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UK Study Highlights Uncertainty in Calculating Indirect Land Use Emissions

July 10, 2008
Britain’s Renewable Fuels Agency this week released the Gallagher Review, a report on the indirect effects of biofuels production that was prompted by the Searchinger and Fargione studies published in Science earlier this year. (See this blog’s earlier post on the forthcoming study.)

The summary of the conclusions of the Gallagher Review include some very telling comments:
Quantification of GHG emissions from indirect land-use change requires subjective assumptions and contains considerable uncertainty.
“Current lifecycle analyses of GHG-effects fail to take account of indirect land-use change and avoided land use from co-products.
“Mechanisms do not yet exist to accurately measure, or to avoid, the effects of indirect land-use change from biofuels.”

Where does the uncertainty identified by the Gallagher Review in the Searchinger and Fargione models come from? Factors include the complex global nature of agricultural markets, the potential for a variety of biofuel feedstocks, production of co-products from the same feedstocks, and the prices of commodities.

According to the Gallagher Review, the model proposed by Searchinger cannot accurately predict future demand for commodities and how global markets will respond. The review notes that agricultural production of food and feed was already shifting from America and Europe to other parts of the world. U.S. and EU biofuel policies were a response to this shift intended to provide new markets for agricultural production.

Searchinger’s model also does not account for future productivity or increases in yield –- he assumes there will be no increase in yield. The model similarly does not take into account increases in productivity from biofuel production technology.

Further, Searchinger does not accurately account for uncertainties in the amount of greenhouse gas emissions that occur from land-use change. Professor Bruce Dale of Michigan State University has previously noted the difficulty in assessing emissions from land-use change. BIO’s 2006 study on Achieving Sustainable Production of Agricultural Biomass shows that adoption of no-till agriculture, which has been increasing, can reduce greenhouse gas emissions and even store additional carbon in soil, a fact that the Gallagher Review makes note of.

As a result, the Gallagher review disputes Searchinger’s calculation of a 167-year carbon debt for U.S. ethanol production, stating, “This review has been unable to definitively assess the accuracy of the Searchinger calculation for the GHG emissions arising from US maize ethanol.”

The studies conclusion for future policy is that biofuels have the potential to reduce greenhouse gas emissions and that policy should encourage innovation and new technologies that increase that potential.