Fermentation utilizes different microorganisms to convert organic waste into alcohols (usually
ethanol) and sludge. Like anaerobic digestion, fermentation relies on pretreatment to optimize
alcohol outputs. Enzymatic hydrolysis is the most common type of pretreatment (Pham et al., 2015).
Fermentation can be used in conjunction with gasification to produce a higher electrical output. In
MSW applications, fermenters are usually used to complement thermal treatment processes. Only a
few stand-alone MSW fermentation facilities exist.
Since the organic fraction of MSW is complex and made up of widely differing substrates, pre-
decaying ligands (binding molecules) of different durability are present and yield different qualities of
alcohol products. Consequently, fermentation of MSW is not as widely used as anaerobic digestion
and is still limited mostly to demonstration-level systems and laboratory experiments.