Valorization of coco coir into biocomposite materials through water-based chemistry

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In this paper, an eco-friendly approach was reported to fabricate coco coir composites through water-based chemistry. The novelty of this approach lies in the water-based chemical methodology as well as the applicability of the fabricated coco coir biocomposites as proper growth media for hydroponics. In the fabrication process, the coco coir was first made reactive via azo coupling the aromatic structures of its lignin with bifunctional linkers. The reactive coco coir was then cross-linked with polyvinyl alcohol (PVA) to produce coco coir composites. Since the fabrication process was performed with water as the solvent at moderate reaction temperatures and the only byproducts were harmless inorganic salts, it is more sustainable than other existing chemical processes that employ organic solvents and produce volatile organic harmful compounds (VOCs). Additionally, a two-factor study was conducted to determine the main and interaction effects of different mass ratios of bifunctional linkers and PVA to coco coir on the bulk density and mechanical compressive strength of the coco coir composites. To highlight the applicability of our work, the carbon-to-nitrogen ratio (C/N), water holding capacity, electrical conductivity, and substrate acidity of the composites were measured to verify their suitability for hydroponic applications. The coco coir composites were shown to be durable for use as growth media to support the growth of kale (Brassica oleracea) and cherry tomato (Solanum lycopersicum) plants in a recirculating hydroponic system.