Do you have a biomass boiler? Are you receiving payments from the Renewable Heat Incentive?
If so, you are probably using wood chip or wood pellets as the fuel. However, the potential of using cheaper, alternative non-wood fuels such as straw, miscanthus, waste coffee grain pellets, sunflower husk pellets to name just a few is growing. Many of these fuels are being registered on the Sustainable Fuel Register (SFR), which may make them eligible for RHI payments as long as they meet the emissions criteria for your boiler.