February 4, 2009
TECHNICAL SUPPORT DOCUMENT FOR
ETHANOL FACILITIES: PROPOSED RULE FOR
MANDATORY REPORTING OF GREENHOUSE
GASES
Climate Change Division
Office of Atmospheric Programs
U.S. Environmental Protection Agency
February 4, 2009
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CONTENTS
1. Industry Description 3
2. Total Emissions 3
3. Review of Existing Programs and Methodologies 3
4. Types of Emissions Information to be Reported 3
5. Options for Reporting Threshold 4
5.1 Source Emissions-based thresholds 4
5.2 Other threshold options 5
6. Options for Monitoring Methods 5
7. Options for Estimating Missing Data 6
8. QA/QC Requirements 6
9. References 6
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1. Industry Description
Ethanol is produced primarily for use as a fuel component, but is also used in industrial
applications and in the manufacture of beverage alcohol. Ethanol can be produced from
the fermentation of sugar, starch, grain, and cellulosic biomass feedstocks, or produced
synthetically from ethylene or hydrogen and carbon monoxide. There are approximately
140 ethanol refineries in the United States and its territories.
The sources of GHG emissions at ethanol production facilities considered in the analysis
for the proposed rule are stationary combustion, onsite landfills, and onsite wastewater
treatment.
Stationary combustion at ethanol facilities usually includes the combustion of either
natural gas or coal in boilers. Many wet milling facilities use co-generation.
Data is unavailable on landfilling at ethanol facilities, but it is believed that some of these
facilities may have landfills with significant GHG emissions.
The wastewater generated at ethanol production facilities is handled in a variety of ways,
with dry milling and wet milling facilities generally treating wastewaters differently.
2. Total Emissions
In 2006, CH4 emissions from wastewater treatment at ethanol production facilities were
68,200 mtCO2e, less than 1% of total CH4 emissions.
Estimates of total national emissions from landfills and stationary combustion at ethanol
facilities are unavailable.
3. Review of Existing Programs and Methodologies
For information on the review of existing programs and methodologies, please refer to
the Technical Support Documents for general stationary fuel combustion (EPA-HQ-
OAR-2008-004), landfills (EPA-HQ-OAR-2008-034), and wastewater treatment (EPA-
HQ-OAR-2008-035).
4. Types of Emissions Information to be Reported
For information on information to be reported, please refer to the Technical Support
Documents for general stationary fuel combustion (EPA-HQ-OAR-2008-004), landfills
(EPA-HQ-OAR-2008-034), and wastewater treatment (EPA-HQ-OAR-2008-035).
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5. Options for Reporting Threshold
5.1 Source Emissions-based thresholds
In evaluating thresholds for ethanol facilities, we first considered emissions-based
thresholds of CH4 generation ("generation threshold") and CH4 emissions ("emissions
threshold") at wastewater treatment systems of 1,000 mtCO2e, 10,000 mtCO2e, 25,000
mtCO2e, and 100,000 mtCC^e per year. Data on emissions from landfills at ethanol
refineries were unavailable to conduct similar analyses for this source. The "generation
threshold" is the amount of CH4 that would be emitted from the facility if no CH4
recovery takes place. This includes all CH4 generation from all wastewater treatment
system types at ethanol facilities, including digesters. The "emissions threshold"
includes the CH4 that is emitted to the atmosphere from these systems. In the emissions
threshold, CH4 that is recovered and combusted at digesters is taken into account and
deducted from the total CH4 generation calculated. Please see the Technical Support
Document for Wastewater (EPA-HQ-OAR-2008-035) for more information.
Table 1. Summary of Threshold Analysis for Industrial Wastewater Treatment at
Ethanol Refineries
Threshold
(mtCO2e)*
#
Systems
% Systems
Emissions
(mtCO2e)
% Emissions
Ethanol -Emissions Threshold
1,000
10,000
25,000
100,000
11
2
1
0
7.9
1.4
0.7
0
67,041
50,810
32,850
0
64
48
31
0
Ethanol - Generation Threshold
1,000
10,000
25,000
100,000
78
3
2
1
56
2.2
1.4
0.7
385,805
213,715
178,050
127,570
94
52
44
31
* Threshold analyzed is based on wastewater treatment emissions only.
A readily available dataset from the Renewable Fuels Association (RFA 2006) containing
production for all ethanol plants in operation as of July 2006 was used to estimate
emissions. This dataset distinguished between dry and wet milling plants; however, it did
not include plant-specific information on wastewater generation rates, influent BOD or
COD levels, or treatment processes on site. Therefore, default values from the U.S.
Inventory were used to calculate CH4 emissions.
For wet milling operations, it was assumed that all mills had anaerobic secondary
treatment in place in order to calculate plant-level emissions. The number of mills that
would meet each threshold was then counted. However, only 33% of mills are expected
to actually have anaerobic treatment onsite. Therefore, the plant counts in each threshold
were multiplied by 33% to estimate the number of plants believed to exceed the
threshold. Only two wet milling operations are expected to meet a threshold. To
estimate the total emissions for plants exceeding the threshold, the average emission rate
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for plants in each threshold was estimated and multiplied this average by the total number
of plants expected to have anaerobic treatment on site.
To be conservative, for dry milling operations, it was assumed that all mills had
anaerobic treatment in place and none operated a biomethanator. In keeping with the
U.S. Inventory estimation methodology, we assumed 25% of emissions from the systems
were emitted, and 75% were recovered. Even with these conservative assumptions, it
was found that there were no dry milling operations that meet any of the thresholds under
consideration.
The number of operations that have generation above the generation thresholds was
estimated. This estimation assumed there was no biogas recovery in place. For wet
milling operations, it was estimated that four plants would exceed the 1,000 tCC^e
threshold, three plants would exceed the 10,000 tCC^e threshold, two plants would
exceed the 25,000 tCO2e threshold, and one plant would exceed the 100,000 tCO2e
threshold. Seventy-five dry milling operations are expected to exceed the 1,000 tCC^e
threshold.
5.2 Other threshold options
EPA also considered a facility-level threshold for ethanol refineries. A limited data set
on stationary combustion at ethanol refineries and emission factors from IPCC and the
GHG Inventory was used to estimate the minimum number of facilities that would meet
each of the facility-level thresholds examined (Graboski 2002). Data were unavailable to
estimate emissions from landfills at ethanol refineries, or to estimate the combined
wastewater treatment and stationary combustion emissions at facilities.
Table 2 Threshold Analysis for Ethanol Production
Threshold Level
1,000 mtCo2e
1 0,000 mtCo2e
25,000 mtCo2e
1 00,000 mtCo2e
National
Emissions
mtCO2e
Not estimated
Not estimated
Not estimated
Not estimated
Total
Number
of
Facilities
140
140
140
140
Emissions Covered
mtCO2e
/year
Not
estimated
Not
estimated
Not
estimated
Not
estimated
Percent
Not
estimated
Not
estimated
Not
estimated
Not
estimated
Facilities Covered
Number
>101
>94
>86
>43
Percent
>72%
>67%
>61%
>31%
6. Options for Monitoring Methods
For information on monitoring methods, please refer to the Technical Support Documents
for general stationary fuel combustion (EPA-HQ-OAR-2008-004), landfills (EPA-HQ-
OAR-2008-034), and wastewater treatment (EPA-HQ-OAR-2008-035).
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7. Options for Estimating Missing Data
For information on options for estimating missing data, please refer to the Technical
Support Documents for general stationary fuel combustion (EPA-HQ-OAR-2008-004),
landfills (EPA-HQ-OAR-2008-034), and wastewater treatment (EPA-HQ-OAR-2008-
035).
8. QA/QC Requirements
For information on options for QA/QC requirements, please refer to the Technical
Support Documents for general stationary fuel combustion (EPA-HQ-OAR-2008-004),
landfills (EPA-HQ-OAR-2008-034), and wastewater treatment (EPA-HQ-OAR-2008-
035).
9. References
EPA. 2008. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2006 (April
2008) USEPA #430-R-08-005.
Graboski, M.S. 2002. "Fossil Energy Use in the Manufacture of Corn Ethanol", Prepared
for NCGA, August 2002. Available online at:
http://www.ncga.com/ethanol/pdfs/energy_balance_report_fmal_Rl.PDF.
IPCC. 2006. IPCC Guidelines for National Greenhouse Gas Inventories: Wastewater
Treatment and Discharge. IPCC (Volume 5 Waste, Chapter 6). Available online at:
http://www.ipcc-
nggip.iges.or.jp/public/2006gl/pdf/5_Volume5/V5_6_Ch6_Wastewater.pdf
RFA. 2006. Renewable Fuels Association (RFA). Historic U.S. fuel Ethanol Production.
Available online at: http://www.ethanolrfa.org/industry/statistics/. Date Accessed: June
2007.
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