Spent coffee grounds can be used to make stuff
From an article at Ars Technica written by Jennifer Ouellette
The finished 3D-printed objects are as strong as unreinforced concrete, per Rivera. His team has made small planters to grow seedlings, which can be transferred to a garden—biodegradable planter and all—when the resulting plants are ready. They've made decorative pendants and espresso cups out of this new material. And they created 3D-printed prototype user interfaces for human-computer interactions that changed shape due to shrinkage as they dried—a single-layer square morphing into a saddle shape, for example, or a rectangular rod that bent upwards as it dried.
https://arstechnica.com/science/2023/09/dont-throw-out-those-used-coffee-grounds-use-them-for-3d-printing-instead/
her mastodon post about it here https://universeodon.com/@JenLucPiquant/111109242540886070