Operators of appliances with a rated thermal input of 20 megawatts or more in which biomass is combusted need a permit under the Environmental Permitting (England and Wales) Regulations 2007 which will contain emission limit values set by the relevant environmental regulator. If the biomass is waste, permits are required if the rated thermal input of the appliance exceeds 0.4 megawatts.
The use of biomass for heat and power can pose a significant air quality problem. Large scale heat or combined heat and power schemes should not normally be used in heavily built-up areas (subject to an Environmental report) unless they are of high quality (20g/GJ PM10 or less) or have efficient abatement equipment specified. There are, however, technology options coming on stream which could substantially reduce emissions, even in urban areas (ceramic filters, for example). It would be easy to infer that biomass should not be encouraged in air quality management areas, which obviously already have a significant problem with air pollution. Seeking non-combustion alternatives—ground or air source heat pumps, solar thermal, better building design should be the first option; the second is to attempt to group users together—this allows the use of a smaller number of larger plants, and larger plants are easier to control.