Draft PPS18: Renewable Energy
Annex 1 Technology: Airborne Emissions
B30. All processes that involve combustion, gasification or pyrolysis give rise to emissions to the air. It is therefore important to consider stack emissions produced by a biomass power plant in the existing environmental context. At the local level, this means comparing them with other sources of emissions and with current air quality. In the broader context, it means comparing the stack emissions from a biomass electricity generating plant with those from a power station fuelled by coal, oil or gas. Carrying out a greenhouse gas emission Life Cycle Analysis (LCA) calculation should be used in this situation.
B31. Emissions from biomass fuel combustion include limited quantities of gaseous nitrogen and sulphur oxides and carbon dioxide. Emissions of nitrogen and sulphur oxides are significantly less than those from comparable fossil fuel stations. Flue gas is discharged from the plant via a chimney. Under certain conditions (particularly in cold weather) a steam plume may emanate from the chimney. This is non-polluting, the only consideration being the visual effect.
B32. Biomass fuel combustion may also give rise to particulate emissions from the chimney, known as ‘fly ash’. These can be kept within UK and European particulate emission limits using techniques such as cylone separation, or electrostatic precipitation in the flue.