Anaerobic digestion of industrial waste waters presents several advantages with respect to conventional processes (low energy consumption, not much waste sludge, methane production). The ANOXAL process, developed and sold by AIR LIQUIDE, is composed of a fixed-cells reactor with upward feeding and re-circulation. An inert packing improves the retention of biomass by fixation and trapping. This process has been applied successfully to two types of wastes as different as one from food processing - FLODOR (Peronne) - and one from paper industry - CELLULOSE DU PIN (Tartas). This technology should offer to industrials a high flexibility and should not need new skills in the plants.