Pretreatment methods to improve anaerobic biodegradability of organic municipal solid waste fractions

•As anaerobic digestion is well-established, process optimisation raises interest.•Substrate pretreatment is a valuable option.•Main kinds of OFMSW pretreatments were reviewed.•Advantages and drawbacks for each technology were discussed.•Likely future research areas were identified.

In the last decades, anaerobic digestion facilities for the treatment of organic solid waste have become widespread throughout Europe, since anaerobic process provides a suitable treatment for this kind of waste as well as the possibility to recover energy from the produced biogas, which is mainly composed of methane. Recently anaerobic processes of organic residues are also being studied for bio-hydrogen production.Among the factors affecting the mass transfer in each biological step of anaerobic digestion, both the composition and the quality of the substrate play a fundamental role. According to the kind of substrate, pretreatments can be used in order to optimise biological process yields.Aim of this work is to review the major classes of chemical, physical and biological pretreatments of organic solid residues, with particular reference to the ones applied to the organic fraction of municipal solid waste (OFMSW) and its prevailing constituents.Therefore, main characteristics of OFMSW are provided, experimental results are compared and technologies are reported in order to identify the state of art of organic solid waste pretreatments, at both research and industrial level, as well as to point out the likely areas of future research in this field.