|Title||Characterizing the influence of resource-energy-exergy factors on the environmental performance of additive manufacturing systems|
|Publication Type||Journal Article|
|Year of Publication||2018|
|Authors||Nagarajan, HPN, Haapala, KR|
|Journal||Journal of Manufacturing Systems|
|Pagination||87 - 96|
|Keywords||Additive manufacturing, Energy efficiency, Environmental performance, Exergy analysis, Life cycle assessment|
Additive manufacturing is rapidly emerging as an alternative to conventional manufacturing, including subtractive processes, often attributed to its claim for sustainable product development, e.g., reduced cost, reduced energy and material use, and the distributed production of tailored consumer products. However, many of these benefits remain unsubstantiated for large-scale production. The aim of the research herein is to identify and characterize the factors influencing the systemic environmental performance of additive manufacturing as an end use of energy, using exergy analysis and life cycle assessment. These methods have been previously applied to evaluate the environmental performance of conventional and non-conventional manufacturing processes, and offer a validated approach to explore the environmental impacts of additive manufacturing with respect to systemic material and energy losses. In this study, the environmental impacts of direct metal laser sintering (DMLS) of iron metal powder and fused deposition modeling (FDM) of acrylonitrile styrene acrylate polymer filament are characterized by performing a thermodynamic (exergy) analysis of the resources and energy utilized and lost from cradle to gate. It is found that only 10% of total DMLS process inputs contribute to material processing, while 90% of the inputs are lost as bulk waste, heat, and work. For FDM, it is found that only 7% of total process inputs contribute to material processing, while 93% are lost. Following the exergy analysis, life cycle assessment is performed to characterize the environmental impacts of the exergy losses using single-issue indicator (Global Warming Potential, GWP) and aggregate indicator (ReCiPe 2008) methods. The results show that electricity consumption is a key contributor to both focal processes and their related upstream processes. The systemic GWP for DMLS is 69 kg CO2 equivalent, while for FDM it is 89 kg CO2 equivalent, per kilogram of material processed. Using the ReCiPe 2008 method, damage to human health is predicted to outweigh damage to ecosystem quality and resource availability for the DMLS process. For the FDM process, damage to human health and resource availability are predicted to outweigh damage to ecosystems quality. This work concludes that electrical energy use is the key contributor to systemic environmental impacts of additive manufacturing. Thus, it is imperative that we identify solutions to generate clean electrical energy, reduce electricity transmission losses, reduce material processing energy use, and design products that enable efficient additive manufacturing.