Regulation of Fuels and Fuel Additives:


Renewable Fuel Standard Program


Summary and Analysis of Comments


Chapter 8


Impacts on Fossil Fuel Consumption


and Greenhouse Gases


Assessment and Standards Division 

Office of Transportation and Air Quality 

U.S. Environmental Protection Agency 

EPA420-R-07-006 

April 2007 
RFS Summary and Analysis of Comments 

8 IMPACTS ON FOSSIL FUEL CONSUMPTION AND GREENHOUSE GASES 

8.1 Lifecycle Modeling.......................................................................................... 8-1 

8.2 Impacts of Increased Renewable Fuel Use ...................................................... 8-2 

8.2.1 Model Used and Reduction Benefits Calculated ..................................... 8-2 

8.2.2 Use of FUEL-CO2 Model........................................................................ 8-3 

8.2.3 Relative Fuel and Energy Savings of Renewable Fuels .......................... 8-4 

RFS Summary and Analysis of Comments 

8 IMPACTS ON FOSSIL FUEL CONSUMPTION AND GREENHOUSE GASES 

What We Proposed: 

The comments in this section correspond to Section IX of the preamble to the 

proposed rule and are targeted at the effects of renewable fuel use on fossil fuel 

consumption and greenhouse gases and other related implications. A summary of the 

comments received and our response to those comments are located below. 

8.1 Lifecycle Modeling 

[Note: Comments related to the use of lifecycle analyses in setting Equivalence Values 

are addressed in Section 3.5] 

What Commenters Said: 

Several commenters raised the issue of building consensus on renewable fuels 

lifecycle modeling assumptions and inputs, and they indicated support for EPA to initiate 

a public dialogue on lifecycle modeling. The American Petroleum Institute (API) and 

Marathon Petroleum Company (MPC) believed that such a dialogue should include a 

discussion of the “boundaries” of lifecycle models, i.e., how the overall problem is 

defined. The Union of Concerned Scientists (UCS) commented that EPA, in cooperation 

with other appropriate agencies, should put a flexible process in place within this rule to 

establish reporting standards and develop a scientific consensus on lifecycle values. 

Letters:

American Petroleum Institute (API) OAR-2005-0161-0185 

Marathon Petroleum Company (MPC) OAR-2005-0161-0175 

Union of Concerned Scientists (UCS) OAR-2005-0161-0226 

Our Response: 

This rulemaking is an initial step in the public dialog process for reviewing 

lifecycle modeling inputs and assumptions used to represent benefits of increased 

renewable fuel use. There currently exists no organized, comprehensive dialogue among 

stakeholders about the appropriate tools and assumptions behind any renewable fuel 

lifecycle analyses, but this is one of our goals. Conclusions reached from such a dialogue 

could lead to the use of lifecycle analyses in future actions to establish incentives for 

renewable fuels. We will be initiating more comprehensive discussions about lifecycle 

analyses with stakeholders in the near future. 

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Chapter 8: Greenhouse Gas and Fossil Fuel Impacts 

8.2 Impacts of Increased Renewable Fuel Use 

8.2.1 Model Used and Reduction Benefits Calculated 

What Commenters Said: 

EPA received comments from three organizations concerned with greenhouse gas (GHG) 

reductions from renewable fuels displacing conventional fuels. The Renewable Fuels 

Association (RFA) emphasized the inherent benefits of renewable fuels with respect to GHG 

reductions, and Environmental Defense strongly supported recognizing and rewarding any and 

all methods, including waste-derived power generation, that reduce the greenhouse gas profile of 

biofuels. 

API commented at length on EPA’s use of Argonne National Laboratory’s 

GREET model for conducting renewable fuels lifecycle analysis. The commenter noted 

that different studies reveal that different models yield different results with respect to 

estimating greenhouse gas reductions from corn-based ethanol and biodiesel versus 

conventional fuel, and that these differences may stem from model assumptions related to 

the energy output/input ratios of ethanol and fossil fuels. API also commented that the 

extent to which the GREET model accounted for emissions from land use changes 

associated with biofuels production was unclear. 

Letters:

American Petroleum Institute (API) OAR-2005-0161-0185

Environmental Defense OAR-2005-0161-0172, -0223 

Renewable Fuels Association (RFA) OAR-2005-0161-0192, -0228 (hearing) 

Our Response: 

EPA acknowledges that several other models, other than the GREET model, have 

been developed for conducting renewable fuels lifecycle analysis. For example, 

researchers at the Energy and Resources Group (ERG) of the University of California 

Berkeley have developed the ERG Biofuel Analysis Meta-Model (EBAMM) and Mark 

Delucchi at the Institute of Transportation Studies of the University of California Davis 

has developed the Lifecycle Emissions Model (LEM). There are also other non-fuel 

specific lifecycle modeling tools that can be used to perform renewable fuel lifecycle 

analyses. 

Several studies have been released recently making use of these other models and 

showing slightly different results than we find in the analysis done for this rule. For 

example, whereas GREET estimates a net GHG reduction of about 22% for corn ethanol 

compared to gasoline, the previously cited works by Farrell et al. utilizing the EBAMM 

show around a 13% reduction. While there may be small differences in the models in 

terms of emissions and energy uses associated with ancillaries (e.g., emissions to produce 

fertilizer, electricity, etc.) the main difference in results is not due to the model used but 

assumptions on scope and input data used. 

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RFS Summary and Analysis of Comments 

For example, most studies focus on average or current ethanol production, which 

uses a current mix of wet and dry mill ethanol production, and coal and natural gas as 

process energy. In contrast, we consider new or marginal ethanol production which 

implies a higher portion of more efficient dry mill production and mix of process fuels. 

Other studies also typically base ethanol and farm energy use on historic data while we 

are assuming a state of the art dry milling plant and more current farming energy use 

data. Assumptions concerning agriculture-related GHG emissions could also have an 

impact on overall results. Other studies also differ in the environmental flows 

considered. For example, Delucchi uses different types of greenhouse gases and global 

warming potentials compared to those used in this final rulemaking to determine GHG 

emissions. 

The differences found by different studies and models used emphasize the 

importance of the input data and methodology when using lifecycle analysis. It also 

shows how dependent this type of analysis is on the assumptions made throughout the 

model. Based on differences in scope and input data considered between these other 

studies and what we defined in this analysis, we believe the differences in results that are 

seen are reasonable and the values we are obtaining from our use of the GREET model 

are acceptable for this analysis. 

The issue of CO2 emissions from land use change associated with converting 

forest or CRP land into crop production for use in producing renewable fuels is an 

important factor to consider when determining the overall sustainability of renewable fuel 

use. While the analysis done for this final rulemaking is indicating that there will not be 

a significant change in land use, this is an area we will continue to research for any future 

analysis. 

8.2.2 Use of FUEL-CO2 Model 

What Commenters Said: 

In the proposed rule, EPA discussed the “FUEL-CO2” model for estimating 

lifecycle greenhouse gas emissions and fossil energy usage. API and MPC commented 

that no information was provided on the “FUEL-CO2” model either in the draft RIA or 

on the EPA website, and that EPA should provide appropriate notice and opportunity for 

public comment on the model if it is to be used for regulatory purposes. 

Letters: 

American Petroleum Institute (API) OAR-2005-0161-0185 

Marathon Petroleum Company (MPC) OAR-2005-0161-0175 

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Chapter 8: Greenhouse Gas and Fossil Fuel Impacts 

Our Response: 

EPA’s final rulemaking does not make use of the FUEL-CO2 model. We will 

continue to evaluate the FUEL-CO2 model as a potential tool for future regulatory 

actions, and will provide the opportunity for public input and comment if we decide in 

the future to use the model for regulatory purposes. 

8.2.3 Relative Fuel and Energy Savings of Renewable Fuels 

What Commenters Said: 

A private citizen commented that he has concerns that EPA has not looked at the 

issue of using alternate fuels to decrease the dependency on crude oil. The commenter 

noted that he previously studied a number of alternate sources of fuel for a specific 

company and found that many were not energy savers. He also noted that, at that time, 

ethanol took more energy to produce than a gallon of ethanol provided as a fuel source. 

The commenter also stated that, in some cases, it might be electrical energy that makes 

up the difference. He noted, however, that this could require the construction of more 

powerhouses as the country is close to overloading the current electrical generating 

capacity. 

Letters:

Private Citizen OAR-2005-0161-0156 

Our Response: 

Our lifecycle analyses do examine the impacts of renewable fuels on consumption 

of fossil fuels and dependence on foreign sources of petroleum. See Section IX of the 

preamble to the final rule. However, these analyses we were meant only to provide an 

indication of the potential impacts of the rule. They were not used in the development of 

the RFS program. 

The Energy Act provided no authority to include the impacts of changes in the 

electrical power industry in the development of the RFS program, nor did it provide 

authority to account for renewable fuels used for the production of electricity in the RFS 

program. However, to the degree that electricity was a factor in the GREET model used 

for our lifecycle analyses, our lifecycle estimates did account for it. 

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