The objective of this project is to improve the efficiency of anaerobic digesters organic waste and side streams through digestate recirculation to the digester. By ultrasound technology or oxidation (ozone and H2O0) to be applied to the digestate, the remaining organic fraction of the digestate will thereafter be returned to the digester, this disintegrated flow is a type of "secondary feed", a result of which, in general, a higher conversion of the organic material is achieved in the input stream. Inhibition by ammoniacal nitrogen is also addressed by a more or less selective removal of ammonia in the digestate recirculation.