Toward sustainable metal additive manufacturing: Environmental hotspots and circularity pathways

Metal Additive Manufacturing (MAM) is the method of producing three-dimensional objects based on a digital model by layer-by-layer material addition. MAM is important for the transition to a Circular Economy because of its various advantages over conventional production. It improves performance by optimizing complicated parts design, which was previously hard to fabricate. This study aims to assess the environmental and circularity potential of the MAM process, including ingot and powder production steps. Data collection was carried out through MAM prototyping, ingot, and powder production facilities. MAM production is evaluated for Laser-Based Powder Bed Fusion (PBF-LB) and Electron Beam Powder Bed Fusion (PBF-EB) techniques by focusing on their energy and material flow. This integrated evaluation process includes Carbon footprint (CF) analysis and Material Circularity Indicator (MCI) calculations. It was found that total carbon emissions are 124.86 kg CO₂-eq/kg for PBF-EB, 281.18 kgCO₂-eq/kg and 435.58 kg CO₂-eq/kg for two different PBF-LB machines. Energy use was mainly from MAM machines, followed by post process and auxiliary equipment which highlights that energy efficiency in this stage is quite important in environmental performance. Moreover, material circularity was found to be a complementary indicator to be 0.33 for this facility. It was identified that circularity performance could be increased by 118 % with existing methods in the literature, highlighting that the effects of small improvements in material use can have a high impact. These findings contribute to a better understanding of environmental and circularity performance and can be utilized for other additive manufacturing methods.