In NewScientist (4 February 2017, paywall) Michael Le Page reports on the use of wood burning stoves to avoid fossil fuels – and how they add substantially to London pollution. And then comes the kicker:
Credit: Canadian Off The Grid
So do the health impacts outweigh any climate benefits? Astonishingly, there might not be any climate benefits, at least in the short term.
Burning logs is often touted as being carbon-neutral. The idea is that trees soak up as much carbon dioxide when growing as they release when burned.
In fact, numerous studies show that wood burning is not carbon-neutral, and can sometimes be worse than burning coal. There are emissions from transport and processing. Logs are often pre-dried in kilns, for instance.
Burning wood also emits black carbon – soot – that warms the atmosphere during the short time it remains in the air. Most studies ignore this, but [Eddy Mitchell at the University of Leeds, UK] and [climate scientist Piers Forster, also at Leeds] calculate that over 20 years – the timescale that matters if we don’t want the world to go too far above 2°C of warming – soot cancels out half the carbon benefits of all wood burning.
For home wood burning, the figures are even worse. “On a 20-year timescale, wood stoves provide little or no benefit, but they do on the 100-year timescale as they remove some of the long-term warming effect of CO2 emissions,” says Forster.
The devil is in the details, evidently, and not, uh, in the stove. The findings are still controversial – but something to think about if you’re wondering about wood burning stoves. Incidentally, the picture source is from a blog posting in early January 2014, complaining that the EPA was preparing to ban wood burning stoves which did not meet standards, and quotes a press release:
The federal Environmental Protection Agency has proposed new standards for wood stoves that would reduce the maximum amount of fine particulate emissions allowed for new stoves sold in 2015 and 2019.
Maximum emissions would be reduced by one-third next year and by 80 percent in five years, the Fairbanks Daily News-Miner reported.
Fine particulate pollution is made up of solid particles and liquid droplets that measure 2.5 micrometers in diameter or less. The EPA currently certifies non-catalytic wood stoves if they produce less than 7.5 grams of fine particulate per hour.
Fine particulate absorbed by breathing has been linked to heart attacks, decreased lung function and premature death in people with heart or lung disease.
The proposed EPA regulations would reduce that to 4.5 grams per hour for stoves manufactured after the regulations go into place next year.
I don’t know if the first set of regulations went into effect, or if the second is still on the specified schedule.
