Sustainability of biomass pyrolysis for bio-aromatics and bio-phenols production: Life cycle assessment of stepwise catalytic approach

The high-valued utilization of biomass resources remains challenging due to their complex biochemical compositions and limited product selectivity. Herein, we propose a novel biomass stepwise catalytic pyrolysis process to efficiently produce aromatic hydrocarbons and phenols by leveraging the distinct thermal stability of biomass components and their compatibility with ZSM-5 and biochar-based catalysts. A life cycle assessment (LCA) is conducted to evaluate the energy consumption and environmental impact of this innovative process compared to conventional methods. Our findings reveal that this approach significantly reduces the energy consumption by 51.76-90.02 % across different application scenarios of by-product biochar. Additionally, using biochar as a soil amendment contributes to carbon negativity, achieving a net greenhouse gas (GHG) emission reduction of up to 6 t CO2 eq for producing 8.325 t aromatics and 1 t phenol. The first-stage catalytic pyrolysis for producing aromatic hydrocarbons is identified as the major contributor to environmental impact, mainly due to ZSM-5 catalyst usage and loss, while the second stage for phenol production has a comparatively minor impact. Finally, sensitivity analysis of the key parameters highlights areas for process optimization, including reducing catalyst dosage, minimizing energy consumption, and improving phenol yield, which are crucial for enhancing the environmental and economic viability of the entire route. This study provides a detailed LCA and offers insights for future improvements in biomass conversion technology.