A matter of wood source Ideally, pellet mills use wood that comes from dead trees and the leftover branches and sawdust from other lumber operations. But environmentalists say some companies use mature hardwoods to make fuel, putting any environmental benefits in doubt. Scientists say wood can be a greener alternative to coal if pellets are made from waste timber or from well-managed pine plantations. But the expansion of pine plantations can eventually threaten native species that rely on natural forest habitats for food and shelter. PELLET MILLS Processing trees into pellets Logs are stripped of their bark, which is burned to fuel achip dryer. Wood passes through a chipper, a dryer anda grinder before the pulverized wood reaches a pelletmill. Pellets are cooled, stored, transported and shippedto power plants in Europe. Environmental impact Methods used by some wood-pellet producers can yieldas much as four times the carbon dioxide as burningcoal, studies show. Hardwoods are slow to regenerate, and it can take decades for new trees to reabsorb the greenhouse gases emitted when the wood is burned. Debarker Harvester Chipper Dryer Pelletmill Cooler Transport Power plant Shipping Greenhouse gases released: Kilograms of CO2 equivalent per megawatt-hour of electricity 3,000 2,000 1,000 –1,000 –2,000 0 4,000 Coal Coal Coal Natural gas Natural gas Natural gas Existing pine plantations Existing pine plantations Existing pine plantations managed more intensively;35% greater yield, harvested every 25 years Existing pine plantations managed more intensively;35% greater yield, harvested every 25 years Increased harvest of natural forests Increased harvest of natural forests ORIGIN OF FUEL ORIGIN OF FUEL Dead trees from natural disturbances Ga. Ala. Miss. S.C. Fla. N.C. Va. Enviva plant in Ahoskie, N.C., makes wood pellets mostly from hardwood timber sold to the company by private landowners. Some uncertainty exists about how much greenhouse gas would be released by using natural forests as fuel, but in all scenarios, the CO2 created would for decades be much more than that from fossil fuels. Georgia Biomass plant in Waycross, Ga., obtains most of its wood from pine plantations. PORT FACILITIESEuropean demand for wood pellets supports two dedicated port facilities: Enviva’s, in Chesapeake, Va., and a Georgia Biomass port in Savannah, Ga. Enviva recently disclosed plans to build a second terminal at the port of Wilmington, N.C. Drawings are diagramatic Method makes the difference

SOURCE: British Department of Energy and Climate Change, National Wildlife Federation, Southern Environmental Law Center.