Japanese company Biomass creates a plastic called RiceResin, which is made up of 70% rice. The rice itself is taken from unedible waste which would usually be thrown away or incinerated during food production.

They don’t currently plan on making a 3D printing filament, but a twitter user Archi_Peace has been experimenting with it. The original RiceResin is available in both biodegradable and non-degradable forms and it could be an interesting potential 3D printing material.

https://twitter.com/archi_peace/status/1614911828991311873
https://www.biomass-resin.com/product/riceresin/
https://www.youtube.com/watch?v=ucg2zIfdB6k