Biomass boilers burn organic matter to generate heat.

Requires: Local supplier of sustainable fuel, Insulation.

Biomass heating systems burn organic matter for fuel such as wood pellets, chips or logs, or manure. Biomass boilers can be connected to central heating and hot water systems. The main advantages of biomass systems are that:

  • Biomass is classed as a low carbon fuel. Although biomass emits carbon dioxide (CO2) when burned, it is CO2 that vegetation has taken in from the atmosphere during their lives. The net CO2 from using biomass fuel is from the cultivation of the plants and processing and transportation of the biomass. This is less emissions than from using fossil fuels.
  • Although the price of biomass fuel can vary considerably, biomass is often cheaper to run than other fuel sources, apart from new high-efficiency gas or oil systems.
  • Biomass fuel sources are renewable, provided enough plants are grown to replace those burned.

However, biomass systems require more labour-intensive maintenance than fossil fuel boilers, including:

  • Regular cleaning and sweeping to prevent ash build up.
  • Collection of ash from the combustion grate and heat exchanger tubes. Some boilers have self-cleaning systems for this. For those that do not, periodic shut down will be required for this to be done manually.
  • Annual maintenance checks.
  • For wood-burning boilers, sweeping soot and any other blockages from the flue pipes, at least biannually at the start and end of winter.

Biomass boilers are larger than their fossil fuel equivalents so adequate space is necessary. They also require space for the flue, and for fuel deliveries and storage. Biomass boilers also emit particulates and nitrogen oxides (NOx), which means they are unsuitable for use in densely populated areas. Future legislation may restrict the burning of biomass in certain areas.

Logs can be cheaper fuel to buy than pellets, but this will depend on wood suppliers in the local area to reduce transportation costs. If space is available, it is well worth considering buying unseasoned logs and storing them for a year to let them season (air-dry) before burning. This will reduce the purchase cost significantly. Seasoning logs is important because burning unseasoned (wet) wood increases the amount of soot deposits and the chances of chimney fires.

Energy Saving Trust, Generating Renewable Energy, Biomass. Available from: [Accessed 26th January 2021].