Since the non domestic Renewable Heat Incentive (RHI) was launched, the majority of funding has been allocated to biomass installations. Commercial users are seeing the benefits of using biomass as a low carbon fuel, incentivised by RHI payments for users. However, anyone applying for the RHI since September 24 2013 with a biomass boiler needs to have either a RHI emission certificate or an environmental permit. This is to meet new air quality requirements, and to make sure that biomass boilers have minimal particulate and nitrous oxide (NOx) emissions.
The criteria for the RHI emission certificate is a maximum of 30 grams per gigajoule (g/GJ) net heat input for particulate matter, and 150 g/GJ for NOx (expressed as NO2). If the biomass boiler does not have a RHI emission certificate then you can apply for an environmental permit from the Environment Agency. Biomass boilers that do not have a RHI emission certificate or an environmental permit will be ineligible for the non domestic RHI.
The new air quality requirements apply to any non domestic RHI applications made after 24 September 2013, which is the date the new regulations took effect. Applications before that date don’t need to meet the air quality requirements, however if you apply for additional boiler capacity now then that additional capacity will need to meet the new standards.
Manufacturers who are having biomass boilers tested for emissions since September 24 2013 need the testing carried out by a test laboratory which is accredited to ISO 17025. If a boiler has been tested and certificated before that date then it’s not mandatory for the test house to be accredited to that standard. Boilers are tested using the type testing range approach, which means that not every individual boiler in a range has to be tested. By testing the smallest and largest output boilers, and possibly a mid size boiler, the whole range can be certificated for a RHI emission certificate.
End users must make sure they use the correct fuel, which will be specified in the emission certificate. The manufacturer’s handbook will also detail how to operate the boiler correctly to minimise emissions. Fuel quality is paramount, and moisture content has the biggest effect on heat output as any water in the fuel has to evaporate away before the wood or biomass will burn, using up energy and reducing the amount of useful heat as opposed to steam up the chimney. Fuel with high moisture content will produce lots of smoke and tars. These tars can be corrosive, potentially damaging the lining of the flue and increasing the danger of a chimney fire.
For users burning pellets there is a Europe wide standard to ensure fuel quality – Enplus. HETAS is approved as the UK certification body for ENplus by the European Pellet Council (EPC), and is able to certificate both producers and traders under the ENplus scheme. ENplus certification sets out minimum standards for ash content, ash melting temperature, wood pellet size, dust, moisture content and heat output. Pellets with low ash content will burn more efficiently, whereas high ash levels could point to impurities in the pellets such as bark. A low ash melting temperature below 1200°C could lead to clinker, potentially damaging the appliance.
A full list of approved fuel suppliers is available on the HETAS website at www.hetas.co.uk.