Lots of Lewes homes have installed woodburners as an eco-friendly heating choice. But with growing reports about their contribution to air pollution, is it time to put out the flames? Woodburner owner Ann Link takes a look.

A few years ago, wood-burning stoves were promoted as climate friendly, but this has changed because of new realisation of the urgency of the climate crisis and increased awareness of air pollution.

As part of the eco-renovation of our home on The Nevill in Lewes in 2009, we got a woodburner that also heats water for radiators and for washing. We saw it as one way to lower carbon emissions, especially as East Sussex has a relatively high percentage of woodland and a tradition of coppicing, giving us a steady and local supply of wood. Although burning of wood creates carbon dioxide, that CO2 is taken in again by growing trees as part of the process of photosynthesis. Provided the wood fuel is replaced by new tree growth, it should be carbon neutral.

This view was widespread at the time, and was endorsed by the organisation that assessed our house as an ‘Old Home Superhome’.  I could see that this approach would not do for everyone, especially city-dwellers, but I saw it as part of a mix that could reduce demand for fossil fuels. Using wood supports local employment and provides heat when other things might not work – for example during a power cut. We briefly considered an air source heat pump, but thought it was too untried for us at that time.

So, what are the problems now?

One major current objection to woodburning is that it produces carbon dioxide now, but all that CO2 then takes 20 or 30 years to then be absorbed back into trees. Given the climate emergency, we need to be removing carbon from the air as quickly as we can – and trying not to add to it – if we’re to reach the net-zero carbon emissions targets that are so crucial to stop global warming. We should be building with wood, which locks carbon away.

Additional factors are that wood fires, along with diesel vehicles, coal burning and other combustion, produce particles of black carbon. These have a warming effect in the atmosphere, and if they fall on snow, they darken it and make it absorb heat more easily, adding to warming in cold regions.

Black carbon’s absorption of solar radiation is comparable to that of carbon dioxide. Yet black carbon only remains in the atmosphere for days or weeks, while carbon dioxide can remain in the atmosphere for hundreds of years. In 2013, a major scientific report said the biggest gains to tackle global warming would come from reducing soot from diesel engines and domestic fires.

Air pollution causing ill health is another factor. It may not be much of an issue for a home on top of a breezy hill in Lewes, but it would be in the new North Street development near the river, a previous developer once proposed wood-burners as a key means of home-heating. When there is cold air near the ground, smoke does not rise far, and so it hangs around to cause smog. In cities, wood burning is clearly unsuitable. Wood fires, as well as candles and gas cookers, also add to indoor air pollution.

What can you do if you have a woodburner or open fire?

Cambridge Carbon Footprint give excellent hints on avoiding air pollution when using a woodburner, including using dry wood from a sustainable local source. They also warn that most cities will be able to ban wood burning in a few years, except in a Defra-approved stove, which are already available. However, given that we are emitting carbon dioxide now, but only absorbing it over the next 30 years, wood burning needs to be decreasing, even with the best new stoves. The solution therefore is to try to burn wood less, by increasing insulation and considering other sources such as heat pumps.

And what about biomass?
For the climate, a bigger issue is that power stations such as Drax are converting from coal to ‘biomass’ which often means using chipped wood from US forests, which may not be grown sustainably and may be destroying ecosystems. Biomass is claimed to be carbon neutral and counts as a renewable source.

A Chatham House report that aims to be a neutral guide to this contested topic still concludes that supporting biomass as a fuel increases carbon emissions. “In reality, carbon dioxide and methane will be emitted from the combustion of woody biomass (generally at higher levels than from the fossil fuels it replaces) and from its supply chain of harvesting, collecting, processing and transport.” It says policies need to change, yet the UK government and many others are planning to increase the use of wood to produce energy.

Biofuelwatch also campaigns against the use of wood fuel in power stations. It says: “There is only one proven way of removing any CO2 from the atmosphere: allowing natural ecosystems – including healthy soils – to flourish and regenerate, and helping restore them where necessary. If we want to have any hope of stabilising the climate, we need an end to fossil fuel burning as well as allowing a lot more forests and other ecosystems to grow. Cutting down forests to replace some fossil fuels is completely the wrong answer.”

Industrial biomass vs domestic wood-burning
Bioenergy, such as biomass, broadly accounts for 11% of all UK electricity generation – and rising. Compared to this activity, the contribution of domestic wood-burning to pollution and climate change may be relatively small. The amount of wood burned in homes was estimated at 4.8m tonnes in 2017 (although this is thought to be a significant overestimate). Conversely, Biofuelwatch say that Drax alone burned pellets equivalent to 14.1 million tonnes in the UK in 2019.

There is certainly a place to question the contribution of home wood burning to climate change and air pollution – and for everyone with a woodburner or open fire to consider how they can reduce its impact. But we cannot do so without also considering the damage caused by the large-scale biomass practices of Drax and others – and the policies that support them.