Do wood-burning stoves produce less harmful emissions than heat pumps?
A LEADING voice on Highlands issues has calculated that heating rural newbuilds with wood-burning stoves could result in much lower emissions than using heat pumps.
Magnus Davidson, writing on X, said: “Using 2023 figures, if all new houses in the Highlands and Islands burned wood for domestic heat rather than used a heat pump, CO2e emissions from wood-burning heating would be 88% lower than the heat pump system.”
His comment was published in the midst of intense debate over the newly-announced ban on woodburning stoves in newbuilds, and raised questions over what burning wood might mean for carbon emissions and net zero.
Mr Davidson is among many who have raised key issues around the complex issue of how to heat Scotland's homes, in particular new rural homes – and the Scottish Government's policy around this.
Key questions include: can burning wood actually be close to carbon neutral? And is the inclusion of woodburning stoves in the ban more about climate, or the particulate pollution they produce?
Are wood-burning stoves lower emissions than heat pumps?
MR Davidson claims so and has made calculations on the number of newbuilds, the emissions intensity of electricity and average domestic heat demand using data from 2023.
To make his calculation he also assumed that burning wood is a carbon-neutral process. “This is due to wood effectively emitting carbon it had already sequestered, so somewhat net neutral, while UK Grid remains powered by some fossil fuel.
“These numbers account for heat pump COP and use UK Government emission factors, using average domestic heat demand figures.”
He calculated that the fuelling of newbuild wood-burning stoves would require 1,750 hectares of woodland (0.006% of total woodland cover in Highlands).
He is not, it should be noted, against heat pumps, which he said “are truly magical and we should shift as much as possible to them – especially in the Highland and Islands which is a massive net exporter of renewable electricity”.
But is burning wood really carbon neutral?
THE answer to this question isn't simple and has been the subject of much debate. The argument that burning wood is carbon neutral is based around the idea that wood is a renewable resource which sequesters carbon.
When you burn a tree and plant another, over time the result is carbon neutral.
However, a key issue with this is time frame.
We burn a tree over a short period, but it takes much longer to grow back and if the carbon dioxide released by that burning is significant there is a problem given that, to mitigate the climate crisis, cuts need to be made quickly.
A 2022 study in the Bulletin of Atomic Scientists stated: “Wood emits more carbon dioxide per kilowatt-hour than coal and far more than other fossil fuels. Therefore, the first impact of wood bioenergy is to increase the carbon dioxide in the atmosphere, worsening climate change.”
The paper also dismissed the idea that it was carbon neutral due to sequestration by newly-planted trees, saying: “Forest regrowth might eventually remove that extra carbon dioxide from the atmosphere, but regrowth is uncertain and takes time, decades to a century or more, depending on forest composition and climatic zone time we do not have to cut emissions enough to avoid the worst harms from climate change.”
The research is not alone in concluding this. One Finnish study found that of all common heating methods in Finland, the typical Finnish stove was the least climatefriendly option. When French researchers looked into the issue of how to balance the carbon produced by burning with regrowth, they found “no single solution” that worked in a way that also met energy targets.
What if you gather your own wood and plant your own trees?
THE wood-burning stove question is a reminder that the answers may be different according to where a person lives.
The question, after all, is not whether everyone should be able to have a wood-burning stove, but whether, in rural areas, such heating systems should be considered appropriate enough to continue to allow their inclusion in newbuilds, even as they are banned in urban areas.
Some argue that it is possible for those living in close relationship to the land to sustainably burn wood.
Others talk of burning dead, fallen wood, which would have decomposed releasing greenhouse gases anyway. One says on its website: “Burning correctly seasoned wood on an Ecodesign stove can produce less carbon dioxide than if the wood was left to rot on the floor of a forest.”
But leaving it to rot on the forest floor has its own benefits to the local ecosystem and increasingly dead fallen wood is being seen as important for biodiversity reasons.
The Scottish Government has been quick to point out that the ban is only for newbuilds – those already with stoves can keep them, and they can also be installed in older homes. With newbuilds there is also a provision that allows an exemption for emergency heating.
If a key issue is particulate matter, shouldn’t we have different rules for rural areas?
STUDIES have shown wood-burning stoves create pollution that is bad for health. Earlier this year, it was reported that a rise in harmful emissions of particulates PM2.5 and PM10 from stoves had helped undermine decreases in pollution from road and energy in the UK.
However, it's worth noting that the Highlands and Islands has significantly lower PM2.5 than the central belt, making a possible argument for banning stoves solely in urban areas affected more by such pollution, and not rural areas.
But, it should be noted, rural dwellers are still impacted by particulates – since they are released into their homes every time they open their stove doors.