Successful and stable operation of anaerobic thermophilic co-digestion of sun-dried sugar beet pulp and cow manure under short hydraulic retention time

. The gradual OLR increase allowed system control and time-appropriate intervention, avoiding irreversible process disturbances and maintaining admissible acidity/alkalinity ratios (<0.8) for HRTs ranging from 30 to 4 days. The accumulation of acetic acid was the main cause of the process disturbance observed at short HRTs. It was deduced that for the HRT of 3 days, the methane productivity was mainly owing to the hydrogen-utilizing methanogens pathway. This research clearly shows how an adequate combination of agro-industrial wastes and livestock manure could be processed by anaerobic co-digestion in short HRTs with great efficiency and stability and deepens in the understanding of the start-up, stability and optimization of the co-digestion.