Every year, Americans drink around 1.6 billion pounds of coffee, but most of the used coffee grounds—over 1.1 billion pounds—end up in compost bins or the trash.
Only about 30% of a coffee bean dissolves in water, meaning a lot of coffee waste is left behind after brewing.
Danli Luo, a doctoral student at the University of Washington, saw a creative way to reuse these coffee grounds.
She realized that coffee is packed with nutrients and is already sterilized during brewing. This makes it perfect for growing fungus, specifically Reishi mushrooms.
Before mushrooms sprout, they develop a white root-like system called mycelium.
This mycelium can bind materials together, creating a lightweight and water-resistant material that could be used as a sustainable alternative to plastic.
Luo and a team at UW developed a method to turn coffee grounds into a paste that can be 3D printed. They named this paste “Mycofluid.”
It is made by mixing used coffee grounds with brown rice flour, Reishi mushroom spores, xanthan gum (a common food thickener), and water. The team even built a special 3D printer attachment to handle the paste.
Once an object is printed, it is placed in a covered container for about 10 days. During this time, the mycelium grows over the surface, forming a tough shell.
The team successfully printed and fused together various objects, such as packaging for a glass, a small vase, a Moai statue, and even a tiny butterfly-sized coffin. After the mycelium skin formed, the objects were dried for 24 hours to stop further mushroom growth.
The final material is strong and durable, similar to polystyrene, which is used to make Styrofoam.
Although slightly heavier than Styrofoam, it holds its shape and absorbs little water. Since all ingredients are natural and biodegradable, the material should break down in compost over time.
While the team has not officially tested its compostability, everything used to make Mycofluid is compostable—and even technically edible, though not tasty.
Luo’s team sees this innovation as a potential solution for small businesses looking for eco-friendly packaging options.
Their goal is to replace harmful materials like Styrofoam with sustainable, customizable alternatives. Scaling up production could be a challenge since Mycofluid requires uniform coffee grounds, but the team is exploring other types of food waste that could work in similar ways.
“We want to develop flexible solutions that can help reduce plastic waste,” Luo said. “This is just the beginning—we’re excited to see what other bio-based materials can be used for 3D printing.”
The team recently published their research in the journal 3D Printing and Additive Manufacturing, and they hope their work will inspire more eco-friendly innovations in the future.
