Burning Questions

‘I’ll maybe put a match to the fire,’ my father would say. The tentative phrasing belied one of the great certainties of my childhood. The fire was lit most evenings, except in high summer, but in Aberdeen you were sometimes glad of it then too. Our 1960s decorative brick fireplace was the heart of the household. It was there for warmth, but it had a significance beyond the heat it provided. It seemed to ease something, or enable something – a wordless sharing of domestic space. In the absence of a television (my Presbyterian parents disapproved of it), the fire supplied diversion. It was at the centre of our family circle every day when my father read the King James Bible and prayed. This might sound like the 1670s, not the 1970s, but it was on a footstool at the hearth that I learned to recite the Shorter Catechism. I knew the sight and sound of burning coal so intimately – the way it cracked and split, the way a flame found its way to the microjets of methane and oozing tar – that it was easy to visualise hell as a landscape of blistering rock.

At the age of four, I learned how to crumple a few sheets of the Press and Journal into the grate, to roll up others into tight overhand knots that would provide more lasting tinder, then to place kindling in a lattice that would support smaller lumps of coal. An unspoken rule dictated that one match from the Scottish Bluebell box on the mantel was sufficient. A second match was a failure. You could quickly get a good blaze if the draught was open from below and the living-room door was firmly closed, but the balance of air pressure in our suburban house could be tricky. We learned not to open the living-room door when the fire had just been lit because to close it again might send a cloud of smoke billowing into the room, an outcome even worse than a second match.

I still put this early firecraft training to work on many if not most evenings between October and March. We live inside the City of Edinburgh Smoke Control Area, which means that open fires are banned, as is house coal, but we are allowed to burn wood as long as it has less than 20 per cent moisture content and the combustion takes place in an authorised appliance – in our case, a Morsø Squirrel, twenty years old and a little rusty, but a more efficient and a less polluting technology than anything my ancestors used. I love our wood stove, not just the comfort of it but the work it demands: cleaning the glass with spit and ashes, the fire-setting and the fire-lighting, the slow coming to life, the tinkering with doors and vents in the early stages of the burn cycle. I like to invert the bottom-up method I was taught (paper, kindling, then coal or logs on top) by placing the logs at the bottom, then letting the embers sink down. My parents wouldn’t have approved, but since they’re dead I don’t have to worry about that, or about how many matches I use. In fact I’ve moved beyond matches: I strike sparks from a ferrocerium rod onto tumble dryer lint. I’m a twisted fire-starter.

This winter, the prohibitive cost of gas means the stove might get a bit more use. Other households are clearly thinking along similar lines. Wood stove sales in the UK have risen 40 per cent; 35,000 units were sold between April and June. The hardware chain Toolstation recently reported a 30 per cent rise in chainsaw sales, suggesting that people are thinking about using salvaged wood to burn at home. With firewood prices rising steeply across the UK and Europe, the World Economic Forum is even talking about making woodstores an economic indicator, a sign of adaptation to energy independence from Russia. The Putin-supporting leader of Belarus, Alexander Lukashenko, was filmed chopping logs, trolling his European counterparts by saying that in the absence of Russian gas, EU citizens couldn’t be too choosy about whether fir or birch made better firewood.

My own woodstore isn’t as full as I’d like. I draw the line at felling trees – I’m an academic not an arborist – but I source, buck, split, stack and season my own logs. To do this I have acquired three axes, two hatchets, some log tongs and a Stihl chainsaw (apparently I use the same axe as Lukashenko, a Fiskars X25). Last January, my reserves were replenished by Storm Malik, which brought low my neighbour’s forty-foot Leylandii. I missed the crash but the aftermath was a joy. Aside from the additional daylight, a little negotiation afforded me the trunks and the chance to build two holz hausen circular woodpiles copied from Lars Mytting’s Norwegian Wood, the armchair forester’s bible. Even when the stove is not in use, there is pleasure in fuel-gathering and anticipation.

But these preparations are also attended by a smouldering doubt. It’s hard to ignore the headlines: ‘Wood burners cause nearly half of urban air pollution cancer risk’; ‘Avoid using wood burning stoves if possible, warn health experts’; even ‘Air pollution can make you BALD.’ On the face of it, there’s a discrepancy between the degree of scientific concern about air quality and the fact that life is so much less smoky now than it was in my childhood. The change is evident in the data, especially in relation to the most harmful fraction, PM 2.5 – particulate matter under 2.5 microns (ultra-fine ground coffee is 40 microns, and a typical human hair between 75 and 100). PM 2.5 emissions in the UK have been falling steadily for decades. There has been an 85 per cent reduction since 1970, largely as a consequence of the demise of coal and tighter controls on emissions from vehicles. The scientific consensus is that there’s no safe level of air pollution, and the hard-won decline in PM 2.5 from vehicles has been counteracted by our abiding love of the domestic fire.

Research on the health effects of PM 2.5 shows that exposure to fine particulates affects just about every organ in the body. They are thought to bear some responsibility for strokes, cardiac problems, chronic obstructive pulmonary disease, cancers in the trachea, bronchus and lungs, aggravated asthma and lower respiratory infections, as well as type 2 diabetes and dementia. Asthmatic children and old people are particularly vulnerable. The only escape is geographical: maps of the UK’s ambient air quality show much higher PM 2.5 concentrations in South-East England, and especially in London. You can look up the data for your own home by submitting a postcode to the site addresspollution.org. The LRB offices, for instance, are in the 99th percentile for pollution levels in Britain (annual average PM 2.5 on Little Russell Street is 13.27 micrograms per cubic metre, more than double the World Health Organisation limit of 5 µg/m³). A UK government report by the Committee on the Medical Effects of Air Pollutants estimated that PM 2.5 was responsible for 29,000 ‘attributable deaths’ per year – just a few thousand fewer than the number of deaths from Covid in the UK in 2022.

How much of this is a result of domestic wood-burning? The answer isn’t straightforward and has undergone significant revision in the last year. In 2019, the Department for Environment, Food and Rural Affairs (Defra) held domestic wood and coal-burning responsible for 38 per cent of the UK’s PM 2.5 emissions. After new data was taken into account in February 2022, this estimate was cut to 17 per cent – still higher than road transport, at 13 per cent. A recent Defra-funded paper by Anna Font and others at Imperial College analysed atmospheric data to compile long-term trends in the amount of particulate matter generated by wood-burning and found a significant and ‘unexpected’ downward trend of PM 2.5 emissions in four out of five test sites, two of them in Scotland, one in London and two in rural South-East England. As the number of households burning wood is relatively stable at around 8 per cent, one likely explanation, the researchers suggest, is that more efficient modern wood stoves are replacing heavily polluting open fires.

Particulate matter is both oddly remote and unhealthily proximate. It’s not something most of us check as we do the temperature outside. A few months ago, I bought a £60 hand-held monitor after reading about a study carried out by the Universities of Sheffield and Nottingham that suggested wood stoves were a threat to the health of their users. Was I poisoning the kids? The authors of this paper, published in Atmosphere, investigated indoor emissions from ‘real world’ stove use by recording peaks of PM 2.5 (average readings can often disguise short ‘flooding’ events, when the stove door is opened to put in more fuel, for example). Sure enough, they found that people using stoves were exposed to very high levels of PM 2.5 (between 27 µg/m³ and 195 µg/m³) after they inserted a log. My own readings from the sensor haven’t been quite so worrying. I have seen peaks as high as 150 µg/m³ – not good – but they have lasted only seconds, quickly dropping to background levels. Perhaps my upbringing has made me a disciplined stove user (I’m obsessed by optimum vent use). Or perhaps I’m guilty of ‘participant reactivity’, modifying my behaviour because I’m also in the process of monitoring it. But even when I’ve incautiously thrown open the stove door and raked the charcoal, the level produced hasn’t been very frightening.

In the first few days using the sensor, I was like a Victorian clergyman with a new rain gauge, absorbed in the innocent joys of measurement. Then it led me to where the real horror lay: the kitchen. Our cooker hood broke many years ago and since we hated the noise it made we didn’t have it repaired. The room has quite a low ceiling so there’s no effective escape for cooking emissions from our gas hob. Literally any kind of cooking produced a much more alarming level of PM 2.5 than anything from our wood stove. Pasta: bad. Pan-fried chorizo: reckless. Toast? Maybe not. Our oven isn’t very clean, but roasting a chicken sent PM 2.5 above 50 µg/m³ and, unlike with the wood stove, the level took an hour to drop. None of this would come as a surprise to aerosol researchers, but it was a revelation to me.

Julie Cupples at Edinburgh University has shown that the literature on air pollution is laden with ideas of purity and contamination, as well as the desire to disentangle nature (background PM 2.5) from culture (its anthropogenic sources). It’s a productive distinction in many ways, but it isn’t one that was apparent to distant generations of my rural family, for whom ‘natural’ fresh air was unknown. In the long winter months inside, they inhaled smoke and exhaled prayer.

Other difficulties in assessing the significance of PM 2.5 are evident when it comes to the reasons people continue to use a wood-burning stove. Clean air advocates dismiss the burning of wood as a merely recreational or aesthetic pursuit, while the Stove Industry Alliance highlights the efficiency of modern stoves, especially compared with sources of outdoor wood-burning: bonfires, barbeques, pizza ovens, jacuzzis, chimineas and the like. (I’m guilty here on two counts: I feed the brazier on the Universities and Colleges Union picket line, and I turned a washing machine drum into a lockdown garden fire pit – I learned how from a five-minute YouTube video; it took me six and a half hours.)

For many people, however, the fire has more personal associations. In my case, it tells the story of how my father’s family became modern. My great-grandparents pulled down their blackhouse in 1885, bidding farewell to the shame of the ‘common roof’ – common, that is, to humans and livestock. In a blackhouse, a hole in the thatch vented the fire on the floor, and the rafters dripped with peat reek and brown tar. My great-grandparents reused the blackhouse stone to build an archetypal Highland croft house with a chimney at each end, one for everyday use and the other for the room that was used only for important visitors like the minister. This transformed the indoor air quality, but since they continued to use peat for cooking and heating, there was still a residue. By the early 20th century, my grandfather had swapped the croft for a job on the railway and the promise of a brick new-build with an offset chimney, a clean mantle and, later, a back boiler for hot water. The future was coal and it came from a co-operative, the Highland Railway Servants’ Coal Committee, which brought fuel to the workers without merchants taking their cut (my grandfather was the treasurer of the committee).

Something in all this made my father feel ambivalent about gas central heating. He tended to his open fire like a cherished pet and would buy half a ton of Easington or Shilbottle, colliery names that he took to be hallmarks of quality. Sometimes he would mix the coal with smokeless anthracite-based ‘ovoids’ like firebrite or phurnacite, but any improvement in air quality was offset by the dross he used to bank up the fire, streaming thick smoke up the chimney and out into the night air. All this was legal because Aberdeen lay outside the Smoke Control Areas set up by the 1956 Clean Air Act. The restrictions improved public health but have now fallen into abeyance. Pollution from the open burning of wood, if not coal, is widespread even inside Smoke Control Areas. The government’s most recent survey on domestic wood-use recorded that 40 per cent of people burning wood were doing so in an open fire. In London, the figure was 70 per cent.

One of the odder symptoms of the reduction in the use of coal in the 1970s was the proliferation of electric heaters with moulded plastic coal and flame effects projected from a bulb and a fan that cast rotating shadows. None of them looked anything like a real coal fire, but that didn’t seem to matter. The twin electric bars were expensive to run so sometimes people turned on the illuminations without the heat. You can now buy wall-mounted LED flame-effect fires. There are electric log fire baskets that use ultrasonic technology to vaporise water into an illuminated mist, giving the effect of flames and smoke, though not heat. There are bioethanol stoves that give some heat – only a fraction of what’s produced by my stove – and emit nothing more sinister than carbon dioxide and water (although bioethanol production itself is not always benign). You just squirt the colourless fuel into a reservoir, ignite with a long-reach electric lighter and relax in front of the fat licks of yellow flame. I read one article on non-polluting stoves which concluded that the most cost-effective solution was to stream ‘Fireplace for Your Home’ on Netflix.

I still light our stove, though not without misgivings. I may upgrade to a more efficient model and will switch on the PM 2.5 sensor to test the difference, though really it’s just an amulet, safeguarding the future while the sparks catch.