Anaerobic Digestion of Municipal Solid Waste: Thermophilic vs. Mesophilic Performance At High Solids

Abstract
High solids anaerobic digestion of the mechanically sorted organic fraction of municipal solid waste under mesophilic and thermophilic conditions is reported. The semi-dry thermophilic process has a gas production rate two to three times the mesophilic process and nearly complete biodegradation. A 3 m3 stirred digester, feeding organic waste at 16-23% solids, was operated at hydraulic (volumetric) retention times decreasing from 15-8 days, and at organic loading rates increasing from 6 to 14 kg volatile solids m-3 day-1. An economic evaluation favours the thermophilic over the mesophilic process.