I can not imagine that even a half inch thick of crushed egg shells on the top of a bin would hurt them. My only concern with egg shells is to not breath pulverized egg shell dust as would be created in a blender. I put them in a bag and roll a wine bottle over them. It is fun and the crushing sound is satisfying. I toss the bag in whole to the bin.

"the crushing sound is satisfying"

You crack me up. :)

Mr Yan, if you have chickens, you can put those egg shells in a separate dish for the chickens to eat 'free choice'. This will give them the calcium they need to keep making sturdy shells.

If you don't have chickens I'm sure you still have plenty of foods going into your worm bin to balance out the eggs, so just put them into the food bucket and let the calcium start reacting with the food juices immediately.

You don't mention how large your worm bin is, so it's impossible to make a worthwhile guess for how much would be harmful. Here's something about aglime that I think is related though. If I put a little aglime on my bin, everything is better. If I put a lot of it on my bin, even though it's a solid powder, it will end up rinsing through 2 feet of material and ending up in the juice collection bucket. When the lime is in the juice bucket, it will flocculate the solids out of the juice and make them settle (just like in a water treatment plant). I don't know if that's good or great for the plants, but it is a pain to keep the solids in suspension long enough to apply the juice to my trees and plants. If you have too many eggshells, I suspect that the excess shells will sit there with nothing left to react to. The worms will likely only eat the ones that are appropriately sized, so the large pieces will likely end up in the finished casts and subsequently sit in the dirt while they slowly dissolve. I consider all of that to be good though because eggshells are pretty stable if there is nothing present to react with them. This makes them a time release PH buffer that supplies calcium as a side benefit.

I've read that every time it rains, a significant quantity of calcium is rinsed below the reach of plant roots. Putting lots of shells in your worm bin means that you have gotten benefit from the egg foodstuff, a sweetened bin, and a lasting supplement for your garden. I would try not to bypass the bin with those, or you may be missing out on the bin benefit as well as simplifying your disposal efforts. Also, if you know you won't be gaining every benefit from the shells during the time frame that they are in the bin, you can free yourself of some of the time involved in crushing them, as they won't all need to be in tiny fragments for the worms to get enough.

Since you already have a stockpile of the shells though, I would resist the urge to add them all at once.

Thanks guys.

These shells were crushed much the same way as Equinoxequinox mentioned. I applied a significant amount of the crushed shells over my gardens and mixed them in with the shredded leafs a bit but I will still have a lot of shells going forward. I have not used a blender or processor to crush shells because I don't want to scratch the plastic housings.

I don't have chickens but I do want to start raising rabbits, but that is a different thread...

I have two bins one is a worm inn and the other is a FT with a 2 square foot cross section. I had grossly over fed them so I have held off for the last two weeks. At this point the worm inn is nearing full. The wooden FT only has 200 to 300 mm of material depth built up at this point.

Last year I had mixed about a cup of crushed shells into the bottom of the holes where I planted a tomato.

If you have any outdoor area, you may want to look into setting up a bin outdoors. If you make it large enough, it should not be possible to overfeed it. The size will also protect it from temperature extremes.

It is surprising how little garbage I now send to the curb since I got a worm bin. Since most everything is intended to be disposable and end up being burned or buried, it's unlikely that even colorful or shiny paper products will contain hazardous ingredients... Unless they come from China. I suspect that nobody is really watching the level of filth they include in their exports.