Glass bottles tossed in the trash are finding new life thanks to a collaboration between the Department of Energy's Oak Ridge National Laboratory (ORNL) and Vitriform3D , an advanced manufacturing company. Together, they found a way to turn old glass into new products using 3D printing.
"There's so much glass going into landfills in the U.S.," said Alex Stiles, Vitriform3D's co-founder. "Glass is infinitely recyclable, but only one-third of glass waste is being recycled."
Vitriform3D's glass recycling process begins with crushing bottles down into a sandy powder. A robotic arm smoothly spreads the tiny glass fragments into a square pile, and nozzles along the arm spray an adhesive that glues the particles together, while other nozzles distribute ink to add fresh color. As the arm swings back and forth, adding more glass particles and adhesive each time, layers build up until the powdered glass is transformed into a durable coaster for a table or a beautiful, stain-resistant tile for a kitchen wall. The new object is then dusted off and, like a piece of pottery, heated in an oven to set the final shape.
This 3D-printing process, known as "binder jetting," had already been used with many types of powders, including metal, wood fiber, and sand, but it had not yet been used for crushed glass, which itself is a combination of silica (the main constituent of sand), soda ash, and limestone.
"Essentially, you're glueing the powdered glass together." Stiles said. He said the final product is considered engineered stone, with a composition of 90 to 95 percent glass waste and 5 to 10 percent of a binder polymer adhesive.
Using old glass to make new shapes
Vitriform3D began to take shape when Stiles and Dustin Gilmer, both students at the University of Tennessee, were brought together on a 3D-printing project for ORNL research scientist Tomonori Saito and IACMI - The Composites Institute. Stiles and Gilmer came up with the idea to crush discarded glass for 3D printing, but that sort of powder had never been used before as a printing material.
After developing the initial concept, Stiles and Gilmer were selected in 2022 for DOE's Lab-Embedded Entrepreneurship Program node at ORNL, Innovation Crossroads . The two-year entrepreneurship program provides scientific expertise, funding, and access to equipment and facilities such as DOE's Manufacturing Demonstration Facility (MDF) at ORNL. Their project at the MDF included altering a standard 3D printer's computer software, figuring out the ratio of adhesive to glass powder, and experimenting with different adhesive formulas that would give their 3D printed glass greater strength as well as beauty.
Since then, Gilmer has become a professor at the University of Tennessee while Stiles' main focus has stayed on developing the Vitriform3D technology through a new continued collaboration with DOE's Building Technologies Research and Integration Center at ORNL. This partnership aims to develop recycled glass cladding: the exterior walls that give a building its finished look as well as protection from the elements.
"Glass is extremely resilient, durable, and versatile. It's fire-resistant and can withstand extreme weather conditions," says Nolan Hayes, an ORNL building technologies researcher working with Stiles to explore how recycled glass could be used in construction.
The bulk of the Vitriform3D cladding will be made from a mixture of glass, adhesive, and reinforcing fibers compressed together into a flat layer under sustained pressure. But a separate surface veneer could be printed and bonded to this base layer with raised 3D geometric or swirling glass patterns, adding art to function.
Sparking glass solutions
When Stiles embarked on his quest to recycle glass, he discovered there's not a very competitive market for scrap because glass is heavy and expensive to ship.
"There's a certain grade of sand that is well-suited to make glass," said Stiles. "Depending on the location, it's often cheaper for a company to just use that sand than to use recycled glass." The type of sand used for glassmaking has consistent-sized grains and is usually 98 to 99 percent silica, with minimal amounts of iron and other impurities such as clay. However, there is a growing worldwide shortage of the high-quality sand needed to make new glass.
According to the Glass Packaging Institute , a trade association representing the North American glass container industry, recycling glass not only saves in raw material costs but also decreases energy use and prolongs the life of furnaces used in glass manufacturing.
Large-scale glass recycling can be complicated by the accidental introduction of other objects, such as ceramics. "If a recycling facility were to get a truckload of glass bottles and it had one coffee mug in it, that would shut down their entire production line for a day," Stiles said.
Stiles decided to start his own glass recycling company, picking up bottles each month from Knoxville residents. He named this company Fourth & Glass , a nod to the historic Fourth and Gill neighborhood where he lived. This company has now collected tens of thousands of pounds of glass that otherwise would have been sent to a landfill.
After the glass is cleaned, Stiles pulls out glass of different colors depending on whatever project he's currently developing - blue for some decorative tiles, clear for a 3D-printed sign - and then sends the remainder to a large scale-crusher in Blount County, Tennessee. That facility uses the crushed glass for road development and other county construction projects.
To help others reinvent waste through innovative design, Stiles is installing a 3D printer at Lawrence Technological University in Detroit so architecture students there can design their own recycled glass building accents.
"This will be the first time that architecture students can really sink their teeth into what they could do with this technology," he said. "For the projects with Oak Ridge National Laboratory, that's more focused on what can we do on an industrial scale. If we had a massive printer, how many thousands of tons of glass can we turn into wall paneling? But a micro-factory like the installation in Detroit could focus on smaller projects.
"With a few pieces of equipment, you too could take a glass bottle, crush it into sand and turn it into something new."
The Manufacturing Demonstration Facility, supported by DOE's Advanced Materials and Manufacturing Technologies Office, is a nationwide consortium of collaborators working with ORNL to innovate, inspire, and catalyze the transformation of U.S. manufacturing.
As a DOE user facility, the MDF is the blueprint for the national laboratory system's C4 Partnering Model, which seeks to increase cross-sector collaboration and rapid technology development. This model seeks to decrease a technology's speed-to-market and enable a strong regional manufacturing and commercialization ecosystem. Learn more about C4 partnering opportunities across the United States .
UT-Battelle manages ORNL for the Department of Energy's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, visit energy.gov/science . - Leslie Mullen
