A compact vertical array of concentrically stacked and interfaced anaerobic digestion modules which comprise an anaerobic digestion sub-system. Each individual digestion module is an open-ended reaction vessel having an external flange on each end. Each pair of adjacent reaction vessels has a suitably...http://www.google.ca/patents/US4248972?utm_source=gb-gplus-sharePatent US4248972 - Stacked modules for anaerobic digestion
