I had a light bulb moment this morning. I thought lime can be made from oyster shells. You feed chickens oyster shells to get thicker egg shells. I wondered if theres calcium carbonate that can be burnt then slaked to make lime. I have awful internet, but with some quick googling it appears to be true.
I didnt know if i should put this in the critter forum, building forum, growies forum, or what. Lime is used for covering wattle and daub, preserving eggs, making concrete, making acidic soil more alkaline, making glass, and probably a lot of other thigs. I guess you would need a lot of shells to lime a house, but hey. save them up for a year or two and just see what you get.
I tried this recently with my daughter, made a small kiln with some firebricks and a tiger torch. We put finely ground egg shells in a stainless bowl and set the torch to it for about 1/2 hour. Only a top thin layer calcined, everything below was full of black soot, I guess next time we need to stir and burn longer.