A process for removing hydrogen sulfide from a raw natural gas stream such as biogas from landfills or controlled anaerobic digestion comprises passing the natural gas stream though a separation unit such as a PSA unit to form a product stream comprising a high concentration of methane and a low pressure tail gas containing hydrogen sulfide, passing the tail gas through a biofilter which includes bacteria that degrades the hydrogen sulfide to sulfur and sulfate compounds which are washed from the biofilter. The tail gas stream subsequent to treatment in the biofilter can be flared to the atmosphere without significant SOx emissions.
