HARLEYVILLE - Wood stoves smoke. Anyone who's fired one up knows that. So the question isn't whether the wood-burning power plants pollute. They do. The question is whether they are the lesser of two evils:

Is it environmentally more responsible to burn wood, a renewable energy source and carbon absorber, than carbon fuels such as coal?

A modest wood-burning power plant is getting underway in Harleyville, back on a country road, firing up waste wood to create electricity that will be bought by the Santee Cooper utility. That electricity otherwise might come from one of the utility's much larger and more polluting coal-fired power plants.

Because the EDF Renewable Energy operation in Harleyville is a "biomass" plant - one of the hot new "clean energy" businesses - it has been given public-money subsidies and fewer restrictions on the pollution it emits. But an environmental group's report last week claimed that wood-burning plants pollute more than the coal plants, compared by the amount of electricity produced, and should be held to the same restrictions.

The controversy is flaring now because the Environmental Protection Agency is scheduled this summer to reconsider toughening restrictions on the wood-burning plants. The second look comes on the heels of the EPA's controversial proposal to strictly limit how much pollution a household wood stove can emit.

The agency in 2010 put off the decision on the plants. The report is an early broadside trying to force the hand of federal regulators.

The EPA is in a tough spot: The biomass industry is taking off and has wide political support. The Partnership for Policy Integrity, which issued the report, is the latest of a number environmental groups that at one point or another have questioned the looser controls on biomass, although many of the groups support biomass power to a degree.

Carbon neutral?

Wood-burning plants essentially are big stoves that burn wood waste to create electricity the way a household stove does to create heat.

With the subsidies and the break on restrictions, the industry is in a modest boom, and now has more than 9,600 facilities operating.

The Partnership for Policy Integrity was formed in 2010 by veteran issue advocates, about the same time as the industry came into its own. Its report is damning.

"Although wood-burning power plants are often promoted as being good for the climate and carbon neutral, the low efficiency of plants means that they emit almost 50 percent more carbon dioxide than coal per unit of energy produced," said Mary Booth, partnership director.

The industry has hit back hard, calling the report an 81-page editorial that has not been peer reviewed or supported by other environmental groups.

"It showcases a fundamental misunderstanding of the science surrounding forestry and biomass, and a lack of familiarity with the state and federal laws governing energy and the environment," said Carrie Annand, Biomass Power Association external affairs vice president.

Annand didn't directly contradict Booth's contention that the plants pollute more if compared by the amount of energy produced. But she argued that wood-burning plants aren't as big and so don't produce nearly so much pollution as the coal plants, and "creating unnecessary permitting hurdles for small facilities discourages investment and job creation," she said. And the plants have offsetting benefits that coal doesn't.

Cost and benefit

The idea is pretty simple: Wood-burning plants are said to be "carbon neutral" because they rely on a renewable product that absorbs carbon dioxide - trees. And decaying wood returns carbon dioxide to the air whether or not the wood is burned. Equipment at the plant captures other pollutants and the plant does not burn treated or painted wood.

"Biomass cannot be compared to coal as coal plants release carbon that is trapped underground," increasing greenhouse gases in the atmosphere, said Sandi Briner, the EDF communications director. "The (wood-burning) carbon dioxide emissions were already offset as the trees grew."

Booth doesn't buy it. The industry has not produced documentation that the full amount of carbon dioxide released actually is offset, she said. Not enough of other pollutants are captured at the plants, and emissions are not restricted during start-up or shutdown - when they are at their worst, she said.

"How can something that emits more carbon dioxide than fossil fuels be carbon neutral? Sure, the material would decompose over time and emit carbon dioxide if it weren't burned, but even decomposition doesn't happen instantly," Booth said. The Harleyville plant is not a small plant, she said. "They will burn 300,000 tons of wood a year. That will require an average of 37 tractor-trailer loads of chips per day, every day, to fuel the plant."

EPA is caught in the crossfire.

With nearly 10,000 wood-burning plants now operating up across the country, the investment and employment is sizeable. The $45 million Harleyville plant is one of two EDF operates in the state so far. It provided employer-scarce upper Dorchester County with 200 jobs.

S.C. regulators largely have followed the federal limits so far.

"Ultimately, EPA will have to make a decision as to whether more regulation is needed," said Mark Plowden, spokesman for the S.C. Department of Health and Environmental Control.

Reach Bo Petersen at 937-5744, @bopete on twitter or Bo Petersen Reporting on Facebook.