Biomass is a generic term that is used to describe material that is derived from living or recently living organisms. When we talk about biomass in the context of fuels, biomass is plant matter which is converted into heat by combustion. In terms of the UK domestic market, the main raw material for biomass fuels is wood.
The importance of using biomass as a fuel rests in its classification as a Carbon Lean or Low Carbon Fuel. Wood and biomass are considered a closed carbon cycle. A growing tree absorbs CO2 from the atmosphere as part of the process of photosynthesis. When the tree matures and is used as a fuel, the CO2 is released back into the atmosphere during combustion. As long as additional trees are planted to replace the ones that have been cut down, then the equivalent CO2 released is re-absorbed by these new trees as they grow, and the process is accepted as being sustainable. In simple terms, biomass takes carbon out of the atmosphere while growing and returns it when it is burned.
The major problem with this, in terms of using wood as fuel, lies with the moisture content of undried wood which usually contains well in excess of 60% moisture and is therefore unsuitable for burning. Burning wood with such high levels of moisture causes a number of significant problems and so before any wood is burnt as fuel, it must be dried or seasoned in some way.
There are a number of wood/biomass fuels generally available, including:
- Wood logs – cut and split timber, which must be either well seasoned or kiln dried.
- Wood briquettes – a fuel produced from reconstituted sawdust or sawmill residues.
- Wood pellets – a fuel reconstituted from sawdust and compacted into small pellets.
- Wood chips – a lower grade fuel that is produced by chipping wood into small pieces.
The benefits of switching to biomass heating can be considerable for a range of significant financial and environmental reasons:
Affordable heating fuel
The Energy Saving Trust estimates that a wood-fuelled biomass boiler could save an average household as much as £800 a year when compared with a traditional electric heating system.
Financial support (RHI)
Introduced in 2011, the Domestic RHI is a Government incentive scheme that was designed to support and encourage the use of renewable heat technologies. This is important because the use of qualifying energy sources will significantly help the UK to reduce its carbon emissions and thus meet renewable energy targets. Individuals who join the RHI scheme can receive regular payments for a seven-year period. The amount of this subsidy varies from person to person and is calculated based on the amount of renewable heat it is estimated that their system has produced.
A low carbon option
Equal to the amount that was absorbed when the plant was growing.