Would calcium carbonate make a good substitute for baking soda? How about potassium bicarbonate?
The interesting thing about calcium carbonate as a substitute for sodium bicarbonate is that it is. It is sold as TUMS. Or you can by identical tablets at Sam’s packaged by the hundreds. These tablets are essentially Sugar and Calcium Carbonate.
Although not the best source, they are a calcium source as well .
I don’t know about potassium bicarbonate but would suggest it may not be as readily available and cheap.