New Woodheaters Pollute

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

Real-life emissions of ultra-low emission heaters much higher than AS4013 ratings
Reducing the allowable limit on a laboratory test that does not measure real-life emissions will not result in acceptable emissions from new heaters.This was tried in in Christchurch, New Zealand, when the emissions limit was reduced to 1.0 g/kg in 2002. Christchurch also prohibited use of wood heaters over 15 years old in April 2010.       Despite the fact that the vast majority of wood stoves in Christchurch have emissions ratings below 1.0 g/kg and only 18% of households in metropolitan Christchurch use log-burning heaters [7], Christchurch exceeded the World Health Organisation PM2.5 guideline of 25 ug/m3 on 22 days in 2013.
   The table compares AS4013 lab-test and real-life emissions in Christchurch. The real-life average of 9.8 g/kg is 11.4 times worse than the lab test results.
Annual PM2.5 pollution: new woodheater = 2,670 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 0.001 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 2670 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 all existing stoves (a total of 1130 old 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 program that focussed on replacing wood heaters with non polluting heating.

Portola's wood stove change-out also failing to deliver claimed benefits according to its 2018 progress report
Portola (pop 2,104, 2010 census,  887 households) has cold winters.
PM2.5 Attainment Plan in 2017 explained that "although other sources of PM2.5 concentrations may exist in the Portola area, PM2.5 concentrations are dominated by emissions from wood burning as demonstrated by the following analyses:
1) Chemical composition data;
2) Positive Matrix Factorization (PMF) modeling;
3) Strong statistical correlations between PM2.5 mass and levoglucosan; and
4) Diurnal patterns in PM2.5 concentrations." 
The above graph clearly shows that air pollution is a problem during the wood burning season, and that most of the PM2.5 is composed of organic matter and elemental carbon.
The report describes the results of chemical fingerprinting (also called positive matrix factorization) to determine the source of the pollution.  On days when air quality standards were exceeded, 86% of the pollution was attributed to wood burning, 2.8% to refuse burning, 5% to transport, 3.7% to secondary nitrate, 1.4% to secondary sulphate and 1.1% to airborne soil. 

The Change-Out Program aimed to replace 600 old, uncertified wood stoves with cleaner burning and more energy efficient home heating devices, with an estimated 100 to 150 change-outs per year from 2016 to 2020.  Incentives, up to the full cost of purchase and installation, are offered to qualified residents of the Plumas County PM2.5 Nonattainment Area (Nonattainment Area) using uncertified wood stoves or inserts as a primary source of heat.

So far,
the Program has replaced 281 stoves (80% in Portola), comprising 197 non-catalytic, 39 catalytic,  4 catalytic/noncatalytic stoves, 30 pellet stoves and 11 propane/kerosene stoves. Figure 7 below from the 2018 progress report shows that the results have been very disappointing, suggesting that replacing old wood stoves with new ones is not a cost-effective way to reduce health-hazardous PM2.5 pollution. 

In December of 2018, CARB proposed to U.S. EPA that the grant be modified to evaluate the use of heat pumps to replace wood stoves in 5 homes and fund a full-time education and outreach coordinator responsible for educating households and promoting clean heating. They also want to register every certified stove (to provide a way for inspectors to verify that households without certified stoves are not burning wood on non-burn days), build 50 wood shed and cover the cost of sweeping 200 chimneys, inspecting stoves and educating residents.


Many brand new Australian wood heaters installed in 2018 have emissions similar to those shown below (click to enlarge).  The level of emissions shown was observed for several hours. The top 3 frames are new heaters in a new housing estate.  Emissions from all except possibly the top left chimney are from heaters known to satisfy the Australian standards that will apply until August 2019. 
The smoke shown below came from heaters with AS4013 emissions ratings of about 3.2 g/kg. 

Think of the contents of a 200 jar of coffee. While enjoying enjoying your next cup, imagine the contents being replaced
by 200 g of smoke and creosote particles.  This is the amount of pollution a typical brand-new Australian woodheater will produce every single day.
       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.

Dr Dorothy L Robinson,
Apr 6, 2010, 5:50 PM
Dr Dorothy L Robinson,
Apr 6, 2010, 5:50 PM