From waste to value: Membrane technologies for agri-food waste valorisation, resource recovery, water reuse, and circular bioeconomy applications

The agri-food sector has experienced a fast growth, leading to the production of huge amounts of waste and by-products that create significant environmental, economic and resource management problems. Although proteins, polysaccharides, antioxidants, and nutrients are present in these residues, a significant percentage of them are still wasted due to the lack of efficient technologies for recovering these materials, processing costs, and concerns about quality and safety. In this context, membrane technologies have proven to be promising sustainable solutions for the selective recovery and valorization of valuable components from complex agri-food wastes. A critical review of advances in membrane-based processing, including microfiltration, ultrafiltration, nanofiltration, membrane emulsification, membrane bioreactors, and membrane distillation, is presented. Several studies reviewed found recovery efficiencies greater than 80–95% for valuable bioactive compounds, while energy consumption was significantly lower for the integrated membrane systems than for the conventional thermal separation processes. In addition, integrated and hybrid membrane designs have been shown to offer great potential for co-recovery of resources, wastewater treatment, and intensified processes within circular bioeconomy schemes. The future development of the valorization of agri-food waste will rely on the development of fouling resistant membrane materials, on the development of intelligent optimization strategies to the process and on the development of scalable hybrid systems which can be used under industrial conditions. Membrane technologies are projected to be essential for enabling and supporting the effective and efficient utilization of agri-food waste as a resource rather than a burden, thereby contributing to sustainable production systems, improved resource efficiency, and the transition to a circular bioeconomy.