Biomass is organic matter of recent origin. It doesn’t include fossil fuels, which have taken millions of years to evolve. The CO2 released when energy is generated from biomass is balanced by that absorbed during the fuel’s production. This is why it is considered to be a carbon neutral process.
Biomass is often called ‘bioenergy’ or ‘biofuels’. These biofuels are produced from organic materials, either directly from plants or indirectly from industrial, commercial, domestic or agricultural products. Biofuels fall into two main categories:
For small-scale domestic applications of biomass the fuel usually takes the form of wood pellets, wood chips and wood logs.
There are two main ways of using biomass to heat a domestic property:
Stoves can be 80% efficient. They’re normally used for background heating. They also add aesthetic value in the living area of the house itself. Many wood burning stoves act as space heaters only. But the higher output versions can be fitted with an integral back boiler to provide domestic hot water and central heating through radiators, if needed.
There are many domestic log, wood-chip and wood pellet burning central heating boilers available. Log boilers must be loaded by hand and may be unsuitable for some situations. Automatic pellet and wood-chip systems can be more expensive. Many boilers will dual-fire both wood chips and pellets, although the wood chip boilers need larger hoppers to provide the same time interval between refuelling.
Boilers can be designed with an integral hot water energy storage or accumulator tank that stores water up to 90º C, enabling the supply of heat to be further decoupled from the combustion of the fuel. This is particularly helpful with log boilers where systems operate at full load and the matching of demand with load is performed by the accumulator.
You should consider the following issues if you’re thinking about a biomass boiler or stove. An accredited installer will be able to provide more detailed advice.
Capital costs depend on the type and size of system you choose. But installation and commissioning costs tend to be fairly fixed. Stand alone room heaters generally cost around £2,000 – £4,000 installed. The cost for boilers varies depending on the fuel choice; a typical 20kW (average size required for a three-bedroom semi-detached house) pellet boiler would cost around £5,000 – £14,000 installed, including the cost of the flue and commissioning. A manual log feed system of the same size would be slightly cheaper.
Running costs: Unlike other forms of renewable energy, biomass systems require you to pay for the fuel. Fuel costs generally depend on the distance from your supplier. As a general rule the running costs will be more favourable if you live in an area that doesn’t have a gas supply.
Payback: This depends on the fuel being replaced and the type of wood fuel being used. It too is more favourable in areas that don’t have a gas supply.
Producing energy from biomass has both environmental and economic advantages. It is most cost-effective and sustainable when a local fuel source is used, which results in local investment and employment. Furthermore, biomass can contribute to waste management by harnessing energy from products that are often disposed of at landfill sites.