Desalination, nutrients recovery, or products extraction: Is electrodialysis an effective way to achieve high-value utilization of liquid digestate?

• K + , NH 4 + , and Cl − were components with higher migration priority during ED. • Percentage removal of salt ions reached over 90% • ED recovered 35–70% N and P and extracted 70% VFAs from liquid digestate. • Organic molecules with benzene rings and carboxyls were easier to foul the membrane. • Agriculture application and VFAs products showed economic benefits about 20 USD/t-digestate. With the wider application of anaerobic digestion in food waste treatment, the digestate management becomes the bottleneck either from economic or carbon mitigating point. The high salt content in food waste digestate hinders the mass agriculture application. In this study, electrodialysis was performed to assess the performance of desalting from mature and fresh liquid digestate as well as the migration patterns of nutrients and value-added products. K + , NH 4 + , and Cl − were found to be the components with higher migration priority. Current efficiency (CE) for desalination scenario was about 35–50% while NH 4 + in mature digestate (MD) contributed about 50–55% of the cationic CE and volatile fatty acids (VFAs) in fresh digestate (FD) contributed about 20–25% of the anionic CE. Organic carbon in MD was well retained, whereas 49%-63% organic carbon in FD experienced migration, which is more obvious at neutral pH. Electrodialysis removed over 90% salts and recovered 35–70% N and P from both mature and fresh liquid digestate, and extracted 70% VFAs from FD. This is expected to save the cost in wastewater treatment of 19.46 USD/t-digestate or obtain a benefit of 17.36USD/t-digestate from VFAs product. But the membrane fouling brought great uncertainty to the operating costs. Compared with cation exchange membrane, more severe membrane fouling was found in anion exchange membrane, whose performance decreased to half of the original by the end of the experiment. Organic molecules with benzene rings and carboxyls were mainly responsible for the membrane fouling.