Biomass or burning boilers use wood (or other biological matter) as a fuel which is considered carbon neutral, as the carbon dioxide produced during combustion is offset by the carbon dioxide absorbed during the plant's growth.

These boilers usually use logs, wood chip or pellets as fuel and are available in sizes ranging from 10kW upwards (small commercial is around 50kW). The fuel can either be manually fed or, added as an optional extra, supplied into the hopper via a vacuum pump system.

Biomass boilers are most suited to off mains gas grid locations or in urban areas where the fuel is readily available and the systems can operate on high temperature heating systems. Systems may also be eligible for subsidy payments under the Renewable Heat Incentive.