Life cycle net energy and global warming impact assessment for hydrogen production via decomposition of ammonia recovered from source-separated human urine

Abstract

Decomposition of ammonia derived from source-separated human urine is a renewable approach for hydrogen production. Life cycle net energy analysis and global warming impact of scaled-up hydrogen production via this technique are studied in this paper. Ammonia decomposition processes, including fixed-bed reactors with Ru/Al2O3 and Ni/Al2O3 as catalyst options are simulated using the Aspen Plus software, and the results are compared with published data for validation. The life cycle net energy indicators are assessed for three scenarios of ammonia generation: conventional air stripping, microbial fuel cell, and electrochemical cell methods at a unit basis of 1000 kg of H2 production. Results show that the microbial fuel cell process is more energy-efficient and emits lower greenhouse gases. The net energy ratio of the microbial fuel cell method is 1.38, and 1.12, for Ru/Al2O3 and Ni/Al2O3, respectively. A comparative assessment of ammonia generation and decomposition options for environmentally-benign hydrogen production is discussed.