New evidence suggests that domestic wood burning emissions as published in the Clean Air Strategy are significantly overstated.
Based on a new academic report commissioned by HETAS and the Stove Industry Alliance (SIA), the proportion of emissions resulting from domestic woodburning as quoted by Defra in their Clean Air Strategy has been significantly overstated.
Within the Clean Air Strategy published earlier this year, Defra suggested that the increase in burning solid fuels (wood and coal) in our homes (domestic burning) is having an impact on our air quality and now makes up the largest single contributor to our national particulate emissions, stating a staggering 38%.
This new report casts considerable doubt on these published figures by highlighting uncertainties’ in respect to both the calculation methods and measurement techniques employed, and an over estimation of wood fuel consumption in the UK.
One of the main concerns raised within the report is that of wood consumption used for domestic burning. The 38% figure stated in the Clean Air Strategy assumes that 6m tonnes of wood fuel are burnt each year in the UK. This information was derived from a user survey of 1,206 members of the public carried out in 2015 by BEIS.
In early 2019, the SIA conducted its own user survey of 10,620 members of the public using wood stoves at home. The results of the survey indicated that the volume of wood burnt each year is closer to 1.85m tonnes. Applying this data to the calculation method used within the Clean Air Strategy, the percentage of PM2.5 attributable to domestic wood burning would fall from 38% to 14.9%, a significant difference.
The SIA users survey also showed that more than 27% related to either open fires or less efficient stoves that were over 10 years old. It was further demonstrated that by replacing less efficient technologies with the new Ecodesign ready stoves, this would further reduce emissions by 45%. Such action would have a further positive impact, reducing the UK PM2.5 emission down to 8% in the case of wood burning.
It was also found that other sources of PM2.5 were being categorised within the context of wood burning. These mainly coming from unregulated sources such as barbeques, chimineas, firepits, pizza ovens, smokers and bonfires. All these unregulated sources contribute to air pollution. Other factors such as burning of garden waste also has very high concentrations of particulates and is not being distinguished from stoves. As cited by Harrison in the report, there are “many facets to [UK Air Quality] data which cast doubt on whether the instrument is reliably reflecting concentrations of woodsmoke”.
With all the focus currently on wood burning and particulates, it is interesting to understand the greenhouse gas emission factors within the context of other heating fuels, as detailed in the following chart:
(Greenhouse gas emission factors for different heating fuels. Source SAP 10.02)
Let’s remember that wood is a renewable biomass resource that is supported by the Renewable Heat Incentive (RHI) and has significantly lower lifecycle GHG emissions than natural gas, heating oil, coal and smokeless fuel as demonstrated above.
One fascinating fact taken from the report is that 80-90 thousand tonnes of charcoal are imported and burned on unregulated UK barbecues each year. There are many key points contained within this report, but by using the high efficiency Ecodesign ready stoves, there is no reason why well-seasoned wood cannot be burnt in both an environmentally friendly and sustainable way.
The use of wood burning stoves within our houses is a very old tradition, providing both a source of heat and ambiance within our homes. The SIA report provides valuable analysis and highlights several areas for additional research and a message to the industry as to how through new technology and education we can all benefit long term burning wood in a sustainable and environmental way.
To find out more information regarding the Stove Industry Alliance (SIA) and Ecodesign ready stoves, please visit their web site