What Is a Biomass Boiler and How Does One Work? 

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

Pros:

• Carbon neutral
• Eligible biomass boilers may qualify for a Boiler Upgrade Scheme (BUS) grant (rural, off-gas-grid properties)
• 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

Cons:

• 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 previously ran the Renewable Heat Incentive (RHI). The Domestic RHI closed to new applicants on 31 March 2022 and is no longer available. It has been replaced by the Boiler Upgrade Scheme (BUS), administered by Ofgem in England and Wales.

Rather than the RHI’s quarterly payments over seven years, BUS provides a single upfront grant — currently £5,000 towards the cost and installation of a biomass boiler. Biomass eligibility under BUS is more limited: your property must be in a rural location and not connected to the mains gas grid, the boiler must have an emissions certificate showing low polluting emissions, and the installation must replace a fossil-fuel heating system and be carried out by an MCS-certified installer (new self-build homes are not eligible).

The biomass fuel you use must still come from a supplier on the Biomass Suppliers List (BSL). Grant values and eligibility can change, so always check the current rules on GOV.UK before purchasing. (Scotland operates a separate scheme via Home Energy Scotland.)

Conclusion

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 Boiler Upgrade Scheme grant offers a helpful upfront contribution towards the cost.

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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