In past centuries, home heating and cooking in the British Isles involved the burning of wood, mainly in open hearths. The Romans developed underfloor heating using hot air (the ‘hypocaust’) but this still relied on wood combustion. The first wood-burning stove was patented in Strasbourg in 1557, but by the industrial revolution urban houses were typically heated with coal. By the mid Twentieth century oil, gas and electricity had become the fuel of choice largely due to the introduction of the Clean Air act, which curtailed the use of household ‘dirty’ coal, but open fires and stoves remained popular where they could be accommodated, especially in rural areas.
In recent years, ‘aspirational lifestyle’ marketing by stove manufacturers (and TV shows like Grand Designs), along with the availability of new biomass-based fuels (pellets and briquettes), have been driving a resurgence – with some even suggesting that because wood is technically a renewable energy source, woodfuel is a clean and green way to heat your home. But is it? And what are the other implications?
A study published by two of the UBoC team, working with colleagues at the University of Leeds (lead author EJS Mitchell) and the National Institute of Water and Atmospheric Research (NIWA) in Auckland, sheds light on at least one burning issue; air quality and climate impacts from the burning of Residential Solid Fuels (RSF) such as biomass and coal, in heating stoves and fireplaces.
(UBoC also aims to research residential wood-fuel supply chains, to assess the impact of different productive woodland management techniques on carbon sequestration, biodiversity, pollution mitigation, flood alleviation and more. And a UBoC-supported PhD investigation into the sustainability verification of power-station-scale biomass supply chains is starting in February).
The air quality and climate impact study, which is published in the journal of Atmospheric Environment, compared the high use of RSF in New Zealand, which is responsible for severe wintertime air quality issues and climate impacts to the UK where the use of RSF is typically low. The results show that RSF contributed significantly to black carbon (BC) in some suburban locations of New Zealand in 2006, with significant air quality and climate impacts. BC is a major component of soot which contributes a warming effect to climate that offsets some of the benefit of reduced overall CO2 emissions.
Models predict RSF consumption in New Zealand to decrease slightly from 7 PJ to 6 PJ between 1990 and 2030, whereas consumption in the UK will have increased by a factor of 14 over the same period. The study found that by 2030, the residential sector will account for 44% of total BC emissions in the UK, which will far exceed emissions from the traffic sector. The contribution to RSF emissions from the residential sector to total UK radiative forcing was also found to increase by 23% over the same period.
Finally, a unique bottom-up emission inventory for RSF emissions was produced for both countries using the latest national survey/census and emission factor data for the year 2013/14. Comparing to pre-existing emission inventories, the authors discovered that RSF emissions in the new emission inventory were generally a factor of 1–2 higher for coal and several times higher for wood, suggesting that emissions from residential heating stoves and fireplaces may be underestimated in current climate models.
The insights from New Zealand show that the increasing combustion of RSF in the UK may likely result in poor wintertime air quality unless action is taken to control RSF emissions such as, for example, by use of Ecodesign emissions limits. (Ecodesign of Energy Using Products Directive is a recent European Union initiative which aims to improve the energy efficiency of appliances by establishing minimum performance requirements for specific product groups, thus removing inefficient products from the marketplace).