University of Washington 3D Prints Plastic Alternative With Mushrooms and Coffee Grounds

Among those who drink coffee daily in the United States, over 80 percent drink two or more cups a day. At a minimum, that means 14 cups of coffee per week, or 728 cups of coffee a year. In total, Americans throw away  1.1 billion pounds of coffee grounds every year. So how could coffee grounds be given a second life and be meaningfully recycled? Danli Luo, a doctoral student in engineering at the University of Washington, saw a scientific opportunity in her daily encounter with the coffee machine and, together with colleagues, developed a method to 3D print coffee grounds into new shapes. This development offers an ecological alternative to plastic.

From the Bean to the Printer

Coffee is extremely rich in nutrients and is sterilized when brewed. This makes coffee grounds an ideal breeding ground for fungi. When they grow, they first form a complex root system, the mycelium, with a fine, whitish mycelium skin. Mushroom mycelium is now increasingly being used as a fabrication material. Numerous companies, researchers and designers are experimenting with it because it is light, robust and water-repellent. Luo and her team of researchers combined coffee grounds with reishi mushroom spores to leverage both advantages. They also added brown rice flour and xanthan gum. This gave them a printable coffee-based paste, which they called “Mycofluid” and which served as a printing material for new structures.

To upgrade the Jubilee 3D printer in the Machine Agency Lab at the University of Washington, Luo also developed a print head with a larger capacity (1 liter) for the paste, so various objects could extruded. In this process, the reishi mushroom spores injected into the paste ensure that a mycelium skin forms after printing. The printed structures have to be stored for ten days for this to happen. The mycelium skin is then sufficiently formed and contributes to the stability of the printed object. To prevent actual fungal growth on the coffee objects, the parts must be dried. As soon as the moisture formation stops, the fungi stop growing.

Coffee Grounds for Sustainable Packaging

The result is parts that are slightly heavier than polystyrene, but have a similar density to cardboard and are about as strong and tough as polystyrene. In addition, the printed structures are fully compostable and theoretically edible (but possibly not edible). The paste is therefore particularly suitable for packaging materials and represents an ecological alternative to plastic and polystyrene. For example, the team printed packaging for a glass, some vase parts and two halves of a Moai statue.

“We’re especially interested in creating systems for people like small business owners producing small-batch products — for example, small, delicate glassware that needs resilient packaging to ship,” Luo said. “So we’ve been working on new material recipes that can replace things like Styrofoam with something more sustainable and that can be easily customized for small-scale production.”

In fact, Luo mentioned that the process is not intended for series production. It would require large quantities of homogeneous used coffee grounds for scaling up, and this is not always possible. For this reason, the research group is now working on similar bio-based pastes for 3D printing based on this approach.

“We’re interested in expanding this to other bio-derived materials, such as other forms of food waste,” Luo added. “We want to broadly support this kind of flexible development, not just to provide one solution to this major problem of plastic waste.” The full study, published in 3D Printing and Additive Manufacturing on January 23, can be found HERE.

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*All Image Credits: Luo et al./3D Printing and Additive Manufacturing