The invention concerns a facility for the processing of organic waste by a combination of fermentation and composting, the installation being characterized in that it includes a biogas plant (1) for the fermentation of organic waste of simple composition, the biogas plant being connected by a pipe line (2) to a tank (3) containing the fermentation substrate and the tank (3) being connected by a pipe line (4) to a clamp-type composting plant for waste of complex composition (5) and/or to an enclosed composting plant for any contaminated organic waste of complex composition and for waste from a composting reactor (6). The invention also concerns a method of processing waste in such a facility, and a biogas plant (1) for use in the facility.