Technical Highlights
 

EPA Lifecycle Analysis of Greenhouse 

Gas Emissions from Renewable Fuels 

As part of proposed revisions to the National Renewable Fuel 

Standard program (commonly known as the RFS program), EPA 

analyzed lifecycle greenhouse gas (GHG) emissions from increased 

renewable fuels use. The Energy Independence and Security Act of 

2007 (EISA) establishes new renewable fuel categories and eligibility requirements. EISA sets the first U.S. mandatory lifecycle GHG 

reduction thresholds for renewable fuel categories, as compared to 

those of average petroleum fuels used in 2005. The regulatory purpose of the lifecycle greenhouse gas emissions analysis is to determine 

whether renewable fuels meet the GHG thresholds for the different 

categories of renewable fuel. 

Lifecycle GHG emissions are the aggregate quantity of GHGs related to the full fuel 

cycle, including all stages of fuel and feedstock production and distribution, from 

feedstock generation and extraction through distribution and delivery and use of the 

finished fuel. The lifecycle GHG emissions of the renewable fuel are compared to the 

lifecycle GHG emissions for gasoline or diesel (whichever is being replaced by the 

renewable fuel) sold or distributed as transportation fuel in 2005. 

EISA established specific greenhouse gas emission thresholds for each of four types of 

renewable fuels, requiring a percentage improvement compared to a baseline of the 

gasoline and diesel. EISA required a 20% reduction in lifecycle GHG emissions for 

any renewable fuel produced at new facilities (those constructed after enactment), a 

50% reduction in order to be classified as biomass-based diesel or advanced biofuel, 

and a 60% reduction in order to be classified as cellulosic biofuel. EISA provides 

some limited flexibility for EPA to adjust these GHG percentage thresholds downward by up to 10 percent under certain circumstances. EPA is proposing to exercise 

this flexibility for the advanced biofuels category in this proposal. 

Office of Transportation and Air Quality 

EPA-420-F-09-024 

May 2009 
 

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EPA must conduct a lifecycle analysis to determine whether or not renewable fuels produced 

under varying conditions will meet the greenhouse gas (GHG) thresholds for the different fuel 

types for which EISA establishes mandates. While these thresholds do not constitute a control 

on greenhouse gases for transportation fuels (such as a low carbon fuel standard), they do require 

that the volume mandates be met through the use of renewable fuels that meet certain lifecycle 

GHG reduction thresholds when compared to the baseline lifecycle emissions of petroleum fuel. 

Determining compliance with the thresholds requires a comprehensive evaluation of renewable fuels, as well as of gasoline and diesel, on the basis of their lifecycle emissions. EISA defines 

lifecycle GHG emissions as follows: 

The term ‘lifecycle greenhouse gas emissions’ means the aggregate quantity of 

greenhouse gas emissions (including direct emissions and significant indirect 

emissions such as significant emissions from land use changes), as determined by 

the Administrator, related to the full fuel lifecycle, including all stages of fuel and 

feedstock production and distribution, from feedstock generation or extraction 

through the distribution and delivery and use of the finished fuel to the ultimate 

consumer, where the mass values for all greenhouse gases are adjusted to account 

for their relative global warming potential.1 

As mandated by EISA, the greenhouse gas emission assessments must evaluate the full lifecycle 

emission impacts of fuel production including both direct and indirect emissions, including significant emissions from land use changes. We recognize the significance of using lifecycle greenhouse gas emission assessments that include indirect impacts such as emission impacts of indirect land use changes. Therefore, in our proposal we have been transparent in breaking out the 

various sources of GHG emissions to enable the reader to readily detect the impact of including 

international land use impacts. 

EPA has analyzed the lifecycle GHG impacts of the range of biofuels currently expected to 

contribute significantly to meeting the volume mandates of EISA through 2022, including those 

from domestic and international sources. In these analyses we have used the best science available. Our analysis relies on peer reviewed models and the best estimate of important trends in 

agricultural practices and fuel production technologies as these may impact our prediction of individual biofuel GHG performance through 2022. We have identified and highlighted assumptions and model inputs that particularly influence our assessment and seek comment on these assumptions, the models we have used and our overall methodology so as to assure the most robust 

assessment of lifecycle GHG performance for the final rule. 

The GHG lifecycle analysis combines a suite of peer-reviewed process models and peer-reviewed 

economic models of the domestic and international agricultural sectors to determine direct and 

significant indirect emissions, respectively (see Figure 1). As required by EISA, the broad system 

boundaries of our analysis encompass all significant secondary agricultural sector GHG impacts, 

not only impacts from land use change. The analysis uses economic models to determine the 

area and location of land converted into cropland in each country as a result of the RFS 

1 Clean Air Act Section 211(o)(1) 

2 
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program. Satellite data are used to predict the types of land that would be converted into cropland (e.g. forest, grassland). 

EPA’s draft results suggest that biofuel-induced land use change can produce significant nearterm GHG emissions; however, displacement of petroleum by biofuels over subsequent years can 

“pay back” earlier land conversion impacts. Therefore, the time horizon over which emissions 

are analyzed and the application of a discount rate to value near-term versus longer-term emissions are critical factors. We highlight two options. One option assumes a 30 year time period 

for assessing future GHG emissions impacts and values equally all emission impacts, regardless of 

time of emission impact (i.e., 0% discount rate). The second option assesses emissions impacts 

over a 100 year time period and discounts future emissions at 2% annually. Several other variations of time period and discount rate are also discussed in the proposed rule. Table 1 provides 

draft GHG emission reductions that result under two time horizon/discount rate approaches 

for a sample of fuel pathways evaluated in the proposed rulemaking. Figures 1 and 2 break out 

emissions for each of these pathways by lifecycle component (e.g. fuel production, domestic and 

international and use change, domestic and international agricultural inputs) for the two time 

horizon/discount rate approaches. 

Table 1. Draft Lifecycle GHG Emission Reduction Results
 

For Different Time Horizon And Discount Rate Approaches.
 

100 year, 2% 30 year, 0% Discount 

Fuel Pathway Discount Rate Rate 

Corn Ethanol (Natural Gas Dry Mill) -16% +5% 

Corn Ethanol (Best Case Natural Gas 

Dry Mill)2 -39% -18% 

Corn Ethanol (Coal Dry Mill) +13% +34% 

Corn Ethanol (Biomass Dry Mill) -39% -18% 

Corn Ethanol (Biomass Dry Mill with 

Combined Heat and Power) -47% -26% 

Soy-Based Biodiesel -22% +4% 

Waste Grease Biodiesel -80% -80% 

Sugarcane Ethanol -44% -26% 

Switchgrass Ethanol -128% -124% 

Corn Stover Ethanol -115% -116% 

2 Best case plants produce wet distillers grain co-product and include the following technologies: 

combined heat and power (CHP), fractionation, membrane separation and raw starch hydrolysis 


 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Gasoline Baseline 

Corn Ethanol (dry mi ll natural gas) 

Corn Ethanol (best case dry mi ll natrual gas) 

Corn Ethanol (dry mi ll coal) 

Corn Ethanol (dry mi ll bioma ss) 

Corn Ethanol (dry mi ll bioma ss with CHP) 

Sugarcane Ethanol 

Switchgra ss Ethanol 

Corn Stover Ethanol 

Diesel Fuel Baseline 

Soy-Based Biodiesel 

Waste Grease Biodiesel 

Gasoline Baseline 

Corn Ethanol (dry mi ll natural gas) 

Corn Ethanol (best case dry mi ll natrual gas) 

Corn Ethanol (dry mi ll coal) 

Corn Ethanol (dry mi ll bioma ss) 

Corn Ethanol (dry mi ll bioma ss with CHP) 

Sugarcane Ethanol 

Switchgra ss Ethanol 

Corn Stover Ethanol 

Diesel Fuel Baseline 

Soy-Based Biodiesel 

Waste Grease Biodiesel 

Figure 1. Net Lifecycle Greenhouse Gas Emissions By Lifecycle Component With 

100 Year Time Horizon And 2% Discount Rate. 

-3 , 0 0 0 , 0 0 0 

-2 , 0 0 0 , 0 0 0 

-1 , 0 0 0 , 0 0 0 

0 

1 , 0 0 0 , 0 0 0 

2 , 0 0 0 , 0 0 0 

3 , 0 0 0 , 0 0 0 

4 , 0 0 0 , 0 0 0 

5 , 0 0 0 , 0 0 0 

6 , 0 0 0 , 0 0 0 

GHG Emissions (gCO2eq / mmBtu) 

D o m e s t i c A g ( w / o l a n d u s e c h a n g e ) D o m e s t i c L a n d U s e C h a n g e I n t e r n a t i o n a l A g ( w / o l a n d u s e c h a n g e ) 

I n t e r n a t i o n a l L a n d U s e C h a n g e F u e l a n d F e e d s t o c k T r a n s p o r t F u e l P r o d u c t i o n 

T a i l p i p e 

Figure 2. Net Lifecycle Greenhouse Gas Emissions By Lifecycle Component With 

30 Year Time Horizon And 0% Discount Rate. 

5 , 0 0 0 , 0 0 0 

4,000,000 

3,000,000 

2,000,000 

1,000,000 

0 

-1,000,000 

-2,000,000 

GHG Emissions (gCO2eq / mmBtu) 

D o m e s t i c A g ( w / o l a n d u s e c h a n g e ) D o m e s t i c L a n d U s e C h a n g e I n t e r n a t i o n a l A g ( w / o l a n d u s e c h a n g e ) 

I n t e r n a t i o n a l L a n d U s e C h a n g e F u e l a n d F e e d s t o c k T r a n s p o r t F u e l P r o d u c t i o n 

T a i l p i p e 

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4 
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We believe that our lifecycle analysis is based on the best available science, and recognize that 

in some aspects it represents a cutting edge approach to addressing lifecycle GHG emissions. 

Because of the varying degrees of uncertainty in the different aspects of our analysis, we conducted a number of sensitivity analyses which focus on key parameters and demonstrate how our 

assessments might change under alternative assumptions. By focusing attention on these key parameters, the comments we receive as well as additional investigation and analysis by EPA will 

allow narrowing of uncertainty concerns for the final rule. In addition to this sensitivity analysis 

approach, we will also explore options for more formal uncertainty analyses for the final rule to 

the extent possible. 

Because lifecycle analysis is a new part of the RFS program, in addition to the formal comment 

period on the proposed rule, EPA is making multiple efforts to solicit public and expert feedback 

on our proposed approach. EPA plans to hold a public workshop focused specifically on lifecycle 

analysis during the comment period to assure full understanding of the analyses conducted, 

the issues addressed and the options that are discussed. We expect that this workshop will help 

ensure that we receive submission of the most thoughtful and useful comments to this proposal 

and that the best methodology and assumptions are used for calculating GHG emissions impacts 

of fuels for the final rule. Additionally, between this proposal and the final rule, we will conduct 

peer-reviews of key components of our analysis. As explained in more detail in the section VI of 

the proposal, EPA is specifically seeking peer review of: our use of satellite data to project future 

the type of land use changes; the land conversion GHG emissions factors estimates we have 

used for different types of land use; our estimates of GHG emissions from foreign crop production; methods to account for the variable timing of GHG emissions; and how the several models 

we have relied upon are used together to provide overall lifecycle GHG estimates. 

Each component of our analysis is discussed in detail in the preamble and the Draft Regulatory 

Impact Analysis that accompany the Notice of Proposed Rulemaking. The proposed rule is an 

important opportunity to seek public comment on EPA’s entire lifecycle GHG analysis, including questions about land use modeling, and the choice of which time horizon and discount rate 

is most appropriate for this analysis. 

For More Information 

For more information on this proposal, please contact EPA’s Office of Transportation and Air 

Quality, Assessment and Standards Division information line at: 

U.S. Environmental Protection Agency 


Office of Transportation and Air Quality 


2000 Traverwood Drive 


Ann Arbor, MI 48105 


Voicemail: (734) 214-4636 


E-mail: asdinfo@epa.gov
 

Or visit: www.epa.gov/otaq/renewablefuels/index.htm