was found to be 1.4 units per building. To determine

the total residential and nonresidential buildings demolished per year, the ratio of residential to nonresidential buildings demolished per year in the 10 cities surveyed was

computed and averaged from their respective building construction and demolition

reports. The following equation was used:

No. of residential buildings demolished X 1

year .803

No. of residential and nonresidential buildings demolished

=

year

1

87,123 X -= 108,497

.803

To determine the total number of buildings constructed per year in the United

States, a similar approach was used. Using data on residential construction obtained

from the National Association of Homebuilders, the following procedure was used:

Residential units constructed + average units

year bldg. constructed

residential bldgs. constructed

=

year

1,512,900

1

+ 2.5 = 605,160

Residential buildings constructed 1

year x.724

residential and nonresidential buildings constructed

=

year

1

605,160 x ~ = 835,856

.724

46
ESTIMATING ENERGY POTENTIAL

The heating value of wood was taken as 8,613 BTU’s per Pound. By multiplying the tons of combustibles generated annually from these two sources, the energy

potential of the waste wood can be calculated on a national level:

Demolition:

avg. yd 3 102 bldgs. demo. BTU’s

bldg. ’ yd3 ’ year

X % combustible X tan

total BTU’s

=

year

1,369.8 X ,337 X 108,500 X .386 X (1.72 X 107)

3.3 X 1014 BTU’s

=

year

Construction:

Tons of wood consumed annually by construction industry

BTU’s

X average % wasted per job in construction X -

ton

Total BTU’s

= ___-

year

35,000,OOO X .074 X (1.72 X 107)

4.5 X 1013 BTU’s

z

year

Total energy potential from demolition and construction nationwide

3.75 X 1014 BTU’s

=

year

To determine the energy potential from demolition waste for a given local area,

the above equation is used with a substitution of number of buildings demolished per

year within the city for the number of buildings demolished on the national level. The

local weighted percent combustible figure can be substituted for the national average

of 39 percent. The volume per building must be recalculated in accordance with the

average ratio of residential, commercial, and industrial buildings indicated in the

building reports.

47
To calculate the energy potential available from construction waste on a local

level, the amount of wood consumed must be estimated. The method used was to set

up an equality which relates amount of wood consumed by the construction industry

on a given leve1 to the number of buildings constructed on that level.

Wood consumption nationwide, by construction industry

buildings constructed nationwide

Wood consumption, by City, by construction’industry

=

buildings constructed, by city

e.g., Chicago

3.5,000,000 tons x

=-

835,856 bldgs. 2,482

X = wood consumption = 104,000 tons per year, by Chicago construction

industry

Using the construction waste energy potential equation:

104,400 X .074 X (1.72 X 10’) =

1 3

’ X lo1 r BTU’s

year

These equations may be applied to any locality that has the appropriate data

available.

48
TOPE IlI

UTILIZATION OPTIONS

49
TOPIC II

UTILIZATION OPTIONS

ABSTRACTS

DeVOTO

Paper from Municipal Trees.-Because they encountered increasing numbers of trees killed

by Dutch elm disease, the cities of Minneapolis and St. Paul attempted to fmd a method for

wood disposal other than burning and/or burying in landflls. A large-size chipper seemed to

be the solution to the problem.

WALKER

Mulch from Limb and Trunk Debris.-Faced with the rising cost of pine straw, Georgialnstitute of Technology experlmented with using site-generated wood chips for mulch. It was

learned that, compared with pine straw, wood chips were less expensive, longer lasting, less

tlammable, and better at retaining soil moisture.

LEMPICKI

Products from Municipal Trees.-Shade trees along City streets and state highways and those

near suburban homes often reach a large size and have butt logs suitable for many specialty

products. However, when these trees are felled, they are all too often used only for fuelwood

and wood chips, or hauled to landfiis. The following is an example of one company’s expe

riente in turning this underutilized material into an interesting and profitable commodity.

LOWERY

Firewood from Municipal Trees.-Firewood is becoming a necessary item in the life of

Americans as we face increasing energy shortages. This paper summarizes an effort to supply the citizens of Atlanta with an energy source obtained from wood residues produced

from the city’s forestry operation.

COBB

Fuel Preparation for Waste Wood Boilers.-After proper preparation, wood residue may be

used as fuel or as raw material for such products as horticultural mulch, animal bedding,

poultry litter, particleboard, fireplace logs, and fuel pellets. The reuse of waste wood requires

an understanding of waste wood boilers, wood-reduction machines (hogs), waste loads,

economic considerations, and the services provided by consultants.

HOWARD

Marketing Urban Wood Residues.-This study defines the characteristics of wood residues

that affect their marketability, discusses the processing required to upgrade residues to useful

wood fiber, and lists potential markets and dollar values for various residues.

STUROS

Segregation Processes for Urban Waste Wood.-Three technologies-steamingng-compression

debarking, vacuum-airlift segregation, and photosorting-have been developed for improving

the quality of whole-tree and wood-residue chips. Applications of these processes coupled

with integrated utilization of the various output wood fractions should lower the barriers

for increased urban waste wood utilization.

McMINN

Importance of Wood as an Urban Energy Source.-The paper reviews (1) theoretical limits

to wood supplies, (2) characteristics of wood as a fuel source, (3) difficulties inpredicting

energy consumption and fuel prices, and (4) the outlook for wood-energy development.

Woody biomass is likely to provide less than 10 percent of urban energy, and its use will be

in small-scale, decentralized systems. Small towns will derive the greatest beneflts from

primary biomass, whereas use of urban waste wood will probably be unrelated to City sise.

50
MILLS

Recovery of Energy from Solid Waste-An Alternative to Landfill Disposal.-There axe many

solid waste recovery techniques from which communities may choose. The technology

described here is known generally as mass combustion in waterwall boilers. A facility using

this technology takes all kinds of residential, commercial, and nonproblem industrial solid

wastes and processes them into usable energy and marketable materials. This combustion

process performs extremely well, with better than 96 percent burnout of combustible matter and a volume reduction of 95 percent.

5 1
PAPER FROM MUNICIPAL TREES

David F. Devoto’

Abstract.-Because they encountered increasing numbers of trees

killed by Dutch elm disease, the cities of Minneapolis and St. Paul

attempted to find a method for wood disposal other than burning

and/or burying in landfills. A large-size chipper seemed to be the

solution to the problem.

THE NEED

A fungus (Ceratocystis ulmi) implanted in elm trees by bark beetles causes a

condition called Dutch elm disease. This disease has become extremely serious in the

cities of Minneapolis and St. Paul over the last few years. Beginning in 1961 in St. Paul

and 1963 in Minneapolis, the disease plodded along without causing real problems

until about 1975, when the number of infected trees began to soar, as is shown in

figure 1.

I I

9

- MINNEAP. LOSSES

8

- - -- ST. PAUL LOSSES

- -

2

- MINNEAP. BUDGET

p 7 . . . .

. * ST.PAUL BUDGET

--

-20

- 15

- 10

- 5

-.-Cl -iC-

”

”

1972 1973 1974 1975 1976 1977 1978

YEAR

--

-25

Figure 1 .-Budgets and tree losses for Minneapolis and St. Paul.

‘Director of Forestry, Minneapolis Park and Recreation Board, 250 South Fourth Street,

Minneapolis, Minnesota 55415.

52
In the early seventies, realizing that iosses were going to become high and that

dollars for control were going to be limited, the cities (first independently, and then

after realizing they were following parallel paths, jointly) began trying to find means

of disposing of trees more efficiently. Until this point, trees were either burned or

buried in commercial landfills. These methods were, even with low losses, not the best

means for disposal. As losses increased, they became even less acceptable.

In any large metropolitan area, landfill space is scarce and should be reserved for

household and industrial wastes rather than being quickly used up by tree brush and

logs. When we discussed the possibility of bringing the large anticipated volumes to his

site, one landfill operator said that he would only take our debris if we supplied a ton

of covering sand for every ton of material we dumped; this obviously would become

expensive .

The other means of disposal available was open burning. With air pollution standards becoming more stringent, with increasing amounts of pollutants being generated

within cities, and with urban sprawl pushing suitable sites farther away, burning fell

short of being a good alternative.

In both of the above methods, another problem became clear. Large increases in

volumes meant more equipment would be necessary, causing more capital investment.

Money for this had to be borrowed at increasing interest rates. More labor had to be

hired at even higher salary rates. The dilemma became worse.

Table 1 .-Comparative disposal costs/ton

Year 1976 1977 1978

Landfill

Burning site

. . . . . . . . . . . . . Dollars. . . . . . . . . . . . .

4.25 6.00 7.20

N/A 2.00 3.00

ALTERNATIVES

Tl-re most obvious alternative for a forester was to turn these costly-to-dispose-of

logs into usable wood, which made sense because the wood was still sound. Its quality

and structure were unchanged, and many of the logs were long and clear of limbs and

knots. With the number of logs steadily increasing, it might even be feasible to move a

sawmill into the area.

Not so, according to the sawmill operators. In our efficient methods for preservation of city trees we had created a major stumbling block. Whenever a tree began to

develop decay, someone had been there to chip away the decay and plug the hole with

concrete and reinforcement rod. Whenever a severe storm split and damaged a tree, we

were “Johnny-on-the-spot” to screw in lag hooks, attach chains and cables, and fasten

in large bolt-rods. We even went so far as to trace the bark around these fixtures so

that the tree would neatly grow over them, making them almost invisible. An additional problem was that every housewife who planned a Saturday garage sale advertised it by nailing a sign (using a tenpenny nail) to our trees.

53
We had anticipated some problems with foreign objects in trees, but we did not

realize just how serious these problems would be. It would have been nice to do away

with the disposal problem and its inherent costs and perhaps even get a little return by

selling our logs to sawmills. The sawmill operators quickly and firmly let us know that

they were not interested in our trees, even if we gave them away.

Another possibility was to not saw up the material, but to grind it into wood chips.

There seemed to be many uses for chips. We had, in the past, been chipping small

branches (up to 6 inches in diameter) right on the Street with small trailer-mounted

limb chippers. Much of this material was used as mulch around our newly planted

trees and shrubs. Any material not needed for our own use was easily given away to

homeowners for their use. Hardwood chips of the proper quality and size were being

used by local manufacturers of roofing felt. Although paper companies were at first

somewhat reluctant to use hardwood chips for pulp, we felt a market could be developed and, if debarked and properly processed, many of our logs could be disposed of

in that industry.

Further study indicated that chipper plants were relatively inexpensive, costing

$% million to $% million (compared to the cost of setting up a sawmill: more than

$1.5 million). The amount of space necessary was also less, and the amount of waste

would be extremely small if a wood “hog” were incorporated into the system to

regrind bark and “overs-and-unders” into fuel material.

Since we did not want to go into the chipping business, our next task was to find

someone in the private sector who would be willing to invest in building and operating

such a system. Again we ran into problems. The private investors needed many guarantees to protect their investments. Could we guarantee a certain number of tons of chips

delivered in relatively even amounts and for a specified number of years? If we could

not fulilll the quota, who would be responsible for the difference in the expected

profit? This was al1 taking place in 1973-74 and, of course, hindsight now shows

us that certain of these guarantees could have been met. At the time, however, acting

as a public agency dealing with the citizens’ tax dollars, we could not make such

commitments.

We were then at the spot that the “little red hen” (in the children’s story) found

herself. When she could not get any help she said, “Then 1’11 do it myself,” and she did.

Well, we did too but not quite so easily; we built a chipper plant ourselves. Since we

were not in the chipping industry and therefore knew very little about it, we searched

a lot of printed matter, talked to a great many individuals and flnally (with considerable help from a consulting engineer) carne up with what seemed to be a workable plan.

SITE SELECTION

It was determined that we would need about 10 acres of land for erecting the

plant and to use for storage and handling of the material. Although vacant lo-acre sites

are not very common in a metropolitan area, there were five locations that were feasible. Best of all, they were owned by various government agencies and could be used

without the need to buy land. As usual, things did not go quite the way we would have

liked .

54
Site number one (fig. 2) was the most convenient for both cities and was our first

choice. It tumed out, however, that the agency owning it had it set up as an industrial development site. The owners needed a long-term lease and expected us to pay

them for the revenue they would lose while it remained undeveloped. Since our whole

venture needed to be done with a very tight budget, the costs incurred would have

been entirely too high.

0

0

5+

l-4

LANDFILLS

OPEN BURNING

CHIPPER PLANT

PROPOSED PLANT SITES

Figure 2.-Actual and proposed disposal sites in Minneapolis-St. Paul.

Site number two (fig. 2) was next best, but we found that it would be directly

under the flight path of the airport. Dust from trucking and from the machinery

would create a hazard for landing aircraft. The metropolitan airport commission felt

strongly that this would be an unsuitable location unless we would be willing to shut

the plant down during problem times. Since this would not be feasible, the next site

was considered.

This location (number three in fig. 2) appeared to be a good choice, even though

it meant a little farther hauling distance for St. Paul. It was located on property owned

by the City Water Department. No other use was foreseen for it, and it also had railroad access, which meant that if rail transportation of chips turned out to be our best

method, it would be inexpensive to put in a loading spur. Again, problems!

Use of the property required City Council approval. Just prior to our request, a

special-use permit had been given to a barge company to insta11 a loading terminal on

the river just across from our proposed site. The Alderman for that ward had been

receiving many complaints about loud noises due to barges being banged into each

other night and day. He absolutely refused to allow anything to be done in that area

that might possibly make any noise.

Location number four (fig. 2) was convenient to both cities. It had enough space

55
and could receive Council approvat. tn closely examining the area, however, it was

clear that interjecting many large trucks ful1 of logs into an area of heavy traffic congestion would become frustrating to al1 concerned.

Another area (number five in fig. 2) was finally selected to be used for the plant.

This area had certain drawbacks which caused it to be the last to be considered. Of

primary concern was that it is within the “100 year” flood plain. Even though the

odds of flood were very small, machinery that would be affected by water would have

to be made so it could be easily removed to high ground. The site was originally a

sanitary landfill, and soil borings from as deep as 60 feet were showing undecomposed

garbage, which meant that pilings would be required under equipment pads. Access to

the site was also somewhat constrained, and we realized that during spring thaw and

heavy rains, we would be severely hampered by mud.

On the other hand, the site was on St. Paul Port Authority land, which we could

use at no cost. It was remote from other land use except for a railroad-repair facility, a

cement plant, and a sewage-treatment facility. For this‘ reason, there would be no

neighbor problems. If necessary, we could rather inexpensively put in a railroad spur

for shipping and possibly even set up for loading river barges.

PLANT COtiPONENTS

While site selection was going on, we were also determining what components

were necessary for operation. It was decided that the best power to use was electric

motors. Components (fig. 3) were as follows:

1. Nicholson 55 by 5%inch roto-drum chipper (fig. 4).

2. Precision No. P848M debarker, complete with control panel and motor starter

(fig. 5).

LOGS

CP- 6

Figure 3.-Components of the chipping plant.

56
Figure 4.-Cutoff saw iu operation.

Figure 5.-Log being loaded onto debarker.

57
3. LM Model No. 200 HSA chain-saw cutoff, complete with control panel and

motor starter (fig. 6).

4. S- by 8-foot chip screen manufactured by Precision.

5. Two van truck loaders with feeder manufactured by Phelps.

6. Bark and waste hog manufactured by Bush Manufacturing Company.

7. Large-capacity storage bin manufactured by Carothers Brothers.

8. Miscellaneous log decks with stops, conveyors, log jack, log clam, etc., manufactured by Mellott .

9. Miscellaneous conveyors, transporters, supports, and walkways manufactured by

Minneapolis Sheet Metal Works.

Figure ó.-Debarked log entering chipper.

The total cost for construction, $460,000, was shared by the Minneapolis Park

and Recreation Board ($ ll 5,000 or 25 percent), the City of St. Paul ($115,000 or

25 percent) and the State of Minnesota, Department of Agriculture ($230,000 or a

50 percent matching grant). The program was set up under a joint-powers agreement

between Minneapolis and St. Paul, with the latter being designated as the lead agency.

Bids to furnish the equipment, prepare the land, and install all components were

requested, and an award was made to the lowest bidder, Minneapolis Sheet Metal Co.

Construction was begun during January 1977, and the plant was ready for a trial

run during August 1977. After the usual equipment shakedown problems, the plant

was ready for operation.

A decision had previously been made that actual operation of the faciiity would

be best handled by the hiring of a private operator chosen by the open-bid method.

58
The Northland Pulp Company was chosen as the operator. Production began, and

things seemed to be going well. Chips and hog fuel were being produced and marketed.

19772DISASTER!

The 1977 season opened with a bang. Suddenly trees were wilting in both cities in

unbelievable numbers. In Minneapolis we had lined up 19 private contractors and felt

very comfortable. It turned out that they were not sufficient; even bringing in an additional 13 through an emergency bid did not give us enough. Fortunately , when we had

asked for bids we requested two price quotations, one for free dumping at the chipper

plant and a second price if the contractor had to find his own disposal area and pay his

own dumping fee.

To help alleviate overload problems at the plant, al1 contractors working in Minneapolis were required to find their own dumping areas. The Hennepin County Public

Works Department set up a burning site open to these contractors, and the bulk of the

trees removed from Minneapolis and surrounding areas literally “went up in smoke.”

Our own city crews were aided in disposing of all material up to 22 inches in diameter

by our renting four 22-inch Morbark chippers, which chipped trees right at the removal

location on the Street. This left for the large chipper only logs over. inches in diameter, which were cut properly for running directly through the chipper plant.

Unfortunately, things did not go as well for St. Paul. The contractors in St. Paul,

as well as the city crews, had to haul al1 of the logs, brush, and other debris to the

chipper plant. The removal of some 40,000 trees over a 4-month period caused brush

and log piles to rise like mountains. It was estimated that by the end of summer some

30,000 trees were piled on the site.

The plant, of course, could not handle these volumes. Trucks found themselves

having to wait up to 3 hours just to get through the gates. Then, because of mud, most

of them had to be pulled into and out of the dumping areas by tractors. St. Paul hired

cranes to unload trucks, and debris was piled 20 to 25 feet high. Attempts to pu11 logs

out of the piles were extremely difficult because of al1 the entangled brushy material.

The chipper itself was running at full capacity for 1% shifts per day, and the other

3/2 shift was spent trying to keep it in repair. A lot of logs were being processed, but the

volumes of brush (for which the plant had not been intended) were becoming huge.

St. Paul then located and purchased two large log-chippers, one a Morbark and the

other a Nicholson. They helped on the brush, but by the end of fall, tremendous volume still remained. The standard joke of the day was, “Anybody got a match?”

Actual burning was considered. The air-pollution problem that would occur, however, would not allow for it. Since the ground upon which the trees were lying was an

old landfnl with undecomposed material many feet deep, it was feared that if this

material were to catch fire it might not be easily extinguished. There was also the fear

that methane pockets might exist in sizes sufficient to cause serious explosions.

By midwinter some progress had been made in reducing the volume, but it was

still a substantial problem. Speculation then began about how much of a threat this

pile of beetle-infested wood would become to elms in the surrounding area. There were

two schools of thought. One held that the beetles would go no farther than a nearby

59
river bottom ful1 of elms for them to feed upon. The second held that the winds associated with wide river valleys would blow them out into the neighboring areas and

cause serious tree losses.

We never found out who was right. It seems a welder making repairs on a piece of

machinery allowed sparks to ignite oil-soaked rags, which then ignited a gasoline

storage can in an old shack. The shack, in turn, caught fire, culminating in the acres of

wood catching tire. They burned out of control for 10 days. The fire department could

do little more than keep the chipper plant from burning up. The firemen were hampered by low pressure in the scarcely available tire hydrants.

The fire was fmally brought under control, and the remainder of the debris was

allowed to continue to burn for an additional20 days under controlled conditions.

1978-OPERATING!

The 1978 season was much better. The only brush allowed to be brought into the

area was carefully kept separated from the logs, and only what could be disposed of

in 1 day was allowed on site. Stockpiles of logs were held to reasonable sizes and separated by fne lanes. The season ran quite well, and by the end of the year most material

had been processed.

During the summer of 1978 the plan produced for sale some $350,000 Worth of

chips. Prices received for the chips varied with their type, quality, and intended use.

Total-tree chips (those not screened and with higher bark content) sold for $5 to $6 .

per ton. The price varied, with debarked and screened chips selling for $9 per ton.

There were many companies buying chips; e.g., Horner Waldorf Paper Company

(located right in St. Paul), Certain-Teed Corporation (producers of building materials

and also located in the suburban area), Celotex Corporation (in Iowa and Illinois),

and both Owens-Illinois and Weyerhaueser Corporations in Wisconsin. A great many

chips were sold for landscaping and agricultura] purposes. Driving into the metropolitan area, one sees tons of chips used as mulch in shrub plantings along highways.

It appears that some marketing problems will always occur. Value of chips varies

with the type and quality being produced. Most buyers need to have certain guarantees

with regard to volume, steady and even production flow, and long-term commitments.

Since our production depends on factors beyond our control (rate of disease incidence,

weather effects on the disease vector, possibilities of improved disease-control methods

or even cures), commitments of these types cannot be made. The primary problem is

that we are not trying to produce a salable product. We are simply trying to fmd a way

of disposing of a waste in a manner most efficient and economical for the taxpayer.

We are currently investigating two possible outlets for our chipped material. One

is with the local electric power company, Northern States Power, who could, after

certain plant conversions, use al1 of the material we can produce. Since they have large

storage capacity, they can even handle our extreme fluctuations in material flow. The

chips would be fed into their boilers along with coal in producing electricity.

The second possibility is to se11 our chips to Guaranteed Fuels, which has recently

(in cooperation with the Minnesota Department of Natural Resources) completed a

plant for waste wood (in the form of chips) to be compressed into pellets to be used

60
for fuel. Their findings are that the pellets have a BTU content comparable to western

coal. A second fmding, perhaps of more interest to Easterners, is that, although the

BTU content of the pellets is not as high as eastern coal, they have the ability to

counteract the sulftn problems inherent in eastern coal, to the extent that scrubbers

are not needed in many furnaces.

CONCLUSION

In summary, then, there are certain concerns that must be addressed when trying

to find a means of disposing of municipal tree debris:

1. First, it must be completely understood that our tree debris is debris, not a

product .

2. It is something that can be terribly expensive to dispose of; our concern should

simply be to find the most economical method of disposal. If, along with this, a certain profit can be derived, al1 the better. But profit should not be the prime motive.

3. Even though we are trying to do the most economical thing, we must also be

concerned with the side effects of our disposal. In most instances, open burning is

probably the least expensive method; however, it can also cause serious pollution

problems, especially in large metropolitan areas. Landfdling, especially where the landfil1 is owned and operated by the municipality itself, can look very attractive; however,

we need to consider what the future potential of the land could be if it were not

fouled by the burying of logs and brush, and how much the long-term capacity of this

landfill is being shortened by wasting it with this debris.

4. Finally, it must be remembered that the wood from municipal trees is just as

valuable a natural resource as is the wood from forest trees. As with any natural

resource, we have a responsibility to use it wisely. That wise use can vary from putting

it into our homes and structures in the form of lumber, roofing and insulation materials; to turning it into paper and boxboard; to burning it in furnaces, which saves

other natural resources for future use.

61
MULCHFROMLIMBANDTRUNKDEBRIS

Dave Walker’

Abstruct.-Faced with the rising cost of pine straw, Georgia Institute

of Technology experimented with using site-generated wood chips

for mulch. It was leamed that, compared with pine straw, wood

chips were less expensive, longer lasting, less flammable, and better

at retaining soil moisture.

From 1970 to 1978,I worked on a research project at Georgia Tech called Liabilities to Assets. One of the major successes in this program was known as “organic

mulching with wood chips.” It was always interesting to see the expression on people’s

faces when they learned that during the years 1976 and 1977 we were given 10,000

and 9,000 cubic yards of chip material at no cost to the Institute. That we were given

the material was hard enough to believe; however, that the material was processed and

hauled to us for free was even harder to believe in a time when costs are constantly

rising on materials, labor, and equipment.

First, we had to see our own need. That carne in 1970, when funds were hard to

come by for landscaping around our buildings. We thought pine straw was expensive

then, but look at it now!

Second, we had to find an alternative to the straw.Many times we fail to recognize

a good idea simply because we are unable to picture something for what it could

become instead of what it is. In this case, an ice storm during the winter of 1970 caused

us to generate about eight truckloads of chip material when we had to bring in a private tree contractor to clean up the downed limbs. Rather than throw this material

away, we tried using it around one of our buildings as a temporary mulch and found in

the long run that it was far superior to the pine straw we had been using (fig. 1).

Third, we had to find a source of supply large enough to meet our demand. We

found that the tree companies were more than happy to give us the chips if they had a

place to dispose of them at no charge. This is important as an incentive because most

landfills charge a dump fee by the load, yard, or estimated tonnage, which in turn

raises the tree contractors’ overhead. Another way to look at it would be to say

that a contractor’s profit margins increase if his prices stay competitive with other

firms and yet his trucks are able to dump their loads at no charge. Keep in mind, however, that the dumping site must be closer to the job site than the landfill, or the above

principie may not apply. In any case, at Georgia Tech, we had crews hauling to us

when they were within a 3- to 5mile radius of our facility; most landfils were 7 to

30 miles away.

Fourth, we had a responsibility to the contractors. If they were going to process,

haul, and give us the chip material, the arrangement had to be beneficial to them. Our

chip-recycle station was located on an abandoned Street. The paved area meant that

the trucks could come and go in any type of weather without fear of getting stuck in

‘Urban Forestry Consultant, Hayesville, North Carolina.

62
Figure l.-Wood chips provide an attractive mulch around buildings.

the mud or having flat tires, which would certainly be hazards at a local landfill. Because we were given the chips free and did not charge for dumping, the contractors

could dump at their conveniente. Most of the time the trucks would arrive before or

after our normal workday when traffic on the campus was light (fig. 2).

What about the type of material and volume storage? In our research we found

that separating the hardwood and softwood chips was an extra problem for the contractor and required a lot of space. Most crews are chipping up whatever they come to

and do not work on just one type of wood. The combined chip material worked very

satisfactorily as an organic growing medium, as well as being attractive. The rougher,

stringier chips were used to hold steeper slopes (up to 60 percent grades), and the

fmer chips were top-dressed over this or used in areas of lesser grade.

~

As for volume storage, our facility had a total capacity of 10,000 cubic yards.

l However, because we were constantly drawing on our stockpile, we never reached

capacity. Unlike leaves, the wood chips are generated year round, which means that

supply is more constant than seasonal, thus eliminating overloads and handling

problems.

What were some of the advantages in using the chips?

1. Long Zasting.-The chips would last up to 3 years when applied in layers 4 to 6

inches thick.

2. Fire safety.-Our research showed the chips to be far superior to pine straw or

leaves because of the larger particle size and moisture-retaining value.

63
Figure 2.-Ample dumping site with ready access for contractors.

3. Moisture control.-We found that the wood chips would control water runoff

on all grades up to 60 percent, slowing it down to allow for greater soil penetration.

(This does not mean that the chips will not float or wash. Any material will move

given enough forte behind it ; however, under normal slope conditions where a waterhead is not involved [no drainage ditches, or concentrated parking lot, or Street runoff], the chips can effectively control erosion.) Once the soil has absorbed the water,

the chips will drain to soil capacity. After this has occurred, the chip layer will then

act as a moisture blanket, increasing the amount of moisture available to plants even

during droughts. This fact is important in controlling watering and its labor costs as

well as being beneficial for plant growth. No summer slump!

4. Soil amendment.-The chips can be used ín place of peat moss or other soil

incorporants if fertilizer is added.

.S.MuZching.-Chips make a fine mulch. The chips will weather to a uniform

color within 6 months and do not require fertilizer if used strictly as a mulch. After

1 year, this material can be worked into the ground, again without the need for

fertilizer.

6. Fertility.-We did not make any laboratory studies to determine the fertility

value of the chips; however, the observation of plant growth response without any

fertilizer being added on mulched plantings would indicate a moderate supply was

released over a period of time. We observed five varieties of hardwoods during a

study made in 1978, and the results showed a growth response of 3 to 4 feet during

6 4
the first year of planting. (1 might add that this was a very dry year in Atlanta, and no

additional water was added except for two good waterings within 2 weeks after planting in late March.) The trees were 1% to 24-inch yearold seedlings.

What about value? At first, we put a $1 per-cubic-yard figure on the chips just to

give us a means of tabulating some type of value system. However, when the chips are

compared with other materials, a much higher value can be realized.

Material Estimated cost (1978)

Peat moss $30/yard

Perlite $20/yard

Sawdust $5/yard

Vermiculite $20/yard

Given the above figures, it would not be unreasonable to put the value of the

wood chips at $10 per cubic yard. In the beginning, 1 said that we received 10,000 and

9,000 cubic yards of chips during 1976 and 1977. If the chips are valued at $10 per

yard, we received approximately $100,000 per year free.

The chip idea is not a Utopia, and it takes a lot of hard work to get the program

started. A successful program must have a good location convenient to both supply

and demand, an all-weather site, equipment to work it, and personnel who can sell the

idea to local tree contractors as well as local landscapers. But the system does work.

65
PRODUCTS FROM MUNICIPAL TREES

Edward A. Lempickir

Abstvact.-Shade trees along city streets and state highways and those

near suburban homes often reach a large size and have butt logs suitable for many specialty products. However, when these trees are

felled, they are all too often used only for fuelwood or wood chips,

OI hauled to landfiis. The following is an example of one company’s

experience in turning this underutilized material into an interesting

and profitable commodity.

Sam Willard started Shearer Tree Service Company in 1949. Employing approximately 40 people, his company is involved in normal arboreal services such as pruning,

planting, spraying, removal, and maintenance. In 1974, Sam was paying about $20,000

per year in landfill fees to dispose of tree removals. Because of the noncompactable,

bulky nature of this material, the landfill rates were expected to increase steadily, thus

making this form of disposal economically unattractive.

Sam decided to do something about the problem and began his effort with the

purchase of a used Frick Sawmill, along with an edger, crosscut saw, planer, stake

pointer, and metal detector (fig. 1). Instead of hauling his tree removal material to

Figure l.-Urban tree removal material is processed through a sawmill and Alaskan Mill sawing

systems.

lUtilization and Marketing Forester, New Jersey Bureau of Forest Management, CN 028,

Trenton, New Jersey 08625.

66
landfills, he began processing the saw logs through his mil1 and converting the tops to

firewood. Lumber, timbers, nursery and survey stakes were the original products from

the mill. The logs are first scanned with a metal detector before any processing is

attempted. Metal in the form of nails, spikes, or barbed wire is a common component

of logs acquired in tree service work. Once located by the metal detector, the metals

must be removed. This removal can be a time-consuming process; however, this particular mil1 does not concern itself with high production, so the extra time taken to

remove metal from some logs is well spent. Logs are processed on a lumber order basis

and only high-grade lumber (FAS and SEL) is kept in inventory. His suburban location

proved a good spot for marketing specialty products to homeowners in the area.

The mil1 has evolved since its first days of operation and provides a wider range of

products, including free-form furniture, clocks, planters, and decorative plaques. This

type of product is made possible with the use of an “Alaskan Mill” sawing system. This

specialized machinery basically consists of a metal frame with guide rollers, two chain

saw power drives, and a large ripping chain. Suitable logs are elevated at one end and

diagonally cut with the rip chain, which results in thick, matched slabs. These slabs are

used as raw material for the free-form furniture styles: tables of al1 kinds and sizes, bar

and counter tops, plaques, clocks, and many other highly decorative items. Variations

in species, grain pattern, color, and figure greatly enhance the free-form product’s

marketability. This type of sawing accentuates the wood grain in such a way that the

pattern normally produced is quite unlike that shown in standard sawn lumber. Large

stumps and abnormal tree butts are also sawn in this fashion, creating unique and

decorative patterns.

The diagonally cut slabs are stickered and air-dried for 3 months before kiln

drying. The operator uses a small West Air Kiln system for drying these thick slabs.

Kiln schedules are a very important facet of the operation since the product must be

free of checks or splits if it is to bring its maximum price. Normal kiln schedules had

to be adapted to fit this particular type of material. After kiln drying, the slabs are

sanded and sold as is, or are processed into a finished free-form furniture item.

Willard’s sawmill is a classic example of how urban tree removal material can be

processed and marketed. His products are a response to the specific type of raw material handled. The utilization of these municipal trees is almost complete; logs are

processed either through the sawmill or Alaskan Mill, large topwood is marketed as

firewood, branches are chipped at the point of origin and sold as mulch, and the sawdust from the mil1 is sold to local horse owners for use as bedding. This unique urban

sawmill is one answer to the problem of municipal shade tree utilization.

67
FIREWOOD FROM MUNICIPAL TREES

Jay W. Lowery’

Abstraer.-Firewood is becoming a necessary item in the

life of Americans as we face increasing energy shortages.

This paper summarizes an effort to supply the citizens of

Atlanta with an energy source obtained from wood residues

produced from the city’s forestry operation.

We all know that America is the land of plenty; as a consequence this great country

has waste wood byproducts in many forms. It ís estimated that in the city of Atlanta,

67 to 85 percent of materials going into the landfills is wood in the form of paper,

cardboard, and wood scraps. Materials are being buried that could be used for heating

or recycled for products.

The supply of firewood has reached critica1 levels in less fortunate countries. An

average of one-fourth the annual income for an average family in Upper Volta is used

for firewood. In China, the reforestation program is being severely hindered by the

theft of newly planted trees, which are being used for firewood.*

Deforestation, in the name of firewood, has been occurring at alarming rates in

Africa, Asia, and Latin America. As a result, severe land problems are developing.

Erosion and floods are becoming rampant, and deserts are expanding because of the

unstable soil surface created by the loss of trees. Some areas which have depleted their

firewood sources have resorted to burning animal dung, thereby breaking the delicate

balance of the nutrient cycle in crucial areas.

Will this country have to meet a critica1 period before the value of firewood can

be fully realized? Let us look once more to the less fortunate countries: (1) they have

expended, for the most part , al1 firewood materials; (2) they are not prosperous enough

to switch to an oil product; (3) they have no way to stay warm or cook their food.

Result? CRISIS. Solution: A sonic device has been developed that breaks down dung

and other organic materials into methane gas and a byproduct that is good compost.

Here a crisis was needed before a solution to a known problem could be found. The

cost of the project presents a problem; however, it does have potential.

These are extreme cases; however, they are pertinent to the problem at hand. In

our cities we are experiencing similar problems: (1) a high concentration of people;

(2) oil, gas, and electricity are becoming scarce and expensive; (3) the growth of cities

has stifled, if not totally eradicated, the supply of firewood.

Firewood consumption dropped sharply for the first 5 decades of this century

with the onset of oil, gas, coal, and electricity used in cooking and heating. In recent

years, however, firewood has become a sought-after item in today’s markets. The

‘Parks Arboriculture Manager, City of Atlanta Bureau of Parks and Recreation, 260 Central

Avenue, SW, Atlanta, Georgia.

2EckhoIm, E. P. 1975. The other energy crisis: FIREWOOD. Am. For. 81(11):12-13.

68
major part of the market exists in communities in and around the Nation’s cities. A

majority of the homes being built in the East include wood-burning fireplaces and/or

stoves.

Although this trend may be limited by increased air pollution standards, people

continue to search for alternatives to their dependency on oil.

Ironically, there is now cash for both “culled” or “worthless” trees and residues

left by timber or pulpwood operations. This market is either for firewood or chip

material.

In Atlanta, Georgia, the wood residues taken from the 3,000 acres of parks and

5,000 miles of rights-of-way were being buried in the landfills. Within the last few

years, two programs have developed: the increased use of wood chips and the free

firewood program, which has brought tremendous public response and at the same

time saved the city money. It also has reduced pressure on the landfill operations

around the City.

Since 1975, two of Atlanta’s three municipal landfills were closed, placing a hardship on all dumping activities. The one remaining site was located at an inconvenient

area outside the perimeter. Average travel time to and from the area averaged 3l% hours

per day. By having three crews to handle logs and chip materials, a total of approximately 10% hours (depending on weather and traffic conditions) is spent transporting

trees to the landfill area.

A proposal was made to establish three holding areas in Atlanta: one on the north

side, one around midtown, and one on the South side of town. Small areas of parkland

which were not being used and were not close to residents were designated as dumps

for the tree residues.

Before this system could be implemented, the Mayor and City Council had to give

their consent. The city cannot give to a nonprofit organization or dispose of “City

property” without holding a public auction or obtaining the consent of the Mayor and

Council. By identifying the residents of Atlanta as the “nonprofit ,organization” and

proving that the program would save the city money, the proposal was approved.

Costs for using the landfills were as follows:

-average 21 manhours (2 men/truck) at an average of $4.50/hr. = $94.25 per day.

-average 10% running hours at an average equipment cost of $3/hr. = $31.50 per

day. Total: $125.75 per day.

-$125.75 X 5 (days/week) = $628.75 per week.

-$628.75 X 50 (work weeks/year) = $31,437.50 per year.

With the implementation of the program, it was estimated that travel time would

be reduced by 50 percent, a savings of $15,7 18.75 per year. In actuality , there is only

a savings of $10,397.

Now that the political red tape has been cut, the Law Department blessed the

program. Questions were raised about the liability of people cutting wood on city

property. It was decided that warning signs would be erected. Although this action

would not totally relieve the city of its liability, it did give fair warning to users

(fig. 1).

69
Figure l.-Signs were erected to provide warning and use information to the public.

Although there is no one assigned to oversee these woodyards, the implications of

the signs keep the people honest. The reason for the limitations on trucks is to discourage commercial people from taking advantage of this wood source.

In lieu of having a person stationed at each site, al1 crews in the Bureau of Parks

and Recreation have been asked to report any discrepancies they observe, either while

working nearby or just passing the areas. To date, only a few incidents have occurred.

On the few occasions that residents or commercial people have tried to use these

areas for dumping, there have been no problems in having them clean up the area or

prosecuting them according to the dumping laws of the City.

The question of selling this wood was considered; however, this operation is a

temporary measure, and the massive amount of paperwork, amending of ordinances,

and setting up new systems make this impractical.

Firewood has become a backup heating and cooking source during times of ice

storms, floods, and blackouts (fig. 2). The city is working in cooperation with Civil

Defense to supply firewood to victims of any major catastrophe.

Because of Atlanta’s climate and rainfall, wood cut and stored in the open will

last only 3 to 4 months. Each year the City culis decomposing wood and chips for

other uses.

70
Figure 2.-Ice storms produce problems of repair and removal for Atlanta residents, but also

increase demand for firewood due to power outages.

Chips are the most versatile and economical use of wood accumulated in Atlanta’s

system. Chips are being used in place of asphalt, concrete, sand, rock, and dust. Using

chips in place of these materials saves replacement cost, restores nutrients to the regular nutrient cycle, and disposes of a material which was once taking up landfill space.

The encouraging part about wood chips is that after only a few hours of educating

the city administration about the benefits of this byproduct, demand for wood chips

soon exceeded supply. Presently, requests average 80 truckloads (40,320 cubic feet)

per week. With the existing resources, the program is able to supply only 10 truckloads (5,040 cubic feet) per week, with 20 loads (22,400 cubic feet) of wood going to

the woodyards. With the purchase of a whole-log chipper, the program wiI1 not be able

to meet the current need, but we will be using all wood waste products.

Future efforts are being directed toward using waste materials from tree businesses, utility companies, and, possibly, construction companies in an effort to increase

the supply of chips in the system.

Chips, as mentioned before, are replacing traditional ground covers in the park

system. However, all trees, shrubs, and flower boxes do not have a mowing edge of

mulch around them, nor have al1 the banks of the park system been erosion stabihzed.

71
The only problem in using chips was presented during an arts festival where they were

being used as a ground cover in a tent. The Fire Marshall refused to approve “flammable material” being used in an “enclosed” area, even though the chips’ waterretaining ability was higher than the first 3 inches of soil.

If you have a valuable resource such as firewood or chips, get excited about it;

you are sitting on a gold mine. You may not be able to prove savings in actual budget

dollars, but improving an operation, developing a complete environment, and solving

maintenance problems are measures which cannot be budgeted for, but they do save

dollars.

72
FUEL PREPARATION FOR WASTE WOOD BOILERS

Alex D. Cobb, Jr.’

Abstract.-After proper preparation, wood residue may be used as

fuel or as raw material for such products as horticultura1 mulch,

animal bedding, poultry litter, particleboard, fiieplace logs, and fuel

pellets. The reuse of waste wood requíres an understanding of waste

wood boilers, wood-reduction machines (hogs), waste loads, economic considerations, and the services provided by consultants.

INTRODUCTION

Annually the volume of solid waste in the United States amounts to over 4 billion

tons and is increasing at a disturbing rate. Everyone-producers and consumerscreates solid waste. The larger and more affluent the population, the greater the volume of solid waste. The problem is compounded by archaic municipal and county

collection and disposal practices.

Of the solid waste produced annually in the United States, animal waste accounts

for some 2 billion tons; mineral waste for more than 1 billion tons; agricultura1 waste

for nearly 650 million tons; household, commercial, and other municipal waste for

about 300 million tons; and industrial waste for almost 130 million tons. Projections

are that solid waste generated in the metropolitan areas will more than triple by the

year 2000.

Sixty-five percent of our population now lives in urban areas. Generally, cities

settle for the least expensive means of solid waste disposal-open dumping and open

burning. These methods pollute the air and water, devour valuable land, pose fire

hazards, breed germs and-worst of all-waste natural resources. Over the last 5 or 10

years, air and water pollution problems have caught the interest of the public. Only

recently has attention been given to solid pollutants and the need to conserve valuable

materials that would otherwise be lost in countless city and town trash heaps.

There is uncertainty about how much municipal waste goes where, but the Federal

Government has estimated that 77 percent goes to open dumps, 10 percent to incinerators, and 13 percent to sanitary landfills. The remaining waste is converted into compost or salvaged for reuse. Studies have shown that waste wood constitutes 10 to 20

percent of landfill material and takes a disproportionate share of landfill space because

it does not compact as well as other materials. Furthermore, as buried wood begins to

decompose it forms methane, which is a colorless and odorless but highly inflammabie

hydrocarbon gas, sometimes known as marsh gas. Gasification of the rotting wood

causes pockets which later collapse in the landfill.

What is the solution? The open dump is not the solution. Sanitary landfills are

only a stopgap measure. Incineration is becoming increasingly costly and is subject to

stringent EPA regulation. More importantly, none of these methods recovers resources;

IDirector of Marketing, Jacksonville Blow Pipe Company, Division of Montgomery Industries

InteInational, 2017 Thelma Street, Jacksonville, Florida 32206.

73
they merely dispose of them. The method of the future, therefore, is to reclaim much

of our urban refuse and reuse it .

WASTE AS FUEL

Many industrial plants are spending considerable amounts of money to get rid of

waste materials that are a potentially valuable supplemental energy source. One study

indicates that combustible waste equivalent to over 700,000 barrels of fuel oil is thrown

away daily in this country.

Plenty of waste is available, the equipment to process and burn it is on the market,

and the economics are favorable. In addition, burning waste as a supplemental energy

source reduces fossil-fuel requirements. For example:

-Less than 1% tons of general plant waste produces heat equivalent to that produced by 1 ton of coal.

-0ne ton of this waste produces heat equivalent to that produced by over 60 gallons of fuel oil.

-Less than 1 ton of this waste produces heat equivalent to that produced by

8,000 cubic feet of natural gas.

Any plant requiring 1,000 pounds of steam per hour and generating 1 ton of waste

per day should consider using waste-fuel firing as a supplementary source of energy.

Three factors should be considered when the potential of waste as a fuel source is

being evaluated: the amount of onsite waste produced; the BTU content of this waste;

and an economic comparison of the waste wood fuel and the fuel presently in use.

The following chart shows the heating values of some common waste wood

materials:

HEATING VALUE OF COMMON WASTE MATERIALS

Waste material Heating value/lb (as fired)

(BTU)’

Used automobile tire casings . . . . . . . . . . . . . . _ . .

Type “0” trash (paper, cardboard, wood, boxes,

13,000

sweepings . . . . . . . . . . . .................

Wood sawdust (pine) . . . . . .................

Wood sawdust. . . . . . . . . . .................

Wood bark (Br). . . . . . . . . .................

Wood bark . . . . . . . . . . . . .................

Oak scrap. . . . . . . . . . . . . .................

Pine scrap . . . . . , . , . . . . . .................

‘BTU = British Thermal Unit-the amount of heat required to raise the temperature

of 1 lb. of water lo F at or near 39.2’ F.

8,500

9,600

7,800-8,500

9,500

8 ,OOO-9,000

7,990

8,420

Many industries with high energy requirements are switching from fossil fuels to

wood. Wood-energy production could play a very important role, especially in such

highly timbered areas as the South and West.

74
RECOVERING THE COST OF CONVERSION

Industry experts have estimated that the cost of converting to a waste wood boiler

can usually be recovered, from savings, within 3 to 5 years, depending on the location

of the plant, the type and amount of onsite waste generated, and the cost of other fuels.

A major factor to be considered is the rather high initial capital cost to purchase

and install the fuel-handling, processing, and firing equipment required with a waste

wood burner. However, this is more than offset by wood fuel that will be used at a

cost vastly lower than that of commercial-grade fuel oil or natural gas.

In one system, which is about 3 years old and uses the fluid-bed combustion

chamber, the total first-year investment in boiler-house equipment and a 20,000

cubic-foot material-handling system carne to $240,000. However, the first year’s fuel

savings (using wood residue instead of 1 million gallons of No. 6 fuel oil at $0.30/gal)

amounted to $285,000. Subtracting $7,770 per year for increased maintenance costs,

electricity, and insurance resulted in a net savings of $277,230. So, in the first year the

owner saved enough to pay for the system, plus a small profit. In succeeding years, he

will be putting at least $277,230 annually toward profits.

TYPES OF WASTE WOOD BOILERS

Numerous conventional boiler systems are now being designed and installed to

provide industry with heat, process steam, and onsite electricity from raw-wood

material as a fuel. These systems are primarily of three basic types:

D~tch oven.-The oldest and most simple boiler system-though not necessarily

the most efficient or the most pollution free-is the Dutch oven. This is a large refractory-lined compartment, with grates, which sits in front of and below a boiler. A large

pile of fuel-in our example, shredded or hogged wood scrap-is maintained in the

oven, where primary breakdown takes place. Combustion is completed in the chamber

situated behind the radiant section of the boiler. The Dutch oven has been known to

perform satisfactorily even with very wet fuel, but it does not respond well to widely

fluctuating steam demands, as the large pile takes considerable time to burn down or

build up, and the system must be attended constantly. Nevertheless, if fired conservatively with a reasonable fuel (not overfired), Dutch ovens can meet most anti-pollution

requirements.

Stoker feeder.-A second, very popular way to fire wood in a boiler is through a

stoker feeder or spreader-stoker. Here the incoming fuel is metered into a wide, flat,

horizontal air stream and spread in a thin bed over grates for aeration and uniform

exposure to combustion. Fuel feed is more easily controlled to follow fluctuations in

steam demand. If the grates are at the bottom of a rather large refractory-lined combustion chamber, performance can be quite satisfactory. However, it should be pointed

out that stoker-fed systems, in general, require cinder reinjection and high-efficiency

collection equipment to meet today’s rigid air pollution standards.

Suspension bumers.-A third boiler system burns the fuel in suspension; these are

of two types: (1) A cyclonic burner, which usually requires dry fuel with moisture

content of 1.5 percent or less, as might be found in dry planer-mil1 shavings, sawdust,

or kiln-dried wood scrap. The material must be tinely pulverized for feeding the

75
burner. (2) A fluidized bed unit which burns either dry or wet fuel having up to 55 or

60 percent moisture content. The dryer wastes, of course, have a higher BTU content.

For example, kiln-dried scrap wood contains approximately 16 million BTU’s per ton,

which is the equivalent of 114 gallons of fuel oil or 16,000 cubic feet of natural gas.

Waste wood boilers must, in most cases, be prepared to operate overnight and on

weekends. Thus, it will be necessary to have a storage system for the wood fuel, just as

it is necessary to provide onsite storage for fuel oil or liquified gas. Storage bins used in

connection with waste wood boilers are generally tall silos with either mechanical or

pneumatic infeed and discharge conveying systems for loading and unloading. The

wood fuel must be hogged (reduced in size) to facilitate storing and conveying. Hogging is necessary even though some of the units will burn large chunks of wood; obviously, large chunks cannot be stored or conveyed well, so, it is necessary to hog the

fuel down to a manageable size.

FUEL PREPARATION HOGS

Fuel preparation for waste wood boilers is accomplished by a machine called a

hog-sometimes referred to as a hammermill, shredder, or pulverizer. The derivation of

the term “hog” is not accurately known, but it may have something to do with the

voracious appetite these machines have for devouring waste materials-especially wood

waste from sawmills, lumber mills, plywood and veneer plants, wood-manufacturing

operations and, of course, urban wood waste. Hogs are used to grind bark-large quantities of it, in fact-which is removed from the raw logs in sawmills and pulpmills.

Some hogs employ a unique cutting action involving stationary anvils positioned

on the side of the machine with rotating teeth (hammers) that pass through rectangular pockets formed by these anvils. This positive cutting action between the teeth and

the anvils performs what amounts to the first particle-sizing function in a two-stage

process.

The second sizing action occurs when the material cut by the action of the teeth

against the anvils is directed downward and across a curved particle-sizing screen which

fits underneath the rotating element . The screen contains either round or rectangularshaped openings whose size is determined by the specific application for which the

machine is sold. Obviously, small, round or square holes are used to produce fine, sawdust-like material; larger round or rectangular openings produce chunky pieces having

a greater cross-section and length.

Hogs can be furnished with either gravity infeed or horizontal infeed of the

material to be processed. However, horizontal infeed models, which are designed

primarily for handling long, flat pieces of scrap over 8 feet long, have restrictions on

the thickness of material which may be processed, depending on the diameter of the

cutting circle. None of these horizontal-feed models would be suitable for certain

types of waste, such as bark, small cutoff and blocks, loose sheets of paper, and similar

materials.

Hogs made by Montgomery Industries, for example, are available in the following

series: HD, PM, PM-KC, CS-KC, XL-KC, and NAS. The difference in each series is the

diameter of the cutting circle of the teeth and/or whether the anvils are mounted on

the side of the hog in a stationary position (as is the case with HD and PM models), or

76
mounted on a pivot shaft to swing away from the cutting area on severe impact with

tramp steel (as with the KC and NAS models).

VARIETIES OF HOGS

The HD model has an 18Wnch cutting circle, and the PM model has a 22-inch

cutting circle. Both models employ 2-inch-wide cutting teeth and 2-inch-wide anvils

mounted on the side of the housing. The anvils are adjustable to maintain the proper

tooth-anvil clearance for efficient hogging. The wear surfaces of both teeth and anvils

are hardfaced for extra long life, and when worn may be rebuilt at about half the cost

of new parts. The hogs will handle light tramp steel 1/4 inch and smaller, nails, small

bolts, and steel strapping. An interna1 bronze shearpin arrangement protects against

damage from heavy tramp steel.

The HD and PM models can be furnished with either gravity discharge or an

integral fan for applications where it may be more convenient to pneumatically convey

the material after grinding. The integral fan model uses less floor space than a gravitytype hog with a separate fan, as only a single motor and drive is required; two motors

and two drives are required when the fan and hog are separate.

The HD and PM models are normally equipped with a steel flywheel which

provides additional energy to carry the rotor through surge loads. Integral fan models

normally require a V-belt drive because the shaft speed seldom coincides with the fullload motor speed. Bottom discharge models are normally connected directly to the

motor with a flexible coupling because the first cost on the flexible coupling is lower

than the cost of a V-belt drive.

The range of sizes on the HD and PM series, measured parallel to the shaft, starts

with a small lo-inch model and increases in 8-inch increments to a 74-inch rotor

length. Such hogs are generally used for most light and medium sawmill, lumbermill,

and wood-furniture applications to process wood scrap, small quantities of bark,veneer

roundup, broken pallets, and similar industrial waste.

Cutting circles on the KC and NAS hogs range from 22 to 54 inches. The teeth

and anvils on these models are 3 inches wide and are hardfaced for extra long life. The

anvil points are mounted on swinging anvil holders supported in a yoke and pivoted so

they will swing away from the cutting circle if large tramp steel enters the hog. On

such occasions, a trip latch releases and drops the screen, preventing serious damage; a

pressure switch activates a signalling device which informs operating personnel that the

protection mechanism requires resetting.

The KC models and the NAS hog are designed for gravity discharge only, with the

exception of one model of the Montgomery Railroad Crosstie Destroyer, which accepts

full-length ties horizontally. No flywheels are required with these models because of the

large mass of the rotating element. Sizing on the KC models, measured parallel to the

shaft , commences with 1.5 inches of rotor length and increases in ó-inch increments to

75 inches. The NAS model has been built as large as 87 inches of rotor length. Applications include grinding heavy bark (in sawmills and pulpmills), railroad crossties and

boxear dunnage, demolition waste, tree limbs, discarded tire casings, and soft metals.

77
SELECTING THE PROPER HOG

There are three rnajor factors to be considered in selecting a hog for any application: the size of the waste, including length, width, and thickness; the quantities of

waste, including average flow rates and maximum surge rates; and the desired size and

use of the final product.

First, the bulk dimensions of the scrap must be known to ensure that the waste

material will fit into the opening of the hog. When dealing with urban wood waste, the

maximum width of the scrap is used to determine the minimum hog infeed opening

parallel to the shaft. The maximum thickness of the scrap and the type of material are

used to determine the proper bearing size. The maximum length of the scrap is used to

determine the height of the upper infeed hopper, if a gravity-infeed model is selected,

or whether the length of the material requires a horizontal-feed model.

Second, the capacity of the hog selected for a given application must be adequate

to handle not only the average flow of incoming material, but also occasional surge

loads caused by a sudden buildup on the infeed conveyor.

Third, the required particle size governs the screen size, and this in turn has a

substantial bearing on hog selection and capacity. The larger the screen openings, the

larger the hog capacity for a given size. If the desired size of the end product and its

use are known, it is possible to select a screen opening that will produce the appropriate product. The following chart shows the capacities of various hogs:

WOOD BLOCKS, EDGINGS, AND SLABS

Average capacity (lbs/hr)

Hog size

HD series

(inches) 3

>,

Screen size

1’/2”’

HP required

Max. Min.*

18 10,800 5,400 2,700 97 50

34 20,400 10,200 5,100 182 50

58 34,800 17,400 8,700 310 60

’ The screen area on slabs must be 2 inches or larger to keep the screen from filling up with

chips and acting as a brake on the rotor.

*Minimum horsepowers shown are required to accelerate the hog up to speed (normally

1,200 RPM) within 30 seconds.

There are many other factors used in selecting the correct hog for a given application. Among these are: size of infeed opening, bearing size, maximum bearing speed,

wood species, and drive selection.

SCREEN SIZES FOR WASTE WOOD BURNERS

For hogs used in the preparation of fuel for waste wood burners, there are three

size ranges, depending upon the type of boiler in use. For toarse boiler fuel, a 3-inch

screen is recommended. For grinding waste wood to use as fuel in boilers with automatic stokers or fluid-bed burners, screens with 2-inch holes are recommended, as are

baffles welded transversely along the outer surface of the’screen to prevent sticks from

78
passing into the discharge conveying system, thus causing a blockage somewhere down

the litre. Cyclonic-type burners need a two-stage grind to produce the finely pulverized

material required to support combustion: the primary breakdown unit uses a 1-inch

screen; the secondary unit is a high-speed hammermill that reduces material to less

than % inch.

ESTIMATING WASTE LOADS

The prospective customer for a fuel-preparation hog would be expected to furnish

the average and surge flow rates of material going to the hog. These rates should be

incorporated into the quotation by the factory as part of the design conditions under

which the performance of the hog is guaranteed. Consulting engineers or suppliers of

waste wood boiler systems will generally verify these figures with the hog manufacturer.

In the case of wood-processing industries, such as pulpmills, sawmills, veneer milis,

dimension mills, and other lumber manufacturers, certain waste factors are known

from experience and can be used as rules of thumb in estimating the amount of wood

scrap available for boiler fuel or other recyclable material. Following are some examples:

PuZpmiZl.-The bark from a standard cord of wood (128 cubic feet) will weigh 700

pounds at 50 percent moisture content. The quantity of oversize chips produced

when chipping a cord of wood is approximately 5 percent.

SzwmiZZ.-Determine plant production in log feet per hour. For estimating purposes, use 1,200 pounds of bark per 1,000 log feet. The amount of green sawdust

produced when sawing logs to produce 1,000 board feet of lumber is approximately 2,000 pounds per 1,000 log feet.

Veéneer mill.-Determine plant production in log feet per hour. The amount of

veneer roundup and clippings is approximately 5,500 pounds per 1,000 log feet.

The amount of cores produced, whether hogged or chipped, is approximately

2,450 pounds per 1,000 log feet.

Planer mill.-Multiply the plant production in board feet per hour by 5 percent

to determine the waste load in board feet per hour. Then multiply this quantity

by the weight per board foot to determine the waste load in pounds per hour. For

estimating purposes, use 2% pounds per board foot for pine; 3l% pounds per board

foot for hardwood.

Dimension pZant.-Multiply the plant production in board feet per hour by 45 percent to determine the waste load per hour in board feet per hour. Then multiply

this quantity by the weight per board foot to arrive at the waste load in pounds

per hour. For estimating, use the same weights for pine and hardwood listed above

under Planer mill.

Furniture plan& industrial and urban wood wastes.-Where the customer does not

have accurate information on the expected waste loads, but the material is being

accumulated (perhaps from a belt conveyor, in buggies, carts, bins, or haul-off

79
containers) determine the cubic content of the bln or container and reduce this

quantity by 50 percent to allow for voids which are created when material is

tumbled loosely into the container. Multiply this approximate volume of solid

wood by the appropriate density factor in pounds per cubic foot to determine the

quantity of actual waste in pounds for each load. Knowing the average number of

loads for each container on an hourly or daily basis would provide a fairly accurate basis for selecting the proper hog size. An alternative method where material

is being conveyed on a belt would be to scrape off and weigh the material that

passed a certain point on the belt in 15 seconds, then multiply this weight by 240

to obtain the approximate pounds per hour to be processed by the hog.

CONCLUSION

Because all plants, as well as their energy requirements and applications, are

different, a plant considering conversion to waste wood fuel should commission an

energy study by a qualified employee or outside consultants.

In addition to its use as fuel, waste wood has many other potential applications.

Wood residues have the following uses: as animal bedding and litter to be sold to riding

stables, kenneis, stockyards, zoos, biological Iaboratories, and auction barns; as absorbent materials to be sold to service stations, machine shops, butcher shops, and meat

backers; as mulch to be sold to nurseries, landscapers, gardeners, and government

agencies; and as industrial supply for making particleboard, fiberboard, hardboard, and

tnolded products.

80
MARKETING URBAN WOOD RESIDUES

John W. Howardl

Abstract.-This study defiies the characteristics of wood residues

that affect their marketability, discusses the processingrequired to upgrade residues to useful wood fiber, and Iists potential ma.rkets and

dollar values for various residues.

In this presentation, 1 will discuss the characteristics of wood residues that affect

their marketability, the types of processing required, the potential markets, the procedures for marketing, and the monetary value involved.

The characteristics of wood residues that affect marketability and value are:

species, moisture content, physical form, and degree of cleanliness. Wood residues

may be composed of hardwood species, softwood species, or a mixture of both. Creen

wood contains 40 to 50 percent moisture, air-dried wood 15 to 25 percent, and kilodried wood less than 10 percent. Wood residues may exist in the form of sawdust,

shavings, chips, slabs, boards, blocks, trunks, limbs, leaves, or twigs. Wood residues

may be clean, or they may be contaminated with dirt, metal, concrete, paper, plastics,

or other debris.

The species and moisture content are fixed; they are determined by the source.

The physical form and cleanliness will depend on the source but can be altered by

processing. The processing has to be justified by the markets available and the dollar

value that can be realized by upgrading the residues.

Essentially al1 types of wood residues are now marketable if the supply is within

reasonable distance of the consuming point and the residues are clean and of the right

physical form .

The greatest potential outlets, by far, are agricultura1 and fuel uses. All residues in

sawdust or shavings are valuable to farmers for bedding and ground control for livestock. Fuel will be the greatest outlet in the near future since the price of oil is escalating rapidly. However, wood residues for fuels require processing to be marketable

and to realize their optimum value. Each type of wood burner is designed to handle

wood in a specific physical form.

1 will define the types of residues by markets and by specifications required of

the residues for processing or use as is (tables 1 and 2).

Wood residues for markets requiring exact processing (fillers for plastics, paper,

fur cleaning, and foundries) have to be ground and sized in their applications. Chemical and physical properties are critical. These residues are usually from secondary wood

manufacture and have exact specifications. These residues have the greatest value but

are not typical of urban wood residues unless the governmental agencies involved

‘Preside@ Can-Am Sales Corporation, Fibers & Fillers, Inc., Box 158, Skaneateles, New

York 13152. 1

81
Table l.-Markets requiring exacting processing and specifications for wood residues

End use Species Moisture Physical form Cleanliness

Woodflour manufacture

Paper filler

Foundry filler

Fur cleaning

Firelogs

Softwood

Softwood

Hardwood

Hardwood

Softwood

Hardwood

Under 8%

Under 10%

Under 10%

Under 10%

Under 15%

Secondary residues

Secondary residues

Secondary residues

Secondary residues

Secondary residues

Very pure

Clean

Clean

Clean

Clean

Table 2.-Other markets for wood residues

End use

I

Species Moisture Physical form Cleanliness

Fuel Hardwood

Softwood

Mixed

lo-20%

Green

Sawdust

Shavings

Hog fuel

Wood chips

Sander dust

Bark O.K.

Debris &

dirt free

Particleboard Hardwood

Softwood

Dry

Green

Secondary

Residues

Clean

Sewage composting Hardwood

Softwood

Green Wood chips

Total-tree

Chips

Debris

Free

Agriculture Hardwood

Softwood

Dry or

Green

Sawdust

Shavings

Clean

Paper Hardwood

Softwood

Green Wood chips

Hog wood

Clean

require industrial wood residues to be considered as part of the urban residue program.

1 list these to show the breadth of the residue markets.

A second category includes the major applications of wood residues. Included are:

general urban wood residues encountered in disposing of land clearings, packaging

residues, dunnage, demolition lumber, tree tops, limbs, and stumps. Essentially all of

these residues require processing in equipment. Their use requires large volumes and

specific physical forms of residue.

1 will define the procedures for marketing residues:

1. Characterize residues according to species, moisture, form, and cleanliness.

2. Determine potential marketing outlets.

3. Locate potential markets within economically feasible shipping range.

4. Determine end use and physical form required.

5. Evaluate against dollar value available.

6. Evaluate costs of upgrade and market.

82
7. Obtain sales commitments prior to investments.

8. Locate minimum-cost disposal if marketing is not feasible.

Freight costs are the most significant factor in marketing wood residues. Green

materials contain 50 percent water by weight. Shipment beyond 150 miles will usually

not be feasible; freight costs will offset the value of the residue.

Specialists in marketing wood residues are available to evaluate residues and provide advice about obtaining optimum dollar value. Specialists include: brokers, state

and federal forestry specialists, industrial representatives from papermills, particleboard plants, professional forestry associations (such as FPRS).

Estimated dollar values listed for wood residues are based on the ultimate end use

and processing required. Obviously, the more demanding the specifications, the higher

the value and the less supply. In large-volume uses, supply is often abundant and the

dollar value is lower .

ESTIMATED DOLLAR VALUE FOR RESIDUES

1. High specifications (exacting processing required):

(a) grinding and screening @SO-$80/ton delivered),

(b) secondary residues ($20-$45/ton delivered; dry, clean, specific species)

2. Intermediate specifications (specific physical forms required):

wood chips, hog wood, species limitations ($18-$35/ton delivered)

3. Low specifications (liberal requirements on physical form):

sawdust , mixed materials (S lo-$1 8/ton delivered; unlimited species).

1 have three case histories of marketing urban wood residues that will illustrate

processing and dollar value.

The first example is converting pallets, packaging, dunnage, and miscellaneous

waste wood from a large industrial plant into hog wood for fuel. This installation is at

Kodak Park, home of Eastman Kodak in Rochester, New York. A small tractor is used

to crush oversize material such as pallets, and the material is then mechanically scooped

up and through a hog mounted on the tractor. This procedure allows Eastman Kodak

to convert waste wood, that is expensive to dispose of, into hog wood fuel Worth $20

to $30 per ton on a BTU basis when incinerated in a burner producing low-pressure

steam for plant consumption.

The second example is improving sewage treatment where green sawdust is used as

a fuel and a filter aid in treating the sludge. This is done in Monroe County, Rochester,

New York, with sawdust delivered at $15 per ton in dump trucks and self-unloading

trailers.

The third example is preparing hog wood for pressure fiber processing for paper

filler. Separated softwood dunnage and packaging residues collected in northern New

Jersey are hogged to small size and delivered to GAF, Gloucester, New Jersey, for conversion to a filler for industrial paper. The value of the wood is approximately $25 per

ton delivered.

83
SUMMARY

Marketing wood residues is complex because essentially all end uses require specifications of some kind on physical form, moisture, and cleanliness. Use of marketing

specialists is strongly recommended to obtain the best dollar value and least cost and

investment .

84
SEGREGATION PROCESSES FOR URBAN WASTE WOOD

John A. Sturos’

Abstract.-Three technologies-steaming-compression debarking,

vacuum-airlift segregation, and photosorting-have been developed

for improving the quality of whole-tree and wood-residue chips.

Application of these processes coupled with integrated utilization of

the various output wood fractions should lower the barriers for

increased urban waste wood utilization.

A tremendous underutilized wood resource exists in urban areas in the form of

tree removals and trimmings, industrial waste, demolition wood, and secondary manufacturing residue. In 1976 the total urban wood residue was estimated to be more than

16 million air-dry tons (table 1) (Carr 1978). Demolition lumber alone accounted for

6.4 million air-dry tons, or 39 percent of the total. One municipality has estimated

that it will have to dispose of 10,000 tons of wood per year from diseased trees for

the next 8 years, and tree trimmings could be more than 1,000 tons per year from an

urban forest of 140 square miles (Ratcliffe 1976).

Table I.-Estimates of urban wood residue generated in 1976’

Source of wood residue Thousands of tons (airdry)

Tree removals and trimmings 2,820

Demohtion lumber 6,410

Pallets, containers, dunnage 4,790

Secondary manufacturing residue 2,400

Total 16,410

’ Carr (1978).

Excluding secondary manufacturing residues, the degree of urban waste wood

utilization in 1976 was very low (table 2) (C arr 1978). Only 2 percent, 15 percent, and

30 percent of the demolition lumber, urban trees, and industrial and commercial wood

waste, respectively, were used. The remaining wood was either used for landfill or

incinerated.

Cities and highly populated counties are currently being forced to process their

wood waste because disposal by incineration and/or landfill is no longer acceptable. To

increase urban waste wood utilization, new and improved roughwood processing equipment and methods must be developed to convert these materials to marketable products. Hopefully this will promote integrated utilization so that each of the various

components of the urban wood waste can be used for its highest value end use.

‘Principal Mechanical Engineer, North Central Forest Experiment Station, Forestry Sciences

Laboratory, Houghton, Michigan.

85
Table 2.-Estimates of urban wood utilization in 1976’

(In thousands of airdry tons)

Use Urban

trees

Secondary

Industrial, Demolition manufacturing Total

commercial waste residues

Fuel, industrial &

residential

Pulp, composition

board

Mulch and bedding

Salvage for lumber

Saw logs

Miscellaneous

Landfill or incineration

280 960 850 2,090

60 240 470 770

480 480

110 110

80 80

240 150 390

2,400 3,350 6,300 440 12,490

Total 2,820 4,790 6,410 2,390 16,410

‘Carr (1978).

Research on improving the quality of whole-tree or wood-residue chips has

resulted in severa1 promising segregation processes. These processes should be considered for incorporation into an integrated urban waste wood recovery system. This

paper discusses these segregation processes.

SEGREGATION PROCESSES

Research on the beneficiation of whole-tree chips or contaminated residual chips

at the Forestry Sciences Laboratory of the North Central Forest Experiment Station,

USDA Forest Service, Houghton, Michigan, has resulted in three promising processessteaming-compression debarking,vacuum-airlift segregation,and photosorting(Mattson

1975; Arola 1976; Sturos and Brumm 1978). In addition, combinations of the above

processes are possible.

STEAMING-COMPRESSION DEBARKING

The steaming-compression debarking process has been put into practice by Parsons & Whittemore, Inc., who designed and built a debarking plant at one of their

pulpmills. The results of their first 16 months of operation are similar to those obtained

in Forest Service research studies (Wawer and Misra 1977). The basic process consists

of three steps: (1) presteaming the unbarked chip mass, (2) passing the chips through

a compression debarker, and (3) screening the compression debarker output to remove

bark fines (fig. 1). Additional (optional) steps include mechanical attrition of the

smaller chip output fractions followed by screening to remove additional fines.

In cooperation with Urban Wood and Fiber Products, Inc., steaming-compression

debarking of elm chips was evaluated (table 3). Results indicate that 66 percent of the

bark was removed and 85 percent of the wood recovered with a final bark content in

the accept fraction of 3.1 percent. By including only the +3/8-inch-size chips in the

accepts, the bark content decreases to 1.6 percent but yet more than 60 percent of the

wood fiber is recovered.

86
SR-SMOOTH STEEL ROLL

KR-KNURLED STEEL ROLL

lI- NIP SETTING

1 I t I I I I 1

/HYDRAULIC ““‘UY-J

CYLINDER /qBAFFLEs / 1 \

REJECT WOOD PRODUCT REJECT

v COLLECTION CONTAINERS /

Figure l.-Compression debarker.

Table 3.-Results of steaming-compression debarking of elm chips’

Product

Input Bark Total Total

material content wood bark

Accepts

+3/8” fraction

-318 + 3116” fraction

. . . . . . . . . . . . . . Percen t . . . . . . . . . . . . . .

51.1 1.6 61.4 12.3

23.6 6.9 23.1 21.6

Combined accepts 81.3 3.1 85.1 33.9

Rejects 18.7 26.4 14.9 66.1

Input 100.0 7.5 100.0 100.0

’ Chips supplied by Urban Wood and Fiber Products, Inc.

87
VACUUM-AIRLIFT SEGREGATION

The vacuum-airlift segregator has received laboratory scale testing both by the

USDA Forest Service and by industry. It consists of a wire mesh conveyor belt with

vacuum hoods placed above the belt at various stations (fig. 2). Whole-tree chips are

spread over a continuously moving conveyor belt that passes through fields of air

currents that subject the chips to vacuum forces from above the belt. The material is

then segregated on the basis of differences in terminal settling velocities caused by

density and geometric differences. Typically, in a multiple-stage system, foliage, clean

wood chips, and ‘middlings” are removed at different locations along the belt. Bark,

knots, and twigs remain on the belt to discharge to a “reject” product area, and finesbark, some foliage, dirt, and grit-fall through the mesh belting.

DISCHARGE

VALVE

MIDDLINGS

---------- CONVEYOR

BARK

CONVEYOR

Figure 2.-Multiple-stage vacuum-airlift segregator. Fines fall through the wtie mesh conveyor.

The “middlings” fraction contains from 30 to 50 percent of the total input

material, depending on species, and has a bark content equal to or higher than the asreceived whole-tree chips. This fraction can be used for pulp, particleboard, fuel, or

chemicals. If the middlings are to be used for pulp, further beneficiation by the

compression debarking process is recommended.

For maximum recovery of “clean” fiber, a combined system is recommended

(fig. 3) (Sturos 1978; Sturos and Marvin 1978). It consists of vacuum-airlift segregation followed by steam-compression debarking of the middlings fraction (table 4,

fig. 4). By means of the vacuum-airlift stage, 4 percent of the input is removed as commercial foliage, 4 percent falls through the wire mesh conveyor as fines, 42 percent is

recovered as clean wood chips acceptable for pulping, 36 percent is recovered as middlings, and 14 percent is left on the conveyor as bark (fuel). Passing the middlings

through the compression debarker results in an additional 29 percent clean wood

88
chips .and 7 percent bark. The combined product recovery results are 71 percent

fiber, 25 percent fuel, and 4 percent foliage.

Figure 3.-Combined vacuum-airlift and compression debarking system for beneficiating whole-tree

chips.

Table 4.-Typical fohage and bark removal results obtained by combinmg the vacuum-airlift and

compression debarking processes’

Process and components Aspen

sugar White

maple birch

Vacuum-airlift segregation:

Input bark content

Bark content

Wood recovery

Bark removal

Foliage removal

. . . . . . . . . . . . . . . . . . .

20.2 13.2 16.4

4.8 5.1 1.6

52 31 40

51 41 45

84 85 94

Vacuum-airlift & compression debarking:

Input bark content

Bark content of accepts

Wood recovery

Bark removal

Foliage removal

20.2 13.2 16.4

5.3 5.3 5.9

88 81 81

80 69 13

86 86 94

’ Ah calculations are based on dry weight.

89
\PRODUCT)

71%

ASPEN WHOLE - TREE CHIPS

CLEAN

FOLIAGE i

c---- VACUUM - AIRLIFT CHIPS BARK 4 %

42% - 14% *

l

1) FINES

4 %

@IDDLINGS)

36 Yo

r

. CLEAN COMPRESSION BARK

CHIPS DEBARK 7 %

29%

/ FUEL \ ,’ FOLIAGE

QR~DUCTJ \PRODUCTJ

25% 4 %

Figure 4.-End products and intermediate steps in segregating aspen whole-tree chips.

PHOTOSORTING

Wood and bark chips differ sufficiently in their optical transmittance to be sortable.

When photosorting, the chips are fed by a conveyor over a linear array of optical

detectors (fig. 5). Light from an incandescent source is incident on the chips from

above. The light intensity is adjusted such that most wood chips transmit sufficient

light to be sensed by the detector array. When a bark chip passes over the detectors,

the transmitted light falls below a preset detection threshold and the detector photocurrent decreases. The resulting signa1 is amplified to energize an air valve, which

deflects the bark chips with a blast of air (fig. 6). Preliminary results for 5/8-inch aspen

chips are promising (table 5). Depending on light level, bark content of 1.4 and 5.1

percent with corresponding wood recoveries of 70 and 96 percent are possible.

ECONOMICS

The Forestry Sciences Laboratory has conducted severa1 cost analyses of the

steaming-compression debarking system, the vacuum-airlift system, and combinations

of these two systems. They have revealed that the combined system is the most cost

efficient . One of the primary advantages of coupling the vacuum-airlift segregator and

the compression debarker is to reduce capital equipment cost and consequently, beneficiation cost. This decreases the amount of material the compression debarker has to

process, which in turn reduces steam requirements, the size of the press, and therefore

cost. The beneficiation costs (1978 basis) range from about $6.70 per output dry ton

of “clean” chips for a steaming-compression debarking system to $4.70 for a combined system in which only 34 percent of the material is compression debarked. Total

capital investment for a 60 ton per hour debarking plant ranges from about $3 million

90
for a steaming-compression debarking plant to $1.7 million for a combined vacuumairlift and steaming-compression system.

LIGHT

\k

CHIP /227--c

PHOTOCELL ARRAY t AIR NOZZLE

AIR VALVE

h

-

THRESHOLD DETECTOR - AMPLIFIER

AIR SUPPLY

Figure 5.-Photosorting system diagram.

BARK REMOVAL

PHOTO-SORTER

LAMP -

+

PHOTO-CELL-, LENS \ 1

WOOD ã BARK

Figure ó.-Mechanical configuration of the photosorting system.

91
Table 5.-Effect of light leve1 on photosorting 5/8-inch aspen wood and bark chips

(In percent)

Product

Input

Accepts

Rejects

LIGHT LEVEL - 2.5 mW/cm

Bark Portion of Portion of Portion of

content total chips total wood total bark

10.6 100 100 100

1.4 63 70 8

26.2 37 30 92

LIGHT LEVEL - 3.5 mW/cm

Input 9.3 100 100 100

Accepts 2.3 79 86 1 9

Rejects 36.7 2 1 14 81,

LIGHT LEVEL - 4.5 mW/cm

Input 8.9 100 100 100

Accepts 3.3 88 93 32

Rejects 48.5 1 2 7 68

LIGHT LEVEL - 5.5 mW/cm

Input 9.7 100 100 100

Accepts 5.1 91 96 48

Rejects 56.4 9 4 52

A typical urban wood waste recovery plant includes a number of processing steps

such as crushing, washing, hogging, screening, and magnetic separation (fig. 7). How

and where would a vacuum-airlift segregator be incorporated ínto such a recovery

plant? A three-stage segregator is one possibility (fig. 8). It would be one of the last

stages in the total material flow through the plant (fig. 9) resulting in at least two

fractions of wood chips-high-quality chips and fuelwood chips. Cost to insta11 a

20-ton-per-hour vacuum-airlift segregation system (fig. 8) into an already existing plant

has been estimated to be $175,000. The processing costs would be less than $1 per

input ton. Total connected horsepower is 205.

SUMMARY

Three new systems have been developed for upgrading the quality of whole-tree

and wood residue chips-steaming-compression debarking, vacuum-airlift segregation,

and photosorting. A combined system using steaming-compression debarking and

vacuum-airlift segregation has proved to be the most economical for maximum clean

fiber recovery and the vacuum-airlift segregation system can easily be incorporated

into present waste wood recovery, systems. Installation of a 20-ton-per-hour system

is estimated to cost $175,000. With the large number of energy products, chemicals,

and fiber products that are potentially available from waste wood, we are at the doorstep of converting it from a disposal problem to a valuable resource.

92
WOOD

YARO 

-

-

HOG - SCREEN - FINES

WASH -

,

I

r l

METAL

I I

Figure 7.-Typical urban waste wood recycling plant.

DISCHARGE

VALVE

FUEL CHIPS

CONVEYOR

HEAVY REJECTS

CONVEYOR

Figure 8.-A three-stage vacuum-airlift segregator for urban waste wood recovery.

93
CHIPS - FINES

,-

WOOD a

HOG

YARD WASH -I

I 4

OVERSIZE

flMETAL

HEAVY

METAL NONMETALLIC

REJECTS

Figure 9.-Proposed urban waste wood recycling plant including vacuum-airhft segregation (VAS).

+

MAGNET IC

SEPARATOR

LITERATURE CITED

Arola, Rodger A., J. A. Sturos, and J. A. Mattson

1976. Research in quality improvement of whole-tree chips. TAPPI 59(7):66-70.

Carr, Wayne F.

1978. Urban wood waste in the United States. Unpubl. rep. to the For. Prod. Lab., U.S.

Dep. Agrie. For. Serv., Madison, Wis.

Mattson, James A.

1975. Debarking chips from whole trees in the Lake States. U.S. Dep. Agrie. For. Serv.,

Res. Pap. NC-115,9 p. North Cent. For. Exp. Stn., St. Paul, Minn.

Ratcliffe, Pete

1976. Ful1 forest residual and unwanted trees as fuel to replace or supplement existing

fuel. Zn Energy and the wood products industry. Meeting sponsored by the FPRS.

Proc. P-76-14:53-55.

Sturos, John A.

1978. Bark, foliage, and grit removal from whole-tree chips-results and economics. TAPPI

Pulping Conf. Proc. p. 121-134. [Atlanta, Ga.]

Sturos, John A., and D. B. Brumm

1978. Segregating wood and bark chips by photosorting. U.S. Dep. Agrie. For. Serv., Res.

Pap. NC-164,6 p. North Cent. For. Exp. Stn., St. Paul, Minn.

Sturos, John A., and John L. Marvin

1978. A process for removing bark, foliage and grit from southern pine whole-tree chips.

Zn Complete-tree utilization of southern pine. Symp. Proc., p. 277-294. [New

Orleans, La., April 17-19.1 USFS/FPRS/IUFRO.

Wawer, Adolf, and M’N. Misra

1977. Whole-tree chips compression debarking-St. Anne Pilot Plant Study. Paper presented at the 63rd Annu. meet. of the Tech. Sec., CPPA [Montreal, P.Q., Canada,

Feb. l-4.1

94
IMPORTANCE OF WOOD AS AN URBAN ENERGY SOURCE

James W. McMinn’

Abstract.-The paper reviews (1) theoretical limits to wood supplies,

(2) characteristics of wood as a fuel source, (3) difficulties in predicting energy consumption and fuel prices, and (4) the outlook for

wood-energy development. Woody biomass is likely to provide less

than 10 percent of urban energy, and its use will be in small-scale,

decentralized systems. Small towns will derive the greatest benefits

from primary biomass, whereas use of urban waste wood will probably be unrelated to city size.

Energy consumption in the United States has increased almost twentyfold in the

last century. During the same period, the amount of energy the Nation derives from

wood has decreased to a little more than a third of its former contribution. At one

time, 75 percent of our energy was supplied by wood, whereas it presently supplies

well below 5 percent (Curtis 1978). A large proportion of the national energy supply.

will probably never again be derived from wood, but use of wood for energy could be

substantial in certain areas. This presentation covers (1) theoretical limits to wood

supplies, (2) some advantages and disadvantages of wood as an energy source, (3) some

complexities inherent in projecting fuel use and prices, and (4) future possibilities for

wood-energy development.

WOODY BIOMASS SUPPLY

In determining quantities available for conversion into energy, annual growth

rather than the total wood volume in the forest must be considered. Professional

foresters routinely base estimates of possible use on growth, but individuals not

involved in renewable-resource management often fail to recognize the distinction

between mining an inventory and harvesting growth. Estimates of total growth over a

large geographic area are not sufficiently precise for an individual or firm that is seriously considering wood as an alternate fuel. However, such estimates are valuable to

planners and policymakers for placing upper limits on wood harvests for al1 purposes.

Some of the more reliable estimates follow.

Worldwide, plants store about six times as much energy in biomass as humans use

each year (Dubos 1976). More than half of this biomass is produced in forests that

receive no more than custodia1 management. Less than one-tenth of the annual biomass accumulation occurs on cultivated areas, so their current energy potential is quite

low when energy inputs are accounted for.

In contrast to the world situation, annual biomass increment in the continental

United States is equivalent to only about half the energy consumed (Burwell 1978).

Furthermore, this biomass includes food, fiber, and feed grains as well as forest and

crep residues and surplus increment. Woody biomass growth on our commercial

‘Project Leader, Wood Energy Relationships, U.S. Departn;ent of Agriculture Forest Service,

Southeastern Forest Experiment Station, Athens, Georgia.

95
forestland is equivalent to somewhere between 10 and 15 percent of our annual energy

consumption. The United States ratio of biornass accumulation to energy use represents a prodigious rate of consumption, rather than a low leve1 of productivity.

The foregoing figures do not mean that wood fuels are impractical or insignificant.

They do mean that on a national or regional scale there are definite limits to the role

wood can play in supplying energy for urban areas.

In many places, wood can be a very practica1 source of energy. One plant in France

has generated electricity from wood-fired boilers for over 50 years (Jagles 1978). In

Maine, Vermont, and New Hampshire, 18 percent of all households use wood as their

primary heating source, and citizens of Burlington, Vermont, have approved a $40-

million bond issue for a 50-megawatt wood-fired p&ower plant (Anon. 1979). Burlington

currently has a 30-megawatt plant supplied by three IO-megawatt boilers; one of those

boilers has operated successfully for severa1 months on wood. A recent study indicates

that a 25megawatt wood-fired plant would probably be feasible in north-central Minnesota (Rose and Olson 1979). The wood-products industry currently derives over

30 percent of its energy from waste wood.

The pertinent question, then, is not whether wood energy is feasible, but where

and on what scale. Approximately half of the biomass growth on our commercial

forestland occurs in the southeastern quarter of the country (Burwell 1978), so it is

probable that substantial development opportunities exist here. The Southeastern

Forest Experiment Station’s wood-energy research unit at Athens, Georgia, is developing procedures to identify communities with high development potential and to

determine the degree to which development in one community will constrain development in others. We are focusing on physical supply and will be dealing with severa1

supply variables, beginning with sawmill residues presently generated and working

ultimately with the long-term productive capacity of the land. We do not include

urban wood waste, primarily because reliable inventory data are not available. Urban

areas may produce waste wood at a rate equivalent to 23 percent of the growth on

commercial forestland (Burwell 1978). If so, this source of energy would be significant

in many communities.

WOOD AS A FUEL SOURCE

Since 1974 wood-energy development has been surprisingly slow in light of the

interest and available technology. Some of the disadvantages of wood as a fuel source

explain the limited development.

Woody biomass is quite variable, and its energy is less concentrated than that in

other common fuels (Jagles 1978). It is therefore difficult to handle and costly to

transport, and it requires a relatively large amount of storage space for a given burner

output . The most difficult problem, however , is water content. The energy equivalent

of green wood is less than half the 8,500 BTU per Pound of dry wood.

Biomass is one of severa1 potential energy sources derived from the sun. Solar

energy in any form has broad appeal because, in theory, it is freely available and the

worst forms of pollution are not associated with its use. However, practica1 application

of solar energy requires capture and storage. Plants perform both functions. They capture less than 5 percent of total insolation, but they do so at low cost. Woody plants

96
’ are particularly attractive as energy sources because, unlike annual plants, they cm

accumulate energy for many years before harvest. Large quantities of fuel, therefore,

can be harvested per unit asea. Burwell(1978) has shown that ratios of energy output/

input can be relatively high (35-40/1) for unmanaged forestland because the only

input required is for harvesting.

Some investigators have concluded that the net effect of the above advantages and

disadvantages will lead to small-scale, decentralized conversion of woody biomass to

energy (Dubos 1976; Burwell 1978). This conclusion seems to imply that opportunities for wood-energy development will be more numerous for small towns than for

large urban areas. However, urban waste wood differs from other woody biomass in

two important respects: (1) some of it is at least partially dry, and (2) it is already -‘”

centralized to a degree. Some of the costs associated with wood-fuel transportation

and processing are, therefore, borne by other products.

ENERGY COST COMPARISONS

There are many uncertainties associated with predicting the relative costs of wood

and alternate energy sources. In the absence of operational experience, costs of harvesting, concentrating, and/or separating types of material can be only roughly estimated. Furthermore, changes in energy supplies and costs can be predicted only with

great uncettainty.

On the basis of Carter’s (1974) discussion, the uncertainties may be grouped under

the following categories:

Waste trimming.-Decades of inexpensive energy have led to waste that conservation efforts can reduce at little or no cost. More.leeway probably exists in space

heating and lighting than in industrial processes.

New technoZogy.-Notable examples of energy-saving technology are new processes for manufacturing steel and aluminum, but advances are taking place in many

fields and at al1 scales of use.

Implementation of existing technology.-No new technology is needed for carpooling, widespread use of mass transit, or for effkient recycling of many energyexpensive materials. As energy costs rise, greater economic incentives should forte

implementation of known technologies.

Labor-energy substitution.-From World War II until the 1973-74 oil embargo,

energy costs decreased and labor costs increased. The benefit of energy substitution

became axipmatic. With energy costs increasing faster than labor costs, that axiom no

longer holds. We can now expect a gradual substitution of labor for energy.

Schipper and Lichtenberg (1976) have demonstrated how some of the above

factors influente Sweden’s rate of energy consumption compared to that in the

United States. They found the main contributing factors to be “. . . smaller automo-

%iles, more use of mass transit , more insulation and tighter construction, more efficient

industrial processes, and the use of cogeneration and district heating.” Of these factors,

only district heating varies’ substantially from near-term United States capabilities; in

Sweden, waste heat from power stations is distributed throughout rather large districts

for space heating. A high standard of living is commonly thought to depend on high

97
energy consumption. Swedish energy consumption per unit of Gross National Product

is only 68 percent of that in the United States, and the two countries have generally

comparable standards of living. A policy-study group here in the United States has

concluded that it will be “. . . technically feasible in 2010 to use roughly a total

amount of energy as low as that used today and still provide a higher leve1 of amenities, even with total population increasing 35 percent” (Demand and Conservation

Panel of CONAES 1978).

FUTURE OUTLOOK

Most authors dealing with energy agree that use of oil and natural gas will decline

and that in the short term no single large energy source will replace them. The variety

and character of alternate energy sources will probably forte a trend toward more

individually tailored systems, rather than uniform, energy-wasteful systems (Jagles

1978). This environment will be conducive to wood-energy development. It could also

lead to depletion of wood supplies and increased fuel transportation costs for local

areas.

For the longer term, Hayes (1979) builds a logical case for the likely development

of coa1 as the single large energy source in the United States. He points out that public

opposition, increasing capital costs, and decreasing growth in electrical energy use are

recognized as obstacles to nuclear development, but the availability of uranium is a

more significant restriction than is generally realized. If coal use increases rapidly, the

combustion of wood with coa1 is potentially significant for maintaining sulfur emissions at acceptable levels (Inman 1977).

Energy plantations can have a favorable energy output/input ratio and could fulfill

some of our long-term energy needs (Inman 1977). However, they have definite limitations and are no panacea for energy problems. One of the greatest fallacies associated

with energy plantations is the emphasis on so-called fast-growing species. Plant growth

is a result of genetic capacity and environmental conditions. The only difference

between fast-growing species and slow-growing species is that the former have the

capacity to respond to a rich environment and the latter do not. Therefore, fast-growing

species do not grow fast on marginal land. Phenomenal production is possible through

fertihzation and irrigation of marginal lands, but these operations are energy-expensive.

Current research efforts are comparing outputs with inputs for such situations. Cities

close to marginal lands have a unique opportunity to coordinate waste management

and energy production by using ash and sewage as soil amendments to increase production on biomass plantations.

CONCLUSIONS

Wood can be expected to supply less than 10 percent of the energy for urban

areas, but its contribution could be substantially greater in selected communities.

Generalizations about the relative costs of wood and other fuels are extremely

difficult to make.

Most systems for conversion of wood to energy will probably be small, decentralized, and tailored to local conditions.

98
Because of high transportation costs, small towns are most likely to use. forestgrown wood for energy.

Since urban waste wood must be concentrated for disposal even if it is not used,

transportation need not be considered in estimating cost of converting this wood to

energy.

Biomass plantations will probably play a limited role in energy supply, but some

urban areas have unique opportunities to develop innovative energy plantation systems.

LITERATURE CITED

Anonymous

1979. Glowing future for forest power: New England gets fiied up over an ancient fuel.

Time 113(4):59.

BurwelI, C. C.

1978. Solar biomass energy: An overview of U.S. potential. Science 199:1041-1048.

Carter, A. P.

1974. Applications of input-output analysis to energy production. Science 184:325-329.

Curtis, A. B., JI.

1978. Wood for energy: an overview. For. Prod. Util. Bull., 4 p. U.S. Dep. Agrie. For. Serv.,

Southeast. Area, State and Priv. For., Atlanta, Ga.

Demand and Conservation Panel of the Committee on Nuclear and Alternative Energy Systems

1978. U.S. energy demand: Some low energy futures. Science 200:142-152.

Dubos, R.

1976. Symbiosis between the earth and humankmd. Science 193:459-462.

Hayes, E. T.

1979. Energy resources available to the United States, 1985 to 2000. Science 203:233-

239.

Inman, R. E.

1971. Silvicultura1 biomass farms. Vol. 1: Summary. METREK Div., McLean, Va. Mitre

Corp. Mitre Tech. Rep. 7347,62 p.

Jagles, R.

1978. Forest biomass for the competitive consumer. In Energy and the southem forest,

p. 108-120. Proc. 27th Annu. For. Symp., La. State Univ., Baton Rouge.

Rose, D. W., and K. P. Olson

1979. Wood-an economical and reliable fuel for generating electricity in northem Minnesota. J. For. 77:88-90.

Schipper, L., and A. L. Lichtenberg

1976. Efficient energy use and well-being: the Swedish example. Science 194:1001-1013.

99
RECOVERY OF ENERGY FROM SOLID WASTEAN ALTERNATIVE TO LANDFILL DISPOSAL

Gloria A. Millsr

Absn-uct.-There are many solid waste recovery techniques from

which communities may choose. The technology described here is

known generally as mass combustion in waterwall boilers. A facility

using this technology takes ah kinds of residential, commercial, and

nonproblem industrial solid wastes and processes them into usable

energy and marketable materials. This combustion process performs

extremely well, with better than 96 percent burnout of combustible

matter and a volume reduction of 95 percent.

Pinellas County, Florida, located on the west coast between the Gulf of Mexico

and Tampa Bay, is primarily an urban area, having as its two largest municipalities the

cities of St. Petersburg and Clearwater; in fact, it is the most densely populated county

in the State. Pinellas County faces a problem encountered by many other urban areas:

how to dispose of its solid waste in an environmentally acceptable manner at a time

when disposal costs are rising and landfill space is diminishing.

The county took a number of steps to reduce its waste collection costs and to

improve productivity. It switched to hydraulically operated packer trucks and oneman collection vehicles. A variety of factors, including the limited future life of its

largest landfill, led to a search for an alternative to that method of disposal.

An act of the Florida legislature gave the Board of County Commissioners the

responsibility for the disposal of al1 solid waste throughout Pinellas County. The

same legislative act established the Solid Waste Technical Management Committee

(TMC). Members are technically qualified representatives from designated municipalities. The TMC has been instrumental in providing guidance to the Board of County

Commissioners in the development of a solid waste program for the county.

The program began with the selection of Henningson, Durham, and Richardson

(HDR) as the county’s engineering consultant and William R. Hough & Co. as the

county’s financia1 consultant. Both firms are nationally recognized experts in developing programs for solid waste disposal.

HDR conducted a feasibility study to determine how much and what kinds of

wastes existed in the county, what technological alternatives existed for the disposal

of those wastes, what markets existed for the energy and materials recoverable from

the waste stream, and what sites were available for the location of a resource recovery

facility. The results of the study indicated that resource recovery was feasible, and a

plan for the implementation of a resource recovery system was developed.

The plan had three major objectives. The county wanted a system that was

(1) technically sound, (2) environmentally acceptable, and (3) economically acceptI

‘Marketing Engineer, Solid Waste Systems, UOP, Inc., Des Plaines, Illinois 60016.

100
able. Private firms were invited to indicate their interest in contracting for the disposal

of 12,000 tons per week of the county’s waste. Following an initial prequalification

process, seven of the largest and most experienced companies in the solid waste business were invited to submit proposals for a total resource recovery system. The six

proposals actually received were subjected to a detailed evaluation that included the

use of computers to process cost data and provide sensitivity analyses. An extensive

description of this Request for Proposal (RFP) process can be found in an article by

Mr. D. F. Acenbrack, Director of Solid Waste Management for Pinellas County.’ The

result of the evaluation was the selection by the County Commission of the proposal

received from UOP, Inc.

UOP, formerly Universal Oil Products Company, is an international high-technology firm with more than 60 years of experience in commercializing new technology,

with emphasis on energy and the environment. In addition to resource recovery, UOP

is involved in petroleum refining, chemicals and petrochemicals production, water

purification, air pollution control, minerals processing, process engineering, and construction and manufacture of high-technology products.

The technology to be utilized in the Pinellas County resource recovery facihty,

which will be designed, constructed, and operated by UOP, is in the category known

generally as mass combustion in waterwall boilers. UOP has a long-term agreement

with the Josef Martin Company of Munich, West Germany, to market their extensive

combustion technology ín the U.S. and elsewhere.

The facility proposed for Pinellas County, and shown in the artist’s rendering

(fig. 1), will contain two combustion trains and will accept al1 kinds of residential,

commercial, and nonproblem industrial wastes and process them into usable energy

and marketable materials. As there are presently no suitable energy customers in the

immediate vicinity of the facility site, the sole energy product will be electricity, which

will be purchased by a public utility, the Orlando Utilities Commission.

Figure 2, a simplified schematic drawing, shows how the facihty works. Collection

vehicles, after being weighed at the entrance, drive into the processing building where

they unload directly into a large receiving pit . Once unloaded, the trucks exit from the

processing building and are quickly on their way.

Except for bulky wastes, the unsorted refuse is picked up by overhead cranes and

transferred to the furnace-feed hoppers. Bulky refuse, including tree trunks and furniture, is first reduced in size, then processed with normal waste materials. The size

reduction is accomplished with a shear-type device to get these larger items down to

about a 1-foot dimension.

Part of the air needed for the combustion process is drawn from the area above

the refuse receiving pit, which accomplishes two things. First, it creates a slight negative pressure, which prevents dust and odor from escaping to the outside; second, it

draws airborne bacteria and dust from the pit area into the furnace where any bacteria

are destroyed. Personnel working in the pit area are thus supplied continually with

fresh, clean air.

‘Acenbrack, D. F. 1978. Tools and team expedite resource recovery project. Public Works

Mag. (Oct.)

101
Figure l.-Pinellas County resource recovery facility.

102
Once loaded into the feed hopper, the refuse passes down through a waterjacketed feed chute from which it is metered onto the stoker grate by means of hydraulically operated feeder rams. The Martin reverse-reciprocating stoker is one of the features that make this resource recovery system unique (fig. 3).

k4oving ocsra l3wa

Fixed Grate Bara

Figure 3.-Martin reverse reciprocating stoker.

As can be seen in the schematic drawing, the Martin reverse-reciprocating stoker is

unlike conventional stoker designs. It is inclined downward toward the discharge end

and is divided alternately into fmed and moving rows of grate bars. The moving grates

push upward against the natural downward gravitational movement of the refuse. This

movement agitates the burning refuse to form an even depth over the fuel bed. Burning

refuse is pushed back underneath the incoming raw refuse to achieve continuous drying, volatilization, ignition, and burning. The result of this unique agitation is a uniform burnout of better than 96 percent of the combustible matter.

A series of plenum chambers underneath the stoker grate admits combustion air

in volumes controlled to suit the combustion conditions of each burning zone. With

the use of preheated combustion air, thorough bumout is achieved even when processing wastes high in moisture content. No manual cleaning of the undergrate plenums is

required because an automatic siftings-removal system periodically sweeps the plenums.

103
A series of overfire air nozzles, located in the front and back of the furnace-throat

area, provides maximum flame turbulence and prevents the stratification of gasses.

The speed of the residue roller is independently controllable to regulate the depth

of the fuel and ash layer on the grate. The ability to control the feed rate of refuse

into the furnace, to control the agitation and depth of the refuse bed on the stoker,

and to control the volume and distribution of the combustion air is a key to the

unmatched performance of this combustion system.

The grate bars themselves are also unique. A close-up view of the grate bars shows

the 2-mm airgaps at the heads of the bars (fig. 4). These airgaps represent only 2 percent of the total-grate surface area. High-pressure combustion air passing through these

gaps causes intense burning, even of dense materials like carpeting, and minimizes

sifting of ash through the airgaps. The precision-ground grate bars are cast of durable

chrome-alloy steel for long operational life.

Figure 4.-Martin grate bars.

A furnace interior shows the modular approach to unit design. The stoker consists

of multiple longitudinal grate sections across the width of the furnace. Larger units

contain severa1 grate sections, while smaller units contain fewer. The boiler furnace is

constrticted of gas-tight, continuously welded waterwalls down to the grate surface.

These waterwalls are coated with refractory material above the grate surface to a height

of about 20 feet. The refractory has good heat-transfer characteristics and prevents

corrosion in the lower section of the furnace where high temperatures are encountered. The large volume of the furnace above the throat area is designed for low gas

velocities to avoid high fly-ash carryover to the gas-cleaning equipment and excessive

slagging in the boiler .

104
The boiler, which is integrated with the furnace, is also specifically designed for

refuse combustion. Boiler tubes are arranged in widely spaced rows, not staggered, to

permit effective cleaning by sootblowers and to prevent plugging of tube rows. The

multipass design of the boilers reduces the particulate load into the gas-cleaning equipment as the reversa1 of the gas flow at the bottom of each pass causes particulates to

drop out of the gas stream. The superheater is strategically located away from the

radiant furnace zone in an open pass. This location requires a larger superheater

surface area but has resulted in a recorded operating life of more than 40,000 hours

without tube replacement. The steaming conditions at the Pinellas facility will be

615 psig., 750’F.

Combustion gases from the boiler pass through an electrostatic precipitator for

removal of particulates before the gases are released to the atmosphere through the

stack. This equipment is also designed to accommodate fly ash. The precipitators proposed for this facility contain three electrical fields, which wiU keep emissions below

current standards. Provision has been made in the design, however, for the installation

of a fourth field in the event that emission requirements become more stringent in the

future .

The steam produced in the boiler is used to drive a turbine-generator to produce

electricity for sale. A portion of the steam is also used in-house to drive some of the

equipment . The whole operation is monitored from an air-conditioned central control

room.

Conceptually, the UOP materials recovery system begins on the Martin stoker

grate where combustible material that might hamper recovery efforts is completely

burned out . The precise distribution of underfire combustion air prevents combustion

“hot spots” that could damage or destroy recoverable materials.

The combustion residue is discharged from the furnace into residue dischargers.

Here, the residue is quenched in water which also serves as an air seal to pregent

leakage of uncontrolled combustion air into the fumace. The residue is cooled below

212°F by the quench water and is pushed, by a discharge ram, up into a draining and

drying chamber. The discharged residue contains just enough moisture to control

dust, which permits the use of ordinary conveyors to transport the residue to the

materials recovery system.

Materials recovery, as seen in the simplified schematic (fig. 5) is essentially a

series of sizing and separation processes to separate the metalhc from the nonmetallic

residue and to separate the ferrous from the nonferrous metals.

Bulky ferrous and nonferrous scrap is the first item separated for sale. A rotating

trommel screen divides the remaining stream into two fractions, one larger than

2 inches and the other smaller than 2 inches. The plus-2-inch fraction, which is primarily “tin” cans, will pass a magnet for ferrous removal. This ferrous material is then

shredded to remove surface contamination and to increase the density of the metal

prior to sale.

Material less than 2 inches will also pass a magnet where small bits of ferrous metal

will be removed. The remainder will be primanly aluminum, heavy nonferrous metals,

glass, ash, and other inorganic materials.

105
Figure 5.-UOP materials recovery system.

Additional screening will subdivide the stream into toarse and fine fractions,

remoilng most of the glass, ceramics, dirt, and other nonmetallic particles. Aluminum

and other nonferrous metals will be recovered from each fraction by heavy-media

density separation. Because of the difference in specific gravity, aluminum will float,

while zinc and copper alloys sink. Small aluminum particles will be crushed into recoverable flakes.

The crushed glass, ceramics, dirt , and other nonmetallic particles removed during

this sizing process may be admixed with the precipitator fly ash, which is collected

separately. This aggregate material may be sold and used as supplemental aggregate in

asphalt paving mix, in roadbed construction, as landfill cover, and as fil1 for land

reclamation.

After recovery of metals and aggregate material, the remaining stream will consist

primarily of larger stones, bricks, and similar noncombustible and nonmetallic objects.

This stream will generally be the only residue. Although it may have value as clean fill,

it will usually be disposed of in a landfill. This process residue will represent about 1.5

percent, by weight of the incoming raw solid waste.

106
The Pinellas County facility will operate 24 hours a day, 7 days a week. Each of

the two combustion units is scheduled for shutdown for inspection and maintenance

twice a year. The plant’s 50 MW turbine-generator is scheduled for shutdown and

inspection every 3 years.

To minimize use of potable water, a precious commodity in Florida, effluent from

a tertiary water treatment plant will be used in the cooling towers of the resource

recovery facihty.

The resource recovery plant will be centrally located within the county for service

to al1 county communities. UOP has allocated funds for landscaping and site beautification so that the facihty will be attractive.

Applications for required Federal and State permits covering air emissions and

powerplant siting have already been filed. To bring the project to fruition, a number of

contracts must be negotiated, including contracts for the construction and operation

of the facility and for the transmission and sale of energy, al1 of which must be completed before the bonds for the plant can be sold. After reviewing both public and

private ownership options, the county has decided that it prefers to be the owner of

the facility .

Once the bonds are sold, the county will notify UOP to proceed with construction.

Thirty-two months later, the Pinellas County resource recovery facility should be

ready for startup. Raw solid waste will then be converted into clean energy and

materials.

Pinellas County is far ahead of most other urban communities with its solid waste

program. By working together, its citizens and officials are turning their solid waste

problem into a solid solution.

107

109
TOPIC III

PLANNING

ABSTRACTS

WHITMER

Legal and Environmental Issues Surrounding Urban Waste Wood.-Materials handling to minimize pollution, litter, and complaints, along with careful attention to

matters of ownership and contracts, must be addressed early in the quest for utilization of wasted resources. Identification of these considerations serves to improve

a project’s chance for successful implementation.

LEMPICKI

Coordinating Producers and Consumers of Urban Wood Residues.-Sources of

urban wood waste are both numerous and varied, so flnding ways to use this waste

can be a complex problem. This paper deals with the New Jersey Bureau of Forest

Management’s program concerning wood waste generated from the secondary

processing of wood, locating the manufacturers, estimating their volumes of wood

waste, and marketing these materials. The wood waste from secondary wood processors is a collectively large source of material often found in urban areas.

PARDO

Urban Waste Wood: The Challenge and the Future.-The proceedings of this conference present a valuable guide to what can be done to convert urban waste

wood problems into utilization opportunities. The information needs to be communicated as widely as possible. Federal dollars are in short supply for new programs, but if these programs are presented as proven ways to save money and to

lower costs, Congress may be willing to buy what you are selling.

110
LEGAL AND ENVIRONMENTAL ISSUES

SURROUNDING URBAN WASTE WOOD

George L. Whitmer’

Abstruct.-Materials handling to minimize pollution, litter, and

complaints, along with careful attention to matters of ownership

and contracts, must be addressed early in the quest for utilization of

wasted resources. Identification of these considerations serves to improve a project’s chance for successful implementation.

INTRODUCTION

Many aspects of waste wood management are identical to reuse or disposal of

municipal solid waste. In fact, one might envision that processed garbage or baled

wastepaper might compete with wood waste in the marketplace. The purpose of this

presentation is to cal1 attention to severa1 technical and nontechnical considerations

which are shared by waste utilization programs.

Legal and environmental issues cannot easily be separated, for failure to recognize

one aspect would tend to have a great impact on the other. One consideration in particular, ownership, has the potential to influente a program’s financia1 risk.

Waste wood occurring naturally in a forested area becomes a part of the ecosystem.

It not only presents no environmental problems other than fire hazard but is utilized

by insects and forest animals and recycled through the forest itself. Waste wood

occurring in an urban area presents an entirely different set of circumstances. In most

cases, waste cannot be allowed to remain where it occurs. It requires transportation to

another site to be disposed of or to receive further processing. Stumps, limbs, or

demolition debris present an operational problem at disposal sites. Most waste wood in

urban areas is not the result of natural occurrences but results from land clearing, construction and demolition, and other activities.

Nature provides a solution for waste wood in the natural environment. It is not an

instant solution, but we cannot argue with the results; however, once we alter natural

processes, it is then up to us to provide solutions for the problems we create.

Waste wood presents a handling problem at any land disposal site. In Georgia, the

Environmental Protection Division (EPD) recognizes two types of approved disposal

sites: the sanitary landfil for putrescible (rapidly decomposable) waste, which requires

daily cover, and the landfill for nonputrescible (demolition debris, wood waste, etc.)

waste, which requires monthly cover. Waste wood normally goes to landfills since it

does not decompose rapidly. It presents a handling problem in either type of site

ihough. Much of it will not compact (tree stumps, logs) and presents a hazard to the

equipment operator when mixed with other refuse. A large stump or log is capable of

upsetting a piece of landfrll equipment. This type of material also takes up valuable

‘Environmental Specialist, Georgia Environmental Protection Division, hlunicipal Solid

Waste Control Program, 3420 Whipple Street, Hapeville, Georgia 30354,

111
space in the landfnl because it does not compact well. More cover material is required

to cover logs, stumps, and limbs because the air spaces around them must be filled.

With the rising cost of land and suitable cover material, these important factors will

become even more critical.

Site supervisors have the authority under State law to refuse any waste at a site

where acceptance of the material might cause a problem. This stipulation is for the

purpose of protecting site operators from hazardous materials. It may also be applicable to waste wood, especially logs, if the supervisor feels that his site is filling up too

rapidly or that the wood might constitute an operational problem orbe hazardous to

his personnel or equipment .

It becomes clear that, while protecting the site operator from hazards and preventing

overutilization of site space, waste wood that is refused admittance to a site continues

to be a disposal problem.

Control over the burning of waste wood is the responsibility of the Air Protection

Branch of the EPD, along with local fire and forestry officials. Permits may be issued,

under certain circumstances, for existing conical (teepee) burners, land-clearing debris,

and tree and limb debris resulting from ice or wind storms. In many cases, permits for

the burning of land-clearing and storm debris are a local option. However, in counties

with a population greater than 65,000, burning of land-clearing and storm debris is

prohibited unless adequate disposal facilities are not reasonably available. Burning is

permitted in this case, except that no open burning of more than 100 cubic yards per

day of land-clearing debris is permitted unless the person performing the burning has

first given 2 days’ notice of the time and place of the burning to the Director, EPD.

Air curtain destructors may be permitted for burning of brush and small limbs.

This practice has in some cases led to air pollution problems due to burning of unauthorized waste.

ENVIRONMENTAL CONSIDERATIONS

The air in urban areas already contains high quantities of air pollution from

vehicle emissions, industry, and coal-fired boilers. Burning of waste wood adds unnecessarily to the already overburdened air in major urban areas and has led to the tightening of restrictions placed on obtaining a permit for open burning of land-clearing

and storm debris. Accidental burning of waste wood through acts of nature or carelessness also contributes heavily fo the urban air pollution problem. Accidental burning

or deliberately set illegal waste wood fires may become a problem following a wind or

ice storm. Variances of open burning restrictions may be issued by regulatory agencies.

Waste wood also has the potential for causing water pollution. This water pollution may take the form of floating or partially submerged debris in rivers, streams, and

lakes. In this form, it poses a hazard to persons skiing, swimming, or iishing in recreational areas. Water pollution may also take the form of tannic acid leaching into

bodies of water from certain types of waste wood. Tannic acid may not be an environmental problem as it is a natural phenomenon in forested areas; however, tannic acid

would be a problem if leaching from a tremendous amount of wood waste were to

occur in a small body of water. Also, as tannic acid can cause darkening of water, it

112
may have a negative impact, esthetically, on bodies of water used for recreational

purposes.

With the increased cost of natural gas and fossil fuels, wood is becomhg an

attractive alternative. Wood chips are being used by many industries as boiler fuel to

generate process steam. Any industry switching from natural gas or fossil fuels to wood

chips or a combination of fossil fuels and wood chips must advise the State Air Protection Branch of the change. Very strict emissíon controls are required; it is possible

that the emissíon control equipment may have to be altered, or the permit for operation of the boiler may have to be amended. A sígnificant increase in the amounts of

fly ash, sulfur dioxide, other particulates, or smoke opacíty would require a change in

the emissíon control equipment.

The pulp and paper industry ís utilízing much wood waste as fuel. One particleboard company in South Georgia utilizes sander dust as fuel, creating an ash which

must be disposed of. Sander dust used in the boilers creates anash slag; the boilers are

blown out four times a day, and there is one day a week for boiler cleaning. During

this day, a chemical is added to the boiler walls, hardening the slag so that it may be

chipped off. In these sander-dust burners, soft slag puddles at the bottom; all of the

slag and ash is presently landfilled.

Another company using a hogged fuel boiler had its ash analyzed for nutrient

content. The result was that it did not contain high enough percentages of minerals

to offset the hauling expense to a fertilizer company. Recovery of the ash material

from this plant would probably be economically feasible if a fertilizer plant were

located close by. This plant landfills its ash at the present time.

An Atlanta company that buys fly ash for use in fertilizer and cement purchases

the ash from coa1 but none from wood; the reason for this ís that coal fly ash ís generally consistent, while that from wood burning is extremely variable. Wood ash

varies from source to source, depending on equipment, mixture of fuels, type of

supplemental fuels, geographic location, mixture of softwoods and hardwoods, handling procedure, and types of environmental controls used. The company, however, is

very interested in the utilization of wood ash and is presently doing research on it.

If large quantitíes of wood chips, bark, or sawdust are stored outside, certain

problems could arise. As mentioned earlier, the leaching of water through this material

could cause tannic acid to enter the groundwater and, ultimately, nearby ponds or

streams. The storage area could be considered an eyesore by nearby residents who

might complain to local officials. Zoning regulations and locaI.nuisance ordinances

should be researched beforehand in order that problems of thís nature can be avoided.

The major enviromnental consideration in the transportation of waste wood is

litter. The Georgia solid waste law does not specifically require that trucks be covered,

but it does require that vehicles be loaded and moved in such a manner that contents

will not fa11 or spill, and ít states that vehicles be covered “when necessary” to prevent

blowing of material from the vehicle.

LEGAL CONSIDERATIONS

RCRA and the Georgia Solíd Waste Management Act do not specifically address

the ownership of waste. Waste handling is a local governmental trust in most cases, and

113
ordinances establishing ownership of waste are generally passed by the city or county.

Normally, this will not affect waste wood if it is a material of no fuel value and is

merely a disposal problem; however, when this waste material becomes a commodityhas a monetary value-then the legal problem of ownership comes into focus. Communities that have instituted curbside newspaper, glass, and aluminum can recycling prop;rams have had to deal with this problem. Residents would place their garbage at

cnrbside for pickup and disposal; at the same time, they would place bundled newspapers, bagged aluminum cans, and glass at the curbside for pickup and placement in

separate compartments of the garbage truck or in separate trucks for recycling. Problems developed when scavengers would precede the garbage truck and pick up the

recyclables for sale themselves. Local ordinances had to be passed providing that

anything placed at the curbside by the resident was the property of the City.

If a city were selling its waste wood to a mil1 for use as fuel in its boilers, this

wood would then be a commodity. An ordinance would be needed to prevent local

entrepreneurs from collecting and selling the waste wood fuel themselves and thus

preventing the city from collecting the revenues generated by it.

Military installations se11 their waste wood through their Defense Property Disposal

Offices. The military considers al1 waste as government property and has complete

ownership of it. Waste wood-wooden trates and boxes, pallets, land-clearing debris,

demolition and construction debris-is sold by the lot on a competitive bid or by the

truckload by retail sale. All waste wood has to be paid for before it leaves the military

installation.

In selecting a market for and obtaining a contract to buy or sell waste wood, a

number of elements must be taken into consideration. Most City and county governments in Georgia do not allow for contracting beyond a l-year limit or beyond a

current administration. This, of course, has made it almost impossible for cities and

counties to contract with recycling companies to take scrap material. Many scrap

companies would have to make an investment in the form of collection, transportation, or processing equipment to enter into such an agreement and would not be

interested in less than a 5-year contract. Exceptions are companies that already recycle

such materials as scrap metal, newspaper, corrugated board, and glass. They would

require no additional investment to enter short-term contracts. Contracting for any

type of waste to be used as a fuel generally requires extensive alteration or construction of boilers and conveying equipment and would require a long-term contract.

Subtitle D of RCRA, under requirements for approval of state solid waste plans,

requires al1 state plans to provide that local governments can no longer be prohibited

from entering into long-term contracts for the supply of solid waste to resource recovery facilities. This provision would pertain to wood waste which is to be used as a fuel.

In any contract, provisions should be made for the amounts of allowable contaminants in waste materials. There are strict requirements on contaminants and different

grades of scrap metal and waste paper; waste wood types also have this problem, as

anyone buying bark for use as fuel can attest. Sand is a major and unavoidable contaminant in shipments of bark; there should be an allowable leve1 which, if exceeded,

would cause a shipment to be rejected. It is amazing how much scrap metal and other

unwanted material tends to turn up in bark shipments.

114 /
Contracts should state insurance limits and which party is liable if damage to

equipment occurs from contaminated shipments. Metal in a shipment of bark could

cause damage to shredding equipment, or bark containing too much moisture might

cause boiler corrosion. Liability insurance for personal injuries should be stated in a

contract .

Method of payment should also be clearly stated. Military installations require

payment for any scrap before it leaves the installation. Other industries are allowed to

transport material to their plant, where it is weighed, and payment is then issued.

Some contractors buying ferrous metals or aluminum are allowed to transport mixed

loads of scrap to their plant, run it through a magnetic separator, and pay according to

the amounts of ferrous and nonferrous materials delivered. Payment should be specified as to load, ton, or cubic yard.

A contract should specify minimum and maximum volumes, particularly if the

waste material is to be used as a fuel. The industry buying the fuel has a minimum

volume that can be utilized in order to maintain operations. The contractor’s failure to

deliver the minimum volume could jeopardize plant operation. There may also be a

problem of receiving too much fuel at the industry if adequate storage area does not

exist.

Provisions should be made in the contract for downtime on the part of the fuel

user. Boilers and burners will have scheduled downtime for maintenance. During this

time, the contractor will still be generating waste wood fuel, and the contract should

stipulate where the fuel will go during these downtimes. The same is true for unscheduled maintenance or repair. Many plants have built-in redundancy so that they can

remain operating during unscheduled shutdown of the main boiler.

If the ash cannot be utilized, contractual arrangements must be made to dispose

of it. If the ash can be used in fertilizer or cement, then additional contracts will be

needed between the generator and the buyer; these contracts should specify minimum

and maximum volume, type of payment, number and type of contaminants allowed,

liability and insurance. The U.S. EPA is currently writing guidelines on the use and

disposal of ash; these guidelines also will have to be considered.

SOCIAL AND POLITICAL ASPECTS

Finally, there are certain social and political aspects that must be taken into

consideration with respect to waste wood or any other waste.

Local governments have the authority to issue business licenses and to control

zoning laws. Any industry changing from one type of fuel to a mixture of that fuel

and waste wood (or any other type of waste material) may encounter some opposition

from the local zoning board. Also, an industry wanting to locate in an industrial park

and burn a waste for fuel may find it more difficult to get zoning approval or a business license.

Whenever waste material is hauled, whether for fuel, recycling, or disposal, there

are going to be complaints. Care should be taken to provide that trucks are properly

covered to prevent littering. If possible, trucks should be routed to avoid use of residential streets, which will help prevent complaints about noise, dust, damage tr,

ll5
streets, and danger to children. If citizens feel that a facility is emitting too heavy a

smoke plume, it, as well as governmental regulatory agencies, will get complaints.

Citizens may also complain if they think water leaching through the waste material is

getting into nearby water.

A tremendous amount of waste wood occurs from ice storms, hurricanes, and

tornadoes. We have already discussed what this extra volume does to the capacity and

operation of disposal sites. Some contingency methods should be available to handle

this extra waste wood. Limb and tree shredders and chippers are good methods of

dealing with this situation. The resulting shredded material may then be used as compost or decorative mulch.

The subject of public relations has been left for last but not because it is least

important . It is imperative that any new procedure be preceded by an extensive public

relations campaign. If a facility is planning a switch from a conventional fuel to burning waste wood or any other waste, the citizens should know why. They should be

told that it will conserve natural resources, that emissions will continue to meet environmental standards, that it will contribute to the longevity of their disposal sites, and

that the operation will be clean. A properly informed public will be more apt to welcome the facility as a good neighbor. In fact, good public relations-backed up with a

good operation-may be a facility’s most valuable asset.

116
COORDINATING PRODUCERS AND CONSUMERS

OF URBAN WOOD RESIDUES

Edward A. Lempicki’

Abstract.-Sources of urban wood waste are botb numerous and

varied, so finding ways to use this waste can be a complex problem.

This paper deals with the New Jersey Bureau of Forest Management’s program concerning wood waste generated from the secondary processing of wood, locating tbe manufacturers, estimating

their volumes of wood waste, and marketing these materials. Tbe

wood waste from secondary wood processors is a collectively large

source of material often found in urban areas.

LOCATING MANUFACTURERS

Companies that use lumber to manufacture wood products often locate in or near

urban areas because they are near a large labor supply, are accessible for receiving and

shipping materials, and are near markets for their products. Consequently, the secondary processors of wood are concentrated, as are their wood wastes.

To locate and identify these wastes, one must first locate the manufacturers. If no

directories of these processors are available, one must be compiled. In most states, the

sources of information for such a directory include the Lumbermans National Redbook Service, Dun and Bradstreet listings, and state industrial directories.

A questionnaire can be used to update listings and gather more detailed information. It might include requests for information on the type of raw material used (such

as lumber, bolts, plywood), species of wood and amount of wood used annually,

.products manufactured, estimated amount of wood residue and the percentage used at

the plant , and the difficulty of disposing of wood residues.

The New Jersey Bureau of Forest Management constructed such a questionnaire

and mailed them to woodworking firms throughout the State (fig. 1). According to

the Bureau’s survey, there are approximately 1,500 wood-product-manufacturing

firms in New Jersey. The responses were organized into product categories, and the

location of each company was pinpointed on a State map to give an overall view of

area workload. It showed a great industry concentration in the highly populated northeastern section of the State and other clusters around smaller urbanized areas of the

State. A direct relationship between population density and location of secondary

wood-processing companies was evident. With this information gathered, companies

were contacted concerning materials generated as waste from product manufacturers.

ESTIMATING RESIDUE VOLUMES

Residues from the secondary manufacture of wood products fe11 into two broad

categories: dimensional waste such as rippings, cutoffs and rejects; and fine material

such as sawdust, shavings, and chips.

‘Utilization and Marketing Forester, New Jersey Bureau of Forest Management, CN 028,

Trenton, New Jersey 08625.

117
Company Name: Address:

Person to Contact: Phone.

1 . Please note the product(s) made (from wood):

2 . What form of wood raw materials do you use? Please check.

- Blanks __ Precut or Dimension - Post

Stock

Blocks, Cants or

__ Flitches __ Lumber __ Roundwood

- Composition Board -Moulding - Veneer

__ Fiberboard __ Piling __ Other

__ Hardboard __ Plywood (Please specify)

__ Particleboard __ Poles

3 . Approximately what quantity of the following species do you use? Please indicate by percentage.

- Ash - Soft Maple __ Balsam Fir

- Basswood - Sycamore __ Westem Fir

__ Beechwood __ Red Oak __ Eastern Hemlock

- Birch __ White Oak __ Southern Pine

-Cedar __ Walnut ___ Western Pine

__ Cherry -YellowPoplar - White Pine

- Hickory - Mixed Hardwoods _ _ Eastern Spruce

- Hard Maple __ Tropical Woods -Mixed Softwoods

Other (please specify)

4. Please indicate your annual requirement of wood, according to your methòd of measurement.

Board Feet Cords

Square Feet Tons

Linear Feet Other

5 . What residues are produced in your operation(s) that are currently going unused? Please

check.

~ Bark ~Cores - Sawdust -Rippings, Cutoffs

- Chips __ Excelsior -Shavings __ Wood Flour

- Other (Please specify)

6 . Annual Wood Residue Volume and Method of Disposal.

Wood Fines (sawdust, shavings, etc.) -cubic yards or tons

Dimensional Waste (ripping, cutoffs, etc.) -....-cubic yards or tons

Method of Disposal

7 . How many personnel are in your firm?

8 . Please check, if you desire a copy of this directory

9. Comments:

l Figure 1 .-Secondary wood-using industry survey.

The amount of waste produced depends on the product being manufactured, the

volume and quality of raw material used, and the efficiency of production. The range

in amount of waste can be wide-from less than 5 percent to more than 50 percent of

the raw material. In the manufacture of floor trusses, the waste might be about 5 percent of the volume’of raw material but 50 percent for wood shoe heels.

Collectively, the industry was having great difficulty with these waste materials.

Most of it was being contracted for landfill disposal at substantial cost to the producer.

118
An estimated 20 million cubic feet of this material were disposed of in this manner

annually. This is not only a costly burden but also a tremendous waste of a resource.

Specific information must be obtained on residue type, production, and availability. The only accurate way to obtain volume information is by measurement, but most

companies know the volume of residues produced over a period of time in general

terms-by a hopper, container, or truckload. Normally, wood fines and dimensional

waste from a particular producer must be categorized separately.

In the case of wood fines, the important factors concerning marketability are

species, grade, particle size, moisture content, quantity, and storage capacity. Samples

of the material should be collected and specifically identified in these terms for

future referente. Dimensional waste, rippings, cutoffs and product rejects are more

difficult to define accurately. Quite often a range of dimensional material is normally

generated. Basically, this material may be grouped into broad categories with average

sizes noted. Often only a portion can be marketed, so separate information must be

obtained for each category. Samples are required since this material is often difficult

to describe accurately.

MARKETS FOR RESIDUES

A particular residue must not only fit a specific use but must also be produced in

sufficient quantity to allow marketing on an economically sound basis. Hence, available markets must be investigated as thoroughly as the producers; information is needed

on material specifications, volume requirements, and the buyer’s shipping, receiving,

and storing facilities.

While markets for residues are as numerous and varied as the producers, the major

markets for dimensional waste include the shipping industry (for storing and bracing),

other secondary processors, landscapers and nurserymen (for stakes), and the residue

dealers and companies that use the wood fines in a variety of products.

There are wood-residue companies located in New Jersey that collect, store,

refine, package, and deliver sawdust, shavings, chips, and other forms of wood residues

to a multitude of markets. Sawdust, for instance, has a variety of applications; sweeping, absorbent and cleaning compounds, animal bedding, metal polishing, and wood

fines for plastic and rubber processing are just a few uses. The average residue dealer in

New Jersey handles about 8,000 tons of wood fines per year. On a cubic-foot basis,

this equals roughly 1.5 million cubic feet of material, or enough fines to fill 700 large

tractor-trailers. The Bureau has been working with these residue dealers and other

demand sources and has had substantial success in diverting material from landfills to

more productive uses.

I

Utilization possibilities exist not only for wood fines but also for rippings, cutoffs,

and product rejects. This kind of material is the common result of sizing and shaping

lumber for product manufacture. Through our visits, we found that one company’s

dimensional residues may well be acceptable as another manufacturer’s raw material.

Companies producing the same products generate residue types that are essentially the

same; however, those manufacturing entirely different products tend to create utilization possibilities. Experience has shown that most often a particular company’s entire

dimensional residue production cannot be recycled to another.manufacturer for reuse.

/

119
Usually, a portion of this material has potential-a particular cutoff-size range or al1

rippings larger than a specified minimum width. The important point is, however, that

data must be obtained for the entire range of dimensional residues generated.

SUMMARY

The wood-using industry has accepted the Wood Residue Utilization Program and

is cooperating well. The residues generated from product production come in many

different forms and can really be thought of as a resource, every bit as renewable as

trees themselves.

The problems and pitfalls of recycling wood residues are many. Raw material

sources must first be located; locating must be followed by an on-site survey, something which requires a great deal of time and effort. Actual samples of material from

specific sources are needed since use is usually rather specific, and wood residues,

especially those generated by wood-product manufacturers, are quite variable and

difficult to describe accurately. Also, the material seems more attractive to a potential

buyer if it can be seen and possibly tried for use.

Experience has shown that waste wood must really sell itself. One must first have

something that a potential buyer can use. Not only must it be acceptable for a specific

use or product, but it must also be available at the right price. Further, waste wood

involves a certain cost for storage, handling, and transport. Economics is ultimately the

deciding factor and most often the real incentive to both residue producer and user.

There is a wide range of uses for wood residues both inside and outside of the woodproducts industry, and most of this material need not be a burden.

120
URBAN WASTE WOOD: THE CHALLENGE AND THE FUTURE

Richard Pardo ’

Abstract.-The Proceedings of this Conference present a valuable

guide to what can be done to convert urban waste wood problems

into utilization opportunities. The information needs to be communicated as widely as possible. Federal dollars are in short supply for

new programs, but if these programs are presented as proven ways

to save money and to lower costs, Congress may be willing to buy

what you are selling.

This Conference has been a real learning experience for me, and 1 want to commend

the people who put the meeting together and each of the speakers for a job well done.

The Proceedings of the meeting will be a gold mine of valuable information and ideas

in an area that so far has gone almost unnoticed.

Let me begin with a few words about the Ameritan Forestry Association for those

of you who may not be familiar with AFA. We are neither a trade association nor a

professional society but are a citizen conservation organization. Membership is open to

anyone. We are perhaps best known for our monthly magazine “Ameritan Forests.”

Our primary role is conservation education: informing the public about the broad

spectrum of forest-land management opportunities and issues. We are communicators

at AFA, which is one reason why 1 am excited by what 1 have heard here at this conference. The information presented here is specific, practical, and tremendously useful.

Now it needs to be communicated.

1 Are we really talking about problems, or are we also talking about opportunities?

One nian’s problem can be another’s opportunity. Perhaps what we really have is a

problem of communication-communication between the person with the waste wood

and the one for whom that wood may be an opportunity.

With that thought in mind 1 want to begin by taking a quick look back at the last

2 days to see whether our speakers were talking about problems, or opportunities, or

about turning problems into opportunities.

l Ken Cordell began by setting the stage with an overview of the urban waste wood

l

situation .

Steve Dennison followed with a discussion of one solution to the communications

problem: Fibrest, a computerized inventory program. Certainly this is a key element in

bridging the gap from problem to opportunity. He noted that so far we have failed to

apply either modern management or modern technology to the disposal of urban

wood waste.

Tommy Loggins was next with a description of another part of the inventory

process: the landfill survey made by the Georgia Forestry Commission in Atlanta,

‘Programs Director, Ameritan Forestry Association, 1319 18th Street, N.W., Washington,

D.C. 20036.

121
which clearly showed that a large volume of usable wood was being discarded. Here,

again, was an effort to identify a problem which could be turned into opportunity.

George Whitmer was next, with a discussion of the legal problems involved in

waste wood disposal and utilization. 1 was particularly glad that he mentioned the

value of public relations in these kinds of programs. It is important to let the public

know what you are doing. This aspect is often overlooked unless the public is somehow directly involved in the program.

Millard Davis discussed the difficult problem of source separation. He warned not

to tie your waste wood program to other recycling efforts such as waste paper or

aluminum. If those fail, for any reason, your waste wood goes down with them.

Dave Devoto spoke next. He described the ups and downs, the successes and failures, in trying to deal with a massive problem of urban waste wood from Dutch elm

disease in the Minneapolis-St. Paul area. There was no question which this was; it was

a problem that needed a solution, and this is a case-history Worth documenting.

Dave Walker then talked about the other side of this same coin: how at Georgia

Tech they were able to set up a program to use wood resulting from a natural disaster

and save the school some $10,000 by turning the problem of wasted trees into usable

mulch .

Ed Lempicki followed with a description of still another opportunity from waste

wood, describing how tree contractor Sam Willard saved disposal costs and turned

expense into income by operating his own specialty sawmill to convert waste urban

trees into specialty wood products. As the saying goes: if you get a lemon, make

lemonade.

The next speaker, Jim Commins, described the urban demolition and construction

wood survey conducted by his company and the way in which they were using these

woods for landfill and productive use. He said that there is a market out there because

the supply is almost everywhere, costs of competitive materials are rising, solid waste

laws are getting tougher, and attitudes of municipal officials are changing for the better.

Jay Lowery focused on the fuelwood situation, with an example of how the

disposal problem was converted into a utilization opportunity in Atlanta with the

institution of public fuelwood dumps. And he predicted that more of this material will

be converted into salable chips in the future.

Alex Cobb described one method of fuel preparation, the use of a hog. He obviously feels that urban waste wood is an opportunity since he concluded that he is in

the right business at the right time. He also provided us with some examples of the

various products and uses for hogged waste wood.

Jack Howard spoke next, describing the functions of a broker in the process of

turning one man’s waste product into another’s raw material. Here was the voice of

experience. He described severa1 ongoing activities ín which he is engaged, and he set

out a step-by-step procedure for marketing wood residues.

John Sturos described some of the research projects being carried out at Michigan

Tech to improve utilization technology, including a detailed slide and film description

of an innovative vacuum system ti, separate usable materials from whole-tree chips.

122
Jim McMinn took a close look at the wood eriergy picture and suggested that the

problem may be not how we dispose of urban waste wood but rather how we can get

more of it. He pointed out that not every situation is right for converting waste wood

to wood energy but that in some areas the potential is great and growing.

Gloria Mills presented a fascinating description of how Pinellas County, Florida,

will be creating energy from municipal waste, with a highly sophisticated and technologically advanced waste conversion plant.

Ed Lempicki took the podium for a second time to describe how he and his New

Jersey colleagues are serving the brokerage function in their State by bringing waste

products together with waste users to turn problems into opportunities.

Which brings me back to my starting point: do we have a problem, or are these

really opportunities that need better communications to be realized?

Frankly, 1 would not look to Washington at this time to fmance the kinds of things

that we are talking about here. The federal budget is tight, new programs are not being

considered because of inflation and, as the previous speaker said, few people in Washington know there is a problem of urban waste wood.

My advice to you is not to go to Washington and say that you have a waste wood

problem. Instead, go to Washington and tell your Congressmen how you can help

them. You have the examples of what has been done and what can be done. You have

a solution, not another problem.

1 have a feeling that if we can get the word out on the potential savings or profits

that you have shown are possible, the people in Washington may begin to pay attention.

1 would encourage you to be evangelists in the cause of turning urban waste wood

problems into opportunities. In other words, keep on doing what you have been doing.

There must be hundreds of municipal foresters, solid waste managers, politicians, tree

companies, wood users, and homeowners who would be delighted to know that things

can be done, that the technology exists, and that although you may not make a profit,

you certainly may save a dollar.

We will do our best at AFA to help you spread the Word.

123
J. Scott Anderson

Pullman Woodex Corp.

16 Berry HiB Road

Columbia, SC 29210

803 772-5085

Linda Anderson

USDA Forest Service

Carlton Street

Athens, GA 30602

404 546-2451

Bob Ashley

Vermeer Carolinas

P. 0. Box 32063

Charlotte, NC 28232

704 333-4647

Ed Banks

Georgia Forestry Comm.

7 M. L. King Drive

Atlanta, GA 30334

Billy Benson

Wilson Tree Co.

P. 0. Box 52

Florence, SC 29501

803 669-9906

Larry Biles

U. S. Forest Service

1720 Peachtree Rd., NW

Atlanta, GA 30309

404 881-3611

Robert Birchell

OK Forestry Div.

122 State Capitol Build.

Oklahoma City, OK 73105

405 521-3886

William 0. Boykin

SC Forestry Comm.

Robertson Build. US 15 N

Walterboro, SC 29488

803 549-5596

Wallace Brit

City of Fayetteville

P. 0. Drawer F

Fayettevtie, AR 72701

501 521-7700 ext. 271

REGISTRATION LIST

124

Stanley Carpenter

Dep. of Forestry

University of Kentucky

Lexington, KY 40546

606 258-4609

Hoyt Cheatwood

Duke Power Co.

P. 0. Box 33189

Charlotte, NC 28242

704 373-8072

Dennis Chef

Davey Environmentai Services

ll 7 South Water Street

Kent, OH 44240

216 673-9511

Alex D. Cobb, Jr.

Montgomery Industries, Int.

P. 0. Box 3687

JacksonvilIe, FL 32206

James A. Commins

JACA Corp.

550 Pinetown Rd.

Fort Washington, PA 19034

Jim Cook

GA Forestry Comm.

103 Massey Street

Pooler, GA 31322

912 748-4924

Harold K. Cordell

USDA Forest Service

Carlton Street

Athens, GA 30602

Charles Crawford

Clarke County Board of Comm.

P. 0. Box 448

Athens, GA 30601

404 546-8330

Millard Davis

Dep. of Environmental Protection

32 E. Hanover

Trenton, NJ 08625

609 984-7869
Steve Dennison

University of Mass.

204 Holdsworth

Amherst, MA 01003

413 545-1917

David Devoto

City of Minn.

300 Bryant

Minneapolis, MN 55409

612 822-0434

Bill Dost

University of Calif.

47th & Hoffman Blvd.

Richmond, CA 94804

415 231-9404

John Downs

Manatee Co.

P. 0. Box 386

Palmetto, FL 33561

813 146-8641

Carl Fitts

Fayetteville San. Dep., Rt. 2

Fayetteville, AR 72701

521-4806

Mitch Flinchum

Univ. of Florida

336 Newins-Ziegler Hall

Gainesville, FL 32611

904 392-l 850

E. D. Frame

VA Div. of Forestry

Box 3758

Charlottesville. VA 22903

BiU Gamble

Safety Test & Equip. Co., Irte.

Drawer 400

Shelby, NC 28150

704 482-7346

Leonard Gould

State and Ext. Forestry

2610 Clarlin Road

Manhattan, KS 66506

Karl F. Greenwell

FL Power & Light Co.

P. 0. Box 529100

Miami, FL 33152

305 552-4571

125

Dan Hall

GA Power Co.

P. 0. Box 4545

Atlanta, GA 30302

404 522-6060

Donald L. Ham

Clemson University

272 F&RR Bldg.

Clemson, SC 29631

803 656-2478

Robert G. Hitt, USFS

1720 Peachtree Rd., NW

Atlanta, GA 30309

404 881-3611

John W. Howard

Can-Am Sales, P. 0. Box 158

Skaneateles, NY

315 685-5611

J. B. Huffman

Forest Resources& Conservation

ll 8 Newins-Ziegler Hall

Univ. of Florida

Gainesville, FL 3 2611

Lawson E. Jarrell, Public Works

P. 0. Box 308

HuntsviUe, AL 35804

205 532-7342

Michael L. Keel

Div. of Forestry

Collins Build.

Tallahassee, FL

Leonard Kilian

SC Comm. of Forestry

Box 21707

Columbia, SC 29221

803 158-2261

Bruce Krantz

USDA Forest Service

210 S. Lamar

Jackson, MS 39201

601 969-4357

Ed Lempicki

NJ Bureau of Forestry

CN

Trenton, NJ 08625

609 292-2531
John D. List

Ingram Corp.

41 OO One Shell Square

New Orleans, LA 71039

Tommy Loggins

GA Forestry Comm.

728 Snelville Highw.

Lawrenceviile, GA 30245

Jay W. Lowery

City of Atlanta

260 Central Ave.

Atlanta, GA 30303

Frank McManus

Resource Recovery Report

1707 H St. NW

Washington, DC 20006

202 298-6244

Jim McMinn

USDA Forest Service

Carlton Street

Athens, GA 30602

404 546-2485

Rob Mason

GA Forestry Comm.

1085 Piedmont Ave.

Atlanta, GA 30309

404 656-3203

Carlos Mejia

City of Laredo

P. 0. Box 2769

Laredo, TX 78041

521 724-8273

Gloria A. Milis

UOP, Inc.

40 UOP Plaza

Des Plaines, IL 60016

312 391-2057

Lloyd W. Millwood

Public Works Dep.

770 Gayle Street

Mobile, AL 36604

205 438-7341 ext. 22

Richard Pardo

Ameritan Forestry ASSOC.

1319 18th, NW

Washington, DC 20036

126

R. C. Peterson

Miami University

Oxford, OH 45056

513 529-2237

W. C. Phelps

Woodamation, Inc.

P. 0. Box 1365

Chalmette, LA

T. S. Phillips

City of Gaffney

Yale Street

Gaffney, SC

803 489-5121

Carmino Puopolo

City of Laredo

P. 0. Box 1796

Laredo, TX 78041

512 727-2174

Eldon Ross

USDA Forest Service

P. 0. Box 2570

Asheville, NC 28802

Charlie Rountree

SC Forestry Comm.

P. 0. Box 21707

Columbia, SC 29221

803 758-2261

Howard J. Schlegel

Alabama Forestry Comm.

513 Madison Ave.

Montgomery, AL 36130

Bob Simmons

SC Forestry Comm.

P. 0. Box 284

Spartanburg, SC 29304

803 583-3438

John Sturos

USDA Forest Service

Forestry Sciences Lab.

Michigan Tech. Univ.

Houghton, MI

906 482-6303

Rodney Swink

NCFS

P. 0. Box 27687

Raleigh, NC 27611

919 733-2162
Mike Taras

USDA Forest Service

Carlton Street

Athens. GA 30602

Herman L. Terry

NC Div. of For. Resources

Raleigh, NC 27611

Max Treece

Duke Power Co.

P. 0. Box 33189

Charlotte, NC 28242

John Underwood

Union Camp

Frandli, VA

803 569-4588

Robert Vane

Self-employed

2630 North Murray Avenue

Milwaukee, WI 53211

414 964-5685

Robert A. Waldrop

Public Works Dep.

770 Gayle Street

Mobile, AL 36604

205 438-7341

127

Dave Walker

Urban Forester Consultant

Route 1

c/o Tammy’s Inn

Hayesville, NC 28904

Jimmy Walters

SC Forestry Comm.

19 Haygood Avenue

Charleston, SC 29403

803 792-1458

George Whitmer

GA Dep. of Natural Resources

34 20 Whipple St.

Hape, GA 30354

Johnny Williams

Escambia County

Rt. 8, Box 905

Pensacola, FL 32506

904 944-0011



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1

I

Southeastern Forest Experiment Station and others

1979. Urban waste wood utilization: proceedings of a conference on alternatives

I

to urban waste wood disposal, March 26-28,1979. U.S. Dep. Agrie. For.Serv.,

i

Gen. Tech. Rep. SE-16, 12 7 p. Southeast. For. Exp. Stn., Asheville, N. C.

Included in the Conference Proceedings are five papers on the resource situation, nine papers

on possibihties for utihzation, and three papers on planning.

Keywords: Wood residues, wood manufacturing, chipping.

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