You could also use an inorganic binder (e.g. silicate). However, you will need to consider that you will form sodium silicate at high temperatures.
Another alternative could be to use a calcium sol-gel process. For example, infiltrate your pellets with a calcium salt, precipitate the salt as you evaporate the solvent (water).
The water/salt solution should give you enough binder-function during the pressing operation and on calcination, you are only left with calcium oxide.
You may want to check the following related discussion: https://www.researchgate.net/post/which_binder_can_be_used_for_making_pellets_of_snail_shell_based_CaO_powder_and_what_will_b_ethe_method_of_it