The world's policymakers and scientists have made a critical error in how they count biofuels' contribution to human-generated greenhouse-gas emissions, according to a paper published on 22 October in the journal Science. Although the article addresses a wonkish subject -- how to measure the environmental impact of energy sources such as ethanol and wood chips, which absorb carbon as they grow but release it back into the atmosphere when they're burned -- it has broad implications. The method undercounts the global-warming contribution of some bioenergy crops, the team of 13 researchers wrote, because it doesn't factor in what sort of land-use changes might occur to produce them. When calculating the greenhouse-gas emissions limit, government officials in the United States, Europe and elsewhere do not count the carbon that biofuels release when they are burned. But carbon is released when a producer clears and burns trees, even to grow a crop destined for the biofuels market. Officials also established a legal system that limits emissions from energy use but not from land-use activities such as clearing forests.
http://www.washingtonpost.com/wp-dyn/content/article/2009/10/22/AR2009102202889.html