An anaerobic digester
system has a vertically upright vessel, a matrix arranged in the vessel supporting a
microorganism biomass thereon, an input for supplying an input
slurry of liquid and
suspended solids at an upper portion of the vessel above the matrix, a gas output at the top of the vessel for withdrawing gas generated by
anaerobic digestion of solids, and an
effluent output at the bottom of the vessel for withdrawing liquid and remaining solids. The vessel has a preferred
liquid height to
diameter ratio of 2 to 1, and is constructed of
inert fiberglass-reinforced plastic coated with a translucent blue gel
pigment layer for filtering light at wavelengths that promote
biomass cultivation. The matrix is formed as an array of panels mounted to a spindle with wheels fixed at spaced intervals along its vertical height, and the panel are made of a
polyethylene grass matting providing a
high surface area to volume ratio of at least 20 to 1. Gas from the top of the vessel is recycled to the bottom to generate bubbles for mixing the feedstock. The related method of
anaerobic digestion includes comminuting input wastes with a
slurry grinder into a pumpable
slurry 8-10 % by weight solids, and providing as the
biomass hydrolytic
bacteria, and fermentative
bacteria including acetogenic and methanogenic
bacteria to produce a
methane gas product. Other products include an organic soil additive, bacterial solids
plant food, and a filtrate used as
plant tonic.