Interesting timing: this study (subscription only, except for the abstract), just published in the journal Science, may give a boost to the biofuels bill that’s currently working its way through the Washington legislature.
The study addressed itself to the issue of whether ethanol from corn really reduces greenhouse gas emissions—which has been an area of fairly intense interest among both supporters and skeptics of biofuels.
To me, it looks like the authors really did their homework, and have done their best to be conduct a fair analysis that takes the best points from all sides of the debate. Their final answer: compared with gasoline, filling your tank with corn ethanol reduces total GHG emissions by about 13 percent. Score a point for ethanol!
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As fair as the paper seems, it probably won’t end the controversy; David Pimentel, one of corn ethanol’s main detractors, has already dismissed the study as "another pro-ethanol paper".
And, as with everything, the devil’s in the details; and for a system as complicated as corn ethanol production there are a lot of details. For example—and pardon me if this is getting too geeky—I’m not sure whether the authors accounted for the 1 percent or so of nitrogen fertilizers that are applied to cornfields, but then get volatilized and released into the atmosphere as nitrous oxide. NO2 is a potent greenhouse gas, about 310 more powerful at trapping heat than carbon dioxide, so even small releases can make a difference. If the authors haven’t accounted for that, then the GHG gains of ethanol may be substantially lower than the paper suggests—perhaps a 3 percent improvement rather than 13 percent.
But one thing that the paper does make clear is that cellulosic ethanol—made from woody material or straw—at least has the potential to be lead to really substantial reductions in GHG emissions. If a modest biofuels bill can help jumpstart interest in cellulosic ethanol, it seems like it could be well worth the effort.