Among the other solutions planned to regulate these problems, we can quote anaerobic digestion or the methanisation of organic wastes in general and wastewater treatment plant sludge in particular. The anaerobic digestion is an organic matter transformation process in energy by bacteria in oxygen absence. It permits to produce a combustible gas called biogas, which is essentially methane composed, and can reduce half of organic matter (Poh et Chong) [4]. The final digestion residue (or digestat) is stable, deodorized, ridded in major part of the pathogenic germs and can even be used as a fertilizer for agricultural purposes. The wastewater treatment plant sludge valorization by anaerobic digestion process permits to produce a renewable energy, that was available, little expensive and no polluting. The biogas production is considered as an economic solution, decentralized and environmentally friendly for the sustainable development.