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Tuesday, June 18, 2013

Carbon released from soil by logging means wood is less 'green' as a fuel, says Dartmouth prof

There has long been debate about whether burning wood for power (heat or electricity) is carbon-neutral. Burning trees adds carbon to the air, just like burning oil/coal, but replacement trees suck carbon back out of the air as they grow - and you can't do that with fossil fuels. Thus, in the long term, biomass is carbon-neutral.

Or so I've always thought.

But a new study from a Dartmouth professor adds this wrinkle: The process of logging also releases carbon stored more than a foot down in the soil. From the story in Dartmouth Now: "The prevailing opinion is that this carbon stays locked in the mineral soil indefinitely. However, (Prof. Andrew) Friedland contends that when the surface soil is disturbed, organic acids or microorganisms migrate downward and prime the release of carbon from the deep mineral soil."

Data from New Hampshire studies and work done around the world indicates that this could be a serious problem as we try to cut power-related carbon releases, says the paper. "If these additional fluxes are widespread in forests, recommendations for increased reliance on forest biomass may need to be reevaluated," says the abstract of the paper.

The takeaway isn't that burning wood is bad, however, only that it needs to be approached carefully. For example, many advocate managed plantations of willow, a fast-growing tree, as a continuing fuel source: New York State is pushing a 1,200-acre plantation with grants (see report here from FierceEnergy, (BROKEN LINK HAS BEEN FIXED) which despite the goofy name is quite a good news source.)