Poor air quality is the biggest environmental factor contributing to premature mortality globally. In the recent update to the global burden of disease, long-term exposures to fine particulate matter was estimated to contribute to 4.9 million premature deaths annually, with respiratory and cardiovascular diseases, cancer, diabetes and links to dementia being the main contributors.
Domestic solid fuel burning (in particular wood) is now the dominant source of fine particulate matter (PM2.5) in the UK (38% of the total in 2019). PM2.5 is one of the biggest areas of concern for air quality and human health in the UK and caused an estimated 33,100 excess deaths in 2019. Efforts have been made to reduce particulate pollution but in recent decades, solid fuel burning for space heating has only increased in popularity, with an estimated 50,000 extra homes installing new stoves each year. Wood users represent 7.5% of the UK population, although with large regional differences (2015 BEIS Domestic Wood Survey).
Fires can emit a wide range of pollutants into the gas and particle phases, including many organic compounds from the degradation of cellulose and lignin. Gas phase emissions of volatile organic compounds can react with atmospheric oxidants to form secondary organic aerosols (SOA). Many of the organic species emitted are known to be toxic, but little is known about the impact of atmospheric ageing on the toxicity of wood burning emissions.
Stove designs have improved over the years, in terms of heat efficiency and emissions. Currently, all new stoves installed in the UK must conform to the ‘Ecodesign 2022’ standard. In the UK, wood burning emissions are measured under strict operational conditions, including correct fuelling according to manufacturer’s instructions. However, it is known that emissions are not continuous with time, with peak emissions occurring during the ignition phase and when reloading fresh fuel. The emissions from wood stoves are further complicated by the variabilities introduced by fuel type and the operator. Poor quality fuels such as unseasoned or waste wood are known to emit more pollution than drier fuels such as kiln-dried wood and the government has taken steps to ban the sale of ‘wet’ woods. However, new fuels are now available made from timber or other by-products, such as from coffee grounds, although their emissions are uncertain.
The over-arching aims of this PhD studentship are to understanding the formation and toxicity of SOA from domestic wood burning in the UK. The student will work within the NERC funded “CondensabLe AeRosol from non-Ideal Stove Emissions” (CLARISE) project. The project aims to understand how emissions from burning change when stoves are used incorrectly or when unconventional fuels are used. The student will carry out short deployments at the University of Manchester Stove Facility to collect samples and use state of the art analytical tools to determine the composition of the SOA formed. They will then use novel machine learning approaches to understand the impact of different burn and oxidation conditions on the toxicity of wood burning emissions. The outcomes of this project will allow us to understand the broader impact of wood burning in the UK and provide evidence to develop better mitigation policies.