Influence of thermochemical pretreatment conditions on solubilization and anaerobic biodegradability of a microbial biomass

The influence of thermochemical pretreatment of a microbial biomass has bee n evaluated in terms of COD solubilization and anaerobic biodegradability. Influence of pH, temperature and pretreatment time were investigated. Optim al conditions for COD solubilization were pH=12, 140 degrees C for 30 minut es. In these pretreatment conditions, up to 70% COD solubilization has been achieved. FH of pretreatment was found to be a key parameter whereas tempe rature and pretreatment time had only minor influence on COD solubilization . Biodegradability batch tests revealed that in all the pretreatment condit ions tested, the anaerobic biodegradability of the pretreated substrate was limited. Continuous experiments run with a substrate pretreated at 140 deg rees C, pH 12 for 30 minutes led to similar limitations since no acclimatat ion was observed. The hypothesis proposed was that some inhibitory molecule s have been released or that some intramolecular reactions have been induce d during the thermochemical pretreatment, leading to the formation of refra ctory compounds.