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EPA Posts Peer Review of Renewable Fuel Standards Lifecycle Analysis

Steps in determining biofuel lifecycle emissions. Source: EPA workshop, June 2009. Click to enlarge.

The US Environmental Protection Agency (EPA) has posted the peer review of the renewable fuel standards lifecycle analysis—including significant indirect emissions, such as from indirect land use changes—online.

In May, EPA released its expected Notice of Proposed Rulemaking (NPRM) detailing the implementation of changes to the existing Renewable Fuel Standard (RFS1) as required by the Energy Independence and Security Act of 2007 (EISA). The proposed rulemaking includes new definitions and criteria for both renewable fuels and the feedstocks used to produce them, including new greenhouse gas emission (GHG) thresholds for renewable fuels and the incorporation of indirect land use change effects. (Earlier post.) At the time, Administrator Jackson announced the lifecycle analysis would be peer-reviewed.

ICF International, an independent third-party contractor, coordinated the peer reviews which were conducted on four areas of the lifecycle assessment that in particular charted new ground, according to EPA:

  • Land use modeling (use of satellite data/land conversion GHG emission factors)
  • Methods to account for the variable timing of GHG emissions
  • GHG emissions from foreign crop production (modeling and data used)
  • How the models EPA relied upon are used together to provide overall lifecycle estimates
EPA analysis of biofuel lifecycle GHG for select pathways with 0% discount rate, 30 years. Dashed red line is the threshold reduction for conventional fuels; dashed green line is the threshold reduction for cellulosic fuels; and dashed blue line is the threshold reduction for advanced biofuels and biodiesel fuels. Source: EPA workshop, June 2009. Click to enlarge.

Land use modeling. Participating in this review were Dr. Holly Gibbs, Stanford University; Dr. Richard Houghton, Woods Hole Oceanographic Institution; Dr. Rattan Lal, Ohio State University; Dr. Jason Tullis, University of Arkansas; and Dr. Brian Wardlow, University of Nebraska.

The peer reviewers generally agreed that the approach taken by EPA and Winrock International—EPA was scientifically justifiable, especially given existing data and technology constraints. (Winrock International determined the extent of land use change using MODIS imagery from 2001 and 2004 and estimating emission factors for each type of land use conversion for a number of key agriculturally producing countries around the world.)

However, the reviewers highlighted several problematic areas of the analysis and recommended possible revisions. In general, these problematic areas were part of the satellite imagery analysis, rather than the emissions factor analysis. The peer reviewers concurred more strongly with EPA’s approach in the latter analysis.

The main areas of concern with the satellite imagery analysis as outlined by the peer reviewers, in order of the frequency of comments received from peer reviewers, were:

  • The 3-year time period of the two MODIS data sets chosen and the error associated with each of those data sets.
  • The coarse resolution of the satellite imagery.
  • The change detection analysis performed on the two MODIS data sets from 2001 and 2004.
  • The reclassification analysis performed by Winrock on the satellite data, especially the categories of excluded land and the role of the ‘mixed’ or ‘other’ category.

Methods and approaches over time. Participating in this peer review were The contractor contacted the following five peer reviewers who agreed to participate in the peer review: Dr. Joseph Fargione, The Nature Conservancy; Mr. Ralph Heimlich, Agricultural Conservation Economics; Dr. Elizabeth Marshall, World Resources Institute; Dr. Jeremy Martin, Union of Concerned Scientists; and Dr. Kenneth Richards, Indiana University.

The main issues addressed in the peer review included (but were not limited to):

  • EPA’s approach to the GHG lifecycle analysis
  • EPA’s approach to accounting for lifecycle GHG emissions over time (e.g., applying “project” and “impact” time frames)
  • EPA’s approach to valuing future GHG emissions (e.g., choosing and using “discount rates”)
  • EPA’s use of a snapshot approach versus a more dynamic year-by-year approach (e.g., “scenario analysis”)

Most peer reviewers generally agreed that the approach taken by EPA was scientifically objective. However, Dr. Marshall commented that it was difficult to determine whether selection of the parameters followed a scientifically objective process because the discussion within the rulemaking documentation did not provide enough depth to justify the time accounting scenarios proposed.

The reviewers’ opinions of appropriate time frames varied considerably. Reviewers disagreed on whether EPA should use an impact time frame—the length over which to account for the changes in GHG emissions, in particular due to land-use changes, which result from biofuel production—or project time frame—how long production of a particular biofuel is expected to continue into the future.

Reviewers also disagreed on what duration the various time frames should have. Some recommended that EPA use both a project and an impact time frame within the analysis, and some introduced the concept of a “rolling” time frame. Reviewers offered time frame lengths ranging from 13 to 100 years.

Peer reviewers also had different opinions on the appropriateness of weighing emissions by applying a discount rate. All reviewers noted in some way that a discount rate should only be applied to a monetary unit, rather than a physical unit such as a carbon emission, although they acknowledged that since EPA was considering emissions to be a proxy for damages applying a discount rate was possible. Peer reviewers offered suggested discount rate values ranging from 0% to 7.9%.

Regarding other methodological considerations, reviewers tended to agree that EPA’s snapshot approach was preferable to a dynamic, year-by-year approach. Some said that the year-by-year approach would significantly increase the complexity of the method, with questionable added clarity.

GHG emissions from foreign crop production. Participating in this review were Dr. Elizabeth W. Boyer, Pennsylvania State University; Dr. Kenneth G. Cassman, University of Nebraska; Dr. John R. Freney, Commonwealth Scientific and Industrial Research Organisation (CSIRO); and Dr. Arvin R. Mosier, USDA/Agricultural Research Service.

Overall, the reviewers found the methodologies used (for fertilizer and pesticides; N2O emissions; agricultural energy use; and CH4 emissions from rice) to be generally acceptable and a “good first approximation” of changes in GHG emissions, with “exceptions that can be easily upgraded.”

All four reviewers had a variety of suggestions for ways that the data used in the analysis could and should be improved. In particular, numerous criticisms and suggestions were aimed at the fertilizer use data. Pesticide use data were also seen as problematic, but the results of the analysis are seen (at least by one reviewer) to have low sensitivity to the pesticide data, so attention should be focused on improving the fertilizer use data.

Model linkage. The Model Linkages Analysis peer review specifically solicited feedback on the use of multiple models and data sources, specifically in regards to land-use impacts; use of models for each component of the analysis, particularly the agricultural, petroleum, and energy sectors; and the use of the results of the models together, particularly in regards to the FASOM and FAPRI models, upstream greenhouse gas (GHG) emission factors, electricity production modeling, and fuel and feedstock transport.

Participating in this review were Dr. Martin Banse, Agricultural Economics Research Institute; Mr. Timothy Searchinger, Princeton University; Mr. John Sheehan, University of Minnesota; Dr. Michael Wang, Argonne National Laboratory.

The bulk of the reviewer comments focused on the following issues:

  • Comparison of partial equilibrium models with general equilibrium models. The reviewers generally agreed that EPA’s approach of linking partial equilibrium models was preferable to using a general equilibrium model such as the GTAP (Global Trade Analysis Project) model, especially given the fact that no existing model comprehensively simulates the direct and indirect effects of biofuel production both domestically and internationally.

    However, the reviewers each emphasized that partial equilibrium models, such as the FASOM (Forest and Agricultural Sector Optimization Model) and FAPRI (Food and Agricultural Policy Research Institute) models, have both positive and negative qualities.

  • Identification of problem areas in current modeling approach. The reviewers identified a number of problematic areas in the analysis, including:

    • Proper incorporation of spatial data into the analysis
    • Inclusion of all relevant factors into analysis, such as energy market information, and social, political and technological factors
    • Inconsistencies surrounding the linkage between FASOM and FAPRI
    • Integration of emissions factors used in GREET (Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation), FASOM, and FAPRI
    • Concerns with transparency of existing analysis
    • Lack of forestry sector in analysis
    • Concerns with FASOM

  • Identification of issues with the existing integration of FASOM and FAPRI models. All four peer reviewers detailed specific issues with the integration between the FASOM and FAPRI models.

  • Disagreement over whether to increase detail of the model. The reviewers disagreed over whether incorporating additional, potentially relevant factors into the model would increase the accuracy of the analysis.

  • Suggestions for the improvement of models and model linkages. Each of the reviewers proposed changes to the current modeling approach. Although the reviewers suggested different approaches, several reviewers recommended incorporating additional models into the analysis.

    • Searchinger suggested an approach which would rely on multiple models at each stage of the analysis. He suggested examining a range of models in order to develop a meta-analysis of the plausibility of different categories of predictions. He also detailed two additional approaches based on opportunities costs and scenario-based modeling analyses.
    • Banse also recommended the inclusion of new models into the existing analysis, but suggested adding new models as sources for additional feedback to the FASOM and FAPRI models.
    • Sheehan suggested a third approach, outlining a system dynamics framework of land-use changes using STELLA, although he stipulated that the system dynamics model in its current form would be too simplistic for use in this policy analysis.
    • Wang suggested that the forestry sector be included in the analysis, since the lack of a forestry consideration might underestimate the extent of the United State’s ability to domestically absorb land demand resulting from US biofuel production.

In addition, Wang and Sheehan both considered the 2005 baseline stipulated by EISA 2007 to be inappropriate. Wang added that the baseline potentially underestimates GHG emissions of petroleum fuels since he predicts that petroleum fuels will come increasingly from unconventional crudes and that global petroleum demand growth over time could generate unanticipated indirect effects in the petroleum sector.




It's interesting that the EPA is so focused on the utilization of liquid biofuels, that they never published a lifecycle greenhouse gas analysis for compressed domestic natural gas and its biofuel analogue, (i.e., Compressed Biogas, and SNG from biomass. Had they done so, I suspect that compressed biogas and SNG from crop and other waste streams would have shown an >80% reduction in greenhouse gas emissions relative to diesel and gasoline, and little or no indirect land use impacts. These gaseous fuels would also show lower emissions from fuel logistics and reduced traffic congestion related to the absence of distribution by Tankers.


Since there are 200 million vehicles on the road and only about 200,000 of them are powered by natural gas, I would guess that they went for liquid fuels as the obvious first choice for study.

Aureon Kwolek

Anybody can do the same thing. Just make up an assumption and then pay 20 scientists to design your model, such that the assumption is completely supported by the data. That’s not scientific proof. Indirect land use change is Garbage in, Garbage out - a theory based on false assumptions and false information. Their computer modeling is a farce, because it misrepresents the specific, factual information on the ground.

The truth is, indirect land use change theory is part of an agenda to limit and restrict first generation biofuels – cleaner alternative fuels that are chipping away at imported oil. This peer review group is laced with biased individuals. See “RFA: EPA Stacks Deck Against Ethanol with Agenda-Oriented RFS Peer Reviewers” Biofuel Journal:

According to this report, Timothy Searchinger, environmental Lawyer and Lobbyist, and Dr. Joseph Fargione, who sat on the peer review, are political activists and first generation biofuel critics. They are both “ethanol opponents with clear conflicts of interest...Among them are two researchers who were co-authors on Searchinger’s controversial and discredited 2008 Science paper on ILUC; staffers from two environmental activist groups; and several academics with an ideological axe to grind against production agriculture and contemporary biofuels.”

Renewable Fuels Association President, Bob Dinneen said: “This is a perversion of what the peer review process is supposed to achieve.”


"perversion?" These guys make peer-review equivalent to handing a paper to the Three Stooges. Farcical. These computer models are about as prescient as a Nintendo machine.

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