Biofuels, Land Use Change, and Greenhouse Gas Emissions: Some Unexplored Variables
- 6 January 2009
- journal article
- research article
- Published by American Chemical Society (ACS) in Environmental Science & Technology
- Vol. 43 (3), 961-967
- https://doi.org/10.1021/es802681k
Abstract
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 higher standard for that industry than for any other domestic industry. Holding domestic industries responsible for the environmental performance of their own supply chain, over which they may exert some control, is perhaps desirable (direct land use change in this case). However, holding domestic industries responsible for greenhouse gas emissions by their competitors worldwide through market forces (via indirect land use change in this case) is fraught with a host of ethical and pragmatic difficulties. Greenhouse gas emissions associated with indirect land use change depend strongly on assumptions regarding social and environmental responsibilities for actions taken, cropping management approaches, and time frames involved, among other issues.Keywords
This publication has 16 references indexed in Scilit:
- Life cycle assessment of corn grain and corn stover in the United StatesThe International Journal of Life Cycle Assessment, 2009
- Land Clearing and the Biofuel Carbon DebtScience, 2008
- Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use ChangeScience, 2008
- Greenhouse gas mitigation in agriculturePhilosophical Transactions Of The Royal Society B-Biological Sciences, 2007
- Current and Potential U.S. Corn Stover SuppliesAgronomy Journal, 2007
- Dynamics of Land-Use and Land-Cover Change in Tropical RegionsAnnual Review of Environment and Resources, 2003
- Resource assessment and removal analysis for corn stover and wheat straw in the Eastern and Midwestern United States—rainfall and wind-induced soil erosion methodologyBiomass and Bioenergy, 2002
- Proximate Causes and Underlying Driving Forces of Tropical DeforestationBioScience, 2002
- Potential environmental effects of corn (Zea mays L.) stover removal with emphasis on soil organic matter and erosionAgriculture, Ecosystems & Environment, 2002
- Management options for reducing CO2 emissions from agricultural soilsBiogeochemistry, 2000