Glen Paul: G'day, and welcome to CSIROpod. I'm Glen Paul. On a cold winter's night, having a wood fired heater burning away with its warmth and glow, the smoky scent, and the flickering flames, can make for a very soothing atmosphere. Unfortunately, it can also make for a very polluted atmosphere.
Smoke from wood heaters is a major cause of air pollution. In fact during winter wood heaters can produce two to three times as much particle pollution as cars.
Dr Mick Meyer from CSIRO's Marine and Atmospheric Research has been investigating emissions from domestic wood fired heaters in Tasmania's Huon Valley, and found they even dwarf emissions from prescribed forest burn-offs.
Mick, I’m sure that most of us are aware that there’s a certain amount of pollution associated with wood heaters, but how surprised were you with the findings?
Dr Meyer: In the case of the Huon Valley I was quite surprised. The project we started there was to look at the impact of regeneration burns, and we thought that we might see a bit of wood smoke, but didn't expect it to be anywhere as near as dominant as it’s turned out. In fact, about 70/80 per cent of the aerosol pollution that’s seen in Geeveston seems to be associated with wood heaters.
Glen Paul: OK, so with the wood heaters themselves, what sort of pollutants do you find within the smoke that's produced by them?
Dr Meyer: There's a lot of compounds in smoke of course, some of them are very low concentrations and trace species. The things that people are most concerned about are usually just the particle concentrations, the soot basically that comes out the chimney.
Glen Paul: Right. So that typical brown haze you see over a city around sunset in winter.
Dr Meyer: Yes.
Glen Paul: Which doesn’t look healthy at all. Just on that then, what are the health problems that can arise from breathing that soot in?
Dr Meyer: The Epidemiologists who look at these things tell us that acute respiratory responses particularly, things like asthma can be made worse, but it can also in extreme cases trigger cardiac problems, and other direct respiratory problems, but they’re usually in a short term nature. The long term effects are much harder to document. Your short term ones are well known, and they’re significant.
Glen Paul: Now, how long does the particle matter, or soot, from burning the wood stay in the atmosphere?
Dr Meyer: What looks as though is happening is that it's accumulating overnight and in the early morning, which is of course the periods when the air is still – a lot of the households down in that region run their heaters almost continuously through the winter, both cooking and heating, so there is emission during the day as well – but during the day the air mixes much better, and tends to disperse the smoke.
But at night the winds drop and the smoke just hangs around. What was interesting down there, is that we were monitoring at a second site which was a little bit out of Huonville, and that was quite clean for most of the period – it wasn’t affected by the Huonville emissions at all, even though it was only maybe four to five kilometres away. So the pollution is actually quite localised in these towns.
Glen Paul: OK. Now let's get onto the climate change issue – some will argue that the wood being burnt in the wood heaters is part of the carbon cycle anyway, so it won’t have much of an impact. What are your thoughts on that?
Dr Meyer: There's several aspects of this. The fuel is carbon neutral, so long as the wood that you’re burning in your heater today is being regrown over the next few years. So if you're growing as much wood as you're burning, then in greenhouse terms its carbon neutral. If you’re running down your forest stocks to feed your wood heaters, of course that’s not the case at all – you’re effectively mining the timber.
Now, that can be quite difficult sometimes to be sure that you’re in balance, or whether you're mining the forests.
Glen Paul: I see. So, why was the Huon Valley chosen as the site for the research looking into the emissions from the wood heaters there in the prescribed burn-offs?
Dr Meyer: It was a pilot study. The issue of making production from regeneration burns has being growing for a number of years down there. Forestry Tasmania has a schedule for burning log sites. They need to do this to prepare the seed bed for replanting and regeneration of the timber coops(?) after they’ve been logged. They tend to burn in the autumn.
The days that are ideal for burning are also the days that are ideal for smoke accumulating in valleys. So they really wanted to check to see how much their practices really are affecting the local regions, and also whether the rules and techniques that they’ve brought in, in the last year or so, to reduce the impacts of the smoke on residents was working.
Regeneration burning occurs in various parts of Tasmania, but the Huon Valley was a very useful test case for us to study.
Glen Paul: OK. Is there limited access say to natural gases there, no infrastructure for that, because that seems to be the popular alternative these days to wood heating?
Dr Meyer: The towns that we were working in aren’t on the gas grid, so if they’re using gas it will be bottled gas, rather than reticulated gas.
Glen Paul: Is there anything that users can do to reduce the amount of pollution coming from their wood heaters?
Dr Meyer: Oh, certainly. With any device there are good practices and bad practices. Wood heaters particle emissions are lowest when the heaters are burning efficiently – that is that you’ve got plenty of air supply to it – so the one thing that you don't really want to do with a wood heater is to shutdown the damper and stuff it full of fuel to keep it burning overnight. All that does is the fuel’s burning efficiently, you get much less heat out of them, but your particle emissions could be tenfold higher than if the heater's burning merrily.
Glen Paul: Is this research a one-off, or are you going to continue on looking at other parts of Australia that use predominately wood heaters?
Dr Meyer: We will see. At the moment the project's completed; we’re about to deliver the final report on the study. At this stage there’s no plans to continue it, but having said that, the EPA in Tasmania has set up a monitoring system, quite an extensive one, around the State, which will at least document the extent of these issues.
I'm continuing the work on the wood heater emissions in conjunction with New Zealand, where there's similar and even perhaps more severe problems in some of their towns.
Christchurch is one area that is traditionally very badly affected by wood smoke, and there’s quite stringent regulations put in place over there over what sort of wood heaters can be sold, and how they can be operated. We have a program at the moment continuing over there, looking at what heaters actually produce when they're installed in houses.
Glen Paul: And do we have these types of regulations in Australia as well?
Dr Meyer: We have similar ones, but they’re not as stringent. In New Zealand the requirements are that wood heaters should emit less than one and a half grams of particles per kilogram of fuel burnt. In Australia the standard is four grams per kilogram of fuel burnt.
I'm sure the New Zealand authorities would like to see that reduced through good design of wood heaters, and I think it’s quite possible that heater design could be improved to do that.
Glen Paul: OK, well that’s encouraging, because I’d hate to see us all disappear in a puff of smoke so to speak.
Dr Meyer: Yes.
Glen Paul: Thanks for talking to us today, Mick.
Dr Meyer: OK. Thank you.
Glen Paul: Dr Mick Meyer from CSIRO's Marine and Atmospheric Research.