Biomass boilers are similar to traditional gas and oil–fuelled boilers, except they burn sustainably sourced wood and plant–based pellets.
Another difference is the cost to buy one. Domestic biomass boiler prices are considerably more expensive than conventional boilers. The average cost to install a biomass heating system in a standard four–bedroom home costs between £10,000 and £14,000 (£7,000 to £12,000 of that is for the purchase of the equipment alone). Compare this to a comparably sized gas boiler which costs about £2,500. However, using a biomass boiler allows you to claim money back from the UK Government’s Renewable Heat Incentive Scheme, which we’ll talk about later.
Using plant–based instead of fossil fuels helps to prevent climate change because the burning process only releases the carbon (in the form of carbon dioxide) that the plant absorbed while it was living. Fossil fuels on the other hand release carbon dioxide absorbed over many millions of years in a matter of a few hours. You can now see why biomass heating systems are so important.
However, there are other more material benefits that a biomass central heating system can provide.
- They don’t need any more disruption during installation as a standard fossil fuel boiler.
- They use very little electricity.
- Biomass boilers can use locally sourced waste wood pellets, thus helping your local economy.
- A biomass boiler can be augmented with other microgeneration technology such as photovoltaics.
- It’s very clean, and you won’t see or smell any smoke.
- Biomass ash takes up hardly any space and can be added to the garden or compost heap as fertiliser.
- You could be eligible for paybacks from the Renewable Heat Incentive Scheme (RHIS).
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Main Topics
How Much Does a Biomass Boiler Cost?
Biomass boilers are expensive to buy. The table shows typical retail price ranges together with installation costs for various boiler types. As a general rule, automatic feeding boilers will always be more expensive than manual ones.
Biomass boiler system price list:
| Type of boiler | Size | Cost estimate |
|---|---|---|
| Manually fed log boiler | Small | £4,000 |
| Large | £10,000 | |
| Automatically fed pellet boiler | Small | £9,000 |
| Large | £25,000 |
Small boilers are typically about 15kW, medium to large boilers generate from about 15 to 1000kW.
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Biomass Boiler Price Factor
Quoted prices depend on various factors:
- How much heat needed to warm the house. The amount of heat available depends on the heat output of the boiler.
- Size of the house. A larger house needs more heat.
- Amount of automation. Biomass boilers can be manually fed or automated. Fuel such as pellets or chips is easy to automate, needing only a vacuum feeder or an Archimedes screw to successfully keep the boiler fed. Conversely, it’s more difficult to automatically logs. Instead, they’re easier to batch feed once every one or two days.
- Ease of incorporating an existing central heating system with a new boiler. Most biomass boilers and fuel storage areas need more room than conventional boilers. It’s often easier to build a separate outbuilding to house these which can cause difficulties with central heating pipework connections.
- Type of fuel. Many boilers can only use specific fuels. This means you have to source a supplier who is on the Government list to provide consistent quality fuels.
- Fuel storage capacity. Biomass will always need more room to store fuel. And, the price of fuel becomes cheaper if you buy more per delivery. The fuel storage area feeds the boiler automatically so must be nearby and within easy reach of the boiler.
It’s not only the purchase price that can vary. The biomass boiler installation costs will also vary depending on these factors.
Wood pellets are the most popular fuel and come in bags or are delivered in bulk to separate storage shed. Bulk deliveries are always cheaper.
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Types of Biomass Fuel
There are three main types of fuel available for biomass boilers. The type of fuel you choose will determine the type of boiler and how much storage space you need for the fuel.
To preserve consistent fuel quality, buy your biomass fuel from reputable biomass fuel suppliers who belong to the Hetas or Woodsure solid fuel quality assurance scheme. These organisations ensure that biomass fuel complies with the appropriate national standards specified by boiler manufacturers. You can find contact details of registered biomass fuel suppliers by looking at the Biomass Supplier’s List (BSL) on the UK Government’s website.
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Wood-Pellet Biomass Fuel
These are the most common type and best biomass fuel available in the UK and can be delivered in bags or as a bulk fuel and blown into hoppers. Generally, wood pellet boilers use fuel made from many plant–based types of material as well as wood. The most common being
- Wood chips, bark and sawdust.
- Grass.
- Peanut shells.
- Rice & wheat straw.
- Miscanthus.
Using these materials in the correct proportions allows the pellet manufacturers to produce fuel of consistent quality and moisture content without using energy to grind the raw materials.
Pellets also need to be between 5% and 10% moisture. Otherwise, below this, the pellets won’t bind together. Whereas, above the range, moisture encourages fungal and bacterial growth with the corresponding decomposition. They don’t need the addition of glues. Instead, they use the natural resins found in sawdust.
Pellets are made with standard dimensions (about 5 to 39mm long by 5 to 6mm diameter) which means there is less chance of the wood pellet boiler jamming or clogging.
On average, wood pellets have a higher energy density than other types of biomass, producing about 5000kWh per tonne. This means that an average home will use less than 10 tonnes pellets per year, depending on the size of property and efficiency of insulation. Wood pellets cost between £150 and £250 per tonne.
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Wood-Chip Biomass Fuel
Wood chips vary in size but have an average length of 3mm. If the chips are too long they will block the auger feed in the wood chip boiler. Any seasoned wood will do, with a moisture content of the raw material not exceeding 30%.
Wood chips come from wood too small to be useful in industry. They have a lower energy density than pellets but slightly better than logs, producing about 3.5kWh per kilogram. Wood chips cost abut £60 per tonne. Although cheaper they also produce less energy per kilogram. So the average running costs per year is about £900.
Log Biomass Fuel
Suppliers manufacture biomass logs in the same way as wood pellets, but they’re larger. Alternatively, you can use ‘raw’ logs. The raw material should come from a sustainable source and be seasoned for 1 year for softwood or 2 years for hardwood logs. The fuel must be free from paint or preservatives and should have a moisture content of less than 20%. Using unseasoned wood or logs contaminated with paint etc will reduce the efficiency of burning and produce excessive ash, tar and soot.
Batch burning boilers need logs of similar sizes so recommended sizes of biomass logs are 50cm long and 12 to 15cm in diameter.
Logs have the least energy density, producing between 2 to 3kWh per kilogram. This value depends on moisture content, whether hardwood or softwood and species of tree. Logs cost a minimum of about £100 per tonne. And, you need about 10 tonnes of logs to last a year. Therefore, you need to pay out at least £1000 to heat a small home for a year with logs.
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Biomass Generators
You can also generate electricity. Energy from the combustion process heats water to produce steam. The steam diverts through a steam turbine which rotates to generate electricity. A small biomass generator typically outputs from about 100kW up to 1,500kW. Larger ones can output 100kW to 5MW.
Biomass Boiler Maintenance
Maintenance demands will be dependent on the level of sophistication of the boiler. It’s not only the boiler that needs regular maintenance, but you must also check the fuel feeder. And, the amount of work depends on the level of automation.
Generally, boilers need an annual maintenance check from the installation engineer. However woodchip feeders sometimes become jammed, so the engineer may be called out more often than that. The owner must regularly clean the equipment and remove the ash. Usually, done weekly. But, wood pellets might only need ash removal every three months. Check the manufacturer’s instructions as each biomass boiler model will have unique requirements.
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Funding Options
The Renewable Heat Incentive (RHI) offers grants for domestic biomass boilers. The scheme works by paying back the owners of renewable boilers for the heat they produce. Wood pellets and wood chip boilers qualify for the funding. But, log burners don’t.
At the time of writing, the RHI tariff is 6.74p/kWh. This means that for an annual heat demand of 20,000kWh, with yearly running costs of £1,200, you would receive RHI payments of about £1,350 per year. You receive this amount split into quarterly payments for seven years. However, to get this money, you have to invest more than £10,000 for your biomass boiler.
Compare these figures with a similarly sized oil fired boiler. Its cost will be about £5,000 including a storage tank. While the running costs will be about £1,100 per year at present oil prices. Remember that an oil boiler won’t attract RHI payments. Therefore, you can see that, at present, an oil fuelled boiler costs less to buy than biomass, but without the ‘green’ credentials.
Another requirement if you want to receive the RHI grant for your biomass boiler, is to source your boiler from a company belonging to the Microgeneration Certification Scheme (MCS). The boiler must be constructed and installed according to the MCS standards. Additionally, you must use fuel from a supplier listed on the Biomass Supplier’s List (BSL).
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How Do Biomass Boiler Heating Systems Work?
Biomass boilers operate by efficiently burning organic matter and using the heat in domestic central heating systems. The boilers burn organic materials, usually waste products from other processes, and turned into pellets, chips or logs. The fuel feeds into the combustion chamber by hand or automatically. Although pellet and chip feed automatically.
Burning fuel produces hot gases that pass over a heat exchanger, transferring the energy to water for use in the central heating system. The boiler stores any excess leftover heat in a thermal buffer tank for later use. The waste products are water vapour, carbon dioxide, and carbon monoxide which vent to the atmosphere, and, a small amount of ash used as fertiliser on the garden. Plants grow, to replace those used in the fuel, absorb the waste carbon dioxide producing a carbon–neutral cycle.
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Biomass Boiler Cost FAQs
Are biomass boilers cheaper to run?
Generally, biomass boilers are cheaper to run than conventional oil and gas–fuelled boilers. However, they usually, cost more to buy. Furthermore, there’s funding from the UK Government that will help significantly towards the purchase of one of these. So, combined with its environmental impact and carbon–neutral fuel a biomass boiler often ticks all the boxes for potential customers.
Do I need planning permission for a biomass boiler?
Usually, you don’t need planning permission when installing a biomass boiler as long as all the additions are indoors. However, you will need a flue, but if it protrudes less than 1 metre above the highest portion of the house, it’s regarded a permitted development. If you aren’t sure, contact your local authority for advice.
Do biomass boilers smell?
Biomass boilers are completely enclosed and you won’t notice any odour from them. The smell from conventional boilers generally, comes from the number of sulphur emissions from the oil or gas. For biomass fuel, there is typically less than 0.1% sulphur meaning that their waste gases have virtually no smell at all.
Why is biomass cheap?
Biomass fuel comes from specially grown fuel plants as well as waste products from other industries. We don’t have to mine the earth as we do for fossil fuels, so they aren’t as expensive as non-sustainable fuels like oil or gas.
How long will 1 tonne of wood pellets last?
Generally, the answer to this question depends on your demand for heat. However, to simplify things, you can say hat 1 tonne of wood pellets produces about 4,800kWh of heat. Assuming that the pellets burn 100% efficient and your home has 100% insulation, a small house in the UK might use 1 tonne of pellets every 3 to 4 months. In practice, however, this will probably be more if you’re heating a larger and poorly insulated house.
What are the pros and cons of using biomass?
The benefits of biomass are:
- It’s a renewable and sustainable fuel source.
- You can make fuel pellets from the waste products of many industries.
- The heat comes from burning a renewable fuel so is constant. Unlike, solar or wind energy which can be intermittent.
- Plants absorb carbon dioxide emissions ready for the next cycle.
The disadvantages are:
- You need a lot of space to store fuel.
- Energy crops need water to grow so continuous irrigation might encourage drought conditions.
- Disregarding the expensive equipment you need to buy, consistent quality fuel pellets cost money when processed and regularly transported to your home. However, although this type of energy generation might be more expensive than other types of renewables, they’re still comparable to the running costs of conventional fuels.
Install a biomass boiler
It might be useful for you to have a domestic biomass boiler installed in your house. Before you decide, get advice from a qualified heating engineer on the best type for your circumstances. Complete the form on this page and you’ll receive 3 or 4 quotes detailing biomass boiler prices from a local heating engineer.
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