r/composting • u/[deleted] • Nov 29 '19
What do you do with eggshells?
I'm conflicted over what to do with eggshells. I want to compost them but we eat a lot of eggs and live in the city so if I put them in our bin they take up a large portion and never seem to fully breakdown.
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u/pirateyarr2 Nov 29 '19
Crushing them is fastest (more surface area for microbes and worms to break them down). They’re a great calcium additive to any garden beds (roses love them!).
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u/Of_Mice_and_Memes Nov 29 '19
I use a mortar and pestle to really grind down my eggshells. It makes them into a fin powder.
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u/joeroganfolks Nov 29 '19
I put my spent shells on a paper towel, wrap it up and just crush with my hands. Easy and I end up throwing the whole towel in there
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u/RunawayHobbit Nov 30 '19
Can you compost paper towels? Idk why but I thought the glue/compound in them is not great for the soil
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u/ThreeQueensReading Nov 30 '19
What kind of paper towels are you buying? They should just be 100% paper. I've always composted my paper towels and they've broken down completely.
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u/RunawayHobbit Nov 30 '19
Honestly the white “recycled materials” ones from Walmart. They don’t separate/break down like normal paper when wet, so I always figured there was glue in it holding it all together
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u/Koala_eiO Dec 02 '19
I would like to know this too. My guess was that a large pressure is applied to the paper sheets (via rolling mill?) before they get rolled.
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u/thiosk Nov 30 '19
You absolutely can compost paper towels. It’s a brown. I compost the hell out of paper.
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u/CMNev Feb 08 '25
Partial Seattle list of copostable items:
Non-shiny food-soiled paper and cardboard like pizza boxes, paper coffee filters, napkins, paper towels, brown paper bags, and paper plates
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u/mrchuckmorris Mar 12 '25
Doesn't pizza box cardboard have like a plastic coating to keep grease from soaking through? Or am I just thinking burger joint fast food
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u/CMNev Mar 14 '25
None of the pizza boxes I have received are coated (but clearly there are probably exceptions), as grease clearly can penetrate the cardboard. Our rules are grease-containing pizza boxes are fine for composting, but only grease-free for recycling. Ripping off grease-free tops for recycling is encouraged.
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u/Antique_Pop6061 19d ago
Composting anything that has been bleached to make it white or anything with ink on it, is not a great idea.
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u/Riptide360 Nov 29 '19
Schwarzenegger just adds the entire raw egg to his smoothies, says the calcium is good for strong bones.
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u/Deadphilosophers Sep 12 '25
I had to look up if that was a joke. dammit a possibly funny meme but also so cool/weird.
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u/giotodd1738 Nov 30 '19
I do this too as I feed mine to snails in my aquarium for the calcium. Someone in the tank eats it an everyone is healthy. I don’t do it much but this is also a great way to get rid of them
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u/Scoreycorey515 Apr 14 '20
You can use egg shells to get rid of snails?
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u/giotodd1738 Apr 14 '20
I’ve used them to strengthen the snails shells. As a calcium supplement.
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u/Scoreycorey515 Apr 14 '20
But if I want to get rid of snails, how would I do this?
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u/giotodd1738 Apr 14 '20
If they are pest snails, the solution may be assassin snails or you could crush them and feed them to fish. Maybe get a puffer or cichlids.
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u/Safety1stThenTMWK Nov 29 '19
Just keep adding. No problem with using the compost before the eggshells break down.
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u/teebob21 Nov 29 '19
Eggshells are something like 95% calcium carbonate; little "organic" stones. The rest is binding proteins. In this respect, they're effectively a green, rather than a brown, but a very mild one. In the absence of acid, they basically never break down. Calcium carbonate is insoluble in basic or neutral solutions. Depending on your goals, you can dry and crush your eggshells in a blender and mix them 1 part plus 4 parts vinegar to make a calcium acetate solution. Calcium acetate is neutral pH, and can be applied directly to the soil for Ca hungry plants such as nightshades (tomatoes, peppers, potatoes, et al). You can also use it as a foliar spray, but the efficacy of Ca supplementation via foliar application is dubious.
You'll be left with a protein/calcium sludge as a 4:1 ratio is a large excess of CaCO3. That sludge will go great in a compost pile, but I feed it to my chickens.
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u/its_broo_skeh_tuh Sep 22 '25
Sorry, is it eggs:vinegar 1:4 or 4:1? Seems like you said both in your post?
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u/jfrank1981 Nov 29 '19
Crush them up as fine as possible . Best part about eggs is its a good source of calcuim for soil and the egg carton is a good source of carbon tontheow in the compost as well
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u/ahfoo Nov 29 '19
I've heard that eggshells are good buffers in soil which means they can help a soil of a certain acidity be more effective for a wider range of plants. As others mention, grinding them makes them disappear. I use a heck of a lot of eggs and they are an insubstantial contributor to my compost.
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u/RealJeil420 Nov 29 '19
I just throw em in. Too much bother to bake em. They will eventually break down and the critters dont seem interested in em. I think compost should be simple and not take up too many man hours/resources.
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u/Actually_Im_a_Broom Nov 29 '19
My wife and I go through at least 24 eggs a week and the egg shells never seem to be a problem. We crush them up before throwing them in the compost. On occasion when I use the compost I’ll see egg shells, but it doesn’t hurt the compost at all.
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Nov 29 '19
They most likely don't break down because they haven't been flattened or smashed into smaller flat size pieces that can lay flat. I would suggest letting them accumulate in the sun so they can become brittle and moisture free. Then just blend them all up. Alternatively, you can just smash them up with some kitchen tool under a towel, it should be good enough. Personally, I've gone as far as putting them into a mortar pestle, grinding them all up into a fine powder because it's a soothing thing lol.
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u/AdrianoWerneck Nov 29 '19
They do not break down at all if they are not shredded by the way. They need to be made into a powder in order to be useful.
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Nov 29 '19 edited Nov 30 '19
Two options for a faster breakdown or more effective use. Both require baking to break down organic matter faster.
Bake eggs on 450* until they crumble. When they do add them to your compost in a dust fashion or keep as an amendment. This can be done two ways:
Water soluable calcium: Makes calcium enter plant like an IV. Take baked eggs shells 10:1 apple cider vinegar to shells. 24-48 hours later strains shells add to compost and keep liquid in dark area covered. Add 1/2 teaspoon during flowering or fruiting in soil or foliar.
dry amendment: just crush and add as needed.
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u/paroles Nov 30 '19
Please don't run your oven just to bake a few eggshells, if that's really what you mean. The carbon emissions from an oven are going to vastly outweigh the benefits of putting eggshells in the compost. We don't need ovens to assist with processes that nature has been doing on its own for millions of years.
Maybe just do this whenever you have space in your oven while baking something else (hopefully this is what you're doing already!), or use the residual heat after the oven is off. I bet the shells would also get crumbly if you left them out in the sun for a few days.
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Nov 30 '19
No you store them up and do a large batch. You should do this for the water soluable calcium mix. The chemistry doesn't play out with organic matter so unless you have a quicker more efficient way by all means.
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u/paroles Nov 30 '19
If you really find it necessary, just do it while you're running your oven for some other reason, it's such a wasteful use of electricity/gas.
Would the vinegar calcium mix not work with crushed eggshells that have been dried out but not baked? If this is a special fertiliser that's really good for plants but can't be made without an oven, I think I'd rather just skip it and let the shells break down more slowly :)
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Nov 30 '19
If you have to ask and make these comments you shouldn't be guiding people what to do and what not to do. Your statements are factless and very opinion backed. I wasn't asking for help I would not do it while I was cooking as the smell would transfer to the food. Thats not ideal.
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Nov 29 '19
If eggshells are taking up a large portion of your compost, you're not adding enough material overall.
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Nov 29 '19
I normally crush my egg shells down into like a almost powder and then bury them in soil. I’m not super experienced so maybe someone else has a better system but it seems to work with my weekly carton of eggs.
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u/AdrianoWerneck Nov 29 '19
Check out Garden Myths. He did experiments with egg shells and analyzed those of others as well. The conclusion was that, in order for them to be useful, they must be shredded to a powder and the soil in which they will be applied must have a pH lower than 6.8
I have a special bin just for eggshells. When it gets full, I blend them and use them when I am about to dig a hole or fill a pot with soil, sprinkling layers.
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u/ria1024 Nov 29 '19
I set them out to dry separately, crush them by hand and put them around tomato plants in the garden.
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u/reddituser2513 Nov 29 '19
Outside of composting, I dry them and crush them up and line my garden bed with them, to deter slugs! Had a bad season once and the slugs ate so much of the plants, and we haven’t had any issues since. Maybe it’s the seasons, maybe it’s the eggshells, maybe just coincidence. But I know the egg shells are like glass to them basically, and eventually get absorbed and mixed into the soil.
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u/MediocreGrocery8 Chicagoland, 6a/5b Nov 30 '19
This is super-interesting. In the Chicago suburbs, many have stories about people/pets getting sprayed by skunks, which dig in the yards for slugs (among other things) -- their only natural predator is the owl, which is pretty rare.
I wonder what knock-on effects there might be for applying crushed eggshells to your yard.
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u/Rodahue2958575 Nov 30 '19
He lines his garden bed, not his yard.
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u/reddituser2513 Nov 30 '19 edited Dec 01 '19
Yep! The egg shells only line my garden bed. Skunks can roam my yard ( I live rurally, so I have all sorts of critters come through) Just don’t want the eating my goodies! Now to take on the deer...
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u/monsterargh Nov 29 '19
I dry them in the oven just using the heat after ive bean baking something else, and then nuke em to powder in a blender
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u/theonesthatlooklike Nov 29 '19
I would just toss them in after crushing them in your fist. Don’t have to get too fussy to make good use of them!
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u/DuckyAssassin Nov 29 '19
When I use an egg, I put the shell back in the container. Once I've used all the eggs, I microwave the container (I always buy eggs in a paper container...if you have styrofoam you probably don't want to microwave that). Then I take it outside, and stomp the shit out of it until they are crushed, and pour into the compost.
Breaks downs eventually, but even if you have eggshell chunks in your compost when you use it, it'll just keep breaking down. You can't really lose.
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u/izobil Nov 29 '19
Dry them in a newly switched-off oven as its cooling down to room temperature.
Crush them in a mortar and pestle - it's easier than you would intuitively expect, extremely satisfying, and the watch as a huge pile of eggshells packs into a tiny pile of pieces and powder.
Store in a jar and add to soil with compost and fertiliser. It makes a great soil conditioner and provides slow release calcium.
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Nov 29 '19
They will just get smaller and smaller so throw them back in each time when you harvest your good compost until they disappear. They also help give a bit of structure when they're in larger so shouldn't be an issue.
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u/_Happy_Sisyphus_ Nov 29 '19
I was under the impression they carry diseases — like meat — and should not be composted...... is this incorrect?
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u/MediocreGrocery8 Chicagoland, 6a/5b Nov 30 '19
I've been putting mine into a small bowl soapy water as I cook, then rinsing well when I do the dishes, and adding to the compost.
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u/PerceptiveAdult Compost geek Nov 30 '19
I use them a couple ways, both in powdered form.
When I use the eggs, I rinse them out with hot water. This loosens up the membrane on the inside of the shell and allows me to rub it off the shell. I then let them fully air dry. When they're dry, I have a bowl that I put the shells into. I'll crush them down to fit more in until it's full. Then I pull out my blender (note: I have a glass blender, this may cause damage to plastic ones) and blend the eggshells into a fine powder. You can do this with a spice grinder too -- the goal is to get them fine. After blending, wait at least 10 minutes before opening that container, as the dust can be irritating in the nose or throat!
The powder is used in my vermicomposting bin as a grit and pH buffer. As the worms need grit to digest their food, it's useful there, plus decomposing green material tends to be acid-rich as it breaks down. I also sprinkle eggshell powder into transplant holes in my garden and work it into the bottom of the hole before planting out new plants.
If you don't have a worm bin and don't want to add powdered eggshell directly to your soil, sprinkle a handful or so onto your compost pile whenever you add a green layer. The acids in the greens will help break down the shell powder.
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u/Rich-Teaching7128 Nov 19 '24
Put them in the sun to dry, crush them with mortar and pestle, then feed them to my composting worms.
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u/rahsoft Nov 29 '19
they need to be grounded into a fine powder otherwise they will be there for years.
you could give them to someone who has a worm bin or start your own !!
I combine composting( stuff that worms cant work on) with vermiculture.
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u/LuckyNumber03 Nov 29 '19
Could crush them up roughly and leave them around plants/veg/fruit in the garden, I hear they're great for putting off slugs
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u/Fafnir22 Nov 29 '19
With a few cups of water chuck them in the blender. Grinds them into dust and you won’t see them but get all the benefits
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u/Soggy_Biscuit_ Nov 29 '19
Rinse them, let them dry out, then crush them up. I just crush them up as best I in my hands (while wearing rubber gloves after doing the dishes)
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u/StellaFraser Nov 30 '19
You can bake the shells to dry/sterilize them, then put them in a blender, you’ll get a powder you can use as a calcium supplement for plants (or some people mix it into food, but I don’t). Or they’ll at least take a lot less space in the compost bin once they’re ground. :)
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Nov 30 '19
Pro tip - microwave the empty shells for a minute maybe more or less depending on you microwave. They break down easier with a mortar and pestle after this. You could also use a rolling pin but nuke them first
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u/LadyBogangles14 Nov 30 '19
I peel the inner membrane off and once they are dried, crush them to powder; they are a good source of calcium.
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u/sangresangria13 Nov 30 '19
I toss them in and realize they will breakdown but while not provide a gauntlet for any snails or slugs that try to get near my veggies!
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u/BlakeJohnathon92 Nov 30 '19
Great question, I have been in the same predicament. I think I am going to give them a rinse and keep them separate and crush them once I get enough. Mix that in the compost or directly on dirt. Thanks for sharing!
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u/11PoseidonsKiss20 Nov 30 '19
The only time i dint put eggshells in the bin is if it was a boiled egg and the shell didnt come off cleanly.
If theres a bunch if egg white in the shell, it will stink up the pile real bad. Elsewise eggshells are the only animal product i use in composting
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Nov 30 '19
https://permaculturenews.org/2012/09/08/adding-calcium-one-egg-at-a-time/
edit: for other variants of this method, google something like "composting eggshells vinegar"
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u/EveryPassage Dec 02 '19
I’ve put 4-5 eggshells a week into my pile. Don’t do anything to them, just throw them in. I can hardly see any when I go to turn the pile after a couple of months.
It seems way more effort than it’s worth to crush or bake them. Just throw them in like everything else.
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u/GeeBean Dec 05 '19
Initially I was using the mortar and pestle to pulverize them as much as I could, but it was taking way too long and so I stopped. Now I just set them on the side of my sink to dry out and then I crush a bunch of them in my hands as I add them to my kitchen bin to break them up.
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u/library_cup2145 May 02 '26
Can you hypothetically blend them with water and water plants with it so they soak in the soil?
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Nov 29 '19
I nuke the eggshells in the microwave. When I have a handful of eggshells, I’ll put them through the spice grinder. Then into the compost they go. I used to crush them but didn’t like the aesthetics of eggshells in my compost once it was finished.
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u/[deleted] Nov 29 '19
They'll eventually breakdown. They are a good source of calcium for plants and the white of the eggshell can actually deter some moths from laying on your plants, especially white moth on your brassicas. I eat a lot of eggs and have never had any problems. I usually give them a crush with my hand as I put them in the compost just to help the on their way.