Life Cycle Assessment of Laser Induced Lignin Graphitization

Sammanfattning

This study presents a cradle-to-gate life cycle assessment (LCA) of bio-based graphene production via laser-induced graphitization (LIG) of lignin. The assessment was performed using the ReCiPe 2016 midpoint (H) method with a functional unit of 1 g of graphene. The study investigates two lignin types, lignosulfonate and kraft lignin and two laser configurations, CO2 and fiber laser through three case designs. Environmental impact of lignosulfonate based selected case, that utilizes reusable silicon carbide (SiC) substrate, was evaluated across 18 midpoint impact categories. Electricity consumption was identified as the dominant environmental hotspot, accounting for approximately 89% of global warming potential (GWP), driven primarily by the laser graphitization step and the auxiliary ventilation system. Among material inputs, lignosulfonate and 2-hydroxyethyl cellulose (2-HEC) were the main contributors, while the SiC substrate, amortized for 600 reuse cycles, contributes negligibly to all impact categories per functional unit. Among the assessed cases, the fiber laser configuration resulted in higher impacts than the CO2 laser, driven by longer processing times and consequently higher energy consumption. Scenario and sensitivity analyses demonstrate that graphitization yield is the most influential parameter, with yield improvement reducing GWP by over 70%. Ventilation energy optimization and renewable electricity sourcing provide further reductions, and a combined improvement scenario achieves an overall GWP reduction exceeding 85%, demonstrating a clear and technically achievable pathway toward competitive environmental performance. At current laboratory-scale performance, the LIG process exhibits higher GWP than commercial graphite production routes, consistent with the early-stage development status of the technology. This study provides a transparent, multi-category environmental baseline for lignin based LIG incorporating a reusable SiC substrate, a substrate configuration not previously assessed in LIG life cycle assessment literature. The findings show that although current laboratory-scale performance is not yet competitive with commercial graphite routes, targeted improvements in graphitization yield, ventilation efficiency, and electricity sourcing could offer a quantified and credible route toward more sustainable graphene production.