Preliminary economics for green ammonia synthesis via lithium mediated pathway

Abstract

High energy density liquid fuel, ammonia, faces increasing interest globally as a carbon-free energy carrier that can be transported over long distances for decentralized and remote distribution. The dominant ammonia production method, Haber-Bosch, is both energy and carbon intensive to overcome the slow kinetics of the ammonia synthesis reaction from nitrogen and hydrogen. An early techno-economic model for lithium mediated electrochemical ammonia synthesis at mild process conditions using feed rates of 27 metric ton/day for lithium hydroxide, 127 metric ton/day for cryogenic nitrogen and 264 metric ton/day electrolysis grade water is presented. Further analysis was carried out to analyze the energy consumption and reduction per metric ton of ammonia in comparison to electrochemical ammonia using H+ conductive membrane and small-scale Haber-Bosch technology. Electrochemical ammonia synthesis using lithium-ion conductive membrane coupled with nitrogen generation by cryogenic distillation was found to be a sustainable pathway. The ammonia production cost via lithium mediated pathway was estimated to be less than $700 per metric ton and was found to be comparable with costs using traditional Haber Bosch. The environmental impact of electrochemical ammonia using the alkali group 1 metal, lithium, was also assessed from cradle to product.

Cost and Performance Targets for Fully Electrochemical Ammonia Production under Flexible Operation

“…10 Yet, the vast majority of TEA studies focus on thermochemical ammonia production using hydrogen derived from renewable energy-powered electrolysis, sometimes analyzing the effects of intermittency in the power supply as a result of wind or solar energy being used to directly supply power to the process. [30][31][32][33][34] Far fewer analyses have assessed the techno-economic fundamentals of fully electrochemical ammonia production; 3 those that have either assume continuous operation or model intermittent operation under heavily simplifying assumptions. 4 Here, we set out to holistically evaluate the cost-optimal design and operation of fully electrochemical ammonia production using realistic power intermittency data for a mix of solar and wind power sources deployed in various locations in the contiguous United States.…”

“…However, despite laboratory-scale reports of fully electrochemical ammonia generation processes of all stripes, − these approaches are nearly universally assessed to lack the efficiency and robustness required to produce ammonia economically at scale in their present form. Techno-economic analyses of renewable ammonia production have been performed, though most focus on thermochemical ammonia synthesis using hydrogen derived from renewable-energy-powered electrolysis. − Far fewer analyses have assessed the techno-economic fundamentals of fully electrochemical ammonia production which utilizes electrochemical nitrogen reduction to produce ammonia; those that have either assume continuous operation or model intermittent operation under heavily simplifying assumptions …”

“…At unity (100%) Faradaic efficiencies, the overpotential of the reaction must be ≤2.45 V to maintain energy efficiencies ≥ 32%. This finding implies that lithium-mediated nitrogen reduction, which often demonstrates high FEs but requires overpotentials in excess of 3 V, ,,,, also requires fundamental modifications to decrease the overpotential for economic viability of the chemistry.…”

Environmental and economic potential of decentralised electrocatalytic ammonia synthesis powered by solar energy

“…It however revealed the occurrence of burden shifting, i.e., one impact improves at the expense of worsening others in biomass-based routes which could exacerbate the damage to the biosphere integrity. 10 From a technical viewpoint, it was pointed out that producing green ammonia at scale would require large amounts of expensive electrical power in the WE [14][15][16]33 and in the eN 2 R [34][35][36][37] routes, making them economically unattractive in the foreseeable future. Specifically, electricity prices as low as 0.025 USD 2020 kW h À1 in a decarbonised grid below 180 g CO2 kW h À1 (41% lower than the European grid intensity 38 ) would be required for centralised green ammonia using WE to become economically and environmentally appealing.…”

Techno-Economic Analysis and Life Cycle Assessment of Hydroxylamine Eco-Manufacturing via Wastewater Electrochemical Reduction

“…A few models in the literature perform TEA of the CO 2 electroreduction (CO 2 ER) pathways to various chemicals. They include Leow et al, Bushuyev et al., Ozden et al, Verma et al, Jouny et al, Shin et al, and Na et al Gomez and Garzon used their model for NH 3 production cost calculation, and James et al used it for solid oxide fuel cells (SOFC) and proton exchange membrane systems (PEMs) . (details in the SI)…”