Integrated technoeconomic and environmental assessment of biogenic polyurethane production†

Polyurethane (PU), one of the most consumed materials, is conventionally produced from fossil-based polyols and polyisocyanates. In this case, increasing the PU biogenic carbon content is a strategy followed to enhance its sustainability, e.g., by employing bio-polyols and biogenic polyisocyanates. Bio-based pentamethylene polyisocyanate (PDI-T), with 70% biogenic carbon content, is a prepolymer commercialized for bio-PU production. However, its production route has not yet been widely reported. Thus, herein, a theoretical study was conducted to investigate the manufacturing process of a novel bio-PU gel using castor oil and PDI-T. The biogenic production of PDI-T from molasses was designed. A comprehensive assessment integrating process modelling and simulation, cost estimation, economic analysis, and life-cycle assessment (LCA) methodologies was performed to evaluate the techno-economic and environmental performance of the produced bio-PU. This process showed a molasses-to-PU yield of 0.2 t_bio-PU t_molasses⁻¹, with the economic viability reaching a selling price of $15 000 per ton, i.e., five-times higher than the price of a conventional PU-gel. Cradle-to-gate LCA showed a global warming potential (GWP) of 22.8 kg CO₂e per kg bio-PU, which is four-times higher than the GWP reported in the Ecoinvent database for conventional PU. This methodology allowed the identification of key limitations negatively impacting GWP and production costs, primarily the complexity of bio-PDI-T synthesis, which involves high energy consumption and cumulative emissions from multiple raw materials. This study highlights that substituting fossil-based components with high biogenic carbon alternatives does not always result in climate benefits. Therefore, applying this methodology is pivotal for identifying truly sustainable pathways or suggesting modifications to existing processes, to achieve effective green chemistry transition.