Abstract: A process is provided for recovering methane from landfill feed gas and other anaerobic digestors. The process comprising the following steps: firstly treating the feed gas to remove H2S; subsequently compressing the gas; and then treating the gas to remove further impurities. Additionally, there is provided a chiller for reducing the temperature of a gas flow. The chiller comprising: a shell arranged to be chilled, a plurality of bores through the shell and through which the gas flows, in use, and forming, together with the shell, a heat exchanger, a tangential inlet to each bore for creating a spiral flow of the gas through the bore, in use. Furthermore, a process is provided for purifying a gas feed using a reversible gas absorber unit comprising two hollow fiber gas/liquid contactors, each of which is arranged to provide a counter-current flow.