New research finds that the amount of "land use emissions" from corn-based ethanol is less than half of the figure used as the basis for California's low carbon fuel standard (LCFS). The new report from Purdue University is an update to its Global Trade Analysis Project (GTAP) model, the model used by the California Air Resources Board to form the LCFS.
The GTAP model was updated in several ways, including to update the global economic database from 2001 to 2006 figures, expanding the amount and types of land included in the analysis, increasing the value of ethanol's co-product distillers grain as an animal feed, assuming a conservative increase in crop yields, and changing assumptions about how and when carbon is released from harvested trees.
The result: average "land use emissions" from corn ethanol are 13.9 grams CO2-equivalent per megajoule (g/MJ) instead of the 30 g/MJ used by California for the LCFS. This is a pretty significant difference.
Wallace Tyner of Purdue, lead author on the study, was quoted by Hoosier Ag Today as saying, "...the original work was sort of a first cut, and we needed to take a more thorough, careful look with new data, new modeling approaches, and model parameters."
What does all this mean? It means the California Air Resources Board needs to take a look at this new information and update their modeling to include this better data. It also means that the science of "indirect land use change" is still very new and full of uncertainties. Even the Purdue researchers state in the report that "... one cannot escape the conclusion that modeling land use change is quite uncertain." It means much more research is needed on "indirect land use change" before policies should use it as a basis for far-reaching decisions.
And there's still the question of why CARB is choosing to selectively apply indirect land use charges only to biofuels and not to petroleum. A blog post for another day...
Read the full report, "Land Use Changes and Consequent CO2 Emissions Due to U.S. Corn Ethanol Production: A Comprehensive Analysis," by Tyner et al, April 2010.
Posted by: Kristin Brekke