Renewable and highly efficient, get to grips with what biomass heating is, how it's installed and what it costs.
Image: In this pre-fab, low-energy Baufritz house, a highly efficient biomass system using wood pellets from sustainable sources provides heating and hot water.
If you're looking into renewable energy sources for your home, you may have heard of biomass heating as an option for your build. But what exactly is it?
In essence, a biomass boiler replaces traditional fossil fuels by burning biological matter instead and channeling that outputted energy into your home's heating.
What types of fuel are used?
Wood-fuelled heating is often referred to as biomass. It’s considered a renewable energy source because when wood is burned, it emits the same amount of CO2 that the tree absorbed while it was growing. Logs or pellets can be used. Pellets are made from 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 registered on the Biomass Supplier List, so you can qualify for Renewable Heat Incentive (RHI) payments.
Is it the right choice for me?
Biomass boilers provide hot water and heating highly efficiently. The downside is you’ll need plenty of space to accommodate one and to store fuel. Pellets need to be stored close by and kept 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. Correctly installed and maintained, they have an efficiency of around 80-90 per cent, which is significantly 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 fully automated Vitoligno 300-C compact pellet boiler costs from £24,000 including silo, pellet feed, buffer vessel for an output of 4-18kW, Viessmann.
How to choose a boiler
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 removed on a regular basis – either automatically or by hand, depending on model.
Pellet stove boilers have a back boiler specified to provide hot water for central heating or to provide hot water as well. They’re unlikely to satisfy 100 per cent of your needs but can be linked 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. Only stoves with a back boiler qualify for RHI. Pellet stoves are space heaters but, unlike their log-burning counterparts, are controllable and can be programmed to turn on automatically. They’re over 90 per cent efficient and produce far less ash than log burners.
How much does it cost?
Biomass boiler systems cost more to buy than gas or oil types, but affordable ongoing fuel prices and RHI payments make installation 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 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.