Path to Carbon Neutrality in Wastewater Treatment—From Energy Optimisation to Resource Recovery

• Energy minimization deserves more attention in the existing WWTPs. • Low-carbon treatment processes need to be further developed. • Minimization of CH 4 and N 2 O is as important as energy minimization. • Bio-produced chemicals may have more added value than energy neutrality of WWTPs. Related to the global efforts to minimize climate change, wastewater treatment plants (WWTPs) face increasing pressure to minimize energy use and achieve carbon neutrality. This requires a multifaceted approach: First, energy consumption must be minimized through enhanced energy efficiency in existing WWTPs and the adoption of low-carbon technologies, such as anammox-based processes, aerobic granular sludge, and membrane aerated biofilm reactors. Second, reducing greenhouse gas emissions, particularly nitrous oxide, is as critical as improving energy efficiency. Third, energy recovery should extend beyond conventional methods like anaerobic digestion or sludge incineration to include harnessing effluent heat from treated wastewater. Finally, resource recovery—encompassing nitrogen, phosphorus, and biopolymers—offers greater societal value than energy independence alone. This article critically reviews strategic pathways to achieving carbon neutrality in wastewater treatment, which brings together energy efficiency, greenhouse gas emissions, and energy and resource recovery within a single framework.