From your morning coffee to a plantable pot

According to a new study from the University of Colorado Boulder, coffee could help reduce waste from 3D printing. A team led by Michael Rivera, assistant professor in the ATLAS Institute and Department of Computer Science, developed a method for 3D printing a wide range of objects using a paste made entirely of old coffee grounds, water and a few other sustainable ingredients.

The team has already experimented with using coffee grounds to craft jewellery, pots for plants and even espresso cups. The technique they developed is simple enough to work, with some modifications, on most consumer-grade 3D printers.

According to Rivera, items made with the coffee grounds can also be put back through a coffee grinder and reprinted into other items.

The researchers presented their findings at the Association for Computing Machinery’s Designing Interactive Systems conference in Pittsburgh.

Rivera’s vision began in a coffee shop he often worked out of when he was a graduate student. 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 waste began to pile up.

Rivera took the grounds and realised he could solve several problems in doing so: reducing plastic waste and preventing the grounds from ending up in landfill.

The team’s method is simple. Rivera and his colleagues mixed dried coffee grounds with two other powders they bought online: cellulose gum and xanthan gum. Both are common food additives and degrade easily in a compost bin. The researchers then mixed in water until it reached a peanut butter-like consistency.

That ooze cannot be loaded directly into a 3D printer. First, the printer needed to be modified with plastic tubes and a syringe filled with coffee paste. When dried, the coffee grounds material is as tough as unreinforced concrete.

“We’ve made objects with a ton of usage,” Rivera said. “We’ve dropped them, and they haven’t broken yet.”

There is potential for turning coffee grounds into tangible objects. Rivera has made 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, they, along with the pot, can be planted in soil. The team can also add activated charcoal to the grounds to make parts that can conduct electricity, such as buttons for sustainable electronics.

Rivera noted that this may never become a widespread practice, but can instead be a step towards discovering other kinds of sustainable 3D-printed materials that could replace plastics.

Image credit: Michael Rivera.