Electrochemical Methods for Protein and Lipid Recovery and Valorization from Waste Activated Sludge

Waste activated sludge (WAS), traditionally considered a by-product of biological wastewater treatment, is increasingly recognized as a valuable source of proteins, lipids, nutrients, and other biomolecules with potential for resource recovery and environmental sustainability. Electrochemical technologies have emerged as promising approaches for WAS valorization because they can promote extracellular polymeric substance disruption, microbial cell lysis, and biomolecule release under controllable conditions. This review examines recent advances in the electrochemical recovery of proteins and lipids from WAS, focusing on the mechanisms governing their release, including reactive oxygen species generation, electron transfer, electroporation, and electro-osmotic effects. Electrooxidation, electro-Fenton, electrocoagulation, bioelectrochemical systems, and hybrid electrochemical processes are compared in terms of treatment conditions, recovery performance, and preservation of biomolecule quality. Particular emphasis is placed on the ability of these technologies to recover proteins and lipids while limiting excessive oxidation that may compromise their structural integrity and subsequent applications. The potential integration of recovered biomolecules into sludge biorefineries for producing biofuels, biomaterials and other value-added products is discussed within a circular bioeconomy framework. Overall, electrochemical technologies represent a versatile pathway for converting WAS from an environmental liability into a source of high-quality biomolecules and renewable products, supporting the transition of wastewater treatment plants toward integrated resource recovery and more sustainable environmental management.