Making waves: Rethinking hydrogen production from human urine through urea electrolysis

Source-separated human urine is a nitrogen-rich stream with strong potential for resource recovery. Among proposed routes, urea electrolysis has received considerable recent attention for coupling nitrogen removal with electrolytic hydrogen (H₂) production. Yet, widely cited claims of H₂ production potential from urine-derived urea rest on a flawed calculation in the literature, and fundamental questions about the practical viability of this pathway remain unanswered. Here, we reassess this potential using geographically resolved protein supply data for 185 countries. We show that even under idealized assumptions, average annual H₂ production potential from urine is only 0.71 kg H₂ cap^-1 globally, which is barely sufficient to power a fuel cell vehicle for ∼75 km, and equivalent to 5.8% of current global H₂ production. At the same time, the literature remains dominated by synthetic urea-rich matrices, creating a translation gap that requires benchmarking electrocatalyst performance in real urine or validated surrogates. We argue that urine-based urea electrolysis cannot become a scalable global H₂ production route but may retain value in selected niche applications or as part of nitrogen management systems where H₂ production is a co-benefit. We therefore call for a recalibration of research priorities, with clearer separation between fundamental electrocatalyst studies and applied claims, more credible benchmarking in real urine, explicit accounting of nitrogen fate alongside H₂ production, and system-level comparison against other urine processing technologies for nutrient recovery and nitrogen management.