Comparative\nLife Cycle Assessment of Glycerol Valorization\nRoutes to 1,2- and 1,3-Propanediol Based on Process Modeling

Crude glycerol, a\nhigh-volume byproduct of the biodiesel industry,\nhas seen a significant surplus due to the industry’s rapid\ngrowth. It can be a promising feedstock for a range of high-value\nproducts via chemical and biochemical routes. This study thus elucidates\nthe relative environmental performance of two prominent glycerol valorization\ntechnologies, i.e., catalytic hydrogenolysis to 1,2-propanediol and\nmicrobial fermentation (batch and fed-batch) to 1,3-propanediol, using\na cradle-to-gate life cycle assessment (LCA). The LCA was performed\nusing an experimental data-driven comprehensive process model to represent\nan industrial-scale biorefinery, handling 20 833 kg/h of glycerol.\nThe LCA results identified cooling water (18–35.5%) and steam\n(15.2–33.7%) consumption in the distillation and glycerol sourcing\n(33.3–68.1%) as the critical environmental hotspots, which\nshould be focused on while designing the process. The fed-batch fermentation\nprocess was environmentally more benign, with significantly lower\nenvironmental impacts than hydrogenolysis (by 35.2%) and batch fermentation\n(by 48.2%). Integrating effective process heat recovery using pinch\ntechnology reduced the overall environmental impacts by 4.9–11.2%.\nThe environmental performance of the overall processes varied substantially\n(2.4–62.1%) with changes in glycerol sourcing and production\nmethods. Therefore, energy and material recycling with sustainable\nwater and glycerol sourcing can improve the sustainability of the\noverall process.