Press release 2019-03-27

Large variations in wood combustion emissions

Short-lived climate-impacting air pollutants trigger both climate and health issues. Small-scale residential wood burning is major source of these emissions. A study carried out by IVL Swedish Environmental Research Institute on behalf of the Nordic Council of Ministers shows that combustion with a reduced wood load and an inadequate air supply results in higher emissions than normal combustion, this is also happens when unseasoned wood is burned.

– The way in which wood is burned is crucial to the amount of emissions generated. To avoid unnecessary emissions of air pollutants wood must be burned in the proper way, says Karin Kindbom, report author and project manager, IVL Swedish Environmental Research Institute.

Together with researchers and experts in the other Nordic countries, IVL has measured and analysed the emissions of particles and short-lived climate-impacting air pollutants from the most common types of stoves and wood-burning boilers installed in residential buildings across the Nordic countries. As expected, emissions were higher in older boilers and stoves than in more modern equipment. For example, under normal conditions, emissions from traditional wood boilers were between five and ten times higher than those from modern wood or pellet boilers.

The study shows that reducing output – burning too little wood and throttling back the air supply to achieve longer burning times – results in poorer combustion and higher emissions. Compared to optimum combustion conditions, emissions were as much as six times higher at reduced output, and up to eight times higher when unseasoned wood was used.

In addition to the fact that emissions sizes vary greatly depending on the combustion process, the Nordic countries also use different so-called emission factors to estimate emissions of air pollutants. This has made it difficult to establish how large actual emissions are, as well as to compare emissions between the Nordic countries. Based on emission metrics, the researchers have now developed new emission factors that can be utilized in national inventories.

– This study shows that you cannot simply ignore the high frequency of "bad" combustion when measuring emissions to air at a national level, says Karin Kindbom.

Short-lived climate-impacting air pollutants affect not only health issues and air quality but also the climate. So-called black carbon, a result of incomplete combustion, absorbs sunlight both directly in the atmosphere and when spread out across snow and ice-covered regions where it induces higher temperatures and faster snow melt. Methane and tropospheric ozone are also included among short-lived climate-impacting air pollutants.

See also:
Emissions of Short-Lived Climate Pollutants (SLCP)
Policy Brief - Emissions of Short-Lived Climate Pollutants (SLCP): Emission factors, scenarios and reduction potentials

For more information, please contact:
Karin Kindbom, karin.kindbom@ivl.se, +46 (0)10-788 67 72