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Eddy Mitchell

Project Title: Emissions from Domestic Biomass Combustion and Implications for Air Quality and Climate Change


I graduated from Cardiff University in 2011 with a BEng (Hons) in Civil & Environmental Engineering. My favourite aspects of the course were those with an environmental or energy focus, which led me to go on and study for an MSc in Energy and Environment in Leeds. My MSc project looked at the ability of bioenergy technologies to reduce CO2 emissions in the UK domestic heating sector – this influenced my choice of PhD research area as described below.

I joined the DTC in Low Carbon Technologies in 2012. I did two mini projects in the first year – the first on the production of high value chemicals and bioethanol from seaweeds using microwave extraction; – the second on the storage & handling problems with biomass fuels and their propensity to self-ignite at low temperatures.

Research Interests

My main research interests are domestic heating technologies, pollutant formation and emissions from biomass burning, and the impacts those pollutants have on air quality, atmospheric chemistry and climate change. My supervisors are Amanda Lea-Langton, Jenny Jones and Alan Williams from the Energy Research Institute (SCaPE), and Piers Forster from the Institute for Climate and Atmospheric Science (SoEE).

Many homes in the UK and other developed countries are beginning to install solid biofuel heating systems. Such devices include wood burning stoves, biomass boilers and micro-CHP units, all with varying levels of complexity and efficiency. The cheapest and most simplistic – wood burning stoves – are often highly inefficient combustion systems and emit high levels of pollutants such as carbon monoxide (CO), oxides of nitrogen (NOx) and particular matter (PM). Emissions of PM are of particular concern because many of the particles released from biomass burning are in the smallest size fraction – below 2.5 micrometers and even below 1 micrometer. These very fine particles are the most dangerous as they can pass deep into the lungs, causing cardiopulmonary disorders. Evidence exists all over the world linking wood burning with deteriorated air quality – including the UK, Europe, the USA, Canada, Australia and New Zealand. However, the biggest problems occur in developing countries where emissions from cookstoves cause millions of premature deaths each year. The WHO describes this as one of the top 10 risks for worldwide burden of disease.

Emissions from biomass burning also have a profound impact on atmospheric chemistry and climate change. For example, the IPCC’s most recent report showed a major uncertainty associated with black carbon (BC) in the aerosol group. Recent studies have shown that biomass burning is one of the major source categories for black carbon and such wide scale domestic burning in Asia may actually be affecting the monsoon.

My PhD Research

My work is primarily concerned with emissions factors for various pollutants from stoves. I am aiming to improve uncertainty in emissions factors by carrying out experimental work on a multifuel stove, burning a range of fuels including conventional fuels (wood logs, coal, peat) and novel fuels (torrefied wood, energy crops). I am trying to understand which properties of the fuel lead to higher emissions and what kind of technologies can be used to improve the combustion and reduce the emissions. Am I currently working with a colleague from the Supergen Bioenergy Hub to test a novel emissions abatement device. I am also working with modellers in the School of Earth and Environment, where we are aiming to use my emissions factors to improve uncertainty in the contribution of solid biofuel combustion to climate change.

The highlight of my PhD so far has to be my placement in New Zealand. I spent the first half of the placement working with NIWA in Auckland, where I did a lot of data analysis and learned a huge amount about emissions testing and air quality issues linked to wood burners. I am still working with several contacts I made there. The second half of the placement involved linking up with a team of glaciologists from the University of Leeds School of Geography. We spent several days visiting various glaciers around South Island, taking samples and recording data. On my return to Leeds, I analysed the samples in the lab to check for any traces of black carbon linked to wood burning.