TECHNICAL SUPPORT DOCUMENT FOR 

INDUSTRIAL WASTEWATER TREATMENT: 

FINAL RULE FOR MANDATORY REPORTING 

OF GREENHOUSE GASES 

Climate Change Division 

Office of Atmospheric Programs 

U.S. Environmental Protection Agency 

June 2010 
i 

CONTENTS 

Page 

1. INTRODUCTION AND BACKGROUND ..................................................................................1-1 

2. INDUSTRY DESCRIPTION ...................................................................................................2-1 

2.1 Industrial Wastewater Treatment.........................................................................2-1 

2.2 Reporting Rule Applicability...............................................................................2-3 

2.2.1 Processes Included in the Reporting Rule ...............................................2-3 

2.2.2 Industries Included in the Reporting Rule ...............................................2-4 

3. EMISSION ESTIMATES .......................................................................................................3-1 

3.1 Pulp and Paper Mills............................................................................................3-1 

3.2 Food Processing Facilities ...................................................................................3-2 

3.3 Ethanol Production Facilities...............................................................................3-5 

3.4 Petroleum Refineries............................................................................................3-6 

3.5 Summary..............................................................................................................3-7 

4. ESTIMATING METHANE GENERATION FROM WASTEWATER TREATMENT.........................4-1 

4.1 Flow Measurement...............................................................................................4-3 

4.2 Organic Matter Concentration Measurement and Analysis.................................4-4 

5. ESTIMATES OF METHANE RECOVERY ...............................................................................5-1 

5.1 Biogas Flow Measurement ..................................................................................5-3 

5.2 Biogas Composition Monitoring..........................................................................5-3 

6. METHANE EMISSIONS CALCULATION ...............................................................................6-1 

7. COSTS FOR GHG REPORTING............................................................................................7-1 

8. REFERENCES .....................................................................................................................8-1 
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LIST OF TABLES 

Page 

3-1 Values Used to Estimate Pulp and Paper CH4 Emissions................................................ 3-2 

3-2 Values Used to Estimate Meat and Poultry Processing CH4 Emissions.......................... 3-4 

3-3 Values Used to Estimate Ethanol Production CH4 Emissions......................................... 3-5 

3-4 Values Used to Estimate Petroleum Refinery CH4 Emissions ........................................ 3-6 

3-5 Estimated Number of Plants Required to Report and Estimated Emissions ................... 3-7 

4-1 Emission Factors.............................................................................................................. 4-3 

6-1 Collection Efficiencies of Anaerobic Processes .............................................................. 6-2 

7-1 Industrial Wastewater Treatment Monitoring Costs........................................................ 7-2 
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LIST OF FIGURES 

Page 

2-1 Diagram of Wastewater Treatment Inputs and Outputs .................................................. 2-2 

4-1 Methane Generation......................................................................................................... 4-1 

5-1 Diagram of Biogas Recovery from Anaerobic Wastewater Treatment ........................... 5-1 

5-2 Diagram of Biogas Recovery from Anaerobic Sludge Digestion.................................... 5-2 

6-1 Diagram of Leakage From Anaerobic Sludge Digestion Biogas Recovery .................... 6-1 
1-1 

1. INTRODUCTION AND BACKGROUND

This document supports the Mandatory Reporting of Greenhouse Gases Final Rule 

(Reporting Rule) for the industrial wastewater treatment source category. The rule is divided into 

industry-specific categories and other categories that span industries. Categories that span 

industries include stationary fuel combustion sources, industrial landfills, and industrial 

wastewater treatment. EPA proposed reporting requirements for the wastewater treatment source 

category in the Federal Register on April 10, 2009, under Subpart II. EPA received comments on 

this subpart and revised the proposed regulation. The major changes from the proposed rule 

include: 

 Renaming the source category Industrial Wastewater Treatment; 

 Clarifying the subpart’s applicability; 

 Removing reporting requirements for petroleum refining oil/water separators and 

petrochemical facilities; and 

 Revising monitoring requirements. 

This document provides technical support for the final rule. 
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2. INDUSTRY DESCRIPTION

The industrial wastewater treatment source category of the Reporting Rule specifically 

applies to anaerobic processes used to treat industrial wastewater and industrial wastewater 

treatment sludge at facilities that perform pulp and paper manufacturing, food processing, 

ethanol production, and petroleum refining. This section describes industrial wastewater 

treatment, including the anaerobic treatment operations covered under the Reporting Rule, and 

explains how the Reporting Rule applies to this source category. 

2.1 Industrial Wastewater Treatment

Wastewater treatment refers to processes that treat or remove pollutants and 

contaminants, such as soluble organic matter, suspended solids, pathogenic organisms, and 

chemical contaminants, from wastewater prior to its reuse or discharge from the facility. These 

pollutants and contaminants are removed from wastewater using physical and chemical 

processes (such as sedimentation and chlorine disinfection) and biological processes. Biological 

wastewater treatment processes can produce CO2 and anthropogenic CH4 and N2O emissions. 

Industrial wastewater may be treated either on site at an industrial facility (industrial 

wastewater treatment) or in combination with municipal wastewater at a centralized publicly 

owned treatment plant (POTW) or privately owned treatment plant. Industrial wastewater is 

defined as water that comes into direct contact with or results from the storage, production, or 

use of any raw material, intermediate product, finished product, by-product, or waste product. 

Examples of industrial wastewater include, but are not limited to, paper mill white water, 

wastewater from equipment cleaning, wastewater from air pollution control devices, rinse water, 

contaminated stormwater, and contaminated cooling water. Municipal wastewater treatment 

refers to a series of treatment processes used to remove contaminants and pollutants from 

domestic, business, and industrial wastewater collected in city sewers and transported to a 

centralized wastewater treatment system such as a POTW. 

Soluble organic matter is generally removed from wastewater using biological processes 

in which microorganisms consume the organic matter for maintenance and growth. The resulting 

biomass and other suspended solids, together known as sludge, are removed from the treated 

wastewater before it is discharged to a receiving stream. Microorganisms can biodegrade soluble 

organic material in wastewater under aerobic or anaerobic conditions. Anaerobic wastewater 

treatment refers to the procedure in which organic matter in wastewater or other material is 

degraded by microorganisms in the absence of oxygen, resulting in the generation of CO2 and 

CH4. 

Figure 2-1 shows a simplified diagram outlining the inputs and outputs from wastewater 

treatment operations. Typically, treatment of wastewater begins with primary treatment using 

processes such as screening or settling. Subsequently, wastewater may be biologically treated 

either under aerobic or anaerobic conditions. Most biological treatment processes are designed to 

separate solids from wastewater; often, these solids are treated further in sludge digesters, which 

may be either aerobic or anaerobic. 
Figure 2-1. Diagram of Wastewater Treatment Inputs and Outputs 

As shown in Figure 2-1, both biological wastewater treatment and sludge digestion 

generate greenhouse gases (GHGs). Aerobic processes emit CO2; however, these are not 

considered anthropogenic emissions and therefore are neither included in Inventory of U.S. 

Greenhouse Gas Emissions and Sinks (EPA, 2007) (hereafter referred to as the Inventory) nor in 

the Reporting Rule. Because CO2 released from wastewater treatment is biogenic in origin (i.e., 

produced by biological processes), the Intergovernmental Panel on Climate Change (IPCC) 

considers these CO2 emissions to be part of the natural carbon cycle. 

Domestic and some industrial wastewaters contain nitrogen, usually in the form of urea, 

ammonia, and proteins. These compounds are converted to nitrate (NO3) through the aerobic 

process of nitrification. Denitrification occurs under anoxic conditions (without free oxygen), 

and involves the biological conversion of nitrate into di-nitrogen gas (N2). N2O can be an 

intermediate product of both processes, but is more often associated with denitrification. 

Industrial wastewater is generally low in nitrogen and, as a result, its treatment generates little 

N2O. Emissions of N2O from industrial wastewater treatment are not included in either the 

Inventory or the Reporting Rule. The IPCC has stated that the N2O emissions from industrial 

sources are insignificant compared to emissions from domestic wastewater. 

The only GHG accounted for in Subpart II of the Reporting Rule is CH4. The principal 

factor in determining the CH4 generation potential of wastewater is the amount of degradable 

organic material in the wastewater. Common parameters used to measure the organic component 

of the wastewater are Biochemical Oxygen Demand (BOD5) and Chemical Oxygen Demand 

(COD). BOD5 represents the amount of oxygen used by microorganisms to consume the organic 

matter contained in the wastewater through aerobic decomposition processes in a 5-day period. 

COD measures the total material available for chemical oxidation (both biodegradable and nonbiodegradable). 

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2.2 Reporting Rule Applicability

The requirements of Subpart II apply to anaerobic processes used to treat industrial 

wastewater and wastewater treatment sludges at pulp and paper mills, food processing facilities, 

ethanol production facilities, and petroleum refineries. These are the only industries covered by 

Subpart II. Further, Subpart II does not include emissions from: 

 Municipal wastewater treatment plants; 

 Separate treatment of sanitary wastewater at industrial facilities; 

 Oil/water separators; or 

 Aerobic and anoxic treatment of industrial wastewater. 

2.2.1 Processes Included in the Reporting Rule 

The anaerobic treatment processes covered by Subpart II are those processes in which 

organic matter in wastewater or wastewater treatment sludge is degraded by microorganisms in 

the absence of oxygen, resulting in biogas generation. “Biogas” refers to the combination of 

CO2, CH4, and other gases produced by the biological breakdown of organic matter in the 

absence of oxygen (Metcalf & Eddy, 1979). 

Requirements for this source category require facilities to report CH4 emissions only 

from anaerobic processes and related biogas destruction devices. Anaerobic processes are 

biological processes that occur in the absence of oxygen (Metcalf & Eddy, 1979). Facilities are 

required to report CH4 emissions from anaerobic reactors and anaerobic lagoons used to treat 

industrial wastewater and from anaerobic sludge digesters used to treat industrial wastewater 

treatment sludges. The sludges may be produced by either aerobic or anaerobic wastewater 

treatment processes. Facilities are also required to report methane emissions from devices used to 

destroy the biogas recovered from the anaerobic processes. 

Anaerobic reactors. Anaerobic reactors are enclosed vessels used for anaerobic 

wastewater treatment processes (Grady, Daigger, and Lim, 1999; Metcalf & Eddy, 1979). The 

IPCC methodology for estimating CH4 emissions from industrial wastewater treatment identifies 

two types of anaerobic reactors, anaerobic sludge blanket and fixed film (IPCC, 2006; 

Table 6-8). 

Anaerobic lagoons. Anaerobic lagoons are lined or unlined earthen basins used for 

wastewater treatment, in which oxygen is absent throughout the depth of the basin, except for a 

shallow surface zone (Metcalf & Eddy, 1979). Anaerobic lagoons are not equipped with surface 

aerators. The IPCC methodology for estimating CH4 emissions from industrial wastewater 

treatment classifies anaerobic lagoons into two depths: deep (depth more than 2 meters) or 

shallow (depth less than 2 meters) (IPCC, 2006; Table 6-8). 

Anaerobic sludge digesters. Anaerobic sludge digesters are enclosed vessels in which 

wastewater treatment sludges are degraded by microorganisms in the absence of oxygen, 

resulting in the generation of CO2 and CH4 (Metcalf & Eddy, 1979). The digested wastewater 

treatment sludges may have been generated by aerobic treatment processes (e.g., the activated 

sludge process). If the sludge digester is operated in the absence of oxygen, it is considered an 

anaerobic process. Anaerobic sludge digesters are designed for CH4 recovery and are not 

expected to emit methane directly from the digester. The IPCC methodology for estimating CH4
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emissions from industrial wastewater treatment includes a methodology for estimating emissions 

from “anaerobic digester for sludge” (IPCC, 2006; Table 6-8). 

Biogas destruction devices. Biogas destruction devices include flares, thermal oxidizers, 

boilers, turbines, internal combustion engines, or any other combustion units used to destroy or 

oxidize CH4 contained in biogas. 

2.2.2 Industries Included in the Reporting Rule 

Subpart II includes industries that both have high levels of BOD5 or COD in their 

wastewater and frequently use anaerobic treatment. For these reasons, these industries are also 

represented in the wastewater treatment sector of the U.S. GHG Inventory. These industries (pulp 

and paper mills, food processing facilities, ethanol production facilities and petroleum refineries) 

are described in more detail below. 

Pulp and Paper Mills. Pulp and paper mills are facilities that produce market pulp (i.e., 

stand-alone pulp facilities), manufacture pulp and paper (i.e., integrated facilities), produce paper 

products from purchased pulp, produce secondary fiber from recycled paper, convert paper into 

paperboard products (e.g., containers), or operate coating and laminating processes (40 CFR 

§98.270). 

Wastewater treatment for the pulp and paper industry typically includes primary 

treatment (such as screening, sedimentation, and flotation/hydrocycloning) to remove solids 

(World Bank, 1999; Nemerow and Dasgupta, 1991), followed by secondary biological treatment 

(such as activated sludge or anaerobic or aerobic lagoons). In the United States, primary 

treatment is focused on solids removal, equalization, neutralization, and color reduction (EPA, 

1993). The vast majority of pulp and paper mills with on-site treatment systems use mechanical 

clarifiers to remove suspended solids from the wastewater. About 10 percent of pulp and paper 

mills with treatment systems use settling ponds for primary treatment and most of these likely do 

not perform secondary treatment (EPA, 1993). Negligible GHG emissions are assumed to occur 

during primary treatment. 

Approximately 42 percent of the BOD5 in pulp and paper wastewater passes on to 

secondary treatment, which consists of activated sludge, aerated stabilization basins, or nonaerated stabilization basins (EPA, 1997b). No anaerobic activity is assumed to occur in activated 

sludge systems or aerated stabilization basins. However, for the Inventory, EPA assumes about 

25 percent of the wastewater treatment systems used in the United States are nonaerated 

stabilization basins. These basins are typically 10 to 25 feet deep and are classified as anaerobic 

deep lagoons. 

Food Processing Facilities. For the purpose of the Reporting Rule, food processing 

facilities are defined as those that manufacture or process meat, poultry, fruits, and/or vegetables. 

The North American Industry Classification System (NAICS) is the standard used by federal 

statistical agencies in classifying business establishments for the purpose of collecting, 

analyzing, and publishing statistical data related to the U.S. business economy. It was developed 

in 1997 to replace the Standard Industrial Classification (SIC) system (NAICS, 2007). 
2-5 

Meat or poultry processing or rendering facilities are those covered under NAICS code 

3116 (which was SIC code 201, Meat Product Manufacturing). NAICS code 3116 (Animal 

Slaughtering and Processing) is made up of the following subsectors: 

 31161 Animal Slaughtering and Processing 

This industry comprises establishments primarily engaged in one or more of the 

following: (1) slaughtering animals; (2) preparing processed meats and meat byproducts; and (3) rendering and/or refining animal fat, bones, and meat scraps. 

This industry includes establishments primarily engaged in assembly cutting and 

packing of meats (i.e., boxed meats) from purchased carcasses. 

 311611 Animal (except Poultry) Slaughtering 

This U.S. industry comprises establishments primarily engaged in slaughtering 

animals (except poultry and small game). Establishments that slaughter and 

prepare meats are included in this industry. 

 311612 Meat Processed from Carcasses 

This U.S. industry comprises establishments primarily engaged in processing or 

preserving meat and meat by-products (except poultry and small game) from 

purchased meats. This industry includes establishments primarily engaged in 

assembly cutting and packing of meats (i.e., boxed meats) from purchased meats. 

 311613 Rendering and Meat By-product Processing 

This U.S. industry comprises establishments primarily engaged in rendering 

animal fat, bones, and meat scraps. 

 (311614 is not a valid 2007 NAICS code) 

 311615 Poultry Processing 

This U.S. industry comprises establishments primarily engaged in (1) slaughtering 

poultry and small game and/or (2) preparing processed poultry and small game 

meat and meat by-products. 

Fruit or vegetable processing facilities are facilities covered under NAICS code 3114 

(which was SIC code 203, Fruit and Vegetable Preserving and Specialty Food Manufacturing). 

NAICS code 3114 (Fruit and Vegetable Preserving and Specialty Food Manufacturing) includes 

the following: (1) establishments that freeze food and (2) those that use preservation processes, 

such as pickling, canning, and dehydrating. Both types begin their production process with inputs 

of vegetable or animal origin. 

NAICS 3114 (Fruit and Vegetable Preserving and Specialty Food Manufacturing) is 

made up of the following subsectors: 

 31141 Frozen Food Manufacturing

This industry comprises establishments primarily engaged in manufacturing 

frozen fruit, frozen juices, frozen vegetables, and frozen specialty foods (except 

seafood), such as frozen dinners, entrees, and side dishes; frozen pizza; frozen 

whipped toppings; and frozen waffles, pancakes, and french toast. 
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 311411 Frozen Fruit, Juice, and Vegetable Manufacturing 

This U.S. industry comprises establishments primarily engaged in manufacturing 

frozen fruits; frozen vegetables; and frozen fruit juices, ades, drinks, cocktail 

mixes and concentrates. 

 311412 Frozen Specialty Food Manufacturing 

This U.S. industry comprises establishments primarily engaged in manufacturing 

frozen specialty foods (except seafood), such as frozen dinners, entrees, and side 

dishes; frozen pizza; frozen whipped topping; and frozen waffles, pancakes, and 

french toast. 

 31142 Fruit and Vegetable Canning, Pickling, and Drying 

This industry comprises establishments primarily engaged in manufacturing 

canned, pickled, and dried fruits, vegetables, and specialty foods. Establishments 

in this industry may package the dried or dehydrated ingredients they make with 

other purchased ingredients. Examples of products made by these establishments 

are canned juices; canned baby foods; canned soups (except seafood); canned dry 

beans; canned tomato-based sauces, such as catsup, salsa, chili, spaghetti, 

barbeque, and tomato paste, pickles, relishes, jams and jellies, dried soup mixes 

and bullions, and sauerkraut. 

 311421 Fruit and Vegetable Canning 

This U.S. industry comprises establishments primarily engaged in manufacturing 

canned, pickled, and brined fruits and vegetables. Examples of products made in 

these establishments are canned juices; canned jams and jellies; canned tomatobased sauces, such as catsup, salsa, chili, spaghetti, barbeque, and tomato paste; 

pickles, relishes, and sauerkraut. 

 311422 Specialty Canning 

This U.S. industry comprises establishments primarily engaged in manufacturing 

canned specialty foods. Examples of products made in these establishments are 

canned baby food, canned baked beans, canned soups (except seafood), canned 

spaghetti, and other canned nationality foods. 

 311423 Dried and Dehydrated Food Manufacturing 

This U.S. industry comprises establishments primarily engaged in (1) drying 

(including freeze-dried) and/or dehydrating fruits, vegetables, and soup mixes and 

bouillon and/or (2) drying and/or dehydrating ingredients and packaging them 

with other purchased ingredients, such as rice and dry pasta. 

The meat and poultry processing industry makes extensive use of anaerobic lagoons in 

sequence with screening, fat traps, and dissolved air flotation when treating wastewater on site. 

About one third of meat processing operations (EPA, 2002) and one fourth of poultry processing 

operations (U.S. Poultry, 2006) perform on-site treatment in anaerobic lagoons. 

Treatment of wastewater from fruits and vegetable processing includes screening, 

coagulation/settling, and biological treatment (lagooning). The flows are frequently seasonal, and 

robust treatment systems are preferred for on-site treatment. Effluent is suitable for discharge to 
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the sewer. Like meat and poultry processing, this industry may also use anaerobic lagoons 

(Nemerow and Dasgupta, 1991). 

The food processing facilities covered by Subpart II are the same as those in the 

industrial wastewater treatment sector of the Inventory. The Reporting Rule does not include the 

manufacturing of food products, such as the manufacture of sugar from beets or sugar cane, 

because these operations are not included in the definition of food processing. 

Ethanol Production Facilities. The Inventory describes ethanol production facilities as 

those that produce ethanol from the fermentation of sugar, starch, grain, or cellulosic biomass 

feedstocks, or produce ethanol synthetically from petrochemical feedstocks, such as ethylene or 

other chemicals. However, synthetic ethanol comprises only about 2 percent of ethanol 

production (EPA, 2007). 

Ethanol, or ethyl alcohol, is produced primarily for use as a fuel component, but is also 

used in industrial applications and in the manufacture of beverage alcohol. Ethanol can be 

produced from fermenting sugar-based feedstocks (e.g., molasses and beets), starch- or grainbased feedstocks (e.g., corn, sorghum, and beverage waste), and cellulosic biomass feedstocks 

(e.g., agricultural wastes, wood, and bagasse). Although the Department of Energy predicts 

cellulosic ethanol production will increase in the coming years, it is currently only in 

development in the United States. According to the Renewable Fuels Association, 82 percent of 

ethanol production facilities use corn as the sole feedstock and 7 percent of facilities use a 

combination of corn and another starch-based feedstock. Corn fermentation is the principal 

ethanol production process in the United States and is expected to increase through 2012. (RFA, 

2009). 

Ethanol is produced from corn (or other starch-based feedstocks) primarily by two 

methods: wet milling and dry milling. Historically, most ethanol was produced by the wet 

milling process, but now the majority is produced by the dry milling process. The wastewater 

generated at ethanol production facilities is handled in a variety of ways. Dry milling facilities 

often combine the resulting evaporator condensate with other process wastewaters, such as 

equipment wash water, scrubber water, and boiler blowdown, and treat the mixed wastewater in 

anaerobic digesters. Wet milling facilities often treat their steepwater condensate in anaerobic 

systems followed by aerobic polishing systems and may treat the stillage (or processed stillage) 

from the ethanol fermentation/distillation process separately or together with steepwater and/or 

wash water. CH4 generated in anaerobic digesters is commonly collected and either flared or 

used as fuel in the ethanol production process (ERG, 2006). EPA estimates that one-third of wet 

milling and three quarters of dry milling facilities treat wastewater anaerobically. 

Petroleum Refineries. A petroleum refinery is any facility engaged in producing gasoline, 

gasoline blending stocks, naphtha, kerosene, distillate fuel oils, residual fuel oils, lubricants, or 

asphalt (bitumen) through distillation of petroleum or through redistillation, cracking, or 

reforming of unfinished petroleum derivatives (40 CFR §98.250). 

Many refineries use oil/water separators as a primary treatment method. These treatment 

operations use gravity separation to remove oil from refinery wastewater and can emit volatile 

organic compounds (VOCs). Although these VOCs are not GHGs, they convert to CO2 in the 

atmosphere. Emissions from oil/water separators were included in the proposed rule but are not 

included in the final because the purpose of the Reporting Rule is to collect direct GHG 
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emissions data from downstream sources1 including industrial wastewater treatment. Therefore, 

the rule does not require facilities to report indirect emissions such as VOCs that can convert to 

CO2 once in the atmosphere. EPA expects no direct emissions of CO2 or other GHGs from these 

oil/water separators. Following primary treatment, most refineries use biological treatment 

systems that exhibit anaerobic conditions, resulting in CH4 production. 

Other Facilities Not Covered by the Reporting Rule. Although other industrial facilities 

may use anaerobic wastewater treatment processes that generate CH4, Subpart II applies only to 

facilities in the four categories described above. EPA has not characterized anaerobic wastewater 

treatment operations or estimated CH4 emissions in other industries. The petrochemical industry 

was included in the proposed Reporting Rule, but is not included in the final rule because 

petrochemical facilities are not known to use anaerobic wastewater treatment. 

 

1 The rule requires fuel suppliers to report indirect emissions; however, downstream sources are not required to 

report emissions of VOCs or other emissions that convert to CO2 in the atmosphere. 
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3. EMISSION ESTIMATES

During the development of the Reporting Rule, EPA estimated the number of facilities in 

each industry that will be required to report their industrial wastewater GHG emissions. EPA 

also estimated the mass of emissions expected to be reported by each industry. For these 

estimates, EPA used assumptions and methodologies developed for the Inventory. 

Each industry covered by Subpart II of the Reporting Rule (40 CFR Part 98) has different 

reporting requirements as outlined below: 

 Pulp and Paper: Mills are required to report their GHG emissions only if their 

emissions exceed 25,000 tCO2e per year in combined emissions from all 

applicable source categories in the final Reporting Rule including pulp and paper 

manufacturing, and, if present, stationary fuel combustion sources, industrial solid 

waste landfills, industrial wastewater treatment, and any others that may apply. 

 Food Processing: Facilities are required to report their GHG emissions only if 

they exceed 25,000 tCO2e per year in combined emissions from all applicable 

source categories, including, but not limited to stationary fuel combustion 

sources, industrial solid waste landfills, and industrial wastewater treatment. 

Process emissions are not included in determining the threshold, nor are facilities 

required to report process emissions. 

 Ethanol Production: Facilities are required to report their GHG emissions only if 

they exceed 25,000 tCO2e per year in combined emissions from all applicable 

source categories, including, but not limited to stationary fuel combustion 

sources, industrial solid waste landfills, and industrial wastewater treatment. 

Process emissions are not included in determining the threshold, nor are facilities 

required to report process emissions. 

 Petroleum Refining: All petroleum refineries are required to report their GHG 

emissions. Refineries must report emissions from their refinery operations and, if 

present, from stationary fuel combustion sources, industrial solid waste landfills, 

industrial wastewater treatment, and any other applicable source categories. 

The procedures EPA used to estimate the number of facilities required to report and their 

industrial wastewater treatment GHG emissions are described in the following subsections. 

3.1 Pulp and Paper Mills

EPA estimated that there are 565 pulp and paper mills in the United States (EPA, 1993). 

Using assumptions presented in the Inventory, EPA estimated that 25 percent (141) of these mills 

have anaerobic secondary treatment and would be required to report their industrial wastewater 

treatment CH4 emissions. EPA does not know the production or emissions from these mills, but 

assumed that all facilities with anaerobic wastewater treatment would have total facility 

emissions that exceed the 25,000 metric tons of CO2e per year reporting threshold. 

To estimate CH4 emissions from industrial wastewater treatment at pulp and paper mills, 

EPA used the methodology presented in the Inventory, which is summarized in Equation 3-1: 
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 CO2e = F × P × W × BOD × cf × TA × B0 × MCF × GWP (3-1) 

where: 

CO2e = CO2 equivalent of methane emissions for facilities required to report 

(tCO2e). 

F = Estimated fraction of facilities required to report (decimal). 

P = Total industry production (thousand metric ton/year). 

W = Wastewater outflow (m3/metric ton). 

BOD = Organic matter concentration in untreated wastewater, measured as BOD5

(kg/m3

). 

cf = Factor for conversion of BOD to COD (unitless) 

TA = Fraction of wastewater BOD treated anaerobically in secondary treatment 

(decimal). 

B0 = Maximum CH4-producing capacity (kg CH4/kg COD). 

MCF = Methane conversion factor for anaerobic treatment. 

GWP = Global warming potential for CH4. 

EPA estimated that pulp and paper industrial wastewater treatment emissions amount to 

4,075,044 tCO2e, using the values listed in Table 3-1. 

Table 3-1. Values Used to Estimate Pulp and Paper CH4 Emissions 

Variable Parameter Value Source 

F Estimated fraction of facilities required to 

report (decimal) 

0.25 ERG, 2008 

P Total industry production (thousand metric 

tons/year) 

135,889 EPA, 2010 

W Wastewater outflow (m3/ton) 85 World Bank, 1999 

Nemerow and Dasgupta, 1991 

BOD Organic matter concentration in untreated 

pulp and paper mill wastewater, as BOD5

(kg/m3

) 

0.4 EPA, 1997b 

EPA, 1993 

World Bank, 1999 

cf Factor for conversion of BOD to COD, 

specific to pulp and paper mill wastewater 

(kg COD/kg BOD) 

2 EPA, 1997a 

TA Fraction of pulp and paper industry 

wastewater BOD treated in secondary 

treatment 

0.42 EPA, 2010 

B0 Maximum CH4-producing capacity (kg 

CH4/kg COD)

0.25 IPCC, 2006 

MCF Methane conversion factor for anaerobic 

systems 

0.8 IPCC, 2006 

GWP Global warming potential 21 EPA, 2010 

3.2 Food Processing Facilities

Food processing facilities covered by Subpart II fall into three segments: fruits and 

vegetables processing, meat processing, and poultry processing. EPA’s estimates of the number 
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of facilities in each segment required to report and their industrial wastewater treatment CH4

emissions are discussed below. 

Fruits and vegetables processing. Based on information from the 2002 U.S. Economic 

Census for Manufacturing (U.S. Census Bureau, 2002), EPA estimated that there are 1,746 fruits 

and vegetable processing facilities in the United States. Using assumptions presented in the 

Inventory, EPA estimated that 5 to 6 percent (100) of these facilities have anaerobic secondary 

treatment resulting in emissions of 123,000 tCO2e. Thus, for 100 facilities, the average emissions 

are 1,230 tCO2e per plant per year. Because this estimate is far below the 25,000 tCO2e per year 

threshold for reporting, EPA estimated that no fruits and vegetables processing facility would be 

required to report its industrial wastewater treatment GHG emissions. 

Meat processing. Meat processing facilities are required to report their GHG emissions if 

they exceed 25,000 tCO2e per year in combined emissions from stationary fuel combustion 

sources, industrial solid waste landfills, and industrial wastewater treatment. EPA estimated the 

number of meat processing facilities that would be required to report GHG emissions based on 

emissions from industrial wastewater treatment only. EPA ignored the other sources because it 

had no information about emissions from stationary fuel combustion sources or industrial solid 

waste landfills at meat processing facilities. 

EPA had no data on meat production or GHG emissions per plant. As a result, to estimate 

the number of meat processing facilities that would emit more than 25,000 tCO2e per year from 

industrial wastewater treatment processes, EPA back-calculated the production rate that would 

result in emissions of 25,000 tCO2e using Equation 3-2. 

 P = t/(W × BOD × cf × B0 × MCF × GWP) × 1,000 kg/ton (3-2) 

where: 

P = Production resulting in GHG emissions above the reporting threshold 

(ton/year). 

W = Wastewater outflow (m3

/ton). 

BOD = Organic matter concentration in the wastewater, measured as BOD, kg/m3

. 

cf = Factor for conversion of BOD to COD (unitless) 

B0 = Maximum CH4-producing capacity (kg CH4/kg COD). 

MCF = Methane conversion factor (decimal). 

GWP = Global warming potential. 

t = Reporting threshold (25,000 tCO2e/yr). 

Using the values listed in Table 3-2. EPA estimated that 133,000 metric tons/year of meat 

production would result in industrial wastewater treatment CH4 emissions that would reach the 

25,000 t CO2e reporting threshold. 

EPA had collected limited production information when it established national effluent 

limitation guidelines and standards for this industry in 2004 (EPA, 2004a). At that time, EPA 

estimated that there were 139 meat processors that processed more than 50 million pounds 

(22,700 metric tons) per year. For the purpose of this estimate, EPA assumed that 40 facilities 

processed more than 133,000 tons/year, the tonnage that reaches the reporting threshold. EPA 

estimates that 33 percent of meat processing facilities have on-site anaerobic treatment. Thus, 
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EPA estimated that 13 meat processing facilities would be required to report their industrial 

wastewater treatment CH4 emissions and that none of these facilities recover biogas. 

Table 3-2. Values Used to Estimate Meat and Poultry Processing CH4 Emissions 

Variable Parameter Meat Processing Poultry Processing Source 

W Wastewater outflow (m3/ton) 5.3 12.5 ARCADIS, 2004 

EPA, 2004a 

BOD Organic matter concentration in the 

wastewater, measured as BOD (kg/m3

)

2.822 1.508 EPA, 2002 

ARCADIS, 2004 

cf Factor for conversion of BOD to 

COD, specific to meat and poultry 

processing wastewater (kg COD/kg 

BOD) 

3 3 EPA, 1997a 

B0 Maximum CH4-producing capacity 

(kg CH4/kg COD)

0.25 0.25 IPCC, 2006 

MCF Methane conversion factor 0.8 0.8 IPCC, 2006 

GWP Global warming potential 21 21 EPA, 2010 

EPA estimated these 13 meat processing facilities each emit 25,000 tCO2e per year, for a 

total of 325,000 tCO2e. 

Poultry processing. Like meat processing facilities, poultry processing facilities are 

required to report if their combined emissions from stationary fuel combustion sources, industrial 

solid waste landfills, and industrial wastewater treatment exceed the threshold. As with meat 

processing, EPA had no data on per plant poultry production or per plant GHG emissions. Again, 

EPA back-calculated the production rate that would result in emissions of 25,000 tCO2e using 

Equation 3-2. 

Using the values listed in Table 3-2, EPA estimated that 105,000 metric tons/year) of 

poultry production would result in industrial wastewater treatment CH4 emissions that would 

reach the 25,000 tCO2e reporting threshold. 

EPA had limited production information collected when it established national effluent 

limitation guidelines and standards for this industry in 2004 (EPA, 2004a). At that time, EPA 

estimated that there were 206 poultry processors that processed more than 100 million pounds 

(45,400 metric tons) per year. For the purpose of this estimate, EPA assumed that any of these 

206 facilities that used anaerobic wastewater treatment processes would be required to report 

their GHG emissions. EPA estimates that 25 percent of the 206 poultry processing facilities that 

process more than 100 million pounds per year have on-site anaerobic treatment. Thus, EPA 

estimated that 50 poultry processing facilities would be required to report their industrial 

wastewater treatment GHG emissions. 

EPA estimated these 50 poultry processing facilities each emit 25,000 tCO2e per year, for 

a total of 1,250,000 tCO2e. 
3-5 

3.3 Ethanol Production Facilities

Ethanol production facilities are required to report their GHG emissions if they exceed 

25,000 tCO2e per year in combined emissions from all applicable source categories, including, 

but not limited to stationary fuel combustion sources, industrial solid waste landfills, and 

industrial wastewater treatment. EPA estimated the number of ethanol production facilities that 

would be required to report GHG emissions based on emissions from industrial wastewater 

treatment only. For estimates of coverage based on combined emissions, see the TSD for Ethanol 

Production. 

Based on information from the Renewable Fuels Association (RFA, 2009), EPA 

estimated that there are 170 ethanol production facilities in the United States. Of these, EPA 

estimated that 85 percent use dry milling and 15 percent use wet milling (EPA, 2007). Using 

production information provided in the RFA data and parameter values listed in Table 3-3, EPA 

estimated CH4 emissions from industrial wastewater treatment at each ethanol production facility 

using methodology presented in the Inventory and summarized in Equation 3-1.

Table 3-3. Values Used to Estimate Ethanol Production CH4 Emissions 

Variable Parameter 

Wet Milling 

Value 

Dry Milling 

Value Source 

F Facilities with anaerobic treatment 

(decimal) 

1 0.33 ERG, 2008

P Total industry production (million 

gallons/year) 

1,494 5,006 EPA, 2010 

W Wastewater outflow (gal/gal ethanol) 

10 1.25 

Donovan, 1996 

NRBP, 2001 

Ruocco, 2006a 

Ruocco, 2006b 

Merrick, 1998 

BOD COD or BOD (kg/m3) 

BOD = 1.5 COD = 3 

Ruocco, 2006a 

Ruocco, 2006a 

Merrick, 1998 

White and Johnson, 2003 

cf Factor for conversion of BOD to 

COD, specific to ethanol production 

wastewater (kg COD/kg BOD) 

2 2 

EPA, 1997a 

B0 Maximum CH4-producing capacity 

(kg CH4/kg COD) 0.25 0.25 IPCC, 2006 

MCF Methane conversion factor 0.8 0.8 IPCC, 2006 

GWP Global warming potential 21 21 EPA, 2010 

TA Fraction of industry wastewater BOD 

treated in secondary treatment 

0.75 0.333 EPA, 2010 

EPA determined that 12 facilities that use wet milling operations had sufficient 

production to exceed the 25,000 tCO2e reporting threshold. However, only one-third of facilities 

that use wet milling are expected to use anaerobic treatment (ERG, 2008). Therefore, EPA 
3-6 

estimated that four facilities with wet milling operations will be required to report GHG 

emissions (based on emissions from industrial wastewater treatment only). 

EPA assumed that all facilities that use dry milling operations had anaerobic treatment in 

place and none operated a biomethanator2. In keeping with the Inventory estimation 

methodology, EPA assumed that 75 percent of the facilities recovered biogas from their 

anaerobic treatment processes. EPA estimated that no ethanol production facilities that use dry 

milling operations would meet the reporting threshold based on emissions from industrial 

wastewater treatment only. 

3.4 Petroleum Refineries

All petroleum refineries are required to report their GHG emissions. Refineries must 

report emissions from their refining operations and, if present, from stationary fuel combustion 

sources, industrial solid waste landfills, and industrial wastewater treatment. 

Based on information from the Energy Information Administration (EIA, 2009), EPA 

determined that there are 150 petroleum refineries in the United States. Using assumptions 

presented in 2007 Inventory, EPA estimated that 100 percent of the refineries use wastewater 

treatment that exhibits anaerobic conditions, and thus they would be required to report their 

industrial wastewater treatment CH4 emissions. Using production information from EIA (EIA, 

2009) and parameter values listed in Table 3-4, EPA estimated CH4 emissions from industrial 

wastewater treatment for petroleum refineries using methodology presented in the Inventory, as 

summarized in Equation 3-1. 

Table 3-4. Values Used to Estimate Petroleum Refinery CH4 Emissions 

Variable Parameter Value Source 

F Facilities with anaerobic treatment (decimal) 1 ERG, 2008 

P Total industry production (thousand barrels/year) 6,567,929 EPA, 2010 

W Wastewater outflow (gal/barrel produced) 35 CARB, 2007 

Timm, 1985 

COD COD (kg/m3) 0.45 Benyahia et al (2006) 

B0 Maximum CH4-producing capacity (kg CH4/kg COD) 0.25 IPCC, 2006 

MCF Methane conversion factor 0.3 a IPCC, 2006 

GWP Global warming potential 21 EPA, 2010 

TA Fraction of industry wastewater BOD treated in 

secondary treatment 

1 EPA, 2010 

a – EPA assumes refineries operate trickling filters, rotating biological contactors, or other systems that exhibit 

anaerobic conditions. Therefore, EPA selected a CH4 conversion factor of 0.3 for these treatment systems. 

EPA assumed that no petroleum refineries recover biogas and estimated that petroleum 

refinery industrial wastewater treatment emissions amount to 616,674 (tCO2e) per year (EPA, 

2007). 

 

2 A biomethanator is a specific type of anaerobic reactor, treating a higher fraction of industry wastewater BOD than 

is typically treated in secondary treatment. 
3-7 

3.5 Summary

Table 3-5 summarizes the number of plants EPA estimates will be required to report 

under the Reporting Rule and their estimated emissions. These estimates were used to calculate 

estimated cost of compliance, which can be found in Greenhouse Gas Reporting Rule, Industrial 

Wastewater Treatments Source Category, Costs for Final Rule Monitoring Requirements – 

Revised (ERG, 2010). 

Table 3-5. Estimated Number of Plants Required to Report and Estimated Emissions 

Category

No. of 

Plants in 

the U.S. 

Estimated Plants with 

Anaerobic Treatment

Estimated 

No. of Plants 

Required to 

Report

Estimated No. 

of Reporting 

Plants with 

CH4 Recovery 

Estimated 

Emissions Plants 

are Required to 

Report (tCO2e) 

Pulp and Paper 565 25% 141 0 4,075,044 

Fruits and Vegetables 

Processing 

1,746 100% have anaerobic 

treatment, but none (0) 

exceed reporting 

threshold 

0 0 123,000 

Meat Processing 3,337 33% have anaerobic 

treatment, but EPA 

estimates only 13 exceed 

the reporting threshold 

13 0 0 

Poultry Processing 536 25% have anaerobic 

treatment, but EPA 

estimates not more than 

50 exceed the reporting 

threshold 

50 0 1,250,000 

Ethanol Production - 

wet mill 

15% of 170 mills 

25 33% have anaerobic 

treatment; of those 

plants, half have enough 

production to exceed the 

reporting threshold 

4 4 21,681 

Ethanol Production - 

dry mill 

85% of 170 mills 

145 100% but none exceed 

reporting threshold 

based solely on 

wastewater treatment 

0 0 0 

Petroleum Refineries 150 100% 150 0 616,674 
4. ESTIMATING METHANE GENERATION FROM WASTEWATER TREATMENT

CH4 emissions from industrial wastewater treatment are a function of the concentration of 

soluble organic material in anaerobically treated wastewater and an emission factor that 

characterizes the extent to which waste becomes CH4 (IPCC, 2006). The emission factor is the 

product of the maximum CH4 producing capacity of the wastewater (B0) and the methane 

conversion factor (MCF) that accounts for the ability of the particular system to achieve that 

maximum CH4 production. The 2006 IPCC Guidelines for National Greenhouse Gas Inventories, 

Volume 5, Chapter 6, p.6.2.1, provide values of B0 for organic material measured as COD and as 

BOD (see Table 4-1). 

Most wastewater treatment systems will not produce the maximum amount of CH4

possible because the conditions in the systems are not ideal for CH4 production. The CH4

producing potential of a specific system is represented by a parameter known as the CH4

conversion factor (MCF). This value ranges from 0 to 100 percent and reflects the capability of a 

system to produce the maximum achievable CH4 based on the organic matter present in the 

wastewater. A higher MCF equates to a higher CH4 production. MCF values for various types of 

treatment systems are presented in the 2006 IPCC Guidelines for National Greenhouse Gas 

Inventories, Volume 5, Chapter 6, Table 6.8. The MCFs used in the Reporting Rule are listed in 

Table 4-1. 

Using the emission factors in Table 4-1 and measured concentrations of organic matter 

and flow rates, facilities covered under the Reporting Rule are required to estimate the annual 

mass of CH4 they generate from their anaerobic wastewater treatment processes3. Facilities must 

measure both the wastewater flow and the concentration of organic material entering anaerobic 

wastewater treatment processes (specifically anaerobic reactors and anaerobic lagoons) for this 

calculation, as shown in Figure 4-1. 

Figure 4-1. Methane Generation 

 

3 Operators of anaerobic sludge digesters are not required to report CH4 generated. Anaerobic sludge digesters are designed to 

recover CH4 and not emit CH4 directly from the digester apparatus. Operators of anaerobic sludge digesters are required to report 

the amount of CH4 recovered and emitted from the recovery system. See Sections 5 and 6 of this document for these 

requirements.

4-1 
To reduce the reporting burden, the Reporting Rule allows facilities to use COD in 

conjunction with Equation 4-1 or 5-day biochemical oxygen demand (BOD5) with Equation 4-2 

to calculate CH4 generation. If facilities measure COD, they should estimate the annual mass of 

CH4 generated by each anaerobic wastewater treatment process they operate, using Equation 4-1: 

 (4-1) 

 

52

1w

4 w ow GCH Flow 0.001 MCF BCOD 

where: 

CH4G = Annual mass CH4 generated from the anaerobic wastewater treatment 

process (metric tons). 

Flown = Volume of wastewater sent to an anaerobic wastewater treatment process 

in week n (m3/week). 

CODn = Average weekly concentration of COD of wastewater entering an 

anaerobic wastewater treatment process (for month n)(kg/m3). 

B0 = Maximum CH4 producing potential of wastewater (kg CH4/kg COD), use 

the value 0.25. 

MCF = CH4 conversion factor, based on relevant values in Table 3-2. 

0.001 = Conversion factor from kg to metric tons. 

w = Index for weekly measurement period. 

If facilities measure BOD5, they should estimate the annual mass of CH4 generated by 

each anaerobic wastewater treatment process they operate, using Equation 4-2: 

  (4-2) 

 

52

1w

4 w ow5, GCH Flow 0.001 MCF B BOD

where: 

CH4G = Annual mass of CH4 generated from the anaerobic wastewater treatment 

process (metric tons). 

Flown = Volume of wastewater sent to an anaerobic wastewater treatment process 

in week n (m3

/week). 

BOD5,n = Average weekly concentration of 5-day BOD of wastewater entering an 

anaerobic wastewater treatment process for month n (kg/m3

). 

B0 = Maximum CH4 producing potential of wastewater (kg CH4 /kg BOD5), use 

the value 0.6. 

MCF = CH4 conversion factor, based on relevant values in Table 3-2. 

0.001 = Conversion factor from kg to metric tons. 

w = Index for weekly measurement period. 

4-2 
4-3 

Table 4-1. Emission Factors 

Factors Default Value Units 

B0 – for facilities monitoring COD 0.25 kg CH4/kg COD 

B0 – for facilities monitoring BOD5 0.60 kg CH4/kg BOD5 

MCF – anaerobic reactor (e.g., upflow anaerobic sludge blanket, fixed film) 0.8 Fraction 

MCF – anaerobic deep lagoon (depth more than 2 m) 0.8 Fraction 

MCF – anaerobic shallow lagoon (depth less than 2 m) 0.2 Fraction 

To determine CH4 generation using Equations 4-1 or 4-2, facilities are required to 

measure both flow and either the COD or BOD5 concentration of wastewater entering the 

anaerobic wastewater treatment process once each calendar week that the process is operating, 

with at least three days between measurements. Facilities must collect samples representing 

wastewater influent to the anaerobic wastewater treatment process, following all preliminary and 

primary treatment steps, as shown in Figure 4-1. 

4.1 Flow Measurement

Flow can be measured with hydraulic structures such as flumes and weirs that are 

inserted in open channel flow (flow in conduits that are not full). Flow can also be measured with 

meters (e.g., electromagnetic, Venturi, ultrasonic) that are appropriate for closed channel flow 

(flow in a liquid-full conduit). Facilities must measure the flow rate for the 24-hour period for 

which they collect samples analyzed for COD or BOD5 concentration. Also, the flow 

measurement location must correspond to the location used to collect samples analyzed for the 

COD or BOD5 concentration. 

Facilities may measure flow rate using one of the methods specified below: 

 ASME MFC–3M–2004 Measurement of Fluid Flow in Pipes Using Orifice, 

Nozzle, and Venturi; 

 ASME MFC–5M–1985 (Reaffirmed 1994) Measurement of Liquid Flow in 

Closed Conduits Using Transit-Time Ultrasonic Flowmeters; 

 ASME MFC–16–2007 Measurement of Liquid Flow in Closed Conduits with 

Electromagnetic Flowmeters; 

 ASTM D1941 - 91(2007) Standard Test Method for Open Channel Flow 

Measurement of Water with the Parshall Flume; or 

 ASTM D5614 - 94(2008) Standard Test Method for Open Channel Flow 

Measurement of Water with Broad-Crested Weirs. 

A facility may choose another method of measurement other than those listed above; 

however, they must follow the manufacturer’s instructions for the wastewater flow measurement 

device. 

Any chosen flow measurement system must measure the entire discharge flow; it must be 

accurate and in working order, calibrated, and maintained. Facilities are required to calibrate all 

wastewater flow measurement devices prior to the first year of reporting and recalibrate them 

either biennially (every 2 years) or at the minimum frequency specified by the manufacturer. 

Wastewater flow measurement devices must be calibrated using the procedures specified by the 
4-4 

device manufacturer. For more information on flow measurement see the NPDES Compliance 

Inspection Manual, Appendix O (U.S. EPA, 2004a). 

4.2 Organic Matter Concentration Measurement and Analysis

To calculate CH4 generation, in addition to wastewater flow, facilities are also required to 

measure organic matter concentration in the form of either BOD5 or COD. Facilities must collect 

samples representative of the wastewater entering their anaerobic treatment systems. Wastewater 

typically flows through a pipe or a conduit and both the flow rate and the concentration of 

organic material in the wastewater varies over time. For example, wastewater may be discharged 

intermittently after batch food processing operations, resulting in spikes of flow and pollutant 

load into the anaerobic wastewater treatment system. 

Wastewater samples are collected in three ways: 

 Grab sample: single samples collected at one time and place. Grab samples are 

representative when the sampled stream does not vary in concentration over time. 

 Time-weighted composite sample: equal volume discrete sample aliquots 

collected at constant time intervals into one container. A time-weighted composite 

sample can be collected either manually or with an automatic sampler. Timeweighted composites are representative of the sampled stream when the flow rate 

does not vary over time. 

 Flow- proportional sample: equal volume discrete sample aliquots collected after 

a fixed stream flow intervals into one container. This can be achieved by: 

— Collecting a constant sample volume at varying time intervals proportional 

to the wastewater flow; or 

— Collecting a volume of each individual aliquot proportional to the flow, 

while maintaining a constant time interval between the aliquots. 

Flow proportional samples can be collected with an automatic sampler and a compatible 

flow measuring device, with a flow chart and an automatic sampler capable of collecting discrete 

samples, or manually by compositing individual grab samples by volume versus flow chart 

readings. 

EPA considered allowing facilities to collect grab samples if the wastewater influent to 

the anaerobic wastewater treatment process represents the discharge from a well-mixed 

wastewater storage unit (tank or pond), such that the COD or BOD5 concentration of the waste 

stream does not vary in a 24-hour period. EPA also considered allowing facilities to collect timeweighted composite samples if the flow rate of the wastewater influent to the anaerobic 

wastewater treatment process does not vary more than ±50 percent of the mean flow rate for a 

24-hour sampling period. 

However, establishing that the sampled stream meets the conditions necessary for these 

types of sampling would require the facility to collect additional samples. For this reason, the 

final Reporting Rule requires facilities to collect a flow-proportional composite sample. The 

Reporting Rule requires either a constant time interval between samples, keeping sample volume 

proportional to stream flow, or a constant sample volume with the time interval between samples 
4-5 

proportional to stream flow. The sample must represent the average COD or BOD5 concentration 

of the waste stream over a 24-hour sampling period at a location similar to that specified in 

Figure 4-1. 

Facilities are required to collect a minimum of four samples per 24-hour period, which 

should be combined for analysis. The requirement of the final Reporting Rule ensures that the 

collected sample represents the wastewater influent to the anaerobic wastewater treatment 

process, without imposing an unnecessary burden on reporters. For more information on 

sampling, see the NPDES Permit Writer’s Manual (U.S. EPA, 1996) and the NPDES 

Compliance Inspection Manual (U.S. EPA, 2004b). 

Facilities must determine the organic matter concentration in wastewater treated 

anaerobically using analytical methods for COD or BOD5 specified in 40 CFR part 136.3 

Table 1B. When determining concentrations of wastewater influent to the anaerobic wastewater 

treatment process to calculate CH4 generated, samples may be diluted to the concentration range 

of the approved method. The concentration of the diluted sample must be multiplied by the 

dilution factor to determine the concentration of the undiluted sample. The undiluted sample 

concentration is used to calculate CH4 generation. 
5. ESTIMATES OF METHANE RECOVERY

“Biogas” refers to the combination of CO2, CH4, and other gases produced by the 

biological breakdown of organic matter in the absence of oxygen. Some facilities recover some 

or all of the biogas generated by anaerobic wastewater treatment and anaerobic sludge digestion 

and route the recovered biogas to a destruction device. These devices include flares, thermal 

oxidizers, boilers, turbines, internal combustion engines, or any other combustion units used to 

destroy or oxidize CH4 contained in the biogas. Figure 5-1 depicts biogas recovery from 

anaerobic wastewater treatment. 

Figure 5-1. Diagram of Biogas Recovery from Anaerobic Wastewater Treatment 

Facilities that use aerobic processes to treat wastewater generate larger quantities of 

waste sludge and may use anaerobic digestion to reduce the volume of sludge and recover the 

biogas. Figure 5-2 depicts biogas recovery from anaerobic sludge digestion. 

5-1 
Figure 5-2. Diagram of Biogas Recovery from Anaerobic Sludge Digestion 

Subpart II of the Reporting Rule requires facilities to calculate and report the amount of 

CH4 they recover. They must calculate CH4 recovery using Equation 5-1. 

 (5-1) 



M

1m

m mCH4 CF )(C (V) R 

where: 

R = Annual quantity of CH4 recovered from anaerobic reactor, digester, or 

lagoon (metric tons CH4/yr). 

M = Total number of measurement periods in a year. Use M=365 (M=366 for 

leap years) for daily averaging of continuous monitoring. Use M=52 for 

weekly sampling. 

m = Index for measurement period. 

Vm = Cumulative volumetric flow for the measurement period in actual cubic 

feet (acf). If no biogas was recovered during a monitoring period, use 

zero. 

(CCH4)m = Average CH4 concentration of biogas during the measurement period, 

(volume %). 

CF = Correction factors for temperature, pressure, and/or moisture, if necessary. 

For Equation 5-1, facilities must determine the volume of gas recovered during a 

monitoring period and the CH4 concentration of the gas. These measured values may be 

multiplied by a number of correction factors: 

 Volumetric moisture correction term for the measurement period, based on the 

average moisture content of biogas during the measurement period; 

 Temperature at which flow is measured for the measurement period; and 

 Pressure at which flow is measured for the measurement period. 

5-2 
5-3 

If a facility continuously monitors the CH4 concentration and these correction factors 

using a meter specifically for CH4 gas, they must use this system to calculate CH4 recovery. A 

fully integrated system that directly reports CH4 content only requires the facility to sum the 

results of all monitoring periods for a given year. 

5.1 Biogas Flow Measurement

To estimate the annual mass of CH4 recovered, facilities are required to continuously 

monitor the recovered biogas flow rate. Every facility with biogas recovery from anaerobic 

wastewater treatment operations must use a gas flow meter capable of continuously measuring 

the volumetric flow rate of the recovered biogas. Facilities may measure flow rate using one of 

the methods specified below: 

 ASME MFC-3M-2004, Measurement of Fluid Flow in Pipes Using Orifice, 

Nozzle, and Venturi; 

 ASME MFC-4M-1986 (Reaffirmed 1997), Measurement of Gas Flow by Turbine 

Meters; 

 ASME MFC-6M-1998, Measurement of Fluid Flow in Pipes Using Vortex 

Flowmeters; 

 ASME MFC-7M-1987 (Reaffirmed 1992), Measurement of Gas Flow by Means 

of Critical Flow Venturi Nozzles; 

 ASME MFC-11M-2006 Measurement of Fluid Flow by Means of Coriolis Mass 

Flowmeters; 

 ASME MFC-14M-2003 Measurement of Fluid Flow Using Small Bore Precision 

Orifice Meters; or 

 ASME MFC-18M-2001 Measurement of Fluid Flow using Variable Area Meters; 

or 

 Method 2A or 2D at 40 CFR part 60, appendix A-1. 

A facility may measure biogas flow using a method other than those listed above; 

however, they must follow the manufacturer’s instructions for the gas flow measurement device. 

Each gas flow meter must be calibrated every two years or at the minimum frequency specified 

by the manufacturer. 

A facility is required to determine temperature and pressure of the biogas weekly only if 

its gas flow meter is not equipped with automatic correction for temperature, pressure, or, if 

necessary, moisture content. A facility must measure moisture content weekly if the CH4

concentration is determined on a dry basis and biogas flow is determined on a wet basis, or viceversa, and the flow meter does not automatically correct for moisture content. All temperature, 

pressure, and moisture content monitors must be calibrated using the procedures and frequencies 

specified by the device manufacturer. If the device manufacture does not provide calibration 

specifications, facilities may use an industry accepted or industry standard practice. All 

equipment must be maintained to the manufacturer’s specifications. 

5.2 Biogas Composition Monitoring

The Reporting Rule allows either continuous or weekly monitoring of the biogas CH4

concentration. If a facility has equipment that continuously monitors the CH4 concentration, the 

facility must use it. If a facility is not currently monitoring the biogas CH4 concentration, they 
5-4 

must use either installed or portable equipment to monitor it weekly. Weekly monitoring 

provides an adequate number of samples to evaluate the variability and uncertainly associated 

with CH4 generation. 

Facilities with biogas recovery from anaerobic processes must measure gas composition 

with a monitor capable of measuring the concentration of CH4 in the recovered biogas using 

either one of the methods specified below or as specified by the device manufacturer if they use 

another device. The gas composition monitors must be calibrated prior to the first reporting year 

and recalibrated either annually or at the minimum frequency specified by the manufacturer, 

whichever is more frequent. 

 Method 18 at 40 CFR part 60, Appendix A-6; 

 ASTM D1945-03, Standard Test Method for Analysis of Natural Gas by Gas 

Chromatography; 

 ASTM D1946-90 (Reapproved 2006), Standard Practice for Analysis of 

Reformed Gas by Gas Chromatography; 

 GPA Standard 2261-00, Analysis for Natural Gas and Similar Gaseous Mixtures 

by Gas Chromatography; 

 UOP539-97 Refinery Gas Analysis by Gas Chromatography; or 

 As an alternative to the gas chromatography methods, a facility may use total 

gaseous organic concentration analyzers and calculate the CH4 concentration. 
6. METHANE EMISSIONS CALCULATION

In addition to reporting CH4 generation, facilities must report the amount of CH4 emitted 

to the atmosphere. For facilities that do not recover biogas, total emissions equal the CH4

generation of each anaerobic reactor or lagoon and can be estimated using Equation 6-1. 

 CH4E = CH4G (6-1) 

where: 

CH4E = Annual mass of CH4 emissions from the wastewater treatment process 

(metric tons). 

CH4G = Annual mass of CH4 generated from the wastewater treatment process, as 

calculated in Equations 3-1 or 3-2 (metric tons). 

Leakage. Facilities that recover biogas from either anaerobic wastewater treatment 

operations or sludge digesters must take into account the inefficiency of the recovery process as 

depicted in Figure 6-1. Leakage refers to the annual mass of CH4 that is generated but not 

recovered. 

Figure 6-1. Diagram of Leakage From Anaerobic Sludge Digestion Biogas Recovery 

For anaerobic processes with biogas recovery, facilities must calculate leakage using 

Equation 6-2 by multiplying recovery (calculated using Equation 5-1) by a collection efficiency 

factor in Table 6-1. This allows facilities to quantify the amount of CH4 that is not captured by 

their destruction device. 





 





 1

CE

1

4 RLCH (6-2) 

6-1 
6-2 

where: 

CH4L = Leakage at the anaerobic process (metric tons CH4). 

R = Annual quantity of CH4 recovered from anaerobic reactor, anaerobic 

lagoon, or anaerobic digester, as calculated in Equation 5-1 (metric tons 

CH4). 

CE = CH4 collection efficiency of anaerobic process, as specified in Table 6-1

(decimal). 

Table 6-1. Collection Efficiencies of Anaerobic Processes 

Anaerobic Process Type Cover Type Methane Collection Efficiency 

Covered anaerobic lagoon (biogas capture) Bank to bank, impermeable 0.975 

Modular, impermeable 0.70 

Anaerobic sludge digester; anaerobic reactor Enclosed vessel 0.99 

Destruction Efficiency. Biogas destruction devices, such as flares, thermal oxidizers, 

boilers, turbines, internal combustion engines, and other combustion units destroy or oxidize 

CH4 contained in the biogas, producing CO2 and water. However, biogas destruction devices 

operate with less than 100 percent efficiency. This means the device exhaust gases will contain 

some CH4. At facilities with biogas recovery, reported total emissions must take into account the 

destruction of CH4 by these recovery devices. These facilities’ total annual mass of CH4

emissions are equal to their leakage rate plus their total recovery multiplied by the recovery 

device CH4 destruction efficiency (DE). Total emissions equal the quantity that leaks from the 

anaerobic process plus the quantity not destroyed in the destruction device, as shown in 

Equation 6-3. 

 CH4E = CH4L + R (1 – DE) (6-3) 

where: 

CH4E = Annual quantity of CH4 emitted (metric tons/yr). 

CH4L = Leakage at the anaerobic process, as calculated in Equation 6-2 (metric 

tons CH4). 

R = Annual quantity of CH4 recovered from the anaerobic reactor digester, or 

lagoon, as calculated in Equation 5-1 (metric tons CH4). 

DE = Destruction efficiency (i.e., the fraction of CH4 destroyed in the 

destruction device (decimal)). 

Destruction devices may be operated less than continuously. Also, a facility may operate 

more than one destruction device (e.g., they may operate a primary destruction device and a 

backup). Total emissions for facilities with biogas destruction devices must be estimated using 

Equation 6-4. 

 CH4E = CH4L + R (1 – (DE1×fDest_1)) + R (1 – (DE2 × FDest_2)) (6-4) 

where: 

CH4E = Annual quantity of CH4 emitted (metric tons/yr). 

CH4L = Leakage at the anaerobic process, as calculated in Equation 6-2 (metric 

tons CH4). 
6-3 

R = Annual quantity of CH4 recovered from the anaerobic reactor, digester, or 

lagoon, as calculated in Equation 5-1 (metric tons CH4). 

DE1 = Primary destruction device CH4 destruction efficiency (lesser of 

manufacturer’s specified destruction efficiency and 0.99). If the gas is 

transported off-site for destruction, use DE=1. 

fDest_1 = Fraction of hours the primary destruction device was operating (device 

operating hours/8760 hours per year). If the gas is transported off-site for 

destruction, use fDest=1. 

DE2 = Back-up destruction device CH4 destruction efficiency (lesser of 

manufacturer’s specified destruction efficiency and 0.99). 

fDest_2 = Fraction of hours the back-up destruction device was operating (device 

operating hours/8760 hours per year). 
7-1 

7. COSTS FOR GHG REPORTING

The Reporting Rule requires operators to monitor their CH4 -generating processes by 

measuring the amount of wastewater entering the anaerobic treatment process, the concentration 

of organic material in the wastewater prior to treatment, the volume of biogas recovered, and the 

concentration of CH4 in the recovered biogas. To determine costs of the required monitoring, 

EPA evaluated whether facilities are currently conducting this monitoring. For monitoring that is 

not routinely conducted, EPA estimated the costs that a typical facility would incur to meet the 

requirement. 

The estimates include one-time capital costs to purchase and install monitoring devices 

and recurring annual costs for analytical services, supplies, and labor. Table 7-1 summarizes the 

total costs EPA estimates will be incurred by facilities in each industry covered by Subpart II. 

EPA estimated that these monitoring requirements would cost, on average, $4,083 per year per 

facility (total annualized costs) or $1.4 million for the 358 facilities estimated to incur 

monitoring costs. For more information on the estimated costs of reporting for this Subpart, 

please see found in Greenhouse Gas Reporting Rule, Industrial Wastewater Treatments Source 

Category, Costs for Final Rule Monitoring Requirements – Revised (ERG, 2010). 
7-2 

Table 7-1. Industrial Wastewater Treatment Monitoring Costs 

National (Scaled-Up) Estimated Costs National (Scaled-Up) Esti

Category

No. of 

Plants 

Required 

to Report

%Plants 

with 

Anaerobic 

Treatment

No. of 

Plants 

with 

Anaerobic 

Treatment

No. of 

Plants 

with CH4

Recovery

WW 

Monitoring 

Costs -Cap

WW 

Monitoring 

Costs -

Annualized 

Cap 

WW 

Monitoring 

Costs -

Annual 

WW 

Monitoring 

Costs -TAC 

CH4

Recovery 

Monitoring 

Costs -Cap

CH4

Recovery 

Monitoring 

Costs -

Annualized 

Cap 

CH

Recov

Monit

Cos

Ann

Pulp and Paper 565 25% 141 0 $1,428,843 $134,873 $463,300 $598,173 0 $0 $0 Food Processing 63 100% 63 0 $455,805 $43,025 $206,640 $249,665 $0 $0 $0 Ethanol Production - wet mill 15% of 170 mills 

4 100% 4 4 $17,064 $1,611 $13,120 $14,731 $23,600 $2,228 $3,6

Ethanol Production - dry mill 85% of 170 mills 

0 75% 0 0 $0 $0 $0 $0 $0 $0 $0 

Petroleum Refineries 

150 100% 150 0 $1,085,250 $102,440 $492,000 $594,440 $0 $0 $0 

Total 358 

Cap – Capital costs. TAC – Total annualized costs (annualized capital costs plus annual costs). 
8-1 

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