About time this started to go mainstream.
https://www.newscientist.com/article/2119595-wood-burners-london-air-pollution-is-just-tip-of-the-iceberg/

By Michael Le Page

Last week, air pollution in London soared to heights not seen since 2011. The usual suspects were named and shamed, including traffic fumes and a lack of wind. But joining them was a surprising culprit.

“We think about half of the peak was from wood smoke,” says Timothy Baker, part of a team at King’s College London that monitors air pollution.

The trendy log-burning stoves producing much of this pollution are marketed as a source of renewable energy that can cut fuel bills while helping reduce global warming. But recent findings suggest they pose a serious threat to the health of their owners, and are also accelerating climate change in the short term.

If nothing is done to discourage log burning in homes, it could become the biggest source of air pollution in cities like London. In the UK as a whole, wood burning is already officially the single biggest source of an especially nasty form of air pollution.

“I love sitting by a log fire as much as the next person but maybe we need to think again before it’s too late,” says climate scientist Piers Forster of the University of Leeds, UK.

Air pollution is awful for our health. The smallest particles get into our blood and even our brains, increasing the risk of many disorders including heart disease.
Natural killer

Children are especially vulnerable: high pollution levels impair their lung and brain development. Air pollution from all sources is estimated to cause some 10,000 premature deaths a year in London alone, where it frequently exceeds legal limits.

Wood smoke may be natural, but it contains many of the same harmful substances as cigarette smoke. It’s a massive killer worldwide, causing as many as 4 million premature deaths every year through indoor air pollution.

In the UK, however, the problem with pollution from wood fires was thought to have been solved by clean air laws introduced in the 1950s, which banned wood burning in open fires in cities. “The official view is that residential wood burning is a thing of the past,” says Gary Fuller of King’s College London.

Yet logs can still be burned in officially approved stoves in cities. Sales of these stoves have soared in the past decade, rising to nearly 200,000 a year. They are marketed as a way for people to drastically reduce their carbon emissions and save on fuel costs.

Even modern stoves described as “low emission” are highly polluting. And in an echo of the diesel car emissions scandal, measurements during actual use in homes show that the stoves produce more pollution than lab tests suggest.

In the “smokeless” fumes coming from the chimney of a house with a modern “eco-friendly” wood burner, Kåre Press-Kristensen of the Danish Ecological Council has measured 500,000 microscopic particles per cubic centimetre. The same equipment finds fewer than 1000 particles per cm3 in the exhaust fumes of a modern truck. The wood stove was certified as meeting Nordic Swan Ecolabel emission standards, which are stricter than the ones stoves in the UK have to meet.
Big in London

What this means is that a small increase in wood-burning stoves can produce a big increase in pollution. In Copenhagen, a city of 600,000 people, just 16,000 wood stoves produce more PM2.5 pollution – the most dangerous particles, smaller than 2.5 micrometres – during winter than traffic does all year round, says Press-Kristensen.

Wood burning is becoming a big problem in London, too. In 2010, when Fuller analysed particulate pollution to discover its source, he found that 10 per cent of all the city’s wintertime pollution was from wood.

There are many reasons to think that figure is higher now. A 2015 government survey found that domestic wood consumption in the UK was three higher than previous estimates, with 7 per cent of respondents reporting that they burned logs. “Wood consumption is increasing substantially,” says Eddy Mitchell at the University of Leeds, UK.

When he, Forster and others fed the data on wood consumption into a computer model of air pollution, their conclusion was disturbing: PM2.5 pollution from residential stoves is soaring in the UK (see diagram, below).

“There is a real risk that if we have a lot more residential wood burning then it could undo our other efforts to control air pollution,” says Fuller.

The harm far exceeds traffic pollution, he says. While people are exposed to high levels of traffic pollution mainly when travelling on busy streets, wood burning produces huge amounts of pollution where people live, when they are at home.
Indoor smog

Press-Kristensen has been measuring that pollution inside homes in Copenhagen. In three out of seven tests done so far, he has found very high levels. In one home with a modern log-burning stove, he found particulate levels several times higher than the highest ever recorded outdoors there (see diagram, above).

So do the health impacts outweigh any climate benefits? Astonishingly, there might not be any climate benefits, at least in the short term.

Burning logs is often touted as being carbon-neutral. The idea is that trees soak up as much carbon dioxide when growing as they release when burned.

In fact, numerous studies show that wood burning is not carbon-neutral, and can sometimes be worse than burning coal. There are emissions from transport and processing. Logs are often pre-dried in kilns, for instance.

Burning wood also emits black carbon – soot – that warms the atmosphere during the short time it remains in the air. Most studies ignore this, but Mitchell and Forster calculate that over 20 years – the timescale that matters if we don’t want the world to go too far above 2°C of warming – soot cancels out half the carbon benefits of all wood burning.

For home wood burning, the figures are even worse. “On a 20-year timescale, wood stoves provide little or no benefit, but they do on the 100-year timescale as they remove some of the long-term warming effect of CO2 emissions,” says Forster.

Press-Kristensen’s calculations show much the same thing. And both sets of findings almost certainly underestimate the problem, because they assume wood burning is carbon-neutral.

Defenders of wood stoves point out that there is a lot of uncertainty about how much black carbon is emitted when wood is burned and how large its effect is. Patricia Thornley of the University of Manchester, UK, thinks we need more real-world measurements before coming to conclusions.

But the uncertainties cut both ways. For instance, the effects of black carbon can be amplified if it is deposited on snow and melts it, exposing dark land that absorbs more heat. It’s possible soot from wood burning is contributing to the fall in spring snow cover in Europe, but it’s very hard to study.

More research is needed to pin down the precise climatic effects of wood burning, which can vary hugely depending on factors such as the source of wood and where the pollution goes. What is clear, however, is that burning logs in homes in towns and cities is not the best use of the wood we have.

It produces more pollution than wood-burning power plants that can be fitted with expensive filters, it produces that harmful pollution where lots of people live, and it has the least climate benefits, if any. “If we are going to burn biomass to meet climate targets, then we ought to do it in big, remote power stations,” says Martin Williams of King’s College London, who is studying the health impacts of the ways the UK could meet its climate targets.

Most researchers say it isn’t their role to make policy recommendations, but it would be best if cities like London discourage private wood burning before it becomes an even bigger health problem. At the moment, all the focus is on diesel vehicles.

Press-Kristensen doubts governments will ban wood-burning; France recently backtracked on a proposed ban on open fires, for example. Instead, he proposes installing heat sensors in chimneys and taxing people when they burn wood, with the level of tax depending on how polluting the appliance is.

Most importantly, governments must not ignore health impacts when deciding climate policies, says Press-Kristensen. “I like fires, but I have to say they are as polluting as hell,” he says.

Thinking of getting a wood-burner?

Wood-burning stoves are touted as an eco-friendly way to heat your house cheaply. But tests now show that even new, properly installed stoves can produce dangerous levels of outdoor and indoor pollution (see main story). What other options are there?

Consider instead
Stick with gas or oil for heating, and spend your money on insulation. Get a heat pump if you can afford it

Fake it
You can get the same cosy feeling from a log-effect electric or gas fireplace, the best of which are hard to distinguish from the real thing
Already have a wood-burner?

Here’s how to minimise its effects:
Don't burn scrap wood
Scrap wood or painted wood can release highly toxic substances such as arsenic when burned

Burn wood that's just right
Burning dry wood with a moisture content of about 20 per cent minimises pollution. But if wood is wetter or drier than that, pollution increases

Posted By: gyrogeardespite 50 kph winds

Will blow the smoke back down the chimney won't it.
Anyway, we have a 50% speed increase on that.

Proven but will the government bite this bullet?

Good article ST.

Useful introductory pages on the subject:

http://vair-monitor.com/2017/01/03/dust-pollution-overview/
http://vair-monitor.com/2017/01/19/measuring-dust-levels-measure-part-23/

Particulates are invisible. We need measurements.

Yes am fitting IWI as we speak! But only 25mm as have solid stone walls with dubious render, albeit painted. With the best will in the world my house is never going to be low energy and it is afterall 450m2 with 2 wrap-around balconies and solid stone walls over 3 stories. Plan is to just change my wood burner for a pellet (not chip) and keep my TS - why, because there's no way my in-laws can use my WB and I don't want to be tied to the house on a daily basis during the heating season for the rest of their lives!!!! Still not going to happen anytime soon. And yes will have to pay more for the fuel and become a hostage to the suppliers. I do worry though every time I smell the burner and the local landscaping does make this inevitable to some degree. So I might have a look at measuring those particulates to understand the scale of the perceived problem. First though must finish kid's bedroom before he leaves home!, restore the supports on the second wrap around balcony and make waterproof, and replace the main downstairs bathroom (original - ugg!)

Posted By: tonyProven but will the government bite this bullet?

Whats proven?

That unspecified wood burners burning unspecified wood can produce high levels of dangerous particulates?

Why not approach the problem the way pollution from cars has been tackled?

More advanced combustion systems and tighter controls on emissions. Control of the fuel would be difficult but if the environmental health had some teeth maybe they could stop obvious offenders.

I don't think wood is the right fuel to use in large conurbations but don't see why it cant have it's place in rural areas.

Posted By: BeauControl of the fuel would be difficult but if the environmental health had some teeth maybe they could stop obvious offenders.

The EHOs have teeth but they won't use them!!

Posted By: owlmanI found this bit of STs OP interesting.

"Burning dry wood with a moisture content of about 20 per cent minimises pollution. But if wood is wetter or drier than that, pollution increases."

I wasn't aware that DRIER wood was worse.

It may be in a open fire, as it burns a lot quicker so is harder to control. It can also burn too hot in SOME boilers giving more nitrogen dioxide (NO2). But I think most people would have to work VERY hard to have wood that is too dry.

I process and dry logs for my mum, comes in as 15 tonne loads of forestry thinnings, stacked as delivered in the open just off the ground, then cut and split as needed to replenish the bays in the barn for further drying, try to have 18-24 months in hand. Currently the mc is around 15% for whats being used. The "ready use" store also houses the pellet boiler, firewood stored in there over the summer will be down to around 12% by the time its needed.

There's certainly a lot more heat produced per kg using 15% as against 20% , it is certainly different controlling a dry burn, but the easiest way is to use larger pieces of wood

It had never occured to me that fuel could be too dry, i'll have a google and a read. Pellets I believe come in at around 7% ish, they are used in system installed under domestic RHI , because of the brand specified by the installer we've ended up with a boiler thats probably too large for the demand ( taking advice after installation , ideally we needed around 27 kw, boilers used by installer were either 25 or 40, aparently for rhi compliance we had to have the 40) it does however modulate down. Buffer size was increased to reduce cycling, during a burn only visible smoke or smell is during start stop of each cycle. But as noted inprevious posts this gives no real indication of possible pollutants.

I had better demolish THIS, then...

gg

I have 100mm of EPS 'EWI' on the roof, ventilated above to reduce heat built up in the summer. My walls are solid stone blocks of Tufo (https://en.wikipedia.org/wiki/Tuff) with internal walls or either solid stone or hollow block. Actually we do have granite type walls on the ground floor (half underground) with in fill. The tufo stone is very lightweight, soft and immensely hygroscopic. It is covered in a very hard cement render which is let's call it 'capillary open'. Whilst I have now painted it in 4 layers of good quality masonry paint it is hardly impervious to rain. In most of the rooms it is impossible to guarantee IWI'ing in such a way as to stop water vapour getting behind the IWI in some places - for example in bathrooms where there are major penetrations, and on the top floor (4 bed 3 bathrooms) in rooms where I am fitting the IWI after the suspended ceiling. So on other threads 25mm or so is about right to minimise the risks of interstitial condensation. Furthermore and I have 3 sets of inward opening French doors on the top 2 floors (plus lots of inward opening windows) and the wood window/door frame is made as part of the wood inside to outside reveal/shutter mount, meaning it is not sensible to try and move windows and doors inward, so I have to ensure they can open adequately (though yes I 'could' chamfer the IWI near the openings) and 25mm doesn't affect the opening to any noticeable degree. I also have original cast iron radiators some are substantially more than 100kgs empty - these are mounted on concreted in steel mounts - so yes I 'could' hack them out, have some more longer ones made and then try to fit them accurately and safely (bearing in mind the increased moment of force meaning I would have to do a much better job than was originally made) but 25mm IWI looks OK around them and doesn't create issues of reducing the air-flow and I have slipped in reflective 3mm foam panels and of course another place where 100% vapour sealing is more difficult. The top floor has MVHR.

Finally, I started the renovation 6 years ago when I knew very little indeed and had never done ANY DIY; pressures to live in the house in an acceptable way (I was only theoretically habitable when we moved in), my increased understanding if house green issues, my improving DIY skill and our changing financial situation have all resulted in an evolutionary renovation. There are lots of things I would do differently now.......

I was also encouraged by Peter-in-Montreal's 25mm IWI experience and it gets alot colder there!

Ohhh and wood fibre insulation and aerogel mean you are not doing it right - you have too much money!! :)

Posted By: Gotanewlife

Ohhh and wood fibre insulation and aerogel mean you are not doing it right - you have too much money!! :)http:///newforum/extensions/Vanillacons/smilies/standard/wink.gif" alt="" title="" >

Thanks for the response, it's always interesting to hear what other people are doing. As to our IWI, I wish I had too much money, or even 'enough money' :). It's a catch-22 situation we are in at the moment where we are spending a ton of money heating the house which leaves not much money to then spend on insulating the house.

We've gone for 100mm fibreboard as they're not that much more expensive than thinner versions and the main costs are the same whether we install 25mm or 100mm (i.e moving radiators, skirtings, flooring, plastering walls, painting walls, etc.) We went with the eye-wateringly expensive option of aerogel in the window reveals because we had no other options. We have steel windows set into stone mullions with very little wriggle room between the stone reveal and the start of the glass in the window. We have fitted 10mm of aerogel and then a couple of thin layers of lime plaster, and by then we've almost covered the window frame to the start of the glass.

It's so disruptive and labour intensive to do IWI, but the house is listed and we would never get permission to cover the external stonework with EWI and plaster, so we're stuck doing this.

Posted By: Peter_in_Hungary

Posted By: Pile-o-StoneWe have steel windows set into stone mullions with very little wriggle room between the stone reveal and the start of the glass in the window.

Would you get away with (removable) secondary glazing?

We don't have an issue with the sound and thermal qualities of the windows, just with thinness of the frames. We are using 10mm spacetherm blankets mechanically attached to the reveals, with lime plaster on top and they look fine, it's just an expensive business. To be fair, we chose the frames to be thin because our windows are like arrow slots and so we wanted to maximise the amount of light coming in. The old frames were wood and quite chunky, especially the ones that opened (a double frame that left us with not a huge amount of glass in the window!).