Abstract

A modular methane digester facility includes prefabricated portable concrete panels and a flexible membrane roof sealing an interior space of the methane digester. A separator-conveyor dewatering device, integratable into the front end of the methane digester facility, separates a semi-solid liquid manure into a liquid portion and a solid portion. A method of dual-stage methane digestion includes stacking a solid stage in a methane digester and supplying a liquid stage to the top of the solid stage. The liquid stage percolates by gravity through the solid stage, the solid stage acts as a filter for the liquid stage, and the liquid stage acts as a methanogenic buffer for the solid stage. A method of pre-heating a mass of solids in a methane digester to a mesophilic temperature includes supplying oxygen to the mass of solids in the form of ambient air supplied to the methane digester by a reverse-air pump.