The calorific values of grain can vary slightly, with Barley giving 4.3-4.4 kWh per kg and Wheat giving 4.5-4.6 kWh per kg. Grain is a slightly denser fuel than miscanthus, so will require less space to store for the same amount of heat.
Grain should not be used with a residual moisture content of more than 13%. Otherwise, energy that would be used to generate heat is used to burn off water, which reduces the boiler’s performance and produces less heat for the same amount of fuel.
The fusion point of grain ash is around 700°C, compared to 1,200°C for wood ash. This gives it a tendency for the ash to bind together, or "clinker", in the firebox.
The moving, self-cleaning step grate in the Guntamatic Powercorn and Powerchip biomass boilers is purpose designed to prevent this.
It is advisable to add approximately 0.3–0.5% by weight of slaked lime to the fuel before use in boilers with ratings up to 50 kW and 0.5–0.8% for boilers with ratings over 50 kW. This increases the calcium content of the fuel, thereby raising the ash fusion point and reducing the amount of clinker that can form in the first place.
The table below shows a comparison between grain and other forms of heating fuel.
Biomass fuel information
Information about the different fuel types available for biomass boilers, the regulations, considerations to take and information on procurement.
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.
About the BSL
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.