A contribution to the circular economy concept: biocomposites based on fully valorized agro-industrial residues.

The increasingly pressing demand of civil society to move towards the circular economy model drives the scientific community to explore new routes to fully valorise wastes and by-products in order to achieve the zero-waste objective. From this perspective, the agro-industrial residues can be considered a potential source of valuable products, which could find application in different fields. Within the H2020 PROLIFIC project, a cascading approach based on green and innovative processing technologies has been designed to recover significant amounts of value-added compounds from industrial residues of legumes (seeds of peas, beans and chickpeas), fungi (cuttings and mycelia of different species), and coffee (silver skin residue and not compliant roasted seeds). The protein extraction has been performed by using environmentally friendly aqueous extraction (EFAE), enzyme-assisted (EAE), ultrasound-assisted (UAE), and microwave-assisted (MAE) extractions. The resultant residues have been further exploited by using supercritical CO2 extraction (SFE-CO2), subcritical water extraction (SWE), and alkali extraction to recover polyphenols, caffeine, and fibres. The described extraction sequence produces an ultimate fibrous waste, which can be further valorised. In fact, it is well-known the use of natural fibre residues as filler in polymeric matrices to prepare bio-composites, characterized by decreased costs and retained mechanical properties. New composites based on biodegradable and bio-sourced polymers have been successfully prepared by melt-mixing, using the extracted residues in different ratios, without any additional additive. All the materials are characterized by high thermal stability: indeed, the temperatures of thermal degradation result higher than the polymer processing temperatures. The tensile tests show an increment in the Young modulus and a decrement in both the strength and the elongation at break consistent with filler loadings. However, for a reduced amount of filler, the overall properties of the matrix have been retained. Upscaling of the best formulations are in progress. Then, the results demonstrate that also the ultimate agroresidues, after the extraction of high-value molecules, can be successfully exploited to produce biocomposites for packaging applications at reduced costs.