Biogas purification processes

A review on the processes that have been used or are promising for the removal of CO/sub 2/, H/sub 2/S, and water vapor from biogas. The process conditions and flow schemes for 16 processes are given. The basic physical mechanisms that are involved in the processes are discussed and include physical absorption into a liquid (dissolution), chemical absorption into a liquid, physical absorption onto a solid, chemical conversion to another compound, membrane separation, and condensation.