When it comes to biofuel production, nitrous oxide emissions are no laughing matter. So says Nobel prize-winning chemist Paul Crutzen, who just wrapped up a new study showing that the overall effect of growing and burning most biofuel crops may be to raise, rather than lower, greenhouse gas emissions. Indeed, several of the most commonly used biofuel crops may release as much as twice the amount of nitrous oxide (i.e. laughing gas) gas - a GHG several hundred times more potent than carbon dioxide - as previously thought.
Therefore, Crutzen and his colleagues conclude, using biofuel could wipe out any benefits gained from not consuming fossil fuels and, more worryingly, could further contribute to global warming intensification. "The significance of it is that the supposed benefits of biofuels are even more disputable than had been thought hitherto. What we are saying is that [growing many biofuels] is probably of no benefit and in fact is actually making the climate issue worse," said Keith Smith, the study's co-author and a professor of atmospheric science at the University of Edinburgh.The study determined that bacteria convert much more of the nitrogen in fertilizer to nitrous oxide than previously estimated - as much as 3-5%, or twice the heretofore largely accepted value of 2% used by the IPCC to assess the impact of fertilizers on global warming. The authors found that the warming due to nitrous oxide emissions often overtook the cooling effect achieved due to saved fossil fuel carbon emissions - 1 to 1.7 times larger for rapeseed biodiesel, which accounts for 80% of biofuel production in Europe, and 0.9 to 1.5 times larger for corn ethanol, the dominant biofuel in the U.S.
Out of all of the biofuel crops assessed, only cane sugar ethanol proved viable as a real alternative to fossil fuels - with a relative warming of 0.5 to 0.9. So, again, the picture is mixed: though biofuels won't offer us the magic bullet needed to solve our fossil fuel-related woes, more work and research needs to be done before we fully embrace these alternatives.