University of Colorado Boulder 3D prints with coffee grounds

According to a study from the University of Colorado Boulder, coffee waste could be used as a suitable material for 3D printing. The project is led by Michael Rivera, an assistant professor in the ATLAS Institute and Department of Computer Science at the university. He and his colleagues have developed a method for 3D printing a wide range of objects using a paste made entirely out of old coffee grounds, water, and a few other sustainable ingredients.

The team has already experimented with using coffee grounds to craft jewelry, pots for plants, and espresso cups. The technique is also simple enough that it will work, with some modifications, on most low-cost, consumer-grade 3D printers.

“You can make a lot of things with coffee grounds,” said Rivera. “And when you don’t want it anymore, you can throw it back into a coffee grinder and use the grounds to print again.”

For Rivera, the project is part of his mission to make 3D printing more sustainable – allowing artists, designers, engineers, and more, to quickly make graspable prototypes and other household objects without adding to landfills. “Our vision is that you could just pick up a few things at a supermarket and online and get going,” said Rivera.

It all began in a coffee shop

When Rivera was a graduate student at Carnegie Mellon University, he often worked out of a café in Pittsburgh called Arriviste Coffee Roasters. The coffee shop contracted with a local group to pick up its used coffee grounds for composting, but during the COVID-19 pandemic, that wasn’t possible – and the waste began to pile up.

“The owner told me, ‘I don’t know what to do with it. So I just throw it away,’” said Rivera, who joined CU Boulder as a postdoctoral researcher in 2022. “I looked at the grounds and said, ‘Maybe I can do something with them.’”

Rivera explained that most consumer 3D printers on the market today print with thermoplastics of some kind. The most common is polylactic acid, or PLA. This material is, theoretically, compostable, but only a fraction of composting facilities will accept it.

“If you throw it in a landfill, which is where the majority of PLA ends up, it will take up to 1,000 years to decompose,” said Rivera. He realized he could solve several problems at the same time: reduce plastic waste, find something to do with all those used grounds, and enjoy some coffee in the process.

Grounds for celebration

The team’s method is pretty simple, Rivera noted. He and his colleagues from the University of Colorado Boulder mix dried coffee grounds with two other powders that they buy online: cellulose gum and xanthan gum. Both are common additives in food and degrade easily in a compost bin. Next, the researchers mix in water. “You’re pretty much shooting for the consistency of peanut butter,” said Rivera.

You can’t load the ‘ooze’ directly into a 3D printer. First, Rivera does a little jury-rigging – modifying a printer with plastic tubes and a syringe filled with coffee paste. But the group’s creations are surprisingly hardy. When dried, the coffee grounds material is about as tough as unreinforced concrete. “We’ve made objects with a ton of usage,” said Rivera. “We’ve dropped them, and they haven’t broken yet.”

Rivera reportedly sees a lot of potential for turning coffee grounds into tangible objects – having, for example, made already small planters out of coffee grounds, which can be used to grow seedlings for acid-loving plants like tomatoes. Once the plants get tall enough, you can plant them, pot and all, in the soil. The team can also add activated charcoal to its grounds to make parts that can conduct electricity, such as buttons for sustainable electronics.

Rivera noted that printing with coffee grounds may never become a widespread practice. Instead, he sees the project as a step toward discovering other kinds of sustainable 3D printing materials that could, one day, replace plastics.