The invention pertains to a process for producing methane by a two-stage anaerobic digestion of organic feed, comprising i) subjecting an organic feed suspension (a) to acidogenesis and methanogenesis in a first reactor (1); ii) withdrawing an effluent (b) from said first reactor and subjecting it to solid/liquid separation (2), thus obtaining effluents high (d) and low (c) in solids, wherein the volatile fatty acid (VFA) concentration in said first reactor is controlled by the withdrawal rate; iii) subjecting the effluent low in solids (c) to acidogenesis and methanogenesis in a second reactor (3), thus producing methane gas in said first and second reactor.