User’s Guide for Estimating Carbon Dioxide Methane and Nitrous Oxide Emissions from Agriculture Using the State Inventory Tool January 2023


User's Guide for Estimating
Carbon Dioxide, Methane, and
Nitrous Oxide Emissions from
Agriculture Using the State
Inventory Tool

January 2023

Prepared by:
ICF

Prepared for:

State Energy and Environment Program,
U.S. Environmental Protection Agency

This section of the User's Guide provides instruction on using the CO2, ChU, and N2O from
Agriculture (Ag) module of the State Inventory Tool (SIT), and describes the methodology
used for estimating greenhouse gas emissions from agriculture at the state level.

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Module 7 - Agriculture Module

January 2023

Table of Contents

1.1	Getting Started	2

1.2	Module Overview	3

1.2.1	Data Requirements	5

1.2.2	Tool Layout	6

1.3	Methodology	6

1.4	Uncertainty	30

1.5	References	30

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module

1.1

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1.1 Getting Started

The Agriculture (Ag) module of the State Inventory Tool (SIT) was first developed using
Microsoft® Excel 2000. While the module will operate with older versions of Excel, it
functions best with Excel 2000 or later. Some of the Excel basics are outlined in the
sections below. Before you use the Ag module, make sure your computer meets the system
requirements. In order to install and run the Ag module, you must have:

• IBM-PC compatible computer with the Windows 95 operating system or later;

• Microsoft® Excel 1997 or later, with calculation set to automatic and macros
enabled;

• Hard drive with at least 20MB free; and

• Monitor display setting of 800 x 600 or greater.

Microsoft Excel Settings

Excel 2003 and Earlier: For the SIT modules to function properly, Excel must be set to
automatic calculation. To check this setting, launch Microsoft Excel before opening the Ag
module. Go to the Tools menu and select "Options..." Click on the "Calculations" tab and
make sure that the radio button next to "Automatic" is selected, and then click on "OK" to
close the window. The security settings (discussed next) can also be adjusted at this time.

Excel 2007 and Later: For the SIT modules to function properly, Excel must be set to
automatic calculation. Go to the Formulas ribbon and select "Calculation Options." Make
sure that the box next to the "Automatic" option is checked from the pop-up menu.

Microsoft Excel Security

Excel 2003 and Earlier: Because the SIT employs macros, you must have Excel security
set to medium (recommended) or low (not recommended). To change this setting, launch
Microsoft Excel before opening the Ag module. Once in Excel, go to the Tools menu, click
on the Macro sub-menu, and then select "Security" (see Figure 1). The Security pop-up box
will appear. Click on the "Security Level" tab and select medium. When set to high, macros
are automatically disabled; when set to medium, Excel will give you the choice to enable
macros; when set to low, macros are always enabled.

When Excel security is set to medium, users are asked upon opening the module whether to
enable macros. Macros must be enabled in order for the Ag module to work. Once they are
enabled, the module will open to the control worksheet. A message box will appear
welcoming the user to the module. Clicking on the "x" in the upper-right-hand corner of the
message box will close it.

Excel 2007 and Later: If Excel's security settings are set at the default level a Security
Warning appears above the formula box in Excel when the Ag module is initially opened.
The Security Warning lets the user know that some active content from the spreadsheet has
been disabled, meaning that Excel has prevented the macros in the spreadsheet from
functioning. Because SIT needs macros in order to function properly, the user must click
the "Options" button in the security message and then select, "Enable this content" in the
pop-up box. Enabling the macro content for the SIT in this way only enables macros
temporarily in Excel but does not change the macro security settings. Once macros are

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module

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enabled, a message box will appear welcoming the user to module. Click on the "x" in the
upper right-hand corner to close the message box.

If the Security Warning does not appear when the module is first opened, it may be
necessary to change the security settings for macros. To change the setting, first exit out
of the Ag module and re-launch Microsoft Excel before opening the Ag module. Next, click
on the Microsoft Excel icon in the top left of the screen. Scroll to the bottom of the menu
and select the "Excel Options" button to the right of the main menu. When the Excel
Options box appears, select "Trust Center" in left hand menu of the box. Next, click the
gray "Trust Center Settings" button. When the Trust Center options box appears, click
"Macro Settings" in the left-hand menu and select "Disable all macros with notification."
Once the security level has been adjusted, open the Stationary Combustion module and
enable macros in the manner described in the preceding paragraph.

Viewing and Printing Data and Results

The Ag module contains some features to allow users to adjust the screen view and the
appearance of the worksheets when they are printed. Once a module has been opened, you
can adjust the zoom by going to the Module Options Menu, and either typing in a zoom
percentage or selecting one from the drop-down menu. In addition, data may not all
appear on a single screen within each worksheet; if not, you may need to scroll up or down
to view additional information.

You may also adjust the print margins of the worksheets to ensure that desired portions of
the Ag module are printed. To do so, go to the File menu, and then select "Print Preview."
Click on "Page Break Preview" and drag the blue lines to the desired positions (see Figure
2). To print this view, go to the File menu, and click "Print." To return to the normal view,
go to the File menu, click "Print Preview," and then click "Normal View."

Figure 1. Changing Security Settings

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Module 7 - Agriculture Module

January 2023

guidelines. The result was a user-friendly and comprehensive set of eleven modules that
help users estimate greenhouse gas emissions at the state level.

Because most state inventories developed today rely heavily on the SIT, User's Guides have
been developed for each of the SIT modules. These User's Guides contain the most up-to-
date methodologies that are, for the most part, consistent with the Inventory of U.S.
Greenhouse Gas Emissions and Sinks (EPA 2022a). Users can refer to the chapters and
annexes of the U.S. Inventory to obtain additional information not found in the SIT or in the
companion User's Guide.

In 2021, EPA began publishing the results of the Inventory of U.S. Greenhouse Gas
Emissions and Sinks disaggregated by U.S. state (EPA 2022b) to make consistent state-
level GHG data available for all states for use by states, researchers, and the general public.
However, EPA recognizes that there will be differences between the state-level estimates
published by EPA and inventory estimates developed by states using the SIT or other tools.
Inventories compiled by states may differ for several reasons, and differences do not
necessarily mean that one set of estimates is more accurate, or "correct." In some cases,
the Inventory of U.S. Greenhous Gas Emissions and Sinks may be using different
methodologies, activity data, and emission factors, or may have access to the latest facility-
level information through the Greenhouse Gas Reporting Program (GHGRP). In other cases,
because of state laws and regulations, states may have adopted accounting decisions that
differ from those adopted by UNFCCC and IPCC to ensure comparability in national reporting
(e.g., use of different category definitions and emission scopes consistent with state laws
and regulations). Users of state GHG data should take care to review and understand
differences in accounting approaches to ensure that any comparisons of estimates are
equivalent or an apples-to-apples comparison of estimates.

The Ag module calculates carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)
emissions from the agricultural sectors shown in Table 1. The Ag module now estimates
CO2 emissions from Liming of Soils and Urea Fertilization for consistency with the Inventory
of U.S. Greenhouse Gas Emissions and Sinks. These categories were previously estimated in
the Land Use, Land-Use Change, and Forestry module.

While the module provides default data for each sector (depending on availability), users
are encouraged to use state-specific data, where available. If using outside data sources, or
for a more thorough understanding of the tool, please refer to the following discussion for
data requirements and methodology.

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module

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1.2.1 Data Requirements

To calculate CO2, CH4, and N2O emissions from agriculture, general animal and crop
production and emission characteristics are required. A complete list of the activity data
and emission factors necessary to run the Ag module is provided in Table 1.

Table 1. Agricultural Sectors, Data Requirements, and Gases Emitted

Module Worksheet

Data Required

Gas(es)

Enteric Fermentation

Emission Factors by Animal Type
Animal Population Numbers

ch4

Manure Management-ChU
Manure Management-IN^O

Typical Animal Mass (TAM)

Volatile Solids (VS) Production
Maximum Potential CH4 Emissions (B0)
Kjeldahl (K) Nitrogen Excreted*

Animal Population Numbers

ch4, n2o

Ag Soils-Plant-Residues & Legumes

Residue Dry Matter Fraction

N20

Ag Soils-Plant-Fertilizers

Fraction Residue Applied

Ag Soils- Animals

Nitrogen Content of Residue
Kjeldahl (K) Nitrogen Excreted
Crop Production
Fertilizer Utilization
TAM*

Rice Cultivation

Seasonal Emission Factor
Area Harvested

ch4

Liming of Soils

Emission factors for CO2 emitted from
use of crushed limestone and dolomite
(ton C/ton limestone)

Total limestone and dolomite applied to
soils (metric tons)

co2

Urea Fertilization

Emission factors for CO2 emitted from
the use of urea as a fertilizer (tons C/ton
urea)

Total urea applied to soils (metric tons)

co2

Ag. Residue Burning-ChU
Ag. Residue Burning-IN^O

Residue/Crop Ratio
Fraction of Residue Burned
Dry Matter Fraction*
Burning Efficiency
Combustion Efficiency
Carbon Content
Nitrogen Content*

cm, n2o

* For consistency in calculations, data that overlaps between sectors are pulled through from the
original input into subsequent uses.

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module

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1.2.2 Tool Layout

Because there are multiple steps to complete within the Ag module, it is important to have
an understanding of the module's overall design. The layout of the Ag module and the
purpose of its worksheets are presented in Figure 3.

Figure 3. Flow of Information in the Ag Module*

Control Worksheet

Individual Sector Worksheets

1. Choose a State

2. to 6. Enter Emission Factors and Activity Data for:

2. Enteric Fermentation

Enteric Fermentation

Enter animal population data for each year

Manure Management

3a. CH4 from Manure Management

Ag Soils

Enter animal population data for each year

Rice Cultivation

3b. N20 from Manure Management

Liming of Soils

Review data imported from Manure CH4 worksheet

Urea Fertilization

4a. Ag Soils-Plant-Residues & Legumes

Ag Residue Burning x

Enter crop production data for each year

4b. Ag Soils-Plant-Fertilizers

Enter fertilizer use by calendar year or growing year

4c. Ag Soils-Animals

Review data imported from Manure CH4 worksheet

5. Rice Cultivation

Enter data harvested for each year

6. Liming of Soils

Enter data on amount of limestone and dolomite applied to soils

7. Urea Fertilization

Enter data on amount of urea applied to soils

8a. Ag. Reside Burning-CH4

Enter crop data and activity data for non-default crops

8b. Ag Residue Burning-N20

Enter nitrogen content for non-default crops

9. View Summary Data ¦*

—Summary Data

Presented in both table and graphical formats in MMTC02E.

10. Export Data ¦*

—*¦ Uncertainty

Review information on uncertainty associated with default data.

* These worksheets are the primary worksheets used in the Ag module; subsequent worksheets are used to
populate the default data and are provided for informational purposes only.

1.3 Methodology

This section provides a guide to using the Ag module of the SIT to estimate CO2, ChU, and
N2O emissions from livestock and crop production. Within the Ag module the sectors
included are enteric fermentation, manure management, agricultural soils, rice cultivation,
liming of soils, urea fertilization, and agricultural residue burning. Because the methodology
differs for each sector, they are discussed separately and specific examples for each sector
are provided.

The Ag module automatically calculates emissions after you enter or choose default data for
the factors on the control worksheet and the activity data within each sector worksheet.
The tool provides default data for most required information; however, other more state-
specific data may be used if available. Additionally, for some states data may not be
available for all crop or livestock types, so users should check each worksheet to determine
if additional information may be available.

The Ag module follows the general methodology outlined in Chapters VII through XI of the
Emissions Inventory Improvement Program (EIIP) guidance, however because of the
automation of the calculations within the tool, the order of steps discussed in this User's

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module

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Guide do not always follow the order of steps discussed within the EIIP guidance document.
This User's Guide provides an overview of the estimation methodology used in the Ag
module by walking through the following steps: (1) select a state; (2) enter emission
factors and activity data for enteric fermentation; (3) enter emission factors and activity
data for manure management; (4) enter emission factors and activity data for agricultural
soils; (5) enter emission factors and activity data for rice cultivation; (6) enter emission
factors and activity data for liming of soils; (7) enter emission factors and activity data for
urea fertilization; (8) enter emission factors and activity data for agricultural residue
burning; (9) review summary information; and (10) export data. The general equations
used to calculate CO2, ChU, and N2O emissions from agriculture are shown in the discussion
of each specific sector.

Step (1) Select a State

To begin, select the state you are interested in evaluating. By selecting a state, the rest of
the tool will automatically reset to reflect the appropriate state default data and
assumptions for use in subsequent steps of the tool.

Step (2) Enter Emission Factors and Activity Data for Enteric Fermentation
Control Worksheet

On the control worksheet, either select the default data provided or enter user-specified,
animal or crop-specific data that will be used throughout the tool. To proceed with the
default data, select the "Check/Uncheck AN" button for each sector or check the individual
default box directly to the right of specific yellow input cells. Note that this number can be
overwritten if you later discover that the data for your state differ from the default data
provided by the tool. To enter user-specified inputs, enter data directly into the yellow
input cells. If the user-specific inputs do not match the default data in the control
worksheet (i.e., the default value is overwritten), the text will appear red. See Figure 4 for
locations of the "Check/Uncheck AN" buttons, individual default check boxes, and yellow
input cells. Information requirements on the control worksheet for each sector are
discussed separately below.

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module

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January 2023

Figure 4. Control Worksheet for the Ag Module

State Inventory Tool - Methane and Nitrous Oxide from Agriculture Module

1. Choose a State. California

This is very important - it selects the correct default variables for your state.

2. Fill In the Variables that are used in this Tool and Click to proceed to the respective worksheets.

Either Type in the Value or Click the Default Box

Reset Worksheet

Enteric Fermentation Emission Factors

Animal Group
Dairy Cattle

Dairy Cows

Dairy Replacement Heifers
Replacements 0-12 mos.
Replacements 12-24 mos.
Beef Cattle
Beef Cows

Beef Replacement Heifers
Replacements 0-12 mos.
Replacements 12-24 mos.
Heifer Stockers
Steer Stockers
Feed lot Heifers
Feed lot Steer
Bulls
Other
Sheep
Goats
Swine

Default Factor

(kq/animal/Yrl Factor Used Use Default? (Check lor Yes)

Manure Management Animal Calculation Values | Consult Guidance |

Animal
Dairy Cattle

Typical Animal Mass (TAM)

(kg)

Use

Default Factor Default?

Volatile Solids (VS)

(kg VS/1000 kg animal mass/day)
Use

Default Factor Default?

Max Pot. Emissions (B^l

(m3 CHj/ kg VS)

Use
Default?

Default Factor

~i \ Control/ Enteric Fermentation ^ CH4 from Manure Management / N20 from Manure Management / Ag Soils-Pbnt-Residues&Legumes

ZL_

_IZ

The first type of required data in the control worksheet is emission factors by animal type
for enteric fermentation. Chk is produced as part of the normal digestive processes of
animals. The amount of ChU produced by domesticated animals depends primarily on the
type of animal (e.g., ruminant or non-ruminant), the age and weight of the animal, and the
quantity and quality of the feed consumed (IPCC 2006). In general, ruminants produce
more ChU than non-ruminants, and higher quality of feed produces lower emissions. The
default emission factors for cattle are dependent on diet characteristics, such as digestible
energy and Chk yield, which vary by diet and individual animal, and are provided on a
regional basis from EPA (2022a). Default emission factors for other livestock types do not
vary by animal production characteristics and are also from EPA (2022a). After completing
the control worksheet for this sector, use the gray arrow to navigate to the sector
worksheet.

Enteric Fermentation Sector Worksheet

The activity data required to populate the orange cells in the enteric fermentation worksheet
are the average animal populations, over the course of the inventory year, for the following
animals: cattle, sheep, goats, swine, and horses. The cattle population is separated into
dairy and beef animals. Dairy animals are further disaggregated into cows and replacement
heifers, while beef animals are disaggregated into bulls, cows, replacement heifers (for
breeding stock), steer and heifer stockers (prior to moving into feedlots), and steer and
heifer feedlot animals. An example of the data requirements used in the enteric
fermentation sector worksheet is presented in Figure 5. Box 1 discusses additional notes if
users plan on providing state-specific animal population data instead of using the default
data.

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Figure 5. Example of Activity Data Applied in the Enteric Fermentation Worksheet

TFT

2. Enteric Fermentation Emissions in California

Click here to find
possible animal
population data
sources.

Emissions from Enteric Fermentation are calculated by multiplying each animal
population by an animal- and region-specific emission factor. Those resulting
values, in kg CHt, are then converted to million metric tons (MMTCHJ, MMT carbon
equivalent (MMTCE), MMT carbon dioxide equivalent (MMTCO^), and then summed
For more information, please refer to the Agriculture Chapter of the User's Guide.

< Return to
Control Sheet

Enteric Fermentation

Number of

Animals
('000 head)

1990

Emission Factoi
(kg CH, Jhead)

W Default Aninal Data?

Emissions
(kg CH,)

Dairg Cattle

Dairy Cows

Dairy Replacement Heifers
Replacements 0-12 mos.
Replacements 12-24 mos
Beef Cattle
Beef Cows

Beef Replacement Heifers
Replacements 0-12 mos.
Replacements 12-24 mos
Heifer Stockers
Steer Stockers
Feedlot Heifers
Feedlot Steer
Bulls
Other
Sheep
Goats
Swine

TOTAL

Check All Boxes

Emissions
(MMTCE)

Emissions
(MMTCOiE)

73.8

70.962.340

56.1

Animal
Populations

^ 62.9

54.2

18,672,435

44.0

3,982,442

44.9

16,678,080

53.0

3,744,079

0.0040

0 0187
0.0040
0.0167
0.0037

0.406
0.048

i j ooo
0.079

0 0002
0.0003

0.0050
0.3135

0.046
0.001

0.002
0.032
1.795

0.117
6.583

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Box 1: Caution When Providing Animal Population Data

If you decide to use animal population data that is different from the default data, please be
aware of the following possible data issues:

Animal populations fluctuate during the year, in some cases by large amounts. For example, a
census done before calving will give a much smaller number than a census done after calving.
Thus, the average animal population over the course of the inventory year should be used in the
estimates (termed here the "annual average population"). For some animals, a specific state's
population may only be given for one month, while the national population is given at other
points during the year. In this case a state's annual average animal population may be
estimated based on the animal population in the state in a given month, and an adjustment
factor developed with (2) the national population of the animal in the same month, and (2) the
national population of the animal either six months before or after. Therefore, to obtain an
average annual animal population it may be necessary to use animal census data from multiple
points throughout each year.

Note that for enteric fermentation the tool gives users the option of providing heifer
replacement data in aggregate or by age class (0 - 12 months and 12 - 24 months); default
populations are provided in aggregate although default emission factors are provided for both
options. If users provide data by age class, it is important to make sure that the total heifer
replacement data are deleted to avoid double counting.

Finally, emissions estimates for enteric fermentation and manure management rely on the same
underlying livestock population data and livestock characteristic data. Therefore, if not using
default data it is important to use the same population data to estimate emissions from these
two source categories. Note that although the specific sub-categories of livestock types may
vary between the two sources, they should rely on the same underlying population data. For
example, total swine populations are used for enteric fermentation, while swine are split into
breeding and market, and further divided by weight class in the manure management source
category. Additionally, calves are omitted in the enteric fermentation estimates; this is because
emissions are assumed to be zero through six months of age. Emissions from calves are
included in the manure management estimates; therefore, the calf populations are required in
that worksheet.

The Ag module calculates emissions for enteric fermentation by multiplying animal
populations by the annual emission factor to obtain the total Chk emitted. Then, the total
CH4 emitted is converted into carbon dioxide (CO2) equivalents by multiplying by the GWP
of CH4 (25). Finally, emissions are divided by 109 to express emissions in MMTCO2E.
Equation 1 demonstrates the emission calculation for enteric fermentation.

Equation 1. Emission Equation for Enteric Fermentation

Emissions (MMTCO2E) =

Animal Population ('000 head) x Emission Factor (kg ChU/head) x 25 (GWP)

-r 1,000,000,000 (kg/MMTC02E)

Once this sector worksheet is complete, use the gray navigational arrow to return to the
control worksheet and proceed to the next sector.

Step (3) Enter Emission Factors and Activity Data for Manure Management

Emissions from animal waste during storage in a management system are accounted for in
this sector. Following storage in a management system it is then assumed that the manure
is ultimately applied to soils, where further emissions take place. These subsequent

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emissions, as well as a third emission type, manure managed through daily spread, are
considered to be emissions from agricultural soils, and are discussed in Step 4.

Control Worksheet

Both CH4 and N2O are produced during the manure decomposition process. The data
required for manure management sector within the control worksheet are the typical animal
mass (TAM), volatile solids (VS) production, and maximum ChU producing capacity (B0),
which are pulled into manure ChU worksheet. Each data requirement is discussed in more
detail below:

• Typical animal mass is the average mass of the entire animal population sub-category,
expressed in kg.

• Volatile solids are defined as the organic fraction of the total solids in manure that will
oxidize and be driven off as gas at a temperature of 1,112°F. Total solids are defined as
the material that remains after evaporation of water at a temperature between 217° and
221°F. CH4 emissions from livestock are directly related to the amount of VS produced.
Production of VS is reported in the tool as kg VS per head per year for cattle (excluding
calves), and as kg VS per 1,000 kg of animal mass per day for calves and all other
livestock (i.e., swine, poultry, sheep, goats, and horses).

• The ChU-producing capacity of livestock manure is generally expressed in terms of the
quantity of ChU that can be produced per kilogram of VS in the manure. This quantity is
determined by animal type and diet and is commonly referred to as Bo with units of
cubic meters of ChU per kilogram VS (m3 ChU/kg VS).

After completing the control worksheet for this sector, use the gray arrows to navigate to
the sector worksheets.

Step (3a) CH4 from Manure Management Sector Worksheet

To estimate ChU emissions from manure, information is input into the blue cells in Figure 6
on annual average animal populations (in number of head) for the following animal types:
cattle (by type), swine (by type), poultry (by type), sheep (by type), goats, and horses.
The red arrows in Figure 6 indicate the areas where the required data are entered or pulled
through to the manure management worksheet from the control worksheet. If users plan
on providing their own animal population data, please review the notes in Box 1. When
decomposition occurs without oxygen (i.e., anaerobic decomposition) ChU is produced. The
CH4-producing capacity of livestock manure depends on the specific composition of the
manure, which in turn depends on the composition and digestibility of the animal diet. In
general, the greater the energy content of the feed, the greater the ChU-producing capacity
of the resulting manure.

The Ag module calculates ChU emissions for manure management by first calculating total
VS produced by the state's livestock. To do so, each animal type population is multiplied by
the VS production rate, provided in kg/head/year for cattle (excluding calves), and kg/1,000
kg animal mass/day for calves and all other livestock (i.e., swine, poultry, sheep, goats, and
horses). For cattle (excluding calves), animal population is multiplied by the VS rate
(kg/head/year) for total VS produced. For calves and all other livestock, animal population
is multiplied by the TAM (kg), VS rate (kg/1,000 kg animal mass/day), and number of days
per year to obtain the total annual VS produced.

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This value is multiplied by B0, and the weighted ChU conversion factor (MCF),1 resulting in
m3 ChU. The total m3 ChU emitted is converted into CO2 equivalents by multiplying by
density of ChU (0.678 kg/m3 ChU) the GWP of ChU (25). Finally, emissions are divided by
109 to express emissions in MMTCO2E. Equation 2 demonstrates the calculation ChU
emissions for manure management.

Equation 2. Emission Equation for ChU Manure Management

VS Producedcattie, excluding calves = Animal Population ('000 head) x 1,000 x VS

(kg/head/yr)

VS Producedcaives and aii other livestock = Animal Population ('000 head) x TAM x
VS (kg/1,000 kg animal mass/day) x 365 (days/yr)

Emissions (MMTCO2E) =

VS Produced (kg) x Bc (m3 CH4/kg VS) x MCF x 0.678 kg/m3 x 25 (GWP)

-r 1,000,000,000 (MMTCO2E)

1 MCF represents the extent to which the B0 is realized for a given livestock manure management
system environmental conditions. The weighted MCF for each animal type is based on default data for
the percent of each animal type's manure handled in manure management systems and the MCF for
each system.

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Figure 6. Example of Activity Data Applied in the Manure Management ChU

Worksheet

| HOME INSERT PAGE LAYOUT FORMULAS DATA REVIEW VIEW DEVELOPER ADD-INS

C D |e f g h I j k l m

3a. CH4 from Manure Management in California

Methane emissions from Manure Management are calculated by multiplying each animal population by the volatile solids (VS) production rate for the total amount of
VS produced. For cattle, total VS produced is calculated by multiplying the animal population by the amount of VS produced per animal head per year. For calves and
other livestock, total VS produced is calculated by multiplying the animal population by the typical animal mass (TAM) and by the amount ofVS produced per kilogram
of animal mass per year. For each animal, this VS total is multiplied by the maximum potential emissions factor and by the methane conversion factor (MCF) of the

ure system by the percentage manure managed in that system. This yields methane emissions in cubic meters which are then converted to MMTCE, MMT carbon
dioxide equivalent (MMTCO2E), and then summed. Note that default emission factors are available through 2015. To facilitate emission calculations for later years, the
tool utilizes 2015 emission factors as proxies for emission factors in subsequent years (2016 through 2020). Emission factors for 2016 and beyond will be updated as
1 as new data become available. For more information, please refer to the Agriculture Chapter of the User's Guide.

\Coi

Check All Boxes

Clear All Data

I"- CH4 from Manure Management

1990

P" Default Animal Data?

Max Pot. ....

lissions (m5 Welghl

:H«J kg VS) MCF

Dairy Cattle

Dairy Cows

Dairy Replacement Heifers
Beef Cattle

Feedlot Heifers
Feedlol Steer
Bulls
Calves
Beef Cows

Beef Replacement Heifers
Steer Stockers
Heifer Stockers

Breeding Swine
Market Under 60 lbs
Market 60-119 lbs
Market 120-179 lbs
Market over 180 lbs
Poultry

Pullets

0.000 =
0.000 =

0.0
0.0

VS Data

0.000 *

n oon .

Maximum Potential
ChU Emissions

LULL
JON
0.000
0.000
0.000
o ouu
nun

LOLL

on::

0.000
0.000
0.000
0.000

U U _ L
L. 'JiL

0.000
0.000
o 000
on in
: n::

0.000
0.000
0 OHO
l::l

0.000 '
0.000 ¦

Step (3b) N2O from Manure Management Sector Worksheet

Once the K-Nitrogen is entered onto the control worksheet under the agricultural soils step
and the animal population data are entered into the manure management ChU worksheet,
no additional data are required to produce emission estimates of N2O from manure
management. Figure 7 shows an example of the worksheet for N2O from manure
management.

Production of N2O during the storage and treatment of animal wastes occurs by combined
nitrification-denitrification of nitrogen contained in ammonia that is present in the wastes.
In order for N2O to be produced, the manure must first be in an aerobic system, in which
the nitrogen in ammonia is converted to nitrites (nitrification). Following this the manure
must go through an anaerobic decomposition period, in which the nitrates are converted to
N2O (denitrification). These types of conditions are most likely to occur in dry manure
management systems that generally have aerobic conditions, but that can undergo periods
of saturation to create the anaerobic conditions necessary for N2O emissions to occur. The
amount of N2O released depends on the system and the duration of waste management.

To estimate N2O emissions from manure management, the Ag module first calculates the
total K-nitrogen excreted by the state's livestock. To do so, each animal type population is
multiplied by the K-nitrogen excretion rate, provided in kg/head/year for cattle (excluding
calves), and kg/1,000 kg animal mass/day for calves and all other livestock (i.e., swine,
poultry, sheep, goats, and horses). For cattle (excluding calves), animal population is
multiplied by the K-nitrogen excretion rate (kg/head/year) for total K-nitrogen excreted. For

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module

1.13

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Module 7 - Agriculture Module

January 2023

calves and all other livestock, animal population is multiplied by the TAM (kg), the K-
nitrogen excretion rate (kg/1,000 kg animal mass/day), and 365 days per year for total K-
nitrogen excreted.

Next the tool separates the total K-nitrogen into the amount in liquid systems (lagoons and
liquid/slurry) and dry systems (drylot and solid storage), and multiplies by the emission
factor specific to these types of systems (0.001 kg N20-N/kg N for liquid systems and 0.2
kg N20-N/kg N for dry systems). Finally, total kg N2O emissions are converted to MMTCO2E
by multiplying by the GWP of N2O (298) and dividing by 109 to convert from kg to
MMTCO2E. Equation 3 demonstrates the calculation N2O emissions for manure
management.

Equation 3. Emission Equation for N2O Manure Management

K-Nitrogen Excretedcattie, excluding calves = Animal Population ('000 head) x 1,000 x

K-Nitrogen (kg/head/day)

K-Nitrogen ExcretedCaives and aii other livestock = Animal Population (*000 head) x TAM
x K-Nitrogen (kg/1,000 kg animal mass/day) x 365 (days/yr)

Emissions (MMTCO2E) =

K-Nitrogen Excreted x Emission Factor (liquid or dry) x
298 (GWP) -r 1,000,000,000 (kg/MMTCQ2E)

Once this sector worksheet is complete, use the gray navigational arrow to return to the
control worksheet and proceed to the next sector.

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module

1.14

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Module 7 - Agriculture Module

January 2023

Figure 7. Example of the Manure Management N2O Worksheet

D I E F G H I I J K L |M N 01 P QI R

3b. N20 from

Manure Management in California

NjD emissions from Manure Management are calculated by multiplying each animal population by the typical animal mass (TAM) by the
amount of Kjejdahl nitrogen produced per kilogram of animal mass per year. This value is then multiplied by a non-volatization factor
and the proportion of waste processed in liquid and solid management systems to give two totals of unvolatized N. Each of these are
multiplied by an emission factor specific to the management system to give two totals of nitrogen emissions. These totals are then
summed and converted to N JD. This amount is then converted to MMTCE, MMT carbon dioxide equivalent (MMTCO^f), and then
summed. For more information, please refer to the Agriculture Chapter of the User's Guide.

Return to
\£ontrol Sheet

E
0
s_
M-

(\l

lure Management 1990

Dairg Cattle

~airy Cows

Dairy Replacement Heifers
Beef Cattle
Feedlot Heifers
Feedlot Steer
Swine

Breeding Swine
Market Under 60 lbs
Market 60-119 lbs
Market 120-179 lbs
Market over 180 lbs
Poultrj
Layers
Hens > 1 yr
Pullets
Chickens
Broilers
Turkeys
Other

Sheep on Feed
Sheep Not on Feed

Number of

Animals
( 000 head)

Unirolatilized N

from Manure in Unvolatilized N Emissions from Emissions from
Anaerobic from Manure in Anaerobic Solid Storage.

Lagoons and Solid Storage. Lagoons and Drglot. & Other Total NiO
Total K-Nitrogen Liquid Sgstems Drglot 6 Other Liquid Sgstems Sgstems Emissions Emission
Eicreted (kg) (kg) Sgstems (kg) (kg N,O N) (kg N,O N) (kgN,Q) (MTCE)

1,114.2

108,077,746

83,013,490

10,327,983

83,013

206,560

455,044

38,47

520.6

28,036,834

24,214,045

484,281

761,013

64,34

Animal Population Data

90.4

4,159,014

83,180

130,712

11,0!

371.4^

I/.UHI.W4

iiw

17,081,974

341,639

536.862

45,38

475,537

—

Jlnfl ,KQ

1R07i

400

317

1,128

60.0

208,663

K-Nitrogen and TAM
are applied here

176

139

495

49.0

304,975

257

204

723

31.0

JJ22.30J,

271

215

764

27.0

12,537

316

251

891

30.400.0

16,577,424

1,657,742

14,919,682

1,658

186,496

295,670

24,99

5.290.0

2,154,829

215,483

1,939,346

215

24,242

38,433

3,24

210.0

114.515

11,452

103,064

1,288

2,042

42,018.2

15,183,270

303,665

477,188

40,34

13,125.0

24,106,425

482,129

757,631

64,05

225.0

931,298

16,339

327

513

775.0

3,207,803

N i ~ ~! \ fnntrnl / Fntfirir Ffirmpntfltinn I TH4 frnm Mani jrp Mamnpmpnf \ N7fl frnm Manum MamnRmmt / An Rnik-Plant-Rpsirii jps&I pnumRS l<

Step (4) Enter Emission Factors and Activity Data for Agricultural Soils

Emissions from agricultural soils are divided into three worksheets in the SIT, 1) residues,
legumes, and histosols; 2) fertilizers; and 3) animals. In addition, emissions can be either
direct through cropping and animal management practices or indirect through either
volatilization into the atmosphere as NOx and NH3 or from agricultural leaching and runoff.
Both direct and indirect emissions are estimated in the worksheets described below.

Control Worksheet

N2O is produced naturally in soils through the microbial processes of denitrification and
nitrification.2 A number of anthropogenic activities add nitrogen to soils, thereby increasing
the amount of nitrogen available for nitrification and denitrification, and ultimately the
amount of N2O emitted. These activities include application of fertilizers, animal production,
cultivation of nitrogen-fixing crops, incorporation of crop residues, and cultivation of
histosols (highly organic soils). The sources of N2O described here are divided into three
categories: (1) direct emissions from agricultural soils due to cropping practices; (2) direct
and indirect emissions from soils from fertilizer application; and (3) direct and indirect
emissions from agricultural soils due to animal production. Each of these is discussed in

2 Denitrification, the process by which nitrates or nitrites are reduced by bacteria, results in the
release of nitrogen into the air. Nitrification is the process by which bacteria and other
microorganisms oxidize ammonium salts to nitrites, and further oxidize nitrites to nitrates.

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module

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Module 7 - Agriculture Module

January 2023

more detail in Step 4. Within the control worksheet data must be entered by crop type for
residue dry matter fraction, fraction residue applied, and nitrogen (N) content of residue.
Crop types utilized include alfalfa, corn for grain, all wheat, barley, sorghum, oats, rye,
millet, rice, soybeans, peanuts, dry edible beans, dry edible peas, austrian winter peas,
lentils, and wrinkled seed peas. Additionally, K-nitrogen is entered by animal type for dairy
and beef cattle (by type), swine (by type), poultry (by type), sheep, goats, and horses.

Data on the residue dry matter fraction, fraction residue applied, and N content of residue
are pulled into the agricultural soils emissions from residues, legumes, and histosols
worksheet. K-nitrogen is pulled into the agricultural soils-animals worksheet along with
animal population data and TAM from the manure management sector. After completing
the control worksheet for this sector, use the gray arrows to navigate to the sector
worksheets.

Step (4a) N2O from Agricultural Soils Sector Worksheet - Residues,
Legumes, and Histosols

This worksheet covers N2O emitted from agricultural soils due to biological nitrogen fixation
by certain crops, crop residues remaining on agricultural fields, and histosol cultivation.
Figure 8 presents an example of the data, as used in the calculations on this worksheet.

Figure 8. Example of Activity Data Applied in the Agricultural Soils Residues and

N2O is emitted from the cultivation of N-fixing crops, also known as legumes. To estimate
state emissions of N2O from N-fixing crops, data on the amount of beans (by type), pulses
(by type), and alfalfa produced in the state is input into the dark green cells in Figure 8. In
addition, data on production of non-alfalfa forage crops, such as red clover, white clover,

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module

1.16

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Module 7 - Agriculture Module

January 2023

birdsfoot trefoil, arrowleaf clover, and crimson clover are desirable. In order to calculate
the total N input from N-fixing crops, the SIT multiplies the production of each type of N
fixing crop by the residue to crop mass ratio for each crop, the residue dry matter fraction,
and the nitrogen content in each crop. For forage crops total N input is simply calculated as
the production of N-fixing forage crops multiplied by the nitrogen content of the crop. The
total N input for all N-fixing crops is multiplied by the emission factor for direct emissions of
N2O (1.0 percent) to obtain the amount of emissions in N20-N/yr. The result is converted
from kg N2O-N to MMTCO2E by multiplying the emissions from crop residues by 44/28 (the
molecular weight ratio of N2O/N2O-N) and by the GWP of N2O (298) and dividing by 106 to
convert from metric tons to MMTCO2E. Equation 4 shows emission calculations from N-
fixing crops.

Equation 4. Emission Equation for N-fixing Crops

Emissions (MMTCO2E) =

Crop Production (MT) x Mass ratio (residue/crop) x Dry Matter Fraction x N content
x Emission Factor (1.0%) x 44/28 (Ratio of N20 to N20-N) x 298 (GWP)

-r 1,000,000 (MT/MMTCO2E)

N2O is also emitted from crop residue that is incorporated into the soil (i.e., the portion of
the crop that has been neither removed from the field as crop nor burned). To estimate the
total N in crop residues returned to the soil for each crop, the SIT multiplies the production
of each crop by the crop residue to crop mass ratio, the dry matter fraction for residue, the
fraction of residue applied (accounting for removal of crop and the fraction burned), and the
N content of the residue. Next, the total N in all crop residues is multiplied by the emission
factor for direct emissions of N2O (1.0 percent) to obtain the amount of emissions in N2O-
N/yr. The result is converted from kg N2O-N to MMTCO2E by multiplying the amount of
emissions from crop residues by 44/28 (the molecular weight ratio of N2O/N2O-N) and by
the GWP of N2O (298) and dividing by 109 to convert from kg to MMTCO2E. Equation 5
shows emission calculations from N-fixing crops.

Equation 5. Emission Equation for Residues

Emissions (MMTCO2E) =

Crop Production (MT) x Mass ratio (residue/crop) x Dry Matter Fraction x Fraction
Residue Applied x N content x Emission Factor (1.0%) x 44/28 (Ratio of N2O to N20-N)
x 298 (GWP) -r 1,000,000,000 (kg/MMTC02E)

N2O is also emitted from the cultivation of high organic content soils, or histosols. To
estimate state emissions of N2O from the cultivation of histosols, the SIT requires data on
histosol cultivation acreage by temperate and sub-tropical climate types. To calculate the
direct emissions from histosols, the acreage of cultivated soils is converted into hectares
and multiplied by the appropriate emission factor for the climate type (8 for temperate or
12 for sub-tropical) in kg N2O-N per hectare per year. The result is converted from kg N2O-
N to MMTCO2E by multiplying the emissions by 44/28 (the molecular weight ratio of
N2O/N2O-N) and by the GWP of N2O (298) and dividing by 109 to convert from kg to
MMTCO2E. Equation 6 shows emission calculations from N-fixing crops.

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module

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Module 7 - Agriculture Module

January 2023

Equation 6. Emission Equation for Histosols

Emissions (MMTCO2E) =

Area Cultivated (acres) x 1/2.471 (ha/ac) x Emission Factor (kg N20-N/ha/yr)
x 44/28 (Ratio of N20 to N2Q-N) x 298 (GWP) -r 1,000,000,000 (kg/MMTC02E)

Step (4b) N2O from Agricultural Soils Sector Worksheet - Fertilizers

This worksheet estimates both direct and indirect emissions from agricultural soils due to
synthetic fertilizer use and organic fertilizer use, including dried blood, compost, tankage,
and land application of sewage sludge3, as shown in Figure 9.

Figure 9. Example of Required Data in the Agricultural Soils Fertilizers Worksheet

0 P Q R S

4b. Ag Soils Plant Fertilizer Emissions in California

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Module 7 - Agriculture Module

January 2023

Emission calculations begin by multiplying total non-manure organic fertilizer use by the
percent of N in organic fertilizer to calculate total N present. Next volatilized and
unvolatilized N are disaggregated to separate calculations for direct emissions from fertilizer
application and indirect emissions through volatilization as ammonia (Nhh) and nitrogen
oxides (NOx). The fraction of volatilized N is assumed to be 10 percent of synthetic fertilizer
and 20 percent of organic fertilizer. Thus, direct emissions are calculated by multiplying
total N by 0.9 for synthetic fertilizer and 0.8 for organic fertilizer to obtain the amount of
unvolatilized N. This value is multiplied by the emission factor for direct emissions of N2O
(1.0 percent) to obtain the amount of emissions in INhO-N/yr and converted from kg N2O-N
to kg N2O by multiplying by the ratio of N2O/N2O-N (44/28). Indirect emissions are
calculated by multiplying the total fertilizer N that volatilizes by the volatilization emission
factor (0.001 kg INhO-N/kg N) and converting from kg N2O-N to kg N2O by multiplying by the
ratio of N2O/N2O-N (44/28). Note that indirect emissions from leaching are accounted for in
the agricultural soils-animals worksheet, which is discussed below in Step 3c.

Finally, both direct and indirect emissions are converted from kg N2O to MMTCO2E by
multiplying by the GWP of N2O (298) and dividing by 109 to convert from kg to MMTCO2E.
Equation 7 demonstrates the calculation for direct emissions and indirect emissions are
shown in Equation 8.

Equation 7. Emission Equation for Direct N2O Emissions from Agricultural Soils

Emissions (MMTCO2E) =

Total N x fraction unvolatilized (0.9 synthetic or 0.8 organic)
x O.Ol (kg N20-N/kg N) x 44/28 (Ratio of N20 to N20-N) x 298 (GWP)
-r 1,000,000,000 (kg/MMTCQ2E)

Equation 8. Emission Equation for Indirect N2O Emissions from Agricultura

Emissions (MMTCO2E) =

Total N x fraction volatilized (0.1 synthetic or 0.2 organic)
0.001 (kg N20-N/kg N) x 44/28 (Ratio of N20 to N20-N) x 298 (GWP)
-r 1,000,000,000 (kg/MMTCQ2E)

Soils

Step (4c) N2O from Agricultural Soils Sector Worksheet - Animals

To calculate N2O emissions for this worksheet, no additional data are required. Figure 10
shows an example of the agricultural soils-animals worksheet. Nitrogen flux from animal
production is dependent on the waste management system employed (if any) and the
amount of waste excreted. The methodology presented in this section does not account for
site-specific conditions that could affect either the amount of nitrogen excreted or the
resulting emission factor for N2O emissions. These conditions could include temperature,
humidity, and others. Estimates include direct emissions from application of animal waste
through daily spread operations, eventual application of managed animal wastes, and
animal wastes that are deposited directly on soils by animals in pastures, ranges, and
paddocks. In addition, indirect emissions from volatilization, leaching, and run-off are also
estimated. This method reflects the assumption that all manure is eventually applied to
agricultural soils as a mode of disposal.

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module 1.19

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Module 7 - Agriculture Module

January 2023

Figure 10. Example of the Agricultural Soils Animals Worksheet

G H I J K L Ml N 0 P | Q | R

4c Agriculture Soils- Animal Emissions in California

Emissions from Animals are calculated by multiplying each animal population by the typical animal mass (TAM) by the amount of K-Nitrogen (K-N) produced per kilogram
of animal mass per year for total K-N excreted. Indirect emissions are estimated by multiplying K-N by a volatization rate and EF to give emissions of N. Direct
emissions from pasture, range, and paddock are calculated by multiplying K-N by the percent of manure in pastures and an EF for that system. Direct emissions from
manure applied to soils are calculated by multiplying K-N for daily spread and managed systems by the percent of manure in these systems and an EF for each
system, excluding a small percent of managed manure used as feed. These totals are then summed and converted to NJD. Unvolatized N from fertilizers, calculated
on the previous worksheet, and K-N from manure are multiplied by a leaching EF to give emissions from leaching and runoff. The emissions summary for each year
converts the total direct and indirect estimates for livestock and runoffJleaching to MTNjD, MMTCE, and then MMT carbon dioxide equivalent (MMTCO^). For more
information, please refer to the Agriculture Chapter of the User's Guide.

Agriculture Soils - Emissions from Animals & Runoff

1990

K-NITROGEN EXCRETED BY MANAGEMENT SYSTEM (kg)

Number of Indirect Animal

Animals Total K-Nitrogen N,0 Emissions

('000 head) Excreted (kg) (metric tons N)

Unmanaged

Pasture. Range,
and Paddock

Dairy Replacement Heifersj[
Beef Cattle
Feedlot
Feedlot Steer
Bulls
Calves
Beef Cows
Steer Stockers
T otal Beef
Swine

Breeding Swine
Market Under 60 lbs
Market 60-119 lbs
Market 120-179 lbs
Market over 180 lbs
Poultrj

K-Nitrogen and TAM
are applied here

Return to
Control Sheet

DIRECT EMISSIONS (MT N)

Unmanaged Manure

Sjstems - Applied to

Dail) Spread Soils

~I / N?f) frnm Manure MananRmRnt /

16,577.424 | \ 33 | [

An Snik-Plant-RRsiriuRsftl Rnumips

16.577.4271 I . .

/ An Snik-Plant-FRr1-ili7Rr<; \ An Bnils-Animals / RirR fultivatinn / I

n r

~i r

The SIT calculates emissions by multiplying each animal population (entered in the manure
management worksheet) by the rate of N excreted by animal type, provided in
kg/head/year for cattle (excluding calves), and kg/1,000 kg animal mass/day for calves and
all other livestock (i.e., swine, poultry, sheep, goats, and horses). For cattle (excluding
calves), animal population is multiplied by the K-nitrogen excretion rate (kg/head/year) for
total K-nitrogen excreted. For calves and all other livestock, animal population is multiplied
by the TAM (kg), the K-nitrogen excretion rate (kg/1,000 kg animal mass/day), and 365
days per year for total K-nitrogen excreted. Next, the total K-nitrogen is disaggregated into
manure handled in managed systems, manure applied as daily spread, and manure
deposited directly into pastures, ranges, or paddocks, based on default percentages
obtained from the U.S. Inventory (EPA 2022a).

Direct emissions from manure handled in management systems and applied as daily spread
is multiplied by the volatilization factor (0.8) to obtain the total unvolatilized N.

Additionally, for poultry an adjustment must be made for the small portion of waste used as
animal feed. For all poultry categories (i.e., layers (hens, pullets, and chickens), broilers,
and turkeys), the total K-nitrogen in managed systems is multiplied by 0.958, as it is
assumed that 4.2 percent of all poultry manure is used as animal feed and not applied to
agricultural soils (Carpenter 1992). The total unvolatilized N is multiplied by the emission
factor for direct emissions of N2O (1.0 percent) to obtain the amount of emissions in N2O-
N/yr.

For animal waste deposited directly onto pasture, range, and paddock the total K-nitrogen is
multiplied by the percent of manure deposited on pasture, range, and paddocks and the
IPCC default emission factor for direct emissions (0.02 kg INhO-N/kg N excreted) (IPCC
1997, EPA 2022a) to obtain the amount of emissions in INhO-N/yr.

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module

1.20

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Module 7 - Agriculture Module

January 2023

Indirect emissions from volatilization to Nhh and NOx are estimated as 20 percent of the
total K-nitrogen excreted per year multiplied by the emission factor of 0.001 kg INhO-N/kg N,
following the methodology of organic fertilizers, shown in Equation 8.

Indirect emissions from leaching and runoff are assumed to occur from 30 percent of the
total unvolatilized N. Therefore, indirect emissions from leaching and runoff are calculated
by multiplying the total unvolatilized N by 0.30 and the emission factor (0.0075 kg N2O-
N/kg N). The result is converted to MMTCO2E using the methodology described below.

Finally, both direct and indirect emissions are converted from kg N2O-N to MMTCO2E by
multiplying emissions by the molecular weight ratio of N2O/N2O-N (44/28) and by the GWP
of N2O (298) and dividing by 109 to convert from kg to MMTCO2E. Equation 7 shows the
general equation for the calculation for direct emissions (adjustment for poultry is not
shown) and indirect emissions are shown in Equation 8. Once this sector worksheet is
complete, use the gray navigational arrow to return to the control worksheet and proceed to
the next sector.

Step (5) Enter Emission Factors and Activity Data for Rice Cultivation

Control Worksheet

For the rice cultivation sector, seasonal emission factors are required in the control
worksheet. Mean seasonal emission factors are used to calculate ChU emissions from the
primary and ratoon4 crops. Rice fields for the ratoon crop typically remain flooded for a
shorter period of time than for the first crop. Studies indicate, however, that the ChU
emission rate of the ratoon crop may be significantly higher than that of the primary crop.
The rice straw produced during the first harvest has been shown to dramatically increase
ChU emissions during the ratoon cropping season (Lindau & Bollich, 1993). The higher
emission rate of the ratoon crop supports the use of separate emission factors for the
primary and ratoon rice crops. Seasonal emission factors for rice cultivation are pulled into
the sector worksheet. After completing the control worksheet for this sector, use the gray
arrow to navigate to the sector worksheet.

Rice Cultivation Sector Worksheet

The rice cultivation worksheet in the Ag Module requires data input in the purple cells on the
total acreage of rice grown during both the primary and the ratoon growing seasons.

Figure 11 demonstrates where the acreage data and emission factors are used in the rice
cultivation worksheet.

4 A ratoon rice crop is a second crop of rice grown from the stubble after harvest of the primary crop.
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Module 7 - Agriculture Module

January 2023

Figure 11. Example of Activity Data Applied in the Rice Cultivation Worksheet

5 Rice Cultivation in California

Emissions from Rice Cultivation are calculated by multiplying the area harvested for the primary and
ratoon crops by a seasonal emission factor. Those resulting values, in kg CH„ are then converted to
million metric tons (MMTCHJ, MMT carbon equivalent (MMTCE), MMT carbon dioxide equivalent
(MMTCOjE), and then summed. Rice is cultivated in seven states: Arkansas, California, Florida,
Louisiana, Mississippi, Missouri, and Texas. The default data for all other states is zero for each year.
For more information, please refer to the Agriculture Chapter of the User's Guide.

-------
Module 7 - Agriculture Module

January 2023

Once this sector worksheet is complete, use the gray navigational arrow to return to the
control worksheet and proceed to the next sector.

Step (6) Enter Emission Factors and Activity Data for Liming of Soils
Control Worksheet

The data entered in the control worksheet for this sector are emission factors for limestone
and dolomite used in liming of soils. These emission factors should be in metric tons of
carbon per metric ton of limestone (or dolomite). The default values are based on West &
McBride (2005); if emission factors other than module defaults are available for limestone
and dolomite, you should document their source carefully. If the user-specific inputs do not
match the default data in the control worksheet (i.e., the default value is overwritten), the
text will appear red.

Limestone (CaCCb) and dolomite (CaMg(CC>3)2) are added to soils by land managers to
remedy acidification. When these compounds come in contact with acidic soils, they
degrade, thereby generating CO2. This section presents the methodology for calculating the
CO2 emissions from the application of limestone and dolomite to soils.

After entering the appropriate emission factors, use the gray arrows to navigate to the
Liming of Soils worksheet.

Liming of Soils Worksheet

Within the Liming of Soils worksheet, enter the total limestone and dolomite applied to soil
in the light blue cells, in thousands of metric tons. An example of this worksheet is shown
in Figure 12. Equation 10 shows the method used to calculate CO2 emissions from liming of
soils.

Default data are provided for most states if you wish to use them; however, states are
encouraged to use more detailed data if it is available and well documented. The default
data are from the United States Geological Survey (USGS 2022). Once this worksheet is
complete, use the gray navigational arrow to return to the control worksheet and proceed to
the next source category.

Equation 10. Emission Equation for Liming of Soils

Emissions (MMTCO2E) =

Total Limestone or Dolomite Applied to Soil (1,000 metric tons) x Emission Factor (tons
C/ton limestone or dolomite) x 44/12 (ratio of CO2 to C) -r 1,000,000 (to yield

MMTCO2E)

State Greenhouse Gas Inventory Tool User's Guide for the Ag Module 1.23

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Module 7 - Agriculture Module

January 2023

Figure 12. Example of Data Applied in the Liming of Soils Worksheet

A B C D E

6. Liming of Soils in California

Return to
Control Sheet

Emissions from Liming of Soils are calculated by summing carbon emissions from the application of both
limestone and dolomite to soil. The masses of limestone and dolomite are multiplied by their carbon emission
factors, converted to million metric tons carbon dioxide equivalent, and then summed. For more information
please consult the Land Use, Land-Use Change, and Forestry chapter of the User's Guide.

Required Consumption Data

Year

Total Applied to Soil
('000 Metric Tons)

1990

Limestone^rtl

Dolomite

1991

Limestone

Dolomite

1992

Limestone

Dolomite

1993

Limestone

Dolomite

1994

Limestone

Dolomite

1995

Limestone

Dolomite

1996

Limestone

Dolomite

1997

Limestone

Dolomite

1998

Limestone

Dolomite

1999

Limestone

Dolomite

2000

Limestone

Dolomite

Total Carbon
Dioxide Emissions

Liming Emission
Factors (from Control)

Default Activity Data?
Default Activity Data?
Default Activity Data?
Default Activity Data?
Default Activity Data?
Default Activity Data?
Default Activity Data?
Default Activity Data?
Default Activity Data?
Default Activity Data?

Step (7) Enter Emission Factors and Activity Data for Urea Fertilization
Control Worksheet

The data entered in the control worksheet for this sector is an emission factor for urea
application as a fertilizer to soils. The emission factor should be in metric tons of carbon per
metric ton of urea. The default emission factor is based on IPCC (2006); if emission factors
other than module defaults are available for urea fertilization, you should document their
source carefully. If the user-specific inputs do not match the default data in the control
worksheet (i.e., the default value is overwritten), the text will appear red.

Urea is used as a fertilizer that results in CO2 emissions that were fixed during the industrial
production process. According to U.S. EPA (2022a), urea in the presence of water and
urease enzymes is converted into ammonium (NH4"1"), hydroxyl ion (OH ), and bicarbonate
(HCO3 ). The bicarbonate then evolves into CO2 and water. This section presents the
methodology for calculating the CO2 emissions from the application of urea to soils.

After entering the appropriate emission factors, use the gray arrows to navigate to the Urea
Fertilization worksheet.

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Urea Fertilization Worksheet

Within the Urea Fertilization worksheet, enter the total urea applied to soil in the orange
cells, in metric tons. An example of this worksheet is shown in Figure 13. Equation 11
shows the method used to calculate CO2 emissions from the application of urea to soils.

Default data are provided for most states if you wish to use them; however, states are
encouraged to use more detailed data if it is available and well documented. The default
data on the amount of fertilizer applied were derived from state-level fertilizer sales data
provided in TVA (1991 through 1994) and AAPFCO (2021). Once this worksheet is
complete, use the gray navigational arrow to return to the control worksheet and proceed to
the next source category.

Equation 11. Emission Equation for Urea Fertilization

Emissions (MMTCO2E) =

Total Urea Applied to Soil (metric tons) x Emission Factor (tons C/ton urea) x 44/12
(ratio of C02 to C) -r 1,000,000 (to yield MMTCO2E)

Figure 13. Example of Data Applied in the Urea Fertilization Worksheet

A 1 B I C | D | E | F G

. C02 from Urea Fertilization in California

< Return to
Control Sheet

15
16]
17
18]

The use of urea as a fertilizer results in C02 emissions that were previously fixed during the industrial production process.
The amount of urea applied to soil is multiplied by the carbon emission factor, and then converted to million metric tons
carbon dioxide equivalent. For more information please consult the Land Use, Land-Use Change, and Forestry chapter of
the User's Guide.

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

Urea Emission Factors
(from Control)

I- Defau
\~ Defau
\~ Defau
\~ Defau
\~ Defau
Defau
I- Defau
I- Defau
I- Defau
|~ Defau
I- Defau
I Defau

I Default Activity Data?

t Activity Data?
t Activity Data?
t Activity Data?
t Activity Data?
t Activity Data?
t Activity Data?
t Activity Data?
t Activity Data?
t Activity Data?
t Activity Data?
t Activity Data?
t Activity Data?

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Step (8) Enter Emission Factors and Activity Data for Agricultural Residue
Burning

Control Worksheet

Agricultural production results in large quantities of crop wastes. In some parts of the
United States, these residues are burned in the field to clear remaining straw and stubble
after harvest, and to prepare the field for the next cropping cycle. This process releases
CO2, CH4, and N2O. In accordance with international greenhouse gas (GHG) accounting
guidelines, the Ag module does not include CO2 emissions from crop residue burning. This
is because the carbon released as carbon dioxide during burning had been taken up from
carbon dioxide in the atmosphere during the growing season, thus resulting in no net
emissions. This sector addresses emissions from burning residues of seven crops for which
burning of crop wastes is significant in the United States—barley, corn, peanuts, rice,
soybeans, sugarcane, and wheat. The data for agricultural residue burning is required by
crop type in the control worksheet and includes:

• residue to crop ratio;

• fraction of residue burned, defined as the proportion of the total crop produced in fields
where residue is burned;

• burning efficiency, defined as the fraction of dry biomass exposed to burning that
actually burns;

• combustion efficiency, defined as the fraction of carbon in the fire that is released to the
atmosphere; and

• carbon (C) content of the crops.

In addition, the dry matter fraction and the N content data from the agricultural soils sector
are used for all crops except sugarcane, which is required here, if applicable. These data
are pulled into the ChU and N2O agricultural residue burning worksheets. After completing
the control worksheet for this sector, use the gray arrows to navigate to the sector
worksheets.

Agricultural Residue Burning Sector Worksheets

The information needed to estimate GHG emissions from burning of agricultural wastes is
the annual production of barley, corn, peanuts, rice, soybeans, sugarcane, and wheat. In
addition, the user has the option of entering the required data in the orange input cells for
up to two additional unspecified crops per year. The SIT provides a conversion to metric
tons from pounds of peanuts, hundred count of rice, tons of sugarcane, and bushels of
barley, corn, soybeans, and wheat. The red arrows in Figure 14 and Figure 15 demonstrate
the use of activity data to calculate agricultural residue burning emissions from ChU and
N2O, respectively.

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Figure 14. Example of Activity Data Applied in the Agricultural Residue Burning

CH4 Worksheet

A C D E F G H

8a. Ag Residue Burning CH4 Emissions in Kentucky

Emissions from Agricultural Residue Burning are calculated by multiplying the amount of crop produced by a series of factors to calculate the amount of crop
residue produced and burned, the resultant dry matter, and the carbon/nitrogen content of this dry matter. From these, the amount of carbon and nitrogen
released can be determined, and thus methane and nitrous oxide emissions quantified. Those resulting values, in metric tons of gas, are converted to million
metric tons carbon equivalent (MMTCE), then to million metric tons carbon dioxide equivalent MMTC02E, and then summed. Note that default emission factors
are available through 2016. To facilitate emission calculations for later years, the tool utilizes 2016 emission factors as proxies for emission factors in
subsequent years (2017 through 2020). Emission factors for 2017 and beyond will be updated as soon as new data become available. For more information,
please refer to the Agriculture Chapter of the User's Guide.

CH4 from Agricultural Residue Burning

Burning Efficiency Combustion Efficiency Carbon Content

5 1

6 I

14
15]
16

Crop Production
(metric tow)

BurnirgV
Efficiency

Combustion
Efficiency

Total C Released
(metric ton3 C)

Sarley
Corn
Peanuts
Rice

Soybeans
Sugarcane
Wheat
Other

Crop Production Residue/crop Ratio Fraction Residue Burned Dry Matter Fraction

0.93

>^
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Module 7 - Agriculture Module

January 2023

N emission ratio (0.007) and converted to full molecular weight of N2O by multiplying by
(44/28), the mass ratio of N2O to N.

Finally, for both ChU and N2O emissions, the results are converted to MMTCO2E by
multiplying by the GWP of ChU (25) or N2O (298) and dividing by 106 to convert from metric
tons to million metric tons, as shown in Equation 12.

Equation 12. General Emission Equation for Agricultural Residue Burning

Emissions ((MMTCO2E) =

Crop Production (metric tons) x Residue/Crop Ratio x Fraction Residue
Burned Dry Matter Fraction x Burning Efficiency x Combustion Efficiency
x C or N Content x Emission Ratio (CH4-C or N2O-N) x Mass Ratio (CH4/C or
N2O/N) X GWP -r 1,000,000 (MT/(MMTC02E)

Once this sector worksheet is complete, use the gray navigational arrow to return to the
control worksheet and proceed to the next sector.

Step (9) Review Summary Information

The steps above provide estimates of total CO2, ChU, and N2O emissions from each
agricultural sector. Total emissions are equal to sum of emissions from each livestock or
crop type, for each year. The information is collected by sector on the summary
worksheets. There are two summary worksheets in the Ag module, one that displays
results in both MMTCO2E and MMTCE, and a second that displays the results in graphical
format. Additionally, the summary worksheet provides an overview of sources excluded
from the current emission estimates. Users should check this list to see if they wish to go
back and enter data for any of the omitted crop or livestock types. Figure 16 shows the
summary worksheet that sums the emissions from all sectors in the Ag module. In the
summary worksheet, users can choose to apply the "National Adjustment Factor," which
helps reconcile differences between the methodologies for estimating N2O emissions from
agricultural soils of the National Inventory of Greenhouse Gas Emissions and the SIT.
Specifically, the method used in the SIT underestimates indirect emissions from fertilizers
while overestimating indirect emissions from livestock and all direct sources of agricultural
soils emissions, relative to the National Inventory. Using the adjustment factor will only
affect estimates of agricultural soils.

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Figure 16. Example of the Emissions Summary Worksheet in the Ag Module

9. California Emissions Summary

Return to
Control Sheet

So to the
Summary Figures

Review discussion of uncertainty
associated with these results

This Worksheet Provides a Summary of Agriculture Emissions for CA Once All Prior Worksheets Have Been Completed.
Note: Totals below do not account for emissions from the following animals, fertilizers, crops, or harvested areas:

Enteric Fermentation:

Manure Management
and Ag Soils-Animal:

Ag Soils-Plant -Residues, Legumes, Red Clover. White Clover, Birdsfoot Trefoil, Arrowleaf Clover, Crimson Clover,
Histosols:

Ag 5o\\s-P\ar\t-Fertilizers:
Rice Cultivation:
Ag Residue Burning:

Liming and Urea:

Adjustment Factor

HrneTie: ana

Dolomite, Urea Fertilizi

post. Dried Manure, Activated Sewage Sludge, Other Sewage Sludge, Tankage

The "National Adjustment Factor"j»opplied to reconcile differences betwaen the methodologies for estimating nitrous oxide emissions from agricultural soils of the National
Inventory of Greenhouse Gte Emissions and the State Inventory Tool. The memoc^ised in the SIT underestimates indirect emissions from fertilizers and overestimates indirect
emissions from livestock ar^j^lirect sources of agricultural soils emissions rqjgraw to the National Inventory. Other sources will not be affected.

O Apply National Adjustment Factor

® Do Not Apply National Adjustment Factor

Emissions (MMTCE)

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

Enteric Fermentation

2.485

2.399

2.425

2.453

2.548

2.577

2.576

2.647

2.635

4.703

4.798

4.878

Manure Management

1.768

1.804

1.834

1.839

1.948

2.040

2.055

2.182

2.105

4.415

4.562

4.908

Ag Soils

1.915

2.318

2.296

2.341

2.420

2.499

2.572

2.470

2.379

3.283

3.385

3.472

Rice Cultivation

0.258

0.233

0.258

0.286

0.317

0.304

0.327

0.338

0.300

0.330

0.359

0.308

Liming

Urea Fertilization

Agricultural Residue Burning

0.011

0.009

0.011

0.012

0.010

0.012

0.010

0.011

0.010

TOTAL

6.438

6.763

6.823

6.930

7.246

7.430

7.542

7.648

7.428

12.742

13.114

13.576

Step (10) Export Data

The final step is to export the summary data. Exporting data allows the estimates from
each module to be combined later by the Synthesis Module to produce a comprehensive
GHG inventory for the state.

To access the "Export Data" button, return to the control worksheet and scroll down to step
10. Click on the "Export Data" button and a message box will open that reminds the user to
make sure all sections of the module have been completed. If you make any changes to the
Ag module later, you will then need to re-export the results.

Clicking "OK" prompts you to save the file.
The file is already named, so you only need
to choose a convenient place to save the
file. After the file is saved, a message box
will appear indicating that the data was
successfully exported.

While completing the modules, you are
encouraged to save each completed
module; doing so will enable you to easily
make changes without re-running it entirely.

Note: the resulting export file should not be
modified. The export file contains a summary
worksheet that allows users to view the results, as well as
a separate data worksheet with an unformatted version of
the results. The second worksheet, the data worksheet,
contains the information that is exported to the Synthesis
Tool. Users may not modify that worksheet.
Adding/removing rows, moving data, or making other
modifications jeopardize the ability of the Synthesis
Module to accurately analyze the data.

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Following data export, the module may be reset and run for an additional state.

Alternatively, you may run the remaining modules of the SIT to obtain a comprehensive
profile of emissions for your state.

1.4 Uncertainty

In the upper right-hand corner of the summary worksheet is a button: "Review discussion of
uncertainty associated with these results." By clicking on this button, you are taken to a
worksheet that discusses the uncertainty surrounding the activity data and emission factors,
and how the uncertainty estimates for this source category affect the uncertainty of the
emission estimates for your state.

1.5 References

AAPFCO. 2021. Commercial Fertilizers 2016. Association of American Plant Food Control
Officials and The Fertilizer Institute. University of Kentucky, Lexington, KY.

U.S. EPA. 2022a. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 - 2020.
Office of Atmospheric Programs, U.S. Environmental Protection Agency. Available at:
https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks-
1990-2020.

U.S. EPA. 2022b. Inventory of U.S. Greenhouse Gas Emissions and Sinks By State: 1990 -
2020. Office of Atmospheric Programs, U.S. Environmental Protection Agency. Available
at:

https://www.epa.gov/system/files/documents/202208/StateGHGI_Methodology_Report_
August_2022.pdf.

Carpenter, G.H. 1992. "Current litter practices and future needs." 1992 National Poultry
Waste Management Symposium. Auburn University Printing Service. Auburn, Al.

Holzapfel-Pschorn, A., R. Conrad, and W. Seiler. 1985. Production, oxidation, and emission
of methane in rice paddies. FEMS Microbiology Ecology 31:343-351.

IPCC. 2006. 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Volume 4:
Agriculture, Forestry, and Other Land Use. The National Greenhouse Gas Inventories
Programme, The Intergovernmental Panel on Climate Change. [H.S. Eggleston, L.
Buendia, K. Miwa, T. Ngara, and K. Tanabe (eds.)]. Hayama, Kanagawa, Japan.

IPCC. 1997. IPCC Guidelines for National Greenhouse Gas Inventories, 3 volumes: Vol. 1,
Reporting Instructions; Vol. 2, Workbook; Vol. 3, Draft Reference Manual.
Intergovernmental Panel on Climate Change, Organization for Economic Co-Operation
and Development. Paris, France.

Lindau, C.W. and P.K. Bollich. 1993. "Methane Emissions from Louisiana First and Ratoon
Crop Rice." Soil Science 156: 42-48. July 1993.

Sass, R.L., F.M. Fisher, P.A. Harcombe, and F.T. Turner. 1990. "Methane production and
emission in a Texas rice field." Global Biogeochemical Cycles 4:47-68.

TVA. 1991 through 1994. Commercial Fertilizers. Tennessee Valley Authority, Muscle
Shoals, AL.

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U.S. Geological Survey. 2022. "Crushed Stone," 2019 Minerals Yearbook. U.S. Department
of the Interior/U.S. Geological Survey, Washington, D.C. Available online at:
https://www.usgs.gOv/centers/nmic/crushed-stone-statistics-and-information#myb..

West, T.O., and A.C. McBride. 2005. "The contribution of agricultural lime to carbon dioxide
emissions in the United States: dissolution, transport, and net emissions," Agricultural
Ecosystems & Environment 108:145-154.

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