Patent ID: 8900840

Claim:
A method for continuously producing hydrogen gas from organic waste, comprising: a) seeding a completely mixed bioreactor with anaerobically digested sludge containing a mixture of microorganisms, the mixture of microorganisms including hydrogen producing microorganisms; b) continuously flowing organic waste into the completely mixed bioreactor; c) using the hydrogen producing microorganisms in the anaerobically digested sludge to continuously break down the organic waste in the completely mixed bioreactor and produce hydrogen gas, carbon dioxide gas, and a liquid effluent containing a mixture of volatile fatty acids, primary alcohols, and the mixture of microorganisms; d) continuously emitting the hydrogen gas and carbon dioxide gas from the completely mixed bioreactor; and e) decoupling a solid retention time from a hydraulic retention time of the liquid effluent by flowing the liquid effluent containing the mixture of volatile fatty acids, the primary alcohols, and the mixture of microorganisms to a container located downstream of the completely mixed bioreactor, using gravity to settle and concentrate the hydrogen producing microorganisms to a bottom of the container and form a settled biomass at the bottom of the container and a liquid mixture above the settled biomass; and recirculating a portion of the settled biomass from the bottom of the container to the completely mixed bioreactor, and discharging a remaining portion of the settled biomass from the bottom of the container in an excess waste stream for controlling a concentration of the hydrogen producing microorganisms in the completely mixed bioreactor; and f) discharging the liquid mixture from the container.