Study: Impact of bioenergy crops on climate change underestimated

The Washington Post
By Juliet Eilperin
Washington Post Staff Writer
Thursday, October 22, 2009; 3:37 PM

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 new paper published Thursday in the journal Science.

While 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 current 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 in the first place.

"We made an honest mistake within the scientific framing of the debate, and we've got to correct it to make it right," said Steven P. Hamburg, chief scientist at the Environmental Defense Fund, and one of the paper's authors.

The discrepancy stems from the fact that government officials in the U.S., Europe and elsewhere, when calculating the greenhouse gas emissions limit, do not count the carbon that biofuels release when they're burned. They've also established a legal system that limits emissions from energy use but not from land use activities such as clearing a forest. Since carbon is released when a producer clears and burns trees, even to grow a crop destined for the biofuels market, this math doesn't add up.

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