Thursday, January 21, 2021
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The burning question: Is your wood stove actually green?

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As far as climate change and human health are concerned, no wood stove is the best wood stove, according to some experts.

The negative impacts to human health associated with particulate matter emitted from residential wood stoves aren’t disputed, said Michael Mehta, a professor of geography and environmental studies at Thompson Rivers University in Kamloops, B.C.

Yet, the myth persists that wood-burning as a residential heat source, particularly in rural areas or smaller communities, is natural and green, said Mehta, a specialist in environmental and health risk issues.

“The problem is there’s been this false presentation of environmental performance as carbon neutral, when it’s not,” Mehta said.

Proponents of burning wood as an energy source, particularly wood pellets, argue it’s a low-carbon fuel. The argument is that carbon released when trees are cut down and burned will be recaptured by new trees that grow in their place.

But recycling carbon with forests while burning wood is more complicated than presented, and it encourages people to use wood rather than switching to healthier and more sustainable heating methods, Mehta said.

It can be argued that burning wood is renewable, but that doesn’t mean it’s sustainable in terms of curbing climate change, he added.

“People seem to think that they can just harvest trees and burn them and it’s a wash,” Mehta said.

“But, we’ll never be able to get at climate change in time if we think that way.”

Burning wood releases carbon immediately, but it takes upwards of 40 years for a tree to start capturing any significant amount of carbon, he said.

Yet in the short term, all the atmospheric carbon will continue to accelerate climate change, already an urgent problem.

“The second problem is when you burn wood from trees, you release a very potent short-lived climate pollutant called black carbon,” Mehta said.

In essence soot, black carbon is a component of fine particulates (PM2.5) emitted during wood burning that contribute to air pollution and are of particular concern to human health.

Black carbon from wood stoves can travel long distances and has a climate-warming effect, Mehta said.

The material absorbs sunlight in the atmosphere and heats it surroundings, he said. And if deposited on ice or snow, it reduces the materials’ ability to reflect sunlight, increasing glacial melting and accelerating global warming, he added.

Rather than using a wood stove, people would do more for the environment and their own health, and that of their neighbours, by switching to other heating options, said Mehta.

The B.C. government funds a wood stove exchange program in conjunction with a number of municipalities and regional districts that offers rebates to replace older, dirty wood stoves with new and cleaner sources of heat, such as electric heat pumps, gas or pellet stoves, or cleaner-burning emission-certified wood stoves.

The annual program has helped replace about 9,000 old stoves with cleaner options since its inception in 2008.

A total of 19 B.C. communities have funding in the coming year for the wood stove rebates, including the Strathcona Regional District, along with five other Vancouver Island regional districts.

Eligible households can apply and get $250 towards a certified wood stove, or $400 towards a qualifying electric heat pump, gas or propane or pellet stove.

Homes in “red zone” communities, where the fine particulate pollution exceeds federal air-quality standards, may be eligible for $500.

However, Mehta is concerned the program still provides the option of substituting one wood stove for another, regardless of the fact it’s certified and releases fewer emissions.

“It gives people the impression that their new wood stove is so clean that they can burn with impunity whenever they want and whatever they want,” he said.

Many people don’t have access to high-quality, dry seasoned wood necessary to limit harmful emissions, he added.

Wood stoves still have value as a secondary heat source in rural or isolated communities during extended power outages, Mehta said, but fundamentally, there are better heating technologies available.

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“For everyday use, an electric heat pump, or mini-split heat pump, is the best technology,” he said.

“It’s a technology that’s been around for decades. There are tens of millions of them deployed around the world.”

Markus Kellerhals, a senior air quality science officer for B.C.’s Ministry of Environment and Climate Change Strategy, said the intent of the wood stove exchange program is to encourage people to switch out their wood stove for alternative heating methods.

“That’s reflected in the (financial) incentives offered by the program,” Kellerhals said.

In terms of air quality and health impacts, there is no minimum safe level of particulate emissions from wood stoves, he said.

“But on the other side of the coin, if someone with a dirty wood-burning appliance replaces it with a cleaner-burning stove, it won’t eliminate emissions, but it will significantly reduce them,” Kellerhals said.

And, for some lower-income households, the higher investment options — such as a heat pump, which can range in the thousands of dollars — aren’t viable options, he said.

“There’s a proportion of the population where heating a house in winter is a significant financial burden and who can’t obtain cheap or free wood,” Kellerhals said.

“And those people are going to be less likely to switch to a heat pump, or any gas infrastructure either.”

Many people who own their own homes and use wood as a primary heat source have sufficient capital to cover the higher initial cost of a heat pump, especially when factoring in the energy savings that follow and taking advantage of rebates offered by BC Hydro, Mehta said.

And there are often significant economic costs associated with heating with wood, he said

Some residents with large forested properties, or who live in isolated areas, may have ready access to free or low-cost wood, but many households using the stoves as the primary heat source purchase wood, Mehta said.

That can cost as much as $1,800 or more in the winter, he said.

Over the course of history, people moved away from burning wood due to the threat to human health and because it was an inferior heating method, he added.

“And now … people are moving back to burning wood, which has the lowest energy density and is the highest polluting source of energy that you could have in your home.”

Rochelle Baker / Local Journalism Initiative / Canada’s National Observer





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