NOVELTY - The anaerobic digestive liquor extracted from a fermenter (1) is filtered with an accurate film. The threshold valve of ammonia concentration is set to 2000-5500 mg/l. The filtrate is returned to the fermenter, when ammonia concentration is below a threshold value. The anaerobic digestive liquor bypassed the accurate film, is returned to the fermenter, when ammonia concentration is more than threshold value.    USE - For controlling concentration of ammonia, during biogas conversion from organic waste.    ADVANTAGE - Enables to maintain concentration of ammonia to a fixed range and therefore prevents reduction in concentration of nitrogen component and stabilizes biogas generation.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for organic-waste processing apparatus which has fermenter for anaerobic treatment of organic waste (12) in the state of interrupted supply of air. The organic waste is degraded in an heated atmosphere. The temperature of the heated atmosphere is set to 35-37 degreesC or 53-56 degreesC. A filtration tank (2) is equipped with accurate film for filtering anaerobic digestive liquor from the fermenter. The pore size of the film is set to 0.1-0.5 microns. The concentration of ammonia is measured by an automatic measurement device (4). A primary return pipe (16) returns anaerobic digestive liquor bypassed the accurate film, to the fermenter, when the ammonia concentration is more than the threshold value.    A secondary return pipe (17) returns filtrate to the fermenter, when the ammonia concentration is less than the threshold value. A pair of shut-off valves (6,7) is arranged in a solution-sending pipe and is selectively operated based on the concentration of ammonia. An ammonia divergence tank (8) is connected to an ammonia degradation tank (9). The pH of the filtrate in the ammonia divergence tank is set in the range of 0-14 and the ammonia is vaporized with a filler.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of an organic-waste processing apparatus.    fermenter (1)    filtration tank (2)    automatic measurement device (4)    shut-off valves (6,7)    ammonia divergence tank (8)    ammonia degradation tank (9)    organic waste (12)    primary return pipe (16)    secondary return pipe (17)