What is a biomass boiler? - Grand Designs magazine

What is a biomass boiler?

Find out exactly what this means of renewable heating can offer your home.

By Hugh Metcalf |

If you’re looking into renewable energy sources for your home, you may have heard of biomass heating. What is a biomass boiler? In essence, it burns biological matter to supply a heating system. Read on for more details.

Living room of a low-energy home showing a ceramic tile clad biomass boiler

Biomass heating warms this low-energy home by Baufritz

Renewable fuel

Wood-fuel heating is often referred to as biomass. It is a renewable energy source because burning wood emits the same amount of CO2 that the tree took up while it was growing. A biomass boiler burns logs or pellets. Pellets are compressed sawdust and fine wood shavings. They are more convenient to use than logs, and their heat output is higher. Look for ENplus accreditation as an indication of quality, and source from a trader on the Biomass Supplier List. In doing so, you may qualify for Renewable Heat Incentive (RHI) payments.

Is it the right choice for me?

A biomass boiler provides hot water and heating highly efficiently. The downside is that you’ll need plenty of space to accommodate one and to store fuel. Pellets need to be close by and dry. So, housing a boiler in a utility room, garage or outhouse is the best option. Some models also require a thermal store to maximise efficiency. A specialist heating engineer can tell you if a biomass boiler is an appropriate, cost-effective heating solution for your needs.
Biomass boilers have an efficiency of around 80-90 per cent, which is higher than conventional fossil-fuel boilers. They need an annual service and a flue that meets regulations for wood-burning appliances. HETAS recommend the flue or chimney should be swept twice a year to remove soot deposits and blockages.

If you’re looking into renewable energy sources for your home, you may have heard of biomass heating. What is a biomass boiler? In essence, it burns biological matter to supply a heating system. Read on for more details.

Living room of a low-energy home showing a ceramic tile clad biomass boiler

Biomass heating warms this low-energy home by Baufritz

Renewable fuel

Wood-fuel heating is often referred to as biomass. It is a renewable energy source because burning wood emits the same amount of CO2 that the tree took up while it was growing. A biomass boiler burns logs or pellets. Pellets are compressed sawdust and fine wood shavings. They are more convenient to use than logs, and their heat output is higher. Look for ENplus accreditation as an indication of quality, and source from a trader on the Biomass Supplier List. In doing so, you may qualify for Renewable Heat Incentive (RHI) payments.

Is it the right choice for me?

A biomass boiler provides hot water and heating highly efficiently. The downside is that you’ll need plenty of space to accommodate one and to store fuel. Pellets need to be close by and dry. So, housing a boiler in a utility room, garage or outhouse is the best option. Some models also require a thermal store to maximise efficiency. A specialist heating engineer can tell you if a biomass boiler is an appropriate, cost-effective heating solution for your needs.
Biomass boilers have an efficiency of around 80-90 per cent, which is higher than conventional fossil-fuel boilers. They need an annual service and a flue that meets regulations for wood-burning appliances. HETAS recommend the flue or chimney should be swept twice a year to remove soot deposits and blockages.

Image: The Vitoligno 300-C compact pellet boiler includes a silo, pellet feed and buffer vessel for an output of 4-18kW, Viessmann.

Manual or automatic?

Choose from basic machines with manual fuel loading, to more sophisticated models with automatic fuel delivery via a hopper. They can be programmed like conventional boilers and some will automatically clean themselves. The ash needs to be taken out on a regular basis – either automatically or by hand, depending on the model.

Stove models

Pellet stove boilers have a back boiler to provide hot water for central heating or for washing as well. They’re unlikely to satisfy 100 per cent of your needs but can work in tandem with other renewables, such as solar thermal panels. They have automatic ignition and some models have an integral hopper that can hold two days’ worth of fuel. Pellet stoves are space heaters but, unlike their log-burning counterparts, are controllable and can turn on automatically. They’re more than 90 per cent efficient and produce far less ash than log burners.

What’s the cost?

Biomass boiler systems cost more to buy than gas or oil types. But affordable ongoing fuel prices and RHI payments make installation more attractive. According to the Energy Saving Trust, an automatically fed biomass pellet boiler costs between £8,000-£15,000, including installation. Pellet costs depend on quantity and the method of delivery. Bulk buying and storing is by far the most economical option.

Biomass boilers and stove boilers qualify for the RHI scheme, the current rate is 6.97p/KWh, but rates change, so keep an eye on the Ofgem tariff tracker. To qualify, systems must be fitted by an installer accredited under the Microgeneration Certification System (MCS) and use MCS-certified products.

 

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