Renewable natural gas (RNG), also known as biomethane, is a renewable fuel and biogas which has been upgraded to a quality similar to fossil natural gas and has a methane concentration of 90% or greater. By removing CO2 and other impurities from biogas, and increasing the concentration of methane to a level similar to fossil natural gas, it becomes possible to distribute RNG via existing gas pipeline infrastructure. RNG can be used in existing appliances, including vehicles with natural gas burning engines (natural gas vehicles).
The most common way of collecting biogas with which to produce biomethane is through the process of anaerobic digestion. Multiple ways of methanizing carbon dioxide/monoxide and hydrogen also exist, including biomethanation, the Sabatier process and a new electrochemical process pioneered in the United States currently undergoing trials.