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

Area of Science:

• Environmental Science
• Chemical Engineering
• Sustainable Energy

Background:

• Human urine is a nitrogen-rich resource with potential for nutrient and energy recovery.
• Urea electrolysis is explored for simultaneous nitrogen removal and hydrogen (H2) production from urine.
• Previous claims on H2 production potential from urine-derived urea relied on flawed calculations.

Purpose of the Study:

• To reassess the global H2 production potential from urine-derived urea.
• To address the translation gap between synthetic matrices and real urine in electrocatalyst studies.
• To guide future research priorities in urine valorization and nitrogen management.

Main Methods:

• Utilized geographically resolved protein supply data for 185 countries to estimate H2 production potential.
• Performed a critical re-evaluation of existing literature and calculation methodologies.
• Advocated for benchmarking electrocatalyst performance in real urine or validated surrogates.

Main Results:

• Global average annual H2 production potential from urine is estimated at 0.71 kg H2 cap⁻¹.
• This potential is insufficient for large-scale H2 supply, equivalent to only 5.8% of current global H2 production.
• A significant gap exists between research on synthetic urea and performance in actual urine.

Conclusions:

• Urine-based urea electrolysis is not a viable scalable global H2 production route.
• This technology may hold value in niche applications or integrated nitrogen management systems.
• Research should focus on realistic benchmarking in real urine and system-level comparisons for nutrient recovery.