Wood burning stoves, the great debate

Why do stoves remain popular with the public when they are a major source of indoor and outdoor air pollution?

You’ve just come back from a long walk, the house is cold so you light the fire and sit down with a cup of tea to read your book. To many people, this probably sounds like the perfect way to spend a lockdown afternoon, but in fact, there is something quite sinister going on here. 

According to the Department for Environment, Food and Rural Affairs (Defra), wood and coal fires are the single biggest source of particulate matter (PM2.5) pollution in the UK. Even in London, which has had smoke controlled areas for more than 60 years, researchers at King’s College London found that wood burning was responsible for between 23 – 31% of all PM2.5 pollution. 

Because of their size – about thirty times smaller in width than that of a human hair – PM2.5 is one of the most dangerous air pollutants when it comes to human health. These tiny pollutants can travel deep into the respiratory tract where they can lead to numerous health problems, from asthma, lung cancer, cardiovascular disease, dementia and pregnancy loss. 

Yet despite the carcinogenic properties of these particles, lighting up a wood burning stove or an open fire remains to be hugely popular, indeed an estimated 175,000 wood burners are sold in the UK every year. 

To get to the crux of why this is the case and in a bid to understand the bigger picture, Air Quality News got in touch with Dr Gary Fuller, an air pollution scientist at Imperial College London, and whose book ‘The Invisible Killer’ addresses this issue in detail. 

‘I think to start with, we need to understand this whole phenomena, and to do that we need to look not just at the quantitative science, but also at the social and behavioural reasons as to why people are using wood burning stoves and open fires in the first place.

‘Let’s face it, looking at flames is completely brilliant, it’s wonderfully relaxing and I think many people also believe that it brings them close to nature, but the implications on air pollution are enormous and that cannot be ignored.’ 

In recent years, the discourse around wood burning stoves has focused on them being a more environmentally-friendly option when it comes to heating your home.

Indeed, the Stove Industry Alliance (SIA), the industry body representing the wood burning stove industry, have gone so far as to say that burning wood is a ‘carbon neutral heating option.’

‘I know it’s slightly debatable,’ said Morley Sage, chair of the SIA, ‘but if you use locally sourced wood then you’re almost certainly in a carbon neutral situation.’

However, this situation is far from clear cut and measuring carbon dioxide (CO2) emissions remains incredibly difficult, as Gary Fuller explained: ‘When you look at the whole life cycle of burning wood, you’ve got to say what is the counterfactual?

‘If we compare a scenario where you heat your home with gas and leave the tree in the forest, to one where you chop down a tree and leave the gas unused, then what happens to the CO2?

‘When you set fire to wood in your fireplace, you’re automatically releasing carbon that has been sequestered for many decades, and it will take the ecosystem a long time to reabsorb that carbon. So you see, the debate becomes not which one is better, but in which time window are they better.’

This lack of clear communication goes beyond the CO2 impacts of wood burning stoves, but also extends to their air pollution impact. Later this month, the government will begin to phase out the sale of coal and wet wood, which according to Defra are ‘the two most polluting fuels.’ However, Dr Gary Fuller has warned that ‘this is possibly a very contradictory signal.’

‘You could look at this and say yes, it will help the problem,’ said Gary.

‘But then are you saying that it’s completely acceptable to burn dry wood?’

‘I raise the concern that in five or ten years time will our pollution problem actually worsen because people will see this as a message that they can go out and either open up an old fireplace or buy an old wood burning stove, and as long as they’re burning dry wood, then the industry seems to imply that it’s completely fine.

‘Indeed, research we conducted in London revealed that the extra PM2.5 that was coming from wood burning stoves was seven times greater than the air pollution reduction from the first two phases of the low-emission zones. So you can see that this mixed messaging runs the risk of undoing much of the work and investment that we’re putting into other areas.’

However, as Morley Sage highlighted, there is an emissions hierarchy when it comes to the fuels we burn and the stoves we use.

‘If you look at a new Ecodesign compliant stove it will produce on average 90% less emissions than an open fire, and 80% less emissions than the average 10-year old stove.’

‘Our website highlights the benefits of replacing older stoves and when that isn’t a possibility then we encourage consumers to ensure that they’re burning the right fuel, meaning fuel that is in line with the government’s new law.

‘The overall message that we’re trying to get across is that it’s all about having the right appliance, the right fuel and then burning it in the right way.’

However, according to a 2015 government survey, in London, 68% of people who were burning wood in their homes were using open fires, the most polluting of all appliances. The fact is, wood burning stoves and open fires have an extremely long life span, upwards of 20 years, and replacing them can be very expensive, a brand new Ecodesign approved stove costs anywhere from £500 – £2,000, without considering installation costs.

As stated by Gary Fuller: ‘The turnover for solid fuel devices is really really long. So people are going to be making substantial investments in stoves and it’s going to be really hard to say that they shouldn’t use them.

‘Yes if people were to take their open fire, and replace it with something that’s more modern, it would mean a reduction in emissions.

‘But even the best stoves still emit air pollution, in their biomass report, the Air Quality Expert Group found that burning wood in an Ecodesign stove was similar to the emissions from six Euro V1 HGVs. 

‘I think it’s important to recognise the benefit of risk reduction, but also to recognise that it’s not the answer.’ 

Morley continued to highlight that there are many other benefits of using wood burning stoves: ‘It’s also a form of heating which assists with fuel poverty, it is not generally bought on credit and it’s an affordable and a local space heater. 

‘There are also many other health benefits, wood burning stoves are a very calming focal point in the home, and at a time when stress and mental health are very important, they can have a positive contribution to that.

‘They are also good at circulating air in the house, which can also be beneficial for health.’ 

But in the midst of a respiratory pandemic, where air pollution has been linked to a greater risk of dying from Covid-19, the question remains, is lighting a fire and contributing to the wider air pollution problem the socially responsible thing to do. 

As Harriet Edwards, senior policy manager at the British Lung Foundation said: ‘We want to encourage people to really question if they need to use a wood burning stove, and if they are using one, then we encourage them to really think about the way they are using them. 

‘But the consumer information is just not out there at the moment and there’s a really big piece of work that needs to be done to change that. I think many people feel duped, they might have felt they were making a more environmentally-friendly choice and now they’re being told otherwise, we need to ensure that the public are given much clearer advice and information, because ultimately, no level of air pollution is safe to breathe in.’ 

There is clearly a gap in the information when it comes to wood burning stoves, and as shown the debate remains to be very heated, but whether they are contributing to air pollution inside your home or causing an air pollution problem to the wider community, there is clearly a need for clear communication to help raise awareness and highlight the air pollution impacts of these not-so idyllic wood burning stoves.

This article first appeared in the February Air Quality News magazine which is available to view here.

Leave a Reply

Your email address will not be published. Required fields are marked *