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

3

Copyright © 2013

by

Stephanie Harris

All Rights Reserved

4

ABSTRACT OF THE PROJECT

Volatile Organic Compound Emissions from Compostingby

Stephanie HarrisMaster 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.............................................................................................................5

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

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Pathogens...............................................................................................................13

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...........19

South Coast Air Quality Management District..........................................19

San Joaquin Valley Air Pollution Control District....................................20

Antelope Valley Air Pollution Control District.........................................22

Particulate Matter and Nuisance Rules............................................................23

Composting Volatile Organic Compound Emissions Sources........................23

Biogenic Volatile Organic Compounds.....................................................24

Vegetation as a Source of Volatile Organic Compounds..........................24

Microbial Volatile Organic Compounds...................................................25

Xenobiotic Sources of Volatile Organic Compounds...............................25

Magnitude of Volatile Organic Compound Emissions from Composting Facilities.....................................................................................................26

Factors Affecting Volatile Organic Compound Emissions.............................28

Feedstock and Volatile Organic Compound Emissions............................28

Phases of the Composting Process and the Emissions of Volatile Organic Compounds................................................................................................30

Control Parameters and Volatile Organic Compound Emissions.............31

Review of Selected Studies.......................................................................31

CONCLUSIONS.....................................................................................................................50

REFERENCES........................................................................................................................51

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LIST OF TABLES

PAGE

Table 1. Summary of the Magnitude of VOC Emissions from Selected Studies....................

Table 2. South Coast and San Joaquin District VOC Emission Factors.................................

Table 3. Compounds Identified in Selected Studies................................................................

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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 mar-

ketable end product. While composting is a viable method of waste reduction, there are dis-

advantages associated with the process, including the emission of volatile organic com-

pounds (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 ad-

vantages 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 het-

erogeneous 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 afford-

able, while costs for larger systems may become prohibitive, depending on the operation. Op-

erational 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 com-

post. 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 sys-

tems may be smaller than the footprints associated with windrow and ASP processes


3

CHAPTER 2

COMPOSTING PARAMETERS

Each variation of the aerobic composting process shares the same control and moni-

toring 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), mois-

ture 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 ad-

just 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 avail-

able 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 typi-

cally 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


MOISTURE CONTENT

Moisture content is another important control parameter. The moisture content is ex-

pressed 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 in-

activated. In this case the moisture content could be increased in order to reduce the tempera-

ture. 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 per-

centage depends on the structure of the material to be composted (Haug 1980). Moisture con-

tent 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 care-

fully 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 com-

post. 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 re-

duce the temperature by 5–10 degrees Celsius (9–18 degrees Fahrenheit) (Haug 1980). An-

other 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 amend-

ment, alcohol formation is of great importance, as the compost is intended to provide nutri-

tion 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 de-

5

graded. It has been reported that a particle size of less than two inches is ideal for the com-

posting 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 through-

out 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 impor-

tant 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 de-

grees 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 cur-

ing 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 Asper-

gillus 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 ther-

mophilic 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)

7

(Lowenfels and Lewis 2006). As the nutrients are exhausted, the temperature drops and the

composting process progresses to the final phase.

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 con-

tinue 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. Typi-

cal wastes used for composting are yard and green waste, food waste, paper waste, the or-

ganic 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 car-

casses. Feedstock may be sourced from restaurants, private residences, and agricultural

sources, among other sources (Landreth and Rebers 1997). Some feedstocks are higher in ni-

trogen, while others are higher in carbon content. Different feedstocks are more likely to re-

lease sulfurous or xenobiotic compounds. The feedstock characteristics must be considered in

designing a composting process. When composting material is properly aerated, carbon, ni-

trogen, and sulfur present in the feedstock are converted to carbon dioxide, nitrate, and sul-

fate, 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 ex-

pected 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 inor-

ganic 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

9

and denitrification processes. According to Kissel, Henry, and Harrison (1992), the release of

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 ni-

trate (if oxygenation is sufficient). Second, if the C:N ratio is high, the conversion of inor-

ganic nitrogen to organic nitrogen is more prevalent than the release of ammonia, as the mi-

crobial 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 pro-

teins (Kissel, Henry, and Harrison 1992). In the presence of a sufficient level of oxygen, min-

eralized organic sulfur can be oxidized to sulfate. The oxidation of sulfur compounds is de-

sirable, 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 in-

creases, 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 pre-

vention 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 pro-

jected diminishing landfill space, Assembly Bill (AB) 939 was drafted. AB 939 or the Inte-

grated 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. En-

vironmental 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

11

with regard to organics: Arkansas, Connecticut, Delaware, Florida, Georgia, Illinois, Indiana,

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 De-

partment, 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 Green-

house Gas Emissions through Recycling and Composting, in which composting was deter-

mined 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 emis-

sions 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 Cli-

mate and Materials Management Forum 2011). The California Air Resources Board (CARB)

has developed a methodology for calculating a compost emission reduction factor (CERF).

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Using this methodology, CARB estimates a CERF of 0.42 metric tons of CO2 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 “in-

creased soil carbon storage, reduced soil erosion, reduced water use, and a decrease in fertil-

izer 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, bacte-

rial 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 OF THE APPLICATION OF COMPOST AS A SOIL AMENDMENT

Composting is beneficial not only for waste reduction and for GHG emissions reduc-

tion but also for the prevention of runoff and for the reduction of the use of fertilizers. Com-

post increases soil density and water holding capacity (Haug 1980). Fertilizer runoff is

known to contribute to eutrophication of water bodies. Compost provides nutrients and bene-

ficial 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 manage-

ment 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 facili-

ties. 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 bac-

teria, 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. As-

caris, 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 infec-

tion, 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 abra-

sions. 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 associ-

ated 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, particu-

late 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 com-

pound" 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, con-

tribute to the formation of ground-level ozone, and contribute to odor nuisances.

Volatile Organic Compounds and Human HealthThere 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 com-

posting 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 in order to reduce the

associated risk. The Clean Air Act requires that the EPA regulate the emissions of hazardous

15

air pollutants (HAP). AB 2728 required that CARB identify the Federal HAP as TAC. Addi-

tionally, 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 mea-

sures be in place if a significant risk is identified (California Air Resources Board 2010) . Lo-

cal 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 be-

tween 300 and 900 meters from Ecoparc-2, an organic waste treatment facility, never ex-

ceeded 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 unac-

ceptable regulatory threshold for air toxics. The 1989 Benzene National Standard for Haz-

ardous 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 individ-

uals was set and a lower limit of an individual lifetime risk level no higher than approxi-

mately one in 1,000,000 for the greatest number of persons possible was set (U.S. Environ-

mental 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 accept-

able (Fowle and Dearfield 2000). If the HI is above one, the site may be considered for reme-

dial 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 in-

cremental cancer risk of less than one in one million is considered acceptable for new facili-

ties 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 Diego: Air Pol-

lution Control District 1996). Both the noncancer and cancer risks in this study were driven

16

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 guide-

lines by several orders of magnitude, in most cases.

The Occupational Safety and Health Administration (OSHA) and the Division of Oc-

cupational 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 concen-

trations 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 compost-

ing operation were acceptable, continued monitoring of Ecoparc-2 was recommended, and it

is advisable that other sites also conduct monitoring in California as more stringent standards

are put in place, especially for new facilities. Special care should be taken to ensure the pro-

tection of staff at composting facilities. Continued monitoring will allow the variations over

17

time to be observed, and long-term patterns can be elucidated. In addition, continued moni-

toring 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 NuisanceImportant 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 nui-

sance. 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 in-

cluded the following organic compounds: amines, dimethyl sulfide, acetic acid, ethylben-

zene, 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, trans-

port, 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 accep-

tor, 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. According to Muller et al. (2004), "alpha-

Pinene, Limonene, (+)-3-Carene, and Camphene, in combination with 2-Heptanone, all oc-

curring 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

18

that within the previous two years over 3,000 nuisance complaints associated with compost-

ing 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 emis-

sions 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 pro-

tect 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

(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 environ-

mental impact report and cost–benefit analysis and subsequently revise the rule (Cejnar

19

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 in-

tended 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 reg-

ister with the SCAQMD (South Coast Air Quality Management District 2003a). SCAQMD

Rule 1133.1 prohibits chipping and grinding facilities from accepting food waste "unless oth-

erwise 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 de-

signed 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 compost-

ing 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.

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-spray-

ing 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

20

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 VALLEY AIR 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 facil-

ity, 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 fa-

cility must scrape or sweep areas such that material no greater than one inch is visible, main-

tain 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 alterna-

tive 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 One mitigation mea-

sures or three Class One mitigation measures and one Class Two mitigation measure for ac-

tive 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 mitiga-

21

tion 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 man-

ner, 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 Water-

ing 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 per-

cent, 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 de-

scribed 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 VALLEY AIR 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 differ-

ent 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 in-

volves both the active and curing phase” (Antelope Valley AQMD 2009). The third require-

ment 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

22

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 RulesWhile 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 nui-

sance 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 annoy-ance 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 prop-erty. 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 specif-

ically 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, alde-

hydes, hydrocarbons, volatile fatty acids, esters, terpenes, and alcohols. Pierucci et al. (2005)

studied the emissions from undifferentiated MSW and found that the most important emis-

sions were of terpenes, monocyclic arenes, alkanes, halogenated compounds, and esters. De-

foer et al. (2002) studied the emissions from four vegetable fruit and garden (VFG) compost-

ing operations as well as the emissions from a rendering plant. The most significant emis-

sions that occurred were terpenes (65 percent of the total VOC emissions). Ketones, hydro-

carbons, 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

23

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 sev-

eral 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 de-

cay 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 oc-

curred 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. Al-

pha-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).

VEGETATION AS A 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 me-

24

chanical wounding of plants releases biogenic volatile organic compounds. Volatiles com-

monly 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 thir-

teen fungal species that have been isolated from composting plants. Many VOCs were identi-

fied 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 ac-

tivity in combination with a complex substratum (e.g. wood)."

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 contami-

nated with VOCs. Household products containing VOCs include "cosmetics, cleaning prod-

ucts, polishes, waxes, paints, pesticides, and auto maintenance products" (Brown, Thomas,

and Whitney 1997). Release of VOCs from household products could occur due to the crush-

ing or breakage of a household product container at some point in municipal solid waste pro-

cessing (Brown, Thomas, and Whitney 1997). Acetone, alcohols, benzene, carbon tetrachlo-

ride, cresol, formaldehyde, naphthalene, phenols, toluene trichloroethylene, xylene, etc. may

25

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 mu-

nicipal 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-contain-

ing 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 Re-

sources 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 and

mobile sources are excluded, and only stationary sources are considered, the total ROG emis-

sions 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 han-

dled 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 reac-

tivity in the range of 0.5–1 g-O3 g-VOC-1 (Kumar et al. 2011).

26

Font, Artola, and Sánchez (2011) reviewed the work of several authors that have re-

ported the magnitude of VOC emissions from composting operations. In this work the find-

ings 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 anaer-

obic 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 com-

bined anaerobic process, 5.70 for turned windrows, and 0.56 for home composting. All pro-

cesses 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 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 Selected Studies

Waste TypeVOC Emis-

sions 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

27

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 Emis-sions

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 con-

trol parameters can be altered in order to reduce emissions of VOCs. With continued re-

search if may be possible to develop improved best management practices for composting fa-

cilities based on the control of these parameters.

FEEDSTOCK AND VOLATILE 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 primar-

ily 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 TypeVOC Emis-sion 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

28

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 Opera-tions 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 pa-

per 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 pes-

ticides, from atmospheric deposition, or as a product of a reaction from cooking. Another ex-

ample can be found in the work of Pagans, Font, and Sánchez (2007). Their study deter-

mined 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

29

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 OF THE COMPOSTING PROCESS AND 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 Pa-

gans, Font, and Sánchez (2006) among others. Here the findings associated with the emis-

sions 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 ac-

tive 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 maxi-

mum 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 na-

ture 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 alco-

hol, 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 tipping piles were similar to those of

the older compost windrows, with a flux of 70 percent alcohol.

CONTROL PARAMETERS AND 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 find-

ings of Delgado-Rodriguez et al. (2011; 2012) and Büyüksönmez (2012) are presented.

30

Delgado-Rodriguez et al. (2012) studied the effect of varied aeration rates on the evo-

lution 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-Ro-

driguez et al. (2011) concluded that a high C:N ratio may be a "suitable selection" to mini-

mize 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 emis-

sions. 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)."

REVIEW OF SELECTED STUDIES

Font, Artola, and Sánchez (2011) reviewed several studies and presented the sum-

mary 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 presented in Ta-

ble 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 com-

pounds 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 alde-

hydes, organic acids, organic sulfur compounds, etc.), but these

31

Table 3. Compounds Identified in Selected Studies

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

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

32

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)




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


33


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)

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)

34















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)





Dimethyl disulfide 860 μg/m3Van Durme, McNamara, McGinley 1992 (6/27/90)

Dimethyl disulfide 956 μg/m3 Van Durme, McNamara, McGinley 1992 (10/89)

Dimethyl disulfide 1 311 μg/m3Van Durme, McNamara, McGinley 1992 (6/26/90)

2,3-Dimethylpentane 1.14 μg/m3 Liu et al. 2009 (Day 15)


35




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/m3Van Durme, McNamara, McGinley 1992 (6/27/90)

Dimethyl sulfide 2 667 μg/m3Van Durme, McNamara, McGinley 1992 (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)



(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

36

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)




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)

37


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

Isopropyl benzene 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/m3Van Durme, McNamara, McGinley 1992 (6/27/90)

Limonene 2 667 μg/m3Van Durme, McNamara, McGinley 1992 (6/26/90)

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

38

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)

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)


39




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)





Octane 13.56 μg/m3 Liu et al. 2009 (Day 12)

Octane 15 μg/m3 Van Durme, McNamara, McGinley 1992




40

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)


alpha-Pinene 14 μg/m3 Mao et al. 2006




alpha-Pinene 78 μg/m3Van Durme, McNamara, McGinley 1992 (6/27/90)

alpha-Pinene 251 μg/m3 Van Durme, McNamara, McGinley 1992 (10/89)

alpha-Pinene 333 μg/m3Van Durme, McNamara, McGinley 1992 (6/26/90)

41

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)


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

42

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

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)



43



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)




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 the detection level were excluded from Table 3.

44

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 de-

termined 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 tip-

ping 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 val-

ues (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.

Liu et al. (2009) measured the VOCs emitted from municipal solid waste and calcu-

lated 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. Fol-

lowing mechanical separation, the remaining fraction was subjected to an aerobic composting

process for 40 days. The volatile emissions from the biostabilization process were collected.

45

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 com-

posted 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 facil-

ity 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 corre-

sponded 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 mi-

46

crosites 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 indi-

cated 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 val-

ues for compounds thought to contribute significantly to odor. Dimethyl disulfide, dimethyl

sulfide, limonene, and alpha-pinene were considered to contribute to odor, since their con-

centrations exceeded their respective threshold odor concentrations, as published in the litera-

ture (Van Durme et al. 1992). The concentrations of these compounds as reported by Van

Durme et al. (1992) are also reported in Table 3.

47

CHAPTER 7

CONCLUSIONS

The composting process has both advantages and disadvantages. With the growing in-

terest in GHG emissions and continued interest in landfill diversion rates, composting is ex-

pected to increase in the near future. As composting increases, it is important that we under-

stand and mitigate the emissions of VOCs for several reasons. Mitigation of VOCs will allow

the reduction of the potential odor nuisance associated with composting. This will be impor-

tant if the public is expected to welcome new commercial facilities. Mitigation of VOCs will

indirectly limit the emissions of TACs, which may reduce cancer and noncancer risks to

more acceptable levels. It is necessary that continued monitoring of facilities be conducted,

especially if the facility is in close proximity to an offsite receptor. Compost plant workers

should be provided the proper personal protective equipment, as they will be exposed to

higher concentrations of VOCs than offsite receptors. Mitigation of VOCs is necessary for air

basins that are not in attainment of the NAAQS of CAAQS. Controlling the emissions from

composting may help these air basins to achieve attainment. Mitigation of VOC emissions

should be the focus of all entities involved in encouraging or mandating composting as a

solid waste management measure. Understanding how and why VOCs are emitted through-

out the composting process will allow better control and mitigation of VOC emissions. While

many of the emissions would occur naturally if the materials were not composted, the con-

centration of these materials into a single location and the opportunity to treat the VOC emis-

sions, as well as their increased potential as a nuisance and health hazard, require that com-

mercial composting facilities take appropriate measures to reduce and control the emissions

of VOCs. Further research may help to elucidate more cost-effective and feasible measures

that can be used on a wide scale to help commercial facilities manage their emissions.

48

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