Velen denken dat het verkeer de grootste vervuiler is………

Woodheater-Car Comparison


Many people think that cars are the worst pollutants.  Sydney has lots of cars but few woodheaters, so we’d expect all the passenger cars in Sydney to produce more total pollution than the small number of woodheaters.  PM2.5 are now considered the most health-hazardous air pollutant, responsible for about 10 to 20 times as many premature deaths as the next worst pollutant, ozone.

New diesel cars must satisfy strict Euro 5/6 pollution standards, which require a new car, 4WD or SUV travelling 20,000 km to year to emit less than 0.1 kg of PM2.5.  In contrast, the NSW EPA estimates that a new wood heater will emit 9.8 kg of health-hazardous PM.25 per year.  Thus a brand new AS4013 heater emits as many PM2.5 in 10 hours as a new car does in an entire year and a heater burning 2 tonnes of firewood will emit 19.6 kg of PM2.5, as much as 196 diesels and 1000 petrol cars!


A total of 5457 tonnes of PM2.5 per year in Sydney are emitted by Sydney’s woodheaters, compared to a total of 135 tonnes from the exhausts of all petrol vehicles, 813 from diesel vehicle exhausts and 597 tons from road, brake and tyre wear.  This means that the average woodheater more PM2.5 pollution than several hundred passenger cars.
Sydney has lots of cars. Armidale has lots of woodheaters.  The graph below compares monthly average PM2.5 nephelometer measurements, recorded by the NSW EPA in Armidale in 1996 and Sydney in 1999.  When woodheaters are not in use, Armidale has cleaner air.  But as soon as the woodheating season starts, Armidale’s pollution rises dramatically, with only a small rise in Sydney where only 4.3% of households use wood as the main form of heating.  This again shows that the average woodheater emits a lot more health-hazardous PM2.5 pollution than the average car and that the only way for Armidale to have wintertime air that is as clean and healthy as in Sydney is for residents to use non-polluting heating.

Prof John Todd’s article in “Clean Air and Environmental Quality” notes that there has been “only marginal improvement over the past 15 years” in woodheater emissions.  Emissions from new cars have also improved.  A new car driving 15,000 km per year emits about 150 g of PM2.5.  With average fuel consumption of 2 tonnes per year (Sydney) or 4 tonnes (Armidale), a new woodheater will emit 133 times (Sydney) or 267 times (Armidale) as much health-hazardous PM2.5 pollution as the average new car driving 15,000 km per year.


Woodheaters also emit more greenhouse gases than other forms of heating.  Many councils offer subsidies to replace woodheaters with non-polluting heating.  Woodheater owners who are concerned about their health or the environment should remember the advice of the NSW DECC “If you can see or smell smoke from your wood heater then you are causing a problem for yourself, your family and your neighbors and consider taking up this offer.

Proportion of PM2.5 emissions (the most health-hazardous air pollutant) emitted by residential wood heaters (purple line joining the triangles) in Sydney by month.  This graph from NSW EPA website, is from their emissions inventory which shows that more than half of all man-made PM2.5 emissions are from the small proportion of households using wood heaters.  ABS statistics show that only 5% of Sydney households use wood as the main form of heating.


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