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Life Cycle Assessment of Coolant Systems in Metalworking
The use of MWFs is widespread in industrial metalworking, as their cooling, lubricating, and flushing effects enable an efficient and cost-effective machining process. Conventional mineral oil-based metalworking fluids—either water-immiscible or water-miscible—are typically used for this purpose. However, the extraction, production, use, and disposal of mineral oil are associated with a wide range of negative environmental impacts. Furthermore, the choice of metalworking fluid also determines how sustainable a machining process chain is.
Assessment of Environmental Impacts Using Crank Shaft Manufacturing as an Example
A large portion of the metalworking fluid used is carried away during the process as it adheres to the workpiece. Depending on the type of MWF used in the subsequent process step, a time-consuming intermediate washing step is required. To address these issues, Oemeta developed the multifunctional oil HYCUT, which can be used both as a non-water-miscible machining oil and as a water-miscible emulsion. HYCUT was developed using renewable raw materials. The potential environmental impacts of the system were examined in a life cycle assessment.
In collaboration with the Institute for Machine Tools and Manufacturing Technology at the Technical University of Braunschweig, the potential environmental impacts of Oemeta HYCUT were analyzed using a life cycle assessment and compared to those of a conventional, mineral oil-based reference lubricant system.
Application of the Life Cycle Assessment Method at an Austrian Engine Plant
To ensure a comprehensive assessment of environmental impacts, the entire life cycle of a product is considered—from raw material extraction through product manufacturing and use to disposal. Throughout this life cycle, both the resources consumed and the emissions generated by all processes under consideration are recorded and converted into environmental impacts.
The life cycle assessment was conducted as part of a case study at an engine plant operated by a German automaker in Austria. The study focused on the process chain for crankshaft production, which consists of a wide variety of machining processes, such as milling, turning, deep drilling, and grinding. This process chain is characterized by frequent switching between water-miscible and non-water-miscible metalworking fluids (see Figure 1).
In practice, the process chain is already operated using the ester-based HYCUT, which is formulated so that the water-miscible and non-water-miscible components are compatible. Consequently, the cross-contamination of metalworking fluid deposits on components is not an issue, as it is with conventional metalworking fluids.
Compared to mineral oil-based reference products, this results in a significantly more efficient use of metalworking fluids throughout the entire production line, as intermediate washing steps and metalworking fluid losses can be largely avoided.
In particular, the reuse of the cleaning solution from component cleaning as a MWF for machining processes has a positive impact on the life cycle assessment. To fully leverage these benefits, the planners tailored the design of the production line to the process fluid. As a result, several component-cleaning systems that are typically required were not installed.
When the Oemeta HYCUT system is used, environmental impacts across all considered categories are significantly lower (40–60%) over the entire life cycle compared to the reference system (see Figure 2).
For the GWP (Global Warming Potential), a reduction of approximately 470 metric tons of CO2-eq was determined for the annual production in the case studied. This reduction is comparable, for example, to the environmental impact caused by the annual operation of 158 passenger cars.¹ The absolute values determined are case-specific and depend on the basis of comparison, the system under consideration, and the processes included.
The relative values indicate the general trend in the comparison. Thus, the life cycle assessment demonstrated that the use of Oemeta HYCUT in metalworking results in significantly lower environmental impacts than a conventional, mineral oil-based metalworking fluid system with equivalent performance.
See the figure below.
Germany
