Selected Methods of Advanced Biogas Upgrading

The upgrading of biogas for the production of biomethane to be injected to the natural gas grid has gained significant importance in recent years. It is often considered to be superior to the production of electricity and district heat with internal combustion engines mainly because of better energy utilisation, higher flexibility and beneficial economic prospects. Biogas upgrading is commonly accepted as state-of-the-art and a considerable number of small and industrial scale plants have been commissioned to date representing the portfolio of currently available upgrading technologies. Nevertheless, academic research clearly demonstrates that still a huge potential for optimisation and development is existing in this field. The current work contributes to the field of biogas upgrading by suggesting innovative and powerful approaches along the whole process chain. The importance of trace component separation is exemplary depicted by introducing a novel desulphurization technology based on chemical-oxidative scrubbing applying an innovative short-contact-time apparatus. Thus, separation efficiency for hydrogen sulphide is maximized while the simultaneous separation of carbon dioxide is minimized to assure minimum chemicals consumption. As an example for the major biogas upgrading step of carbon dioxide removal, the process of membranebased gas permeation is suggested. This technique stands out for its excellent adaptability regarding biomethane quality and methane recovery already during the design phase, simple and robust plant operation, low specific energy demand as well as reasonable upgrading costs. Finally, a combination of biogas upgrading with the Power-to-Gas approach is presented. This process provides the possibility of storing renewable electrical excess energy in form of biomethane in the high-capacity natural gas grid, an overall increase of biomethane output of a given biogas plant by maximizing carbon utilization and a reduction of the specific carbon footprint of a biomethane site.