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New Studies Support Cellulosic Ethanol

February 19, 2009
A team of researchers led by Jason Hill and David Tilman at the University of Minnesota have published an interesting assessment of the health costs of both greenhouse gas and fine particulate matter from corn ethanol, gasoline and cellulosic ethanol. The study is available in the Proceedings of the National Academy of Sciences early release for Feb. 10. The conclusion is favorable to cellulosic ethanol:

The benefits of shifting from gasoline and the current generation of food- and feed-based biofuels to next-generation cellulosic biofuels are approximately twice as large as previously thought, as long as the carbon debt from land-use change is minimal. Other environmental advantages of properly produced cellulosic biofuels (e.g., lower emissions of ozone precursors and reduced pesticide and nitrate loading of surface and groundwater) may make the economic benefits to society of this transition greater still."

What is most interesting is the authors' identification of the need to move beyond consideration of greenhouse gas emissions alone to include other forms of pollution and to consider the differences in regional impacts of each fuel pathway:

The debate over whether substituting biofuels for fossil fuels benefits or harms the environment needs to be expanded beyond GHG emissions to include a broad array of environmental quality dimensions."

The authors combine a calculation of the social costs of carbon with regional cost/benefit calculations of particulate matter pollution derived from an EPA map of environmental benefits. They note however that there is still lack of consensus on how to value health benefits from greenhouse gas reductions, and that considerable variance occurs through use of differing discount rates for the phenomenon. The variance does not affect their analysis, though, since the same calculation is applied to each pathway equally.

Another new analysis was presented at the AAAS annual meeting by Holly K. Gibbs of Stanford University. Gibbs analyzed United Nations Food and Agricultural Organization (FAO) satellite images collected between 1980 and 2000 to measure agricultural expansion throughout the entire tropical region.

Gibbs found that the area of cropland dedicated to soybean production in Brazil increased at a rate of nearly 15 percent per year since 1990, and Indonesia's oil palm production tripled during the 1990s and then doubled again from 2000 to 2007. She also notes that both Brazil and Indonesia contain significant areas of degraded land—in Brazil, the total area may be as large as California—that could be replanted with crops, thereby decreasing the burden on forested land. To prevent increases of biofuel production from causing expansion of cropland into forest, according to Gibbs, requires "new policies or economic incentives to encourage establishing crops on these lands. Government subsidies, environmental certification schemes or carbon markets could provide incentives to grow crops on degraded rather than forest lands."