Stove manufacturers working to tackle emissions

SPECIAL REPORT: Dennis Milligan of the Stove Industry Alliance outlines efforts to reduce emissions from the domestic burning of wood and coal.  

Lord Gardiner of Kimble under-secretary of state at Defra has confirmed that the government is working alongside stove manufacturers, fuel suppliers and retailers to reduce emissions from the domestic burning of wood and coal (see airqualitynews.com story).

But what are they doing?

With the support of Defra, the Stove Industry Alliance (SIA) has introduced Ecodesign Ready Stoves, five years ahead of the Ecodesign Regulations becoming law. Ecodesign is the European wide legalisation aimed at reducing emissions, (PM2.5 & PM10), and improving appliance efficiency. It is due to be implemented for solid fuel room heaters in 2022. From January 2022 it will be illegal to sell a stove that has not passed the Ecodesign emission and efficiency tests. Unlike Defra’s exemption for wood burning stoves, which only applies to smoke control areas, Ecodesign will cover the whole country.

From 2020 the main manufacturers in the SIA have also committed to only manufacture new stove models that will satisfy Ecodesign requirements. Independent testing by Kiwa, the main UK test laboratory for solid fuel appliances, has shown that Ecodesign Ready stoves can reduce particulate emissions by 90% compared to an open fire and 80% compared to a stove manufactured ten years ago.

The DECC Domestic Wood Usage survey (2015) revealed that 70% of the wood burnt in London was burnt on open fires (nationally the figure is nearly 60%).  Defra’s own figures show that domestic coal and wood burning contributes between 7% to 9% of London’s fine particulate concentrations (PM2.5 & PM10). From these figures, it can be seen that the installation of Ecodesign Ready stoves could lead to a significant reduction in PM emissions. The SIA is pushing for an upgrade scheme that could accelerate the replacement of older appliances with Ecodesign Ready stoves. Ecodesign Ready stoves were launched in January and there are already over 200 models available. Stove test results are verified by HETAS, the largest competent person scheme for installers of biomass and solid fuel heating in the UK which also approves appliances and fuels. This means that the consumer can be confident that the stove will meet the Ecodesign emission limits.

Wood moisture

Modern clean burning stoves are designed to burn dry wood. Dry wood creates fewer emissions and produces more heat than wet wood. Wet wood can also lead to a blackening of the stove glass and a build-up of soot in the chimney. Defra is again supporting the industry to create a new category of wood called Ready to Burn.

Wood needs to be dried before it is burnt. Freshly cut wood can have a moisture content between 60% and 80%. This makes burning fresh wood equivalent to burning water. To dry logs properly they need to be left to dry for between one and three years (the length of time depends upon the species. Ash for example may take 12 months while oak may take 36 months.) This is known as seasoning.

Most people buying a stove do not have the space to dry wood for up to three years. They want to buy wood that is ready to burn. As a result, stove owners are encouraged to burn kiln dried wood, which has a moisture content of less than 20%, and dried/seasoned wood, that has been allowed to dry, but too often ‘seasoned logs’ have been sold with too high a moisture level; often between 30% and 50%. The Woodsure Ready to Burn logs will have a verified moisture content below 25%. This means the consumer will be able to buy a bag of logs branded Ready to Burn in the knowledge that the wood will give optimum performance in the stove.

Ready to Burn

Using dry wood also means that fewer logs are needed to produce the same level of heat. This, in itself, reduces emissions because less wood is being burnt. It also saves the stove owner money. The diagram below illustrates the impact of wet wood on the heat produced by a log.

Taken together Ecodesign Ready stoves and Woodsure Ready to Burn wood can produce more heat for the stove owner and produce fewer emissions in the environment. Most people already know that a wood burning stove will produce significantly lower carbon than oil or gas. They can now use a wood burning stove, knowing they are reducing particulate emissions and CO_2.

Defra is making the right choices with a responsible industry that is taking the initiative to improve air quality.