First LCA on 3D Printer Sustainability: Green Manufacturing Revolution or Overrated Gadget?

Rapid prototyping, also called 3D printing, is the name of a much praised technological innovation touted as revolutionizing the well-established patterns of industrial manufacturing. It is a fascinating thought: each and every one of us will soon be capable of making sophisticated, customized products at home and no longer depend on a limited range of mass-produced industrial fabrications. But how real are our expectations? Does the collective euphoria for the new affect our capacity for a mindful, neutral evaluation of the potential behind low-budget 3D printing? And what are the hidden hick-ups concerning its overall sustainability?

By adding one layer to another and another and so forth, printing has entered the third dimension. It starts with digital data, like a CAD-file or a 3D scan of an existing object, typically takes a solid, thermoplastic “spaghetti” called filament instead of liquid ink, and produces objects, not images. That is captivating news indeed, and it has inspired many to formulate big hopes. The main advantage of a printed object, apart from its infinite variability, is material efficiency. Compared to the two other forms of making an object, either pouring melted material into a mold or cutting material out of a solid block of raw material, printing produces virtually no production scrap. It is an additive process, not a subtractive one, so 100% of the input ends up in the final product. Second, you dramatically reduce transport emissions by on-site production. The machine sits where the product is needed, at your house or in your office, not in a central manufacturing plant from which it has to be stored and transported to the final user through a mind-boggling, energy-intensive distribution network. What’s more, the days of overproduction would seem to be numbered: with 3D printing, you only produce as many pieces as you need.

Mara Grunbaum paraphrased these advantages well, at ecomagination. It is clear why rapid prototyping became so popular in professional manufacturing throughout the last decade:

On the industrial level, the technology, also called additive manufacturing, has three main environmental selling points: Because plastic or metal is laid down only where it’s needed, there’s very little scrap, unlike when objects are stamped or sculpted out of a larger piece of material. The same machine can build many different things, so you don’t have to create specialized machinery for each piece you want to make. And since the printers take direction from digital design files that are easy to transmit electronically, parts and products can — at least in theory — be printed out right where they’re needed, rather than shipped long distances from a factory where they’re mass-produced.

These sophisticated rapid prototypers can also melt and print metals and even food. However, the 3D printers that have become affordable for the home user in the last few years, the revolutionary ones, usually only process two kinds of raw material. Either fossil-based ABS thermoplastics (acrylonitrile butadiene styrene) or plant-derived polylactic acid (PLA). Because it is hard to imagine this three-dimensional ink, I mentioned the similarity of this filament to spaghetti earlier. However, in contrast to a stove top’s ability to boil semolina, you can’t expect a 3D printer to produce quick results. With a digital model that you want replicated in the real world, what you most need is patience: “The process, known as ‘additive manufacturing’, can take anywhere between several hours to several days”, wrote Catherine Wilson from edie.net in her blog post on 3D printing and sustainability.

Well, if it is capable of making any custom spare part, I’m happy to wait a few hours for my printer to complete its job. By doing so, it extends the lifespan of my existing products beyond any limit of the manufacturer, who may possibly decide to stop providing spare parts tomorrow. By eliminating the main reason behind obsolete products, 3D printers help to enter an era of sustainable products with extended phases of use in the product life cycle. So say the advocates. Moreover, as some thrilled supporters argue, the printers help to make more suitable – because more highly customized – products right away. And they will have longer lifetimes due to being exactly appropriate for the specific use. Considering this, we can conclude that 3D printers really should boost expectations for improved environmental sustainability in production systems. But other expectations are even higher. An anticipated benefit of 3D printing could easily be dubbed revolutionary when it comes to social sustainability: knowledge and the means of production no longer in the hands of a few multinational corporations in the Northern hemisphere, but rather democratically distributed among tens of thousands of globally equal users. As Joy Hughes from Solar Gardens put it:

3D printing has the potential to do for manufacturing what the PC did for computing and what the solar panel is doing for energy. The ability to make things is becoming a commodity, available to many at low cost, decentralized, with innovation democratized.

It sounds marvelous, doesn’t it? We found a technology that will save the world. Finally. Well, unfortunately, as with everything in the real world, there is a downside to 3D printing. First of all, even highly customized products will eventually break down. Given that the challenge of recycling has never been fully resolved, even with relatively homogeneous industrial manufacturing methods at the core of today’s waste, how are we supposed to deal with the leftovers of individual material mixtures and customized products at the end of their life cycle? Will the new, remarkably free users care for the principles of ecodesign, or will they shortsightedly produce only what best fits the needs of the use phase? Some raw materials utilized in sophisticated 3D printers such as metal powders pose health risks and can require even more energy than conventional manufacturing, as Mara Grunbaum wrote:

Mechanical engineer Tim Gutowski, who heads MIT’s Environmentally Benign Manufacturing group, found in a 2009 study that laser direct metal deposition — a type of additive manufacturing where metal powder is deposited and fused together by a high-energy beam — uses hundreds of times the electricity, per kilogram of metal processed, as more traditional methods like casting or machining.

Due to the different scale of a home-use 3D-printer, that builds one product once in a while, and an industrial machine, that constantly makes hundreds or thousands of products, the embodied energy of their products is totally different. Per item, the industrial machine’s impact is almost negligible, whereas it is not for the printer. On the other hand, while transport emissions for raw materials occur in both cases, the final product moves no further distance when made on-site with a 3D printer, which cuts the embodied product distribution energy by almost 100%. All this has to be taken into account when comparing conventional, centralized manufacturing with distributed 3D printing.

With affordable 3D-printers conquering all markets in Western countries, media did not wait long to report on possible misuse. In New Zealand, for instance, the replicators recently suffered bad publicity because of their reported capacity to produce handguns. So this is just the right moment to stop the gossip with the first life cycle assessments (LCAs) and, instead, to enrich the discussion at the other end of the scale for debate quality. By providing reliable data and an appropriate orientation to the framework necessary for 3D-printing with regard to its promise of sustainability, LCAs do what they do best. Megan Kreiger and Joshua Pearce from Michigan Technological University are among the first scientists to compare the environmental effects of a 3D-printed product with a conventional product throughout the products’ respective life cycles. They took a typical plastic juicer, made in China, and compared it to a home-manufactured one. The specific 3D printer used in the study is an open-source design named RepRap, which used a 15% fill composition only, saving a considerable share of material when compared to the 100% fill of conventional manufacturing. According to its wiki page, the RepRap is the current market leader, followed by the commercial Makerbot.

Kreiger and Pearce found that the 3D-printed juicer had a lower cumulative energy demand than their mass-produced counterpart, no matter if ABS or PLA were used. In terms of carbon emissions, however, results depended on two parameters: the electricity source and which material is used. When using the fossil-based, but more rugged ABS as raw material, 3D printing generated lower emissions only when the electricity to run the printer was solar-powered. With regular power from the carbon-intensive US-American grid, it was the conventional method of mass-manufacturing with ABS that resulted in lower emissions. However, with PLA, 3D-printing always had a better environmental performance than conventional mass-manufacturing, both using less energy and emitting less carbon. The juicer that was made with a PLA-fitted, solar-powered 3D-printer was far better than its conventional equivalent. It used roughly half the energy and only caused a third of the greenhouse gas emissions.

The technology may indeed have become more affordable in recent years and studies like Krieger’s and Pearce’s show that 3D printing can already reduce the burden on the environment. However, they also emphasized how vast is the space for future efficiency improvement and energy savings, e.g. in the losses related to an open heat plate:

The emissions are lower for the distributed manufacturing systems for all cases except the ABS juicer without PV [solar photovoltaics]. This is due to the relatively large amount of energy needed to keep the heated build platform at operating temperature for the ABS. Future work is necessary to reduce the energy needed for the build platform. This can be done by using chemical means to enable better adhesion, using zoned heating so only the part of the bed that is needed for the part is heated, better insulating the bed, or using a controlled environmental chamber to insulate the entire RepRap from cold ambient temperatures. […] If more products are printed simultaneously on the heating bed, it may be possible to reduce the energy to print even further due to the initial heating energy being dispersed among more individual products.

So the conclusion of a neutral assessment of 3D-printing is not that surprising. If we are into sustainable manufacturing, we learn that we should use biodegradable material, renewable energy, and improve our heat flows. And for simple things like plastic juicers, we can indeed consider 3D printers! I’m looking forward to seeing when the above-mentioned improvements are going to enter the 3D printing sphere. In the meantime, although I regret smashing an excellent idea such as wide-spread 3D printing on the hard floor of reality in the year 2013, I’ll let Mara Grunbaum and Bert Bras have the last word. I.e., there is one inevitable behavioral issue that most people overlook:

And the dream of Star Trek-style replicators in every home, printing everything from toys to toasters? That may not be the best idea either, according to Bras [Bert Bras, mechanical engineer at Georgia Tech who focuses on sustainable design and manufacturing]. As an analog, he says, think of the home photo printer. Sure, you save a bit of gas not driving to the drug store to get your glossy prints. But you also waste a lot of ink and paper when your printer glitches or your photos come out poorly and you start over, which is less likely to happen with a trained professional and a machine built to run off a thousand prints a day. And that’s not to mention the impact of manufacturing all those individual printers and ink cartridges in the first place. “It’s a lot more efficient if a big machine does it,” Bras says. By the same token, while 3D printing has its uses in industry, “you have to be careful when you hand it out to amateurs.”