In recent years there is an increasing attention for climate change issues. This is an important driver to identify emissions of greenhouse gases from wastewater treatment plants (WWTPs). Greenhouse gases emitted from a WWTP are CO2, CH4 and N2O. The emission of CO2 is mainly related to the consumption of electricity that is used for treatment processes such as aeration, pumping and dewatering. CO2 emission from the biological process itself is part of the so called short-cycle CO2 and does not count for the greenhouse effect. The emission of methane as greenhouse gas is scarcely researched, but is thought to be produced and emitted from sewerage systems and only on a minor scale produced at the treatment site itself. Sludge handling facilities (thickeners, dewatering of digested sludge) could however also be significant sources of methane.

The emission of nitrous oxide (N2O) is related to the removal of ammonium via nitrification and denitrification. This occurs in surface waters when all ammonium is discharged via the effluent or is included in the processes at the WWTP. The fraction of nitrogen that is emitted as N2O is variable among the different researches performed in the laboratory and on full-scale plants.

A lot of research is currently performed on the emission of non CO2 greenhouse gases from WWTP and sewers. To discuss the methodology and results of this research this website is launched as a platform for discussion.