BIOCASCADING APPROACH IN THE AGRO-RESIDUES VALORIZATION: THE BIOCOMPOSITE PRODUCTION AS A PROLIFIC CONTRIBUTION TO THE CIRCULAR ECONOMY

The increasingly pressing demand of civil society to move towards the circular economy models drives the scientific community to explore new routes to fully valorise wastes in order to achieve the zero-waste objective. From this perspective, even the residues of agro-industrial processing must not be considered as a waste, the disposal of which involves an economic cost, but as a potential source of valuable products. Indeed, this kind of leftover biomasses and food production by-products can be particularly rich in proteins, carotenoids, polyphenols, caffeine, and fibres, which could find application in various sectors as food, nutraceuticals, cosmetics and packaging. Within the PROLIFIC project, a range of green and innovative processing technologies to recover significant amounts of the above-mentioned value-added compounds from industrial processing 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) has been tested and developed. The protein extraction has been performed by using environmentally friendly aqueous extraction (EFAE), enzyme-assisted extraction (EAE) and 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 biocascading approach allows actually collecting interesting compounds but also produces an ultimate fibrous waste, which, with the purpose to keep it into the circular economy loop, can be differently 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 but retained mechanical properties. Composites based on biodegradable and bio-sourced polymers have been successfully prepared by melt-mixing, with the extracted residues in different ratio but without any additive. All the materials are characterized by high thermal stability and in any case, the temperature of thermal degradation resulted far higher than the polymer processing temperatures. The addition of residues has not affected the crystallization and melting processes of the polymeric matrices. The tensile tests have shown 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. Then, the results demonstrate that also the ultimate agro-residues, after the extraction of high value molecules, can be successfully exploited. Finally, it is notable that the obtained material costs can be remarkably reduced and applications in different packaging sectors, such as cosmetic area and food industry, can be taken into consideration.