Environmental and economic relevance of hydrogen co-production during electrochemical phosphorus recovery from cheese whey wastewater

Hydrogen is a by-product of electrochemical phosphorus removal, but its environmental and economic relevance has rarely been assessed. In this work, two electrochemical routes were evaluated: an Mg-assisted electroless system (AZ31 anode and stainless-steel cathode), expected to favor struvite precipitation, and a current-driven system (Ti/IrO 2 -Ta 2 O 5 anode and stainless-steel cathode), expected to favor Ca-phosphate precipitation. Under the baseline scenario, the current-driven Ca-phosphate-oriented route showed higher environmental impacts than the Mg-assisted route in 16 ReCiPe Midpoint categories. Its environmental performance improved markedly when hydropower was considered, demonstrating that the relative ranking of the two routes is strongly dependent on electricity supply. H 2 generation ranged from 1.9 to 2.7 m 3 H 2 m −3 d −1 , accounting for 10–50% of environmental credits and 69% of the revenue. These values may be improved through continuous gas removal. This study provides experimental evidence of the environmental and economic contribution of H 2 for electrochemical P recovery and identifies further research priorities.