Wood chips are small pieces of logs or wood waste. These are formed by passing through a chipping machine, which turns them into 30mm pieces, also known as G30.

Wood pellets are a type of biomass fuel, made from compacted sawdust or other waste from saw-milling and manufacturing. At 4.8kWh per kg, you only need one third of the space that you'd need for wood chips.

As a biomass fuel, logs will generally deliver 5.1kWh per kg, depending on moisture content and type of wood (hardwood or softwood, and species).

Grain can be an economical and convenient fuel for use in biomass boilers. 'Pourable' grain such as oats, wheat and barley have a low nitrogen content. Being a slightly denser fuel than miscanthus, it will require less space to store for the same amount of heat.

Miscanthus, (or 'elephant grass') is a perennial grass originating from Asia. It is becoming popular as an energy crop as it can easily and quickly grow on poor quality land with no need for fertilisers or very much intervention.

The Biomass Suppliers List (BSL) is a list of woodfuel that has proven it meets the eligibility requirements for the Renewable Heat Incentive (RHI) scheme.