2020 National Emissions Inventory Technical Support Document: Waste Disposal Composting


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2020 National Emissions Inventory Technical
Support Document: Waste Disposal -
Composting

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EP A-454/R-23 -001 gg
March 2023

2020 National Emissions Inventory Technical Support Document: Waste Disposal - Composting

U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Air Quality Assessment Division
Research Triangle Park, NC

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Contents

List of Tables	i

33	Waste Disposal - Composting	33-1

33.1	Sector Descriptions and Overview	33-1

33.2	EPA-developed emissions	33-1

33.2.1	Activity Data	33-2

33.2.2	Allocation Procedure	33-4

33.2.3	Emissions Factors	33-6

33.2.4	Controls	33-6

33.2.5	Emissions	33-6

33.2.6	Sample Calculations	33-7

33.2.7	Improvements/Changes in the 2020 NEI	33-8

33.2.8	Puerto Rico and U.S. Virgin Islands Emissions Calculations	33-8

33.3	References	33-8

List of Tables

Table 33-1: Composting SCCs in the 2020 NEI	33-1

Table 33-2: Annual Waste (million tons) generated and recovered in the US in 2015	33-2

Table 33-3: State-level food waste composting (tons)	33-3

Table 33-4: Ranges and midpoints for data withheld from state and county business patterns	33-5

Table 33-5: 2016 County Business Pattern for NAICS 562212 in Arizona	33-5

Table 33-6: Sample calculations for VOC emissions from greenwaste composting in Apache County, AZ
	33-7

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33 Waste Disposal - Composting

There are five sections in this documentation that discuss nonpoint inventory Waste Disposal. This
section discusses Composting, the second section (34) discusses Open Burning - Land Clearing Debris,
the third section (35) discusses Open Burning - Residential Household Waste, the fourth section (36)
discusses Open Burning - Yard Waste, and the fifth section (37) discusses Publicly-Owned Treatment
Works (POTWs). The reason these sources are broken up within this EIS sector is because the EPA
methodologies for estimating the emissions are different.

33.1 Sector Descriptions and Overview

Greenwaste composting includes the diversion of yard waste, food waste, and other biogenic waste
from landfills to composting facilities. Estimates of emissions of volatile organic compounds (VOC),
ammonia (NH3), and three hazardous air pollutants (HAPs), acetaldehyde; methanol; and naphthalene,
from greenwaste composting are based on the amount of food and yard waste composted. Composting
of biogenic waste is currently not included in emissions estimates for this category as activity data on
this waste type is not available.

Note that this source category does not include the composting of biosolids from wastewater treatment
plants or manure management facilities. There are separate SCCs for biosolids (2680001000) and for a
mixture of greenwaste and biosolids (2680002000). EPA is not currently estimating emissions for these
SCCs. If S/L/Ts report any emissions for the mixture SCC, emissions from the greenwaste portion of that
mixture may be duplicative of some or all of the EPA emissions estimates described here. Note also that
this source category estimates emissions from composting facilities but does not estimate emissions
from backyard composting.

Table 33-1 shows, for composting, the SCCs covered by the EPA estimates and by the State/Local and
Tribal agencies that submitted data. The SCC level 3 and 4 SCC descriptions are also provided. The SCC
level 1 and leading level 2 descriptions is "Waste Disposal, Treatment, and Recovery; Composting:" for
all SCCs.

Table 33-1: Composting SCCs in the 2020 NEI

SCC

Description

EPA

S/L/T

2680001000

100% Biosolids (e.g., sewage sludge, manure, mixtures of these matls); All
Processes

2680002000

Mixed Waste (e.g., a 50:50 mixture of biosolids and green wastes); All Processes

2680003000

100% Green Waste (e.g., residential or municipal yard wastes); All Processes

A list of agencies that submitted composting emissions is provided in Section 6.2.3.

33.2 EPA-developed emissions

The calculations for estimating the emissions from greenwaste composting involve first estimating the
amount of food and yard waste composted in each county. The amount of state-level food waste
composted is available from the EPA report Food Waste Management in the United States, 2014 [ref 1]
The amount of state-level yard waste composted is estimated by calculating the per-capita amount of

33-1

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yard waste composted using national data from the EPA report Advancing Sustainable Materials
Management: 2015 Fact Sheet [ref 2] and multiplying that by the state population. The state-level yard
and food waste are summed together and distributed to the counties based on the proportion of
employment at solid waste landfills. The total amount of greenwaste composted is multiplied by
emissions factors for VOC and NH3 to estimate emissions of these pollutants from greenwaste
composting.

33.2.1 Activity Data

The activity data for this source category is the amount of food and yard waste composted, which is
estimated using data from two EPA reports: the national-level amount of yard waste composted comes
from Advancing Sustainable Materials Management: 2015 Fact Sheet and the state-level amount of
food waste composted comes from Food Waste Management in the United States, 2014 [ref 1, ref 2],
Table 33-2 shows the total national-level amount of yard waste generated and recovered for
composting.

Table 33-2: Annual Waste (million tons) generated and recovered in the US in 2015

Material

Waste
Generated

Waste Recovered

Yard trimmings

34.72

21.29

The values from Table 33-2 are used with the U.S. population in 2020 of 336 million people [ref 3] to
determine per-capita values of food and yard waste recovered for composting.

Wyard.US	(1)

i^yard,US	D

rUS

Where:

PCyard,us = Per-capita yard waste recovered for composting in the US, in tons per person per
year

Wyard,us = Total annual yard waste recovered in the US, in tons/year
Pus = US population

This calculation results in per-capita values of approximately 0.066 tons per person per year of yard
waste recovered for composting. Please note that EPA data on composting does not include backyard
composting.

The per-capita yard waste values from equation 1 are multiplied by the population of each state to
estimate the state-level amount of yard waste recovered for composting.

^Tyard,s P^yard,US ^	(2)

Where:

Wyard,s = Annual yard waste recovered for composting in state s, in tons

PCyard,us= Per-capita yard waste recovered for composting in the US, in tons per person per year

33-2

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Ps = Population of state s

EPA reports the amount of food waste composted at the state level in the report Food Waste
Management in the United States, 2015 [Table 3 in ref 1], These values are shown in Table 33-3. EPA
collected these data from state environmental websites and contacts with state agencies. The data year
for each state is listed and represents the latest data available. The data were not altered from the
original reference for use in this methodology.

	Table 33-3: State-level food waste composting (tons)	

State

Food
Composted

Data
Year

California

715,119

2012

Colorado

29,130

2013

Connecticut

4,644

2013

Delaware

17,626

2013

Florida

158,711

2014

Georgia

8,021

2014

Hawaii

39,287

2014

Indiana

13,525

2013

Iowa

4,334

2010

Kansas

1,127

2010

Maine

1,658

2010

Maryland

69,643

2014

Massachusetts

2,753

2014

Michigan

8,700

2013

Minnesota

46,751

2013

Mississippi

242

2013

Missouri

16,000

2014

State

Food
Composted

Data
Year

Nevada

35,869

2014

New Hampshire

110

2012

New Jersey

28,634

2012

New York

44,405

2013

North Carolina

38,014

2014

Ohio

81,450

2014

Oregon

50,143

2013

Pennsylvania

56,851

2013

Rhode Island

150

2014

South Carolina

4,277

2014

Tennessee

1,500

2013

Texas

188

2012

Vermont

14,738

2013

Virginia

2,454

2014

Washington

65,221

2013

Wisconsin

8,677

2013

Total

1,569,952



The state-level amount of total greenwaste composted is the sum of the state-level food and yard waste
composted.

Wqw,s Wyard,s ^food,s	(3)

Where:

WGw,s = Annual total greenwaste recovered for composting in state s, in tons

Wyard,s = Annual yard waste recovered for composting in state s, in tons

Wfood,s = Annual food waste recovered for composting in state s, in tons, from Table 33-3

The process used to distribute the state-level amount of greenwaste composted to the counties is
discussed in next section.

33-3

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33.2.2 Allocation Procedure

Comprehensive data on the county locations of composting facilities is not available. As a result, the
analysis assumes that greenwaste composting facilities are co-located with solid waste landfills.

State-level food greenwaste composting activity (from equation 3) is allocated to the county-level using
employment at solid waste landfills (NAICS code 562212). Specifically, state-level estimates of
greenwaste collected for composting are multiplied by the ratio of county- to state- level number of
employees at landfills.

Empc (4)

EmpFracc =

Emps

Where:

EmpFracc = The fraction of landfill employees in county c
Empc = The number of landfill employees in county c
Emps = The number of landfill employees in state s

Employment data are from the U.S. Census Bureau's 2016 County Business Patterns (CBP) [ref 4], Due to
concerns with releasing confidential business information, the CBP does not release exact numbers for a
given NAICS code if the data can be traced to an individual business. Instead, a series of range codes is
used. Many counties and some smaller states have only one solid waste landfill, leading to withheld data
in the county and/or state business pattern data. To estimate employment in counties and states with
withheld data, the following procedure is used for NAICS code 562212.

To gap-fill withheld state-level employment data:

a. State-level data for states with known employment in NAICS 562212 are summed to the
national level.

b. The total sum of state-level known employment from step a is subtracted from the national
total reported employment for NAICS 562212 in the national-level CBP to determine the
employment total for the withheld states.

c. Each of the withheld states is assigned the midpoint of the range code reported for that state.
Table 33-4 lists the range codes and midpoints.

d. The midpoints for the states with withheld data are summed to the national level.

e. An adjustment factor is created by dividing the number of withheld employees (calculated in
step b of this section) by the sum of the midpoints (step d).

f. For the states with withheld employment data, the midpoint of the range for that state (step c)
is multiplied by the adjustment factor (step e) to calculate the adjusted state-level employment
for landfills.

These same steps are then followed to fill in withheld data in the county-level business patterns.

g. County-level data for counties with known employment are summed by state.

h. County-level known employment is subtracted from the state total reported in state-level CBP
(or, if the state-level data are withheld, from the state total estimated using the procedure
discussed above).

33-4

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i. Each of the withheld counties is assigned the midpoint of the range code (Table 33-4).

j. The midpoints for the counties with withheld data are summed to the state level.

k. An adjustment factor is created by dividing the number of withheld employees (step h) by the

sum of the midpoints (step j).

I. For counties with withheld employment data, the midpoints (step i) are multiplied by the
adjustment factor (step k) to calculate the adjusted county-level employment for landfills.

Table 33-4: Ranges and midpoints for data withheld from state and county business patterns

Employment Code

Ranges

Midpoint

0-19

20-99

100-249

175

250-499

375

500-999

750

1,000-2,499

1,750

2,500-4,999

3,750

5,000-9,999

7,500

10,000-24,999

17,500

25,000-49,999

37,500

50,000-99,999

75,000

100,000+

For example, take the 2016 CBP data for NAICS 562212 (Landfills) in Arizona provided in Table 33-5.

Table 33-5: 2016 County Business Pattern for NAICS 562212 in Arizona

State
FIPS

County
FIPS

County
Name

NAICS

Employment
Code

Employment

001

Apache

562212

withheld

007

Gila

562212

withheld

012

La Paz

562212

withheld

013

Maricopa

562212

296

015

Mohave

562212

withheld

017

Navajo

562212

withheld

021

Pinal

562212

023

Santa Cruz

562212

withheld

025

Yavapai

562212

withheld

027

Yuma

562212

withheld

Note: Counties in Arizona that do not have employment in solid waste
landfills are excluded from this table.

1. The total number of known county-level employees in Arizona is 336.

2. The state-level CBP reports 522 employees for NAICS 562212 in Arizona. This means there are
186 employees total for the 8 counties for which data are withheld.

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3. The counties with withheld data are assigned midpoints according to their employment code in
Table 33-4. For example, Apache County is given a midpoint of 60 employees (since range code
B is 20-99) and Gila County is given a midpoint of 10 employees.

4. The state total of the midpoints for all withheld counties is 270 employees.

5. The adjustment factor is 186/272 = 0.6889.

6. The adjusted employment for Apache County is 60 x 0.6889 = 41. Gila County has an adjusted
employment of 10 x 0.6889 = 7 employees.

Once county- and state-level employment have been estimated, the ratio of county to state employees
(from equation 4) is calculated and multiplied by the state-level greenwaste recovered for composting
(from equation 3) to calculate the amount of waste composted in each county.

Wgw,c = EmpFracc x WGWtS (5)

Where:

WGw,c = Annual total greenwaste composted in county c, in tons

WGw,s = Annual total greenwaste recovered for composting in state s, in tons

EmpFracc = The fraction of landfill employees in county c

33.2.3 Emissions Factors

Emissions factors for greenwaste composting (SCC=2680003000) are provided in the "Wagon Wheel
Emission Factor Compendium" on the 2020 NEI Supporting Data and Summaries site. The emissions
factors for VOC and ammonia (NH3) are taken from the California Air Resources Board Emissions
Inventory Methodology for Composting Facilities [ref 5] and are unaltered from the original reference.
The emissions factors for the HAPs (acetaldehyde, methanol, and naphthalene) are taken from Kumar et
al [ref 6],

33.2.4 Controls

There are no controls assumed for this category.

33.2.5 Emissions

Emission factors are provided in the "Wagon Wheel Emission Factor Compendium" on the 2020 NEI
Supporting Data and Summaries site. For VOC and NH3, the emissions are multiplied by a conversion
factor to convert from pounds to tons.

1 ton (6)

EP,C = WCWiC x EFp x 2000 Ws

Where:

Ep,c = Annual emissions of pollutant p in county c, in tons for VOC and NH3 and lbs. for HAPs

33-6

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Wgw,c = Annual total greenwaste recovered for composting in state s, in tons

EFP = Emissions factor for pollutant p, in tons of pollutant per ton of greenwaste composted

Emissions of HAPs are estimated by applying speciation factors (available in the zip file
"HAPAugmentation_Nonpoint_28jan2023", on the 2020 NEI Supplemental data FTP site) to annual VOC
emissions. For HAPS, no conversion factor is needed, and the emissions are reported in tons.

Eh,c = EVOc,c x SFh	(?)

Where:

Eh,c= Annual emissions of HAP h in county c, in tons per year
Evoqc = Annual VOC emissions in county c, in tons

SFh= Speciation factor for HAP h, in tons of HAP emissions per ton of VOC emissions
33.2.6 Sample Calculations

Table 33-6 lists sample calculations to determine the VOC emissions from composting of greenwaste in
Apache County, Arizona.

Table 33-6: Sample calculations for VOC emissions from greenwaste composting in Apache County, AZ

Eq.#

Equation

Values for Apache County, AZ

Result

1

Wyard,us
*^yard,US D

rUS

21.08 million tons yard waste
329 million people

0.064 tons yard
waste per person
per year

2

^Tyard,s P^yard,US ^

0.064 tons yard waste per person
x 7,016,270 people inAZ

449,041 tons yard
waste composted in
AZ

3

Wqw,s Wyard,s ^food,s

449,041 tons yard waste

+ 0 tons food waste

443,520 tons green-
waste composted in
AZ

4

„	EmPc

41 employees in Apache County

0.079 fraction of
solid waste
employees in
Apache County, AZ

i-d 11 iUl 1

Emps

522 employees inAZ

5

Wcw.c = EmpFracc x WGWiS

0.079 fraction

x 443,520 tons greenwaste composted

35,038 tons
greenwaste
composted in
Apache County, AZ

6

Ep,c ^GW,c ^ EFp

1 ton
X 2000 lbs.

35,038tons greenwaste
x 4.67 lbs. VOC per ton greenwaste
1 ton

X 2000 lbs.

82 tons VOC
emissions from
greenwaste
composting in
Apache County, AZ

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33.2.7 Improvements/Changes in the 2020 NEI

There are no significant changes from the methodology used to calculate the 2020 NEI emissions.

33.2.8 Puerto Rico and U.S. Virgin Islands Emissions Calculations

Emissions from Puerto Rico are calculated using the same method described above. For the U.S. Virgin

Islands, emissions are calculated using 2020 population data [ref 7], since 2014 Census Data does not

exist for the U.S. Virgin Islands.

33.3 References

1. U.S. EPA. 2016. Food Waste Management in the United States, 2014. Office of Resource
Conservation and Recovery.

2. U.S. EPA. 2018. Advancing Sustainable Materials Management: Facts and Figures Report. 2015
Facts and Figures Sheet, Tablel. Generation, Recovery, and Discards of Products in MSW, 2015.

3. U.S. Census Bureau. 2020 Total Population. American Community Survey.

4. U.S. Census Bureau. 2020 County Business Patterns.

5. California Air Resources Board. 2015. ARB Emissions Inventory Methodology for Composting
Facilities. Table A-4. Emission factor data taken from Draft Staff Report on Proposed Amended
Rule 1133.1 (chipping and grinding activities) and Proposed Rule 1133.3 (emissions reductions
from greenwaste composting operations),Table 111-3.

6. Kumar, A., C.P. Alaimo, R. Horowitz, F.M. Mitloehner, M.J. Kleeman, and P.G. Green. 2011.
Volatile organic compound emissions from green waste composting: Characterization and ozone
formation. Atmospheric Environment, 45:1841-1848.

7. U.S. Census Bureau. 2020. County Population Totals.

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United States	Office of Air Quality Planning and Standards	Publication No. EPA-454/R-23-001gg

Environmental Protection	Air Quality Assessment Division	March 2023

Agency	Research Triangle Park, NC

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