UK gas distribution networks have started to inject biomethane into the natural gas grid in order to reduce net CO2 emissions. However, it is important that the biomethane contains low levels of impurities, particularly siloxanes (polymers containing silicon), sulphur and ammonia, which can be present as by-products from biomethane production. Siloxanes can be a problem as burning them in domestic appliances can produce deposits of silica which reduce performance over time.
Following European Commission M/475 Mandate to CEN for standards for biomethane for use in transport and injecting in natural gas pipelines, ‘CEN TC 408 Biomethane’ started writing EN 16723 to provide guidance on biomethane quality specifications.
NPL joined CEN TC 408 to understand and advise the suitable limits of impurities that could be present in the grid and for vehicle use, which have been written as EN 16723. A main concern with regards to performing the analytical measurements required to meet EN 16723 was the limit of total silicon which was eventually set at a challenging level of less than 1 mg m-3.