How bad is wood-burning? And why do people do it?
As an environmental activist and air quality researcher, I am often confronted by people who burn wood, even other activists. I have even been on television to argue against wood-burning. And, with a growing awareness of air pollution indoors and in neighbourhoods, some have chosen to do away with their wood-burning activities, but others have not. Why is this?
Wood-burning pollution is increasing
We know now that wood-burning stoves are increasing in sales in the UK, with greatest sales in the richest parts of the country. Yet, the government refuse to ban them despite the Chief Medical Officer’s report saying the overall declines in air pollution are concurrent with ‘an increase in emissions from domestic wood-burning’, that ‘domestic burning is a major source of our national emissions of fine particulate matter’, and that air pollution causes the death of ‘between 26,000 and 38,000’ people in England per year.
Firstly, a definition: PM2.5 is any particulate matter that is 2.5 microns or smaller. This is an important size because it reaches the lower lung. Particulate matter is measured as μg/m³, which is the concentration of an air pollutant, and stands for “micrograms per cubic meter of air”. The UK government will often say things like ‘annual emissions of PM2.5 have fallen by 85% since 1970’, to demonstrate that particulate air pollution has reduced. But even though total PM2.5 is decreasing, PM2.5 from wood-burning are increasing, effectively replacing the phasing out of coal.
Over 1 million wood stoves were bought between 2010 and 2015 and, to justify the investment, wood is often burnt every day. This wood smoke drifts into neighbours’ houses so lots of people are exposed.
One chimney pollutes a street
We rightfully campaign for clean air, but many seem totally unaware that domestic wood-burning is the largest source of particulate pollution in the UK. Only 8% of the UK’s homes burn wood, but this accounts for around 21% of the total PM2.5 emissions, whereas all traffic on the UK roads produces 13%. This is a growing issue in the UK, where wood-burning contributed to 75% of domestic combustion emissions in 2021, up from 70% in 2020, compared with just 3% in 1970.
A pilot study in Islington, London was made to find hotspots of air pollution. Scientists carried air quality sensors around a residential area on Friday, Saturday and Sunday evenings, the most popular times for home wood-burning. They found wood-chip boilers and homes burning wood to be responsible for most of the particulate pollution in residential streets.
Wood-burning pollutes homes
Wood-burners triple the level of harmful pollution particles inside homes and should be sold with a health warning.
A 2020 study in Sheffield, UK analysed data collected every few minutes from pollution monitors in people’s homes and in total assessed 260 uses of wood-burners. The results showed the burners were usually lit for about four hours at a time, and during this period the level of harmful particles in homes was three times higher than when stoves were not being used.
During those four hours, average particle levels rose to between 27 and 195 μg/m³. The World Health Organization guideline for PM2.5 is 15μg/m³ over 24 hours, and 5μg/m³ as a yearly average.
The rich are buying stoves
I contacted the Stove Industry Alliance (SIA), who ‘promote and explain the benefits, wellbeing and environmental advantages of wood-stoves as heating appliances’, to ask about the sales of stoves in the UK. From a recent press release they issued, there were just over 35,000 sales of wood-burning stoves in April-June 2022. This grew to just over 57,000 in July-Sept 2022. Perhaps this was due to rising gas bills, but at around £500 plus installation costs, a wood-burning stove isn’t for people who are short of cash. The rise in wood-burning stove purchases are in affluent households who have alternative sources of heating.
However, the SIA often point to open fires as the problem. “It is widely accepted that up to 70% of all wood fuel burnt indoors in London is on open fires, the use of which (to burn wood) is illegal in a [Smoke Control Area]” they told me on Twitter. “Modern stoves … make up a very small % of the PM” they said in another tweet.
Focussing on London, rather than England, was cherry-picking. The government reported: “Open fires [are] estimated to account for around 24% of PM2.5 emissions from the domestic combustion sector, with wood-burning stoves accounting for around 76%”. The Stove Industry Alliance didn’t respond to me pointing this out to them. No surprises there, as they represent sales of approximately 75–80% of the UK stove market.
Home-style magazines and renovation programmes targeted at the most wealthy often show beautifully decorated homes with a wood fire. Country Living wrote “the Government has announced plans to phase out the sale of coal and wet wood in England between 2021 and 2023. This means that suppliers will need to offer cleaner, more eco-friendly burning materials — such as dry wood”. Notice the language here — ‘cleaner’ and ‘eco-friendly’. Although it may be true that washing yourself in horse manure is cleaner than washing in a bath of crude oil, neither are clean.
The richest burn the most wood, the poorest suffer the worst air pollution
A 2020 report produced for the UK government providing results from a face-to-face omnibus survey of over 46,000 people across the UK found that almost half of all indoor burners (46%) were from the highest AB social grades. It also showed a breakdown of why people burn wood. The greatest reason was ‘socialising and creating a homely atmosphere; it is a lifestyle choice for this affluent and largely English segment who burn least and could be persuaded to burn less or differently’. It stated ‘of those who burned indoors, 21% reported household incomes of over £50,000 per year’. Almost all indoor burners lived in a house (98%) rather than a flat or maisonette, and almost all indoor burners classified themselves as ‘white’ (97%). Only 3% of the respondents claimed that they found it ‘very difficult’ to pay for their energy costs.
The UK government uses the minority to avoid bans
The UK government’s 25-year Environmental Improvement Plan released in January 2023 stated “We are not considering a ban on domestic burning in England. The UK government recognises that some households are reliant on solid fuel burning as a primary source for heating, hot water and cooking, with this in mind government is not seeking to ban burning”.
In January 2021, experts at Asthma UK and the British Lung Foundation asked people to use wood-burners only if they had no alternative source of heat. Only 6% of the UK population rely on heating their homes in other ways, and this includes heating oil and liquified petroleum gas. The UK government also states that wood-burning stoves ‘are now an additional form of heating for many households; for a minority they may be the sole heat source.’ Rather than supporting this minority of homes with insulation and heat pumps, the UK government chose to use them as an excuse to allow the affluent areas to keep polluting their neighbourhoods.
Emissions from wood burners result in almost £1bn in health costs a year and are responsible for nearly half the cancer risk caused by urban air pollution. Imagine how this financial cost and health burden could be reduced if the government helped those reliant on burning wood to insulate and heat their home in a cleaner way.
The UK government’s own reports show that the South East has the highest concentration of households that burn wood in England, and that they are the most well connected region of England to gas heating. The South East region contains the greatest number of Tory voters of all regions in England.
Most people want wood-burning bans
A report in February 2023 by the Guardian showed that more people support a ban of wood-burning than people who support their use. A poll of 1,258 people on 15 and 16 February showed that Londoners were most keen to ban wood-burning, as were the over-75s across the country were the most supportive of wood-burning bans in cities, with 58% in favour and 32% opposed. The most in favour of keeping wood-burners were Scotalnd and Wales, who are least well-connected to the gas network, and may therefore rely more on solid fuels, such as wood.
In fact, the Mayor of London effectively banned wood burners in new and refurbished homes, where the guidance encourages developers to meet air quality standards by installing solar panels, electric heat pumps, cycle storage and electric vehicle charging. The guidance also requires an overall increase in biodiversity, with the inclusion of green roofs, new trees and hedges and wildlife-friendly landscaping.
Drying wood in gas-powered kilns
The UK government has stated in the 25-year Environmental Improvement Plan that ‘burning a dry log can reduce emissions by 50% compared to a log which has not been dried’ and that it will ‘ban the sale of wet wood in smaller packets’. Where drying your own logs takes 2–3 years, companies selling kiln-dried wood burn gas or use electricity. So, rather than using the gas or electricity to directly heat a home, it is used to dry logs that are burnt, releasing far more air pollution than a gas boiler or electric heater would.
Collecting wood from forest floors
Stag beetles are in drastic decline in the UK, and this is not helped by people collecting deadwood from forest floors. Stag beetle larvae take between 3–7 years to develop in dead and decaying wood, and the tidying up of parks, gardens and green spaces and the removal of tree stumps and deadwood is contributing to their decline. Around 650 UK beetle species are thought to require deadwood at some point in their lifecycle, and without deadwood the beetles have nowhere for their larvae to grow. Stag beetles are a priority species for conservation in the UK, it has endangered or protected status and has been included and is classed as a ‘European Protected Species’. Providing decaying wood for years is necessary for their survival.
Deadwood recycles nutrients back into the soil, provides food and nurseries for rare animals, and hosts spectacular collections of fungi. Environmentalists would be best leaving this wood on the forest floor to allow the UK’s dwindling wildlife the opportunity to recover.
Open fireplaces
People are unlikely to buy a new fireplace when they have a traditional-looking 100-year-old one in their home. As the SIA stated, 68% of wood-burning in London homes is using an open fireplace, which is the least efficient way to burn wood. A UK survey from 2016 showed wood-burning produces 2.6 times more particle emissions than traffic exhaust.
Modern stoves produce a quarter of the emissions of an open fire, with air coming in at specific points to ensure highest rates of wood combustion. Stoves sold in Europe must meet Ecodesign standards that set limits on how much smoke a stove can produce. But this limit is still higher than 18 modern diesel cars and produce 450 times more particulate pollution than gas heating, compared to older stoves, that are still in use but banned from sale, producing 3,700 times more. Additionally, there is a big difference between test performance and real-world emissions. A 2015 study showed that the amount of smoke produced by a wood stove can produce 16 times over the approval limits, with the biggest factor being the way that the person lit the fire.
Deforestation
Burning wood ‘feels’ environmentally friendly. Rather than burning fossil fuels, wood feels like a renewable source, which sucks up carbon from the atmosphere and provides homes for birds and insects along the way. Unfortunately, this wood is from either rich woodlands or monocultures that have poor biodiversity. Due to increased demand, the UK is the third largest importer of firewood in the world, and this increases chances of plant diseases and insects that can be inadvertently brought along with the firewood, which can cause serious problems for UK woodlands. Latvia exports a significant proportion of firewood to the UK, and they have observed sharp declines in forest birds as felling increased.
In a world where forests are being cut down at a rate of one football field every two seconds, chopping down trees for wood-burners is one of the last things Europeans want to be doing. Instead, we in the UK need to be serious about replacing wood-burners with heat pumps and requiring government subsidy to help this transition.
Government incentives can work. A government scheme in Tasmania in 2001 provided people with A$500 to switch to electric heating and the number of wood-burning homes dropped from 66% to 30%, seeing winter death rates fall by 11%.
Arsenic
There is a recently observed spike in arsenic in the UK’s air, attributed to people burning waste wooden fence panels, pallets, old furniture, doors, door frames and construction wood salvaged from skips that contains arsenic. Back in 2020, a UK government survey showed 9% of people burned waste wood at home, and this is likely to have increase dramatically with increased gas prices. Construction timber (the type with a green tinge) is treated with ‘chromated copper arsenate’ (CCA) to preserve it from microbes and insects. The arsenic is what kills the microbes and insects, and what is released into the air when it is burned. The release of arsenic from burning treated wood is not widely known, which demonstrates the government are either out of touch with what is happening, or that they don’t care about what is happening enough to act.
Arsenic pollution from burning wood in a crisis is not a new thing. The 2008 economic crisis that crippled Greece resulted in many people burning waste construction wood and, by 2015, the city suburbs saw a 30% increase in particle pollution and increased arsenic in the air. Lead was also found in the air as people burned their lead-painted furniture, which is so toxic that even low doses can lead to lifelong consequences, and childhood exposure adversely affects personality. A 2021 study showed people who had spent childhoods in areas with more lead in the air were less agreeable and more neurotic.
New government guidelines don’t make sense
The UK government’s 25-year Environmental Improvement Plan released in January 2023 states they will ‘Tighten the limits that new stoves in Smoke Control Areas must meet, reducing the limit from 5 grams of smoke per hour to a maximum of 3 grams per hour’. But smaller particles, which have less mass, are more harmful. The particle number should be used in the limit, not the total mass, because total mass has no bearing on how many particles there are. In the same way, 1 kg of apples and 1 kg of sand have the same mass but vastly different numbers.
A back-of-the-envelope calculation:
- 3g of smoke particles that are 2.5 microns = 3400 billion particles
- 3g of smoke particles that are 10 microns = 53 billion particles
Additionally, enforcing such a limit would be incredibly difficult. English councils have issued only 17 fines over six years, despite more than 18,000 complaints, as it is difficult and expensive to prove guilt and then take people to court.
Smoke control areas are also not ubiquitous. You need to check if your area is actually included. And even then, you can use outdoor barbecues, chimineas, fireplaces or pizza ovens in smoke control areas. Bonfires, perhaps the most polluting of all, are allowed in smoke control areas.
- emit a substantial amount of smoke from a chimney
- buy or sell unauthorised fuel for use in a smoke control area unless it’s used in an ‘exempt’ appliance (appliances which are approved for use in smoke control areas)
Overall…
I would hope that any environmental activist, environmentally conscious person, or indeed anyone reading this article will come away knowing that:
- wood-burning causes around 21% of total PM2.5 air pollution in the UK, and 75% of domestic emissions;
- between 26,000 and 38,000 people in England die from air pollution every year;
- collecting wood from forests is wiping out insects, and burning treated wood is polluting the air with arsenic;
- experts at Asthma UK and the British Lung Foundation ask people not to burn wood unless they have to;
- burning wood affects breathing and general health of neighbours who have to suffer the consequences of people’s choices;
- 92% of people who burn wood made their decision based on aesthetics, tradition, supplement, or simply to save money; and
- alternative forms of heating, such as heat pumps or underfloor heating properly installed, and properly insulating homes must be more widely adopted.
