Research highlights the air-quality benefits of Wood Pellet Stoves

The use of wood as a heating fuel provides CO2 (Carbon Dioxide) reduction benefits when compared to fossil fuels due to wood being a renewable fuel. CO2 is emitted in the burning of wood fuel but it is absorbed during the re-growth of the tree; therefore as long as wood fuel is produced from sustainable forestry the contribution to greenhouse gases is very low.

But despite wood heating being recognised as part of the solution to reducing the world’s use of fossil fuels and thus reducing greenhouse gases, burning wood has been connected with production of local air pollutants such as particles and volatile organic compounds.

It’s thought that over 60,000 premature deaths occurred in Europe in 2010 due to emissions from residential heating with wood and coal – an increase of 23% since 1990.

Exposure to wood smoke can cause a range of ailments, many with the potential to contribute towards or lead to fatality including respiratory illness, and decreased lung function. 

In 2019 over two hundred thousand stoves were sold in the UK, and 67% of them were multifuel. So as the trend for using stoves to heat our homes increases, what can be done to ensure that UK air quality is improved and that wood stove emissions are as low as possible?

The University of Leeds has presented research which highlights the benefits to air quality from using wood pellet stoves compared with traditional multi-fuel stoves. The findings are significant, demonstrating a 95% reduction in particulates emitted by pellet stoves. That is 20 times less particles for a standard pellet stove versus a traditional log stove.

Figure 1. Leeds University wood stove emission levels

Reducing the particulate emissions is crucial for air quality on a local level but just as importantly research estimates that 70% of emitted wood smoke from a log stove can re-enter the home. 

So why does a wood pellet stove create less emissions than log stoves? 

  1. Pellets are a standardised product that conforms to strict requirements to be pure virgin wood free from contaminations and contain very low levels of ash
  2. Pellets are a homogeneous, small and ultra-dry wood fuel, this means combustion can be fully controlled and consistent as there is no change in moisture and size that affects how the wood burns
  3. A pellet stove controls the wood fuel rate and air supply rate at a ratio that ensures full and complete combustion so no smoke and unburned gases leave the stove
  4. A pellet stove is a continuously fed device not a batch fed one like a log stove, this means the conditions and temperatures are constant

What are we doing to improve air quality ?

We have recognised for a long time that there has been a contradiction between burning wood being viewed as ‘renewable’ and also whether it is ‘environmentally’ beneficial.

At Island Pellet Stoves we went further with our Lundy design – we were conscious that high efficiency, low CO2 and low emissions was essential in the current position of climate emergency and the concerns about the quality of air in our cities. 

The concentric / balanced flue was a step forward as the pre-heating of air resulted in improved combustion in the secondary and tertiary burning of the gases. 

Our flue gases pass through tubes and particle separation systems like that of larger high-efficiency boilers, this has significantly increased the completion of the combustion process and meant that efficiency increased while particles, carbon monoxide and volatile compounds were significantly reduced.

We have compared the results of the Leeds University study to our particulate and NOx emissions and we have found that our patented combustion system produces emissions lower than those of typical pellet stove and thus achieving up to 98% reduction; a 50 times reduction over a traditional log stove. 

Inside Air Quality

As our homes become more sealed to conserve heat, our internal air quality has been affected with some cases reported of the air quality being worse inside the home than outside. We have also been monitoring inside air quality when our Lundy stove is operating and have proven that our fully sealed design has not caused emissions emitted into the home. 

The results of our tests on internal air quality measured while the Lundy stove is heating a home are shown below; no noticeable difference from background levels of particulate and VOC’s were detected.