Renewable Natural Gas (RNG), also known as Sustainable Natural Gas (SNG) or biomethane, is a biogas which has been upgraded to a quality similar to fossil natural gas and having a methane concentration of 90% or greater. By upgrading the quality of methane-based biogas to that of natural gas, it becomes possible to distribute the gas to customers via the existing gas grid within existing appliances. Renewable natural gas is a subset of synthetic natural gas or substitute natural gas (SNG).
Multiple ways of methanising carbon dioxide/monoxide and hydrogen exist, including biomethanation, the sabatier process and a new electrochemical process pioneered in the United States currently undergoing trials.