Real-life emissions much higher than AS4013 ratings
A CSIRO study (published 2008) measured real-life emissions from AS4013 woodheaters, where education programs, including a $2 million federally-funded woodsmoke reduction program, had alerted the public to the serious health problems caused by breathing woodsmoke.
Knowing the health effects of woodsmoke and that their emissions were being measured, the volunteers would have been motivated to take the time and trouble to operate their heaters correctly. The researchers commented that was no evidence heaters were “allowed to smoulder overnight; in contrast they appeared to be refuelled periodically throughout”.
Despite the extraordinary dedication of the volunteers, particle emissions averaged 9.4 g/kg wood burned (range 2.6 to 21.7).
Low-burn emissions 7 to 8 times higher than AS4013 rating
A study of over 100 households found that that people rarely operate their woodheaters as prescribed in the Standards test. They use larger logs and only a third of households always correctly loaded them perpendicular to the heater’s door. More importantly “when intending to operate the woodheater at slow or medium burn rates, the air control is rarely left fully open for the 10 to 15 minutes required in the standard test method.”
Emissions were measured in laboratory tests, in which 4 new heaters were operated under a revised test method, turning the air control to low after two minutes instead of waiting until 20% of the fuel load had been burned. One heater, rated 2.5 g/kg, emitted 17.5 g/kg, producing a total of 183 g of particulates on a single overnight burn - see Todd & Greenwood, 2006. Another rated 2.9 g/kg emitted 22.7 g/kg, i.e. a total of 175 g over the next 8 hours
This implies that real-life emissions can be 7 to 8 times higher than the AS4013 rating.
Annual PM2.5 pollution: new woodheater = 267 petrol cars
Australian woodheater expert Prof John Todd noted that the current generation of woodheaters emit about 10 g/kg (see below - time to develop new woodheater standards). A typical petrol-fuelled passenger car emits about 0.01 g PM2.5 per km, or about 150 g if driving 15,000 km per year. A heater burning Armidale's average of 4 tonnes per year will therefore emit 40 kg of PM2.5, equivalent to the annual PM2.5 emissions of 267 passenger cars.
Health costs - thousands of dollars per heater per year
A study pubished in 2005 estimated that every kg of PM10 emitted in Sydney has health costs of $132 - see Table 6.3.1 of Geoff Morgan's study on the NSW Department of Environment and Climate Change website. A subsequent study, commissioned by the Federal Government, recommended that PM2.5 should be used to estimate health costs in preference to PM10. In Sydney. Health costs in Sydeny, expressed in terms of PM2.5, exceed $200 per kg of emissions. With the average average fuel consumption of 2 tonnes per year, a new heater in Sydney will emit 20 kg of PM2.5 with estimated health costs of about $4,000 per year.
Several local councils in Sydney have introduced development control plans that do not permit new heaters to be installed. These include Waverley and Holroyd, with others requiring non-polluting heating in new developments, e.g. Manooka Valley, Oran Park and Turner Road Growth Precincts.
Time to develop new woodheater standards
Australian woodheater expert Prof John Todd wrote in an article published in 2008 in Clean Air: "We must develop a new generation of woodheaters that burn cleanly when used in people’s homes. How cleanly? Well, the present heaters emit somewhere around 10g of fine particles per kg (dry-weight) of firewood. The next generation must be 1 g kg or less in order to achieve acceptable air quality in areas with a high proportion of wood- users, and ideally we should aim for a further order of magnitude improvement to 0.lg/kg
Until these new models are available, consumers should be wary of buying a new heater that will emit unacceptable levels of air pollution. With estimated health costs of more $2,000 per year (Armidale) and $4,000 to $6,000 per year in Sydney (right column), we need a moratorium on the installation of new woodheaters until a health-based standard has been developed.
Complete 'Change-out' left Libby, Montana, with many days of totally unacceptable pollution
Huge sums (over $2.5 million) were spent in Libby, Montana, a town of 2,600, replacing 1130 stoves just to achieve a 28% reduction in pollution (see graph below from Prof Michael Brauer's webinar). Canadian research shows significant health damage to healthy volunteers exposed to only 10 ug/m3 of PM2.5 from woodsmoke for just 1 week. In order to avoid the risk of serious health problems and premature death, the new stoves should be replaced by energy efficient non-polluting heating powered by the sun and the wind, together with any upgrades in insulation and energy efficiency that will help reduce running costs.
The enormous sums spent on replacing existing woodstoves with new ones that produce almost as much pollution seems like a waste of money compared with the 70% reduction from Launceston $2.05 million woodsmoke-reduction rprogram that focussed on replacing wood heaters with non polluting heating.
Think of the contents of a 200 jar of coffee. While enjoying enjoying your next cup, imagine the contents being replaced
People talk about the pollution from power stations in the Hunter Valley. Yet, all modern power stations have filtration systems to trap the particles. Measured pollution as ground level has been described as "negligible".
What kind of filtration system could trap 200 g of particles from the average domestic chimney every day without blocking? Unlike power stations, wood heaters do not have particle filtration systems. Not only are many more particles emitted per unit of heat, they are emitted at roof height where where they are much more likely to be breathed in and damage our health.
US: comparison of gas, oil & wood heating
US standards specify the maximum emissions in terms of grams per hour. Consequently, the problem of excessive emissions of new heaters low burn might not be quite as bad as in Australia. The illustration below is nonetheless a fairly good representation of the situation - that new heaters are probably better than older ones, but 97 lbs of PM2.5 pollution is still far from acceptable, given that there is no safe level of PM2.5 pollution, that the average passenger car (driving 15,000 km/year) produces about 1/3 lb of PM2.5, with oil heating (1/4 lb) and gas heating (1/6 lb) even less.