Comparative sustainability assessment of bio-based vs mineral-based hydraulic oils.

The choice of hydraulic oils is key to the performance of hydraulic systems and is gaining increasing importance from an environmental perspective. Hydraulic oils are typically derived from either mineral or biological sources, with mineral-based oils being the common choice used in load handling equipment. Despite the widespread use, existing studies concerning hydraulic oils focus on either environmental or technical aspects, with comprehensive assessments integrating economic considerations remaining limited, particularly in the context of large-scale industrial applications. This study was driven by the need to address these gaps through a holistic comparison of mineral and bio-based hydraulic oils across technical, economic, and environmental dimensions, specifically within the context of large-scale load handling operations. The technical assessment results show that bio-based oils perform comparably to mineral hydraulic oils in terms of viscosity index, and even outperform them in certain key parameters, including flash point and pour point. However, the mineral oils showed superior oxidation stability. To evaluate the climate impact, a cradle-to-grave life cycle assessment was conducted, referencing operations in a load handling equipment and including both incineration (with energy recovery) and re-refining to represent the waste oil management in Europe. The results showed a clear environmental advantage of the bio-based oils, with mineral oils generating 75% more greenhouse gas emissions across the base-oil production phase. The inclusion of the end-of-life phase resulted in 63% and 71% more climate impact from the mineral oil compared to the bio-based oil across the full product lifecycle when incineration and re-refining treatment methods are used, respectively. The emission results also show that re-refining is the environmentally friendly waste management option when compared to incineration, showing significant emission reduction potential across both oil types. Furthermore, a sensitivity analysis was carried out to investigate the effect of an improved bio-oil service life on the climate impact. This analysis was driven by input from industry experts and suppliers concerning the potential for an extended oil service life of bio-based hydraulic oils. The findings showed that longer oil service life significantly reduces climate impact, even as much as 98% if paired with a re-refining waste management option, and no oil change is needed across the service life of the load handling equipment. Economically, the results showed that while the mineral hydraulic oils are cheaper when purchased, the potential extended service life of bio-based hydraulic oils may offset the initial cost difference when evaluated over the full lifespan of the equipment, while simultaneously offering external cost benefits through the carbon pricing mechanism. Overall, the three- dimensional results of this study suggest that bio-based hydraulic oils are a viable and competitive alternative to mineral hydraulic oils. While each hydraulic oil option offers certain advantages and limitations, the optimal choice depends on the priorities and operational context of the specific company.