3D Printing with Used Coffee Grounds

3D printing is a relatively wasteful fabrication method. It is an additive process, which means there isn't any removed material to worry about. But support material, purged filament, priming towers, and discarded prototypes all add up. The 3D printing industry is still small enough that this waste is insignifcant on a global scale, but it is growing. Almost all of that waste is thermoplastic of some kind and even PLA doesn't biodegrade in a reasonable amount of time. To make 3D printing more sustainable, a CU Boulder team led by assistant professor Michael Rivera developed a new coffee ground-based 3D printing material.

Rivera conceived this idea after working at a cafe and seeing the amount of used coffee grounds it generated. Those grounds are typically used for composting, but Rivera thought they might be still be useful before then. Coffee grounds are fibrous, so they can provide some structure. The team just needed a way to hold them together and make them suitable for 3D printing.

After experimenting with different additives, Rivera and his colleagues settled on a mixture of coffee grounds, cellulose gum, xantha gum, and water. Together, these formed a thick paste with the consistency of peanut butter. It can hold its shape after extrusion, then the part can be dried to harden. After drying, Rivera reports that it is quite strong. Even better, the parts are still very biodegradable. They can be composted just like the original coffee grounds and will break down in a short amount of time. Or parts can be ground up and extruded again to form new parts.

It is possible to print this coffee ground paste on affordable consumer 3D printers with minimal modifications. Like a chocolate 3D printer, this only requires a simple syringe-style extruder. The total cost to build a printer capable of handling this material would only be a few hundred dollars and it would work with conventional firmware and slicers.

But it does have a couple of disadvantages. First, the extrusion is very thick and therefore a poor choice when a part has fine details. Second, because the material is so biodegradable, it can't hold up to exposure to the elements. For certain applications, however, it seems like a great choice that could reduce our reliance on thermoplastics.