Continuous industrial process for producing biogas and a digest from liq. organic material comprises the following steps. (1) reception in an appts. with tanks for liq. and slightly depressed surfaces for solids; (2) milling, dilution and homogenisation to adjust organic matter content (for manures, sewage sludge, septic tank contents, domestic or plant wastes, core or diluted as appropriate) to 8-10% 5%; during this step the liq. is heated; (3) prim. fermentation in a vessel with fixed and sloping contact/flow surfaces (max. spacing 0.5m) to provide a rough surface; the amount of volatile solids supplied is at least 100 kg/sq.m. of surface per day and in this stage acid- and methane-producing anaerobic mesophilic bacteria develop (depending on the nature of the organic matter) for 3-7 days at mean temp. 35 (15%)C in a well mixed environment of pH 6.5-8; (4) sec. fermentation in a generally similar vessel without contact surfaces or stirring for final development of methane-producing bacteria for 2-4 days at same temp. as (3) and pH 7-8, allowing for decantation and recovery of sludges; step (1)-(4) are carried out in tightly sealed vessels and steps (3) and (4) in thermally insulated reactors; (5) sludge dehydration step, employing vacuum, heating, filtration etc., to produce a dry organic soil conditioner or full (4500 BTU/pound); (6) storage of the dried material; (7) storage of biogas from the fermentation, before purificn. for use; (8) treatment of waste water in a decanter/flocculator to permit its safe reuse and to meet regulations for discharge (i.e. total solids below 200 mg/l; suspended solids below 10 mg/l; BOD below 20 mg/l; COD below 70 mg/l; NTK below 15 mg/l; nitrates, nitrites and P only traces).    USE -    The system generates methane fuel, CO2(sec. product) and solid organic fertiliser (or fuel) from renewable resources.    ADVANTAGE -   Fermentation takes less than 10 days and all hygienic and environmental standards are met. The mesophilic anaerobes maximise methane yield.