Chapter 37 - Superabsorbent materials from industrial food and agricultural wastes and by-products

Abstract

The global superabsorbent materials (SAMs) market was estimated at €7.5 billion in 2017 and is expected to keep growing annually at a rate of 6.2%. Most SAMs used nowadays are based on acrylic derivatives, but their toxicity, low biodegradability, and petrochemical nature, together with their high price and incompatibility with agricultural land and underground water, have increased the interest in novel superabsorbent biopolymers (SABs). These alternative SABs can be obtained from different natural resources (e.g., cellulose, starch, blood plasma, gelatin, chitosan, etc.) that are by-products or biowastes from different food and agricultural industries. Therefore the development of this new generation of SABs enhances the biocompatibility and biodegradability of the pursued products, as well as the sustainability of several industrial segments. This new generation of biopolymers also involves changes in material processing since nowadays most fabrication procedures are based on graft copolymerization of vinylic monomers (e.g., acrylonitrile, acrylic acid, acrylamide) onto natural polymers (starch, cellulose and their derivatives), but there are emerging studies focusing on protein-based SABs. This chapter presents an overall diagnosis of the current state of SABs. First, a summary of the work carried out on polysaccharides, proteins, or graft copolymers is made. Then, different strategies performed for producing SABs based on protein sources from agri–food wastes and by-products are highlighted.