Methane gas produced by anaerobic digestion of wastewater sludge can be upgraded to pipeline quality and sold to a public utility for injection into a natural gas distribution system. Upgrading the gas typically involves treatment for removal of carbon dioxide and hydrogen sulfide, dehydration, and compression. Upgrading of digester gas to pipeline quality is technically feasible. Moreover, based on current prices of natural gas, selling of upgraded gas to a public utility is economically viable. Although this method of gas utilization has been investigated for several wastewater treatment plants, no such programs have been implemented. The primary reason is that to date, other alternatives (usually involving on-site uses) have been considered more manageable or economical. Gas generated in solid waste landfills is similar in quality to digester gas. Several landfill gas recovery, processing, and utilization projects (some of which involve selling upgraded gas to a public utility) have either been implemented or are being planned. Because there are no competing on-site uses of landfill gas and because landfill gas quantities are typically much larger than those from digesters, landfill gas has a greater potential for future development by public utilities.