A hot chance: exhaustive anaerobic digestion of “grey waste” under temperatures of pasteurization
According to German laws municipal residual refuse MRR (biowaste, paper and glass are collected in separate bins) must be nearly mineralized before it will be deposited in a landfill, since this material can still contain 20 - 50 % biogenous organic matter leading to gaseous and liquid emissions. Especially the high-organic sieve fraction of MRR below 40 - 60 mm and with a thermal energy content of 5000 kJ/ kg would be unfavourably or not admissible for thermal utilizations.
Lab-scale experiments with household-organics and manure, revealed that methanogenesis should also be possible at hyperthermophilic conditions above 55°C (e.g. 70°C; Ahring, 1994). However, Lepistö and Rintala (1996) found by their experiments with wastewater that the necessary “propionate removal was significant only at 55°C”. The following experiments will show that the hydrolysis stage should be performed above 55°C and not the methanogenic stage.