My first reaction to these questions was whether the cost, in every sense, of the provision of resources used to prepare the eggshells was equal to or greater than the good done by repurposing/recycling them, especially if you grind them using electricity. I'd like to know if there was net gain. I'd also like to know whether your soil has been proven to require more calcium.

Thanks for your (super fast) response.

True enough. Valid points but more as some sort of a philosophical thought experiment.

Serious consideration of the effort and all the time spent in the garden that results in a harvest of fruits and vegetables I could otherwise purchase from the grocery store for a few dollars should prevent me from gardening at all …yet I continue.

You can crush them and feed back to your chickens. Just make sure to crush enough thst they don’t get the idea of eating their eggs. I also question the conclusion that they’re wasted in compost. The same is said about coffee grinds. If you think of compost as a soil amendment rather than fertilizer isn’t anything organic good?

A quick look on the internet shows that the egg-processing industries - who deal with vast tonnes of waste eggs have been looking at this problem for a while, without a whole lot of success. There are lots of posited uses but none would make sense in a home environment - they don't even really in an industrial context.

I approach from a different angle - eggshell pieces in compost may not add as much usable calcium to your soil as some think, but it doesn't hurt either. Having soil with mixed components is overall a good thing, and the benefit of diverting from landfill is, too. (If like me you don't wash the shells, the egg part is mostly collagen i.e. proteins so feeds something in there).

Maybe someday a different process will be found, but for the time being, it adds to your soil, keeps it out of landfill, and doesn't hurt.

To me time spent in the garden isn't effort and it is good for one both physically and mentally. There are huge positives even before there are any veggies to show for it. If one enjoys experimenting with eggshells there might be a positive pay off. But it would have to be a good return on time, effort and resources. My eggshells go on the compost heap simply crushed in one hand.

toxcrusadr

I'll take a crack at these questions.

I have chickens. All the shells go in the compost, then into the garden. I always find it interesting that people worry about eggshells breaking down. First, they do. They break down pretty quickly in my garden---into small chips. Second, if the didn't, why would I care? The other thing that I find to be a positive contribution is that if you vermicompost, you quickly notice how much worms like gathering all their family into slimy balls to take up residence in an eggshell half. If worms are half as enthused in the yard as they are in Tupperware, then I think eggshells are valuable as a worm attractant.

I usually (when I was composting them that is) crunch them up with my hand before tossing them in the kitchen bucket. That way as soon as the membrane holding them together breaks down, there are just a lot of small pieces that are not very visible in the garden.

The first question that comes to mind is, how do you know your soil is Ca-deficient? Then, asking how to extract CaCO3 from eggshells is a bit like asking how to extract iron from horse shoes. Horse shoes, for the most part, are essentially iron, and eggshells are, for the most part CaCO3, which is pretty much insoluble at pH levels that favor garden plants. Decreasing the particle size to something close to fine powder will increase the mineralization rate in soils with active microbiota.

Al

I thought the calcium did leach out in the soil or compost, albeit very slowly, which may not be a bad thing...?

And this made me think of a fun science project I do w/ kids in our rec program, we put seashells into white vinegar in a cup to see them bubble up, and then leave the cups for a week or so to allow the vinegar to evaporate, and as it evaporates, it grows a "crystal garden" of what I presume to be calcium crystals.

Neat experiment. The crystals are a compound containing Ca, but not Ca in elemental form, which doesn't exist in nature because it reacts vigorously with water and other elements to form compounds of Ca.

Al

Might it be calcium acetate?

Yes. The product of the reaction is H2O + CO2 + Ca(CH3COO)2, the later being calcium acetate.

Al

Questions are always good, even the ones like these. What I took from all this is to not worry about the decomposing rate of egg shells in the soil at all. I actually do not believe the original post about the poster did research and found out egg shells do not decompose much in soil, which sounded to me like a pile of poop, but to each his own.

^ I agree. A pile of poop of course would be better, but there's nothing wrong with crumbled eggshells in the soil, becoming white little soil particles that are high in calcium and slowly break down. I think it's fine if you don't specially grind them, just mix them in your regular compost, and they do crumble down to little white bits. Nothing wrong with that!

Coffee grounds are not very acidic, so wouldn't do much to dissolve the eggshells. If nothing else, eggshell pieces can improve soil texture.

Eggshells (ground up) are good for vericomposting. The red wigglers will take care of them.