A team of researchers have outlined their vision of a sustainable and circular additive manufacturing ecosystem.
Published in the journal Nature Sustainability, the article is titled ‘A vision for sustainable additive manufacturing.’ It proposes that 3D printing can support a more eco-friendly manufacturing process if developed through a “system-level approach.”
This would mean integrating sustainability at all stages of the additive manufacturing process chain, including 3D printer design, process development of raw materials, supply chain selection and end-of-life recycling and reusability.
They suggest that sustainability-optimized designs should be integrated into existing design for additive manufacturing (DfAM) principles and that the industry must be guided by global sustainability initiatives. These include United Nations’ Sustainable Development Goals and the European Green Deal.
Looking to the future, they set out the importance of “a new role for AM” that is based on environmentally sustainable practices. While additive manufacturing is “not inherently circular or sustainable,” they argue that it has a key role to play in the creation of a circular economy.
Is 3D printing sustainable?
Hailing from universities in Italy, the Netherlands, Singapore, Switzerland, Sweden, and the US, the researchers outline that global climate change, biodiversity loss, and political turmoil are threatening the availability of raw materials.
A common argument in favor of 3D printing is that it eliminates material waste. However, the researchers note that the reality is not black and white, stating that “extensive waste material reduction seldom occurs.”
The research shows that while additive manufacturing can sometimes reduce the amount of wasted material, this is strongly dependent on the context of the 3D printing technology and application.
3D printing processes are highlighted as less materially efficient than conventional manufacturing processes such as injection molding, casting and extrusion. For instance, polymer powder bed fusion (PBF) can produce up to 44% of plastic powder waste. Additionally, photopolymer resin-based printers produce liquid resin waste, while 3D printed support structures are frequently discarded.
The paper also outlines the negative environmental impact of 3D printer energy use. The energy consumption of most polymer 3D printers reportedly exceeds the total impact of injection molding ABS plastic. Similarly, for most metal parts, additive manufacturing uses more energy per kilogram of material processed than casting, molding, forging or extrusion.
The researchers also dispute the notion that additive manufacturing eliminates transportation emissions. They explain that raw materials used in 3D printing still need to be shipped globally, with additive manufacturing only reducing the need to “transport different parts made of the same materials.”
How can these 3D printing misconceptions be overcome? The authors believe the answer lies in more comprehensive and context-based life-cycle analyses (LCA). Future analysis should clarify where 3D printing is not sustainable. Excluding material production and end-of-life impacts could lead to missed opportunities for developing new sustainable 3D printing materials and processes.
How to make 3D printing more sustainable
Next, the authors outlined how additive manufacturing can be made more sustainable, arguing that 3D printing processes, machines and materials need to be “redesigned.”
One suggestion is replacing the melting of plastics in direct ink writing (DIW) 3D printing with bio-composite pastes. Such parts could use five times the material and five times the wall thickness of DIW components while having half the environmental impact. However, the researchers note that the mechanical properties of these pastes need to be improved before this vision can be fully realized.
They also indicate the need for better end-of-life recyclability of 3D printing materials. Currently, multi-material 3D printers render recyclable polymers non-recyclable because they cannot be separated from each other and accumulate impurities. Therefore, the authors believe the ingredients in such materials should be compostable, allowing them to be discarded in an eco-friendly manner.
The next step to improving the sustainability of additive manufacturing is leveraging sustainable design tools. The authors suggest incorporating sustainability features into existing DfAM workflows. For instance, LCAs could be integrated into optimization software to guide material choice, process parameters, and geometry.
3D printing’s sustainability potential
The authors also expanded on how additive manufacturing can be used to make existing design practices more sustainable.
They argue that all products should be designed to be easily repaired and maintained. When spare parts are not cost-effective to mass-produce and store for years, additive manufacturing can produce replacement parts on demand and at the point of need.
Design for upgradability is also suggested. Manufacturers should focus on updating existing products to meet changing customer needs by adding new features and functionalities. This would extend product life and reduce waste. However, they acknowledged that more exploration is needed to ensure the profitability of this business model.
The reusability of parts at the end of their life cycle is noted as another design consideration. This method seeks to give parts a second life by making them easy to disassemble and reassemble into new offerings. The authors believe that additive manufacturing is well suited to this application, but highlight the need for new guidelines, decision support and smart systems to achieve this.
Lastly, they note that products should be designed to be recycled. This often results in downcycling, where the raw material loses its original quality. Additive manufacturing is already used to process materials that include varying amounts of recycled content. Yet, more research is needed to determine how best to treat recycled feedstocks, as impurities often lead to failed prints.
The future of sustainable additive manufacturing
The article envisions a future additive manufacturing life cycle that is adaptable, digitally driven and sustainable.
To achieve this, it states that 3D printer utilization needs to be maximized, meaning fewer 3D printers working 24/7. This is because some 3D printer technologies can reduce the impacts per part by 10x or even 100x. A new generation of technologies and materials also needs to be exploited, along with the design processes that consider the sustainability benefits of additive manufacturing.
The researchers ultimately argue that their vision for sustainable additive manufacturing can only be achieved if key stakeholders share the same intents and commitments to meet sustainability targets.
While early proclamations may have hailed 3D printing as a green technology, it is now more important than ever to critically evaluate its sustainability claims and provide a balanced assessment of its environmental impact.
The danger of sustainability becoming a “bandwagon” was highlighted by Dr. Phil Reeves during a presentation entitled Sustainability and 3D printing: Greenwash, Hogwash or a Justified Shift in Thinking? In addition to useful figures on the energy consumption of various additive manufacturing technologies, Reeves’ presentation provided insights into the embedded carbon in metal AM powders. Previously, consultant firm Roland Berger issued a report tackling similar issues and warning against “superficial” or “misleading” sustainability claims of 3D printing.
However, in many cases, the additive manufacturing advantage, at least in energy terms, stems from how the final component is used. Energy assessment over the life of an AM aerospace component, whereby weight reduction reduces fuel consumption, will often lead to a significant reduction in emissions versus a conventional part. The same may not be accurate for components used in other sectors. The work done to understand the savings can be found in the Life Cycle Assessments now conducted by companies, trade organization AMGTA, and increasingly academic researchers.
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Featured image shows the researchers’ vision for sustainable additive manufacturing. Image via Jeremy Faludi.
