Tropfrog wrote:
Calcium is totally ph neutral and dont affect ph at all. The eggs contains calcium carbonate, also called lime. When lime is broken down in a wet and acidic environment it releases calcium and carbonate. The carbonate part helps to neutralize the acidic environment and increase ph. If you have soil ph over neutral 7, lime will not break down and no effect on soil ph at all.

So egg shells will be very beneficial if you have acidic tap water and want to grow alkaline loving species. In this case you will find that egg shells not at all decompose slow, quite the opposite.

Sigh, yes, calcium carbonate.

And as you know very well.. too low a PH is rarely the problem. Too high however, is for many, as many have to deal with hard water, the reason why people transfor to rain water in many cases.

As for the speed of things,
www.gardenmyths.com/eggshells-decomposition-study/

Well. That link suggests that egg shells dont break down very fast in alkaline soil. That is perfectly expected as it takes acidic conditions to break down. I would not call it decompose as that is a process involving microbes eating organic matter. Egg shells are not organic matter, it is a quite common chemical compound. It has no nutritional value for the microbes. It is acid and water that breaks down egg shells and not microbes.

Why are you arguing this?

You really think you are being helpfull for the OP?

No, I am not arguing. It is called discussion. Perfectly fine in a discussion forum. If it is helpful or not for Ivan is not up to me or you to decide.

Sounds like they aren't going to be any help.

Our water is never acid and usually slightly alkaline. Water here already has some calcium in it, so egg shells would do nothing.

I was looking at all the eggshells we throw away thinking there must be something useful to do with them. I guess not.

Egg shells at worst case scenario would have no benefits and at the same time cause no harm at all to the plants and at best would add nutrients and benefit the plants.

I throw all kitchen waste in the same bin (egg shells, meat, dairy, bones, you name it), and then use what they call EM (effective microorganisms?) to ferment them (outside of Japan the Japanese term "bokashi" is widely used, but here in Japan its just EM), and then I bury them in my backyard. Because of the anaerobic fermentation process, the compost has pH < 7, and maybe the egg shells balance it out? My vegetables seem to like it, so I haven't given it much thought, and, I already have enough bins for all kinds of garbage and don't want to begin sorting kitchen waste into different bins... For bonsai, I mostly use inorganic substrates (akadama + kiryu).

There's a lot of discussion on whether or not the EM fermentation is useful or not. What I see as a benefit is that stuff like meat/fish/dairy will not smell like dead corpse after a few weeks in the bin.

Ivan Mann wrote:
I was looking at all the eggshells we throw away thinking there must be something useful to do with them. I guess not.

One down, 14 left to try:

www.tasteofhome.com/collection/eggshell-uses/

Eggshells in coffee is worth a try.

Tropfrog wrote:

Ivan Mann wrote:
Egg shells are mostly calcium, and I would think that it would lower the pH of the soil, which might be good for some trees and bad for azaleas, etc.

Comment?

Calcium is totally ph neutral and dont affect ph at all. The eggs contains calcium carbonate, also called lime. When lime is broken down in a wet and acidic environment it releases calcium and carbonate. The carbonate part helps to neutralize the acidic environment and increase ph. If you have soil ph over neutral 7, lime will not break down and no effect on soil ph at all.

So egg shells will be very beneficial if you have acidic tap water and want to grow alkaline loving species. In this case you will find that egg shells not at all decompose slow, quite the opposite.

Very well explained! Thank you for the clarification.