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How to Measure Land Use Change

September 5, 2008
Both the U.S. EPA and California’s Air Resources Board are currently considering how and whether to incorporate the indirect effects of U.S. biofuels production on carbon emissions from land use change in other parts of the world. The Renewable Fuel Standard passed by Congress in December 2007 requires inclusion of “significant emissions from land use changes” as part of the life cycle analysis of carbon emissions from biofuels. The Low Carbon Fuel Standard adopted by California also requires a life cycle analysis for fuels.

The issue of “indirect land use change” emissions was introduced early this year with the publication of papers in SciencExpress (see earlier post). Debate since the publication of those papers has focused on the lack of data to accompany the models and the assumptions inherent in the models. For instance, Searchinger and Fargione assumed that other countries would have to develop new cropland, primarily from sensitive ecosystems such as the rainforest, to replace the crops being used for biofuels in the United States. In a recent working paper, Roman Keeney and Thomas Hertel of Purdue University look at the possibility that increased crop yields would replace some of the crops being used for biofuels in the United States. They conclude that up to 30 percent of demand could be met through yield increases. Further, they show that Canada and Brazil – as the major grain trading partners for the United States – would be the countries to look at for any indirect land use change caused by U.S. biofuel production.

Keeney and Hertel do not calculate the impact that yield increases might also have in in Canada and Brazil, helping to meet demand. However, researchers at the University of Wisconsin do examine that possibility. Still, according to these researchers, the shift of land use does increase emissions and in the near term, demand is most likely to be met through expansion of land rather than increases in yield.

A group of researchers recently wrote to the California Air Resources Board, saying that until the uncertainties in the “indirect land use change” models had been thoroughly studied, they should not be calculated in the life cycle analysis required for biofuel producers in California. Other researchers responded that the effect certainly exists, so some calculation of it must be included under the law. They say that most calculations estimate that indirect land use change will double the greenhouse gas emissions attributable to biofuels.

The debate should not be whether land use change and cutting of rainforests releases carbon -- it does. It should be whether indirect land use change can be reliably attributed to individual biofuel producers. Bruce Dale of Michigan State University put it this way during a field hearing of the Senate Agriculture Committee in Omaha, Neb., on Aug. 18:
It seems to me that making U.S. farmers responsible for land use decisions made by others is both unfair and a terrible precedent. Are we going to make every U.S. industry responsible for greenhouse gas generation by its competitors around the world?"

In other words, there are many factors that lead to deforestation in Brazil. As Iowa State University professors Eugene Takle and Don Hofstrand put it, "The conversion of native ecosystems to agricultural production started well before the emergence of the biofuels demand."