I use eggshells as a calcium supplement for my dogs and a soil additive. I rinse the shell and remove the membrane, let dry on the counter and store in plastic containers until there's enough to spread out on a cookie sheet. I then put them in the oven on 350 degrees for about 10 minutes. After they've cooled, grind in a coffee grinder (dedicated to egg shells) and store in a plastic container until needed.

I throw them in my fire place.
The calcium will not be affected by heat but it will be pulverised and will be more redily available to the plants.
I do the same with all kind of bones.

Cyrus, do you put them in the fireplace in some kind of metal container (like a can) or do you wrap them in foil -- to keep them separate from the ashes?

I really like the idea of having them pulverized.

Thanks for posting that tip.

I have another question (for anyone). I've heard it's good to mix some eggshells into the soil in the hole you plant the tomato plant in. How much per plant, on average?

As a general rule the soils east of the Mississippi tend to be acidic or slightly acidic and can usually handle some more calcium.

It's too bad that raw eggs could have salmonella. I don't know if the bacteria is only on the outside or what. Those egg membranes are loaded with super nutrients for joints like knees!!!!! I would not reccomend eating them raw.

Somewhat off topic, Completely off topic perhaps. I met a weight lifter at the "Y" several decades ago who threw whole eggs, shells and all, into a blender with some fruit and vegetables and perhaps other stuff and made a drink which he consumed in large quantities.

Albert,
There is a reason you haven't seen him in a couple of decades, he probably died of Salmonella poisoning ;-)

Rather than clean my egg shells before feeding them back to my hens (they need the calcium) I zap them in the microwave for a couple of minutes. Makes them crisp and dry quickly. A warning; the little bit of whites left in the shell is a great bonding agent and becomes nearly indestructible when nuked, so don't put those shells in anything that you don't want to scrub or toss. I put them on a paper plate or napkin for this. The paper plate lasts quite a few zaps and then you can just toss it.

BTW...You are 40x more likely to die in a car accident than to die of salmonella poisoning, much less from salmonella poisoning from eggs. And of course you know that any time you eat eggs with a soft yolk or white, they are raw...just warmed, not cooked.

I put all my egg shells, as is in the compost. Then when compost is done, that goes in the garden.

(I also eat raw eggs all the time)

Your garden typically needs much more Calcium than the egg shells you can provide (from family consumption). Just one tomato plant may need ten, if fully absorbed, and probably more like 50 in real life. That is why I use wood ash, which is about 50% Ca, plus most other micronutrients, about 2lb/100sqft/year. Very sandy soils may need more, alkaline, clay western soils may not need it at all. Yes, I have acid soil, but even if it were neutral, most of the greens would still like the wood ash.