Using life cycle assessment to measure the environmental performance of catalysts and directing research in the conversion of CO₂ into commodity chemicals: A look at the potential for fuels from 'thin-air'

This study uses the life cycle assessment (LCA) environmental management tool to measure the performance, at laboratory scale, of a range of iron and palladium based nanoparticle catalysts for carbon dioxide utilisation (CDU). The catalysts combine the reverse-water gas shift reaction with the Fischer-Tropsch process to convert carbon dioxide (CO₂) into hydrocarbons (HCs) often employed as fuels and feedstocks for the chemical industry; offering the potential synthesis of HCs void of fossil fuel extraction. The catalysts operational performance was shown to vary considerably dependent on the specific iron:palladium loadings. LCA results afforded insight into 'green' catalyst design, palladium addition vastly improves catalyst performance. However, with such a high embodied environmental impact a trade-off is witnessed whereby the continual addition of palladium, although shows favourable CO₂ conversion and HC yields, does not return a sufficient environmental offset in terms of produced HCs to cover the embodied impacts present in its formation. With the present laboratory setup their embodied environmental impacts are several orders of magnitude more impactful than traditional process pathways, largely due to the electricity use; a switch to renewable generators can reduce the overall process impacts by 90%, a significant step in increasing the competitiveness of the process, a use of renewable electricity in the synthesis of hydrogen further strengthens the case for its use in HC production has environmental merit. Indeed, from a material exchange perspective the H₂ consumes is of a lesser environmental impact than those offset through the HCs produced. As with all laboratory processes, it is very likely that process scale-up and refinement will further enhance the results witnessed in this study.