RNG (renewable natural gas) is a mostly methane stream that is most commonly derived from biogas produced by anaerobic digestion or from landfill gas (LFG) by removing impurities such as CO2, H2S, and water vapor to achieve a purity similar to pipeline fossil natural gas.  Other means of production include conventional catalytic methanation of waste CO2 with renewable hydrogen (made by water electrolysis with renewable electricity), and advanced electrochemical processes. RNG can be added to the natural gas pipeline, burned locally for heat and power, or fed to chemical synthesis.