Low in nitrogen content and convenient to boot, pourable grains such as oats, wheats and barley are a popular choice for biomass boilers. Grains can be used in models such as the Guntamatic Powerchip and Powercorn boilers. 

Because of the different types, the calorific value of grain varies. As a guideline, barley gives around 4.3-4.4 kWh per kilogram and wheat gives 4.5-4.6 kWh per kilogram. Compared to Miscanthus, grain is a little denser so will require slightly less storage space. 

Grain types for biomass boilers

As for moisture content, grain should have no more than 13%. If grain contains too much moisture, the boiler will work harder to burn it off and therefore its performance will be reduced. 

When burning grains, ash binding together can be a bit of a problem. The self-cleaning, moving step grate in the Guntamatic Powercorn and Powerchip models is designed to stop this happening. 

It’s advised to up the calcium content of your grain by adding 0.3-0.5% (by weight) of slaked lime to boilers up to 50 kW and 0.5-0.8% for boilers rated over 50 kW. This can help to increase the fusion point of ash and reduce the chances of ash binding together. 

The table below outlines the performance of grains compared to other biofuels:

Fuel kg/m3 g CO2/kWh kWh/ Kg
Grain 780 86 3.9
Miscanthus 180 8.3 3.6
Wood Chips 250 7 3.5
Logs 350 7 4.1
Wood Pellets 650 15 4.8
Coal n/a 484 8.6
LPG n/a 323 6.6
Heating Oil n/a 350 10
Electricity n/a 530 n/a
Source: Biomass Energy Centre