Is firewood a renewable fuel for a sustainable future?

Renewable? Sustainable? Eco-friendly?

Wood is an incredible material.

It grows naturally almost everywhere in the world.

We’ve been using it for too many things to mention, for too long to remember.

It’s easy to imagine that one of the first ways we used it, was to keep warm. But is firewood a green way to heat our homes in a sustainable context?

We’ve been burning wood for over a million years. Control of fire, soon after the creation of art, is a defining property of intelligence.

Today trees need pruning and an olive grove gives you firewood, for free. A tree dies, cut it down, plant two. What’s not to like?

We all want to stay warm in winter. And someone who has access to firewood is probably going to use it.

Reasons to burn firewood

• To keep warm in winter
• A hot fire warms the soul
• Firewood is cheap
• Firewood is free
• I only use wood occasionally
• Wood is the only heating we’ve got
• I use a wood burner as a backup for power cuts
• We’ve been using wood for ages

Is firewood a renewable?

If we’ve been using wood for so long it must be OK, right?

In theory, cutting one dead tree down and planting another one or two so at least one grows into a mature tree, doesn’t reduce the number of trees in the world or contribute to deforestation.

In the long-term you’re not reducing the amount of carbon dioxide (CO2) trees take out of the atmosphere during their lifetime.

The leaves on a live tree take CO2 out of the atmosphere during photosynthesis. The tree releases oxygen as a by-product. This is the oxygen in the air we breathe. A dead tree doesn’t take CO2 out of the atmosphere or produce oxygen. The CO2 (carbon) stored in dead wood, is emitted slowly as the wood rots.

In theory, wood is a renewable, if forests are managed in a sustainable way.

Does burning wood produce pollution?

When we burn wood it produces the following:

• Carbon Dioxide (CO2) is produced when wood and other fuels burn. CO2 is not toxic in low concentrations and is exhaled by animals (including humans) as part of the natural breathing process. CO2 is a greenhouse gas and human (industrial/vehicle) emissions are widely considered to be a major cause of global heating. CO2 has a greater effect on climate change than any other gas because of the amount we produce. In 2019, 80% of US greenhouse gas emissions were CO2.

• Nitrogen dioxide (NO₂) is a greenhouse gas 300 times more damaging than CO2. It lasts 120 years in the atmosphere. It is a known contributing factor to acid rain, asthma and other respiratory problems in children.

• Methane is a toxic greenhouse gas 21 times more potent than CO2.

• Carbon monoxide (CO) is a poisonous gas produced by incomplete combustion. It is basically invisible and odourless. It’s this gas that kills people who connect a hose to their exhaust pipe, poke the other end through a window, and sit in the car with the engine on. Smouldering embers produce a lot of carbon monoxide. A good CO alarm costs about €25.

• Fine particles are carcinogenic for humans. Wood burnt in UK home fireplaces in 2019 produced 38% of PM2.5 fine particle pollution (under 2.5 microns in size). That’s over 3 times the PM2.5 emissions from road traffic.

Burning wood produces toxic gases and substances. The amounts vary greatly depending on what wood we burn, and how we burn it.

• Tools (chainsaws) and vehicles used to cut and deliver firewood burn fossil fuels. 2-stroke chainsaws burn a fuel/oil mix, oil is used to lubricate saw chains.

How burning wood releases stored carbon

Burning wood releases carbon dioxide (CO2) into the atmosphere.

This CO2 was taken in by the tree as it grew. Therefore there are no long-term additional CO2 emissions. But, the CO2 that was stored in the wood during the tree’s lifetime is released immediately when we burn it.

A tree can store a lot of CO2 in 10-20 years, and all this CO2 is emitted into the atmosphere immediately when we burn it.

If we plant another tree of the same species, it will take it years to grow and soak up the same amount of CO2.

So CO2 stored in trees over decades is released quickly into the atmosphere when firewood is burnt.

If we burn wood from a tree that’s 10 years old, it will take a new tree 10 years to absorb the CO2 we’ve released into the atmosphere in just a few months.

There may be no long-term additional CO2 emissions. But we are not reducing greenhouse gas emissions this decade by burning wood now.

Wood pellets

Pellet stoves are efficient wood burners. They burn cleaner than other wood burners, but can still produce harmful emissions. A catalytic pellet stove will produce more heat and fewer emissions.

The wood pellet production process is an additional source of pollution. Pellets are often not produced locally, and cost more than locally-sourced firewood.

Letting trees rot

Decaying woodland provides a natural habitat for insects and wildlife. It plays a critical role in a forest‘s ecosystem.

The natural decomposition of dead vegetation produces emissions such as CO2 and methane. Dead wood stores a lot of carbon. It releases more than we do burning fossil fuels.

But letting wood rot produces less carbon dioxide than burning it. Around 6 times less.

Forest fires emit a lot of CO2 and other toxic gases in just a few days. Unmanaged, uncleared areas are one of the major causes of forest fires.

In a world that’s heating up and catching fire, clearing fire breaks sounds like a good idea.

Sustainable forest management can help prevent wildfires destroying large numbers of trees and homes.

So:

• sustainably managed forests
• trees cleared to create fire breaks
• wood from controlled sources used in a sustainable way

Is firewood green?

Burning wood produces harmful emissions, it can produce a lot of air pollution and contribute to global heating.

In the UK the sale of coal and wet wood has been banned.

So wood is not a green fuel. And the greener (wetter) it is, the more pollution it produces.

But many of us still burn wood to heat our homes.

You’ve got an olive grove, the trees need pruning. There’s a dead tree to cut down.

And we all want to stay warm in winter.

Reasons not to use firewood

There are many good reasons to burn wood, and one good reason not to.

• Burning wood produces pollution

How can we reduce emissions?

The most effective way to reduce emissions is to use more sustainable heating systems like heat pumps.

But if we’re going to use firewood, we can burn as little as possible, as efficiently as possible. Properly dried wood burnt in an efficient wood burner produces less smoke and burns with a hotter flame, reducing emissions.

Burning firewood does produce pollution, as do most of the things we still do.

Next month we’ll take a look at how to burn less firewood more efficiently and reduce emissions.

If you’ve got an article about how you’re going green, or a project you want content written for