Meh. Easier to put them on my grass and fertilize the soil.

I use coffee grounds for D&D terrain. They simulate dirt nicely by themselves, but with a wash and some flocking they look great.

This is the best summary I could come up with:

But if you’re looking for a truly novel application for coffee grounds, consider using them as a sustainable material for 3D printing, as suggested by a recent paper published in DIS '23: Proceedings of the 2023 ACM Designing Interactive Systems Conference.

“You can make a lot of things with coffee grounds,” said co-author Michael Rivera of the University of Colorado, Boulder, and the ATLAS Institute, who specializes in digital fabrication and human-computer interactions.

As 3D printers have moved into more widespread use, it has sparked concerns about environmental sustainability, from the high energy consumption to the thermoplastics used as a printing material—most commonly polylactic acid (PLA).

Adding biomass fillers (bamboo or hemp fiber, oyster shells, and yes, spent coffee grounds) makes recycling even more labor and energy intensive.

Inspiration struck while Rivera was a graduate student at Carnegie Mellon University and a regular at Arriviste Coffee Roasters cafe in Pittsburgh.

The dried grounds were sifted with a standard kitchen strainer to remove large clumps and then mixed with xanthan gum and carboxymethyl cellulose powders, which serve a similar purpose to binders, stabilizers, and thickeners.

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Many of these types of ideas are to use an easily compostable material and mix it into the plastics as a filler or add tons of binders. The most common 3d printing plastic PLA, is technically biodegradable but will only undergo sufficiently rapid degradation in industrial composters which have elevated temperatures. I was investigating using cellulose acetate based filament but it seems there are still quite a few issues with what I was able to find in the literature (low flexibility and brittle, additives can interfere with biodegradability). Some proposed methods use other plastics that seem to respond well when mixed with cellulose and the same plasticizers but I haven’t seen much other literature focusing on making cellulose based (as the main polymer, not as an additive) filament (not printed dissolved in a solvent as a gel and then dried).

https://www.youtube.com/watch?v=jCsnVp6mEbk

As for this method, if using binders that are easily and cheaply made, and are biodegradable, then I see no issue other than needing to use specialized printers. TBH I wouldn’t mind prints which can’t withstand being dipped in water because most prints probably aren’t being wetted anyways.

I don’t drink coffee but I dispose of tea leaves in the pots of my house plants. Seems a bit simpler, not gonna lie.