Biogas, a methane (CH4) rich gas produced from anaerobic digestion of organics, is an undervalued renewable fuel. Upgrading biogas by removing impurities and concentrating CH4 produces a cleaner, more useful fuel. While biogas can be upgraded to biomethane, also called reneweable natural gas (RNG) (>95% CH4, see footnote), a fuel that can be compressed and injected into natural gas pipelines or used in CNG vehicles, upgrading to this level is currently cost prohibitive for most farms. More typical on-farm use of biogas is as a fuel source for boilers and engine-generator sets, where lower CH4 levels (>50%) can be used; optimally with most of the moisture and hydrogen sulfide (H2S) removed. Combinations of demisters, condensation sumps, and chillers can be used for dewatering. Many technologies can remove H2S (desulfurize) biogas, and are highlighted below.