This Digest has been written to provide an overview of the technical and operational characteristics of biomass systems within the scope of the Microgeneration Certification Scheme (MCS). Standards and specifications are covered, including certification, safety and incentives (such as the Renewable Heat Incentive and Green Deal). Although some technical information is given, it is not intended as an installation guide. The intended readership includes landlords, housing associations, local authorities, developers, architects and consultants.This is one in a series of four related Digests focusing on a renewable energy technology commonly used in domestic buildings. The other technologies covered include photovoltaics, heat pumps and solar thermal collectors.