Pellet makers source wood from thousands of landowners who are often eager to generate income to offset property taxes. Enviva opened its first mill in Ahoskie, NC, in 2011, promising to make pellets mostly from scraps of wood such as tree tops, twigs and sawdust with no other market.

When land is cut down, the thick, straight logs usually go to a sawmill that produces things like two by four. Pellet makers take small chunks that may have no other market and vie with paper, cardboard, and diaper fluff makers for the rest. According to Consuelo Brandeis, a research ranger for the United States Forest Service, about 3 percent of the timber harvested from the south goes into pellets .

Several Enviva mills were soon processing material from logging and sawmills across the region. Environmental groups claim to have documented truckloads of tree trunks and whole trees, not just leftovers that end up in pellet mills. Publicly available pictures show logs stacked in mills, and a reporter outside the entrance to a pellet mill saw trucks pulling in with logs.

The pellet manufacturers’ pledges to rely on scrap wood “put them in a corner,” said Robert Abt, forest economist at North Carolina State University in Raleigh, because the wood industry was already using its supplies relatively efficiently and leaving little waste.

While longer pieces of wood that are too crooked or knotted for sawmills are part of Enviva’s offerings, Jennifer Jenkins, Enviva’s chief sustainability officer, has a PhD. Speaking of ecosystem ecology, the company said sourcing is sustainable because it only buys from landowners who are committed to tree regrowth and because the forests in the southeast are growing overall. Pellets from such regions should be classified as climate neutral under the accounting rules of the Intergovernmental Panel on Climate Change, a United Nations agency that provides scientific information on climate change, said Dr. Jenkins.

Dr. Jenkins said the company has installed air pollution controls that exceed requirements. A community relations manager said he had not received any noise complaints related to the Northampton County mill.

The US wood pellet industry, which exported more than seven million tons of pellets last year, has generated strong opinions in North Carolina.