March 1, 2024 Biomass Boilers, Green Heat and Energy Efficiency
Biomass Boilers and Air Quality
Modern Biomass technology is a highly sophisticated, well-regulated, low-emission heat source, which is essential to UK decarbonisation. Biomass is the largest contributor to low-carbon heat to date, and the government’s Biomass Strategy recognises its importance for hard-to-treat sectors.
However, misplaced concerns about particulate emissions are leading some authorities to hesitate about biomass and withdraw their support (such as it is).
Air Quality Explained
Air quality measurements take into account any harmful or unwanted materials, especially particulate matter, which includes airborne particles that are small enough to be absorbed by the lungs. The two most common varieties of particulates are those less than 10 microns across (PM10) and those less than 2.5 microns across (PM2.5).
PM2.5 is widely used as the measurement for air quality, and various bodies and authorities have set goals and targets for it.
- The World Health Organization recommends no more than five micrograms per cubic metre (5μg/m3)
- The UK’s target for 2040 is no more than 10μg/m3
- The EU places the acceptable limit at 20μg/m3
The reality of biomass boilers and air quality
The obvious areas where air quality is most compromised are cities. They have the highest density of people, vehicle emissions, and residential heating systems. However, despite all of that, most cities in the UK are already at or under the 10μg/m3 PM2.5 target limit that the UK has set for 2040. Even the worst city for air quality (Brighton) was only slightly over the 2040 target, at 11.5μg/m3.
Even if cities’ air quality were a more serious cause for concern, biomass boilers would not be a contributing factor. Urban environments are not the setting where biomass is the ideal choice. Biomass is the heating method of choice for poorly insulated, large buildings off the gas grid — they are not generally suitable for urban environments, and as such they’re barely present there.
Biomass boiler technology and air quality
Modern biomass boilers are not simply metal boxes that burn wood. They are precision-engineered to offer maximum mechanical and combustion efficiency. Comparing the PM2.5 emissions of various heat sources, we see that biomass boilers are superior even to gas boilers.
| Technology | PM2.5 emissions (g/GJ) |
| Pellet stoves and boilers <50 kW | 30 |
| High-efficiency stoves <50 kW | 140 |
| Conventional gas boilers <50 kW | 140 |
| Open fireplaces <50 kW | 240 |
Additionally, many modern wood chip or pellet boilers include electrostatic precipitators (ESPs) which filter out 99% particulates, meaning PM2.5 emissions for those systems are negligible.
What is the future of biomass and air quality?
The biomass heat industry would welcome any opportunity to discuss our industry-leading air quality credentials with government bodies and relevant regulators.
Biomass has a vital role to play in helping the UK reach net zero. It is not always the answer, but when it is, it’s the only answer. Current policy is holding back businesses from replacing antiquated, high-carbon systems, and biomass needs to be treated as part of the solution.
For businesses thinking about switching to green power, we have prepared a Guide to Green Business Energy. If you have questions or would like advice about great energy for your company, call 01621 892613 to speak to one of our UK-wide network of renewable energy experts, and get no-obligation guidance on your business’s ESG targets and Net Zero transition.
