Electromembrane processes for waste valorization: Energy recovery and storage

This article reviews the most recent advances on the contribution of electromembrane-based technologies to waste valorisation through their implementation in the sustainable recovery and storage of energy from waste streams. Two driving forces are considered, salinity and pH gradients. Recent advances and challenges in ion exchange membranes (IEMs) and bipolar membranes (BPMs) are presented. Reverse electrodialysis (RED) and reverse bipolar membrane electrodialysis (RBMED) are evaluated as primary batteries to harvest energy from salty streams. The potential of combining RED/ED and RBMED/BMED as sustainable secondary batteries is also presented. Overall, it is concluded that increasing the membrane performance is a key aspect to rise the maturity of the proposed technologies along with their adaptation to the different characteristics of current and future waste streams potentially available for energy recovery and storage.