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Fertilizer and emissions

Ethanol's Broken Promise: Fertilizer and emissions

May 29, 2014

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An accurate accounting of corn ethanol’s life cycle emissions must also include the impact of nitrous oxide (N2O), a greenhouse gas that is released from the fertilizers used to grow corn that has 298 times the global warming potential of carbon dioxide. More fertilizer is used on corn than on any other crop, an average of 138 pounds per acre. Nobel prize winning atmospheric chemist Paul Crutzen and colleagues found in a 2008 paper that nitrous oxide emissions from fertilizer could be up to five times greater than previous estimates, which assumed that on average 1 percent of fertilizer is emitted as nitrous oxide.27 Crutzen found the emissions to be as high as 3-to-5 percent, which would negate any potential greenhouse gas reductions from corn ethanol.28

The corn ethanol mandate has also led a lot of farmers to grow more corn and to switch from rotating corn and soybeans to continuous production of corn, which requires more than eight times more fertilizer than soybeans.