Selected Citation

10446

Biofuels, Land Use Change, and Greenhouse Gas Emissions: Some Unexplored Variables

Kim, H.; Kim, S; Dale, B.E.

Phillips Academy Andover, Andover, Massachusetts; Michigan State University, East Lansing, Michigan; Michigan State University, East Lansing, Michigan

01/01/2009

2009

Environmental Science & Technology

43

3

961-967

6

JOURNAL ARTICLE

American Chemical Society, Washington, D.C.

Greenhouse gas release from land use change (the so-called “carbon debt”) has been identified as a potentially significant contributor to the environmental profile of biofuels. The time required for biofuels to overcome this carbon debt due to land use change and begin providing cumulative greenhouse gas benefits is referred to as the “payback period” and has been estimated to be 100−1000 years depending on the specific ecosystem involved in the land use change event. Two mechanisms for land use change exist: “direct” land use change, in which the land use change occurs as part of a specific supply chain for a specific biofuel production facility, and “indirect” land use change, in which market forces act to produce land use change in land that is not part of a specific biofuel supply chain, including, for example, hypothetical land use change on another continent. Existing land use change studies did not consider many of the potentially important variables that might affect the greenhouse gas emissions of biofuels. We examine here several variables that have not yet been addressed in land use change studies. Our analysis shows that cropping management is a key factor in estimating greenhouse gas emissions associated with land use change. Sustainable cropping management practices (no-till and no-till plus cover crops) reduce the payback period to 3 years for the grassland conversion case and to 14 years for the forest conversion case. It is significant that no-till and cover crop practices also yield higher soil organic carbon (SOC) levels in corn fields derived from former grasslands or forests than the SOC levels that result if these grasslands or forests are allowed to continue undisturbed. The United States currently does not hold any of its domestic industries responsible for its greenhouse gas emissions. Thus the greenhouse gas standards established for renewable fuels such as corn ethanol in the Energy Independence and Security Act (EISA) of 2007 set a

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