WOOD BURNING AND CLIMATE
Trees are green, but burning them is not
Wood burning is often described as a 'renewable' or carbon neutral energy source. It is argued that if a tree is burned for fuel, another can be planted to replace it, which will eventually re-absorb the carbon. But as with all climate science the issues involved are not so simple. As an article in the New Statemans says 'The regrowth of trees takes time, and younger trees that are regularly harvested in plantations may never store as much carbon as older, bigger trees in natural forests.' Research published by Chatham House found that while in the longer term carbon dioxide released from burning wood could be absorbed by replacement trees, there is no certainty this is the case in the coming years or even decades. While some may wish to claim wood burning as a renewable, they cannot claim that wood burning is a clean energy. Unlike solar, wind and hydrogen (which are also renewables), wood burning produces the most significant source of air pollution in many parts of the world. As the table to the right (or below) shows (from the Victorian EPA's Emissions Inventory Report - page 73) - wood heating in Victoria alone contributes 4029.89 tonnes of health harming PM2.5 into the atmosphere annually, more than fossil fuels and vehicles.
Wood burning also emits black carbon, brown carbon, methane and carbon monoxide. All of which speed up global warming. While carbon dioxide (Co2) emissions are the main target of actions to reduce climate change, and make up to 60% of long term radiative forcing (or warming) in the atmosphere, Short-lived Climate Pollutions (SLCP) (which as their name suggests, produce a short-lived warming effect in the atmosphere from a few days to a decade) make up the other 40-45% of global warming gases. SLCPs include black carbon, methane, tropospheric ozone, and hydrofluorocarbons (HFCs) and are commonly associated with refrigeration, diesel-fuelled vehicles, and burning of solid-fuel (such as wood stoves and wood heating). Black carbon is estimated to be the second largest leading cause of global warming after Co2. And as described by the Climate and Clean Air Coalition in their Primer on SLCPs, the major sources of black carbon are open burning of biomass, diesel engines, and the residential burning of solid fuels such as coal, wood, dung, and agricultural residues. A study published in the Proceedings of the National Academy of Sciences (PNAS) reports that non-CO2 green house gases are responsible for nearly half of all climate forcing global greenhouse gases and that targeting SLCPs is essential to limiting the year 2100 warming below 2 degrees. 'While these climate forcers remain in the atmosphere for a much shorter period of time than carbon dioxide (CO2), their potential to warm the atmosphere can be many times greater'.
The debate about renewables along with the complexity of the science makes wood heating an easy target for green washing - that form of marketing spin used to convince us that a product is environmentally friendly. Because wood is a natural product, many people assume burning wood must be harmless. A warming fire is not only romanticised but it is also deeply embedded in our culture as central to our species survival. The wood heating industry doesn't have to work very hard at all to convince people that wood heating is good for the environment. But these green claims do not reflect the science. A 2013 study published in Annals of Forest Science looking at using wood as a substitute for fossil fuels concluded that to mitigate climate change it is better to store wood than use it as a fuel. And a 2019 Finnish study in Energy Policy concluded that using a wood stove was the most climate unfriendly way to heat a home.
Clean forms of home heating
Recent research has shown that heat pumps, also known as reverse cycle or heater-air-conditioners are the cheapest and most environmentally friendly way to heat a home. This is because they move the warmth the sun adds to our air from outside to inside the home. Efficient models can deliver five times as much heat to the home as they use in electric power, so can be counted as 80% renewable even when running off coal-fired power, and of course 100% renewable for anyone using green power.
They are also cheap to run - only a fraction of buying firewood and many models cost less to buy and install than a wood stove. And of course, they are thermostatically controlled and can be set to start to warm the house before the occupants are out of bed. There are also get floor mounted models, some of which radiate heat.
For low income households the Victorian government is offering a $1000 rebate to upgrade home heating. For more information go to https://www.heatingupgrades.vic.gov.au/about-us
For information about sustainable heating you can visit the website for the national, not-for-profit organisation Renew https://renew.org.au/resources/how-we-can-help Or the Australian Energy Foundation -https://www.aef.com.au/ - both of whom provide expert advice and information on sustainable solutions to households.
Research reports and articles on wood burning and climate change
Below are links to some of the other studies and reports about environmental impacts of wood burning.