Sustainability analysis of electrochemical direct air capture technologies

Global warming caused by anthropogenic greenhouse gas emissions, particularly carbon dioxide in the atmosphere, has garnered significant attention due to its detrimental environmental impacts. Carbon capture from both point and dilute sources is amongst the critical technologies needed to mitigate these negative phenomena. Carbon dioxide capture from flue gas is a well-established technology, while carbon capture from the air through direct air capture processes remains under research and development. In recent years, attention has focused on fully electrified direct air capture systems as potential candidates for large-scale direct air capture applications capable of exploiting renewable energy sources. However, economic and environmental analyses are missing in the literature. In this work, a scale-up analysis of different electrified direct air capture technologies (based on electrolysis, bipolar membrane electrodialysis, electro-swing adsorption, and proton-coupled electron transfer systems) is conducted through a hybrid learning curve methodology in order to evaluate total costs and environmental impact (according to scopes 1 and 2). The analysis is conducted for different geographic locations, times of year, and types of renewable energy source. Results show that electro-swing adsorption and proton-coupled electron transfer processes are both characterized by lower costs and environmental burdens, while electrolysis and electrodialysis systems have higher costs and environmental impacts. A technique for order preference by similarity to ideal solution analysis is carried out to determine the most sustainable process considering technical, economic, social, and environmental aspects. Results indicate that the proton coupled electron transfer system, built in China, in 2040–2050, exploiting wind offshore energy is the most sustainable process.