Environmental Assessment of Metal Chip Recycling - Quantification of Mechanical Processing's Global Warming Potential

Material recycling is an essential lever for improving the sustainability of production processes. One way of reusing metal chips that occur as waste in machining or other subtractive manufacturing processes is to mechanically pretreat and remelt them. In mechanical pretreatment, the chips are separated from the cutting fluid by a centrifuge and then briquetted directly on site. This simplifies the handling and makes the transport and subsequent remelting more efficient than in thermal processing alone. The main objective of this work is to quantitatively assess the environmental impacts of the described recycling process, focusing on the global warming potential. Furthermore, recycling by means of mechanical chip processing is compared with alternatives such as thermal drying and primary material extraction. A parametric life cycle assessment (LCA) model has been developed for this purpose. The model considers equipment, material, throughput and location variations to analyze different use cases. The results of the LCA of an exemplary use case show that environmental benefits result from a higher bulk density during transport and a lower energy input during remelting due to a lower liquid content.