Researchers at the University of Colorado Boulder, US, developed a methods for 3D printing a wide range of object using a paste of waste coffee grounds.

The project was led by Michael Rivera, an assistant professor at the university. He got the idea when he was a graduate student at Carnie Mellon University, when he noticed that his coffee shop couldn’t compost the coffee grounds during the COVID-19 pandemic, so they just threw it away. Thus, Rivera offered to take it.

Most consumer 3D printers print with thermoplastics of some kind, with the most common being polyacrylic acid (PLA). This is a biobased plastic and theoretically compostable, but it is not widely accepted by composting facilities and generally ends up on the landfill.

The new filament aims to reduce the amount of PLA needed and is biodegradable. Dried coffee grounds are mixed with cellulose gum and xanthan gum, two common food additives that biodegrade easily, and water.

The material is not a hard filament like PLA, so to print it, the 3D printer has to be modified with plastic tubes and a syringe filled with coffee paste. When dried, the objects become as hard as unreinforced concrete.

The team created small planters from the material that can be used for acid-loving plants like tomatoes. When the plants get big enough, they can be planted in the soil, pot and all. The team can also add activated charcoal to its grounds to make parts that can conduct electricity, such as buttons for sustainable electronics.

Photos: Michael Rivera / Pexels