A biomass boiler is one of several renewable heating alternatives to consider if you're looking to switch from a gas or oil boiler. But they aren't suitable for every property.
Whether it is possible to install a biomass boiler in your home will come down to the type and size of house you live in. And even if you can do so, there are a number of additional considerations such as refuelling and cost, as well as your individual preferences.
In this article we asked two heating experts to talk through the biomass boiler pros and cons to help you make your decision.
The pros of biomass boilers
For homes that are not connected to the mains gas grid, a biomass boiler can be an effective alternative means of providing heating and hot water. Even though they are not as efficient as an air source heat pump, they are considerably more efficient than an oil-fuelled or LPG boiler, both of which are more costly and release considerable carbon emissions into the atmosphere.
1. Biomass boilers can reach high temperatures
“Biomass boilers can operate at temperatures similar to fossil fuel systems and at high outputs” says Ben Bevan, Director of Treco Green Heat. “Of the different renewable technologies available, biomass boilers are the best for larger, harder to heat properties, as not having to upgrade the property's radiators means they are great from a retrofit perspective.”
2. Biomass fuel is cheaper than other fuels
Once you have met the initial costs of buying and installing a biomass boiler, it subsequently generates savings on your heating bill, because biomass fuel can be a lot cheaper per kilowatt hour (kWh), than that for other heating technologies.
Local suppliers of wood can deliver in bulk, sometimes bagged up for easier handling. This in turn reduces the cost of biomass fuel per ton. It is also worth considering that logs may be cheaper again than buying in quantities of wood pellets, so if you have suitable storage space for logs and a biomass boiler that can burn them, this may be an option worth considering.
3. Running costs can be little or nothing at all if you have access to fuel
The running costs for a biomass boiler are also less than those for a gas boiler. If you have access to a ready source of wood fuel, such as a woodland area or know a local farmer who is keen to dispose of wood waste, then you may be able to fuel your biomass boiler for free.
4. Biomass boilers are low maintenance
Biomass boilers are almost maintenance free, explains Pete Downes, managing director of Commercial Biomass Ltd. "Some boilers feature ash compaction into a cartridge beneath the day hopper, and bulk stores of up to ten tonnes for pellets, meaning the ash container can need emptying as little as twice a year, and the fuel only needs topping up that often too.
"They are simple, easy to understand mechanisms," he adds. "Unlike something such as a gas boiler or a heat pump, most of the moving parts of a biomass boiler are powered by motors, gears and bearings. There is a control system, which is generally a touch screen, but on the whole the mechanics are quite simple.”
Pete Downes
Pete Downes served an apprenticeship with a then FTSE100 HVAC and mechanical services company. Pete has been involved in the design and fitting of the ETA biomass heating systems in many contracts, and enjoys working with clients to achieve the installation to suit their needs.
Biomass boilers can be connected up to an existing heating system(Image credit: Getty Images)
5. You don't have to upgrade your heating system
Biomass boilers produce a high temperature heat, which means you can connect it to the existing radiators on your old heating system.
“They can take the place of an oil boiler in many instances," explains Pete Downes. "As pellet boilers are similar in size and they produce high temperature heat, you don’t have to upgrade any radiators on old systems,"
6. Quiet to run and it can last decades
Pete Downes says biomass boilers can be quiet to run compared to alternative oil and gas boilers. “The domestic boilers make very little noise," he explains. "Even if you have a suction mechanism, in the case of a pellet boiler, you can set the time when it operates to a period when there is nobody home. If you get a good boiler and it’s well fitted it can last for decades."
7. They are greener than a fossil fuel boiler
The amount of carbon dioxide emissions released by a biomass boiler are the same as those absorbed by the tree while it was growing, therefore you are not adding extra carbon emissions to the atmosphere when using a biomass boiler. However, it is also important that new plants replace those that were used for fuel. This means that biomass is a far greener fuel than fossil fuels such as coal, oil or gas.
“Annually, a typical domestic property that a biomass boiler is suitable for will save in the region of 8 to 10 tonnes of CO2 compared to heating by oil” says Ben Bevan.
8. They can burn wood waste destined for landfill
There are four grades (A, B, C and D) of wood waste that ordinarily gets disposed of in landfills. This typically consists of offcuts, wood shavings, sawdust and wood from demolition projects. Two grades of this wood waste – A and B – can be used to fuel biomass boilers, instead of it going to landfill or an urban incineration facility.
Grade C wood waste which consists of wood containing preservatives and bonded material such as MDF, chip board and plywood, requires a special type of biomass boiler (WOODCO/Justsen WID (IED) design).
Grade D wood waste, consisting of wood contaminated with hazardous chemicals (such as creosote and copper, chrome and arsenic – CCA) can only be legally burned in municipal incinerators.
9. Government grants can help with install costs
Homeowners installing biomass boilers may be eligible for a grant of up to £5,000 under the Government’s Boiler Upgrade Scheme (BUS), which runs until 31st December 2027.
Under certain conditions, such as those property owners looking to heat multiple domestic buildings, the earlier scheme operated by the Government, the Domestic Renewable Heat Incentive (RHI) is also available.
Shop biomass boiler products
Solid Fuel, Biomass Wood and Coal Boiler
This easy-to-use solid fuel, wood and coal boiler can burn just about anything to reduce heating costs
Wood pellets for biomass boiler
These unbranded wood pellets are a great, high-energy pellet providing a high heat output
Lekto Woodfuels Fire Logs
These softwood fire logs have been designed for a steady and reliable burn of up to 2-3 hours
The cons of biomass boilers
Some of the cons of biomass boilers are fairly obvious, such as getting a little smoke when they are first lit. "This is very brief and only lasts as long as it takes for the boiler to heat up and then you just see a heat haze at the top of a flue," says Pete Downes. But other disadvantages are a little more subtle.
1. Biomass boilers require lots of space
You will need much more space for your biomass boiler than you will for a gas boiler, because a biomass boiler is larger, especially if it includes a hopper that feeds the biomass fuel into the boiler. Even if it does not come with a hopper, you will still need space to store the fuel.
“The plant is physically bigger than other heating alternatives” says Ben Bevan, “and a dedicated area is required for fuel storage, so the spatial requirements are greater.”
Pete Downes agrees, adding: "Things such as a log boiler will require a large buffer tank and the rough rule of thumb for a log boiler is 50L/kW. These aren’t needed for smaller pellet boilers.
"Chip boilers also require a lot of space for fuel storage and they also need a buffer, though the rough rule of thumb is 30L/kW, less than a log boiler."
2. Biomass boilers cost more to buy and install
The initial investment involved in installing a biomass boiler is considerably higher compared to gas or oil boilers. Biomass boilers usually cost between £4,000 and £8,000, although you may be able to get a government grant under the Boiler Upgrade Scheme (BUS) to help with this.
That said, as Pete Downes points out, it's also worth bearing in mind that there is less funding up for grabs compared to heat pumps. “Biomass boilers have a slightly lower subsidy on the BUS Scheme than heat pumps – £5,000 instead of £7,500," he says.
3. You need to store biomass fuel carefully
Biomass fuel has to be kept dry, or it won’t burn efficiently. This means that either the storage space for the fuel has to be properly thought out and considered, or you will have to find an area with shelter in which the wood fuel can be left to dry out before feeding it into the biomass boiler.
4. Feeding a biomass boiler is harder work
If the biomass boiler does not come with a hopper, there will be more work involved in continually feeding the boiler with fuel – pellets, wood chips, logs or wood waste, unlike a gas boiler that uses gas straight from the gas grid.
“Along with annual servicing requirements owners can have varying degrees of interaction depending on the level of autonomy of the system” says Ben Bevan. “This includes weekly ash removal in winter, and manual topping up of fuel if there is no bulk fuel store with automatic feed.”
Pete Downes adds: "You have to refuel it, whether it’s bags of pellets, a pellet bulk store (very similar to having an oil tank filled), chips or a log boiler. You have to empty the ash, though pellet boilers are available with ash compaction. Even log boilers only produce a small percentage.”
5. If fuel isn't local it will increase your carbon footprint
If you don’t source the biomass fuel locally, there will be an additional carbon footprint involved in transporting the fuel to your home. This will mean checking what suppliers of biomass fuel are located in your immediate area.
FAQs
How often do you have to fill a biomass boiler?
It is important to choose the correct size of biomass boiler when you are making your initial purchase, because in order to ensure the boiler burns wood fuel efficiently, you have to match its output with your property’s heat demand. This means you have to consider the nominal output of the boiler and its fuel chamber size so that it meets your heating needs. The biomass boiler should match or exceed your property’s heat loss rate in order to keep up with your heating demand.
Modern biomass boilers can help with the combustion rate to a certain extent because they are equipped with Lambda sensors in the flue. These sensors constantly monitor the flue gases and adjust the air supply to ensure maximum efficiency.
As a rough guide, log boilers will require filling with wood fuel at least twice a day during winter. If the biomass boiler has a hopper attached, this will assist with feeding the boiler, thus you will merely have to ensure that the hopper is constantly supplied with fuel.
Why do biomass boilers use electricity?
Some biomass boilers are equipped with fans, electric controls and pellet feeders, which use electricity. This means that the boiler will not operate if there is a power cut and so you may want to consider some form of backup power if you live in an area where there is a high risk of power outages. The actual cost of the electricity will be minor compared to other renewable energy technologies such as heat pumps.
Biomass boilers like any other heating system have their advantages and disadvantages, and it’s important to weigh these up before committing to a purchase.
Biomass certainly isn’t suitable for all properties, but for those with large, hard to heat properties in rural areas, it can be a great solution and worth considering if weighing up biomass boiler vs gas boiler. It might also be worth considering an air source heat pump.
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Robin is a freelance journalist based in the South West of England, UK. He specialises in environmental issues, climate change and renewable energy, with other interests in transport and green motoring. He is a regular daily correspondent for a renewable energy website, writing news articles and interview pieces on all the main clean energy technologies. He has also written widely for numerous magazines on these topics, as well as writing white papers and web content.
