Responses to Published Studies Regarding Concern about Impacts on Greenhouse Gas Emissions from Land Use Changes Resulting from Increased Biofuels Production and Usage
Two articles published in Science Magazine in February raised significant concerns about the viability about increased U.S. biofuels production, claiming that GHG emissions would rise dramatically due to direct and indirect land use changes needed to support the additional crop growth.
Responses to the arguments posed in the two studies have been released by many interested parties, both public and private, including the U.S. Department of Energy Office of Biomass, Argonne National Laboratory, National Renewable Energy Laboratory, Oak Ridge National Laboratory, Pacific Northwest National Laboratory, USDA, University of Michigan, the 25x’25 Alliance, among others.
The responses agree that some aspects of the articles were accurate, however significant errors, oversimplifications, or using inappropriate assumptions were made. The Searchinger study was the primary focus of the responses.
The various federal agencies responses included:
The study models 30 billion gallons of corn based ethanol production, which is double what is called for, and limited to, by the RFS. The amount was limited by Congress because of the awareness of the limitations of ethanol production from corn. The remaining amount of additional ethanol production comes from cellulosic processes using waste materials.
Corn acreage yields were assumed to be constant in the modeling. However, U.S. yields have increased annually at an average of 2%. In addition, corn yields worldwide have lagged behind the advances seen in the U.S., so has a larger percentage growth potential than in the U.S. to arrive at similar yields.
Land conversion estimates assume the worst case scenario using historical data worldwide including China and Brazil. Using this approach does not capture the improvements that have happened in these areas, such as the reforestation efforts in China and the legislation in Brazil that has slowed the deforestation.
The study assumes that corn exports will decline by 62%, disrupting the world food supply and leading to indirect land use changes. However, historical data shows that corn exports have remained relatively constant since the 1980’s, with a recent trend towards increasing exports (14% in 2007), even while the ethanol industry was undergoing significant growth.
One modeling scenario assumed that acreage use for corn would be changed over to switchgrass. On the contrary, no farmer would do this because corn has a higher value.
DOE reinforced that their commitment for developing environmentally sound biofuels. They are working with USDA, EPA, and others to evaluate more fully the direct and indirect land use issues, as well as the sustainability issues (such as water and fertilizer usage), the additional fuel production will create.
Dr. Bruce Dale with the University of Michigan points out that the studies describe themselves as lifecycle analyses (LCA), however the basic principles of LCA are not adhered to. An LCA is data driven, however these studies rely on estimates or economic model driven data that is not appropriate or accurate for performing an LCA, leading Dr. Dale to discredit the reports from even being considered as LCA. He also points out that the studies link all land use affects from increases in corn production to ethanol production. However this is not a correct argument since, for example, additional corn grown for animal feed cannot be linked to potential the environmental problems related to corn for ethanol production.
The 25x’25 Alliance notes that increases in food, feed, fiber, and energy can be met with a combination of next generation crop and fuel production technologies while decreasing the cost of farming inputs that will prevent the use of agriculturally sensitive lands for biofuel crops.
Original Study References:
- Searchinger, Timothy, et.al., “Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land Use Change” , Science, February 7, 2008.
- Fargione, Joseph, et.al., “Land Clearing and the Biofuel Carbon Debt”, Science, February 7, 2008.
Study Response References:
|
