Acclimation of an anaerobic consortium capable of effective biomethanization of mechanically-sorted organic fraction of municipal solid waste through a semi-continuous enrichment procedure

BACKGROUND: Municipal solid waste is generally disposed of by incineration or landfilling. Higher combustion efficiencies or lower waste amounts to be dumped, respectively, can be obtained through recovery of the waste wet fraction, which could be valorized by means of anaerobic digestion processes with the production of a CH4-rich biogas. However, such a fraction is typically poorly digestible. The aim of this work was to obtain a methanogenic consortium capable of effective biomethanization of the wet fraction collected from a municipal solid waste. RESULTS: An up-flow recirculated column bioreactor (0.36 L) was initially filled with cattle manure and then, after a short batch working period, fed with the above mentioned target substrate according to a semicontinuous scheme. More than 90% of the overall COD fed during the whole 5-months experiment was depleted. The methane production yield gradually increased throughout the process to 0.35 L g-1 of depleted COD. Molecular analysis of the microbial consortium indicated that the archaeal population, which consisted of two acetoclastic Methanosarcina sp. strains, persisted during the whole experiment, whereas several hydrolytic and acidogenic Firmicutes and Bacteroidetes were enriched throughout the process, concomitantly to the increase of the biomethanization potential of the consortium. CONCLUSIONS: An anaerobic consortium capable of efficiently converting the wet fraction of municipal solid waste into methane was obtained through a dedicated enrichment procedure in an up-flow anaerobic recirculated reactor. This result was mainly ascribed to the acclimation and enrichment of bacterial species. Copyright (c) 2012 Society of Chemical Industry