Recovery of Value-Added Products from Industrial Wastewaters: A Review to Potential Feedstocks

Abstract

Biorefineries process biodegradable wastes into a range of bio-based products. Several wastes can be used as feedstocks for biorefineries, but liquid effluents, called wastewaters, stand out due their large production flow and pollution potential of water bodies. Noteworthy wastewaters suitable for biorefineries include (i) vinasse, also called sugarcane stillage; (ii) cheese whey; (iii) glycerin; and (iv) cassava wastewater. Vinasse is the main residue of the sugar and ethanol industry and 10–15 L of vinasse are generated per liter of produced ethanol. It has a high organic content (20–25 g COD L 1), low pH, high temperature, and high ash content. Cheese whey is the watery part of milk that is separated from the curd in the cheese-making process. It is the major by-product of dairy industries and it presents high organic load (70–80 g COD L 1), low alkalinity content, high nitrogen content, and very high biodegradability. Glycerol is the major by-product of the biodiesel industry. Crude glycerol (925–1500 g COD L 1), generated by homogeneous base-catalyzed transesterification, contains glycerol, alkalis, methyl esters, and methanol. Cassava wastewater (10–20 g COD L 1) is composed by root cleaning water, cassava milling wastewater, and cassava starch wastewater. It is a milky yellowish liquid with large quantities of nutrients. 202 G. Lovato et al. These effluents production combined was over 3.5 trillion kilos in 2019 and, therefore, pose a huge threat to the environment, but also a great opportunity for biofuels (over 7 1011 Nm3 of biogas per year—hydrogen and methane) and biochemicals production. Thus, the aim of this chapter is to review the production process of these wastewaters and their potential as feedstocks for anaerobic digestion, a wastewater treatment process capable of generating energy (hydrogen and methane) and biomolecules (acids and polymers). © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022.