Wood as energy source not as 'green' in carbon terms

Using wood for energy, thought to be cleaner than fossil fuels, could, in fact, lead to greater carbon emissions than estimated, a U.S. study found. The impact would come not from the burning of the wood but from large amounts of carbon released from deep forest soils as a result of disturbances such as logging, researchers at Dartmouth College reported Tuesday. Global atmospheric studies often don't consider carbon in deep soil because it has been thought to be stable and unaffected by timber harvesting, but the Dartmouth findings show clear-cutting and other intensive forest management practices can lead to emissions from such deep soils, said to store more than 50 percent of the carbon in forest soils. Calls for an increased reliance on forest biomass for energy production should be re-evaluated and forest carbon analyses are incomplete unless they include deep soil, also known as mineral soil, the researchers said. Woody biomass, which includes trees grown on plantations, managed natural forests and logging waste, makes up about 75 percent of global biofuel production. "Our paper suggests the carbon in the mineral soil may change more rapidly, and result in increases in atmospheric carbon dioxide, as a result of disturbances such as logging," Dartmouth Professor Andrew Friedland said. "Increased reliance on wood may have the unintended effect of increasing the transfer of carbon from the mineral soil to the atmosphere. "So the intended goal of reducing carbon in the atmosphere may not be met."