How to Use Eggshells in the Garden for Soil, Compost, and as Pest Control

While eggs may be the delight of many home cooks, eggshells can be the bane of many home composters.

A vertical close up of a spade digging into dark, rich soil with fresh eggshells in front of it. To the center and bottom of the frame is green and white text.

I remember my reaction when I dug in to harvest my very first batch of finished compost.

I was thrilled that all of my food waste and garden trimmings had magically transformed into a beautiful, brown, humus-like substance!

All except the eggshells. Lots and lots of them, all still very recognizable.

But I made some changes and I don’t find those big pieces of shell in my compost anymore. You don’t have to either.

In addition to discussing the best way to add them to your compost, I’m also going to cover other ways of using them as a soil amendment, and whether or not they work as a pest deterrent.

Here’s a quick overview of what’s ahead:

Eggshells as Food Waste

Eggshells take up a whole lot of room when you don’t break them up – whether that’s in your compost or your trash can.

Their beautiful oval shapes – so perfect for containing their contents – don’t flatten down well in the trash, unless you take the time to crush them.

A close up of kitchen food waste ready to place on the compost pile.

And many people put them in the garbage without a second thought. According to Paula Felps at Earth911, the US alone sends 150,000 tons of eggshells to landfills every year.

If you do the math, that’s nearly a million pounds of these oval wonders taking up space in landfills, not per year, but per day. Yikes!

A close up of a large number of eggshells on the ground, after cleaning and drying, pictured in bright sunshine.

It makes a lot of sense to try to find alternate uses for these empty former packages of eggy goodness. And that’s where home gardeners can get involved.

Eggshell Nutrients

Before we get into the details of how to reuse this abundant variety of food waste in the garden, I think it would be helpful to examine just what exactly is being thrown away at a rate of nearly a million pounds a day.

A close up of bright white eggshells, still with some of the albumen inside them set on a rustic wooden surface.

Here’s what the average eggshell is comprised of:

  • 95% calcium carbonate
  • 0.3% phosphorus
  • 0.3% magnesium
  • Traces of sodium, potassium, zinc, manganese, iron, and copper

It seems like such a shame to just throw all those nutrients away, doesn’t it?

A close up of a wooden spoon containing eggshells that have been dried and crushed into a power, set on a white surface.

Especially if they could replace a garden product that you might have to purchase otherwise – like agricultural lime.

In fact, a study presented at the 2006 Iowa State University Integrated Crop Management Conference by extension field specialists John Holmes and Paul Kassel found eggshells to be an effective means of reducing soil acidity, on par with agricultural lime, which is mined from limestone.

A close up of a large number of discarded eggshells on the ground amongst straw, with fallen leaves in the background.

And in case you’re wondering, repurposing this type of food waste isn’t just a DIY amendment utilized by home gardeners.

Ground eggshell meal is listed as an organic fertilizer “generally acceptable under the [rules of the USDA National Organic Program (NOP)] for commercial organic farmers,” as described in the North Carolina Extension Gardener Handbook published by North Carolina State University, with an average analysis of 1.2-0.4-0.1 (NPK).

Though nitrogen, phosphorus, and potassium levels offered by eggshells are relatively low, the takeaway here is that what is usually discarded as waste can be an incredible source of calcium, with value as an amendment used both to feed plants and to neutralize acidic soil.

Use as a Soil Amendment

How can you tell whether your garden will benefit from added calcium?

A close up of a garden fork set in dark, rich garden soil, with a yellow bucket to the right, spreading around a white fertilizer substance, pictured in bright sunshine with vegetable crops in soft focus in the background.

It’s important to understand what type of soil you’re starting with – so make sure you read our enlightening article on this subject.

You may even want to do a soil test to see how much calcium your soil already contains.

If your soil is acidic, amending with a source of calcium may be helpful, depending on what you want to grow.

A close up of a berry tree growing in the garden with ripe purple fruits surrounded by green foliage, fading to soft focus in the background.

But there are cases when acidic soil is preferable, such as for growing blueberries and other ericaceous plants. You wouldn’t necessarily want to add an alkaline amendment like calcium in that case.

The results of your soil test will help guide you in deciding if adding calcium to your soil is a good idea or not.

A close up of a pile of shells from cracked eggs set on a soil surface.

If you’re growing tomatoes and other food crops that may suffer from blossom-end rot, the calcium from eggshells may be a big help at planting time.

In a paper published in the March 2016 issue of the International Journal of Innovative Research in Science, Engineering and Technology, Madhavi Gaonkar and A. P. Chakraborty from Dr. Babasaheb Amebedkar University in Maharashtra, India, described their research on using eggshells as a calcium supplement and fertilizer.

A close up of dark, rich garden soil with shell fragments from eggs dug into it, pictured with a small green plant to the right of the frame, fading to soft focus in the background.

These researchers concluded that powdered eggshell is “probably the best natural source of calcium,” and found the use of this amendment could balance soil calcium levels in order to help prevent blossom-end rot.

A close up of red tomatoes growing on the plant suffering from blossom-end rot, a disease that turns the ends of the fruits black and causes them to decay, pictured surrounded by green foliage on a soft focus background.
Tomatoes showing blossom end-rot

Charles C. Mitchell, extension agronomist with the Alabama Cooperative Extension also studied adding this food waste to the soil in a farm setting to neutralize soil acidity.

He determined that adding crushed eggshells to the soil was useless – unless they were ground to a fine powder, smaller than sand.

When ground in this way, he found that this powder was even more effective than agricultural lime, providing a source of calcium that was readily available to plants.

In short, large pieces of shell break down too slowly to serve as an amendment or soil sweetener.  when ground into a powder, they bind to the soil, becoming more readily bioavailable and altering the soil pH.

A close up of a selection of eggshells, some that have been cleaned, dried, and crushed, and others still containing yolk and white, set on a glossy wooden surface on a soft focus background.

In addition to preventing blossom-end rot in tomatoes, the calcium in ground shells can be used to prevent apple cork spot, or as an alternative to amending your lawn with lime.

But before you start sprinkling calcium willy-nilly throughout your garden, you may want to learn more about how plants use nutrients and minerals, so that your use of this soil amendment is well-informed.

Use in Compost

If saving spent eggshells for use as a soil amendment isn’t on your agenda, there are a couple of good reasons why you might want to compost them instead of throwing them in the trash.

A close up of rotting food waste on a compost pile with dark soil in the background.

The first, as discussed above, is to keep them from going to waste in landfills.

Food waste takes much longer to break down in landfills than it does in compost piles, as landfills are sealed off, anaerobic environments.

In this case, anaerobic decomposition is stinky and inefficient compared to aerobic decomposition, the type that takes place in a well-maintained compost pile – where aerobic microbes thrive because of the presence of oxygen.

Those aerobic microbes transform food waste into nitrogen, phosphorus, and magnesium, making excellent material for growing more food!

If you are using an anaerobic composting method at home, such as bokashi – the addition of Lactobacilli bacteria to kick-start the fermentation process – then the shells will break down just fine.

A close up picture of a compost pile with various household food waste, including banana skins, on a soft focus background.

Another motivation for composting your eggshells might be to provide better conditions for earthworms, either in your compost pile, or in your vermiculture bin.

Earthworms need grit to digest their food, and ground up eggshells are an excellent source.

Even if you don’t have a worm bin, you’ll eventually have earthworms hanging out in your outdoor compost pile, and in your soil, so including some shell debris for them will help them to thrive.

A close up of a collection of earthworms in dark, rich composted garden soil.

Before you add eggshells to your compost pile or worm bin, pulverize the dried shells to ensure that your finished compost is smooth and dirt like, uncluttered by large pieces of shell. Note that composting whole eggs is generally not advisable, since the smell can attract rodents.

Grinding them before adding them to your compost or worm bins will also make it easier for the earthworms to use the material as grit.

I’ll share my method for safely preparing ground eggshells with you shortly.

In the meantime, to learn more about keeping your pile balanced, check out our article on the basics of composting.

Use as Seed Starting Containers

Another creative gardening reuse for eggshells is to use them as containers for seed starting.

While this is a viable option for upcycling your kitchen waste, you’ll need to be aware of certain limitations and necessary preparations before getting started.

A close up of a hand from the left of the frame holding a small shell containing microgreens, on a soft focus background.

This seed starting method works best for plants that are small and low growing. Plants that can gain height rapidly, such as tomato seedlings, will quickly outgrow these small containers.

That doesn’t mean you can’t start tomatoes from seed in this way – but if you do, you’ll want to have larger nursery pots on hand for repotting within a few weeks after they sprout.

And keep in mind that repeated repotting is not recommended for most transplants, as this can cause undue stress and damage their roots.

A close up of a cardboard egg tray containing seedlings growing in white shells, set on a rustic wooden surface, with a lawn in soft focus in the background.

On the other hand, low growing plants such as thyme, cucamelons, or certain succulents would be good candidates for starting in eggshells.

A close up of a small seedling started in a shell, showing small succulent growth, pictured on a soft focus background.

It’s best to start seeds in sterile pots, so if you decide to use eggshells as seed pots, the first step you’ll want to take is to make sure you thoroughly clean the shells.

Thicker shells will be easier to clean without breaking than thinner ones.

Generally, shells from younger hens are thicker, and those from older hens are thinner, so if you’re buying eggs from a farm, you might ask the farmers if they have eggs from young layers.

Gently wash out the eggshells with warm, soapy water – or bring them to a boil in hot water to sanitize them.

A close up top down picture of hands from the top of the frame filling small pots made from eggs with dark, rich soil, ready for seed planting. In the background is a white piece of paper and a wooden surface.

Along with a sterile growing environment, young seedlings need drainage.

If you are able to successfully clean your eggshells without breaking them, next poke two or three small holes into the bottom of each shell to ensure the seedlings have well-drained soil. The tip of a metal paper clip works well for this.

When you’re ready to plant your seedlings, remember that whole eggshells don’t break down quickly – certainly not quickly enough to let your young plant’s roots spread out into the soil.

A close up of a transparent plastic container with seedlings planted in the shells of used eggs, with a white label on the front, on a soft focus background.

So you’ll need to remove the seedling from its shell before planting – either lift the seedling out with a widger or small spoon, or crack the shell to remove it.

And if you’d like further guidance in starting your own annuals from seed, follow the helpful directions in our guide.

Use as a Pest Deterrent

Another garden use for this type of readily-available food waste is to pile sharp, crushed pieces of shell around the bases of plants as a barrier, to deter certain soft-bodied pests.

Scattering crushed eggshells around your crops may help to repel cutworms, those nasty caterpillars that like to chop the heads off of your delicate little seedlings.

A close up of a maggot pest at the base of a lettuce plant which will burrow down and damage the plant, on a soft focus background.

Cutworms go for the tender stems of young seedlings, so a common defense against these pests is to block their access by placing collars around seedling stems.

According to T. J. Martin at the Cochise County Master Gardeners office, crushed eggshells are also an effective deterrent against cutworms when a layer is scattered around the stems of sensitive young seedlings.

A close up vertical picture of a small lettuce plant growing in the garden with eggshells placed around the base as a mulch, surrounded by wood chips, fading to soft focus in the background.

However, when it comes to deterring slugs, crushed eggshells aren’t all they’re cracked up to be – pun intended.

In his book, “The Truth About Garden Remedies: What Works, What Doesn’t, and Why,” author Jeff Gillman debunks this DIY slug deterrent by trying the experiment himself.

The Truth About Garden Remedies: What Works, What Doesn’t, and Why

To read more, you can find this book on Amazon.

In fact, I had the pleasure of taking a class with Gillman through the University of North Carolina at Charlotte’s Native Plants Studies program, and I and my other classmates tried this experiment along with him.

We used a paper plate as our testing grounds. Around the inner perimeter of the plate we created a barrier made of crushed eggshells, then placed the slugs in the center of the plate.

Next, we watched to see if the sharp shards would keep the slugs in the center of the plate – or if the slugs would venture across anyway.

We did the same test with pennies as well, since copper is another supposed slug-repelling home remedy.

The result? Neither barrier deterred the slugs. (Cue sad trombone).

A close up of a large slug munching on leafy greens in the garden on a soft focus background.

In his book, Gillman recounts trying several variations of the slug-on-paper-plate experiment.

He found that when the shells were crushed to the size of baby aspirin, and piled into a 1/4-inch deep barrier, he got the best results. These shards slowed the slugs down a bit, but the barrier was not enough of a deterrent to make the slugs turn back or to prevent them from crossing it.

Want to know what Gillman does recommend for controlling slugs? Spoiler alert – it’s beer traps.

You can learn more about repelling slugs in our article.

A close up of the trunk of a tree with crushed eggshells placed around the base on the top of the soil as a mulch, surrounded by green leaves and foliage, fading to soft focus in the background.

I do have to point out that there are many different species of slugs, and as far as I know, Gillman has not tried his experiment on a wide variety of them – so the eggshell barrier may work better against some species than it does with others.

So I’m going to say the verdict is still out as to whether this DIY trick is an effective remedy against slugs in the garden.

In any case, placing pieces of crushed, heat-dried eggshell around your plants certainly won’t hurt them – remember, they won’t even change your soil’s pH over the short term.

What About Salmonella?

Speaking of unpleasant things like slugs… what about salmonella?

I know, I know – this has been your burning question all along, right? How can you possibly use eggshells in your garden without subjecting yourself and your family to the risk of salmonella infection?

A close up of a burlap sack with freshly collected eggs from backyard chickens, still with dirt on the outside, pictured on a soft focus background.

Luckily, I am prepared with an answer – and a solution.

Part of my method for preparing eggshells for the garden involves baking them in the oven to dry them out before grinding.

This practice does a couple of things at once – it dries out the sticky, inner membrane and kills salmonella.

A close up of an empty egg, showing the shell and the inner membrane pictured in bright light on a soft focus background.

You only need one second of moist heat at 170.6°F to kill salmonella bacteria.

The oven-drying method will expose your eggshells to temperatures higher than that for longer periods of time, so you should be able to set aside those worries about salmonella.

Instead, this frees you up to think about more important things – like how you’re going to celebrate naked gardening day when it rolls around again!

How to Make a Soil Amendment

Now that you have put your worries about salmonella to rest, it’s time for the fun part: preparing your eggshell powder for use in compost or as a soil amendment.

A close up of a white ceramic bowl containing used eggshells that have been cleaned, set on a blue wooden surface with a rustic blue wooden fence in the background in soft focus.

In three words, you’re going to collect, dry, and grind.

Collect

First, collect your shells and rinse them under a tap to remove any raw egg to avoid attracting flies, or unpleasant smells.

Place them in an ovenproof dish such as a casserole dish or cookie sheet. Once the dish is full, you’re ready to dry them. The amount of time it will take to fill the baking dish depends on how often you eat eggs, and how many egg-eaters are in your household.

Don’t bother trying to crush them while you’re storing them in this way – it will be much easier to crush them once they are dry.

And by the way, I’ve been handling my eggshells like this for several years now, and in several different climates, ranging from the temperate Southern Piedmont, to the arid Intermountain West, to the damp Pacific Northwest.

I’ve personally never had any problems from storing them this way over the short term – no mold, no pests, and no odor – although I will admit that I do a lot of baking, so my shells tend to get a drying heat treatment at least once a week.

If you are concerned nonetheless about whether keeping raw eggshells is a potential health issue, you could certainly boil them first.

Just be aware that you will lose some of the calcium content of the shells, which will be leached into the water while they’re cooking. You can also let this water cool and use it as a soil amendment.

Dry

Now that you have a baking dish full of raw shells, wait until the next time you need to preheat your oven.

While the oven is preheating, place the baking dish full of eggshells into the oven for a few minutes.

A close up of a hand from the left of the frame turning an oven dial to switch it on, with a digital display showing the time on a soft focus background.

If you are using a glass baking dish, make sure the oven temperature is no higher than 350°F – some glass dishes can crack at higher temps. Except of course if you are using Pyrex or a similar brand that is safe in the 400°F range.

I actually store my collected eggshells in a baking dish in the oven prior to drying them out, to keep them out of the way.

Then, any time I plan to do some baking and am preheating my oven, the baking dish and its contents are ready to go, and I allow them to heat up for several minutes.

This dries out those wet membranes – although usually they have dried on their own by then – and exposes the shells to temperatures that will kill salmonella.

Grind

Once my shells are all sufficiently dried out, I grind them up into a fine powder. The best solution I have found for doing this is to grind them in my blender.

Working in small batches, place dried shells in the blender, and grind to a powdery consistency. When all of the shells are finely ground, transfer them to a mason jar for storage.

A close up of a white ceramic bowl containing eggshells that have been dried and crushed, with others scattered to the left and right, set on a wooden chopping board on a white background.

Now your homemade eggshell powder is ready to add to the soil for added calcium or to counteract acidity, or to your compost to biodegrade further.

Or you can simply store this powder for later use – just make sure your powder is thoroughly dry before storing it, or add a silica desiccant packet to the jar for added peace of mind.

How to Make a Pest Deterrent

If you want to use eggshells as a pest deterrent, instead of grinding them into a fine powder, you’ll want to crush them into small, jagged pieces instead.

You’ll still want to dry and heat them in the oven as described above.

A close up of a black pestle and mortar containing eggshells that have been cleaned and dried, set on a wooden surface and pictured on a soft focus background.

But instead of grinding them in a blender or coffee grinder, which will result in producing pieces that are too small to deter pests, crush them by hand.

A close up of two hands from the top of the frame using a rolling pin to crush and grind up cleaned and dried eggshells on a wicker basket surface.

You can do this by placing small batches in a mortar and crushing them with a pestle, or place them on a baking sheet and crush them with a rolling pin.

A close up of a purple container with eggshells spread out as a mulch over the top of the soil around the roots of the growing plants, pictured on a soft focus background.

Place your crushed shell pieces in a jar for storage – or go ahead and take them out to your garden and sprinkle them around your plants right away.

Breakin’ Up Isn’t Hard to Do

See? Breaking up your eggshells – and letting them break down – really isn’t that hard to do!

And if you make sure to dry them out for easier grinding, the remainders of your omelets can be easily transformed into a DIY soil amendment or compost ingredient.

As far as using them for pest control – let’s all keep experimenting and report back.

A close up of shells of eggs mixed in with rich, dark soil in the garden.

What do you think, readers? Have you successfully used this food waste to amend your soil or deter pests? Let us know in the comments.

And if this article has piqued your interest in edible gardening by repurposing food scraps, you can read more articles on that subject right here:


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A collage of photos showing eggshells being used in a garden.

© Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Product photo via Timber Press. Uncredited photos: Shutterstock.

About Kristina Hicks-Hamblin

Kristina Hicks-Hamblin lives on a dryland permaculture homestead in the high desert of Utah. Originally from the temperate suburbs of North Carolina, she enjoys discovering ways to meet a climate challenge. She is a Certified Permaculture Designer and a Building Biology Environmental Consultant, and holds a Bachelor of Arts degree in liberal studies from the University of North Carolina at Greensboro. Kristina loves the challenges of dryland gardening and teaching others to use climate compatible gardening techniques, and she strives towards creating gardens where there are as many birds and bees as there are edibles. Kristina considers it a point of pride that she spends more money on seeds each year than she does on clothes.

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Irene
Irene (@guest_7324)
6 months ago

What about using a microwave oven to dry the shells out?

Emily
Emily (@guest_7334)
6 months ago

I love your idea of putting them in the oven to dry them out. I usually boil them & dry them in a plate on the counter. It’s a little unsightly, but once they’re dry I put them in a paper bag & tuck them away for later.

Dottie
Dottie (@guest_7503)
6 months ago

I dry and crush my egg shells to add to the seed in my bird feeder. It is especially good during the Spring when birds need the extra calcium for egg laying.

Clare Groom
Clare Groom (@clareg)
Admin
Member
Reply to  Dottie
6 months ago

That’s a great idea Dottie, thank you for sharing!

Gabrielle Falk
Gabrielle Falk (@guest_7510)
6 months ago

Hello. I’m from Sydney, Australia. Didn’t plant any veg./herbs this summer just gone-far too hot. Plus we had severe water restrictions. Could only water early am, late pm with buckets of water. However. Can I just dry the egg shells, crush, and add directly to my vegetable containers? Thank You. :mrgreen:

Sue
Sue (@guest_10388)
1 month ago

The strange thing about all of these articles is that NONE THEM INDICATE HOW MUCH to add.