Once viewed as virtuous, wood stoves are climate and health villains
Today's guest article is by Michael D. Mehta, Ph.D., who teaches geography and environmental studies at Canada’s Thompson Rivers University. Dr. Mehta is affiliated with Doctors and Scientists Against Wood Smoke Pollution, and is President and CEO of the Sweet Spot Solar Company.
His article comes to us courtesy of The Conversation. We’ve edited it for style and clarity and added information about the climate impacts of wood-burning and safer, healthier home wood-burning.
Blame wood-burning stoves for
winter air pollution and health threats
By Michael D. Mehta, Ph.D.
The World Health Organization ranked air pollution and climate change as the top health threats for 2019, and one in nine deaths around the world are linked to air pollution.
In Canada, air pollution kills nine times more people than automobile accidents. My own research shows that in rural British Columbia the main source of winter air pollution is residential wood burning, and that it is mostly being ignored and rarely monitored by government.
Wood-burning is a health hazard
While wood smoke is natural and smells good, there’s nothing safe or “green” about heating your home with wood.
The main threat comes from the cocktail of tiny so-called PM2.5 particles in woodsmoke, which are about 2.5 microns in diameter and easily work their way into our lungs, bloodstream, brain and other organs.
The PM2.5 particles in woodsmoke can trigger asthma attacks, allergic responses, heart attacks and stroke, and chronic exposure to them is linked to heart disease, lung cancer in non-smokers, chronic obstructive pulmonary disease, type II diabetes, and dementia.
Wood smoke affects everyone, but children are especially vulnerable in part because their respiratory systems are under development. Children hospitalized for lower respiratory tract infections are more likely to have a wood stove in the house, although other factors may also play a role.
Pregnant women exposed to wood smoke may have children with smaller lungs, impaired immune systems, decreased thyroid function, and changes to brain structure that may contribute to difficulties with self-control.
The elderly are also at risk, with a recent study of people living in the Kamloops, Prince George, Courtenay, and Comox Valley regions of British Columbia showing that wood stove pollution raised the rate of heart attacks in people over 65 significantly.
And that nice smell? It comes from benzene — a carcinogen (cancer-causing substance) — and acrolein, which irritates the eyes, gastrointestinal tract, and lungs.
With the dozens of toxic and carcinogenic chemicals in wood smoke, it’s inconsistent for governments to ban smoking and vaping in public places while ignoring the smoke from wood stoves and fireplaces.
Wood for home heat and electricity: Neither clearly sustainable nor carbon-neutral
Last year, the authors of two studies concluded that burning wood releases more carbon than burning coal, and that wood-burning accelerates global warming (Sterman D et al. 2018; Booth MS 2018).
[Editor's note: Those analyses have been challenged by another group of scientists, who share the concern about wood but dispute some of the underlying assumptions and the consequent degree of concern (Prisley S et al. 2018).]
Nonetheless, both sides of that scientific debate agree that wood burning isn’t necessarily carbon-neutral and is a significant source of carbon emissions — and there’s little doubt that wood-burning generates lots of particularly unhealthful air pollution.
Wood-burning also releases a powerful short-lived pollutant called black carbon that can speed the melting and retreat of glaciers, which in turn drives rises in sea level and depletes a major source of water for hundreds of millions of people.
According to the Center for Climate and Energy Solutions (formerly the Pew Center on Global Climate Change), “Black carbon has recently emerged as a major contributor to global climate change, possibly second only to CO2 as the main driver of change. Primary sources include emissions from diesel engines, cook stoves, wood burning and forest fires.”
Healthier, greener alternatives to wood heat
Mini-split air source heat pumps are an excellent option, as they are often three to four times more efficient than electric baseboard heaters and can work in colder climates.
Efficient propane stoves and heaters are an excellent complement to heat pumps and can provide top-up heating on very cold days as well as backup heating during power outages.
The British Columbia Lung Association has been a strong advocate of wood stove exchange programs. But even the cleanest, highest level of eco-certified wood stoves generate more particulate matter per hour than 18 newer diesel passenger cars — and a wood stove sits right in your home.
Citizen science is a gamechanger
Wood smoke, and the cultural and social practices that allow it to be generated without much regulation and control, operates in a vacuum where preconceptions and strong emotions impair action.
Burning wood deprives people of the right to breathe clean air in their own homes, and it ultimately represents an uncontrolled form of secondhand smoke exposure with broad implications.
Concerned citizens have set-up an extensive and a growing network of low-cost air quality sensors made by PurpleAir, which can be used to monitor air quality in your home or business. [Editor’s note: PurpleAir sensors currently range in cost from $179 to $259, and similar indoor-air sensors are available, some at lower cost.]
Hundreds of communities around the world whose topography tends to trap air pollution have been installing networks of these wireless-enabled, real-time sensors — and these monitors show a distinct and troublesome pattern.
These sensors reveal the chemical “signature” of wood burning and show that many rural Canadian communities often have winter air pollution levels that far exceed those seen in larger cities — and that some places register air quality readings that rival bad air days in China and India.
Lack of government action to deal with and publicize this problem encourages people to ignore this evidence and to underestimate the risk.
Editor's note: Click here to view Dr. Mehta's original article.
Editor's note: Tips for cleaner, healthier, efficient wood-burning
These “Best Wood-Burning Practices” come from the U.S. Environmental Protection Agency (EPA):
Building a Fire
- Burn only dry, split, well-seasoned wood. Properly seasoned wood is darker, weighs less, and sounds hollow when hit against another piece of wood.
- An efficient fire requires good firewood, using the right wood in the right amount, and good fire building technique.
- Store wood outdoors, off the ground, with the top covered, and season it for at least six months.
- Wood burns best at a moisture content of less than 20 percent. Test wood with a wood moisture meter before you burn it.
- Start fires with newspaper, dry kindling, or all-natural fire starters, or install a natural gas or propane log lighter in your open fireplace.
- Buy and burn locally cut firewood to decrease the risk of transporting invasive forest pests to your property.
Safe Wood-Burning Practices
When using your wood burning appliance, follow these guidelines for safe operation:
- Keep flammable items, like curtains, furniture, newspapers, and books, away from your appliance.
- Only use newspaper, dry kindling and all-natural or organic fire starters. Never start a fire with gasoline, kerosene, or charcoal starter.
- Do not burn wet or green (unseasoned) wood.
- Many wax and sawdust logs are made for open hearth fireplaces only. Check your wood stove or fireplace insert operating instructions before using artificial logs.
- If you use manufactured logs, choose those made from 100 percent compressed sawdust.
- Build hot fires. For most appliances, a smoldering fire is not safe or efficient.
- Keep the doors of your wood-burning appliance closed unless loading or stoking the live fire. Harmful chemicals, like carbon monoxide, can be released into your home.
- Regularly remove ashes into a covered, metal container. Store the container outdoors on a nonflammable surface.
- Keep a fire extinguisher handy.
- Check your local air quality forecast before you burn.
What Not to Burn
These materials can release toxic or harmful chemicals when burned, and may damage your appliance:
- Household trash, including cardboard, plastics, foam and the colored ink on magazines, boxes, and wrappers
- Coated, painted, and pressure-treated wood
- Ocean driftwood, plywood, particle board, or any wood with glue on or in it
- Wet, rotted, diseased, or moldy wood
- Plastic, asbestos, rubber, manure and animal remains
- Booth MS. Not carbon neutral: Assessing the net emissions impact of residues burned for bioenergy. Environmental Research Letters, Volume 13, Number 3. Published 21 February 2018. Accessed at https://iopscience.iop.org/article/10.1088/1748-9326/aaac88
- Center for Climate and Energy Solutions. What is Black Carbon? Accessed at https://www.c2es.org/document/what-is-black-carbon/
- ClimateCentral.org/John Upton. Pulp Fiction: The European Accounting Error That's Warming the Planet. Accessed at https://reports.climatecentral.org/pulp-fiction/1/
- Mongabay/ Catanoso J. UN forest accounting loophole allows CO2 underreporting by EU, UK, US. May 2, 2018. Accessed at https://news.mongabay.com/2018/05/un-forest-accounting-loophole-allows-co2-underreporting-by-eu-uk-us/
- Sterman D et al. Does replacing coal with wood lower CO2 emissions? Dynamic lifecycle analysis of wood bioenergy. Environmental Research Letters, Volume 13, Number 1. Published 18 January 2018
- Prisley S et al. Comment on 'Does replacing coal with wood lower CO2 emissions? Dynamic lifecycle analysis of wood bioenergy'. Environmental Research Letters, Volume 13, Number 12. Published 18 December 2018
- The New York Times/ Schlesinger S et al. Pruitt Is Wrong on Burning Forests for Energy. May 3, 2018. Accessed at https://www.nytimes.com/2018/05/03/opinion/pruitt-forests-burning-energy.html