Analysis of Meso/Thermo AD Process Applied to Pressed Biowaste

Nowadays, anaerobic digestion is a proven technology for the biowaste management. Current research interest is orientated towards process optimization in terms of biogas yield focusing amongst other on mechanical pre-treatment applications to favour solubilisation of biowaste complex organic compounds. A recent mechanical pre-treatment technique involves pressing of segregated biowaste for the physical separation of the material to distinct and more easily handled phases namely semi-liquid and semi-solid biowaste fractions. The aim of the current study is to examine the characteristics of the semi-liquid fraction and to assess the anaerobic digestion process under mesophilic (37 °C) and thermophilic (55 °C) conditions in CSTR pilot scale reactors. The semi-liquid fraction exhibits high biodegradability potential having increased volatile to total solids ratio (0.88) while the low TS content (TS = 188 gTS/kg) facilitates the operating conditions of the process. The mesophilic and thermophilic digestion processes in steady state conditions showed high strength and resilience to the process parameters such as pH, alkalinity, VFA, ammonia and ammonium levels. Mesophilic and thermophilic anaerobic digestion gave an average biogas production of 0.79 and 0.90 m3biogas/kgTVS with 66.0 and 68.8 % methane content respectively.