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Wood heat rises again

High cost of oil and gas fuels a boom in wood stoves. But what is the cost to climate?

By Staff writer of The Christian Science Monitor / October 21, 2008

The Beatty family near Paxico, Kan., heats their entire home with this wood stove. Modern wood-burning stoves emit far fewer pollutants in the form of fine particulates than did models from the 1970s. Environmentalists can’t agree on the stoves’ carbon footprint.

David Pulliam/The Kansas City Star/AP/File

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George and Judith Reilly own a big antique house on the main street of Brandon, Vt., a picturesque town on scenic Route 7. The house’s front parlor doubles as a gallery to display the fabric art Judith creates in her upstairs studio.

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Last spring, when oil for the house’s furnace began to top $4 per gallon, Mr. Reilly did some quick calculating and decided he could save up to 50 percent on his heating cost this winter by installing a stove that burned sawdust pellets. Over the summer, he placed an order with first one, then another local dealer. But by October, both had failed to find him a stove. Finally, he discovered one on eBay. The only problem: Reilly had to drive his pickup truck from Vermont to Maryland to claim it. Last weekend, as nighttime temperatures dipped below freezing, he was installing his prize, which he hopes will be his main source of heat this winter.

Both traditional and pellet-burning wood stoves are in high demand as cold weather begins to grip the northern United States and Canada. Sales of wood stoves are up 55 percent so far this year over last, according to industry figures. And sales of wood pellet stoves are even hotter: up 135 percent over the same period last year.

But as people polish their stoves and admire their woodpiles, environmentalists and health officials are expressing concern that burning wood in old or poorly designed stoves could add significantly to air pollution. And although wood represents a local and renewable fuel source, its credentials as a “carbon neutral” fuel – not adding to global warming – are hazy at best.

Even the very cleanest-burning and best-maintained wood or pellet stoves release a much higher level of emissions than a typical oil furnace, a common heating fuel in the Northeastern US. Natural gas, the most popular heating fuel nationwide, burns even cleaner than oil.

Wood smoke “is a fairly toxic cocktail,” says Lisa Rector, a senior policy analyst for NESCAUM, a nonprofit group that advises eight Northeastern US states on air-pollution control issues. According to the Environmental Protection Agency (EPA), wood smoke contains a number of potent health hazards, including carbon monoxide, nitrogen oxides, and fine particulates. The American Lung Association estimates that in some locales fireplaces and wood stoves are the source of 80 percent of the fine particulates found in the air.

Judging how polluting a particular wood stove is can be tricky. Since the early 1990s the EPA has mandated that new wood stoves emit no more than 7.5 grams of emissions per hour, though many models have been tested with much lower emissions. Stoves manufactured in the 1970s and ’80s emitted about 42 grams per hour, according to the Hearth, Patio, and Barbecue Association (HPBA), which represents wood stove manufacturers.

But how much pollution a stove emits also depends on what is being burned.

“A tree is not a tree is not a tree,” Ms. Rector says. “It is what it lives in.” Trees can pick up substances such as mercury, sulfur, or chlorine from the soil in which they grow. And if the wood is not properly seasoned or wet, combustion will be less complete. (See below.) Not only will the stove give off less heat, it will pollute more.

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