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CHARLOTTE, N.C. — As (NYSE: DUK) turns to cleaner-burning wood to help fuel some of its coal-fired power plants in North and South Carolina, some environmentalists worry that growing demand could damage local forests.

Using biomass to fuel power plants is in response to a 2007 law requiring utilities to get more of their energy from renewable sources and reduce the amount of greenhouse gas emissions associated with coal-burning plants.

Duke has asked the North Carolina Utilities Commission for permission to burn wood, including chips from cutting up whole trees, with coal at its Buck power plant in Rowan County and Lee plant in Williamston, S.C.

“It’s certainly our understanding that (the legislation) allows a broad and inclusive interpretation of woody biomass,” Duke spokesman Jason Walls told The Charlotte Observer for a story in Saturday editions. “A closer definition would allow greater clarity moving forward.”

The and other organizations have filed legal challenges to those plans, saying the company should be using waste wood and scraps – not whole trees.

“Where the legislation says ‘swine waste’ and ‘poultry waste,’ it doesn’t envision burning pigs and chickens,” said Derb Carter, director of the law center’s Carolinas office. “In the same sense, we don’t think ‘wood waste’ should be considered whole trees.”

The group also spoke out against the Obama Administration’s announcement last week to open some areas of the Atlantic coast to oil and gas exploration.

“Opening the South Atlantic Coast to oil and gas drilling will do nothing to address climate change, provide only about six months worth of oil, and put at risk multi-billion dollar tourism and fisheries industries. One oil spill could devastate a coast,” Carter said in a statement issued April 1.

“Instead, reducing our dependence on such old, polluting energy sources by bringing America’s innovative talent to bear on fully exploiting energy efficiency and clean renewable energy sources should be the first step in an energy policy that generates jobs and keeps America technologically competitive,” she added.

Without the ability to access whole trees, utilities will have a more difficult time reaching the 12.5 percent renewable energy standard by 2021 as the law requires, said economist Robert Abt, a forestry professor at North Carolina State University.

“I’m pretty confident in saying if we only allowed the use of residuals, then wood is not going to be a significant part of the portfolio,” Abt said.

But that worries environmentalists, especially in North Carolina where companies are not required to replant after harvesting trees. That means forests could be laid bare and open to erosion, damaging waterways and wildlife, Carter said.

“We’re going to have a game-changing demand on wood resources,” said Dickson Phillips III, a Chapel Hill lawyer who leads the Environmental Management Commission’s renewable energy committee. “It seemed like the appropriate time to make sure we don’t do something we’re going to regret.”

The staff of the North Carolina Utilities Commission has recommended that commissioners approve Duke’s request. The Southern Environmental Law Center, the Environmental Defense Fund and The North Carolina Sustainable Energy Association have asked for a hearing and for the request to be denied.