NOVELTY - Anaerobic biomass processing system comprises: an anaerobic acidification reactor (1) containing acidification bacteria in a suitable environment for acidifying the biomass, and comprising an inlet (11) for biomass and an outlet (12) for acidified biomass; an anaerobic settling chamber (2) comprising an inlet (21), a first outlet for cleared liquid biomass, a second outlet for sludge biomass, and a third outlet for gaseous biogas effluent; and an anaerobic methane synthesis reactor containing methanogenic bacteria for anaerobic microbial conversion of cleared liquid biomass.    USE - The system is useful for processing biomass using anaerobic digestion into biogas and processed liquid biomass, and in an animal farm (all claimed), which is useful for processing its own waste products, and converting them into useful products.    ADVANTAGE - The system: is simple; utilizes vegetable material that provides increased production of processed biomass; utilizes the filter device that is robust and easy to clean; and alleviates the labor for an operating person.    DETAILED DESCRIPTION - Anaerobic biomass processing system comprises: an anaerobic acidification reactor (1) containing acidification bacteria in a suitable environment for acidifying the biomass, and comprising an inlet (11) for biomass and an outlet (12) for acidified biomass; an anaerobic settling chamber (2) comprising an inlet (21) arranged to receive the acidified biomass from the outlet of the anaerobic acidification reactor and containing methanogenic bacteria in a suitable environment for methanogenesis in biomass in the settling chamber in which the biomass is allowed to settle and thus forms a cleared liquid biomass, a sludge biomass and a gaseous biogas effluent, a first outlet for the cleared liquid biomass, a second outlet for the sludge biomass, and a third outlet for the gaseous biogas effluent, where the settling chamber is free from mixing means; and an anaerobic methane synthesis reactor containing methanogenic bacteria in a suitable environment for anaerobic microbial conversion of cleared liquid biomass into biogas and processed liquid biomass, and comprising an inlet arranged to receive the cleared liquid biomass from the first outlet of the anaerobic settling chamber, a first outlet for biogas and a second outlet for the processed liquid biomass, and mixing means, in particular movable mechanical mixing means, for mixing the biomass in the methane synthesis reactor. An INDEPENDENT CLAIM is also included for an animal farm, comprising at least one housing arranged to keep livestock or poultry, and the system.    DESCRIPTION OF DRAWING(S) - The figure shows the anaerobic biomass processing system.    Anaerobic acidification reactor (1)    Anaerobic settling chamber (2)    Inlet anaerobic acidification reactor (11)    Outlet of anaerobic acidification reactor (12)    Inlet of anaerobic settling chamber (21)