Depending upon the assumptions and boundary conditions set in the ILUC evaluation, the result can dramatically increase the calculated GHG footprint of a biofuel, far offsetting the presumed greenhouse gas benefits of its use. (Earlier post.)

The challenge is that the ability to calculate future indirect land use changes resulting from production of biofuels is limited by the lack of both proven and accepted land use models and sufficient information about input data. For example, future land use policies may well be major factors in determining future land use changes, and yet adequate information and approaches for calculating the effects of such as-yet-unknown policies aren’t available. (Earlier post.)

The 12 senators sent a letter to EPA Administrator Jackson recommending that EPA refrain from including calculations of the effects of indirect land use changes in their rulemaking at this time. In November 2008, several of the group had also sent a letter to then-Administrator Johnson recommending the same thing. This letter repeats that recommendation and expands on its basis.

We understand that EPA has developed a methodology for calculating the indirect land use change components of the life-cycle GHG emissions for various biofuels and intends to include results of that methodology in its proposed rulemaking for the RFS-2. We also understand that, according to EPA’s methodology, the ILUC components contribute substantially to the life-cycle GHG emissions for several biofuels, including corn ethanol, sugarcane-based ethanol, and soy-based biodiesel. Indeed, according to EPA’s current ILUC calculations, existing soy-based biodiesel production may not count towards the biodiesel mandate in RFS-2.

EPA acknowledges that quantification of the ILUC components of life-cycle GHG emissions for biofuels is very difficult at this time. Many factors drive land use changes. Quantifying land use changes resulting from biofuels production needs to take into account these other factors, such as population growth, economic growth that drives demand for land-based food, feed and fiber production, urbanization, extracting lumber or mineral resources, and, of course, the very different and rapidly evolving land use policies of the United States and other nations. Not only are the land use impacts of these factors difficult to quantify; there is considerable uncertainty about predicting their future magnitude and effects. There also is an unresolved debate about how present and future GHG emissions should be compared, specifically whether a discount rate should be applied to future GHG emissions, and if so, what might be an appropriate discount rate for future GHG emissions.

An additional complication for the EPA methodology is that it cannot foresee or model future land use restrictions that might result from future national or international agreements or policies. Because land use changes such as deforestation can result in very large GHG emissions, it is possible that future domestic and international climate change policies will include major provisions restricting land use changes. Indeed, that may be the most appropriate and effective way to reduce GHG emissions associated with land use changes. At the same time, these land use restrictions in future international climate change policies are a major factor whose effects cannot be quantified until they are adopted. And yet, ignoring them introduces a major uncertainty into quantifying the ILUC components of life-cycle GHG emission calculations for biofuels today.

Given the complexity and uncertainty of this issue as well as what we believe are basic analytical limitations, we urge EPA to refrain from including any calculations of the ILUC components in determining life-cycle GHG emissions for biofuels at this time. The premature publication and use of inaccurate or incomplete data could compromise the ability to formulate a sound approach to implementing this life cycle GHG emissions requirement in the future. And the resultant rulemaking confusion could seriously harm our US biofuels growth strategy by introducing uncertainty and discouraging future investments. Instead, EPA should move forward in a manner that allows for public review and refinement of the methodology that is ultimately used to calculate the contributions to GHG emissions associated with ILUC.

—Letter to the EPA

Senators signing the letter were: Tom Harkin (D-IA); Charles Grassley (R-IA); Kit Bond (R-MO); Sam Brownback (R-KS); Bob Corker (R-TN); Kent Conrad (D-ND); Tim Johnson (D-SD); Claire McCaskill (D-MO); Ben Nelson (D-NE); Pat Roberts (R-KS); Jon Tester (D-MT); and John Thune (R-SD).