Bioplastics from eggshells
Eggshell is 95% calcium carbonate. It seems more likely to be used as an additive in a composite plastic.  Testing composite plastics produced from adding ground eggshell to common plastics may make for an interesting science project.

References:

Dissertation on meat and bone meal derived plastics

Patricio Toroa et. al. Eggshell, a new bio-filler for polypropylene composites