Eco-efficiency assessment of carbon capture and hydrogen transition as decarbonisation strategies in alumina production

Studies seeking to thoroughly couple the environmental and economic performances of a process or product are becoming more prominent as the needs for decarbonisation grow. This study explores the use of Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) in the alumina extraction industry. Models for various thermal energy supply methods and CO 2 mitigation strategies were developed to obtain an inventory for analysis and the environmental impacts and life-cycle costs of the supply chain were evaluated. Finally, economic and ecological results were integrated using eco-efficiency indices and a sensitivity analysis of the most significant variables detected was conducted. The research indicated that the integration of a calcium-looping plant to capture post-combusted CO 2 could reduce 55.5% of the CO 2 equivalent emissions, while also obtaining a better economic performance due to the CO 2 avoided taxes. However, other environmental indicators had slightly more significant impacts because of the additional use of natural gas. The potential use of green hydrogen instead of natural gas could enable a 70.0% reduction in CO 2 equivalent emissions, as well as a reduction in all other environmental indicators studied, except for water consumption. However, transitioning to green hydrogen production could incur higher costs. This study introduced an eco-efficiency ratio index, indicating that CO 2 capture and storage proved to be the most eco-efficient scenario, regardless of economic fluctuations in CO 2 emission taxes. The substitution of natural gas with green hydrogen also emerged as a viable eco-efficient solution, provided electricity prices remain below 0.045€/kWh.