3D Printing and Industrial Ecology

Abstract

Why a special issue on additive manufacturing in this journal? Or, perhaps the more precise question is, why so many mechanical engineering and environmental health articles An important implication of the complexity of assessing the environmental implications of 3D printing is that its adoption…will not automatically generate net environmental benefits.…[C]areful, systematic, and quantitative analysis …[is needed] if the enthusiasm for the disruptive potential for the technology is to be balanced against…, say, the recyclability of specialized polymers, metals, or mixed materials…or the possibility of dramatic increases in throw-away products facilitated by endless customization. (Imagine being able to produce shoes, costume jewelry, or household goods in varied colors or ornamentation on demand. This could bring fast fashion to a whole new level.) in a journal on industrial ecology (IE)? 3D printing, or as it is more typically called by engineers, additive manufacturing (AM), has been heralded as both a revolution in production and an opportunity for dramatic environmental advance. While most known to the public as machines similar to ink-jet printers in homes, maker labs, and hobbyist settings, it is actually a family of technologies primarily used in industry. These technologies share the characteristic of producing objects based on digital information by adding successive layers of materials—thus the label additive manufacturing—rather than removing materials (prompting the retronym, subtractive manufacturing, to refer to conventional manufacturing). AM is of interest to industrial ecologists for a variety of reasons. These include the potential for localization of production and the concomitant reduction in transportation of goods, zero-waste manufacturing, and increased availability of spare parts. More subtly, 3D printing is one of a series of technologies that have been viewed as a source of autonomous environmental improvement. And, finally, 3D printing is yet another technology on which life cycle assessment (LCA), a key tool in IE, can shed light regarding environmental benefits andimpacts. Interestingly, as the review by Kellens and colleagues (2017) in this issue shows, much of the environmental research to date on 3D printing has focused on energy use during production (often labeled as “specific energy” in that literature). Some papers in this special issue advance this line of research (see, e.g., Yang et al. 2017; Gutowski et al. 2017). Others, however, bring well-known IE tools such as LCA (Baumers et al. 2017a; Cerdas et al. 2017; Faludi et al. 2017; Huang et al. 2017; Walachowicz et al. 2017; Priarone et al. 2017), life cycle costing (Mami et al. 2017; Huang et al. 2017), and eco-efficiency to bear (Díaz Lantada et al. 2017; Mami et al. 2017). It is hoped that the papers on emissions from 3D printing (Bours et al. 2017; Azimi et al. 2017; Graff et al. 2017; Mendes et al. 2017) and unit energy consumption will contribute building blocks to future LCA and other systems-oriented work that is typical of IE. The special issue nonetheless provides insights on topics central to IE such as the impact of 3D printing on supply chains (Holmström and Gutowski 2017) and localization of production enabled by 3D production from an environmental perspective (Cerdas et al. 2017; Holmström and Gutowski 2017). Three papers examine waste generation in 3D printing—one that proposes threshold criteria as part of an evaluation framework for evaluating human health and environmental impacts (Bours et al. 2017), one that compares material (and waste)-related impacts in additive and subtractive manufacturing (Priarone et al. 2017), and a third relating to design of the supports that are “printed” as part of the object being produced and subsequently discarded (Díaz Lantada et al. 2017). Two papers address repair processes (Peng et al. 2017; Walachowicz et al. 2017), though not for consumer goods in the manner envisioned in the popular literature. None of the papers focus on spare parts production nor do any explore the behavioral or consumer dimensions of localized production. These topics need careful, systematic, and quantitative analysis if the enthusiasm for the disruptive potential for the technology is to be balanced by consideration of, say, the recyclability of polymers, metals, or mixed materials used in nonindustrial settings or the possibility of dramatic increases in throw-away products facilitated by endless customization. (Imagine being able to produce shoes, costume jewelry, or household goods in varied colors or ornamentation on demand. This could bring fast fashion to a whole new level.) Put another way, much of the research on the environmental dimensions of 3D printing has focused on benefits and impacts in production. That research needs to be complemented by more environmental analyses of the production of materials used in 3D printing and related upstream impacts (Faludi et al. 2017; Priarone et al. 2017), on how 3D products are used, and on the wastes they generate. These are questions that are ideally suited for IE research. AM is not inherently zero waste as some had hoped. It is true that using subtractive manufacturing techniques that begin with a block of material and remove some to produce the final shape generates scrap or waste that AM can often avoid. There are, however, the supports mentioned above and residual feedstock in the production process that are inherent elements of some types of AM. But the biggest waste-related impacts may revolve around whether consumers end up with more goods and thus an increase in end-of-life waste and in the associated emissions and resource consumption upstream in the supply chain. There is growing consensus that the biggest environmental benefits will come from the production of parts that are light weighted because of AM's capability to produce objects with complex geometries (Kellens et al. 2017; Faludi 2017). Think of specialized parts for aircraft that can reduce weight and thereby fuel consumption and greenhouse gas emissions (Mami et al. 2017). Put in IE lingo, a critical (and less touted) environmental opportunity arising from AM may be the reduction of use-phase impacts. The absence of a fixed environmental and financial expense for tooling may result in cost advantages (Atzeni and Salmi 2012) or savings of specific energy consumption (Telenko and Seepersad 2012) resulting from AM adoption where production quantities are small. In conjunction with sustainability improvements in the use phase, the life cycle view suggests some evidence that AM can be both cheaper and more environmentally benign than conventional manufacturing pathways, subject to a number of criteria being met, including manufacturability. Alas, even this generalization faces exceptions and complications, making it the starting point for environmental assessment, not the conclusion. Thus, comparing additive and subtractive manufacturing falls prey to a familiar verdict in IE research—it depends. Conventional manufacturing includes a vast range of types of technology, including machining, injection molding, and die casting. Similarly, AM includes diverse technologies: Selective laser sintering, selective laser melting, electron beam melting, fused deposition modeling, and stereolithography are among the most commonly applied AM technologies. As Baumers and colleagues (2017b) state in a companion introduction to this issue: “Each AM technology variant, essentially building on a different physical mechanism for the conversion of raw material inputs into outputs, carries its own set of characteristics, limitations and impacts, making the formulation of generalizable statements on the environmental dimensions of AM challenging.” Thus, an important implication of the complexity of assessing the environmental dimensions of 3D printing is that its adoption and diffusion won't automatically generate net environmental benefits. Like other technologies, environmental considerations need to be integrated into the design and deployment of 3D printing if it is to realize its full contribution to sustainability. Thank you to Martin Baumers (University of Nottingham) and Tim Gutowski (MIT) for their feedback on this article. Any errors are my own. Conflict of Interest Statement: The author has no conflict of interest to disclose.