Life cycle assessment of bio-based hard carbon for sodium-ion batteries across different production scales

This paper aims to address research gaps surrounding the environmental impact of Hard Carbon (HC) production by conducting a Life Cycle Assessment (LCA) based on data from two laboratories with differing backgrounds and scenarios. HC is commonly used as anode material for sodium-ion batteries, a potentially sustainable and costefficient alternative for lithium-ion batteries. The study identifies environmentally sustainable routes for HC synthesis by comparing various biomass and synthesis pathways. The study reveals that the energy consumption of the pyrolysis process is the primary contributor to the environmental footprint of lab-scale HC production. A prospective LCA is performed by upscaling the laboratory processes to pilot- and industrial scale based on expert judgement and assumptions on energy and material balance. The results show that the environmental profile of HC can be significantly improved when the production scale is expanded. At large production scales, HC shows great potential to be used as a counterpart to graphite in future battery systems. However, direct emissions, such as methane, and the depletion of materials, such as argon and acid, become more critical to the environmental footprint, highlighting the need for energy recovery, emission treatment strategies, and more efficient use of materials. This work provides a framework for future LCA studies of HC, highlighting the limitations of simplified upscaling. It also provides a foundation for developing sustainable energy storage systems, thereby contributing to more informed decision-making in HC industrial production.