Wood Stoves and Biomass Plants: What Are They Good For?

Why your wood stove might be giving you more than just a warm, fuzzy feeling.

Written by

David Watson

June 9, 2020

I love a good fire. Who doesn’t?

The dancing flames, the crackling wood, the heady woodsmoke. Fireside stories with old friends. Toasted marshmallows (usually charred to a crisp). Curling up with a book. Simpler times.

Cosying up around the fire is considered an innocent pursuit.

Open fireplaces and wood burning stoves in the home have become a fashion symbol in recent years, a signal of one’s green credentials. They’re fueled by wood, and wood is renewable. Ergo, heating your house with wood must be good for the planet.

In a simple world⁠ — one of cosy, fireside wisdom⁠ — that might be true. But the real world is rarely so simple.

What does woodsmoke smell like to you?

In 2015 I journeyed by bicycle from Mexico to Costa Rica. I saw a lot of things, some beautiful, some sad. I also smelled a lot of things.

When I arrived in Central America, woodsmoke evoked for me those typical, nostalgic feelings we have for wood fires in rich countries. Fast-forward a few months and wood smoke meant for me only one thing: poverty.

A roadside restaurant in Yucutan, Mexico. That’s my tent under the lean-to. With no modern sources of energy available, all the cooking was done over wood (I don’t even think they had charcoal).

In Central America, many families and even restaurants rely on wood for all their cooking and hot water. Gathering and chopping wood is hard work, and women in particular inhale vast quantities of smoke during cooking. Wherever there was wood smoke, there was poverty. It took me a couple of years of being back in the UK to break the association.

The kids at the restaurant got curious as I worked on my bike.

Rich people, wherever they live, don’t normally use wood to cook and heat. Firstly, it’s impractical. It’s much easier to cook with gas or electric. Vitally though, switching away from wood (and coal and dung) reduces the air pollution that the UN estimates kills 7 million people every year. In Canada, it’s thought that air pollution kills 9 times more people than die in car accidents.

There’s no fire without smoke

It doesn’t matter how efficient your burner is, there’s no fire without smoke. As Michael D. Mehta, Professor in the Department of Geography and Environmental Studies, Thompson Rivers University, puts it: “Smoke from wood fires contains dozens of toxic and carcinogenic chemicals…The main threat comes from the cocktail of tiny particles and droplets that are about 2.5 microns in diameter (also called PM2.5). Due to their size, they easily work their way into our lungs, bloodstream, brain and other organs, triggering asthma attacks, allergic responses, heart attacks and stroke.”

Where I live in the UK, the government has reported on many air pollutants since the 1970s, when many cities were shrouded in industrial smog. While there is an overall trend towards lower levels of particulate pollution thanks to the gradual phase out of coal power and the adoption of cleaner industrial practices, when it comes to particulates from domestic woodstoves, levels are the highest they have been since 1990.

In the UK, there are reported to be 1.5 million wood-burning stoves in use, with around 200,000 more sold every year. Shockingly, recent figures show that “the use of wood in domestic combustion activities accounted for 38 per cent of PM2.5 emissions in 2018.”

Pollution from wood stoves and fireplaces in the home are troubling because people, including young children and pregnant women, may be sat mere feet away from the fire. They also tend to be used more at the weekend when wood-burning families (and their unwitting victims, their neighbours) are likely to be in their homes.

When it’s just one house with a wood fire, it’s OK. But what about two, three, four…the whole town?

Wood burning fires are very rarely used as the primary source of heating, with data from the UK suggesting only 8% of homes with wood burners rely on them as the primary source of heating. Wood burners are providing something else then: a connection to imagined simpler times, perhaps? A link to our prehistoric ancestors?

Occasional wood fire indulgence is not the problem — integrating wood burning into your daily life is.

I get it, I really do. I still enjoy a good campfire once a year at my friend’s outdoorsy birthday, or the occasional wood-fired BBQ (maybe even that is too much and I should switch to gas?). But once you realise that a wood-burning stove might be kicking out more particulates than an HGV or up to 18 diesel cars, you start to question: is it really worth it?

Perhaps environmental orgs could learn something from campaigns on the risks of passive smoking.

Trees, not coal

Leaving aside air pollution, at least burning wood is climate friendly, right? Let’s set the bar really low: we won’t compare burning wood with another low-carbon energy source like solar or nuclear. Let’s ask, “Is burning wood better for the climate than burning coal?”

That question has to be answered in two parts: firstly, does burning wood release more CO2 than burning coal? Secondly, will new trees grow in the future to make up for the carbon released from burning wood today?

According to Sterman et al.’s paper, the answer to the first question is an emphatic “no”. It’s down to basic physics. Put simply, burning wood produces more CO2 per unit of useful energy than does coal. So replacing coal with wood means more CO2 out the stack today.

The paper goes onto to look at how long it takes to “pay back” the carbon released from burning the wood by growing new forest. The results are quite surprising: “The payback time for this carbon debt ranges from 44–104 years after clearcut, depending on forest type — assuming the land remains forest.”

Enviva’s Northampton facility, which has a production capacity of 510,000 metric tons of wood pellets per year. Enviva recently filed an application to expand this enormous facility (Image courtesy Dogwood Alliance).

Not only is burning trees not low carbon, it also destroys forest habitat on a massive scale. Organisations like the Dogwood Alliance have uncovered unsustainable practices at one of the world’s largest biomass producers, Enviva. Much of Enviva’s wood is shipped all the way to the UK to be burned in modified coal power plants for green subsidies. A single UK plant, Drax, received a whopping £789.5 million in green subsidies from burning trees in 2019 alone.

What’s the deal, then? Why do renewables advocates and even the EU Commission support burning trees to produce electricity?

What’s green and keeps the lights on?

Things have got confused. The world is searching for low-carbon power. Solar and wind produce electricity with zero emissions (at the point of generation). Solar and wind are renewable. Therefore, renewable is good?

But it’s not always windy and the sun goes down every night. What can fill the gap to meet electricity demand? Trees can be burned 24/7, whatever the weather. Trees are renewable. Burning trees is good?

It doesn’t have to be that way. There are three other sources that can produce low-carbon, always on power: hydro, geothermal and nuclear. Pick the one that suits your geography and tastes, and go for it. There’s still time.

Alastair McIvor put together this graphic showing the states that have built large electrical grids without significant use of fossil fuels or biomass: solar and wind plus some hydro or nuclear will do it.

A green future?

In the late 80s, wood burning stoves looked like they were going to disappear in rich countries because, simply put, they are inferior to the alternatives. Their recent return to popularity is part of a wider anti-progress movement that includes organic food and a preference for “natural” ingredients. Only when this lifestyle trend fades in favour of technological progress and human health are we likely to see any change. That, or if governments crack down on domestic air pollution like London did following the lethal Great Smog of 1952.

Such a ban may be coming in the near future in some countries. The UK government has already announced plans to make illegal the selling of coal for domestic fires by 2023. By February 2021, the bags of wood sold on garage forecourts around the country must be dry (AKA seasoned) wood, which has lower emissions that wet (AKA green) wood.

As for biomass for electricity, recent documentaries like Planet of the Humans, error strewn though it is, have raised the biomass issue up the agenda. I feel (hope) that this strange industry will slowly start to lose political support in favour of other firm, low-carbon alternatives.

Further reading

WRITTEN BY

David Watson

Ecopragmatist, clean energy advocate, believer in pedal power. Editor@Generation Atomic. All views strictly my own.

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