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An environmental life cycle assessment of a pilot scale microbial electrolysis cell for hydrogen production was performed for the first time in this study. The microbial electrolysis cell system was designed based on the existing pilot plants with urban wastewater flow rate of 65 L.d (-1) at wastewater strength of 500 mg COD.L-1. The effect of the performance parameters of the microbial electrolysis cell on life cycle results was analyzed with SimaPro 8.2.3.0. The results showed that the emissions per kg hydrogen-produced from construction phase are the greatest among all phases of the current microbial electrolysis cell system. An increase in cathodic gas recovery and hydrogen production rate resulted in a decrease in emissions per kg hydrogen-produced from the operation and construction of the microbial electrolysis cell. In addition, the total life cycle emissions decreased with increasing of the cathodic gas recovery and electricity transformation efficiency, and increase with increasing applied voltage. The global warming potential from the operation phase was 18.8 kg carbon dioxide-eq/ kg hydrogen under the following conditions: applied voltage of 0.5 V, electricity transformation efficiency of 90%, and cathodic gas recovery of 90%. Compared with existing hydrogen production and wastewater treatment technologies, the current microbial electrolysis cell technology for hydrogen production from wastewater can still be improved in terms of environmental benefits and technical maturity. Nevertheless, microbial electrolysis cell technology with optimized operation parameters will hopefully become an important choice of hydrogen production and wastewater treatment technology in the future.