ARB Emissions Inventory Methodology

for Composting Facilities

This Composting Methodology was developed with the assistance and review from the following 

Air Pollution Control Districts (APCD) or Air Quality Management Districts (AQMD): Bay Area 

AQMD, Butte County AQMD, Imperial County APCD, Sacramento Metro AQMD, San Joaquin 

Valley APCD, San Luis Obispo County APCD, Santa Barbara County APCD, Shasta County 

AQMD, South Coast AQMD, Ventura County APCD, and 

Yolo-Solano AQMD. 

I. Background and Applicability 

The purpose of this document is to describe a methodology for estimating emissions 

from California composting facilities. The methodology provides procedures for

estimating volatile organic compound (VOC) and ammonia (NH3) emissions from 

composting operations. Composting facilities are also sources of greenhouse gases 

such as methane, nitrous oxide, and carbon dioxide; however, a separate methodology 

that evaluates the complete lifecycle emissions for GHG emissions is warranted and is 

not included in this document. 

These facilities are typically subject to the regulations of the California Department of 

Resources, Recycling & Recovery (CalRecycle), the State Water Resource Control 

Board, and the local air districts. CalRecycle permits the facility siting, pathogen 

destruction, and general operation standards for composting facilities. The State Water 

Resource Control Board ensures compliance with state water protection requirements 

to ensure that wastewater from composting facilities is properly handled onsite. The 

local air districts permit composting facilities under New Source Review and in some 

cases have source specific regulations. They also receive odor complaints from local 

residents and refer them to CalRecycle or the delegated local enforcement agency.

This methodology can be used to estimate emissions from compostable material 

handling operation facilities (compost facility). A composting facility is an operation or 

facility that processes, transfers, or stores compostable materials for the purposes of 

controlled biological decomposition. Compostable materials include: grass clippings, 

woodwaste, manure, biosolids, digestate, and food waste. The methodology is 

applicable to facilities that process organic materials via an open windrow composting 

or aerated static pile processes. This methodology assumes that material is stockpiled 

prior to composting for up to 14 days before the active phase initiated. Active 

composting and curing is assumed to take approximately 8 to 9 weeks. Emissions from 

the composting, drying, or land application of organic wastes generated on farms and 

used to fertilize farm crops, as well as backyard composting and unintentional 

composting, are not addressed in this methodology. 

This emission inventory methodology addresses composting facilities with feedstocks 

that include greenwaste, co-composting (greenwaste combined with biosolids and/or 

1 

3/2/2015
manure) and foodwaste mixed with greenwaste. This methodology only applies to a 

compositing mixtures with no more than 15% by weight foodwaste, biosolids (by 

volume), or manure (by volume) and mixtures with no less than 85% by weight 

greenwaste.

The emission calculations from this methodology apply to facilities that are identified by 

the following Category of Emission Source (CES) code and Reconciliation Emission 

Inventory Code (REIC):

CES REIC Description

89490 199-170-0260-0000 Composting Waste Disposal

II. Source Category Description

a. Process Description

Composting is a process that involves the biological break down of organic matter into 

products that generally can be used in an agricultural application. Compost application 

to agricultural fields increases soil health while providing multiple co-benefits. Compost 

application can reduce the amount of synthetic fertilizer needed, reduce the amount of 

water used, decrease soil erosion, increase soil carbon storage, and reduce the use of 

herbicides.

Compostable organic waste feedstock can come from many sources including but not 

limited to the following: 

• Biosolids - organic material resulting from the treatment of wastewater or sewage 

sludge.

• Animal waste (manure) - non-human animal excretions and waste, including, but 

not limited to, dried solids and urine from cows or swine. 

• Poultry litter - poultry excretions and waste, including, but not limited to, dried 

solids and urine from chickens, turkeys, geese, or ducks. 

• Greenwaste - leaves, grass clippings, plants, tree prunings, branches, and 

woody material such as large trees and stumps, arising from domestic, 

agricultural, commercial or municipal activities.

• Pomace - the solid remains of grapes, olives, or other fruit after pressing for juice 

or oil. It contains the skins, pulp, seeds, and stems of the fruit 

• Foodwaste - any food scraps collected from the food service industry, grocery 

stores, or residential food scrap collection. Foodwaste also includes food material 

that is chipped and ground. Food packaging material may be included with the 

foodwaste and depending on the material will need to be separated or ground 

into the composting pile.

• Liquid waste – some facilities use liquid waste from various sources which may 

include: brewery waste, soda waste, restaurant wastewater, or wastewater 

residue. 

2
The following descriptions provide a general overview of the composting process at a 

facility and common types of composting processes that are currently being used.

Stockpile

Organic waste is generally transported by truck for processing at composting facilities. 

The material is dumped in piles to wait for incorporation into an active composting pile. 

Material may be held in these pre-processing stockpiles for a few hours up to several 

days. During the stockpile phase, the composting process may begin and create 

emissions that are uncontrolled. 

Grinding and Screening

In most cases, the materials in the stockpile will be ground and screened before they 

are placed in the windrows. An electric or diesel powered grinder is generally used for 

this purpose. The material may also be sent through a screening plant to sort out debris 

and garbage from the process.

Once the materials have been processed through the grinding and screening phase, it 

is then placed in piles or windrows to start the active and curing phases of the 

composting process. Brief descriptions of common composting methods used in 

California are listed below.

Static Piles

Static piles are the simplest form of composting and require little management and 

equipment. Once established, it is very difficult to adjust moisture, and static piles tend 

to go anaerobic in the center. Aerobic conditions can be achieved if the initial pile 

porosity is high (>60%) and there is a high proportion of bulking materials to keep pores 

open for air exchange. In general, product is kept on site for at least 15 days prior to 

sale to meet CalRecycle’s pathogen reduction requirements and is only turned if 

temperature warrants. Currently this composting method is not addressed by the air 

district rules and is not addressed in this methodology. Upon further analysis and 

additional data availability, emissions from static piles may be addressed at a later date. 

Windrow Composting

Windrow is the general term for an elongated pile of stacked raw materials. Piles need 

to be small (3-6’) and porous enough for air to pass through them over a long period of 

time. A turned windrow is one that is mechanically turned using a bucket loader, 

manure spreader or a windrow turner. Turning the windrow remixes the materials, 

allowing all the raw materials to be colonized by microorganisms in the warmer, more 

active internal part of the compost pile. Turning reintroduces oxygen and allows heat, 

water vapor, and gases to escape. The most important reason for turning the pile is to 

reestablish porosity allowing air to get into the pile.

3
Passively aerated windrow system (PAWS)

PAWS includes perforated pipes placed at the base of each windrow to promote 

convective airflow throughout the pile. The key to this system is thorough premixing of 

feedstocks before placing over the perforated pipes. Also, passively aerated windrows 

need to be insulated with finished compost to ensure that temperatures at the outer 

edges of the windrow are sufficient for pathogen destruction. 

Forced Aerated Static Piles

Forced aerated static piles are similar to PAWS piles, but blowers are installed at the 

ends of perforated pipes or air ducts. Air flow can be adjusted by changing the 

frequency and duration of the blower. Usually, blowers are set to turn on when the 

compost reaches a maximum temperature (e.g., 150F). Aerated static piles can be 

either positively or negatively aerated. (UW, 2002)

b. Emissions from Composting Windrows (VOCs, NH3,)

This emissions methodology addresses VOC and NH3 emissions resulting from 

composting of organic materials. A brief description for each of these is presented 

below.

VOCs: Volatile organic compounds are emitted when organic waste is composted. 

VOCs are emitted as a result of decomposition of organic material within the 

composting windrow and also directly from the feedstock. Whether the waste organic 

materials are composted or handled otherwise, they continue to emit a variety of VOCs. 

These VOCs are biogenic in origin; thus, they are biodegradable. Since these are 

biogenic and biodegradable compounds, any measure that would promote active 

biological processes will decrease their emissions. The key factors that need to be 

controlled to optimize the biological process of composting are oxygen content, 

moisture content, pH, and carbon:nitrogen (C:N) ratio. Furthermore, since the VOC 

compounds emitted are biodegradable, water soluble (to some extent), and have 

adsorptive potential, there are an array of mitigation alternatives including pseudobiofilter cap available to control their emissions. (SJV, 2010)

CalRecycle and UC Davis conducted a study in 2011 to determine what VOCs are 

emitted from composting piles and the reactivity of the VOCs detected. More than 100 

VOCs were detected and quantified in this study, including aliphatic alkanes, alkenes, 

aromatic hydrocarbons, biogenic organics, aldehydes, ketones, alcohols, furans, acids, 

esters, ether, halogenated hydrocarbons and dimethyl disulfide (DMDS). Alcohols were 

found to be the dominating VOC in the emissions from a compost pile regardless of 

age, with the highest emissions coming from the younger composting windrows. 

(CalRecycle, 2011) 

NH3: The presence of excess nitrogen in the form of ammonium carbonate or ammonia 

can be traced to the microbial metabolism of protein or other sources of nitrogen. If the 

C:N ratio is too low, the energy source (carbon or carbohydrates) may be less than that 

required for converting all the available nitrogen into microbial cells. In such an event,

the organisms make full use of available carbon and the excess nitrogen combines with 

4
hydrogen and is emitted as ammonia. If excess nitrogen in a decomposing mass is too 

great, ammonia may be formed in amounts sufficient to be toxic to the microbial 

population in the compost and will be emitted into the atmosphere as well.

c. Available Emissions Test Data

Emissions test data available for developing emission factors used in this methodology

are presented in Tables II-1 through II-3 below. The emissions test data was compiled 

to determine emission factors for greenwaste (including foodwaste up to 15% of 

feedstock) and biosolids/manure co-composting. A more detailed summary of the 

available emission factor sources can be found in the attached Appendix A.

Table II-1: Summary of Available Active Composting Greenwaste Emissions 

Test Data

Site VOC (lbs VOC/wet ton) Ammonia (lbs NH3/wet ton)

SCAQMD Inland 1.56 0.26

SCAQMD Inland 2.25 0.63

CIWMB (Modesto) 0.85 N/A

CIWMB (Modesto)* 1.95 N/A

Site X 6.30 2.34

Jepson Prairie 5.65 0.24

Northern Recycling (Zamora) 10.03 0.45

City of Modesto 1.50 N/A

City of Modesto* 2.20 N/A

Average 3.58 0.78

*Source test contained 15% by weight foodwaste

Table II-2: Summary of Available Active Co-Composting Greenwaste with 

Biosolids/Manure Emissions Test Data

Site VOC (lbs VOC/wet ton) Ammonia (lbs NH3/wet ton)

Recyc Inc. 0.53 2.7

EKO System 1.7 3.28

San Joaquin Composting, Inc. 3.12 2.81

Average 1.78 2.93

Table II-3: VOC Stockpile Greenwaste Emissions Test Data

Site VOC EF

(lb-VOC/wet ton-day)

Northern Recycling Zamora 0.13

NorCal Jepson Prairie (Vacaville) 0.42

SCAQMD Inland 0.10

SCAQMD Inland 0.13

Average 0.20

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d. VOC and Ammonia Emission Control Techniques

A number of control techniques are available to facilities to control the emissions from 

composting activities. These control techniques reduce both VOCs and ammonia

emissions. The first technique is aerated static piles (ASP). In aerated static pile 

composting, organic waste is mixed together in one large pile instead of rows. To 

aerate the pile, layers of loosely piled bulking agents (e.g., wood chips, shredded 

newspaper) are added so that air can pass from the bottom to the top of the pile. The 

piles also can be placed over a network of pipes that deliver air into or draw air out of 

the pile. Often air blowers are activated by a timer or a temperature sensor. The air is 

run through a biofilter to control the emissions from the windrow. ASP systems can 

incorporate covers over the windrow to increase the capture efficiency. Examples of 

these types of systems include the Gore cover, Engineered Compost System (ECS), or 

AgBag.

Finished compost can be used as a pseudo-biofilter. Finished compost can be applied 

in a thick layer over the surface of the windrow. Facilities may apply the finished 

compost for differing durations of time to reduce emissions. 90% of the VOC emissions 

happen in the active phase of composting and as a result compost covers are most 

effective during this active phase. (SJV, 2010) SJVAPCD and SCAQMD’s regulations 

are designed to get the most reductions early on in the active phase and require a 22-

day compost cover (60% reduction of VOCs) and 15-day compost cover (40% reduction 

of VOCs), respectively. 

Finally, one of the most effective ways to reduce emissions is to operate at an indoor 

facility or use a fully enclosed system. Indoor facilities are generally located in large 

warehouses and the indoor air is ducted through a biofilter. Fully enclosed systems 

may use drums, silos, or other types of sealed containers to capture the air and direct it 

through a biofilter. Facilities can achieve 80% or more emissions reductions using 

these types of emission control devices.

e. Emission Control Demonstrations

A number of studies have analyzed the use of emission control devices on composting 

windrows. The most common types in California involve the use of compost as a cover 

for the windrows or an aerated static pile that passes the exhaust gas through a biofilter. 

Table II-4 shows the most common emission control devices with their respective 

aeration types (positive or negative), emission control methods (compost cap, biofilter, 

etc.), and cover material (biofilter, membrane, plastic, etc.). Detailed summaries of the 

sources can be found in the attached Appendix A.

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Table II-4: Control Techniques for Composting Operations

Control Type Aeration Control Method Cover Material

Windrow

Static Pile – No Biofilter Passive None None

Managed Windrow – No Biofilter Passive None None

Water Management Requirements1 Passive Watering None

Static Pile/Passively Aerated Windrow 

covered 15 days with a biofilter2

Passive At least 6 inches of 

Compost Cover

Finished Compost or 

Compost Overs

Static Pile/Passively Aerated Windrow 

covered 22 days with a biofilter1

Passive At least 6 inches of 

Compost Cover

Finished Compost or 

Compost Overs

Aerated Static Pile (ASP)

Negative ASP with Biofilter (classic)3 Forced, Negative 

Air

At least 6 inches of 

Compost Cover (optional), 

Biofilter Bed

Finished Compost or 

Compost Overs

Positive ASP with Biofilter Cover Forced, Positive Air At least 6 inches of 

Compost Cover

Finished Compost or 

Compost Overs

Enclosed Aerated Static Pile 

Enclosed, Negative ASP with Biofilter 

(e.g., ECS)

Forced, Negative 

Air

Biofilter Bed Engineered Cover Tarp

Negative ASP with Biofilter (indoor)3 Forced, Negative 

Air

Biofilter Bed Building

Enclosed, Positive ASP (e.g., GORE 

Cover)

Forced, Positive Air None Engineered Cover 

Membranes

Ag Bag Forced, Positive Air None Thick Mill Plastic Bag

General Enclosed Pile vented through 

a Biofilter

Forced Vented through biofilter Finished Compost or 

Compost Overs

1

Requires compliance with pile management and/or watering requirements in SJVAPCD’s rule 4566.

2

Requires compliance with pile management and/or watering requirements in SCAQMD’s rule 1133.3. 3

These composting types can be conducted at the indoor setting venting indoor air to a biofiltration control system.

(SC, 2011a) (NRAES, 1992) (Paul & Geesing, 2009)

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III. Recommended Emission Estimation Approaches

This methodology describes two approaches for estimating emissions. The first is 

based on actual emission testing and the second approach relies on industry averaged 

data emission factors from composting facilities. These two approaches are described 

below. 

a. Facility Specific Data (Emission Testing)

Conducting on-site emissions testing to determine site specific emission factors is one 

approach for estimating emissions from a given facility. It is recommended to use the 

testing methods listed in the South Coast Air Quality Management District (SCAQMD)

or San Joaquin Valley Air Pollution Control District (SJVAPCD) composting rules. 

SCAQMD lists their testing requirements and protocols in SCAQMD Rule 1133.3(e). 

SJVAPCD lists their testing requirements in SJVAPCD Rule 4566(6.4). This data can 

be combined with the facility throughput, control technology factors etc. as described in 

b. below to estimate the annual emissions for the facility. 

b. Composting Emission Factor 

An alternative approach is to use emission factors developed based on the results of 

emission tests or studies performed at one or more facilities. This approach is 

described below. Use of the following emission factors are subject to the approval of 

the local air districts who permit the composting facilities.1

 Additional testing may be 

necessary to demonstrate emission control efficiency factors or emissions from a 

composting facility.

i. Data Requirements

For each facility, the following information would be needed to calculate the emissions 

for the facility using a recommended emission factor:

• Facility throughput (wet tons)

o Annual amount of organics processed at the facility. Wet tons is defined 

as the mass of greenwaste, co-composting, and foodwaste that is 

processed at the facility, excluding any screen waste that does not go 

through the composting process.

• Feedstock Composition (e.g. greenwaste, foodwaste, co-composting)

o This emission factor is appropriate for greenwaste only or a mixture of 

greenwaste with foodwaste or co-composting up to 15% by weight of total.

• Control Technology Efficiency (ASP, biofilter)

o It is necessary to determine the control technology emission reduction 

efficiency. This can be done with source testing or using the standard 

recommended values in Table III-3.

• Average Stockpile Time

1 The local air pollution control districts or air quality management districts may have established emission 

factors and/or regulation approved for use in their corresponding air basin. Contact the local air district 

for more information.

8

 
o It is necessary to average the time that the incoming organics are 

stockpiled before incorporation into the composting piles. 

ii. Estimating Emissions from a Facility

Total Annual Emissions = (CPEF x (1-CE) x TP) + (SEF x SD X TP);

• Where

o CPEF = Composting Process Emission Factor (lbs/wet-ton)

o SEF = Stockpile Emission Factor (lbs/wet ton-day)

o SD = Average number of days material is stockpiled (days)

o CE = Control Efficiency (Percentage)

o TP = Total annual facility throughput (wet-tons)

Table III-1: Recommended Emission Factors for Greenwaste and Foodwaste1

Pollutant Stockpile

(lbs/wet ton-day)

Composting Process

(lbs/wet ton)

VOC 0.20 3.58

NH3 N/A 0.78

Table III-2: Recommended Emission Factors for Greenwaste Mixed with Animal 

Manure, Biosolids, or Poultry Litter (Co-Composting1)

Pollutant Co-Composting Process

(lbs/wet ton)

VOC 1.78

NH3 2.93

1 Foodwaste, biosolids, and manure can be a maximum of 15% by weight of the total mixture with 

greenwaste.

9

 
Table III-3: Control Techniques for Composting Operations

Control Type Aeration VOC Control Efficiency NH3 Control Efficiency

Windrow

Static Pile – No Biofilter Passive 0% 0%

Managed Windrow – No Biofilter Passive 0% 0%

Water Management Requirements1 Passive 19% 19%

Static Pile/Passively Aerated Windrow

covered 15 days with a biofilter2

Passive

40% 20%

Static Pile/Passively Aerated Windrow 

covered 22 days with a biofilter1

Passive

60% 20%

Aerated Static Pile (ASP)

Negative ASP with Biofilter (classic) Forced, Negative 

Air 26% 23%

Positive ASP with Biofilter Cover Forced, Positive Air 80%-98% 53%

Enclosed Aerated Static Pile 

Enclosed, Negative ASP with Biofilter 

(e.g., ECS)

Forced, Negative 

Air 80%-98% 70%-78%

Negative ASP with Biofilter (indoor) Forced, Negative 

Air 80%-98% 80%-99%

Enclosed, Positive ASP (e.g., GORE 

Cover)

Forced, Positive Air

80% 70%

Ag Bag Forced, Positive Air 80% 70%

General Enclosed Pile vented through 

a Biofilter

Forced 80% 70%

1

Requires compliance with pile management and/or watering requirements in SJVAPCD’s rule 4566.

2

Requires compliance with pile management and/or watering requirements in SCAQMD’s rule 1133.3.

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Data Sources

(CalRecycle, 2011) Volatile organic compound emissions from green waste composting: 

Characterization and ozone formation

(CalRecycle, 2013) Greenwaste Compost Site Emissions Reductions from Solar‐

powered Aeration and Biofilter Layer

(Colorado, 2012) Composting: VOC Emissions & Best Management Practices, 

Colorado Department of Public Health and Environment

(Elsevier, 2009) A methodology to determine gaseous emissions in a composting plant,

Composting Research Group, Department of Chemical Engineering, Barcelona, Spain

(NRAES, 1992) NRAES, On-Farm Composting Handbook, June 1992.

(Paul & Geesing, 2009) John Paul and Dieter Geesing, Compost Facility Operator 

Manual, 2009.

(SC, 2011) RULE 1133.3 EMISSION REDUCTIONS FROM GREENWASTE 

COMPOSTING OPERATIONS

(SC, 2011a) SCAQMD, Final Staff Report for Proposed Amended Rule 1133.1 and 

Proposed Rule 1133.3, July 2011.

(SDSU, 2012) Full-Scale VOC Emissions from Green And Food Waste Windrow 

Composting, Fatih Büyüksönmez, Department of Civil, Construction and Environmental 

Engineering, San Diego State University

(SJV, 2011) RULE 4566 ORGANIC MATERIAL COMPOSTING OPERATIONS, 

SJVAPCD

(SJV, 2010) Compost VOC Emission Factors, SJVAPCD

(UW, 2002) The Art and Science of Composting, Leslie Cooperband, University of 

Wisconsin-Madison

(Yolo, 2012) ECS AC Composter Pilot Facility, Air Emissions Source Test, Thomas R. 

Card, P.E., Charles E. Schmidt, PhD.

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Appendix A to ARB Recommended Emissions Inventory 

Methodology for Composting Facilities

A. Overview

This appendix provides a summary of available California facility composting emissions 

data and an overview of a recent study conducted on effectiveness of emission control

systems.

B. California Air District Emission Factors

Two sets of emission factors have been adopted by local air quality management 

districts. The San Joaquin Air Pollution Control District (SJVAPCD) published their 

emission factor in 2010. SJVAPCD adopted Rule 4565: Biosolids, Animal Manure, and 

Poultry Litter and Rule 4566: Organic Material Composting Operations for composting 

facilities in March of 2007 and August of 2011, respectively. The South Coast Air 

Quality Management District (SCAQMD) adopted their Rule 1133.2: Emission 

Reductions from Co-Composting Operations in January 2003 and Rule 1333.3: 

Emission Reductions from Greenwaste Composting Operations in July 2011. SCAQMD

published the following emission factors as part of the 2011 rulemaking process. Table 

A-1 list the factors for each district. As can be seen, SJVAPCD has an emission factor 

for VOC emissions and SCAQMD has emission factors for both VOCs and ammonia. 

The following Tables A-2 through A-5 present the underlying emissions source test data 

that were used in developing the approved emission factors for each district. 

Table A-1: Summary of Composting Emission Factors Approved by SJVAPCD & 

SCAQMD

Compost 

Type

Stockpile 

(lb-VOC/wet-ton-day)

Windrow EF Per 

Composting Cycle 

(lb-VOC/wet ton)

Windrow EF

(lb NH3/wet 

ton)

SJVAPCD SCAQMD SCAQMD SCAQMD SCAQMD

Greenwaste, 

Foodwaste, 

Grape Pomace

0.2 N/A 5.71 4.67 0.71

CoCompostingN/A N/A 1.78 1.78 2.93

1
Table A-2: SJVAPCD VOC Stockpile Greenwaste Emissions Testing Data

Site Length of Time the 

Material Stays in the 

Stockpiles (day)

Season 

Samples

Taken

EF

(lb-VOC/wet ton-day)

Northern Recycling 

Zamora 90 Spring 0.126

NorCal 

Jepson Prairie 

(Vacaville)

7 Summer 0.422

SCAQMD

Inland 9 Winter 0.101

SCAQMD

Inland 21 Fall 0.133

Average 0.196

Table A-3: SJVAPCD VOC Windrow Greenwaste Emissions Testing Data

Site Sampling Age of 

Material

Season Samples 

Taken

EF 

(lb-VOC/wet ton)

CIWMB (Modesto) Over the Active + 

Curing Phase (days 

not sampled were 

interpolated)

Fall 0.85*

Site X Spring 6.30

NorCal Jepson 

Prairie (Vacaville)

Summer 5.65

Northern Recycling 

(Zamora)

Spring 10.03

Average 5.71

*1.54 was identified in the green waste report after a recalculation to better represent other 

sites; however, 0.85 was the actual value reported from this test site and will be used in the EF 

determination.

Table A-4: SCAQMD Greenwaste VOC & Ammonia Emissions Testing Data

Site Sampling age 

of material

Season samples 

were taken

Throughput 

(tons/day)

VOC 

(lbs/wet ton)

Ammonia 

(lbs/wet ton)

Inland Over the static 

and windrow 

phase

Winter 307 1.56 0.26

Inland Fall 350 2.25 0.63

Modesto Over the active 

and curing 

phase (days 

were not 

sampled were 

interpolated)

Fall 103 0.85 N/A

Site X Spring 200 6.30 2.34

JPO Summer 163 5.65 0.24

Zamora Spring 319 10.03 0.445

Weighted average emission factors 4.67 0.66

2
Table A-5: SCAQMD & SJVAPCD Co-Composting Uncontrolled VOC & Ammonia 

Emissions Testing Data

Facilities VOC E.F. (lb/ton 

mix)

NH3 E.F. (lb/ton 

mix)

RECYC Inc. (Corona, 1995) 0.53 2.7

EKO System (Corona, 1995) 1.7 3.28

San Joaquin Composting, Inc. 

(Lost Hills, 1996)

3.12 2.81

Average 1.78 2.93

As shown in Table A-4, SCAQMD used the same emission source data as SJVAPCD.

However, they included two additional source tests from the Inland facility in the 

calculation to determine the emissions factor. This caused the weighted emission factor 

to decrease by approximately 1 lb/wet ton. At the time of the SJVAPCD’s emission 

factor development, SJVAPCD chose not to use these source tests because they 

believed that the facility was small and did not accurately reflect the size of the facilities 

in their district. Because there is a limited subset of data, we have included the Inland 

source test information. While the data may not be representative of the sites in 

SJVAPCD, it is representative of many sites throughout the state and is included in this 

methodology.

C. Composting Facility Emissions Test Data

a. Modesto Composting Facility

CalRecycle sponsored a study in 2012 by San Diego State University. The study was 

conducted at the Modesto Composting Facility operated by the City of Modesto. 

Samples were collected with United States Environmental Protection Agency (U.S. 

EPA) isolation flux chambers for 59 days and analyzed according to the SCAQMD 

Method 25.3. Two separate composting windrows were tested in this study. The first 

windrow was comprised of greenwaste only and the second windrow was a mixture of 

85% greenwaste and 15% foodwaste. Emission factors were determined to be 

1.4 g/kg-dry-weight (dw) (1.5 lbs VOC/wet ton1) and 2.2 g/kg-dw (2.2 lbs VOC/wet ton1) 

for greenwaste and greenwaste combined with foodwaste composting, respectively. 

(SDSU, 2012)

b. Composting Outside of California

The Colorado Department of Public Health and Environment published a memo titled 

“Composting: VOC Emissions & Best Management Practices” in 2012. In the memo, 

they cited the SJVAPCD emission factor as “the most robust and technically sound 

study currently available.” However, they did not use the stockpile emission factor as 

they assumed that the climate differences would impact the emissions from the 

stockpile. This was not a concern for the active composting emission factor as the 

1 Conversion to wet tons was done using the initial blend moisture content.

3

 
moisture content, temperature, and turning requirements should create a windrow with 

similar characteristics. (Colorado, 2012)

D. Summary of Composting Emission Sources

The following tables A-6 through A-7 present a summary of the available source testing 

results for composting facilities whose test results were used to develop the emission 

factors in the proposed composting emission inventory methodology.

Table A-6: Summary of Available Active Composting Greenwaste Emissions Test 

Data

Site VOC (lbs VOC/wet ton) Ammonia (lbs NH3/wet ton)

Inland 1.56 0.26

Inland 2.25 0.63

CIWMB (Modesto) 0.85 N/A

CIWMB (Modesto)* 1.95 N/A

Site X 6.30 2.34

Jepson Prairie 5.65 0.24

Northern Recycling (Zamora) 10.03 0.45

City of Modesto 1.50 N/A

City of Modesto* 2.20 N/A

Average 3.58 0.78

*Source test contained 15% foodwaste

Table A-7: Summary of Available Active Co-Composting Greenwaste with 

Biosolids/Manure Emissions Test Data

Site VOC (lbs VOC/wet ton) Ammonia (lbs NH3/wet ton)

Recyc Inc. 0.53 2.7

EKO System 1.7 3.28

San Joaquin Composting, Inc. 3.12 2.81

Average 1.78 2.93

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F. Emission Reduction Technology Assessments

The following section provides a brief overview of the sources that were used to develop 

the proposed emission reduction (control efficiency) factors in the emission inventory 

methodology. 

a. CalRecycle: Greenwaste Compost Site Emissions Reductions from SolarPowered Aeration and Biofilter Layer

CalRecycle and SJVAPCD sponsored a test project that monitored emissions from a 

solar powered aerated static pile system (eASP). The eASP utilized ambient air blown 

into the pile from the bottom; the blowers were powered by photovoltaic panels and 

associated batteries. The eASP had a biofiltration layer added to the surface as an air 

pollution control measure. A series of compost windrows were built concurrent with the 

eASP using the same feedstock. The air emissions from the eASP were compared to 

the on‐site measured air emissions of the current industry standard windrow composting 

method.

Table A-8 provides a summary of the emissions from the windrow over the 22‐day 

active composting period, as specified by SJVAPCD Rule 4566. VOC reductions of 

98.8% were achieved when compared to the control windrows. Reductions in ammonia 

emissions were 83% using tubes in the field, and 53% from the laboratory, when the 

eASP was compared to the control windrows. Reductions in emissions of greenhouse 

gases ranged from 13% for methane up to nearly 89% for N2O for the eASP system 

when compared to the controls. (CalRecycle, 2013)

Table A-8: Results of eASP Study (lbs pollutant/wet ton)

b. Colorado Department of Public Health and Environment: Composting: 

VOC Emissions & Best Management Practices

Colorado cited the October 31, 2007 report “Emissions Testing of Volatile Organic 

Compounds from Greenwaste Composting at the Modesto Compost Facility in the San 

Joaquin Valley” published by the California Integrated Waste Management Board and 

used 75% control efficiency for biofilter/compost cover that is used for the entire 

process. They used a 56.25% control efficiency when the biofilter/compost cover is 

used only in the first two weeks.

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Table A-9: Summary of Control Efficiencies from Colorado Department of Public 

Health and Environment

G. Regulatory Requirements for Emission Controls

SJVAPCD and SCAQMD both specify in their regulations the minimum requirements for 

composting facilities emission control devices. The requirements of the regulations are 

summarized in the following tables.

Table A-10A: SJVAPCD Rule 4565 Co-Composting Emission Control Device 

Requirements

Facility Size Emission Control Device Alternative to Emission 

Control Device

Less than 20,000 tons/year Implement at least 3 of the Class One mitigation 

measures listed in Table 2 OR implement at least 2 Class 

One mitigation measures in addition to 1 Class Two 

mitigation measure for active composting listed in Table 

A-10B.

20,000 to 100,000 

tons/year

Implement at least 4 of the Class One mitigation 

measures listed in Table 2 OR implement at least 3 Class 

One mitigation measures in addition to 1 Class Two 

mitigation measure for active composting listed in Table 

A-10B.

Greater than 100,000 

tons/year

Implement at least 4 Class One mitigation measures in 

addition to 1 Class Two mitigation measure for active 

composting OR Implement at least 2 Class One mitigation 

measures, in addition to 1 Class Two mitigation measure 

for active composting and 1 Class Two mitigation 

measure for curing composting listed in Table A-10B.

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Table A-10B – SJVAPCD Rule 4565 Co-composting Facility Mitigation Measures

Class One Mitigation Measures

1. Scrape or sweep, at least once a day, all areas where compostable material is

mixed, screened, or stored such that no compostable material greater than one 

inch (1”) in height is visible in the areas scraped or swept immediately after 

scraping or sweeping, except for compostable material in process piles or storage 

piles.

2. Maintain a minimum oxygen concentration of at least five percent (5%), by volume, 

in the free air space of every active and curing compost pile.

3. Maintain the moisture content of every active and curing compost pile between 

40% and 70%, by weight.

4. Manage every active pile such that the initial carbon to nitrogen ratio of every pile 

is at least twenty (20) to one (1).

5. Cover all active compost piles within 3 hours of each turning with one of the 

following: a waterproof covering; at least six (6) inches of finished compost; or at 

least six (6) inches of soil.

6. Cover all curing compost piles within 3 hours of each turning with one of the 

following: a waterproof covering; at least six (6) inches of finished compost; or at 

least six (6) inches of soil.

7. Implement an alternative Class One mitigation measure(s) not listed above that 

demonstrates at least a 10% reduction, by weight, in VOC emissions.

Class Two Mitigation Measures

8. Conduct all active composting in aerated static pile(s) vented to a VOC emission 

control device with a VOC control efficiency of at least 80% by weight.

9. Conduct all active composting in an in-vessel composting system vented to a VOC 

emission control device with a VOC control efficiency of at least 80% by weight.

10. Conduct all curing composting in aerated static pile(s) vented to a VOC emission 

control device with a VOC control efficiency of at least 80% by weight.

11. Conduct all curing composting in an in-vessel composting system vented to a VOC 

emission control device with a VOC control efficiency of at least 80% by weight.

12. Implement an alternative Class Two mitigation measure(s) not listed above that 

demonstrates at least 80% reduction, by weight, in VOC emissions.

Table A-11: SJVAPCD Rule 4566 Greenwaste and Foodwaste Emission Control 

Device Requirements

Facility Size Emission Control Device Alternative to Emission 

Control Device

Less than 200,000 

tons/year

Watering System 

Requirements

19% Reduction of VOC 

emissions

200,000 to 750,000 

tons/year

Watering System 

Requirements and Finished 

Compost Cover

60% Reduction of VOC 

emissions

Greater than 750,000 

tons/year

80% Reduction of VOC 

emissions

80% Reduction of VOC 

emissions

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Table A-12: SCAQMD Rule 1133.2 Co-Composting Emission Control Device 

Requirements

Facility Size Emission Control Device Alternative to Emission 

Control Device

Any new facility with greater 

than 20% manure, by 

volume

Enclosed Emission Control 

Device with a control 

efficiency of 80% reduction 

of VOC and Ammonia 

Emissions

80% Reduction of VOC and 

Ammonia emissions

Table A-13: SCAQMD Rule 1133.3 Greenwaste Emission Control Device 

Requirements

Facility Size Emission Control Device Alternative to Emission 

Control Device

New facility with less than 

20% manure or 5,000 tons 

foodwaste

Cover windrow with finished 

compost and watering 

requirements

40% Reduction of VOC 

emissions and 20% 

reduction of Ammonia 

emissions

New facility with greater

than 20% manure, by 

volume, or 5,000 tons and 

greater than 10% 

foodwaste, by weight

80% Reduction of VOC and 

ammonia emissions

80% Reduction of VOC and 

Ammonia emissions

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