Life cycle energy and greenhouse gas emissions implications of polyamide 12 recycling from selective laser sintering for an injection-molded automotive component

The selective laser sintering (SLS) process generates waste polymer powders, which can be recycled as feedstock for producing injection-molded components. Recycling this powder has implications on the life cycle modeling of the SLS product, as well as the subsequent injection-molded component. This study investigates the life cycle primary energy demand (PED) and global warming potential (GWP) of an automotive fuel-line clip produced with recycled polyamide 12 (PA12) from an SLS process in comparison to the conventional polyamide 66 (PA66) counterpart, based on real-world industry data. In addition, the life cycle PED and GWP of an SLS part are examined, with and without recycling PA12 from the SLS process. The results indicate a strong dependence on the approach to evaluate the environmental burden of waste PA12 from the SLS process (cut-off, mass-based allocation, economic allocation, and substitution). Compared with the PA66 fuel-line clip, the recycled PA12 (rPA12) clip reduces the life cycle GWP by up to 26% (cut-off) or increases by up to 68% (mass-based allocation). For the SLS part, recycling PA12 powder provides a 42% reduction to its life cycle GWP (mass-based allocation). Finally, from an expanded two-part system perspective, the recycling of PA12 from the SLS process provides an 8% reduction in life cycle GWP. Similar trends are shown for the life cycle PED profiles. This study demonstrates the importance of recycling additive manufacturing (AM) wastes within a broader cascading system to improve the environmental performance of AM and the circular economy across industrial systems.