A system and method for the purification of biogas, the system comprising: a gas compressor for increasing the pressure of the biogas for processing; a gas processor for removing any CO2, volatile organic compounds, and H2S, from the gas; an optional biological sulfur removal system for treating offgas from the gas processor; a regenerative thermal oxidizer system for treating gas from the biological sulfur removal system for thermal destruction of volatile organic compounds, H2S, and CH4 slipped from the gas processor; a catalytic oxygen removal system for receiving product gas from the gas processor and removing oxygen from the product gas; and a caustic scrubber for receiving product gas from the catalytic oxygen removal system and neutralizing any acid formed during catalytic oxygen removal.