Wood heat rises again

One concern this winter is that people may decide to fire up an old wood-burning stove. “We’re still getting calls from people who have these 30-year-old [wood stoves] that their uncle gave them,” says Bob Christensen, the owner of En-R-Gy Saver Inc. in Holliston, Mass., which sells six brands of wood and pellet stoves. His stove sales are up about 50 percent this year over last.

The poster child of wood-heat pollution is the outdoor boiler, a wood furnace located in a separate outbuilding that sends hot water through underground pipes to a home or business. Outdoor wood boilers can emit 206 times more pollution than an oil furnace, or about 3,000 to 5,000 times more than a natural gas furnace, Rector says. They are often a source of complaints from neighbors who don’t appreciate being bathed in smoke.

Maine, New Hampshire, and Vermont have moved to set emissions standards on outdoor boilers. Manufacturers are getting the message, says Deidra Darsa, a spokeswoman for HPBA. “They have done an incredible job in turning their products around in the last year or so and come up with some very clean-burning products,” she says. The EPA is also engaged with outdoor boiler manufacturers to set up new emissions guidelines.

Because of its pollutants, wood-burning in general is most appropriate “at the urban fringe and beyond,” not in cities, which are already dealing with many other sources of air pollution, says John Gulland, cofounder of woodheat.org, a nonprofit website that aims to offer impartial information about firewood and wood-burning stoves.

Just like oil and gas, wood gives off carbon dioxide and other greenhouse gases when burned. But it also offers some carbon-saving benefits that make judging its effects on global warming difficult.

“I like to call it ‘75 percent carbon neutral,’ ” Mr. Gulland says. While wood burning does release carbon dioxide and methane, advocates argue that the trees would do that anyway in the forest as they die, fall over, and decompose.

But only a portion of the CO2 from decomposition enters the atmosphere. Some remains in the soil. Meanwhile, forests absorb carbon dioxide, so maintaining forested areas that are harvested for wood is a carbon plus. And if the wood being burned is scrap from a sawmill, for example, then no additional trees are being felled and no additional carbon created.

The question can quickly get knotty.

“On a scale of carbon neutrality, it’s better than burning a fossil fuel, but it’s not the same as wind or solar,” Rector says. “It’s a very complicated question,” she says. “We still need to let the scientists figure it out.”

How to burn wood more cleanly

The Environmental Protection Agency (EPA) has these recommendations for people who burn wood:

• Use a properly installed and vented EPA-certified wood stove.

• Season wood outdoors through the summer and for at least six months. Properly seasoned wood is darker, has cracks in the end grain, and sounds hollow when smacked against another piece of wood.

• Store wood outdoors, stacked neatly off the ground with the top covered.

• Use clean newspaper and dry kindling to start fires.

• Have the wood stove cleaned and inspected annually.

• Don’t burn household trash or cardboard. Plastics and colored inks on magazines, boxes, and wrappers give off toxic chemicals when burned.

• Never burn coated, painted, or pressure-treated wood, as it also releases toxic chemicals.

• Never burn ocean driftwood, plywood, particle board, or any wood with glue on or in it. They all release harmful chemicals when burned.

• Never burn wet, rotted, diseased, or moldy wood.

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