Wood for Biofuel: Not So Green?

June 11, 2013

Woody biomass, which accounts for roughly 75% of global biofuel production, may affect carbon emissions to a greater degree than previously believed.

A new study led by Dartmouth College shows that deep (mineral) soil, which stores more than 50% of the carbon in forest soils, may contribute more to increases in atmospheric carbon dioxide than researchers previously thought.

"Our paper suggests that increased reliance on wood may have the unintended effect of increasing the transfer of carbon from the mineral soil to the atmosphere,” says Andrew Friedland, a Dartmouth professor and co-author of the study. “So the intended goal of reducing carbon in the atmosphere may not be met."

Atmospheric studies don’t usually consider carbon stored in deep soil because it was believed to remain unaffected by timber harvesting. Carbon responses vary depending on harvesting intensity, surface disturbance, and soil type, but the new findings certainly indicate that such analysis must include a consideration of forest carbon cycles, researchers say.

The results appear in the journal Global Change Biology-Bioenergy.