Biodegradability and cost comparison of polyhydroxyalkanoates-based composites with industrial waste and by-products...

This study investigated the biodegradability of polyhydroxybutyrate (PHB)-based composites compounded with industrial waste and by-products under mesophilic anaerobic conditions. Six formulations were produced via twin-screw extrusion with 30 wt% diverse fillers, including solid digestate (SD), dried distillers' grains (DDG), brewer's spent grain (BSG), spent coffee grounds (SCG), insect frass (IF), and biochar (B). Pure PHB achieved a biodegradability of 103 % after 177 days. Except for the PHB-SD and PHB-B composites, all PHB-based composites achieved over 90 % biodegradability within 120 days, with PHB-DDG and PHB-BSG composites reaching this level in only 42 and 76 days, respectively. Interestingly, the incorporation of fillers not only accelerated methane production kinetic, aligning better with industrial hydraulic retention times, but also reduced material costs by approximately 20 %. These findings validate PHB-based composites as viable, cost-effective and environmentally sound alternatives to conventional plastics, promoting industrial waste and by-products valorization within a circular economy framework.