Is the calcium deposit in my kettle utilized?

Question

Can plants utilize the calcium that sediments in the kettle when water is boiled? Should we be "feeding" it to them?

Answer 1

Not really - limescale is mostly calcium carbonate, which, in large amounts, might have a mildy alkalising effect on soil, but won't contribute much else other than releasing carbon as it degrades, which isn't necessarily a useful side effect. For the tiny amounts you'll be using, it won't make much impact. If you're dedicated enough to extract and crush the stuff, it might be of some use applied round an alkaline loving plant, say, a single onion growing in the ground.