How Green Is 3D Printing?
Michael Molitch-Hou posted on September 28, 2016 | explores the various methods by which 3D printing could be used ecologically and sus...

As a comparatively new technology that has not yet been fully integrated into the larger manufacturing supply chain, 3D printing represents an opportunity to do things differently. Whereas the industrial revolution of yesteryear established a business as usual plagued with smoke stacks, poisoned water supplies, floating garbage islands and deadly labor practices, advanced manufacturing, including 3D printing, could bring about the implementation of ethical employment, closed-loop production and eco-friendly materials.

If 3D printing is to contribute to the urgent and necessary eco-industrial revolution of the 21st century, we must take stock of both the pitfalls and benefits of the technology as it relates to sustainable production. How can 3D printing aid in efforts to manufacture and deliver products in ways that reduce the negative human impact on the Earth's ecosystem? What obstacles does the technology face in order to bring about such positive change?

Additive vs Subtractive Manufacturing

The additive nature of 3D printing means that building parts layer by layer can generate less wasted material than other subtractive forms of fabrication, such as CNC milling. Whereas a CNC machine might cut a part out of a solid steel block, additive processes waste only the material that may not be recycled for further builds.
CFM International’s 3D-printed fuel nozzle reduces part count from 18 to just one. (Image courtesy of GE.)
CFM International’s 3D-printed fuel nozzle reduces part count from 18 to just one. (Image courtesy of GE.)

Moreover, 3D printing allows for the creation of geometrically complex designs not previously possible with traditional techniques. GE Aviation and Safran Aircraft Engines demonstrated this through their joint company, CFM International, which 3D printed the highly publicized LEAP jet engine fuel nozzle. With the LEAP nozzle, CFM was able to reduce the part count on the assembly from 18 parts to just one. The resulting design brought new efficiency to aircraft engines, cutting fuel consumption and CO2 emissions by 15 percent.

When asked whether or not 3D printing is more ecologically friendly compared to traditional manufacturing processes, leading industry analyst Terry Wohlers explained, “The short and simple answer is ‘maybe,’ but the jury is still out. Some forms of additive manufacturing (AM) technology can produce considerable waste, such as the support material used in the process and laser sintering powder that cannot be reused. A much higher percentage of metal powder [than polymer powder] can be reused, so it is more environmentally friendly. When considering the design of lightweight structures, especially for aircraft and eventually automobiles, the environmental benefit is greater with the savings in fuel, coupled with savings in using less material.”

This point was demonstrated in 2014 by direct metal laser sintering (DMLS) 3D printer manufacturer EOS when it performed a study with Airbus regarding the environmental lifecycle benefits of DMLS as compared to rapid investment casting. To compare the two technologies, a generic titanium aerospace bracket was both 3D printed via DMLS and produced with traditional casting as a control in the study. Then, the bracket was redesigned to take advantage of the geometric complexity offered by 3D printing.

The lifecycle of the brackets was then analyzed with a number of different factors in mind, including energy consumption and COemissions from the actual process of producing the bracket itself to energy used and CO2 emitted by planes featuring the brackets. Ultimately, the study's authors determined that optimizing the design of the bracket for 3D printing resulted in a 40 percent reduction in CO2 emissions over the lifecycle of the bracket and reduced the weight of the plane by 10 kilograms.

On the left, a conventional bracket design. On the right, a bracket optimized for 3D printing. (Image courtesy of Airbus Group Innovations.)
On the left, a conventional bracket design. On the right, a bracket optimized for 3D printing. (Image courtesy of Airbus Group Innovations.)

Material waste was also 25 percent less with 3D printing over casting. The study suggests that, while energy consumption is similar for both processes, casting actually produces much more CO2 directly due to the fact a ceramic mold is burned out in a high-temperature furnace.

“[T]he final product was more fuel efficient during its use,” a representative from EOS explained in an email to “CO2 emissions were reduced by 40 percent due to weight savings of up to 10 kilograms and optimized geometry. These reductions greatly affected the ‘buy-to-fly’ ratios.”

The representative added, “As a whole, manufacturing has historically been subtractive—a process that generates significant amounts of discarded material and waste. So there is still progress to be made in continuing to bring AM mainstream. Within the realm of AM, we can continue to make strides in decreasing the energy consumption of AM machines. DMLS requires a tremendous amount of energy, but with each new system, we’re constantly streamlining them to be more efficient throughout the AM process.”

3D printing only produced slightly less indirect CO2 emissions, due to slightly lower energy usage. This, however, is a problem associated with the global energy grid and not the efficiency of the technology. According to the U.S. Energy Information Administration, in 2012, 40 percent of the world's electricity was generated from coal, 22 percent from natural gas and 22 percent from renewable energy sources. In the United States in 2015, the nation's energy grid was divided by a dependence on coal (33 percent), natural gas (33 percent), nuclear power (20 percent) and a variety of sustainable sources such as water, solar and wind. As has been well documented, both coal and natural gas are large producers of global greenhouse gasses (GHGs). And any nation that relies heavily on these sources to power its electric grid will contribute greatly to climate change. Therefore, any manufacturing equipment, additive or otherwise, will most likely rely on fossil fuels for energy.

Distributed Manufacturing

According to a 2015 EU study, aviation and maritime shipping are responsible for 3 to 4 percent of GHG emissions. While this may be a small slice of the GHG pie, if left unchecked, this sector could account for 17 percent of GHG emissions by 2050.

Moreover, when other forms of freight transportation are accounted for, the number increases. A 2007 report published by the Air and Waste Management Association has freight transportation, including heavy-duty truck, rail and water transport, responsible for over 25 percent of COemissions in the United States and 30 percent in Europe. These numbers don't include the other toxic by-products of the global shipping industry, such as high-sulfur fuels used by ships that acidify oceans.

The advent of 3D printing, however, makes possible the concept of distributed manufacturing. Our current manufacturing model consists of a fragmented supply chain composed of centralized manufacturing facilities. If 3D printing becomes a viable means for producing the majority of end parts, it may be possible to 3D print goods locally and on demand, a model known as distributed manufacturing.

Currently, few businesses are focusing on such a model, leaving the 3D printing network 3D Hubs as a leader in this space. 3D Hubs hosts over 25,000 3D printers on its site, including a growing number of industrial service providers, making it possible for people across six continents to order 3D prints directly from local 3D printer owners.

In turn, shipping is reduced from transit across oceans and countries to across county lines. This makes it possible to reduce the carbon footprint of the freight industry, but also gives customers an opportunity to meet local manufacturers and learn about the 3D printing process.

Bram de Zwart, cofounder and CEO of 3D Hubs, discussed how the company is enabling the implementation of a distributed manufacturing process. “Digital manufacturing machines such as 3D printers are becoming the factories of the future,” de Zwart said. “They enable consumer products to be made on demand and much closer to their point of purchase, eliminating waste from overproduction and transportation. 3D Hubs is accelerating this future by giving everyone direct local access to 3D printers.”

At the moment, 3D Hubs features a number of different 3D printing technologies to make this possible, including industrial plastic and metal 3D printers, as well as more affordable desktop machines. However, as the Industrial Internet of Things begins to take shape and manufacturing technologies drop in cost and see an increase in accessibility, it’s possible to imagine even more fabrication systems connected on such a network.

For instance, producers of a desktop water-jetting system are seeking funding to develop their products, and numerous low-cost laser-cutting and CNC milling systems exist to bring about an affordable manufacturing revolution. Once all of these machines are networked through a site like 3D Hubs, an even larger number of products could be produced via distributed manufacturing models.

Closed-Loop Production

As it stands, human beings produce about 2.6 trillion pounds of garbage per year, according to a study conducted by the World Bank in 2012. About 46 percent of that waste is produced by high-income countries, like the United States and England, and about 59 percent of that waste ends up in landfills.

The report also noted that post-consumer waste is responsible for about 5 percent of global greenhouse gas emissions, meaning that, in addition to leaching toxins into our soil and drinking water, this trash is polluting our air.

While consumers can be held partly responsible for generating waste, government agencies and manufacturers can also be held to blame, as producers continue to fabricate products that are not recyclable or biodegradable and governments may not incentivize them to do so.

Additionally, some public recycling programs may not adequately handle the waste provided to them by consumers. For instance, the United States only uses seven different codes for categorizing plastics, lumping multiple types within the same groups, while China has 140 codes, providing extensive categorization for various polymers.

This is even more problematic when it comes to plastic for 3D printing. Whereas the first two plastics covered by recycling codes in the United States account for common consumer products like water bottles and milk jugs, the most prevalent plastics used in 3D printing via fused filament fabrication (FFF) are categorized as “other.” This catch-all group includes the biodegradable polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS), the plastic that often comprises car dashboards and LEGO blocks.

A PLA symbol for inscribing into 3D-printed objects to open up greater recyclability in 3D printing. (Image courtesy of Resources, Conservation and Recycling.)
A PLA symbol for inscribing into 3D-printed objects to open up greater recyclability in 3D printing. (Image courtesy of Resources, Conservation and Recycling.)

For this reason, associate professor Joshua Pearce's Open Sustainability Technology group at Michigan Technological University proposed a more extensive categorization system that allows 3D printer users to embed their own recycling codes onto 3D-printed parts. Parts made from ABS, for instance, might have an ABS recycling logo on them so that they can be recycled and reused to manufacture other ABS products.

This will be a key component to a distributed manufacturing ecosystem, as 3D printer owners will be able to recycle previously printed goods based on these codes. To make this possible, Pearce's group also developed the RecycleBot, a device capable of converting plastic waste into 3D-printable filament.
The recycling process for converting plastic milk jugs into 3D-printable filament. (Image courtesy of Michigan Tech’s Open Sustainability Technology lab.)
The recycling process for converting plastic milk jugs into 3D-printable filament. (Image courtesy of Michigan Tech’s Open Sustainability Technology lab.)

Research continues on the RecycleBot to further drive down the cost to build the machine and expand the range of materials it can use, such as polyethylene terephthalate (PET), which Pearce says is the “most wasted plastic.” The Open Sustainability Technology group will also be releasing a new set of vertical RecycleBot electronics this semester that will be available in an AC version for people with reliable electricity and a DC version that can be solar powered—which will complement the group’s solar-powered RepRap 3D printer.

Pearce takes the distributed manufacturing model implemented by 3D Hubs a step further, envisioning consumers as becoming prosumers who 3D print their own goods and recycle those goods into reusable 3D printer filament when necessary. He explained, “By combining the RecycleBot with 3D printing, people can turn their trash into valuable resources. We previously proved in a lifecycle analysis that this distributed recycling is better for the environment than even conventional recycling.”

Pearce added, “I see us moving more towards a form of truly distributed manufacturing, where individuals fabricate custom products for themselves from free and open-source digital plans. Economics is clearly in favor of such a transition. The number of [free, open-source hardware] designs continues to climb, and the class of open-source 3D printers continues to gain in sophistication, ease of use and materials selection.”

Obstacles to Distributed Manufacturing

In order for such a model to emerge, however, Pearce said that it is necessary to cultivate a thriving open-source design community and a “stable, well-respected, high-quality repository” for 3D-printable designs.

“A few years ago, that would have been MakerBot's Thingiverse,” Pearce continued. “Unfortunately, the MakerBot implosion—in which the darling company of the open-source hardware world went proprietary and literally went backwards on quality and documentation—set the entire community back years. The company alienated a large swath of the maker community with the change of its license agreement, which went pretty far out of both the letter and the spirit of the maker community.”

Since then, 3D-printable models have no centralized location, according to Pearce, making it more difficult for a true community to emerge around quality designs and innovation.

Low-cost, open-source 3D printing technology needs to improve as well. While companies like Aleph Objects have introduced important features like automatic bed leveling and calibration into open-source 3D printers, Pearce argued that “we still need to go far further, particularly with respect to multimaterials, composites and advanced materials like metals.”

In that regard, Pearce's group has also developed a metal 3D printer capable of being built with off-the-shelf components for under $2,000. The machine uses a metal arc welder to heat up spools of metal onto an aluminum substrate. In a closed-loop system of manufacturing, the metal feedstock could come from recycled aluminum cans.

Before consumers can become prosumers, however, Pearce believes that a cultural change may need to take place. “Many people have no idea how things are made, how they work or how to take care of their own things,” he said. “They have been brain-washed into buying a new one from companies with questionable labor practices and throwing away the old thing in a landfill. Besides being wasteful, ethically tenuous and horrible for the environment, this is lame. Buying something makes you a consumer, which justifiably used to be an insult.”

He added, “As a global community, we need to foster more curiosity, creativity, sharing and a sense of exploration so we can transition back to making the products that surround us as makers. Only this time around, rather than doing everything with simple industrial tools, we can use the technologies of today like 3D printing. This will allow us to live rich, full and relatively equitable lives, while minimizing our impact on the environment.”

Fair Trade Filament

As 3D printing becomes more popular, Pearce suggested that, not only will new recycling codes be required, but so too will an “ethical product standard” in which material recyclers provide 3D printer filament to others. “Similar to the solutions proposed for other forms of ethical manufacturing, it is possible to consider a form of ethical 3D printer filament distribution being developed,” Pearce said. “There is a market opportunity for producing this ethical 3D printer filament, and we helped develop an ‘ethical product standard’ for 3D filament based upon a combination of existing fair trade standards and technical and lifecycle analysis of recycled filament production and 3D printing manufacturing.”

Some organizations and businesses have already formed around such a concept. Protoprint in India, for instance, has trained local “waste pickers” to convert plastic bottles into high-density polyethylene (HDPE) 3D printer filament. Traditionally, individuals that sort through trash for recyclable materials will turn them in at a scrap or recycling center for less than $2 per day. Protoprint, however, is training waste pickers to operate the machinery required to recycle the material themselves.

Once trained, those that operate the filament production centers can sell the 3D printing material themselves as Protoprint goes on to train another group. This model gives the waste pickers marketable skills as well as their own filament business. Protoprint is still experiencing issues with the quality of the 3D printing material at the moment, seeing significant warping of the HDPE when printing, but the organization continues to work on it.

Protoprint CEO Sidhant Pai explained, “We've made a lot of progress since we launched our pilot filament production site in 2014 but have yet to completely solve the filament warping issue. We've received a grant to fund research with National Chemical Laboratories over the next two years to develop an additive to prevent the warping and improve filament quality.”

Eco-Friendly Filament

Though it's possible for owners of FFF 3D printers to make their own feedstock with the RecycleBot or commercially available alternatives, such as the Filabot, the technology may not quite be ready for more novice users. Alternatively, some 3D printer owners may simply lack the time for extruding their own filament.

Fortunately, there are a number of businesses doing the work for us. Refil, Innofil3D, 3DomFuel and others all manufacture filaments made from waste products. These include ABS from recycled car dashboards, PET from beverage bottles and high impact polystyrene (HIPS) from old refrigerators. An upcycling company called TerraCycle, in partnership with 3D Brooklyn, has even made filament from recycled potato chip bags and has a number of other 3D printing projects in the works.

3DomFuel, in particular, has produced a number of feedstocks that really go the extra mile to reuse waste. In addition to biodegradable PLA made using NatureWorks corn starch–based plastic, the company manufactures filaments composed of leftover coffee grinds, as well as by-products from the beer and hemp production process.

3DomFuel Chief Marketing Officer John Schneider spoke to the benefits of using eco-friendly materials in developing the company's 3D-Fuel filaments: “3D-Fuel uses genuine NatureWorks Ingeo 3D printing resins as the core ingredient for many of our materials. One of the benefits of this is that we are able to get a better sense of the environmental impact [via a Life Cycle Assessment].”

“Another way we stay sustainable is by using eco-waste in many of our filaments,” he added. “Whether that’s waste from coffee, beer, hemp or the others we have in development, we are able to incorporate them into 3D printing filaments to give them new life. There are very few materials that we produce that are not bio based. Our Biome3D filament, for example, has many attributes of ABS but is 100 percent bio based. Our spools are made from recycled HIPS. Though they are a petroleum-based material, HIPS is a very recyclable plastic.”

Matthew Stegall, 3DomFuel CEO, explained that much of what the company aims to do is reduce the impact that 3D printing plastic might have on the world’s landfills. Though PLA may be biodegradable, Stegall pointed out that, in a traditional landfill, it still takes decades to biodegrade. When disposed of in an industrial waste system, however, it takes closer to three to six months.

By combining natural waste materials, such as coffee grounds or hemp, into PLA, not only does the company reuse by-products that would otherwise be discarded, it increases the biodegradability of the plastic that is used in the 3D printing industry.

Huffing Plastics and Metals

These sorts of materials may be better for the land, air and water, but some may be potentially dangerous to the 3D printer users themselves. Several studies have already been conducted demonstrating that desktop 3D printers produce ultra-fine particles (UFPs) and volatile organic compounds that, when inhaled, can cause lung irritation or, at their worst, heart and lung disease.

ABS has been shown to be the most toxic in these cases, in that it produces UFPs 345 times higher than what exists in a baseline environment and gives off by-products via outgassing processes: by-products such as ethylbenzene, isovaleraldehyde and acetaldehyde, all of which have a range of negative health effects when inhaled. PLA is much safer in terms of the toxic effects of the materials, but breathing in UFPs can still cause irritation.

For this reason, desktop 3D printer manufacturers may wish to take safety precautions by featuring HEPA or other filters in their machines. This is particularly important as hobbyist printers are often targeted at classrooms for their ease of use and low cost.

It’s important to note that industrial systems, too, can be dangerous to use, given the fine metal powders and flammable environments involved with metal 3D printing. Most facilities that operate these machines will likely take the necessary precautions, such as requiring that machine operators wear ventilators and gloves, but, if not, UL offers training and safety certification for industrial 3D printing facilities.

Changing Minds and Materials

Many of the aforementioned eco-friendly developments will naturally continue to develop; however, the currently unsustainable practices already implemented in the larger worldwide economic system will also continue to develop. For instance, a number of large petrochemical companies have recently joined the 3D printing industry with their own thermoplastic materials.

Among them are chemical giants like DuPont, which has partnered with taulman3D to manufacture T-Lyne filament and Covestro, a subsidiary of Bayer, that is producing polycarbonate with Polymaker. These are just a couple of the companies becoming involved in the space, but in addition to being involved in numerous environmental controversies (denying climate change, dumping toxic waste into bodies of water and air pollution, for example), these materials are made of the same plastics that are derived from petroleum and that result in heaps of plastic waste.

To understand what will be required to shift our plastic economy in a more sustainable direction, I asked Terry Wohlers. He explained, “The motivation will largely come from the economic benefits. In other words, if more sustainable materials result in less expensive products, customers of the materials will create demand and suppliers will follow. If these materials are more expensive and their performance is inferior, they will struggle to gain traction.”

Another possibility is that change could come from the bottom-up. While economics are often the deciding factor for large corporations, they may be increasingly susceptible to public perception and pressure.

A relevant example is a campaign launched by Greenpeace against Kimberly-Clark, makers of Kleenex, Kotex and other paper-based consumer products. After the environmentalist organization spent five years campaigning against the multinational corporation for its destruction of old-growth forests to create throwaway goods, Kimberly-Clark finally succumbed to the pressure. The corporation went from using 54 percent to 84 percent of recycled fibers in its products.

Not only did Kimberly-Clark admit that Greenpeace's efforts played an important role in this move, but the corporation continues to collaborate with Greenpeace to this day. Moreover, Greenpeace claims that other similar manufacturers followed suit, such as Procter & Gamble.

More recently, Greenpeace's efforts to prevent Shell from drilling for oil in the arctic have paid off. The activist group created public awareness around the potential effects of oil spills and climate change associated with arctic drilling and also formed barricades with kayaks to prevent Shell’s oil drill rig from leaving the port in Seattle. After spending over $7 billion to find oil reserves in the Alaskan Arctic, the oil giant decided to cancel the drilling project.

In an age in which information is increasingly available to the public through the Internet, such sunk costs might be avoided if corporations direct their operations with the public interest in mind. When they don’t, there may be more protest and, ultimately, fewer profits, as conscientious consumers avoid ecologically damaging products in favor of those that are better for the environment.

The Future of Sustainability and 3D Printing

While it’s impossible to determine the future of the wildly incomprehensible human endeavor, through collective will, it may be possible to drive the species towards a more sustainable future via 3D printing and other technologies.

Divergent 3D has begun using 3D printing to overhaul the auto manufacturing industry in order to lessen the carbon footprint of one of the world's largest industries. The company's CEO, Kevin Czinger, argued that the GHG emissions from manufacturing automobiles actually far outweighs the tailpipe exhaust produced by individual drivers. In fact, the process of producing electric motors for vehicles puts out significant GHG emissions.

A chart depicting the amount of emissions associated with manufacturing and operating vehicles, including those from Divergent 3D on the far right. (Image courtesy of Divergent 3D.)
A chart depicting the amount of emissions associated with manufacturing and operating vehicles, including those from Divergent 3D on the far right. (Image courtesy of Divergent 3D.)

Rather than rely on massive metal-stamping facilities to produce a car chassis, Divergent 3D creates auto bodies using a series of 3D-printed metal nodes that connect carbon fiber rods, resulting in a lighter and more energy-efficient structure. Whether or not those cars rely on gas or electric drivetrains, they will ultimately be lighter, and the process of manufacturing them is much less toxic to the environment.

Divergent 3D is in the process of researching and scaling up its technology with the PSA Group, owners of Peugeot, Citroën and DS Automobiles. Whether or not Divergent 3D’s new manufacturing paradigm will take hold or make the environmental impact Czinger hopes it will remains to be seen.

However, what the company does demonstrate is the sort of out-of-the-box thinking that will be required if the species seeks to maintain a comfortable existence on this planet. Because 3D printing is a comparatively new technology with new implications for how goods are manufactured, there are new opportunities for material sourcing, delivery and design. With sustainable materials, local and on-demand production, efficient geometries and completely unique business models, the third industrial revolution brought about by 3D printing could be the first green revolution as well.

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