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Wood Stoves Clean Up Their Act

To avoid woodsmoke pollution, manufacturers develop technologies to burn hot and fast

By Eric C. EvartsStaff writer of The Christian Science Monitor / September 23, 1992


REINHART ROSS speaks in glowing terms about his new wood stove.

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"I fire it up once in the morning, then I don't have to do it again," he says.

Mr. Ross lives in a hilltop A-frame house he and his wife, Dorothy, built in Bellingham, Wash., in 1986. The house was designed to be heated efficiently by their wood stove, which sits in the corner of the cathedral-ceiling living room that faces a forest. He keeps the house at about 68 degrees "because any warmer than that, and people start getting tired," he says.

The clean-burning stove is a big improvement over his previous one, which "was state of the art for its time," he says. "The glass window in the door never gets dirty."

In addition to burning less wood and producing less smoke, new wood stoves accumulate less tarry, black creosote. Many stoves create airflow across their glass doors to prevent any buildup there.

"I'm convinced it makes a visible difference in chimney emissions," Ross says of his $1,200 Pacific Energy Super Series stove. "I can see [the difference] from the living room just by looking up out the windows."

The trees Ross cleared to build the house provided enough wood to heat the house for his first three years there, he says.

Like Ross, hundreds of thousands of homeowners in the United States bought wood stoves as the cost of energy rose through the 1970s and '80s. Wood was a popular way to provide heat while cutting back on oil, electricity, and natural gas consumption. But the resurgence of organic heating fuel brought days when burning wood was banned.

The bans have been so frequent in some areas, says John Kowalczyk, manager of air planning for the Oregon Department of Environmental Quality, that "they have actually pushed people away from wood heat" despite its low cost in rural areas.

Traditional wisdom says that the most efficient way to extract heat from wood is to let it smolder for hours, never letting too much air get to the fire so the wood won't burn too fast. But this kind of fire is the most polluting, says Will Peck of the Bow and Arrow Stove and Fireplace shop in Cambridge, Mass.

By comparison, today's clean-burning wood stoves are designed to burn fires hot and fast and will not permit an operator to cut off the air supply.

They must be fed smaller amounts of wood continually, rather than using one big log, which turns into coals that will last all night, Mr. Peck says.

Ross, however, says a moderately full load of logs fed into his stove at 9 p.m. will leave coals hot enough at 6 the next morning to start a fire without kindling.

The key to cutting smoke emissions, says Chris Stoneman, who is in charge of implementing wood-stove standards for the Environmental Protection Agency (EPA) in Washington, D.C., is to burn less wood.

New stove technology focuses on lean-burning fires that consume lots of air and relatively little fuel and burn wood completely. As an added benefit, the fires deposit less of the black, tarry creosote that often coats the walls of older model wood stoves.

"Any wood stove is only as clean as the person operating it," says Mr. Peck.

To ensure complete consumption of fuel, manufacturers rely on three primary devices not present in older technology stoves (generally those sold before 1988).

* A secondary air system automatically allows sufficient air into the stove to burn fuel thoroughly, even when the operator has closed down the stove's primary air-intake system.