February 4, 2009
TECHNICAL SUPPORT DOCUMENT FOR
MANURE MANAGEMENT SYSTEMS: PROPOSED
RULE FOR MANDATORY REPORTING OF
GREENHOUSE GASES
Climate Change Division
Office of Atmospheric Programs
U.S. Environmental Protection Agency
February 4, 2009
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CONTENTS
1. Industry Description 3
2. Total Emissions 3
3. Review of Existing Programs and Methodologies 3
4. Types of Emissions Information to be Reported 4
4.1 Types of Emissions to be Reported 4
4.2 Other Information to be Reported 4
5. Options for Reporting Threshold 5
5.1 Emissions-based Thresholds 5
5.2 Other Threshold Options 9
6. Options for Monitoring Methods 10
6.1 Calculating Methane Generation 10
6.2 Calculating Methane Generation of Digesters 12
6.3 Calculating Methane Destruction and Leakage of Digesters 13
6.4 Calculating Nitrous Oxide Emissions 13
6.5 Calculating Generation and Emissions 14
6.6 Calculating CH4 Generation and Emissions Using Digester Gas Collection Data 15
6.7 Direct Measurement of Emissions 15
7. Options for Estimating Missing Data 15
8. QA/QC Requirements 15
9. References 16
Appendix A. Additional information 17
Table A-1. Manure Management System Descriptions 17
Table A-2. Waste Characteristics Data 18
Table A-3. Methane Conversion Factors 19
Table A-4. Collection Efficiencies of Anaerobic Digesters 20
Table A-5. Nitrous Oxide Emission Factors 20
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1. Industry Description
This source category consists of manure management systems for livestock manure. A
manure management system is a system that stabilizes or stores livestock manure in one
or more of the following system components: uncovered anaerobic lagoons, liquid/slurry
systems, storage pits, digesters, drylots, solid manure storage, feedlots and other dry lots,
high rise houses for poultry production (poultry without litter), poultry production with
litter, deep bedding systems for cattle and swine, and manure composting. This
definition of manure management system encompasses the treatment of wastewaters from
manure. For the purposes of this rule, this source category does not include components
at a livestock operation unrelated to the stabilization or storage of manure such as daily
spread or pasture/range/paddock systems. Manure management system component
descriptions are provided in Table A-l.
When livestock or poultry manure are stored or treated, the anaerobic decomposition of
materials in the manure management system produces CFLi, while N2O is produced as
part of the nitrogen cycle through the nitrification and denitrification of the organic
nitrogen in livestock manure and urine. The amount and type of emissions produced are
related to the specific types of manure management systems used at the farm, and are
driven by retention time, temperature, and treatment conditions.
2. Total Emissions
In the United States, approximately 13 million dairy cattle, 88 million beef cattle, 62
million hogs, and 2 billion poultry (broilers, turkeys, hens, and chickens)1 are being
raised on approximately 1 million farms (i.e., 92,000 dairy farms, 796,000 beef farms,
79,000 hog farms, and 130,000 poultry farms2). In 2006, CFLi emissions from manure
management systems at these farms totaled 41.4 million metric tons of carbon dioxide
equivalents (mmtCC^e), and N2O emissions were 14.3 mmtCC^e; manure management
systems account for 8 percent of total anthropogenic CH4 emission and 3 percent of N2O
emissions in the United States.3
3. Review of Existing Programs and Methodologies
For this proposal, EPA reviewed several protocols and programs for monitoring and/or
estimating GHG including the 2006 IPCC Guidelines, the U.S. GHG Inventory,
California AB32, California Climate Action Registry, U.S. Energy Information
1 EPA. 2006 GHG Inventory for Manure Management.
2 USDA. 2002 Census of Agriculture.
3 EPA (2008) Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2006.
http://www.epa.gov/climatechange/emissions/usinventorvreport.html
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Administration Voluntary GHG Reporting Program (1605b), EPA Climate Leaders, The
Climate Registry, UNFCCC Clean Development Mechanism, EPA AgStar, and Chicago
Climate Exchange. These methodologies are all based on the IPCC guidelines.
In addition, EPA reviewed programs for obtaining and recording information from farms,
including USDA's Animal and Plant Health Inspection Service (APHIS), USDA Census
of Agriculture, and the National Pollutant Discharge Elimination System (NPDES).
These data sources do not currently collect information that could be used for the purpose
of estimating farm-level GHG emissions.
4. Types of Emissions Information to be Reported
4.1 Types of Emissions to be Reported
Based on the review of existing programs and the emission sources at landfills, GHG
reporting for manure management systems is limited to CH4 and N2O. Manure
management also produces CO2; however, this CC>2 is not counted in GHG totals as it is
not considered an anthropogenic emission. Likewise, CC>2 resulting from the combustion
of digester CH4 is not accounted as an anthropogenic emission under international
accounting guidance. For reporting options for stationary combustion (including digester
gas combustion for energy and combustion of fossil fuels used to assist gas combustion
efficiency), refer to EPA-HQ-OAR-2008-0508-004.
Manure management systems which include one or more of the following components
are to report emissions under this rule: manure handling in uncovered anaerobic lagoons,
liquid/slurry systems, pits, digesters, and drylots, including systems that combine drylot
with solid storage. Emissions to be reported include those from the systems listed above,
and also emissions from any high rise houses for caged laying hens, broiler and turkey
production on litter, deep bedding systems for cattle and swine, and manure composting
occuring onsite as part of the manure management system. This source category does not
include systems which consist of only components classified as daily spread, solid
storage, pasture/range/paddock, or manure composting.
4.2 Other Information to be Reported
In order to check the reported GHG emissions for reasonableness and for other data
quality considerations, additional information about the emission sources is needed. It is
recommended that, in addition to N2O and CH4 emissions, each reporting CH4
management system should also report methane generation and, if applicable, CH4
combustion annual quantities. Additionally, it is recommended that the following data
also be submitted with the annual report:
Data to report
a. Type(s) of manure management system (MMS)
b. Animal population (by animal type)
c. Monthly volatile solids content of excreted manure
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d. Percent of manure handled in each MMS
e. BO value used (most will use IPCC)
f. Methane conversion factor used (most will use IPCC)
g. Average animal mass (for each type of animal)
h. Monthly nitrogen content of excreted manure
i. N2O emission factor selected (most will use IPCC)
j. CH4 generation
k. N2O emissions
Manure management systems that include digesters report the following as
well
a. Total volumetric biogas flow
b. Average annual CH4 concentration
c. Temperature at which gas flow is measured
d. Pressure at which gas flow is measured
e. Destruction efficiency used
f. CH4 destruction
g. CH4 generation
EPA considered requesting farms to report only CH4 andN2O emissions or generation;
these options were not chosen because without reporting input data, including CH4
combustion data, insufficient information is available for QA/QC of the reported
emissions. Alternatively, EPA considered reporting of only emissions and combustion
data, but without reporting input data; again, insufficient information is available for
QA/QC of the reported emissions.
Regarding the frequency of reporting, EPA considered both annual and quarterly
reporting. Although emissions could fluctuate seasonally at manure management
systems, annual reporting of emissions is sufficient for these sources.
5. Options for Reporting Threshold
5.1 Emissions-based Thresholds
In developing the threshold for manure management, EPA considered thresholds of
1,000, 10,000, 25,000, and 100,000 metric tons CO2e of CH4 generation and N2O
emissions at a manure management system ("generation threshold"), and CH4 and N2O
emissions at manure management systems ("emissions threshold"). The "generation
threshold" is the amount of CH4 and N2O that would be emitted from the facility if no
CH4 destruction takes place. This includes all CH4 generation from all manure
management system types, including digesters, and N2O emissions. The "emissions
threshold" includes the CH4 and N2O that is emitted to the atmosphere from these
facilities. In the emissions threshold, CH4 that is destroyed at digesters is taken into
account and deducted from the total CH4 generation calculated.
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One option EPA analyzed would require farms with combined CH4 and N2O emissions of
25,000 mtCO2e (i.e., CH4and N2O emitted at a manure management system) to report
emissions. At this proposed threshold, EPA estimates that 43 farms would report,
including approximately 11 beef feedlots, 25 dairy farms, and 7 swine farms, or less than
1 percent of any of these farm types. This represents approximately 6 percent of the GHG
emissions from beef operations, 4 percent of the GHG emissions from dairy operations,
and 1 percent of the GHG emissions from swine operations.
The emissions included in the emission threshold are the CH4 and N2O that is directly
emitted to the atmosphere from these systems. In the emission threshold, CH4
combustion is taken into account. The evaluation of whether or not a farm may exceed
the generation threshold does not take biogas recovery and combustion operations into
account; therefore the generation number calculated can be considered the maximum
amount of GHGs that could be emitted from the facility.
EPA developed a number of model farms to represent the manure management systems
that are most common on large farms and have the greatest potential to exceed the GHG
thresholds. These model farms include:
• A beef farm with a pasture system;
• A beef feedlot;
• A dairy farm with an uncovered anaerobic lagoon system without solid
separation;
• A dairy farm with an uncovered anaerobic lagoon system with solid separation;
• A dairy farm with a liquid/slurry system without solid separation;
• A dairy farm with a liquid/slurry system with solid separation;
• A farrow-to-finish swine farm with a deep pit system;
• A farrow-to-finish swine farm with an uncovered anaerobic lagoon system;
• A caged layer farm with an uncovered anaerobic lagoon system;
• A caged layer farm with manure drying;
• A turkey farm with bedding (litter); and
• A broiler farm with bedding (litter).
Using the EPA GHG inventory methodology for manure management4, the numbers of
livestock that would need to be present to exceed the 1,000 mtCC^e, 10,000 mtCC^e,
25,000 mtCO2e, and 100,000 mtCC^e thresholds were estimated. These estimates are
presented in Table 1.
EPA combined the numbers of livestock required on each model farm to meet the
thresholds with U.S. Department of Agriculture (USD A) data on farm sizes to determine
how many farms in the United States have the livestock populations required to meet the
GHG thresholds for each model farm. The numbers of farms above the generation and
4 EPA (2008) Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2006.
http://www.epa.gov/climatechange/emissions/usinventorvreport.html
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emissions thresholds are presented in Table 2. The emissions from the farms over the
generation and emissions thresholds are presented in Table 3.
For information on assumptions and details on the analysis, please see the ERG
memorandum dated January 20, 2009, Threshold Livestock Head Count Analysis for
Manure Management and Threshold Farm Count Analysis for Manure Management.
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Table 1. Threshold Populations for All Model Farms
Animal Type
Beef
Dairy
Swine
Poultry
Model Farm
Name
Beef Farm 1
Beef Farm 2
Dairy Farm la
Dairy Farm Ib
Dairy Farm 2a
Dairy Farm 2b
Swine Farm 1
Swine Farm 2
Poultry Farm 1
Poultry Farm 2
Poultry Farm 3
Poultry Farm 4
Model Farm Description
All beef cattle types on pasture
Steers and heifers on feedlot
Cows using anaerobic lagoon without solid
separation, heifers and calves on dry lot with
runoff pond
Cows using anaerobic lagoon with solid
separation, heifers and calves on dry lot with
runoff pond
Cows using liquid/slurry without solid
separation, heifers and calves on dry lot with
runoff pond (using average MCF for
liquid/slurry)
Cows using liquid/slurry with solid
separation, heifers and calves on dry lot with
runoff pond (using average MCF for
liquid/slurry)
Farrow-to-Finish operations with deep pit
system
Farrow-to-Finish operation with an anaerobic
Lagoon
Layers and pullets on anaerobic lagoon WMS
Layers and pullets without bedding
Turkeys on bedding
Broilers on bedding
Population Unit
Total number of head
Total number of head
Number of Dairy Cows
Number of Dairy Cows
Number of Dairy Cows
Number of Dairy Cows
Total number of head
Total number of head
Total number of head
Total number of head
Total number of head
Total number of head
Population at Threshold Levels
1,000
tCO2e
39,129
3,557
201
334
447
520
6,848
2,914
39,464
1,465,586
420,458
2,073,570
10,000
tCO2e
391,290
35,569
2,012
3,234
4,468
5,201
68,481
29,135
358,012
13,295,708
3,814,371
18,811,308
25,000
tCO2e
978,224
88,923
5,029
8,341
11,171
13,004
171,203
72,839
895,029
33,239,269
9,535,927
47,028,270
100,000
tCO2e
3,912,987
355,690
20,115
48,712
44,684
52,015
684,811
291,354
3,580,116
132,957,076
38,143,709
188,113,078
Note: Estimates presented have not been adjusted to account for significant figures.
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Table 2: Number of Farms Estimated at Each Threshold
Threshold Levels
(tCO2eq)
Generated
Emissions
1,000
10,000
25,000
100,000
1,000
10,000
25,000
100,000
Beef
Dairy
Swine
Total
Number of Farms
1,071
107
11
0
5,118
259
25
0
2,885
84
8
0
9,074
450
44
0
Number of Farms
1,071
107
11
0
5,095
254
25
0
2,883
84
7
0
9,049
445
43
0
Table 3: Total Emissions from Farms at Each Threshold
Threshold Levels
(tCO2eq)
Generated
Emissions
1,000
10,000
25,000
100,000
1,000
10,000
25,000
100,000
Beef
Dairy
Swine
Total
Total tCO2eq
6,418,122
2,855,842
570,068
0
18,900,130
4,168,058
806,258
0
9,087,438
1,279,430
298,534
0
34,405,690
8,303,330
1,674,860
0
Total tCO2eq
6,418,122
2,855,842
570,068
0
18,663,556
4,088,926
806,258
0
8,843,511
1,085,912
105,016
0
33,925,188
8,030,681
1,481,342
0
5.2 Other Threshold Options
EPA considered several other threshold options for reporting emissions:
1. All manure management systems regardless of size, treatment processes, or control
technology.
2. All anaerobic manure management systems.
3. Systems of a certain size (volatile solids or manure).
4. Systems of a certain size (population of animals served by system).
5. Systems of a certain design capacity.
EPA determined that Option 1 above would result in reporting from more than 1 million
livestock farms in the United States. There are a large number of anaerobic manure
management systems in the United States, many of them contribute very low amounts of
emissions and manage manure for very small livestock populations. Option 2 would result in
many reporters who are mostly small emitters.
Regarding Option 3, volatile solids and manure amounts are not highly correlated with
emissions from manure management because there are many factors that influence emissions
from manure (i.e., management system type, temperature). Similarly under Option 4, livestock
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population size is a weak indicator of emissions from a manure management system because of
the many factors that influence emissions from manure. Finally, under Option 5, system design
capacity is not a good indicator of emissions from a manure management system, because of the
many other factors that influence emissions from manure (i.e., livestock population served by
the system, volatile solids content of manure, management system type, and temperature).
6. Options for Monitoring Methods
One option for the monitoring method involves the use of activity data, such as the number of
head of livestock, operational characteristics (e.g., physical and chemical characteristics of the
manure, type of management system(s)), and climate data, with the Intergovernmental Panel on
Climate Change (IPCC) method to calculate CFLi generation and N2O emissions and measured
values for gas combustion. This approach allows the use of default factors, such as a system
emission factor, for certain elements of the calculation, and encourages the use of site-specific
data wherever possible. The cost of such an approach is usually low, but the uncertainty can be
high. For additional information on this method, please see IPCC 20065 and EPA 20086.
6.1 Calculating Methane Generation
To estimate the amount of CFLi generated from manure, the amount of volatile solids in the
manure management system must be determined by using:
• A calculation of the quantity of manure entering the system using livestock population
data and default values for average animal mass and manure generation; and
• Monthly sampling and testing of excreted manure for total volatile solids content.
Average annual populations may be estimated in a variety of ways, depending on the available
data and the type of animal population. For static populations (dairy cows, breeding swine,
layers), the average population may be estimated by performing a one-time animal inventory.
Average annual populations for growing populations (meat animals such as beef cattle, market
swine, broilers, and turkeys) are more difficult to estimate, because these animals are generally
alive for only part of a complete year. The average annual population for these populations may
be estimated using the average number of days alive, the number of animals produced annually,
and an equation that is presented in 2006 IPCC Guidelines for National Greenhouse Gas
Inventories, Volume 4, Chapter 10, Equation 10.1.
Farm-specific values for average animal mass of each livestock type may be estimated in a
variety of ways, depending on the available data and the type of animal population. Default
values may be used for the TAM if farm-specific values are not available; default values are
available in the Table A-2 and in 2006 IPCC Guidelines for National Greenhouse Gas
Inventories., Volume 4, Chapter 10, Table 10A4-10A9. For static populations (dairy cows,
breeding swine, layers), the average animal mass may be estimated by performing a one-time
5 IPCC 2006. Chapter 10: Emissions from Livestock and Manure Management. IPCC (Volume 5 Agriculture, Forestry, and
other Land Use). Available at http://www.ipcc-nggip.iges.or.jp/public/2006gl/pdf/4_Volume4/V4_l 0_ChlO_Livestock.pdf
6 EPA 2008. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2006. Chapter 6: Agriculture, and Annex 3.10:
Methodology for Estimating CH4 and N2O Emissions from Manure Management.
http://www.epa.gov/climatechange/emissions/usinventorvreport.html
10
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assessment of the average herd TAM. For growing populations (meat animals such as beef
cattle, market swine, broilers, and turkeys) average animal mass may be estimated using the
following equation:
Average animal mass = Starting weight + Finished weight - Starting weight
2
After the population and typical animal mass have been determined, the total volatile solids
(TVS) may be calculated using the equation below:
TVS = %TVS * (Population * TAM * MER/1000)
Where:
TVS = Total volatile solids excreted per animal type (kg/day).
%TVS = Annual average percent total volatile solids by animal type, as
determined from monthly manure monitoring as specified in §98.364
(decimal).
Population = Average annual animal population (head).
TAM = Typical animal mass, using either default values in Table A-2 or farm-
specific data (kg/head).
MER = Manure excretion rate, using either default values in Table A-2 or farm-
specific data (kg manure/day/1000 kg animal mass).
Next, the maximum amount of CFLi that could potentially be produced by the manure under
ideal conditions is calculated by multiplying the volatile solids by the maximum CFLt-producing
capacity of the manure (Bo). The B0 values for manure vary by animal type and diet. The B0
values used in the U.S. GHG inventory for manure management have been determined through
laboratory tests and documented in peer reviewed journals; these values are presented in Table
A-2 and documented in the 2006IPCC Guidelines for National Greenhouse Gas Inventories,
Volume 4, Chapter 10, Table 10A4-10A9.
Most manure management systems will not produce the maximum amount of CFLt possible
because the conditions in the systems are not ideal for CFLi production. The CFLt-producing
potential of a specific manure management system is represented by a parameter known as the
methane conversion factor (MCF). This value ranges from 0 to 100 percent and reflects the
capability of a system to produce the maximum achievable CFLi based on the readily
biodegradable organic matter present in the manure. A higher MCF equates to a higher CFLr
producing potential. For liquid systems, MCF values are temperature dependent, so the average
ambient temperature of the system location must be known in order to choose the appropriate
MCF for the system. MCF values are presented in Table A-3, and are from the 2006 IPCC
Guidelines for National Greenhouse Gas Inventories, Volume 4, Chapter 10, Table 10.17.
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The equation proposed to calculate CH4 generation from manure management systems is
presented below:
A = CH4 Generation (kg/yr) =
X an^tJX -s [TVS * VS»s * Days * Bo * MCF»s] * 0.662 kg CH4/m3]
Where:
TVS = Total volatile solids excreted by animal type (kg/day).
VSMMS = Percent of manure that is managed in each MMS (decimal), (assumed
to be equivalent to the amount of VS in each system).
Days = Number of days in the reporting year (days/yr).
BO = Maximum CH4-producing capacity, as specified in Table A-2
(m3 CH4/kg VS).
MCFMMs = CH4 conversion factor for MMS, as specified in Table A-3 (decimal).
6.2 Calculating Methane Generation of Digesters
If the operation has a digester, EPA proposes that the CH4 generation of the digester be
measured. Direct measurement to determine CH4 generation from digesters depends on two
measurable parameters: 1) the rate of gas flow to the combustion device; and 2) the CH4 content
in the gas flow. These can be quantified by directly measuring the gas stream to the destruction
device(s). The gas stream may be measured by continuous metering or monthly sampling.
For continuous metering, the recommended instrumentation measures both flow and gas
concentration. Several direct measurement instruments also use a separate recorder to store and
document the data. A fully integrated system that directly reports CH4 content requires no other
calculation than summing the results of all monitoring periods for a given year. Internally, the
instrumentation is performing its calculations using algorithms similar to Equation B below.
For monthly sampling, the two primary instruments used are a gas flow meter and a gas
composition meter. The gas flow meter must be installed as close to the gas combustion device
as possible to measure the amount of gas reaching the device. Two procedures are used for data
collection in the monthly monitoring method:
1. Calibrate monitoring instrument in accordance with the manufacturer's specifications.
2. Collect four sets of data: flow rate (ft3/minute); CH4 concentration (percent);
temperature (°R); and pressure (atm). The measurements should be taken before any
treatment equipment and using a monitoring meter specifically for CH4 gas.
The amount of CH4 generated from the digester is calculated using Equation B.
B = CH4 Generation of Digester (kg/yr) =
V (V * Jk_ * 0.0423 * ^^ * -3s- * 1,440 minutes/day * kll°gmm * Days
tt( 100% Tn latm 2.20462 pounds
Where:
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CH4D = Methane Combustion of Digester(kg CH4/yr)
Vn = Daily average volumetric flow rate for day n, as determined from daily
monitoring (acfm).
Cn = Daily average CH4 concentration of digester gas for day n , as
determined from daily monitoring (%, wet basis)
0.0423 = Density of CH4 Ib/scf (at 520°R or 60°F and 1 atm).
Tn = Temperature at which flow is measured for day n(°R).
Pn = Pressure at which flow is measured for day n (atm).
Days = Number of days in the reporting year (days/yr).
6.3 Calculating Methane Destruction and Leakage of Digesters
To estimate CH4 destruction at digesters, the destruction efficiency of the combustion
equipment and the amount of time that the combustion equipment is operating is applied to the
amount of methane generated by the digester (Equation B) estimated above.
C = Methane Destruction of Digesters (kg/yr) =
CH4D * DE * OH/Hours
Where:
CH4D = Annual quantity of CH4 generated by digester, as calculated in Equation
B (kg CH4/yr).
DE = CH4 destruction efficiency from flaring or burning in engine (lesser of
manufacturer's specified destruction efficiency and 0.99).
OH = Number of hours destruction device is functioning in reporting year
Hours = Hours in reporting year
To estimate CH4 leakage at digesters, an estimate of the collection efficiency is applied to the
amount of methane generated by the digester (Equation B) estimated above. The leakage from
digesters is estimated in Equation D.
D = CH4 Leakage at Digesters (kg/yr) =
Where:
CH4D = Annual quantity of CH4 generated by digester, as calculated in Equation
B (kg CH4/yr)
CE = CH4 collection efficiency of anaerobic digester, as as specified in Table
A-4 (decimal)
6.4 Calculating Nitrous Oxide Emissions
To estimate N2O emissions from manure management systems, the amount of nitrogen in the
manure management system must be determined by using:
• A calculation of the quantity of manure entering the system using livestock population
data and default values for average animal mass and manure generation; and
• Monthly sampling and testing of excreted manure for total nitrogen content.
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The estimation of population and typical animal mass is detailed in Section 6.1. After the
population and typical animal mass have been determined, the total nitrogen excreted (Nex) may
be calculated using the equation below:
x (Population x TAM x MER/1000)
Where:
Nex = Total nitrogen excreted per animal type (kg/day)
NManure = Annual average percent of nitrogen present in manure by animal type, as
determined from monthly manure monitoring (decimal)
Population= Average annual animal population (head)
TAM = Typical animal mass, using either default values in Table A-2 or farm-
specific data (kg/head)
MER = Manure excretion rate, using either default values in Table A-2 or farm-
specific data (kg manure/day/ 1000 kg animal mass)
Each manure management system has an associated N2O emission factor (EF). These emission
factors are available in Table A- 5 and the 2006 IPCC Guidelines for National Greenhouse Gas
Inventories, Volume 4, Chapter 10, Table 10A4-10A9, and default Nex values are available in
the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Volume 4, Chapter 10,
Table 10.21.
The equation to calculate direct N2O emissions from manure management systems is presented
below:
E = Direct N2O Emissions (kg/yr) =
* animal type [* MMS Nex X Nex,MMS X EFMMS X Days] X 44
N2O/28 N2O-N] (Eq. JJ-6)
Where:
Nex = Total nitrogen excreted per animal type (kg/day)
N£X,MMS = Percent of manure that is managed in each MMS (decimal), (assumed to
be equivalent to the amount of Nex in each system)
EFMMS = Emission factor for MMS, as specified in Table A-5 (kg N2O-N/kg N)
Days = Number of days in the reporting year (days/yr).
6.5 Calculating Generation and Emissions
Estimate the greenhouse gas generation from a manure management system by converting the
CFLt emissions from the manure management system (A), CFLt generation from any digesters
(B), and the N2O emissions from the manure management system (E) into common units
equivalents, then summing them.
Generation = A + B + E
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Reporters will also estimate emissions. For systems without digesters, emissions equal
"Generation" in the equation above. For systems with digesters, emissions will be calculated by
adding the CH4 emissions from manure management systems other than the digester (A), the
methane generation from digesters (B), the N2O emissions from manure management systems
other than the digesters (E), then subtracting the CFLt combustion from digesters (C) and adding
the CH4 leakage from digesters (D). All parameters should be converted to a common unit
(CC>2 equivalents) before the calculation occurs.
Emissions = A + B-C + D + E
6.6 Calculating CH4 Generation and Emissions Using Digester Gas Collection Data
EPA also considered using gas collection data (metered) and an estimate of collection system
efficiency to calculate emissions. The advantage of this method is that it uses metered data. But
it is difficult to estimate collection efficiency, and studies have given greatly varying values for
collection efficiency.
6.7 Direct Measurement of Emissions
Direct measurement is another option EPA considered. This method allows for site-specific
measurements, but it is very costly and might not be accurate if the measuring system has
incomplete coverage.
7. Options for Estimating Missing Data
A complete record of all measured parameters used in the GHG emissions calculations is
required. Therefore, whenever a quality-assured value of a required parameter is unavailable
(e.g., if a meter malfunctions during unit operation or if a required fuel sample is not taken), a
substitute data value for the missing parameter shall be used in the calculations, according to the
following requirements:
For missing gas flow rates, volatile solids, or nitrogen or methane content data, the substitute
data value shall be the arithmetic average of the quality-assured values of that parameter
immediately preceding and immediately following the missing data incident. If, for a particular
parameter, no quality-assured data are available prior to the missing data incident, the substitute
data value shall be the first quality-assured value obtained after the missing data period.
8. QA/QC Requirements
In evaluating options for QA/QC requirements, EPA considered requiring reporters to maintain
monthly population records for each livestock type using the manure management system and
records on gas flow and CH4 content to combustion device; EPA could use these data to check
the estimated emissions submitted by the entity. EPA also considered requesting that reporters
use EPA-provided national emission factors for CFLt and N2O per animal and system type to
check against calculated emissions, but believes there is too much variability to compare
average national data to a specific system.
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9. References
CARB (California Air Resource Board). 2008. Regulation For The Mandatory Reporting of
Greenhouse Gas Emissions: Second 15-Day Modified Regulatory Language For Public
Comment. Available at:
http://www.arb.ca.gov/regact/2007/ghg2007/ghgattachment 1.pdf. May 15.
IPCC. 2006. 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for
National Greenhouse Gas Inventories. Volume 2, Energy; Chapters 2 and 4. Available
at: http://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html.
U.S. Department of Energy (DOE). Technical Guidelines: Voluntary Reporting Of Greenhouse
Gases (1605(B)) Program. Section I.E. 4.1.6. Iron and Steel Production. January 2007.
U.S. Environmental Protection Agency. 2008. Inventory of Greenhouse Gas Emissions and
Sinks: 1990-2006. EPA-430-R-08-005. Office of Atmospheric Programs, Washington,
DC. April 15.
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Appendix A. Additional information
Table A-l. Manure Management System Descriptions.
System
Pasture/Range/Paddock
Daily spread
Solid storage
Dry lot
Liquid/Slurry
Uncovered anaerobic lagoon
Pit storage below animal
confinements
Digester
Burned for fuel
Cattle and swine deep
bedding
Composting- static a
Composting- in vessel a
Composting- intensive
windrow3
Composting- passive
windrow3
Poultry manure with litter
Poultry manure without litter
Aerobic treatment
Description
The manure from pasture and range grazing animals is allowed to lie as deposited, and is not
managed.
Manure is routinely removed from a confinement facility and is applied to cropland or pasture
within 24 hours of excretion.
The storage of manure, typically for a period of several months, in unconfined piles or stacks.
Manure is able to be stacked due to the presence of a sufficient amount of bedding material or loss
of moisture by evaporation.
A paved or unpaved open confinement area without any significant vegetative cover where
accumulating manure may be removed periodically.
Manure is stored as excreted or with some minimal addition of water to facilitate handling and is
stored in either tanks or earthen ponds, usually for periods less than one year.
Uncovered anaerobic lagoons are designed and operated to combine waste stabilization and
storage. Lagoon supernatant is usually used to remove manure from the associated confinement
facilities to the lagoon. These lagoons are designed with varying lengths of storage (up to a year
or greater), depending on the climate region, the volatile solids loading rate, and other operational
factors. The water from the lagoon may be recycled as flush water or used to irrigate and fertilize
fields.
Collection and storage of manure usually with little or no added water typically below a slatted
floor in an enclosed animal confinement facility, usually for periods less than one year.
Animal excreta with or without straw are collected and anaerobically digested in a large
containment vessel or covered lagoon. Digesters are designed and operated for waste stabilization
by the microbial reduction of complex organic compounds to CO2 and CH4, which is captured and
flared or used as fuel.
The dung and urine are excreted on fields. The sun dried dung cakes are burned for fuel.
As manure accumulates, bedding is continually added to absorb moisture over a production cycle
and possibly for as long as 6 to 12 months. This manure management system also is known as a
bedded pack manure management system and may be combined with a dry lot or pasture.
Composting, typically in an enclosed channel, with forced aeration and continuous mixing.
Composting in piles with forced aeration but no mixing.
Composting in windrows with regular turning for mixing and aeration.
Composting in windrows with infrequent turning for mixing and aeration.
Similar to cattle and swine deep bedding except usually not combined with a dry lot or pasture.
Typically used for all poultry breeder flocks and for the production of meat type chickens
(broiler) and other fowl.
May be similar to open pits in enclosed animal confinement facilities or may be designed and
operated to dry manure as it accumulates. The latter is known as a high-rise manure management
system and is a form of passive windrow composting when designed and operated properly.
The biological oxidation of manure collected as a liquid with either forced or natural aeration.
Natural aeration is limited to aerobic and facultative ponds and wetland systems and is due
primarily to photosynthesis.
a Composting is the biological oxidation of a solid waste including manure usually with bedding or another organic carbon source
typically at thermophilic temperatures produced by microbial heat production.
Source '.2006IPCC Guidelines for National Greenhouse Gas Inventories.
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Table A-2. Waste Characteristics Data
Animal Group
Dairy Cows
Dairy Heifers
Feedlot Steers
Feedlot Heifers
Market Swine <60 Ibs.
Market Swine 60-1 19 Ibs.
Market Swine 120-179 Ibs.
Market Swine >180 Ibs.
Breeding Swine
Feedlot Sheep
Goats
Horses
Hens >/= 1 yr
Pullets
Other Chickens
Broilers
Turkeys
Animal group typical
animal mass (kg)
604
476
420
420
16
41
68
91
198
25
64
450
1.8
1.8
1.8
0.9
6.8
Manure Excretion Rate
(kg/day/1000 kg animal
mass)
80.34
85
51.2
51.2
106
63.4
63.4
63.4
31.8
40
41
51
60.5
45.6
60.5
80
43.6
Maximum Methane
Generation
Potential, B0 (m3 CH^kg
VS added)
0.24
0.17
0.33
0.33
0.48
0.48
0.48
0.48
0.48
0.36
0.17
0.33
0.39
0.39
0.39
0.36
0.36
Source '.EPA 2008, U.S. Greenhouse Gas Inventory for Manure Management
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Table A-3. Methane Conversion Factors
System
Aerobic Treatment
Cattle Deep Litter (<1 month)
Cattle Deep Litter (>1 month)
Manure Composting - hi Vessel
Manure Composting - Static Pile
Manure Composting-Extensive/
Passive
Manure Composting-Intensive
Solid storage
Poultry manure with litter
Poultry manure without litter
Dry lot
Pit storage <1 month
Pit storage >1 month
Liquid/slurry (with crust cover)
Liquid/slurry (w/o crust cover)
Uncovered Anaerobic Lagoon
MCFs by Temperature (degrees C)
Cool
<10 11 12
13
14
0.00%
3.00%
17% 19% 20%
22%
25%
0.50%
0.50%
0.50%
0.50%
2.00%
1.50%
1.50%
1.00%
3.00%
17% 19% 20%
10% 11% 13%
17% 19% 20%
66% 68% 70%
22%
14%
22%
71%
25%
15%
25%
73%
Temperate
15 16 17 18 19 20
21
22
23
24
25
0.00%
3.00%
27% 29% 32% 35% 39% 42%
46%
50%
55%
60%
65%
0.50%
0.50%
1.00%
1.00%
4.00%
1.50%
1.50%
1.50%
3.00%
27% 29% 32% 35% 39% 42%
17% 18% 20% 22% 24% 26%
27% 29% 32% 35% 39% 42%
74% 75% 76% 77% 77% 78%
46%
29%
46%
78%
50%
31%
50%
78%
55%
34%
55%
79%
60%
37%
60%
79%
65%
41%
65%
79%
Warm
26 27
0.00%
>28
30.00%
71% 78%
0.50%
80%
0.50%
1.50%
1.50%
5.00%
1.50%
1.50%
2.00%
30.00%
71% 78%
44% 48%
71% 78%
79% 80%
80%
50%
80%
80%
Source: 2006 IPCC Guidelines for National Greenhouse Gas Inventories.
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Table A-4. Collection Efficiencies of Anaerobic Digesters
System Type
Covered anaerobic lagoon
(biogas capture)
Complete mix, fixed film, or plug
flow digester
Cover Type
Bank to bank, impermeable
Modular, impermeable
Enclosed Vessel
Methane Collection Efficiency
0.975
0.70
0.99
Source: EPA 2008, Climate Leaders Greenhouse Gas Inventory Protocol Offset Project Methodology for Managing
Manure with Biogas Recovery Systems
Table A-5. Nitrous Oxide Emission Factors (kg N2O-N/kg Kjdl N)
Waste Management System
Aerobic Treatment (forced aeration)
Aerobic Treatment (natural aeration)
Digester
Uncovered Anaerobic Lagoon
Cattle Deep Bed (active mix)
Cattle Deep Bed (no mix)
Manure Composting (in vessel)
Manure Composting (intensive)
Manure Composting (passive)
Manure Composting (static)
Deep Pit
Dry Lot
Liquid/Slurry
Poultry with bedding
Poultry without bedding
Solid Storage
N2O Emission Factor
0.005
0.01
0
0
0.07
0.01
0.006
0.1
0.01
0.006
0.002
0.02
0.005
0.001
0.001
0.005
Source '.2006IPCC Guidelines for National Greenhouse Gas Inventories.
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