Earlier this month, The Greens called for efforts in improving vehicle emissions standards to be extended to woodheaters, responsible for more than a third of hazardous fine particle emissions in Sydney. Ethical Living contributor Carol Brammage investigates why wood heaters might not be the best choice for the environment, or your health.

The close association between humans and fire goes back to the beginnings of human settlement. Can we even imagine our prehistoric cave-dwelling ancestors without fire? The idea of the hearth as the centre of the home remains compelling to this day.

So is it not unsettling that the romance of the open fire at the centre of the home is the subject of criticism on environmental grounds? As a source of heat, open fires are inefficient. It is not only the wasted heat that goes up the chimney but also harmful emissions in the smoke.

[pullquote]According to the statement released by The Greens last week, a new woodheater can emit more than 1,000 times as many PM2.5 particles per year as a new passenger car.[/pullquote]

Theoretically, if wood burns under perfect conditions, the only emissions would be carbon dioxide and water. As explained by Nordica MacCarty and colleagues in a 2007 article comparing biomass cooking stoves published by the Aprovecho Research Centre, if the fuel is completely combusted and if the firewood is harvested sustainably, then the process would be carbon neutral. However, in practice combustion is not complete and results in the release of undesirable products such as carbon monoxide, methane and particulates into the air. Further, if the wood is not harvested sustainably, then the carbon dioxide released is not offset by the carbon dioxide absorbed by trees planted to replace those harvested.

Emissions can be reduced by using more efficient wood heaters, but how harmful is woodsmoke actually? Carbon monoxide, a toxic greenhouse gas, is the main polluting gas in woodsmoke. A 2004 audit of wood heaters by the Australian Department of the Environment and Heritage, notes that woodsmoke contains a range of toxic pollutants, but that the principal pollutant is in the form of particles. Inhaled fine particulate matter can be retained in the lungs causing an inflammatory response. Airborne particulates are linked to a variety of respiratory diseases, including asthma.

According to the statement released by The Greens last week, a new woodheater can emit more than 1,000 times as many PM2.5 particles per year as a new passenger car.

PM2.5 are the most hazardous air pollutant, estimated to cause 10 to 20 times as many premature deaths as the next worst pollutant, ozone, and have been linked to risks of heart and lung disease, cot death and childhood diseases such as bronchiolitis. These health risks are highlighted in an article posted in Environmental Health News on 14 March 2011. Author Cheryl Katz reports that when woodsmoke fine particulates penetrate into the lungs, “they carry high levels of chemicals linked to cardiopulmonary diseases and cancer, and they can damage DNA and activate genes in hazardous ways comparable to cigarette smoke and car exhaust.”

“Woodheaters are the chief air pollution culprit in Sydney causing 34.3% of PM2.5 emissions,” Greens NSW Senator-elect Lee Rhiannon said.

“With the winter months upon us the government needs to introduce a new health-based standard for wood heaters as a matter of urgency. The shift away from polluting woodheaters should be a health and economic priority for the federal government.”

Of course industry, power stations and traffic exhaust are among other significant air polluters, but in urban areas in winter, woodsmoke can be a major source of airborne particulates.

The use of controlled combustion wood heaters instead of open fires for heating homes can contribute significantly to reducing particle emissions. These heaters have enclosed combustion chambers and the amount of air entering the firebox can be controlled. Heaters can be free standing or inserted into an existing fire place. Their high heat output means that they can heat more than one room and even heat the whole house by means of ducting.

In Australia, the emission limit set for any new wood heater sold, is four grams of particles for every kilogram of dry wood burned. As explained in John J. Todd’s 2003 Wood-Smoke Handbook: Woodheaters, Firewood and Operator Practice, although legislation varies from state to state, most include this standard. Unfortunately, emission standards are not uniformly monitored or enforced.

Newer controlled combustion wood heaters should comply with standards set for safety, durability, efficiency and emission levels. Disturbingly, the 2004 audit of wood heaters (mentioned above) found that over half of the popular Australian models tested failed to comply with standards. The report recommends that the current system of certification be reviewed.

Another weakness is that the efficiency of wood heaters is severely compromised when owners fail to operate their heaters properly. For a wood heater to be efficient, only well-seasoned, dry wood should be used. Fires should be started with plenty of dry kindling. Wood should be cut into appropriately sized pieces and fire boxes should not be over filled. Bright, hot fires burn more cleanly than dull fires and fires should not be left to smolder.

These last pointers are applicable to older wood heaters and to open fires too. But note that in contrast to the new wood burners, open fires emit around 17 grams of particles per kilogram of wood burned.

Todd records that in 1999, about 1.5 million households in Australia used firewood for heating. Based on these figures, a rough estimate indicates that about “40 000 tonnes of fine particulates and 240 000 tonnes of carbon monoxide are emitted into the atmosphere each year”. By improving combustion efficiency, Todd maintains that “technically it would be possible to reduce emissions to just one quarter of present levels.” In practice though, it is a different matter to convince people to take responsibility and to take the steps necessary to reduce emissions.

Not only are emissions reduced when using controlled combustion wood heaters but they also consume about two-thirds less wood than open fires. But even with this reduced consumption, it nevertheless remains essential that wood is responsibly sourced.

Without the active promotion of managed woodlots and other renewable sources of firewood, demand for firewood can continue to impact negatively on Australia’s woodlands and wildlife. The Firewood Association of Australia promotes the sustainable use of firewood. It is mandatory for its members to abide by a code of practice that specifies acceptable sources of firewood. However, on its website, the Department of Sustainability, Environment, Water, Population and Communities notes that most wood is collected on private property which makes regulation difficult. The website provides guidelines for collecting wood and information on the use of firewood and its consequences.

So what to do? Improved home insulation and wearing extra layers of clothes on cold days can cut down on heater usage, but in cooler regions heating choices still need to be made. It is true that heaters fueled by gas or electricity are cleaner burning at point of use, but when taking into account extraction processes, power generation, infrastructure and transportation, the picture becomes more complex.

Wood heaters that meet local standards, are properly operated and burn sustainably produced firewood certainly have their place in the range of responsible heating options available to Australian households.

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Carol Brammage is a freelance writer based in South Africa. She has worked as an academic librarian at a university in South Africa and as a sub-editor on a daily newspaper. She holds a Master’s degree in English literature. Her interests include reading, writing, music, gardening and nature watching. She designs and makes bags and beanies inspired by African textiles and beadwork. She aspires to plain living and when possible she and her husband take off on camping trips into the sobering solitude of the bush.

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