Strategic biorefinery platform for green valorization of agro-industrial residues: A sustainable approach towards biodegradable plastics

Abstract

The production of cellulose reinforced bio-composites has emerged as an efficient bio-sustainable alternative for high-quality functional polymeric materials to replace the presently dominated petroleum-based plastics. Also because, lignocellulose biorefinery from waste agro-industrial residues has attracted widespread attention for combating increasing environmental pollution caused by incineration of such wastes. In this prospect, the fractionation of tender coconut husks (TCH) to yield cellulose, hemicellulose and lignin fractions has been investigated by different pretreatment methodologies using conventional and novel reaction media. Excellent outcomes were obtained with the use of the deep eutectic solvent composed of choline chloride and oxalic acid dihydrate that led to the dissolution of 95.5% of the initial lignin in TCH to yield a cellulose fractional recovery of 87.5% at the optimal conditions attained by parametric variations. Interestingly, the same eutectic mixture also functionalized the obtained cellulose to cellulose nanocrystals (CNC) with 69% yield, crystallinity index of 88.6% and average particle size of 146 nm. Further, isolated starch from waste tamarind seeds was used as the polymer matrix wherein the CNC was added as a suitable bio-filler to cast bioplastic films using biodiesel byproduct glycerol as a plasticizer. The characterization of the biodegradable films revealed a tensile strength of 21.8 MPa along with outstanding thermal and moisture barrier properties. The results elucidate that the huge dependence for petro-plastics could be reduced with the integrated valorization of solid wastes that can aid wide-ranging industries and align with the rising motto of a bioeconomy.