More than 150 wood pellet manufacturing mills operate across the U.S., many supplying the domestic woodstove pellet market with home heating fuel.
More than a quarter are industrial pellet mills, grinding thousands of acres of forest into biomass for overseas export to electrical utilities stoking retrofitted coal-fire furnaces with "densified" wood.
The largest mills, concentrated in the southeastern U.S., claim to sustainably harvest timber, from both hardwood and softwood forests. But a new mill, Highland Pellets in Pine Bluff, which harvests only fast-growing Southern softwood pine may be among the greenest.
Still, the calculated ecological costs and benefits of forest biomass remain hazy.