Imagine sipping your morning cup of joe, and then using those very coffee grounds to create useful or decorative items. A new project led by Michael Rivera, an assistant professor at the University of Colorado Boulder is turning this proposal into reality, by seeking to harness the potential of used coffee grounds to reduce waste and make 3D printing more sustainable.
The idea emerged when Rivera, during his graduate studies at Carnegie Mellon University, frequented a local coffee shop, Arriviste Coffee Roasters. This café used to compost its coffee grounds, but due to the pandemic, this practice ceased, leaving piles of waste behind. When the owner lamented that he had no use for the grounds, Rivera saw an opportunity.
Most consumer-grade 3D printers today rely on thermoplastics, with polylactic acid (PLA) being the most common material. While PLA is theoretically compostable (with enough time and a few accelerants), few composting facilities accept it. Moreover, in landfills, it can take up to 1,000 years to decompose. Rivera realized that he could tackle multiple issues simultaneously by repurposing coffee grounds: reduce plastic waste, find a sustainable use for the grounds, and enjoy a steaming cup of morning joe in the process.
Rivera’s team has developed a straightforward method. They blend dried coffee grounds with two powders, cellulose gum and xanthan gum, both readily available online and compostable. Water is then added to achieve a consistency similar to peanut butter. However, this paste can’t be directly loaded into a 3D printer.
To overcome this, Rivera made modifications to a printer, incorporating plastic tubes and a syringe filled with the coffee paste. Surprisingly, the resulting creations are quite robust…or should that be… quite robusta? When dried, the coffee grounds material boasts the durability of unreinforced concrete, capable of withstanding drops and impacts.
The potential applications of 3D printing with coffee grounds are vast. Rivera and his team have crafted small planters, perfect for growing acid-loving plants like tomatoes. Once the seedlings reach the right size, they can be planted directly into the soil, pot and all. Additionally, by incorporating activated charcoal into the coffee grounds, the team can produce components that conduct electricity, making them suitable for sustainable electronics, like buttons.
Although printing with coffee grounds may never become a widespread practice, Rivera envisions it as a stepping stone towards discovering other sustainable bio-based 3D printing materials that could eventually replace plastics.
Rivera has published a paper titled “Designing a Sustainable Material for 3D Printing with Spent Coffee Grounds”, which you can access over at this link, just in case you fancy manufacturing some coffee-based feedstock for yourselves.
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