Someday soon, home may be where the recycling happens. If Dr. Joshua Pearce has his way, that is. Pearce has spent his career investigating how technology can address the pressing global issues of sustainability and poverty. Last year, he and his team from Michigan Technological University's Open Sustainability Technology research group put milk jugs through an office shredder, then into a 3D printer. They found that making their own 3D printing feedstock used about one-tenth the energy needed to acquire commercial filament, and used less energy than recycling the plastic conventionally.
Photo by Creative Tools, on Flickr
3D printing in general has been hailed as an eco-solution that will revolutionize industry as we know it. The technique boasts a wide range of potential applications in manufacturing, medicine, and even building construction. Since world demand for 3D printers and printing materials is projected to reach 5 million dollars per year by 2017, it may make a significant mark on the economy in the coming years. Environmentalists are hopeful because 3D printing offers several advantages over traditional manufacturing. It’s decidedly much faster and less wasteful. Since items are created digitally, there are no limitations on geometry; printers can make intricate shapes, interspersing hollow regions to make lighter-weight products that require less fuel to transport. The technique has already made lighter and cheaper solar panels that are up to 20 percent more efficient than conventional ones.
The eco-virtues of 3D printing have been extolled across the blogosphere. But is all the hype true? And what are its potential environmental drawbacks?
3D printing builds an item in layers from the bottom up, based on horizontal cross sections of a digital 3D model. It’s also referred to as additive manufacturing, since it builds products by adding material, rather than cutting it away. A major advantage is that it adds material to each layer only where it’s needed, resulting in little waste. In contrast, traditional subtractive manufacturing transports large amounts of material to a manufacturing site, where most of it’s cut away to shape an end product.
The Department of Energy’s Oak Ridge National Laboratory found that subtractive manufacturing can waste up to 30 pounds of material for every pound of useful material. With additive manufacturing, up to 98 percent of the material is used in finished parts. The process may also trim the number of steps required, further reducing energy consumption up to 50 percent for some industries.
While 3D printing machines may use different techniques to print with metal, ceramics, paper, and other materials, most desktop 3D printers print with plastic. Several desktop models are available for less than 500 dollars. While it may sound like something out of Star Trek, we can already download designs, customize shapes, sizes, and colors, and print personalized products at home within a few hours. Hundreds of designs for jewelry, home décor, iPhone cases, watches, and even musical instruments are available.
This new paradigm could change the meaning of “going local.” With consumers printing at home, emissions from transporting finished products could fall. Future printing with locally recycled feedstock could substantially reduce emissions from shipping raw materials as well. This create-on-demand model is also much more efficient than mass-producing and shipping potentially unwanted, excess items, and could eventually cut down on the need for product packaging.
Some people fear that the distributed manufacturing model of home 3D printing will perpetuate an unhealthy reliance on plastics. But this paradigm, along with the technology’s newness, allows for a good deal of experimentation with alternative patterns of plastic consumption, including distributed recycling.
For example, Pearce has shared his milk jug recycling process at Thingiverse, an open source hub for 3D printing designs. A number of innovators have invented similar machines that give used plastic new life as 3D printing filament, dubbed RecycleBots. Several models, such as the Filabot, are in the early stages of commercialization. A major advantage of using RecycleBots is that the plastic used for 3D printing is essentially recycled in the home, rather than transported to a centralized recycling center. It’s also much cheaper than buying commercial filament.
Still, the current generation of wiry, rough-edged RecycleBots look more like something you'd see in Dr. Frankenstein's lab than in the average home. While future models may gain more traction, existing models will likely only be used in the garages, work sheds, and basements of enthusiastic hobbyists.
Those who don’t have access to RecycleBot models still have the option to use recycled commercial filament with models like the Ekocycle Cube 3D printer. Newly released in December 2014, Ekocycle filament cartridges are made from 25 percent post-consumer plastic, and contain an average of three recycled 20-ounce PET plastic soda bottles per cartridge. 3D Systems, which created the Ekocycle model, encourages customers to send any unwanted 3D printed parts to one of four locations in New York, California, South Carolina, or Germany for composting or recycling into new filament.
The transportation emissions associated with 3D Systems’ highly centralized recycling operations are a significant drawback. However, if distributed recycling takes off, demand for locally recycled plastic filament could change the game. Anticipating a growing recycling industry, Dr. Pearce’s team has even proposed fair trade standards for plastic refuse, similar to those for fair trade coffee.
Printing with bioplastics is another alternative that’s already taking shape. Ekocycle owners can also choose compostable, biodegradable polylactic acid filament made with plant starch (usually from corn). And the 3D Print Canal House project in Amsterdam aims to 3D print an entire building with Macromelt made of 80 percent vegetable oil. However, biofuels still come with their own set of environmental and economic challenges.
Clearing the Air about Home Printing
Can melting plastic in your home affect your health? A 2013 study by Illinois Institute of Technology (IIT) found particle pollution associated with 3D printing to be equivalent to stovetop cooking, burning scented candles, or burning a cigarette. Particle pollution poses risks to the airways and circulatory system, potentially leading to breathing problems, heart attack, and stroke. But the amount of pollution depends on the type of plastic used. Most commercially available 3D printers use either acrylonitrile butadiene styrene (ABS) or bio-based PLA. The IIT study found that the ABS printers resulted in much higher emissions of ultrafine particles (less than 100 nanometers in diameter) than PLA printers. Also, while fumes from heated ABS plastic are associated with toxicity in lab animals, the chemistry of corn-based PLA doesn’t pose toxicity hazards.
While current models of 3D printers generally don’t come with air filters or exhaust mechanisms, future models could be fit with nanoparticle filters. For now, printing enthusiasts can take precautions such as ventilating the room and using an air filter while printing.
More Energy for Metals?
A pivotal environmental question about any new technology is how much energy it uses. Although home printing is energy efficient — desktop printers draw about as much power as a laptop computer — concerns have been raised about the amount of energy needed for the direct metal laser-sintering (DMLS) method of 3D printing industrial parts, which fuses metal granules together with lasers. Back in 2009, researchers at MIT found the method used hundreds of times the electricity of traditional methods. However, the study only looked at the production stage without taking into account overall life cycle, including waste reduction and reduced transportation emissions for lighter products.
A more recent study conducted in 2013 by EOS and EADS' Innovation Works (now Airbus Group), both private companies, compared the manufacture of airplane hinge brackets via DMLS and traditional casting. It evaluated both processes in terms of carbon dioxide emissions, energy consumption, raw material efficiency, and recycling.
While the DMLS bracket did require more energy in the production phase, other advantages made up for it. The DMLS brackets weighed less, since they could be printed in lighter titanium instead of steel. The additive process also reduced waste by up to 75 percent. Most importantly, the geometric complexity made possible by 3D printing allowed for easy optimization of the part’s design. The lighter, optimized brackets can safely reduce an aircraft’s weight by 10 kilograms. Despite using more energy in the production phase, the brackets can cut emissions by 40 percent over their entire life cycle, including the use phase.
3D printing is a complex technology that can use a variety of different materials to make a wide range of products. The fact that it is still a relatively new technology means that there is still room for experimentation and improvement, and with continued development, 3D printing may hold real promise for improved sustainability.