Vinod Khosla has a letter in the Oct. 17 issue of Science ($ub. req’d) critiquing the Searchinger et al study: “U.S. croplands for biofuels increases greenhouse gases through emissions from land-use change.”

Question: Why would the editors at Science publish a letter from someone who is not a biologist or a peer of the researchers being critiqued?

Answer: Searchinger et al were allowed to respond, and the response left a glowing crater where Khosla’s argument once stood. Here’s a sample:

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The plight of the Amazon is a matter of both forestry and agriculture. Typical logging removes a few trees per hectare, causes collateral damage, and facilitates conversion through road-building, but forests regrow carbon if the land is not subsequently converted to agriculture. Biofuels that use good cropland anywhere in the world raise crop and meat prices and help spur the actual conversion to pasture or cropland by increasing their net economic return.

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For cellulosic ethanol grown on corn land, our study found increased greenhouse gas emission, even with dramatically higher yields and conversion rates than now broadly attainable.

Yet even with major breakthroughs that double our assumed biomass yields, cellulosic ethanol grown on corn land would only reduce emissions compared with gasoline by 37% counting land-use change.

Even the latest hopeful DOE research plan in 2005 envisions 15 years of research and development before cellulosic production starts to scale up.

Although Khosla correctly points out that rising crop prices only modestly increase food prices in U.S. grocery stores, the poor around the world eat basic cereals and vegetable oil. Their prices worldwide rose 300 and 400% respectively, between 2000 and spring 2008. Nearly all analyses assign a major role to biofuels: Biofuels consumed the vast bulk of the world’s growth in cereals and vegetable oil between 2005 and 2007, requiring the world to deplete stocks to meet growing food demand.

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Sub-Saharan Africa already imports much of its food and has roughly 400 million hungry people [population of United States is 365 million] who together suffer 85% of the world’s calorie gap. Climate change could decrease yields by 50% in the region.

… Sub-Saharan Africa needs to use its good arable land for food even more than other regions.