Harris_Stephanie_FinalShands

VOLATILE ORGANIC COMPOUND EMISSIONS FROM COMPOSTING
_______________
A Project
Presented to the
Faculty of
San Diego State University
_______________
In Partial Fulfillment
of the Requirements for the Degree
Master of Science
in
Civil Engineering
_______________
by
Stephanie Harris
Summer 2013

SAN DIEGO STATE UNIVERSITY
The Undersigned Faculty Committee Approves the
Project of Stephanie Harris:
Volatile Organic Compound Emissions from Composting
_____________________________________________
Fatih Büyüksönmez, Chair
Department of Civil, Construction, and Environmental Engineering
_____________________________________________
Tyler Radniecki
Department of Civil, Construction, and Environmental Engineering
_____________________________________________
Richard Gersberg
Graduate School of Public Health
______________________________
Approval Date

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Copyright © 2013
by
Stephanie Harris
All Rights Reserved

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ABSTRACT OF THE PROJECT
Volatile Organic Compound Emissions from Composting
by
Stephanie Harris
Master of Science in Civil Engineering
San Diego State University, 2013
This paper is a review of the aerobic composting process and the emissions of volatile
organic compounds (VOCs) from this process. To understand why and how emissions of
VOCs occur, it is necessary to understand the composting process itself, including process
parameters that can be monitored and controlled. A review of the literature was conducted in
order to determine the source of VOC emissions within the confines of the composting
process. This paper also explores the nature and magnitude of VOC emissions as reported in
the literature. The advantages and disadvantages of composting and the need for composting
are also considered.

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TABLE OF CONTENTS
PAGE
ABSTRACT..............................................................................................................................iv
LIST OF TABLES...................................................................................................................vii
CHAPTER
INTRODUCTION TO COMPOSTING................................................................................... 1
Windrow Composting............................................................................................. 1
Aerated Static Pile Composting.............................................................................. 2
In-Vessel Composting............................................................................................. 2
COMPOSTING PARAMETERS ............................................................................................. 3
Carbon:Nitrogen Ratio............................................................................................ 3
Moisture Content..................................................................................................... 3
Aeration Rate .......................................................................................................... 4
Particle Size............................................................................................................. 4
pH Variability ......................................................................................................... 5
Temperature ............................................................................................................ 5
PHASES OF COMPOSTING................................................................................................... 6
Mesophilic Phase .................................................................................................... 6
Thermophilic Phase................................................................................................. 6
Curing Phase ........................................................................................................... 7
COMPOSTING FEEDSTOCK ................................................................................................ 8
Feedstock as a Carbon Source ................................................................................ 8
Feedstock as a Nitrogen Source.............................................................................. 8
Feedstock as a Sulfur Source .................................................................................. 9
ADVANTAGES OF COMPOSTING .................................................................................... 10
Landfill Diversion................................................................................................. 10
Composting and Greenhouse Gas Emissions ....................................................... 11
Benefits of the Application of Compost as a Soil Amendment ............................ 12
DISADVANTAGES OF COMPOSTING.............................................................................. 13
Pathogens .............................................................................................................. 13

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Fungal Opportunists.............................................................................................. 13
Emissions of Air Contaminants ............................................................................ 14
Volatile Organic Compounds ............................................................................... 14
Volatile Organic Compounds and Human Health .......................................... 14
Volatile Organic Compounds and Odor Nuisance.......................................... 17
Volatile Organic Compounds and Ground-Level Ozone................................ 18
Volatile Organic Compounds and California Local Air District Rules.......... 18
South Coast Air Quality Management District......................................... 19
San Joaquin Valley Air Pollution Control District ................................... 20
Antelope Valley Air Pollution Control District ........................................ 21
Particulate Matter and Nuisance Rules ........................................................... 22
Composting Volatile Organic Compound Emissions Sources ....................... 22
Biogenic Volatile Organic Compounds .................................................... 23
Vegetation as a Source of Volatile Organic Compounds ......................... 24
Microbial Volatile Organic Compounds................................................... 24
Xenobiotic Sources of Volatile Organic Compounds............................... 25
Magnitude of Volatile Organic Compound Emissions from Composting
Facilities.................................................................................................... 25
Factors Affecting Volatile Organic Compound Emissions ............................ 27
Feedstock and Volatile Organic Compound Emissions............................ 27
Phases of the Composting Process and the Emissions of Volatile Organic
Compounds ............................................................................................... 27
Control Parameters and Volatile Organic Compound Emissions............. 28
Review of Selected Studies....................................................................... 29
CONCLUSIONS..................................................................................................................... 30
REFERENCES ....................................................................................................................... 30

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LIST OF TABLES
PAGE
Table 1. Summary of the Magnitude of VOC Emissions from Selected Studies ..................... 1
Table 2. South Coast and San Joaquin District VOC Emission Factors................................... 1
Table 3. Compounds Identified in Selected Studies ................................................................. 2

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CHAPTER 1
INTRODUCTION TO COMPOSTING
Composting consists of either a passive or an engineered process where organic waste
is biodegraded, resulting in a humus-like product termed compost (Tchobanoglous, Theisen,
and Vigil 1993). Compost is organic matter that has been stabilized and is able to be applied
to soil as an amendment. There are several different variations of the composting process, yet
the basic principles remain the same (Tchobanoglous, Theisen, and Vigil 1993). Organic
matter is reduced in volume and is converted from a waste product into a usable and
marketable end product. While composting is a viable method of waste reduction, there are
disadvantages associated with the process, including the emission of volatile organic
compounds (VOCs).
Composting can occur under aerobic or anaerobic conditions. Anaerobic variations of
the composting process are often used to generate methane for energy recovery. While the
anaerobic process may be advantageous for energy production, it is an intricate process that
requires careful control, and for this reason the majority of commercial composting facilities
use an aerobic process. Aerobic processes are energy-intensive, rather than being a source of
energy, but they are more easily controlled and utilized (Tchobanoglous, Theisen, and Vigil
1993).
There are several variations of the aerobic composting process. Each variation has
advantages and disadvantages. The selection of a specific method will depend on the site
specifics. The common aerobic composting process variations can be described as follows:
windrow, aerated static pile (ASP), and in-vessel (Tchobanoglous, Theisen, and Vigil 1993).
WINDROW COMPOSTING
In windrow composting, waste is piled into long rows and is turned by a front-end
loader or similar machinery in order to supply oxygen to the windrow (Tchobanoglous,
Theisen, and Vigil 1993). Windrows are typically dome-shaped to shed rain and snow
(Rhyner et al. 1995). Windrow composting benefits include low operational and capital costs.

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Disadvantages of windrow composting include a large footprint, the susceptibility of the
process to the weather, the lack of control over the oxygen supply, and the potential of the
site to act as a volume source of emissions rather than a point source (Tchobanoglous,
Theisen, and Vigil 1993). Windows may attract vermin and may produce compost that is
heterogeneous in nature. The process takes months to complete, while other, more controlled
processes take less time to produce mature compost (Rhyner et al. 1995).
AERATED STATIC PILE COMPOSTING
The ASP method employs forced aeration. Air is often introduced through piping at
the bottom of the compost pile. The components required for ASP systems are simple and
typically do not require extensive maintenance (Tchobanoglous, Theisen, and Vigil 1993).
The benefits of this type of system include enhanced control of the oxygen content of the
compost by supplying air in a more uniform manner. Even further control can be obtained by
the addition and monitoring of oxygen and temperature sensors, so that the aeration rates can
be adjusted according to the current conditions present in the compost pile (Rhyner et al.
1995). The capital cost depends on the size of the system. Smaller systems are more
affordable, while costs for larger systems may become prohibitive, depending on the
operation. Operational costs of ASP systems are high and the required footprint is large; in
addition, the ASP process may act as a volume source of emissions, depending on the design
(Tchobanoglous, Theisen, and Vigil 1993).
IN-VESSEL COMPOSTING
The in-vessel method utilizes a closed reactor. The system can be designed as a plug
flow or mixed/dynamic reactor. Dynamic reactors and plug flow reactors have high capital
cost, but have low operational costs and offer good control of the oxygen content of the
compost. A clear benefit of in-vessel composting is that the emissions from this type of
system may act as a point source and may be more easily controlled. The footprint of in-
vessel systems may be smaller than the footprints associated with windrow and ASP
processes (Tchobanoglous, Theisen, and Vigil 1993).

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CHAPTER 2
COMPOSTING PARAMETERS
Each variation of the aerobic composting process shares the same control and
monitoring parameters. The method of adjusting control parameters may vary from process
to process, but the basic principles of aerobic biodegradation remain the same
(Tchobanoglous, Theisen, and Vigil 1993). Control parameters include the carbon:nitrogen
ratio (C:N), moisture content, aeration rate or turning frequency, and particle size. These
parameters should be monitored and adjusted as required. In addition, pH and temperature
are indicator parameters that can be monitored to provide information about the state of the
compost pile.
CARBON:NITROGEN RATIO
The C:N ratio is considered to be one of the most important control parameters to
adjust in order to have a successful composting operation (Tchobanoglous, Theisen, and
Vigil 1993). The C:N ratio is dependent on the feedstock materials. Materials are often
blended to supply the optimal C:N ratio. Carbon or nitrogen may exist in a form that is not
readily available to the microbial community present in the feedstock. Some sources of
carbon, such as lignin, are not readily available (Tchobanoglous, Theisen, and Vigil 1993).
Microbes typically utilize C:N at an 8–10:1 ratio (Kissel, Henry, and Harrison 1992). It has
been suggested that a C:N ratio between 25:1 and 50:1 is ideal for the composting process.
Ratios below this value can allow nitrogen to escape from the compost as ammonia.
Additionally, biological activity may be inhibited. If the ratio is too high, nitrogen may
become a limiting nutrient (Tchobanoglous, Theisen, and Vigil 1993).
MOISTURE CONTENT
Moisture content is another important control parameter. The moisture content is
expressed as the weight of water as a percentage of the wet weight of the material (Landreth
and Rebers 1997). If the moisture content of the material is too high, the oxygen supplied
will be limited, since the volume of the voids in the compost will be decreased. If excess
moisture is present, the compost material may not reach ideal temperatures. On the other

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hand, if the compost material is reaching temperatures that are too high, microbes may be
inactivated. In this case the moisture content could be increased in order to reduce the
temperature. Microbial activity, which is required for the composting process, will not occur
if the moisture content is insufficient. There is no single ideal moisture content, as the ideal
percentage depends on the structure of the material to be composted (Haug 1980). Moisture
content can be controlled by the addition of dry materials such as amendments or bulking
agents. Drying feedstock before it is introduced into the composting process can also control
the moisture content. As the temperature of the compost materials increases, it is important to
monitor the moisture content, as much of the water is driven off by the heated pile (Rhyner et
al. 1995).
AERATION RATE
The aeration rate or turning frequency is another control parameter that must be
carefully considered. Oxygen is required for adequate microbial activity. If the oxygen
content decreases sufficiently, microbial activity will be inhibited, thus decreasing the
temperature of the compost and inhibiting the composting process (Rynk et al. 1992).
Aeration can also be used to control the moisture content of the materials, as well as the
temperature of the compost. While the addition of moisture can control compost material
temperatures, the addition of air can also aid in the control of temperatures. Turning a
windrow has been shown to reduce the temperature by 5–10 degrees Celsius (9–18 degrees
Fahrenheit) (Haug 1980). Another consideration is that if aeration is insufficient, the pH of
the materials may drop, again potentially inhibiting the composting process. If the aeration of
the compost is not sufficient, malodorous sulfur compounds can be emitted, potentially
creating a nuisance. Additionally, anaerobic conditions may allow the formation of alcohols.
As little as 1 ppm of alcohol can kill plant cells (Lowenfels and Lewis 2006). Since compost
is often applied as a soil amendment, alcohol formation is of great importance, as the
compost is intended to provide nutrition to plants. (Lowenfels and Lewis 2006).
PARTICLE SIZE
Particle size is controlled in composting processes. Smaller particles increase the
bioavailability of the material. As discussed previously, carbon and nitrogen, as well as other
nutrients, must be made available to the microbial community in order for the waste to be

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degraded. It has been reported that a particle size of less than two inches is ideal for the
composting process (Haug 1980).
PH VARIABILITY
The pH may change throughout the composting process. Initially, the pH of organic
waste is typically between five and seven (Tchobanoglous, Theisen, and Vigil 1993). The pH
usually drops after the first few days and then begins to rise to approximately eight
throughout the aerobic process. As the materials cool, the pH can be expected to be in the
range of seven to eight. If the process becomes anaerobic, the pH will fall, impeding the
composting process (Tchobanoglous, Theisen, and Vigil 1993). Different microorganisms
prefer different pH ranges. The ideal pH for bacteria is from six to seven, while the ideal
range for fungi is from five and one-half to eight (Diaz, Savage, and Golueke 1994). The pH
will drop initially in the process due to the formation of organic acids by acid-forming
bacteria (Diaz, Savage, and Golueke 1994). Subsequently, other microbes will use these
acids as a substrate and the pH will begin to rise. Adjustment of the pH is not advised, as it
can cause a loss of nitrogen (Diaz, Savage, and Golueke 1994).
TEMPERATURE
The temperature of the compost is dynamic throughout the composting process. The
temperature of the compost materials is associated with microbial activity. Heat is generated
by the exothermic reactions associated with microbial metabolism (Haug 1980). It is
important to raise the temperature of the pile for a sufficient amount of time to destroy
pathogens as well as weed seeds. However, if the temperature rises above 60 degrees Celsius
(140 degrees Fahrenheit), the microorganisms may die or become dormant (Rynk et al.
1992).

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CHAPTER 3
PHASES OF COMPOSTING
Temperature is an important indicator for the three phases of the aerobic composting
process. These phases can be described as the mesophilic phase, thermophilic phase, and
curing phase. Different microbes are dominant depending on the phase of the composting
process. For the composting process to occur, microbes must be present to degrade the waste.
The microbes use the waste as a source of energy and as a carbon source, in the case of
organoheterotrophs (Haug 1980). There are many species of fungi and bacteria that play a
role in the composting process, including the subset of bacteria known as actinomycetes.
Macrobiota such as worms also play a role in the process (Rynk et al. 1992). It is important
to note that pathogenic species, such as Salmonella, and opportunist species, such as
Aspergillus fumigatus, may be present in some cases (Haug 1980).
MESOPHILIC PHASE
As soon as the proper combination of materials is placed together, the composting
process begins (Rynk et al. 1992). The temperature begins to increase as microbes degrade
the fresh waste. Additionally, larger organisms break down the waste as they search for and
break down food (Lowenfels and Lewis 2006). The most easily degraded compounds, such
as simple sugars, starches, celluloses, and amino acids, are broken down during this phase
(Lowenfels and Lewis 2006; Diaz, Savage, and Golueke 1994). Materials more difficult to
degrade begin to be broken down in this phase. Mesophilic species are dominant during this
initial phase.
THERMOPHILIC PHASE
As the temperature of the compost rises, mesophilic species are outcompeted by
thermophilic species. This second phase can be termed the active phase, as the majority of
the conversion and degradation of the materials occurs during this phase. Organisms in this
phase are able to withstand temperatures over 66 degrees Celsius (150 degrees Fahrenheit)
(Lowenfels and Lewis 2006). As the nutrients are exhausted, the temperature drops and the
composting process progresses to the final phase.

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CURING PHASE
The third phase of the process can be termed the curing phase. The temperatures
again favor mesophilic species. In this stage the degradation of the materials most difficult to
degrade is achieved. Cellulose, hemicellulose, chitin, and lignin are degraded (Lowenfels and
Lewis 2006). The waste eventually stabilizes into humus or compost. The material will
continue to degrade until all nutrients are exhausted and all of the carbon has been converted
to carbon dioxide (Rynk et al. 1992).

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CHAPTER 4
COMPOSTING FEEDSTOCK
Many different materials can be used as feedstock for the composting process.
Typical wastes used for composting are yard and green waste, food waste, paper waste, the
organic fraction of municipal solid waste (either source-separated or separated at the waste
management facility), and in some cases manure, digested wastewater sludge solids, or
carcasses. Feedstock may be sourced from restaurants, private residences, and agricultural
sources, among other sources (Landreth and Rebers 1997). Some feedstocks are higher in
nitrogen, while others are higher in carbon content. Different feedstocks are more likely to
release sulfurous or xenobiotic compounds. The feedstock characteristics must be considered
in designing a composting process. When composting material is properly aerated, carbon,
nitrogen, and sulfur present in the feedstock are converted to carbon dioxide, nitrate, and
sulfate, respectively (Kissel, Henry, and Harrison 1992).
FEEDSTOCK AS A CARBON SOURCE
Sources of carbon in compost exist as easily degraded carbohydrates and proteins,
and less easily degraded cellulose and hemicellulose, as well as the most recalcitrant sources,
lignin and other difficult-to-degrade organic molecules (Kissel, Henry, and Harrison 1992).
The primary byproducts of the conversion of organic matter are carbon dioxide and water.
According to Kissel, Henry, and Harrison (1992), typical mixed organic waste contains
slightly less than 50 percent carbon by weight, and approximately half of the carbon is
expected to be oxidized to carbon dioxide. The remaining portion of the carbon is expected to
exist as difficult-to-degrade materials, including humified lignin (Kissel, Henry, and Harrison
1992).
FEEDSTOCK AS A NITROGEN SOURCE
Several feedstocks are high in nitrogen. The nitrogen may exist in organic or
inorganic form; however, it typically exists in an organic form (Kissel, Henry, and Harrison
1992). Organic nitrogen is released from wastes via mineralization and via the nitrification
and denitrification processes. According to Kissel, Henry, and Harrison (1992), the release of

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nitrogen as ammonia is dependent on the C:N ratio. The release of nitrogen can be prevented
in two ways. First, ammonium formed as a product of mineralization can be oxidized to
nitrate (if oxygenation is sufficient). Second, if the C:N ratio is high, the conversion of
inorganic nitrogen to organic nitrogen is more prevalent than the release of ammonia, as the
microbial demand for the nitrogen is high (Kissel, Henry, and Harrison 1992).
FEEDSTOCK AS A SULFUR SOURCE
In typical feedstock, sulfur compounds exist primarily in organic forms, such as
proteins (Kissel, Henry, and Harrison 1992). In the presence of a sufficient level of oxygen,
mineralized organic sulfur can be oxidized to sulfate. The oxidation of sulfur compounds is
desirable, since reduced forms of sulfur tend to be malodorous. The intermediaries of carbon-
bonded sulfur mineralization by microorganisms are sulfides. Low carbon:sulfur (C:S) ratios,
as well as insufficient aeration, result in the increased release of volatile sulfur-containing
gases such as carbon disulfide, dimethyl sulfide, and dimethyl disulfide. Maintaining a high
C:S ratio allows carbon groups in the organic matter to bond the intermediary sulfides until
they can be oxidized to sulfates (Kissel, Henry, and Harrison 1992).

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CHAPTER 5
ADVANTAGES OF COMPOSTING
Composting has become a necessity in solid waste management. There are several
reasons that composting is becoming increasingly necessary. One of the main drivers is the
need to divert waste from landfills. Additionally, as the concern over global warming
increases, composting may afford an opportunity to reduce greenhouse gas (GHG) emissions.
The application of compost as a soil amendment provides additional benefits, such as the
prevention of runoff.
LANDFILL DIVERSION
CalRecycle reports that in 1990 approximately one-half of the counties in California
had less than 15 years of landfill space remaining (CalRecycle 2012). In response to the
projected diminishing landfill space, Assembly Bill (AB) 939 was drafted. AB 939 or the
Integrated Waste Management Act of 1989 required a diversion rate of 50 percent from
landfills by the year 2000 (California Environmental Protection Agency 2009). Landfill
diversion continues to be relevant today. According to the United States Census Bureau, the
world's population has now exceeded an estimated 7 billion and the United States population
exceeds an estimated 316 million (United States Census Bureau n.d.). According to the
United States Environmental Protection Agency, in the year 2011 Americans generated
approximately 250 million tons of trash. In the year 2011 Americans generated 4.40 pounds
of waste per day per capita and recycled and composted 1.53 pounds per day per capita, on
the average (U.S. Environmental Protection Agency 2013). California's population as of
2012 was estimated to be over 38 million, according to the U.S. Census Bureau (United
States Census Bureau 2013). As a continued response to the growing population and
associated solid waste issues, AB 341 was signed in 2011. This bill requires the state of
California to develop a policy to divert 75 percent of solid waste from landfills by 2020
(CalRecycle 2013).
Many states have landfill bans on some form of organic material. As of April 2013,
the U.S. Composting Council reports that the following states have some form of landfill ban
with regard to organics: Arkansas, Connecticut, Delaware, Florida, Georgia, Illinois, Indiana,

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Iowa, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, New Hampshire,
New Jersey, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, South
Dakota, West Virginia, and Wisconsin. Michigan is considering repealing its landfill ban,
while Vermont is considering the adoption of a new landfill ban. Florida and Georgia have
removed the ban on yard waste disposal for landfills that generate energy (U.S. Composting
Council 2013).
If there is no ban at the state level, local municipalities may implement bans. San
Diego County Code of Regulatory Ordinance Section 68.571 requires green waste recycling
(County of San Diego n.d.). According to the City of San Diego Environmental Services
Department, composting one ton of green waste saves more than three cubic yards of landfill
space (San Diego Department of Environmental Services n.d.). Thus, landfill diversion is one
of the main drivers of the need for composting.
COMPOSTING AND GREENHOUSE GAS EMISSIONS
Composting has been found to have a net benefit with regards to GHG emissions.
This is especially relevant with the passing of AB 32, which has the goal of reducing GHG
emissions to 1990 levels by 2020 and reducing emissions to 80 percent below 1990 levels by
2050 (California Air Resources Board n.d.).The United States Environmental Protection
Agency (USEPA), Region 10, released a report in May of 2011 entitled Reducing
Greenhouse Gas Emissions through Recycling and Composting, in which composting was
determined to reduce net GHG emissions. According to the report, "[d]iversion of food
scraps from landfills offers the greatest quantity of in-state GHG emissions reductions . . . the
emissions reduction potential of diverting one year’s worth of food scraps from landfills
through composting is equal to approximately 1.5 percent of California’s 2050 emissions
reduction goal, 0.8 percent of Oregon’s goal, and 1.8 percent of Washington’s goal"
(Material Management Workgroup of the West Coast Climate and Materials Management
Forum 2011). According to the report, “[f]ood scraps are responsible for a large share of
methane emissions generated by landfills” (Material Management Workgroup of the West
Coast Climate and Materials Management Forum 2011). The California Air Resources Board
(CARB) has developed a methodology for calculating a compost emission reduction factor
(CERF). Using this methodology, CARB estimates a CERF of 0.42 metric tons of CO2

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equivalent/ton of wet feedstock using California specific data (California Air Resources
Board 2011). The CERF is partially based on the estimated greenhouse gas emissions
reductions from “increased soil carbon storage, reduced soil erosion, reduced water use, and
a decrease in fertilizer and herbicide use.” The San Joaquin Valley Unified Air Pollution
Control District Final Staff Report: Proposed New Rule 4566 states that “[i]n comparison to
natural decay, bacterial activity in the conversion of material to compost provides a benefit
for reduction of global warming emissions by keeping carbon in the bacterial cell structure
thereby reducing the total amount of carbon escaping into the air” (Thao 2011).As GHG
emissions reductions are sought, composting will inevitably be encouraged.
BENEFITS OFTHE APPLICATION OF COMPOST AS A SOIL
AMENDMENT
Composting is beneficial not only for waste reduction and for GHG emissions
reduction but also for the prevention of runoff and for the reduction of the use of fertilizers.
Compost increases soil density and water holding capacity (Haug 1980). Fertilizer runoff is
known to contribute to eutrophication of water bodies. Compost provides nutrients and
beneficial microbes to the soil, reducing the need for fertilizers. This is another reason that as
the population increases and food demand increases, the demand for compost may also
increase.

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CHAPTER 6
DISADVANTAGES OF COMPOSTING
While composting affords many benefits to the environment and society, there are
some concerns that need to be considered as part of the design process, siting, and
management of composting facilities. One of these is the presence of pathogens. Many
pathogens may be present in the feedstock, and these pathogens may be emitted from
composting facilities. According to Haug (1980), one of the main functions of composting is
to destroy pathogens that were present in the feedstock. Another concern is the potential
emission of air contaminants, including VOCs.
PATHOGENS
Certain feedstocks may be more likely to contain pathogens. Many different
pathogens can be present in sewage. If sewage sludge solids are to be composted, special
care should be taken to ensure proper pathogen destruction. Potential pathogens include
bacteria, viruses, protozoa, and metazoa (Haug 1980). Examples of diseases that can be
caused by these microbes are cholera and salmonellosis, but many others can potentially
occur. Ascaris, which causes ascariasis, is often associated with sewage sludge (Haug 1980).
Sludge processing methods such as air drying and digestion are not expected to completely
destroy all pathogens in the sludge (Haug 1980).
FUNGAL OPPORTUNISTS
Fungal opportunists may also be present in compost. Opportunistic fungal species are
able to cause disease in humans under a certain set of conditions. Mycosis, or fungal
infection, can be either dermal or systemic. Of the two types of infection, systemic infections
are more serious. Infection typically occurs via inhalation or from introduction through
abrasions. Most attention is paid to the genus Aspergillus, since some of the species of this
genus cause aspergillosis. A. fumigatis has been detected in composting systems and may be
associated with cellulosic materials used for bulking agents (Haug 1980).

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EMISSIONS OF AIR CONTAMINANTS
Another disadvantage of the composting process is the potential for the emission of
air contaminants. Potential air contaminant emissions include emissions of ammonia,
particulate emissions, sulfurous emissions, and VOC emissions. While the emissions of
ammonia, particulate matter, and sulfurous compounds are well documented, the emissions
of VOCs are of primary interest for the scope of this work.
VOLATILE ORGANIC COMPOUNDS
VOCs are emitted during the composting process. The term "volatile organic
compound" is defined differently by different agencies. According to the San Diego Air
Pollution Control District (SDAPCD) Rule 2 (b)(50), volatile organic compound (VOC) “. . .
means any volatile compound containing at least one atom of carbon excluding carbon
monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, ammonium
carbonates, and exempt compounds.” The exempt compounds are also provided in SDAPCD
District Rule 2, Table 1 (County of San Diego: Air Pollution Control District 2009). The
emissions of VOCs are important to consider for different reasons. VOCs can present a
human health risk, contribute to the formation of ground-level ozone, and contribute to odor
nuisances.
Volatile Organic Compounds and Human Health
There are several VOCs that have been determined to be a risk to human health.
Health risks are usually evaluated in three different categories. VOCs can contribute to acute,
chronic, or cancer risks, or a combination of these risks. Some of the toxic VOCs that have
been identified in composting studies include benzene, toluene, ethylbenzene, xylene,
styrene, and naphthalene (Liu et al. 2009; Mao et al. 2006; Van Durme, McNamara, and
McGinley 1992; Eitzer 1995). Health risks are a concern, especially for the workers at
composting facilities, but also for the surrounding receptors, such as businesses and
residents. In California, the AB 1807 program requires human health risk identification and
management. The risk identification is done by CARB in conjunction with the Office of
Environmental Health Hazard Assessment (OEHHA). Together these agencies identify
compounds that are to be formally identified as toxic air contaminants (TACs). CARB then
reviews the emissions sources of a specific TAC and decides if regulatory action is required

15
in order to reduce the associated risk. The Clean Air Act requires that the EPA regulate the
emissions of hazardous air pollutants (HAP). AB 2728 required that CARB identify the
Federal HAP as TAC. Additionally, the AB2588 program requires facilities to report their
TAC emissions, determine the associated health risks, and notify residents near the facility of
any significant risk. Senate Bill (SB) 1731 modified AB2588 to also include the requirement
that risk reduction measures be in place if a significant risk is identified (California Air
Resources Board 2010) . Local agencies work in conjunction with CARB in order to mitigate
risks.
Font, Artola, and Sánchez (2011) conducted a review of the literature in order to
study the detection, composition, and treatment of VOCs from waste treatment plants. In
their work they reviewed two studies that considered the possible “negative effects on plant
workers and the nearby population.” Here the work of Vilavert et al. (2012), Nadal et al.
(2009), Eitzer (1995), and Domingo and Nadal (2009) are considered.
Vilavert et al. (2012) found that the hazard index (HI) for twelve sites located
between 300 and 900 meters from Ecoparc-2, an organic waste treatment facility, never
exceeded one. A risk of less than one is considered acceptable. This study found that the sum
of the excess cancer risks was slightly higher than 10-5. Vilavert et al. (2012) report that the
USEPA considers this an acceptable level of risk. The EPA has no set acceptable or
unacceptable regulatory threshold for air toxics. The 1989 Benzene National Standard for
Hazardous Air Pollutants (NESHAP) established a two-stage risk-based decision framework.
An upper limit of acceptability of a one in 10,000 lifetime cancer risk for highly exposed
individuals was set and a lower limit of an individual lifetime risk level no higher than
approximately one in 1,000,000 for the greatest number of persons possible was set (U.S.
Environmental Protection Agency 2010). The EPA’s superfund program considers an excess
lifetime cancer risk in the range of 10-4 (one in ten thousand) to 10-6 (one in one million) to
be acceptable (Fowle and Dearfield 2000). If the HI is above one, the site may be considered
for remedial action. However, the federal acceptable cancer risk may differ from what is
considered to be an acceptable level of risk at the local level. For example, in San Diego, a
maximum incremental cancer risk of less than one in one million is considered acceptable for
new facilities unless the facility is equipped with toxics best available control technology (T-
BACT) or the facility meets the requirements for a specified exemption (County of San

16
Diego: Air Pollution Control District 1996). Both the noncancer and cancer risks in this study
were driven by emissions of formaldehyde. It should be noted that Ecoparc-2 treats the
organic fraction of municipal solid waste (OFMSW) and green waste in addition to light
plastic containers.
Nadal et al. (2009) reported a total HI greater than one at two sites within Ecoparc-2.
The elevated HI was reportedly due to "especially high concentrations of toluene." A total
excess cancer risk above 10-4 was reported at three points within the treatment facility. The
risks were reported as 8.73E-04, 1.55E-04, and 1.39E-04. The elevated cancer risk of 8.73E-
04 was reported to be due primarily to exposure to ethylbenzene and tetrachloroethylene. It
should be noted that the HI and excess cancer risk reported are the result of summation of the
risks for each compound. The exposure was assumed to be occupational exposure. According
to Eitzer ,"workplace exposure limits are higher than outdoor ambient air exposure limits."
Eitzer (1995) found that the targeted VOC emissions that were analyzed were lower than the
workplace exposure limits set forth by the American Conference of Governmental Industrial
Hygienists (ACGIH). It should be noted that the exposure limits may have subsequently been
updated; however, the concentrations of compounds were below the ACGIH exposure
guidelines by several orders of magnitude, in most cases.
The Occupational Safety and Health Administration (OSHA) and the Division of
Occupational Safety and Health (DOSH) or (Cal/OSHA) have developed permissible
exposure levels for specific compounds. Cal/OSHA has also developed short-term exposure
levels for specific compounds (United States Department of Labor n.d.). In future studies, the
concentrations of specific compounds could be compared with the OSHA, Cal/OSHA, and
ACGIH published values.
Domingo and Nadal (2009) conducted a review of the human health risk associated
with domestic waste composting facilities. Among the risks associated with exposure to
VOC emissions are the risks of "indirect health effects" including nausea and vomiting. It is
important that these "indirect health effects" be considered, as the planning for expanded and
new composting facilities is expected to continue at an accelerated rate.
While Vilavert et al. (2012) suggested that the health risks from the studied
composting operation were acceptable, continued monitoring of Ecoparc-2 was
recommended, and it is advisable that other sites also conduct monitoring in California as

17
more stringent standards are put in place, especially for new facilities. Special care should be
taken to ensure the protection of staff at composting facilities. Continued monitoring will
allow the variations over time to be observed, and long-term patterns can be elucidated. In
addition, continued monitoring may allow the development of the public's confidence in the
safety of composting, which will be required if composting facilities are to continue to be
sited.
Volatile Organic Compounds and Odor Nuisance
Important to the public as well as those designing and siting composting facilities is
the potential for nuisance in the form of odorous emissions. While ammonia and hydrogen
sulfide contribute to the odor from composting facilities, VOCs also play a role. According to
Font, Artola, and Sánchez (2011), “the presence of odors is the main concern associated with
VOC emissions and it has been investigated by a wide number of researchers.” Font, Artola,
and Sánchez (2011) reviewed several studies that correlated VOC emissions and odor
nuisance. Presented in this work are the findings of Tsai et al. (2008), Schlegelmilch et al.
(2005), Kissel, Henry, and Harrison (1992), Büyüksönmez and Evans (2007), Van Durme et
al. (1992), and Muller et al. (2004). Tsai et al. (2008) found that six compounds emitted from
a food waste composting plant exceeded human olfactory thresholds. These compounds
included the following organic compounds: amines, dimethyl sulfide, acetic acid,
ethylbenzene, and p-cymene. Schlegelmilch et al. (2005) found that “critical odour
concentrations are released mainly during the first 2-3 weeks of the composting process.”
According to Kissel, Henry, and Harrison (1992), malodorous compounds are released
during the collection, transport, storage and turning of waste. The production of malodorous
compounds increases under anaerobic conditions. If oxygen is not available to be used by
microbes as an electron acceptor, microbial species that are able to use an alternate electron
acceptor may thrive in place of obligate aerobes. For example, sulfate can be used by some
bacteria as an electron acceptor. The reduction of sulfate can result in the emission of
malodorous organic sulfur compounds (Kissel, Henry, and Harrison 1992). Limonene and
alpha-pinene are released from the wood chips used as a bulking agent in many facilities, as
well as from plant wastes (Büyüksönmez and Evans 2007; Font, Artola, and Sánchez 2011;
Van Durme et al. 1992). These compounds have been demonstrated to contribute to odor.

18
According to Muller et al. (2004), "alpha-Pinene, Limonene, (+)-3-Carene, and Camphene, in
combination with 2-Heptanone, all occurring in certain ratios, is proposed to contribute to the
characteristic smell of the biowaste compost." The South Coast Air Quality Management
District (SCAQMD) reported in 2002 that within the previous two years over 3,000 nuisance
complaints associated with composting facilities were received by the District and other local
enforcement agencies (South Coast Air Quality Management District 2002).
Volatile Organic Compounds and Ground-Level
Ozone
Ground-level ozone formation is one of the primary concerns with regard to the
emissions of VOCs. When VOCs are emitted to the atmosphere, chemical reactions occur
with NOx in the presence of light to form ground-level ozone. Ozone contributes to human
health risks and is a criteria pollutant as defined by the Federal Clean Air Act (CAA).
The CAA requires that National Ambient Air Quality Standards (NAAQS) be set.
Two types of NAAQS are set, primary and secondary. Primary standards are intended to
protect human health, including the health of sensitive populations. Secondary standards are
set in order to protect property and visibility. The NAAQS for ozone is 0.075 ppm, annual
fourth highest daily maximum eight-hour concentration, averaged over 3 years (U.S.
Environmental Protection Agency 2012). The California Ambient Air Quality Standard
(CAAQS) is more stringent than the NAAQS. There are two CAAQS for ozone, a one-hour
standard and an eight-hour standard. The one-hour standard is 0.09 ppm, while the eight-hour
standard is 0.70 ppm (California Air Resources Board 2013). In order to ensure compliance
with NAAQs and CAAQs, local air districts enforce prohibitory or source-specific and new
source review rules that reduce and control stationary sources of precursor ozone emissions,
including VOCs.
Volatile Organic Compounds and California Local
Air District Rules
According to CalRecycle, in California, several local districts have adopted or plan to
adopt prohibitory or source-specific rules for composting operations. The districts include
Antelope Valley Air Pollution Control District (AVAPCD), San Joaquin Valley Air Pollution
Control District (SJVAPCD), and South Coast Air Quality Management District

19
(SCAQMD). The Mojave Desert Air Quality Management District (MDAQMD) had adopted
a composting rule; however, the rule was rescinded due to a legal challenge. According to the
Desert Dispatch, Judge John P. Vander Feer ordered that the MDAQMD conduct an
environmental impact report and cost–benefit analysis and subsequently revise the rule
(Cejnar 2009). Concern was expressed that SCAQMD and SJVAPCD had stricter rules that
could lead to a high concentration of composting facilities in the Mojave Desert district. The
South Cost rule requires that piles be covered, while San Joaquin's rule has stricter controls
for larger facilities. The following are brief summaries of the local rules. The summaries are
intended to explore the control measures required by the local districts and do not include all
of the requirements of each rule. Interested parties should refer to the rules directly, which
can be found on each local district website.
SOUTH COAST AIR QUALITY
MANAGEMENT DISTRICT
SCAQMD Rule 1133 requires that chipping, grinding, and composting facilities
register with the SCAQMD (South Coast Air Quality Management District 2003a).
SCAQMD Rule 1133.1 prohibits chipping and grinding facilities from accepting food waste
"unless otherwise allowed by the Local Enforcement Agency" (South Coast Air Quality
Management District 2011a). In addition, facilities are required to remove wastes within a
specified time frame (South Coast Air Quality Management District 2011a). SCAQMD Rule
1133.2 is designed to reduce emissions from co-composting operations. There are different
requirements for new versus existing co-composting facilities. New facilities are required to
enclose active composting operations. The rule sets out specific parameters for the enclosure.
In lieu of the enclosure, the site may choose to submit and obtain approval of a compliance
plan meeting the specifications of the rule. The plan must demonstrate a control efficiency of
at least 80 percent by weight of VOCs and 80 percent of ammonia emissions compared to the
"baseline emission factors" (South Coast Air Quality Management District 2003b). Existing
composting facilities are required to submit a similar plan that requires a 70 percent reduction
of VOC and 70 percent reduction of ammonia emissions compared to the "baseline emission
factors." SCAQMD Rule 1133.3 requires that facilities utilizing up to 20 percent manure, by
volume, or up to 5,000 tons per year of food waste cover active piles with finished compost
and requires that the compost pile not be turned for the first seven days of the active phase.

20
The rule requires that the piles have water applied to them six hours before turning, or water
may be applied during turning if a windrow turner is used that is equipped with water-
spraying technology. An approved alternative is allowable if the method is demonstrated to
have a VOC emissions reduction efficiency of 40 percent by weight and a reduction
efficiency for ammonia emissions of 20 percent by weight. If a facility processes more than
more than 5,000 tons of food waste per year, the facility is required to install a control device
with 80 percent removal efficiency by weight for VOCs and ammonia for all piles containing
more than 10 percent food waste (South Coast Air Quality Management District 2011b).
SAN JOAQUIN VALLEYAIR POLLUTION
CONTROL DISTRICT
The San Joaquin Valley Unified Air Pollution Control District Rule 4565 has two
classes of mitigation measures, Class One and Class Two. Depending on the size of the
facility, the facility will have to implement different numbers of Class One, Class Two, or
both Class One and Two mitigation measures. Class One mitigations include the following:
the facility must scrape or sweep areas such that material no greater than one inch is visible,
maintain an oxygen concentration of at least 5 percent by volume in the free air space of
active and curing compost piles, maintain a moisture content of active and curing piles
between 40 and 70 percent by weight, maintain active piles with a C:N ratio of at least 20:1,
cover active piles within 3 hours of each turning event with a waterproof covering or 6" of
soil or finished compost, or implement an alternative measure that achieves a 10 percent
reduction of VOCs by weight. Class Two mitigations include the following: aerated static
piles shall be vented to an emission control device with an efficiency of at least 80 percent by
weight, an in-vessel composting system with an efficiency of at least 80 percent by weight
shall be used, curing must be conducted in aerated static piles vented to a control device with
an efficiency of 80 percent by weight, curing shall be conducted in an in-vessel composting
system vented to a control device with a VOC control efficiency of at least 80 percent by
weight, or an alternative measure shall be implemented which reduces VOC emissions by 80
percent by weight. Facilities with a throughput of less than 20,000 tons of wet waste per year
must implement either three Class One mitigation measures or two Class One mitigation
measures and one Class Two mitigation measure for active composting. Facilities with a
throughput between 20,000 and 100,000 wet tons per year must implement either four Class

21
One mitigation measures or three Class One mitigation measures and one Class Two
mitigation measure for active composting. Facilities with a throughput of more than 100,000
wet tons per year must implement either four Class One mitigation measures and one Class
Two mitigation measure for active composting piles or two Class One mitigation measures
and one Class Two mitigation measure for active composting piles and one Class Two
mitigation measure for curing piles (San Joaquin Valley Air Pollution Control District 2007).
The San Joaquin Valley Unified Air Pollution Control District Rule 4566 requires
subject facilities with a throughput of less than 100,000 wet tons per year to either remove
organic material, start the active phase of composting, cover the material in a specific
manner, or implement an approved alternative within 10 days of receipt of organic material.
If the facility has a throughput greater than or equal to 100,000 wet tons per year, the facility
must take the above listed action within three days of receipt of organic material. Facilities
with a throughput of less than 200,000 wet tons per year of organic material must either
“implement at least three turns during the active phase and one of the mitigation measures for
the Watering Systems in Table 1 [of Rule 4566]” (San Joaquin Valley Air Pollution Control
District 2011) or implement an alternative approved measure that reduces VOC emissions by
19 percent, by weight. Facilities with a throughput greater than or equal to 200,000 but less
than 750,000 wet tons per year of organic material must either conduct at least three turns
during the active phase, apply water as specified in Table 1 of the rule, and cover the
compost as described in Table 1 of the rule, or implement an approved alternative mitigation
measure that reduces VOC emissions by 60 percent by weight. Any facility with a
throughput greater than or equal to 750,000 wet tons per year of organic material must reduce
its VOC emissions by 80 percent by weight by means of an approved mitigation measure.
ANTELOPE VALLEYAIR POLLUTION
CONTROL DISTRICT
The Antelope Valley Rule has three key requirements. First, the rule requires that
chipping, grinding, and composting facilities register with the AVAPCD. Second, chipping
and grinding operations are required to remove different materials from the site within
different specified amounts of time. The third and most complex requirement is applicable to
co-composting facilities. The rule defines co-composting as “[c]omposting where Biosolids
and/or Manure are mixed with Bulking Agents to produce Compost. Co-Composting

22
involves both the active and curing phase” (Antelope Valley AQMD 2009). The third
requirement requires co-composting sites to operate within specific limits. The rule requires
that the site maintain a C:N ratio of not less than 20:1 for active compost piles. The site is
required to maintain a moisture content between 40 and 70 percent or cover active and curing
piles within 3 hours of turning with either a waterproof covering or 6” or more of soil or
compost. The site is also required to maintain a pH below 8.0 in active and curing piles.
Incoming feedstock is required to be mixed in order to maintain proper proportions in all
parts of the compost pile. The facility is also required to scrape or sweep once daily where
compost is mixed, screened, or stored so that materials no greater than 1” in height are
visible.
Particulate Matter and Nuisance Rules
While not all local districts in California have specific prohibitory or source specific
rules, local districts may have particulate matter and nuisance rules. An example of a
nuisance rule is the San Diego Air Pollution Control District's (1969) Rule 51.
RULE 51. NUISANCE (Effective 1/1/69)
A person shall not discharge from any source whatsoever such quantities of air
contaminants or other material which cause injury, detriment, nuisance or
annoyance to any considerable number of persons or to the public or which
endanger the comfort, repose, health or safety of any such persons or the public or
which cause or have a natural tendency to cause injury or damage to business or
property. The provisions of this rule do not apply to odors emanating from
agricultural operations in the growing of crops or raising of fowls or animals.
Additionally, in San Diego, as in other local Districts, sources of air contaminants not
specifically exempted from permitting are required to obtain a permit, even if a prohibitory
rule does not exist for a specific source.
Composting Volatile Organic Compound Emissions
Sources
The VOCs typically found in composting emissions include aromatics, ketones,
aldehydes, hydrocarbons, volatile fatty acids, esters, terpenes, and alcohols. Pierucci et al.
(2005) studied the emissions from undifferentiated MSW and found that the most important
emissions were of terpenes, monocyclic arenes, alkanes, halogenated compounds, and esters.
Defoer et al. (2002) studied the emissions from four vegetable fruit and garden (VFG)

23
composting operations as well as the emissions from a rendering plant. The most significant
emissions that occurred were terpenes (65 percent of the total VOC emissions). Ketones,
hydrocarbons, alcohols, esters, aldehydes, and sulfur compounds were also detected (Defoer
et al. 2002). There are different sources of VOC emissions from composting. The waste itself
may be the source of the VOC emissions, the VOC emissions may result from microbes, or
the VOC emissions may occur from cross contamination from other waste materials.
Different types of VOCs can be expected to be found from different types of waste.
BIOGENIC VOLATILE ORGANIC
COMPOUNDS
The waste itself may be the source of VOCs. In many cases composting is conducted
with green wastes, including plant trimmings. Vegetation has been demonstrated to emit
several VOCs. In 2008, CARB estimated that biogenic emissions accounted for 2226.2 tons
per day of reactive organic gases (ROGs). The total of all ROGs was estimated to be 4440.7
tons per day (California Air Resources Board 2009a). Therefore, biogenic emissions
accounted for approximately 50.13 percent of the total ROG emissions on a daily basis, as
reported in 2008. In a study conducted by Büyüksönmez and Evans (2007), emissions from
composted materials were compared to the emissions from the same materials that were
allowed to decay on their own. The study found that composted materials emitted less VOCs.
The VOC emissions reduction ranged from 60 to 92 percent, depending on the type of
material and how it was blended. The study authors attribute the emissions reductions to the
biodegradation of VOCs due to the activity of microbes associated with the composting
process. Biogenic emissions from these materials ranged from 11.0 to 347.7 mg/kg dry
weight as alpha-pinene. Composted materials resulted in emissions ranging from 18.1 to
106.6 mg/kg dry weight as alpha-pinene. It was noted that emissions from prunings and grass
clippings primarily occurred during the first two weeks of the study. Wood chips emitted
VOCs throughout the study and continued to emit at even as the study ended. Primarily
terpenes were emitted. Alpha-pinene, beta-pinene, 3-carene, camphene, beta-myrcene, and d-
limonene were found to compose 32.7–95.3 percent of the total VOC emissions
(Büyüksönmez and Evans 2007).

24
VEGETATION ASA SOURCE OF VOLATILE
ORGANIC COMPOUNDS
The predominant emissions from vegetation are terpenes. Most of the plants that emit
terpenes belong to the families Coniferae and Myrtaceae and the genus Citrus (Manahan
1991). Common terpenes emitted from plants include alpha-pinene, beta-pinene, limonene,
myrcene, and alpha-terpinene (Manahan 1991). Plants also emit esters, but the emissions are
not as significant as those of terpenes (Manahan 1991). Brilli et al. (2012) report that
mechanical wounding of plants releases biogenic volatile organic compounds. Volatiles
commonly associated with plant wounding include "C6-alcohols, C6-aldehydes, acetate
esters, methanol, and acetaldehyde, as well as products of isoprene oxidation, especially
methacrolein and methyl vinyl ketone" (Brilli et al. 2012).
MICROBIAL VOLATILE ORGANIC
COMPOUNDS
Many different compounds are emitted by microorganisms; these compounds are
termed microbial volatile organic compounds (MVOCs). Fischer et al. (1999) studied
thirteen fungal species that have been isolated from composting plants. Many VOCs were
identified as being emitted from these fungi. The VOCs emitted depended on the species
studied. Over 100 compounds were identified. The classes of VOCs determined included
esters, ethers, aldehydes, ketones, terpenes and terpene-like compounds, alcohols, alkanes,
alkenes, and cycloalkanes. Muller et al. (2004) studied three different composting facilities.
Muller et al. (2004) found that microbial VOCs (MVOCs) accounted for as little as 2 percent
and as much as 14 percent of the targeted VOC emissions, on the average. Muller et al.
(2004) found that the "MVOC ratio ranged above 10 percent when the process of composting
was carried out in a relatively short time and the substratum was rich in carbohydrates."
When only plant debris was composted, fewer MVOCs were emitted. Muller et al. (2004)
attribute this difference to fact that the "phase of rotting is longer due to relatively low
microbial activity in combination with a complex substratum (e.g. wood)."

25
XENOBIOTIC SOURCES OF VOLATILE
ORGANIC COMPOUNDS
Many household products contain VOCs. If these products come into contact with
waste that is to be composted, it is possible that the waste to be composted can be
contaminated with VOCs. Household products containing VOCs include "cosmetics,
cleaning products, polishes, waxes, paints, pesticides, and auto maintenance products"
(Brown, Thomas, and Whitney 1997). Release of VOCs from household products could
occur due to the crushing or breakage of a household product container at some point in
municipal solid waste processing (Brown, Thomas, and Whitney 1997). Acetone, alcohols,
benzene, carbon tetrachloride, cresol, formaldehyde, naphthalene, phenols, toluene
trichloroethylene, xylene, etc. may all be emitted from household products (Brown, Thomas,
and Whitney 1997). Brown, Thomas, and Whitney (1997) found that most of the VOCs that
were added to synthetic municipal solid waste were lost due to volatilization within the first
48 hours of the process. The design of their study was an attempt to simulate the rupture of a
VOC- or pesticide-containing container in refuse and what effect this would have on the
initiation of composting in a ventilated static pile. Biodegradation of the VOCs was
considered limited, since most of the VOCs was volatilized in a short period of time. The rate
at which the VOCs were lost was proportional to the vapor pressure of each VOC. Kissel,
Henry, and Harrison (1992) reported that the organic material present in compost may act as
a sorbent for VOCs and that there may be a potential for the VOCs to be oxidized via the
composting process. While Brown, Thomas, and Whitney (1997) found that the VOCs were
lost from the synthetic compost, the two pesticides that were used to spike the synthetic
compost were not lost. Both Captan and Lindane remained in the compost matrix.
MAGNITUDE OF VOLATILE ORGANIC
COMPOUND EMISSIONS FROM COMPOSTING
FACILITIES
The total statewide ROG emissions estimate for 2008 was 4440.7 tons per day.
Therefore, c The California Air Resources Board (CARB) estimated in 2008 that composting
emissions were 38.02 tons of reactive organic gases (ROGs) per day (California Air
Resources Board 2009b). Composting emissions equated to approximately 0.86 percent of
the total ROG emissions, including the emissions from natural and mobile sources. If natural

26
and mobile sources are excluded, and only stationary sources are considered, the total ROG
emissions were 427.6 tons per day (California Air Resources Board 2009a). This would
equate to composting emissions making up approximately 8.89 percent of the total ROG
emissions for stationary sources in 2008.
Not all of the compounds emitted by composting are highly reactive. Kumar et al.
(2011) studied the emissions from two compost facilities. Collectively, these facilities
handled urban green waste, farm waste, and food waste. The study found that most of the
VOCs emitted were not highly reactive; more than 60 percent of the total VOC emissions
had reactivity in the range of 0.5–1 g-O3 g-VOC-1 (Kumar et al. 2011).
Font, Artola, and Sánchez (2011) reviewed the work of several authors that have
reported the magnitude of VOC emissions from composting operations. In this work the
findings of Cadena et al. (2009), Büyüksönmez (2012), and Colon et al. (2012) are presented
in addition to the emission factors documented in SJAPCD Rule 4565 and 4566, as well as
those reported in SCAQMD Rules 1133.2 and 1133.3.
Cadena et al. (2009) determined the total VOC emissions and developed emission
factors for a composting plant. The VOC emission factors were determined to be 0.21 kg per
Mg of OFMSW, also reported as 0.82 kg VOC per Mg of dry matter. Büyüksönmez (2012)
studied the VOC emissions from the Modesto composting facility. Both green waste and
food waste windrows were tested. The food waste windrows contained green waste mixed
with 15 percent food waste. The total emission factors developed were 1.4 g/kg-dry weight
for green waste composting and 2.2 g/kg-dry weight for food waste composting. Colon et al.
(2012) studied four waste treatment plants. Each site utilized a different treatment method.
One site used confined windrow composting, one used in-vessel composting, one used
anaerobic digestion combined with composting, and one used turned windrows. In addition,
home composting was evaluated. The in-vessel and anaerobic digestion processes were
equipped with wet scrubbers and biofilters. VOC emissions were determined to be 0.36 kg
VOCs per Mg of OFMSW for the in-vessel system, 6.22 for the confined windrows, 0.86 for
the combined anaerobic process, 5.70 for turned windrows, and 0.56 for home composting.
All processes used either wood chips or pruning wastes as bulking agents at different ratios.
The in-vessel process used a bulking agent:waste ratio of 1:2, the confined windrow process
used 2:3, the anaerobic process used a ratio of 4:1, the turned windrow process used a ratio of

27
1:2, and finally the home composting process used a ratio of 1:1.3. Table 1 provides a
summary of the findings above. The emission factors used by SCAQMD and SJAPCD are
presented in Table 2.
Table 1. Summary of the Magnitude of VOC Emissions from SelectedStudies
Waste Type
VOC
Emissions Units Source
OFMSW 0.21 kg/Mg-OFMSW Cadena et al. 2009
OFMSW 0.82 kg/Mg-dry matter Cadena et al. 2009
Green Waste 1.4 2.2 g/kg-dry weight Büyüksönmez 2012
Food Waste 2.2 2.2 g/kg-dry weight Büyüksönmez 2012
OFMSW 0.36 kg/Mg-OFMSW Colon et al. 2012
Factors Affecting Volatile Organic Compound
Emissions
VOC emissions depend on several factors including: the feedstock used, the phase of
the composting process in which measurements are taken, the aeration rate, the C:N ratio,
and the moisture content. Studies have been conducted in an effort to determine which
control parameters can be altered in order to reduce emissions of VOCs. With continued
research if may be possible to develop improved best management practices for composting
facilities based on the control of these parameters.
FEEDSTOCK ANDVOLATILE ORGANIC
COMPOUND EMISSIONS
The species and magnitude of VOC emissions depend on the feedstock. This is
demonstrated in the work of Komilis, Ham, and Park (2004), a study of different blends of
material that found great variation. Wastes taken from a composting facility emitted

28
primarily aromatic hydrocarbons, terpenes, and ketones. Komilis, Ham, and Park (2004)
added seed from a composting facility to some materials and not others. Unseeded mixed
paper waste emitted aromatic hydrocarbons and alkanes in the highest amounts. Seeded
Table 2. South Coast and San Joaquin District VOC Emission Factors
Waste Type
VOC
Emission
Factor Units District Associated Rule
Green Waste Stockpile 5.36 lb/wet ton San Joaquin Rule 4566
Green Waste Windrow 4.27 lb/wet ton San Joaquin Rule 4566
Food Waste Stockpile 5.36 lb/wet ton San Joaquin Rule 4566
Food Waste Windrow 4.27 lb/wet ton San Joaquin Rule 4566
Co-Composting Animal
Manure/Poultry Litter 1.78 lb/wet ton San Joaquin Rule 4565
Co-Composting Biosolids 1.78 lb/wet ton San Joaquin Rule 4565
Co-Composting
Operations 1.78 lb/ ton throughput South Coast Rule 1133.2
Green Waste (Active
Phase) 4.25 lb/ ton throughput South Coast Rule 1133.3
Source: San Joaquin Valley Air Pollution Control District. "SSP2050." Last modified September 9, 2009.
http://www.valleyair.org/policies_per/policies/ssp2050.doc.; South Coast Air Quality Management
District. "Rule 1133.2." Last modified January 10, 2003b. http://aqmd.gov/rules/reg/reg11/r1133-
2.pdf.; South Coast Air Quality Management District. "Rule 1133.3." Last modifed July 8, 2011b.
http://aqmd.gov/rules/reg/reg11/r1133-3.pdf.
mixed paper waste emitted mostly alcohols. Komilis, Ham, and Park (2004) hypothesized
that alcohols are due to microbiological activity, while xenobiotic VOCs occur from the
paper matrix itself. Terpenes were the most prevalent emissions from yard waste, followed
by aromatic hydrocarbons, ketones, and alkanes. This correlates to findings by Büyüksönmez
and Evans (2007) that demonstrated terpenes to be the dominant emissions from wood chips,
prunings, and grass clippings. Unseeded food wastes emitted sulfides, acids/esters, alcohols,
and terpenes, while seeded food wastes emitted mostly aromatic hydrocarbons. Komilis,
Ham, and Park (2004) postulate that xenobiotic VOCs in food waste may originate from
pesticides, from atmospheric deposition, or as a product of a reaction from cooking. Another
example can be found in the work of Pagans, Font, and Sánchez (2007). Their study

29
determined the VOC and ammonia emissions and the subsequent removal efficiencies for
VOCs and ammonia via the use of a biofilter in a laboratory-scale composting operation. The
study used two types of waste source—selected OFMSW and animal by-products (AP).
Chopped pruning waste was used as a bulking agent. Two treatments of OFMSW were
studied, one mixed at 5:1 bulking agent:OFMSW by volume and one mixed at 1:1 by
volume. AP was mixed at 3:1. The study found that the emissions of VOCs depended on the
type of waste composted. The VOC concentration ranged from 50 to 695 mg[C]m-3 for
OFMSW (5:1) and ranged from 13 to 190 mg[C]m-3 for OFMSW (1:1). The VOC
concentration of AP was found to be from 50 to 465 mg[C]m-3.
PHASES OFTHE COMPOSTING PROCESSAND
THE EMISSIONS OF VOLATILE ORGANIC
COMPOUNDS
VOC emissions have been documented to occur primarily in the first phases of the
composting process. Font, Artola, and Sánchez (2011) explored the correlation between the
concentration of VOCs emitted and the progression of the composting process in their review
of the literature. In their review, they reported correlations explored by Eitzer (1995) and
Pagans, Font, and Sánchez (2006) among others. Here the findings associated with the
emissions of VOCs and the progression of the composting process documented by Eitzer
(1995), Pagans, Font, and Sánchez (2006), Büyüksönmez and Evans (2007), Delgado-
Rodriguez et al. (2011; 2012) , and Kumar et al. (2011) are presented. Eitzer (1995) found
that the greatest concentration of VOCs occurred "in the tipping piles, near the shredders, and
in the fresh active composting region” (Eitzer 1995). Büyüksönmez and Evans (2007) found
that most of the VOC emissions occurred during the first two weeks, but noted that wood
chips continued to emit VOCs throughout their study. Pagans, Font, and Sánchez (2006)
found that the maximum VOC concentrations from the emissions associated with composting
OFMSW occurred within the first 20 hours of composting. Delgado-Rodriguez et al. (2011;
2012) also reported that the highest emissions of VOCs were occurred early in the
composting process. The nature of the VOCs may change throughout the composting
process. For example, Kumar et al. (2011) found that the flux from three- to six-day-old
compost windrows was 85 percent alcohol, while two- to three-week-old compost piles had a
flux of 66 percent alcohol. Kumar et al. (2011) also found that the emissions from the fresh

30
tipping piles were similar to those of the older compost windrows, with a flux of 70 percent
alcohol.
CONTROL PARAMETERSAND VOLATILE
ORGANIC COMPOUND EMISSIONS
Font, Artola, and Sánchez (2011) explored the control of process parameters and the
association with the emissions of VOC in their review of the literature. In this work, the
findings of Delgado-Rodriguez et al. (2011; 2012) and Büyüksönmez (2012) are presented.
Delgado-Rodriguez et al. (2012) studied the effect of varied aeration rates on the
evolution of VOCs from compost. Their study reports that "the aeration rate had a strong
effect on VOCs emissions." They found that high aeration rates led to higher emissions of
VOCs. Low aeration rates, however, led to anaerobic conditions and the formation of organic
sulfur compounds. Delgado-Rodriguez et al. (2012) suggest that an aeration rate of 0.175
L(air) kg-1min-1 may be ideal. Delgado-Rodriguez et al. (2011) found that a higher aeration
rate caused higher VOC emissions. Büyüksönmez (2012) observed that emissions increased
during turning. The author reports that on the average the VOC emissions doubled
subsequent to the turning event.
Delgado-Rodriguez et al. (2011) found that a high C:N ratio led to lower emissions of
most of the VOCs studied, with the exception of undecane and 2-butanone. Delgado-
Rodriguez et al. (2011) concluded that a high C:N ratio may be a "suitable selection" to
minimize VOC emissions.
Moisture content can have an effect on VOC emissions. Delgado-Rodriguez et al.
(2011) found that moisture content had both a positive and a negative effect on VOC
emissions. Delgado-Rodriguez et al. (2012) found that the effect of the moisture content
varied depending on the volatile compound; therefore they suggested a "medium moisture
value (55 percent)."
REVIEWOF SELECTED STUDIES
Font, Artola, and Sánchez (2011) reviewed several studies and presented the
summary of those studies in table format. In this work, in order to review what types of
VOCs are emitted during the composting process, six studies were selected for review. The
following studies are described in brief, and the results of the sampling conducted are

31
presented in Table 3, which is similar to that presented in the work of Font, Artola, and
Sánchez (2011). Collectively, over 100 compounds were detected from composting
emissions. Terpenes were detected in each of the studies. Dimethyl disulfide and/or dimethyl
sulfide were reported by all of the studies, with the exception of Eitzer (1995), who evaluated
a selection of compounds that did not include these two compounds. As Eitzer (1995) stated,
“[i]t is likely that there are a number of other unidentified VOCs present at composting
facilities (such as aldehydes, organic acids, organic sulfur compounds, etc.), but these
Table 3. Compounds Identified in SelectedStudies
Compound Concentration Units Source
Acetaldehyde 60 μg/m3 Van Durme, McNamara, McGinley 1992
Acetic acid 612 μg/m3 Mao et al. 2006
Acetic acid 2 574 μg/m3 Van Durme, McNamara, McGinley 1992
Acetone 114 mg/m3 Smet, Van Langenhove, and De Bo 1999
Acetone 25 μg/m3 Van Durme, McNamara, McGinley 1992
Acetone 443 μg/m3 Mao et al. 2006
Acetone 500 μg/m3 Mao et al. 2006
Acetone 166 000 μg/m3 Eitzer 1995
Benzene 1.23 μg/m3 Liu et al. 2009 (Day 15)
Benzene 3 μg/m3 Mao et al. 2006
Benzene 56 μg/m3 Mao et al. 2006
Benzene 104 μg/m3 Van Durme, McNamara, McGinley 1992
Benzene 700 μg/m3 Eitzer 1995
Borneol 508 ng/m3 Muller et al. 2004
Borneol 1 786 ng/m3 Muller et al. 2004
Borneol 6 936 ng/m3 Muller et al. 2004
Bornyl acetate 320 ng/m3 Muller et al. 2004
Bornyl acetate 1 342 ng/m3 Muller et al. 2004
Bornyl acetate 1 836 ng/m3 Muller et al. 2004

32
1,3-Butadiene 0.31 μg/m3 Liu et al. 2009 (Day 12)
2-Butanol 15 mg/m3 Smet, Van Langenhove, and De Bo 1999
2-Butanone 320 000 μg/m3 Eitzer 1995
Butanone 61 mg/m3 Smet, Van Langenhove, and De Bo 1999
Butanone 30 μg/m3 Mao et al. 2006
Butanone 45 μg/m3 Mao et al. 2006
cis-2-Butene 4.30 μg/m3 Liu et al. 2009 (Day 15)
(table continues)
Table 3. (continued)
trans-2-Butene 1.36 μg/m3 Liu et al. 2009 (Day 15)
n-Butylbenzene 210 μg/m3 Eitzer 1995
sec-Butylbenzene 220 μg/m3 Eitzer 1995
Camphene 1 070 ng/m3 Muller et al. 2004
Camphene 1 200 μg/m3 Eitzer 1995
Camphor 1 884 ng/m3 Muller et al. 2004
Carbon disulfide 0.4 mg/m3 Smet, Van Langenhove, and De Bo 1999
Carbon disulfide 1.46 μg/m3 Liu et al. 2009 (Day 15)

33
Carbon disulfide 150 μg/m3 Eitzer 1995
Carbon disulfide 224 μg/m3 Van Durme, McNamara, McGinley 1992
Carbon tetrachloride 290 μg/m3 Eitzer 1995
(+)-3-Carene 1 025 ng/m3 Muller et al. 2004
3-Carene 570 μg/m3 Eitzer 1995
beta-Caryophyllene 404 ng/m3 Muller et al. 2004
beta-Caryophyllene 581 ng/m3 Muller et al. 2004
beta-Caryophyllene 4 058 ng/m3 Muller et al. 2004
Chlorobenzene 9 μg/m3 Van Durme, McNamara, McGinley 1992
Chlorobenzene 29 μg/m3 Eitzer 1995
Chloroform 54 μg/m3 Eitzer 1995
4-Chlorotoluene 240 μg/m3 Eitzer 1995
Cyclohexane 4.51 μg/m3 Liu et al. 2009 (Day 12)
(table continues)
Cyclohexane 327 μg/m3 Van Durme, McNamara, McGinley 1992
Cyclohexanone 13 μg/m3 Van Durme, McNamara, McGinley 1992
Cyclopentane 442 μg/m3 Van Durme, McNamara, McGinley 1992
p-Cymene 3.4 mg/m3 Smet, Van Langenhove, and De Bo 1999
p-Cymene 49 μg/m3 Mao et al. 2006
p-Cymene 63 μg/m3 Mao et al. 2006
n-Decane 69.06 μg/m3 Liu et al. 2009 (Day 15)
n-Decane 1 060.96 μg/m3 Liu et al. 2009 (Day 3)

34
n-Decane 1 065.09 μg/m3 Liu et al. 2009 (Day 6)
1,2-Dichlorobenzene 1 μg/m3 Eitzer 1995
1,3-Dichlorobenzene 2 μg/m3 Eitzer 1995
1,4-DichIorobenzene 90 μg/m3 Eitzer 1995
Dichlorobenzene 9 μg/m3 Van Durme, McNamara, McGinley 1992
1,2-Dichloroethane 2 μg/m3 Eitzer 1995
1,l-Dichloroethane 1 μg/m3 Eitzer 1995
1,2-Diethylbenzene 1.04 μg/m3 Liu et al. 2009 (Day 15)
Diethyl ether 0.5 mg/m3 Smet, Van Langenhove, and De Bo 1999
Dimethyl disulfide 0.8 mg/m3 Smet, Van Langenhove, and De Bo 1999
Dimethyl disulfide 111 ng/m3 Muller et al. 2004
Dimethyl disulfide 156 ng/m3 Muller et al. 2004
(table continues)
Dimethyl disulfide 1 753 ng/m3 Muller et al. 2004
Dimethyl disulfide 9.35 μg/m3 Liu et al. 2009 (Day 15)

35
Dimethyl disulfide 860 μg/m3
Van Durme, McNamara, McGinley 1992
(6/27/90)
Dimethyl disulfide 956 μg/m3 Van Durme, McNamara, McGinley 1992 (10/89)
Dimethyl disulfide 1 311 μg/m3
(6/26/90)
2,3-Dimethylpentane 1.14 μg/m3 Liu et al. 2009 (Day 15)
Dimethyl sulfide 8.2 mg/m3 Smet, Van Langenhove, and De Bo 1999
Dimethyl sulfide 1 760 ng/m3 Muller et al. 2004
Dimethyl sulfide 2.12 μg/m3 Liu et al. 2009 (Day 6)
Dimethyl sulfide 759 μg/m3 Mao et al. 2006
Dimethyl sulfide 1 360 μg/m3
(6/27/90)
Dimethyl sulfide 2 667 μg/m3
(6/26/90)
Ethanol 194 mg/m3 Smet, Van Langenhove, and De Bo 1999
2-Ethoxyethanol 9 μg/m3 Van Durme, McNamara, McGinley 1992
Ethyl acetate 66 mg/m3 Smet, Van Langenhove, and De Bo 1999
Ethyl acetate 9 μg/m3 Mao et al. 2006
Ethylbenzene 6 μg/m3 Mao et al. 2006
Ethylbenzene 16 μg/m3 Van Durme, McNamara, McGinley 1992
Ethylbenzene 29 μg/m3 Mao et al. 2006
Ethylbenzene 1 190.67 μg/m3 Liu et al. 2009 (Day 15)

36
(table continues)
Ethylbenzene 178 000 μg/m3 Eitzer 1995
2-Ethylfuran 4 mg/m3 Smet, Van Langenhove, and De Bo 1999
2-Ethylfuran 78 ng/m3 Muller et al. 2004
2-Ethylfuran 1 028 ng/m3 Muller et al. 2004
m-Ethyltoluene 38.67 μg/m3 Liu et al. 2009 (Day 15)
o-Ethyltoluene 9.32 μg/m3 Liu et al. 2009 (Day 15)
p-Ethyltoluene 36.59 μg/m3 Liu et al. 2009 (Day 15)
Fluorotrichloromethane 1 493 μg/m3 Van Durme, McNamara, McGinley 1992
Furan-3-aldehyde 241 ng/m3 Muller et al. 2004
Heptane 3.7 μg/m3 Liu et al. 2009 (Day 15)

37
Heptane 39 μg/m3 Van Durme, McNamara, McGinley 1992
2-Heptanone 2.4 mg/m3 Smet, Van Langenhove, and De Bo 1999
2-Heptanone 214 ng/m3 Muller et al. 2004
2-Heptanone 1 948 ng/m3 Muller et al. 2004
2-Heptanone 2 888 ng/m3 Muller et al. 2004
Heptanone 46 μg/m3 Van Durme, McNamara, McGinley 1992
(table continues)
Hexachlorobutadiene 4 μg/m3 Eitzer 1995
Hexane 0.32 μg/m3 Liu et al. 2009 (Day 15)
2-Hexanone 6 600 μg/m3 Eitzer 1995
Hexene 28 μg/m3 Mao et al. 2006
Hexene 55 μg/m3 Mao et al. 2006
Isobutanol 15 mg/m3 Smet, Van Langenhove, and De Bo 1999
Isopropylbenzene 370 μg/m3 Eitzer 1995
p-Isopropyl toluene 4 800 μg/m3 Eitzer 1995
d-Limonene 10 100 μg/m3 Eitzer 1995
Limonene 57 mg/m3 Smet, Van Langenhove, and De Bo 1999
Limonene 11 768 ng/m3 Muller et al. 2004
Limonene 45 μg/m3 Van Durme, McNamara, McGinley 1992 (10/89)
Limonene 240 μg/m3 Mao et al. 2006
Limonene 368 μg/m3 Mao et al. 2006
Limonene 480 μg/m3
(6/27/90)
Limonene 2 667 μg/m3
(6/26/90)

38
Linalool 1 162 ng/m3 Muller et al. 2004
Longifolene 954 ng/m3 Muller et al. 2004
Longifolene 1 708 ng/m3 Muller et al. 2004
Longifolene 4 159 ng/m3 Muller et al. 2004
Methanol 153 μg/m3 Van Durme, McNamara, McGinley 1992
Methyl acetate 24 mg/m3 Smet, Van Langenhove, and De Bo 1999
Methyl acetate 4 μg/m3 Mao et al. 2006
Methyl acetate 16 μg/m3 Mao et al. 2006
Methyl acetate 144 μg/m3 Van Durme, McNamara, McGinley 1992
2-Methyl-l-butanol 675 ng/m3 Muller et al. 2004
2-Methyl-l-butanol 889 ng/m3 Muller et al. 2004
2-Methyl-l-butanol 7 637 ng/m3 Muller et al. 2004
3-Methylbutanal 4 mg/m3 Smet, Van Langenhove, and De Bo 1999
(table continues)
2-Methyl-1-butene 1.91 μg/m3 Liu et al. 2009 (Day 12)
Methyl chloride 16 μg/m3 Van Durme, McNamara, McGinley 1992
Methyl-cyclohexane 3.75 μg/m3 Liu et al. 2009 (Day 9)
Methyl-cyclohexane 3.87 μg/m3 Liu et al. 2009 (Day 12)
Methyl-cyclopentane 2.57 μg/m3 Liu et al. 2009 (Day 9)
Methyl-cyclopentane 17.87 μg/m3 Liu et al. 2009 (Day 3)

39
Methylene chloride 260 μg/m3 Eitzer 1995
Methyl ethyl ketone 974 μg/m3 Van Durme, McNamara, McGinley 1992
2-Methylfuran 0.2 mg/m3 Smet, Van Langenhove, and De Bo 1999
2-Methylfuran 152 ng/m3 Muller et al. 2004
2-Methylfuran 236 ng/m3 Muller et al. 2004
2-Methylfuran 1 135 ng/m3 Muller et al. 2004
3-Methylhexane 0.27 μg/m3 Liu et al. 2009 (Day 15)
2-Methylhexene 0.33 μg/m3 Liu et al. 2009 (Day 12)
4-Methyl-2-pentanone 16 000 μg/m3 Eitzer 1995
Methyl propionate 5.9 mg/m3 Smet, Van Langenhove, and De Bo 1999
Methyl propyl disulfide 0.1 mg/m3 Smet, Van Langenhove, and De Bo 1999
Myrcene 2 250 ng/m3 Muller et al. 2004
(table continues)
Naphthalene 0.13 μg/m3 Liu et al. 2009 (Day 15)
Naphthalene 1 400 μg/m3 Eitzer 1995
Nonane 19 μg/m3 Van Durme, McNamara, McGinley 1992
Nonane 19.62 μg/m3 Liu et al. 2009 (Day 15)

40
Octane 13.56 μg/m3 Liu et al. 2009 (Day 12)
Octane 15 μg/m3 Van Durme, McNamara, McGinley 1992
3-Octanone 997 ng/m3 Muller et al. 2004
3-Octanone 1 485 ng/m3 Muller et al. 2004
3-Octanone 2 035 ng/m3 Muller et al. 2004
1-Octen-3-ol 421 ng/m3 Muller et al. 2004
Pentane 884 μg/m3 Van Durme, McNamara, McGinley 1992
Pentane 75 μg/m3 Mao et al. 2006
trans-2-Pentene 13.22 μg/m3 Liu et al. 2009 (Day 6)
2-Pentylfuran 84 ng/m3 Muller et al. 2004
2-Pentylfuran 110 ng/m3 Muller et al. 2004
2-Pentylfuran 1 241 ng/m3 Muller et al. 2004
Phenol 13 μg/m3 Van Durme, McNamara, McGinley 1992
alpha-Pinene 6.9 mg/m3 Smet, Van Langenhove, and De Bo 1999
(table continues)
alpha-Pinene 6 839 ng/m3 Muller et al. 2004
alpha-Pinene 4.34 μg/m3 Liu et al. 2009 (Day 12)

41
alpha-Pinene 14 μg/m3 Mao et al. 2006
alpha-Pinene 78 μg/m3
(6/27/90)
alpha-Pinene 251 μg/m3 Van Durme, McNamara, McGinley 1992 (10/89)
alpha-Pinene 333 μg/m3
(6/26/90)
alpha-Pinene 2 100 μg/m3 Eitzer 1995
beta-Pinene 2.24 μg/m3 Liu et al. 2009 (Day 15)
beta-Pinene 41 μg/m3 Mao et al. 2006
beta-Pinene 43 μg/m3 Mao et al. 2006
2-Propanol 95 mg/m3 Smet, Van Langenhove, and De Bo 1999
n-Propanol 64 μg/m3 Van Durme, McNamara, McGinley 1992
n-Propylbenzene 1 200 μg/m3 Eitzer 1995
i-Propylbenzene 5.58 μg/m3 Liu et al. 2009 (Day 15)
Propylbenzene 4.49 μg/m3 Liu et al. 2009 (Day 15)
Propyl propionate 2.7 mg/m3 Smet, Van Langenhove, and De Bo 1999
Pyridine 47 μg/m3 Van Durme, McNamara, McGinley 1992
(table continues)

42
Styrene 26 μg/m3 Van Durme, McNamara, McGinley 1992
Styrene 291 μg/m3 Mao et al. 2006
Styrene 482 μg/m3 Mao et al. 2006
Styrene 6 100 μg/m3 Eitzer 1995
alpha-Terpinene 127 ng/m3 Muller et al. 2004
alpha-Terpinene 1 752 ng/m3 Muller et al. 2004
alpha-Terpinene 1 843 ng/m3 Muller et al. 2004
gamma-Terpinene 768 ng/m3 Muller et al. 2004
gamma-Terpinene 3 991 ng/m3 Muller et al. 2004
gamma-Terpinene 12 812 ng/m3 Muller et al. 2004
alpha-Terpineol 149 ng/m3 Muller et al. 2004
alpha-Terpineol 564 ng/m3 Muller et al. 2004
alpha-Terpineol 1 849 ng/m3 Muller et al. 2004
Terpineol 81 μg/m3 Eitzer 1995
Terpinolene 109 ng/m3 Muller et al. 2004
Terpinolene 654 ng/m3 Muller et al. 2004
Terpinolene 1 703 ng/m3 Muller et al. 2004
Tetrachloroethene 5 600 μg/m3 Eitzer 1995
Thujone 4.9 mg/m3 Smet, Van Langenhove, and De Bo 1999
Toluene 20 μg/m3 Mao et al. 2006
Toluene 64 μg/m3 Mao et al. 2006
Toluene 73.84 μg/m3 Liu et al. 2009 (Day 15)
Toluene 488 μg/m3 Van Durme, McNamara, McGinley 1992
Toluene 66 000 μg/m3 Eitzer 1995
1,2,3-Trichlorobenzene 6 μg/m3 Eitzer 1995
1,2,4-Trichlorobenzene 9 μg/m3 Eitzer 1995
1,1,2,-Trichloroethane 27 μg/m3 Van Durme, McNamara, McGinley 1992
l,l,l-Trichloroethane 15 000 μg/m3 Eitzer 1995

43
Trichloroethene 1 300 μg/m3 Eitzer 1995
Trichlorofluoromethane 915 000 μg/m3 Eitzer 1995
1,2,4-Trimethylbenzene 23.57 μg/m3 Liu et al. 2009 (Day 15)
(table continues)
1,2,4-Trimethylbenzene 1 000 μg/m3 Eitzer 1995
1,3,5-Trimethylbenzene 2 200 μg/m3 Eitzer 1995
2,2,4-Trimethylpentane 0.43 μg/m3 Liu et al. 2009 (Day 15)
m,o-Xylene 15 000 μg/m3 Eitzer 1995
m,p-Xylene 1 654.49 μg/m3 Liu et al. 2009 (Day 15)
o-Xylene 4 μg/m3 Mao et al. 2006
o-Xylene 35 μg/m3 Mao et al. 2006
o-Xylene 318.76 μg/m3 Liu et al. 2009 (Day 15)

44
o-Xylene 1 861.34 μg/m3 Liu et al. 2009 (Day 9)
p-Xylene 8 μg/m3 Mao et al. 2006
p-Xylene 46 μg/m3 Mao et al. 2006
p-Xylene 6 900 μg/m3 Eitzer 1995
Xylene 29 μg/m3 Van Durme, McNamara, McGinley 1992
Notes: Concentrations reported as “nd” or less than thedetection level were excluded from Table 3.
The format of Table 3 was inspired by the work of Font, Artola, and Sánchez (2011), who studied the detection,
composition, and treatment of VOCs from waste treatment plants.
compounds were not included on the target list (many of these compounds could not be
determined with the chosen methodology).” Several toxic compounds (per the OEHHA)
were present, including benzene, xylene, ethylbenzene, 2-butanone, and naphthalene.
Aromatics (e.g., benzene, xylene, and phenol), ketones (e.g., acetone and butanone), esters
(e.g., ethyl acetate), hydrocarbons (e.g., pentene and hexane), alcohols (e.g., propanol,
methanol, and ethanol), volatile fatty acids (e.g., acetic acid), and aldehydes (e.g.,
acetaldehyde) were all detected.
Eitzer (1995) compared eight different composting facilities. His study targeted 67
volatile compounds that might impact human health. Terpenes were also included, since the
study author identified large peaks on the total ion chromatograms. The author indicates that
it is likely that additional VOCs are present, but that these were not included, since they were
not targeted compounds. Eitzer (1995) found that most of the emissions are found at the
tipping floors, in shredders, and in areas where the compost first reaches the designed
operating temperatures. The maximum observed concentrations of the VOCs with threshold
limit values (TLVs), as listed by ACGIH, are reported in Table 3. Eitzer (1995) reported five
terpenes by name: alpha-pinene, camphene, 3-carene, d-limonene, and terpineol. The highest
reported concentrations of these five terpenes (based on average concentrations taken at
different characteristic locations) are also included in Table 3. Additional terpenes were
detected, but were not reported by name. The maximum total concentration of terpenes
reported was 16,600 μg m-3.

45
Liu et al. (2009) measured the VOCs emitted from municipal solid waste and
calculated the VOC removal efficiency after a biofilter. The composting process used at the
plant studied began after the waste was piled in stacks, which were aerated for 20 days. After
the stacks of waste were aerated, the waste was subjected to a mechanical separation process
where "plastic, glass, metal, bricks, and other noncarbanaceous wastes" were removed.
Following mechanical separation, the remaining fraction was subjected to an aerobic
composting process for 40 days. The volatile emissions from the biostabilization process
were collected. The concentrations of the compounds detected in the influent of the biofilter
are reported in Table 3.
Mao et al. (2006) measured emissions from three food waste composting plants in
Taiwan. The three plants were termed Plant A, Plant B, and Plant C. Plants A and C used
household food waste and vegetable, fruit, and garden waste (VFG) as feedstock, while Plant
B used poultry manure and food waste as feedstock. The wastes in these plants were
composted in windrows within enclosed buildings. The composting process lasted
approximately 20–30 days. The concentrations of VOCs reported to be in the ambient air at
facilities A and B are reported in Table 3. The concentration of amines was not reported in
Table 3, as the amines were not reported by name. The concentration of amines was reported
to range from 2,408 to 72,245 μg m-3.
The emissions of three composting facilities were studied. Facilities A, B, and C used
feedstocks of garden and plant refuse as well as municipal biowaste. Samples were collected
from storage areas near the compost piles, next to the site where compost is sieved, during
the turning of the compost in the storage area, and at the outlet of the biofilter, except at
facility A (Muller et al. 2004). The concentrations of the targeted VOCs detected at the
compost piles are shown in Table 3.
In this study, aerobic composting was conducted on a pilot scale. The emissions from
the aerobic composting portion of the study were determined to be predominantly alcohols. It
is reported that chemical oxidation and aerobic biodegradation of terpenes may account for
the difference detected between the aerobic processes and the anaerobic processes used. The
feedstock material was source-separated waste having an average composition of 70 percent
garden waste, 20 percent kitchen waste, and 10 percent nonrecyclable paper. The aerobic
portion of the study lasted 12 weeks. The "total weight loss due to VOC-emissions

46
corresponded to 0.059 percent of the original biowaste" (Smet et al. 1999). Alcohols,
carbonyl compounds, esters, and ethers were emitted primarily in the initial phase of the
process. Volatile organic sulfur compounds were emitted primarily during the thermophilic
stage. All terpenes, with the exception of p-cymene, followed a "zero-order decrease in
emission rate versus time" (Smet et al. 1999). In the aerobic process, alcohols and carbonyl
compounds composed 75 percent of the total VOC emissions and were emitted primarily
during the first week. Smet et al. (1999) found that the production of VOCs may occur in
"anaerobic microsites of the biowaste piles." The maximum observed concentrations of
VOCs are reported in Table 3.
VOC emissions were measured from an aerated static pile composting process where
dewatered, anaerobically digested sludge was mixed with wood chips before composting.
Samples were taken from the active compost blower exhaust. The authors of the study
indicated that the sulfur compounds came from the sludge, while terpenes originated from the
wood chips that were used as an amendment. The VOCs emitted in the active compost
blower exhaust that were determined by Van Durme et al. (1992) to have TLVs listed by the
ACGIH are shown in Table 3. Over 72 compounds were identified at this compost facility;
however, of the 72, only 29 had associated TLVs. Van Durme et al. (1992) also reported
values for compounds thought to contribute significantly to odor. Dimethyl disulfide,
dimethyl sulfide, limonene, and alpha-pinene were considered to contribute to odor, since
their concentrations exceeded their respective threshold odor concentrations, as published in
the literature (Van Durme et al. 1992). The concentrations of these compounds as reported by
Van Durme et al. (1992) are also reported in Table 3.

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