Thermophilic semi‐dry anaerobic digestion process of the organic fraction of municipal solid waste during transient conditions

Abstract

Abstract The ability to manage a biological process is linked not only to the knowledge of performance in stationary conditions. Accordingly, here, the behaviour of an anaerobic digester during transition states is reported and discussed. The paper deals with the anaerobic digestion of the mechanically sorted organic fraction of municipal solid waste under thermophilic (55°C)semi‐dry conditions (digester feed total solids=20–25%). The complete experimentation simulates a progressive increase of process capacity through variation of the operative conditions applied. In particular, changes of organic loading rate (OLR) from 4 to 8 KgTVSf (m‐3d‐1), hydraulic retention time (HRT) from 1 to 3 days, T°C up to 10°C and digester feed total solids (TS feed) from 20 to 100 g Kg‐1 are considered. Perturbations during stationary conditions are also discussed. After a complete monitoring of the digester it is concluded that thermophilic semi‐dry anaerobic digestion is a robust process, able to cope with the mentioned variations. After transient, new stationary conditions are reached very fast, generally within a week.