A Review of Biogas Utilisation, Purification and Upgrading Technologies

Biogas is a valuable renewable energy and also a secondary energy carrier produced from biodegradable organic materials via anaerobic digestion. It can be used as a fuel or as starting material for the production of chemicals, hydrogen and/or synthesis gas etc. The main constituents of biogas are methane (CH4) and carbon dioxide (CO2), with various quantities of contaminants, such as ammonia (NH3), water vapour (H2O), hydrogen sulfide (H2S), methyl siloxanes, nitrogen (N-2), oxygen (O-2), halogenated volatile organic compounds (VOCs), carbon monoxide (CO) and hydrocarbons. These contaminants presence and quantities depend largely on the biogas source, which could be anaerobic digestion of many substrates and landfill decompositions. The removal of these contaminants especially H2S and CO2 will significantly improve the quality of the biogas for its further uses. In parallel, biogas upgrading market is facing challenges in term of operating costs and energy consumption. The selection of appropriate technology depends on the specific biogas requirements, site specific, local circumstances and is case sensitive. This paper reviews the present state-of-the-art of biogas cleaning and upgrading technologies, including its composition, upgrading efficiency, methane recovery and loss. In addition, biogas production, utilization and the corresponding requirements on gas quality for grid injection and vehicle usage are investigated. Based on the results of comparisons of various technologies, recommendations are made on further research on the appropriate low cost technologies, especially using solid waste as low cost materials for biogas purification and upgrading.