A review of biogas purification processes

Biogas is a valuable renewable energy carrier. It can be exploited directly as a fuel or as a raw material for the production of synthesis gas and/or hydrogen. Methane (CH4) and carbon dioxide (CO2) are the main constituents, but biogases also contain significant quantities of undesirable compounds (contaminants), such as hydrogen sulfide (H2S), ammonia (NH3) and siloxanes. The existence and quantities of these contaminants depend on the biogas source (i.e., landfills, anaerobic fermentation of manure). Their presence constitutes a major problem because (i) they can be detrimental to any biogas thermal or thermocatalytic conversion device (e. g., corrosion, erosion, fouling); and (ii) they generate harmful environmental emissions. It is therefore important to include biogas purification steps upstream of its final use processes. This review is aimed at presenting the scientific and technical state-of-the-art in biogas purification processes. Both mature, already-applied and promising, under-development technologies are reported and described here. (C) 2008 Society of Chemical Industry and John Wiley & Sons, Ltd