Should Green Homes Burn Wood?
Extracting fossil fuels like coal, natural gas, and oil — by mountaintop removal, fracking, and deep-sea drilling — all entail environmental risks
Environmentalists often argue over the wisdom of heating homes with wood. Strong arguments can be marshaled on both sides of this debate, so I’ll do my best to represent both positions before summing up.
Burning wood makes environmental sense
According to wood-fuel advocates, burning wood is carbon-neutral. While burning wood releases carbon into the atmosphere, the carbon would have been released anyway if the tree had died of old age and rotted on the forest floor.
Here’s how a forest’s carbon cycle works: as trees grow, they sequester atmospheric carbon by converting CO2 in the air to leaves, twigs, and wood. The CO2 isn’t permanently sequestered, however, since virtually all wood (with a few exceptions, like Tutankhamen’s throne) eventually burns or rots. The amount of carbon released by burning is the same as the amount released by rotting.
As long as firewood is sustainably harvested — that is, as long as a logger limits annual cutting to the annual growth of the forest — burning firewood is carbon-neutral.
Wood-stove advocates also point out:
Burning wood is an environmental disaster
Environmentalists opposed to wood burning often live in congested areas affected by air pollution or in areas where forests are threatened. Seeing trees as precious, they don’t look kindly on logging trucks.
Foes of wood burning point out:
- In many parts of the world, annual firewood cutting exceeds annual forest growth — so wood burning is not carbon-neutral.
- Commercial firewood harvesting requires fossil fuel for chainsaws and trucks, undermining the argument for carbon neutrality.
- If everyone in the U.S. burned wood, the nation’s forests would be decimated.
- Wood smoke includes many noxious pollutants that contribute to lung disease and cause premature deaths.
Particulates are probably the most dangerous components of wood smoke. Particulates small enough to enter deep into the lungs are known as PM10 particulates (meaning they have a diameter of 10 microns or less); these are the particulates that are most likely to contribute to lung disease. Those most vulnerable to smoke-related health problems are people with asthma, young children, pregnant women, and the elderly. According to one source, each year in the U.S., particulates from all sources (including vehicle exhaust) are responsible for 30,000 premature deaths from lung disease, heart attacks, and stroke.
In addition to particulates, wood smoke includes small but significant amounts of arthracen, benzene, biphynel, carbon monoxide, chrysene, dioxin, fluoranthene, formaldehydeChemical found in many building products; most binders used for manufactured wood products are formaldehyde compounds. Reclassified by the United Nations International Agency for Research on Cancer (IARC) in 2004 as a “known human carcinogen.", naphthalene, nitrogen oxide, phenanthrene, polycyclic aromatic hydrocarbons, pyrelene, pyrene, and sulfur dioxide. Each of these chemicals can negatively affect human health.
Weighing pluses and minuses
Burning wood is almost carbon-neutral. In light of the looming problem of global climate change, carbon neutrality is nothing to sneeze at.
If you harvest firewood with a bow saw and a wheelbarrow, as I did in my early years, wood is as close to carbon-neutral as any fuel. In most cases, though, firewood is harvested with a chainsaw and a truck. According to those who have studied the issue, each BTUBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. of fossil fuel used to harvest firewood yields 25 BTUs of wood fuel — a respectable ratio. In the future, perhaps, loggers will use chainsaws that burn alcohol distilled from sugar cane and drive trucks fueled with biodiesel.
It goes without saying that anyone involved with green building should cut their own wood or buy their firewood from loggers concerned with sustainability. However, I don’t believe we should use a global assessment of forest health to judge the morality of local wood burning. Just because forests are severely threatened in Haiti and Madagascar does not mean that Americans should refrain from harvesting firewood near their homes. In this sense, all forestry is local.
In many northern and southeastern states, the woods are full of unharvested fuel, including standing dead wood, fallen limbs, trees knocked down by ice storms, and stands of dense forest that would benefit from thinning.
The deleterious effects of wood smoke on human health are a serious concern. However, wood smoke is much less likely to cause health problems in sparsely populated rural areas than in densely populated areas.
Newer stoves pollute much less than older stoves. EPA regulations established on July 1, 1988, required stoves to meet stricter limits on particulate emissions. On July 1, 1990, newer Phase II regulations — which require stoves with catalytic converters to emit less than 4.1 grams of particulate matter per hour and stoves without catalytic converters to emit no more than 7.5 grams per hour — took effect.
All fuels have disadvantages. (Read more about fuel choices on GBA’s “Heating Options” page.) If you have an electric heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump., remember that 50% of U.S. electricity is generated by coal-burning power plants. The recent oil spill in the Gulf of Mexico and recent coal-mine disasters (not to mention mountaintop removal) have reminded Americans of the risks associated with oil drilling and coal mining. While flue gases emitted by a gas furnace are far more benign than wood smoke, gas drilling and gas pipelines also have negative environmental effects.
Responsible wood burning
Because of the health problems associated with wood smoke, wood burning is inappropriate in densely populated town and cities. Wood burning is also inappropriate in areas where forests are threatened.
If you live in a rural area and choose to burn wood:
- Cut your own firewood or buy your fuel from a responsible logger who harvests firewood sustainably.
- Use a right-sized wood stove. A hot fire in a small stove produces cleaner smoke than a smoldering fire in a large stove.
- Use an EPA-certified wood stove. Do not use an outdoor wood-fired boiler; these appliances are notoriously smoky and inefficient.
- Don’t use your stove to burn trash.
- Cut or buy your wood one year before your burn it, and store it under metal roofing or in a woodshed. Seasoned firewood burns cleaner than green firewood.
- No matter what kind of fuel you burn, strive to improve your home’s thermal envelope. Plugging your home’s air leaks, improving your home’s insulation, and adding storm windows will save you money and reduce the amount of wood you need to burn. That’s good for your pocketbook and good for the planet.
Last week’s blog: “Housewrap in a Can: Liquid-Applied WRBs”
- Martin Holladay
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