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Carbon Release an Issue in Woody Biomass Use for Energy Production

February 9, 2012

The following story was written by a University of Missouri student as part of the 2011 Sonja Hillgren/Farm Journal Ag Journalism Field Reporting Institute. Learn more.

By Emily Garnett
Deep inside Pioneer Forest, which sprawls across 154,000 acres in central and southeastern Missouri, the roar of a chainsaw could be heard.


The roar stopped abruptly and in the brief silence that followed, Jay Duncan, co-owner of J&G Logging, hoisted his orange Stihl chainsaw and made a hasty dash away from the tree. With a prolonged cracking sound and an enormous crash, the branches, limbs and sizeable trunk of a mature scarlet oak hit the ground.


What Duncan heard was the death of a tree. What he couldn’t hear was the beginning of the slow, silent release of carbon into the atmosphere as the tree began its decaying process. If the dead scarlet oak is used as "woody biomass," a wood product burned for energy production, the carbon release will be even swifter.


Thanks to a study known as the "Manomet Report," the sound of trees releasing carbon into the atmosphere now rings loudly in the ears of many scientists and foresters. Even though the study’s conclusions could limit the size and impact of an imminent woody biomass industry, many foresters and environmentalists fear for the health and survival of Missourian forests.


The U.S. Department of Agriculture has long promoted using trees to produce energy, in the place of fossil fuels such as coal and natural gas. Fossil fuel supplies are replenished over millennia, but trees can be regrown within 30 years.


Because of this fast growth, the logic went, trees can rapidly reabsorb the carbon they release into the atmosphere when they’re burned, thus making wood a carbon-neutral source of energy.
"Up until very recently in the United States, woody biomass has gotten a free pass," said Peter Becker, a forest ecologist and research coordinator with the Eastern Ozarks Forestry Council.


But in June 2010, the Manomet Center for Conservation Sciences, a non-profit environmental research organization based in Massachusetts, released a study that refuted the long-standing belief that burning wood for energy is a carbon-neutral event.


"Forest biomass generally emits more greenhouse gases than fossil fuels per unit of energy produced," creating an initial "carbon debt" when wood products are first burned, the report concluded.


Tree regrowth will eventually remove this carbon from the atmosphere, but it can take up to 40 years before the full debt is repaid. So, only decades after the initial burning does biomass "begin yielding carbon dividends in the form of atmospheric greenhouse gas levels that are lower than would have occurred from the use of fossil fuels," the study concluded.


"When I read the report my mouth dropped open, literally," Becker said. "It has serious, serious implications."


In part due to the issues raised in the Manomet Report, the U.S. Environmental Protection Agency has revised a report proposal that will examine how a variety of energy sources, including wood, release greenhouse gases into the atmosphere.

The changes could limit how much wood is accessible for biomass facilities such as wood-generated power plants, said Kenneth Skog, a forest economist with the U.S. Forest Products Laboratory in Madison, Wis.

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