NOVELTY - System has bag filling mechanism mounted for traveling in an operating travel direction, impermeable bag mounted in a collapsed position on bag filling mechanism, and at least one conduit, where the bag filling mechanism is operative to receive organic material and can insert the organic material into bag such that as the bag filling mechanism moves in operating travel direction, filled portion of the bag rests on the ground behind the bag filling mechanism and an unfilled portion of the bag remains in the collapsed position mounted on the bag filling mechanism.    USE - The system is useful for digesting organic material anaerobically and for recovering gas from organic material e.g. manure, straw and wood chips, where the recovered gas is useful for domestic and commercial purposes.    ADVANTAGE - The system anaerobically digests large volume of organic matter cost-effectively.    DETAILED DESCRIPTION - System has (a) bag filling mechanism mounted for traveling in an operating travel direction, (b) impermeable bag mounted in a collapsed position on the bag filling mechanism, and (c) at least one conduit, where the bag filling mechanism is operative to receive the organic material and can insert organic material into the bag such that as the bag filling mechanism moves in the operating travel direction, filled portion of the bag rests on the ground behind the bag filling mechanism and an unfilled portion of the bag remains in the collapsed position mounted on the bag filling mechanism. The bag filling mechanism and at least one conduit are configured such that as the bag filling mechanism moves in the operating travel direction, at least one conduit is placed into the bag such that the filled portion of the bag contains a length of conduit extending, and at least one conduit is operative to conduct fluid between an exterior location outside the bag and an interior location inside the bag and a gas recovery conduit is connected to top portion of an interior of a filled bag such that gas generated in the bag can pass into the gas recovery conduit. An INDEPENDENT CLAIM is included for method for anaerobic digestion and gas recovery from organic material, which involves providing an impermeable bag mounted in a collapsed position on a bag filling mechanism, operating the bag filling mechanism to receive the organic material and insert the organic material into the bag, moving the bag filling mechanism in an operating travel direction, filling the bag to a desired level, releasing the bag from the bag filling mechanism, and sealing the bag to substantially prevent gas from leaving or entering the bag, discharging liquid mixed with anaerobically active bacteria into an upper portion of the bag such that the liquid flows downward through the organic material in the bag, drawing liquid from bottom of the bag and circulating the liquid into the upper portion of the bag, and connecting a gas recovery conduit to a top portion of an interior of the bag and drawing gas generated in the bag through the gas recovery conduit to a gas collection site.