Strategic and green valorization of paper mill wastes within the circular economy framework

The urgent global challenges related to energy lack and environmental issue drive the industrial sector to search for innovative solutions for waste resource utilization within a circular economy framework. Among the many difficulties faced by the paper industry, the significant production of waste sludges (Mton/year) stands out, imposing substantial landfill costs and environmental impacts. To address this challenge, the collaborative project with Lucart Company aims to investigate and optimize the valorization of two distinct types of waste sludges: cellulose and inorganic ones. Regarding the first one, the main objective was to convert the cellulose-rich sludge into high-value-added platforms and biofuels, specifically alkyl levulinates (ALs), through direct alcoholysis of its C6 fraction. On the other hand, regarding the valorization of the inorganic-rich sludge, mainly composed of CaCO3 with a minor cellulose fiber component, two approaches were pursued: i) integration of the bulk inorganic sludge into biodegradable materials, such as poly(lactic acid) and polycaprolactone, as eco-friendly alternatives to conventional cellulose and mineral fillers; ii) selective recovery of CaCO3 through thermochemical processes, including pyrolysis and combustion treatments under mild reaction conditions. This project shows concrete possibilities for the paper industry, offering various valorization methods, at the same time, paying attention to environmental impact and economic feasibility.