Sugarcane vinasse processing: Toward a status shift from waste to valuable resource. A review

The foreseeable increase of bioethanol production by distilleries will inevitably lead to an important increase in production of the associated effluent, namely vinasse. Due to its high pollution load, characterized by high chemical oxygen demand, high salt content and heavy dark color, the depollution of this effluent is mandatory before release into nature. In this work, we reviewed the literature on the main physicochemical and biological treatments of sugarcane vinasse and emphasised on the technological valuation of vinasse that allows to shift the status of the effluent from waste to valuable resource. The membrane systems seem to offer the best depollution option but they are subjected to strong technical limitations. Several alternative processes have been proposed, but they generally fail to treat the entire organic load of waste when used in stand-alone technology, while generating higher investment costs in the treatment process. The biological processes turn out to be particularly promising as they are able to produce interesting metabolites from living cells. Among them, production of biogas through anaerobic digestion is by far the most developed and economically viable process for treatment of vinasse. However a few works, also using vinasse as a growth medium, have been published on development of innovative technics to produce single cell products such as lipids, proteins, organic acids, alcohols or enzymes. In the medium term, technologies to produce third generation biodiesel are developing to complement and compete with fuels derived from petroleum. Finally, the development of hydrogen production processes from vinasse is emerging, thus preparing us for a long-term decarbonised economy.