The process and system may have an organic matter influent introduced into an acid reactor. The acid reactor may be maintained under conditions to facilitate creation of volatile acids in a fluid having water and suspended solids forming a sludge effluent. The sludge effluent may be communicated to an acid separation element where the water and volatile acids may be separated from the suspended solids. A liquid stream may be communicated from the acid separation element to a methane reactor and a solids recycle stream may be communicated to the acid reactor. The methane reactor may be maintained under conditions to facilitate creation of biogas. A liquid effluent may be communicated from the methane reactor to a methane separation element where liquid water may be separated from the solids. A second solids recycle may be communicated from the methane separation element to the methane reactor.