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Adding Egg Shells to Your Worm Bin

Someone recently asked whether or not it was ok to add egg shells to their vermicomposting systems. The question reminded me that this was something I’ve been meaning to write about for quite some time.

The answer to that question is definitely YES – egg shells are a great addition to your worm and compost bins. They are a great source of slow release calcium and can also act as a buffer, essentially helping to prevent excessively acidic conditions from developing.

I personally prefer to grind my egg shells up as much as possible before adding them – this helps to increase the rate at which the nutrients can be utilized, and also the rate at which the obvious egg shell fragments will disappear from your bin. I also prefer to leave the yolk residues in the shells rather than rinsing them out. This provides a bit of extra nitrogen (and other nutrients I’m sure), which never hurts.

I simply put my fresh shells in old empty egg cartons, making sure not to stack any of the wet ones on top of each other so that they can dry out quickly. Once I’ve amassed a serious collection of shells, I next dump them all in a plastic bucket and grind them with the bottom of a mason jar (any hard object should work fine). You can see in the pictures above what the shells end up looking like.

I’ve read that calcium plays an important role in earthworm reproduction, so you may also see a boost in breeding if you add shells to your bins. If you don’t eat eggs, there are some other options for adding calcium. A lot of worm farmers recommend the use of lime (calcium carbonate – CaCO3) in worm beds. If used in moderation, I agree this can be a useful material, but I recommend against adding it every time you think acidic conditions are developing (as a ‘quick fix’). You may end up throwing the balance of your system off kilter and harming your worms in the process. Composting worms are actually very tolerant of acidic conditions – apparently Red Worms in particular have a pH tolerance range of between 5 and 9, according to Dr. Clive Edwards (renowned vermicomposting researcher).

Rock dust may be a better choice than lime simply because it will likely be a little more slow release (like egg shells), and can contain other beneficial minerals as well.

Written by Bentley on April 10th, 2008 with 30 comments.
Read more articles on Home Vermicomposting.

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30 comments

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Get your own gravatar by visiting gravatar.com Alison
#1. April 14th, 2008, at 7:44 AM.

Thanks Bentley, this is a great help ! I have been drifting the crushed shells over the lawn but I would like to include them in my worm bins.

Get your own gravatar by visiting gravatar.com garyb50
#2. April 14th, 2008, at 5:03 PM.

Great idea… crushing them. I’ve always just crumbled them by hand & tossed them into my veggie can. And they don’t get assimilated that well in the end. I’m going to try crushing them separately next time.

Get your own gravatar by visiting gravatar.com Allen
#3. April 14th, 2008, at 5:49 PM.

What about some or all of the actual egg? At this time of year we always wind up with many more fresh eggs than we can use. I usually wind up scrambling a bunch of them and feeding them back to the chickens. I have been putting some of the egg shells in the worm bins and will probably try to be more consistent with it, especially if it can help reduce the acidity from too much citrus.

Allen

Get your own gravatar by visiting gravatar.com Bentley
#4. April 15th, 2008, at 3:15 PM.

Hey Allen,
As mentioned, I do leave SOME of the egg yolk in the shell, but if I had lots of extra eggs (that needed to be disposed of) I would likely create a separate composting system (maybe even a hot composting pile) since there is much greater potential for putrification and potentially nasty organisms developing. I definitely wouldn’t recommend adding them to any of your indoor worm bins or outdoor bins you work with a lot.

Get your own gravatar by visiting gravatar.com Jomama
#5. April 1st, 2010, at 9:38 PM.

Does it matter if the eggshells have been cooked or not? Can I put peeled hardboiled egg shells in there? How about hardboiled eggshells that have been dyed for Easter?

Get your own gravatar by visiting gravatar.com James
#6. August 8th, 2010, at 8:57 PM.

I used to like to grind the shells after a day or 2 of drying in an old coffee grinder. Is this ok? My worry was making the shell fragments TOO small and sharp. Is there any chance of harming with worms if they were to ingest the shells after grinding? Would larger be better?

Get your own gravatar by visiting gravatar.com Bentley
#7. August 10th, 2010, at 4:24 PM.

That’s an interesting question, James. I would be inclined to say “don’t worry about it”, but I really have no clue if this is the case or not. I would suggest spreading out the ground up shells really well to at least decrease the likelihood of this happening. I certainly didn’t see any evidence that the worms are being harmed by small fragments when I was grinding up my shells (I’m now lazier about it, opting to simply toss them in as-is for the most part)

Get your own gravatar by visiting gravatar.com Mark from Kansas
#8. August 11th, 2010, at 9:10 PM.

James,
I pulverize the dried out egg shells and sprinkle them in,nothing bad has happened to my worms.
The reason I pulverize the egg shells in a mini chopper is that the first time I used the Letty’s mini chopper, I ruined it and she got mad. So now I HAVE to use the mini chopper to justify ruining it.

Get your own gravatar by visiting gravatar.com Robert
#9. August 17th, 2010, at 7:44 PM.

The difference between the two comments ” The answer to that
question is definitely YES – egg shells are a great addition to your
worm and compost bins. ” and the following question and answer.
James’ Q. “Is there any chance of harming with worms if they were to
ingest the shells after grinding? Would larger be better?”
Bentley’s A. ” That’s an interesting question, James. I would be
inclined to say “don’t worry about it”,
” but I really have no clue if this is the case or not.”
I find it irisponsible to give advice if there is no proof that the
answer is correct.
I believe that it’s probably harmful to the worms to swallow sharp
broken pieces of egg shells. I am going to locate some one with a
microscope and see for myself what a ground up piece of egg shell
looks like, compared to a grain of sand. In the mean time, I will
reserve my ground up egg shells to spread around plants that I am
trying to save from slugs.
If you want to read the other side of this controversy, look up how
others have written about slugs and how the egg shells deter them
from going any where near egg shells.
” From Bonnie Willie’s site on slugs.
7. Abrasive materials like ground egg shells, oyster shells or
diatomaceous earth can be placed at the base of plants. As the
slug ripples over the abrasive material their bodies become
lacerated causing the slugs to die from dehydration.

Get your own gravatar by visiting gravatar.com Bentley
#10. August 17th, 2010, at 8:19 PM.

Heya, Robert
Mr. Irresponsible here
:lol:
Thanks for sharing your thoughts. I can assure you that my inclination to say “don’t worry about it” was based on the lack of evidence I have seen (absolutely NONE) that would indicate worms are being harmed during the 10 years I’ve been vermicomposting. It is also based on the numerous accounts of others who have been adding crushed egg shells to their bins. Aside from that, I was simply sharing a personal opinion (not even a recommendation, necessarily) – I always encourage people gather as much information/evidence as they can, and then to come up with their own informed decision.
Discouraging slugs from attacking your plants and adding egg shells to your worm bed are two different things. When attempting the former, you would probably heap them up in a nice thick layer around the base of your plants, thus requiring the slug to actually cross over the material to reach the plant. When adding them to a worm bin, it’s a good idea – as I suggested above – to spread them out a fair bit (mix them in as well).
Anyway, I value additional thoughts and discussion, even when people call me irresponsible (haha) and disagree with me – so thanks again for chiming in.

Get your own gravatar by visiting gravatar.com Robert
#11. August 18th, 2010, at 2:13 AM.

Hi Bentley:
Glad to hear from you. I wondered what got into me for firing off
what I wrote. Thanks for taking it with LOL., and correcting my
spelling of the word.
I’m still interested to see the egg shells under a microscope.
Have you ever had the opportunity to compare them to grains of
sand under magnification?
Thanks again for the response.
Robert

Get your own gravatar by visiting gravatar.com Bentley
#12. August 18th, 2010, at 4:06 AM.

Hi Robert,
Not a problem – no point taking these things too personally, especially when e-communication is involved! Your friendly follow-up certainly serves as an important reminder of this.
Would be interesting to see how the shells look under the microscope, but have not had the opportunity to do so yet.

Get your own gravatar by visiting gravatar.com Roar Irgens
#13. November 6th, 2011, at 6:29 AM.

I am just starting my worm box. I have previously ground egg shells in an old blendor and added that to my veggie garden. I plan to add it to the worm food. I do have a microscope. Will take a look.
i have heard that the worms will nest in half egg shells. Any exoerience on that, anybody ?
Roar

Get your own gravatar by visiting gravatar.com Roar Irgens
#14. November 6th, 2011, at 6:31 AM.

I find the comments usefull and interesting.
Roar

Get your own gravatar by visiting gravatar.com Chad
#15. December 17th, 2012, at 8:13 PM.

We use raw aragonite in our worm bins. All it is is ground up mullusks shell.
Calcium (CaCO3) 33%

Get your own gravatar by visiting gravatar.com Britton Cook
#16. January 6th, 2013, at 5:12 PM.

Hi all! I started my worm bin august 2012 so I’m new at this but having fun doing it. I heard that adding egg shells was a good thing for the worms so i have saved every egg shell i have had for months (along with empty paper egg cartons), and have been crushing up the shells for them. Calcium aids the worms by helping them to reproduce, and also plays a role in aiding their digestion. While as important as calcium is, in order for any living thing to metabolize calcium, proper amounts of magnesium are needed as well. Which brings me to my question. I have heard of people using dolomitic lime to help in the magnesium area, but has anyone ever tried epsom salt with worms before? I ask only because epsom salt would be a great source of Magnesium without adding any more calcium to the mix. I feel like I have plenty of egg shells and don’t want things to get too far off balance. Thank you!
-Britton

Get your own gravatar by visiting gravatar.com Adam
#17. May 13th, 2013, at 12:10 AM.

I add a mixture of crushed egg shells, oyster shell flour and rock dust to all of my worm bins. I’ve had zero problems. They won’t swallow an entire chard of the shell. Even crushed, egg shells are still too big for that. And if you ground it up finely into a powder, they would still be fine. Just like when people add DE to their bins. The worms enjoy that too. I find it irresponsible to call someone as experienced as Bentley irresponsible for giving his opinion based on experience. If you don’t want to benefit from his info, fine. He’s helped me a great deal though and I’m not just a hobbyist in vermiculture.

Get your own gravatar by visiting gravatar.com Adam
#18. May 13th, 2013, at 12:11 AM.

I cover my food waste with the above items at every feeding to keep the bins balanced

Get your own gravatar by visiting gravatar.com Cindy
#19. May 21st, 2013, at 10:29 PM.

If you toss in large pieces of broken eggshells the worms won’t benefit from them as much as they will if you grind them into powder, which they can injest and use as grit. I recommend buying a cheap $17-$20 coffee grinder. I use an old Krups grinder, which, by the way, also does an excellent job of grinding spices. It allows me to grind them into a fine sand like consistency, or powder, depending on the length of time I grind. I save eggshells until I have 2-4 dozen or more, then I spread them out onto a sheet of foil and toss them in the oven and bake them at 350 degrees for 30-60 minutes, then let them cool before grinding. The primary reason I bake them is to remove moisture from the shells to make it easier to grind them and keep them from clumping. Baking also kills salmonella, if present, which isn’t harmful to the worms and they can process and eliminate, but could ptentially make me sick.

II store my powdered eggshells in cheap plastic commercial sized salt & pepper shakers that I picked up at a discount dollar store. I sprinkle eggshell powder and mix it in whenever i make up fresh bedding and I make a habit of dusting the bins every 7-10 days, and I sprinkle a little bit on any food when I add it. This has not only managed to help keep my the pH i my bins balanced for 2 1/2 years, but it also help rovide then with a steady supply of the grit they need.

Regarding adding whole eggs….. I tried this on several occasions. I added two 1/4″ thick slices of hard boiled egg to one of my bins and the worms devoured the whites, but wouldn’t touch the yolks. In ‘Worms Eat My Garbage’ Mary Applegate said it’s safe to add an egg occasionally. Knowing what I now know, I would limit feeding to an occasional eggwhite, but never any yolks. Eggwhites are very high in calcium and low in fat, and the calcium may very well be what my worms were attracted to. Yolks, on the otherhand, are high in protein and fat, so if there is any correlation, the protein might cause protein poisoning (a.k.a. the dreaded and often fatal, string of pearls, or sour bin syndrome). If you would like to try feeding your worms eggwhites, recommend you start off by adding only 1 or 2 thin slices of boiled eggwhite and that you check your bin after 24 hours and if your worms haven’t been eating them, toss them out. In any event, whether the worms are eating or not eating the eggs, you should remove all remaining egg within 48-72 hours before it begins to putrify and start creating a stench.

Get your own gravatar by visiting gravatar.com Adam
#20. May 22nd, 2013, at 5:02 PM.

Cindy… Yeah if you powder the shells, that is good because they consume it much faster. They will still consume larger pieces though. I’ve noticed that crushed shells do last much longer than the fine oyster shell flour. The rock dust usually gets devoured as well. The crushed shells do disappear after awhile though. Regarding larger pieces not benefitting as much, I somewhat disagree. They don’t get consumed as quickly as powder does, but they offer other benefits. One thing I’ve noticed about halves of egg shells is that they love laying cocoons in them. I’m not sure the exact reason for that (protection, membrane, etc..). Any way you do it (coffee grinder, food processor, crushing by hand, leaving whole will help the worms tremendously. One thing I will say is if you are trying to use then to keep the PH neutral, the smaller pieces are better because they’re easier to disperse. If you don’t eat enough eggs or have a restaurant giving their shells to you as I do, rock dust or oyster shell flour alone should be sufficient.

Get your own gravatar by visiting gravatar.com Melissa
#21. May 26th, 2013, at 2:40 PM.

Hi all,

Helpful comments, thank you. I realize I haven’t been crushing the shells finely enough, so they never get assimilated. One question, how are folks storing the empty egg shells before grinding? In the fridge? The freezer? Thank you!

Get your own gravatar by visiting gravatar.com Adam
#22. May 28th, 2013, at 11:14 AM.

Hello Melissa,

What I do is rinse and thoroughly air dry my egg shells. I like to use as little energy as possible because that defeats the purpose of going “green” IMO. After that, you can store them wherever. I have a large 55 gallon drum in my garage that I keep them in. I don’t keep any yolks on them because that can get pretty smelly as Bentley stated.

Get your own gravatar by visiting gravatar.com Melissa
#23. May 28th, 2013, at 1:38 PM.

Thanks, Adam.

Get your own gravatar by visiting gravatar.com Teresa
#24. March 10th, 2014, at 11:44 AM.

We just started our first bin. We are a large family who eats up to 5 dozen eggs in a week sometimes. How much egg shell is too much? Thanks.

Get your own gravatar by visiting gravatar.com J.L. Lucas
#25. March 12th, 2014, at 4:23 PM.

a second hand coffee grinder works well to crush the egg shells

Get your own gravatar by visiting gravatar.com Adam
#26. March 13th, 2014, at 10:45 PM.

I used to use a food processor to grind up egg shells. Even using that did not create powder unfortunately. I now use a Vitamix blender. That thing makes a very nice powder. This works very well and let’s the eggs cover things much better than the small chards in order to keep the PH neutral. This also makes it so your castings don’t have un-processed egg shells at the end (even though that isn’t really a big deal). I still also use my special grit mixture.

Get your own gravatar by visiting gravatar.com Adam
#27. March 14th, 2014, at 6:12 PM.

Teresa…I don’t think there really is a “too much” when it comes to egg shells. Obviously you don’t want to “drown” them in the shell powder or over run a bin with whole egg shells. I usually just lightly coat my fresh bedding with my egg shell flour and sprinkle a light layer over any food that I add to the bins. That stuff is valuable to me so I don’t use too much.

Get your own gravatar by visiting gravatar.com Teresa
#28. March 16th, 2014, at 3:48 PM.

Thanks. I may be overdoing it a little. The worms seems to like it, though. I sprinkle it on top and it’s worked in within a few hours. We’ve been using a molcajete to crush our shells. It’s like an oversized mortar and pestle. It’s not powder, persay, but it’s small enough to suit me and the worms. I’m not particular with the end product since it will just go on my outside plants here at home.

Get your own gravatar by visiting gravatar.com HarryCK
#29. July 20th, 2014, at 12:41 PM.

No one has answered the question above about using epsom salt in your worm farm. Epsom salt is supposedly very good for your plants, so I too would be interested in knowing whether you can use it with worms or not.

Get your own gravatar by visiting gravatar.com Bentley
#30. July 22nd, 2014, at 2:01 PM.

I would avoid using ANY type of salts, Harry, since worms are VERY sensitive to them. I might add some epsom salts at the base of my tomato plants (even though plenty of worms in close proximity), but only because there is plenty of safe habitat close by.

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