diagram of a biomass heating system


When looking into how a biomass boiler works, we’ll first look at what biomass is. Biomass is the name given to renewable organic material that comes from plants and animals which can then be used as energy. Biomass is converted into energy using any of the following methods:

  • Direct combustion (burning) to produce heat
  • Thermochemical conversion to produce solid, gaseous, and liquid fuels
  • Chemical conversion to produce liquid fuels
  • Biological conversion to produce liquid and gaseous fuels

The use of biomass fuels for transportation and electricity generation is increasing in many developed countries in a bid to reduce carbon dioxide emissions from fossil fuel use. 

Biomass sources for energy include:

    • Wood and wood processing wastes—firewood, wood pellets, wood chips, lumber and furniture mill sawdust and waste, and black liquor from pulp and paper mills
    • Agricultural crops and waste materials—corn, soybeans, sugar cane, switchgrass, woody plants, algae, and crop and food processing residues
    • Biogenic materials in municipal solid waste—paper, cotton and wool products, food, yard waste, and wood wastes
    • Animal manure and human sewage


How does a biomass boiler work?

With the pressing issue of climate change growing ever prevalent, many people are more concerned than ever about their energy consumption and how they can reduce their carbon footprint. Installing a biomass boiler is a great alternative to traditional methods of heating your home whilst also helping to reduce the effects of climate change.

Burning biomass releases heat which can then heat homes and generate electricity. Similar to how a gas boiler can provide space heating and hot water, biomass boilers work in the same way – except rather than using gas to create heat, biomass boilers take advantage of sustainable biomass fuel.

According to Boiler Plan UK, replacing a coal-fired system with a wood-fired boiler can reduce carbon dioxide emissions by approximately 10.1 – 10.8 tonnes a year. Alternatively, replacing a modern combi boiler can still help to reduce carbon emissions by an impressive 2.6 tonnes.


Biomass boiler fuel types

Biomass boilers tend to be split into three different categories:

Log boilers 

Log boilers require a lot of logs in order to heat a whole house, and these will need to be loaded by hand at least once a day. Logs can be sourced from woodland, but having the right permissions and safety precautions is vital.

Pellet boilers 

Pellets boilers are both simpler to use and control than their log boiler counterparts. They’re also more suited to small to medium buildings and have the added benefit of being able to work automatically in the same way that gas or oil boilers do.

Wood chip boilers

With this type of boiler, wood chips are used to heat larger buildings or groups of houses. Due to the number of wood chips required, a local supplier is necessary. Extra care should be taken when using recycled wood, as there is a high risk of contaminants such as Formica, plastics and paint.



Biomass boiler pros and cons


  • Carbon neutral
  • Biomass boilers and stoves qualify for the Renewable Heat Incentive scheme (RHI)
  • An efficient way to use up waste wood
  • Practical for remote locations
  • Fuel prices are stable when compared to fossil fuels, generating additional savings
  • Less rubbish ends up in landfills as using biomass makes use of the waste
  • Can manage both your space heating and hot water


  • Biomass boilers need more space than gas or oil boilers because the system is larger 
  • The initial investment of purchasing the boiler and installing it is higher compared to traditional gas or oil boilers
  • It is essential for biomass fuel to remain dry or it won’t burn properly, so storage conditions must be considered 
  • Requires some maintenance


How much does a biomass boiler cost?

As you can see from the averages below, depending on the size of your biomass boiler and whether you manually feed the boiler yourself, the cost differs dramatically from £4,000 to £16,000:

  • A small manually fed log boiler averages at around £4,000 – £7,000
  • A large manually fed log boiler averages at around £7,000 – £10,000
  • A small automatically fed log boiler averages at around £9,000 – £16,000
  • A large automatically fed log boiler averages at around £9,000 – £16,000

There are other factors to take into account other than just the price of the boiler. How much work is needed in order to install and integrate a biomass boiler into your existing system will have a dramatic impact on the final price.

Other things that can influence the final price include the amount of heat needed to heat the entire house – therefore, the overall size of the building you intend to heat will be a critical factor when it comes to costs.

Biomass boiler grants

In order to encourage more people to switch to renewable energy sources for heating their homes, the UK Government created a scheme called the Renewable Heat Incentive (RHI). The incentive means that cash payments are made quarterly over a seven-year period.

Wood-fuelled biomass boilers are eligible for the RHI – although it should be noted that your payments will depend on factors like your system type and tariffs. 

To comply with RHI rules, your biomass fuel must be sourced from a trusted supplier which is listed on the Biomass Suppliers List (BSL), and your system must also be on the Domestic Renewable Heat Incentive Product Eligibility List. This is something you will have to organise before buying a biomass boiler.



Overall, using biomass boilers proves to be an eco-friendly and sustainable solution that can help contribute to lower carbon emissions and protect the environment. Despite there being setbacks in terms of the pricing to buy and install a biomass boiler, the Government’s cashback scheme acts as a great incentive.  

In terms of employment and how the great push for green alternatives to gas will affect the job landscape, there is still a huge demand and future for gas engineers, with many training to be multi-skilled in both natural gas and renewable alternatives. 

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Find out more about how you can train as a domestic gas engineer or get in touch with us to see how you could shape your career - we take being job-ready seriously. 

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