Abstract: A system for and method of recovering methane gas from liquid waste which is stored within a pit is disclosed herein. The methane gas is produced by causing the liquid waste to undergo anaerobic fermentation. Therefore, it is necessary to close the pit in an air tight fashion. This is carried out using a cover sheet which is fixedly disposed over the pit in an air tight but readily disengagable fashion. The liquid waste within this air tight pit is preferably agitated intermittently during its storage therein whereby to increase the amount of methane gas produced.