Absolute Environmental Sustainability Assessment of Emerging Working Fluids in Organic Rankine Cycles

New working fluids (WFs) have been recently proposed to enhance the environmental performance of Organic Rankine Cycles (ORCs) in waste heat recovery systems. However, a critical gap remains in the comprehensive evaluation of their environmental impacts, particularly those associated with the production of these compounds and their use in ORC systems. This study performs a comprehensive absolute environmental sustainability assessment (AESA) to evaluate the environmental trade-offs of replacing traditional WFs, such as R245fa, with emerging alternatives in ORC systems. An innovative methodology, integrating process simulation, life cycle assessment (LCA), prospective analysis, and the planetary boundaries (PBs) framework, is employed to provide a holistic sustainability assessment. The results show that using emerging WFs reduces 85% of the carbon footprint of ORCs. Although this transition shifts environmental burdens to the ozone depletion impact category, the system remains within the PBs’ safe operating space. The burden of the other environmental impact categories studied is reduced by more than 15%. The prospective analysis highlights that the transition from current to alternative WFs for ORC systems could cut around 237 million tons of annual CO₂ emissions by 2050.