There has been a lively debate over the past few months about whether burning wood is actually worse for than coal in terms of greenhouse gases. There is no doubt whatsoever that burning coal is catastrophic for both climate change and air quality, and most types of coal have been banned as fuel in UK cities for decades. Burning wood is seen as the saviour of fire lovers, as a clean and low carbon source. The rapid rise of stoves has been partly built on the low carbon credentials of wood. But is this reputation as the good guy – the fuel it’s ok to burn – justified?
Wood produces more CO2 than Coal!
On a like for like basis, burning wood produces MORE greenhouse gas than coal to produce the same amount of heat. Whoah! Of course, this sets the alarm bells ringing a little, and splatters more than a bit of dirty coal dust on wood’s shiny white suit and wholesome image. But do we stop there? Is that the whole story?
Wood’s carbon neutral claim
Most of wood’s claim to it’s low carbon status is built on the fact that whilst the tree grew, it hoovered up carbon dioxide from the environment (and also ploughed out the oxygen we breathe, of course. Thanks for that!) When the tree is burned, or decomposes on the forest floor for that matter, that same amount of carbon dioxide is released back into the atmosphere. So this gives rise to the claim that burning wood is ‘carbon neutral’. The wood absorbs carbon dioxide whilst it grows and locks it in, then releases it back when it is burnt or decomposes.
So far so good: trees suck in greenhouse gas when growing and release it when we burn it. No increase overall, right? Well, yes, but this is where we have to introduce the thorny question of time frames. If a tree sucks in greenhouse gas for three hundred years, then we chop it down and burn in one cold winter month, that is a lot of gas going back into the atmosphere. In the current climate crisis, this is significant. Also, if we don’t replace that tree with a new one, then we are losing a very good way to store greenhouse gas out of the atmosphere were it does harm. Even if we replace that huge old tree with a weedy little sapling, it will take decades, maybe even centuries before it is hoovering up as much greenhouse gas as its predecessor on a yearly basis.
So the slightly unsatisfactory answer to the question of wood is: ‘it can be good, depending on where you get it from.’ If you want something more concrete, or if you like a more definitive set of easy answers, here’s my quick guide:
Wood that could be used in construction – bad!
Waste of good quality wood that could be used to make useful stuff like houses.
Wood that is not properly seasoned – bad!
Wood with too high a water content creates lots of smoke and burns inefficiently, clogging up your chimney and increasing the chance of a chimney fire.
Scrap wood that has been treated or painted – BAD!
Most pallet and other treated wood contains yucky toxic fumes and can also clog up your chimney.
Wood from rainforest or ancient woodlands – BAD BAD BAD!
(Do I need to spell it out?! Who are you? Donald Trump?)
Clean scrap wood, or wood that is the product of managing woodland – GOOD!
Why the hell not. Low carbon, and usually low cost too.
Wood grown especially for fuel – GOOD!
So long as it is grown on marginal land rather than taking up prime agricultural sites that could be used for food production.
Those bags of wood you buy from the garage when there is nothing else? BAD!
They don’t burn well in my experience, and who really knows where they come from? Not me.
Wood: It’s a win!
Unlike wood, burning fossil fuels only ever increases greenhouse gases in any realistic time frame, and heads us towards dangerous levels of climate change. So replacing coal, gas or oil with wood is a positive move. However, wood is – like most things – not a silver bullet to our climate crisis, and it’s important to look at where it comes from. Clean scrap wood or well seasoned waste wood from careful forest or woodland management burned in an efficient wood stove is clearly a low carbon fuel win.
And so much more satisfying to sit in front of than a radiator, of course…