Can You Compost Oyster Shells? 🦪

Reading Time: 8 minutes 🍃

If you live in a coastal area, you may be used to enjoying fresh seafood, such as oysters. And if you’re an avid or a brand-new composter, you may be wondering if oyster shells would be suitable for your garden. Can you compost oyster shells?

Oyster shells can be successfully composted after being cleaned and sanitized and must be ground or pulverized before being composted. While oyster shells add valuable calcium to compost, it is crucial not to add any raw or cooked shellfish meat to your compost pile.

Keep reading to learn more about how to compost oyster shells, the simplest way to prepare oyster shells for the compost heap, and the benefits that these shells can offer your garden.

Table of Contents

Can I Add Oyster Shells to My Compost?

Oyster shells make an excellent addition to compost heaps. They are natural, rich in minerals and complex compounds, and are great for your soil and growing plant life.

However, oyster shells are also incredibly tough. After all, they must protect a living oyster from predators, endure battering from waves and rocks in the ocean, and stand up to the force of hurricanes to protect their host.

As a result, whole oyster shells can take years to break down in a compost heap and must be ground up to a powder or beaten into tiny fragments to benefit a garden. So, where can you find oyster shells for your compost heap?

Where Can I Obtain Oyster Shells for Composting?

For many people, the simplest way to obtain oyster shells is to purchase and eat the oysters and make use of their empty shells afterward. Gardeners with a shellfish allergy or whose diets do not allow oysters to be eaten can find ways to get oyster shells into their garden, too.

A local fish market may have discarded oyster shells that you can use, and if you live near a fishing village, many fishermen are willing to give away or sell their oyster shells to you.

Discarded oyster shell fragments may also be gathered for free from a beach, though be aware that some localities prohibit or limit shell gathering, as these shells are a valuable part of the ecosystem and help build up shore composition and reefs. Always obey the laws and do not gather oyster shells if it is illegal to do so.

Now that you have your oyster shells, what should you do next, and how can you grind them for use in compost?

How Do I Grind Oyster Shells?

Oyster shells can be ground or crushed at home using a few simple materials. You’ll need

A pot with boiling water
Metal scraping implement (like a dull knife) to remove oyster meat
Tongs

Gardening gloves for safe handling
Plastic zipping sandwich bags
A towel

A hammer
(Optional) Stone mortar and pestle

Boil your oyster shells for 10 minutes if they have not already been boiled. Make sure to scrape away any remaining meat or tissue from the insides of the shells with a metal knife or tool. Remove your oyster shells from the boiling water with your tongs and let them cool down.

Put your gardening gloves on. Broken or crushed oyster shells can still be very sharp and may hurt your hands or cut you if handled without durable cloth gloves.

Next, place them in your zipping sandwich bag in a single layer, and cover them with a towel. The towel will prevent injury from any shards that may develop and will keep your hands safe.

Move your towel-covered bag to a solid, durable surface that can take a beating. Now, pound away with the hammer. It may take a while to break down your oyster shells, so be patient. Next, grind the fragments with a stone mortar and pestle to bring your oyster shells to an even finer, powder-like consistency.

The final product should be either fragmented like tiny bits of glass or fine like sand. It is also possible to break down oyster shells using heavy machinery for a simpler job and more uniform shell grain.

Machines Can Grind Oyster Shells for Composting, Too

If this entire by-hand process seems like a bit of a pain, you can use industrial machinery to grind oyster shells into fine powder in seconds. These machines tend to be expensive, but if you’re looking to crush oyster shells as a business or for your large commercial farm, investing in such a machine may be worth the money.

Alternatively, a local miner, fisherman, or farmer may have such a machine, and for a fee, they may be willing to crush your oyster shells for you. This will get you a consistent and fine grain of crushed oyster shells and allow it to break down beautifully in your compost heap.

Be sure to spread your oyster shells out evenly and distribute them throughout your heap for maximum benefits. So what profit do oyster shells add to compost?

What Are the Benefits of Adding Oyster Shells to Compost?

Oyster shells are a tough and mineral-rich substance. They help protect the living oyster within from the ravages of waves, wind, rocks, and seagulls that batter the oyster about. They’re also natural and are completely safe to add to the soil.

Use oyster shells for

Calcium deposits
Bulk in your compost pile
Powdered oyster shells can absorb moisture and reduce odor

Oyster shells can improve compost oxidation

Oyster shells can help your compost heap retain valuable nitrogen as well. As decaying plant matter breaks up, nitrogen is slowly lost, and the maximum benefits of this element fade. But oyster shells can help a compost heap retain nitrogen, making it more nutritious in the long run, giving you healthier compost and feeding your garden for a longer time.

Oyster shells are rich in calcium and are, essentially, the equivalent of the exoskeleton of the mollusk within. Plant life loves calcium, which can help plants grow stronger and resist temperature flux, disease, and drought.

As the oyster shell breaks down, that calcium finds its way back into the soil, building up a rich supply of minerals and helping adjust the soil’s pH level. So, will your soil become more acidic or alkaline if you add oyster shells?

Will Oyster Shells Make Compost Acidic or Alkaline?

As oyster shells break down, they add calcium carbonate to the compost, resulting in a more alkaline compost with a higher soil pH.

This can be beneficial for moderating the pH level of your soil, making slightly acidic soil a bit more neutral and thus accommodating a wider variety of plant life.

While some plants thrive in acidic soil, most prefer a more neutral pH level. Adding oyster shells allows your garden to welcome more plant varieties and maintain a healthy balance between the acidity of other compost materials (such as coffee grounds or orange peels) and the nature of your native soil.

How about oyster meat? Is it possible to throw in some oyster meat or flesh along with your shells?

Oyster Meat Should Not Be Composted

Oyster meat, like any kind of meat, is harmful to compost. It will also smell terrible as it decomposes and believe me when I say that few things are as putrid as rotting oyster flesh. If you thought your compost heap was a bit smelly before, it’d be nearly unapproachable with rotting shellfish.

Oyster flesh, like any meat, tends to break down a bit slower than plant material and will not adjust well to a compost heap full of vegetable peels, eggshells, and dead leaves. While eggshells as an animal by-product can be safely composed and will enrich your compost, meat is not the same thing, will decay at a different rate, and can disrupt the nutritional composition of your heap.

Rotting meat also attracts unique colonies of bacteria, which can harm your garden and kill sensitive plant life. Finally, you’ll also want to avoid adding oyster flesh to your compost as it can attract unwanted guests.

Will Oyster Meat Attract Animals to Compost?

Yep, it sure will. Scavengers such as rats, raccoons, weasels, coyotes, feral cats and dogs, and foxes can be attracted to rotting oyster meat in a compost heap and root through it. So make sure you scrape all the meat and tissue from your oyster shells before composting them.

If these animals become used to coming to your yard for food, they can become bolder and harder to scare away. Once a predator no longer fears humans, they’re difficult, if not impossible, to be rid of and may become dangerous to pets and humans.

These are the kinds of animals you probably don’t want around, especially not medium-sized predators. If you’re a homesteader raising poultry, these predators can eat eggs, kill chicks, and kill grown chickens, too.

Do Chickens Like Oyster Shells?

If you do happen to be raising chickens, oyster shells can benefit them, as well. Oyster shells, when ground into a fine powder, can add valuable calcium to a chicken’s diet and are a much healthier and safer alternative to dietary poultry lime.

You can save money on dietary lime and feed your hens something natural and beneficial. This is especially true if your hens are being raised for eggs, as a calcium-rich diet in hens is linked to bigger and higher-quality eggs.

This added calcium can also help a chicken’s immune system, improve bone density in older hens, and improve heart health. This may help your laying hens better resist disease and improve their longevity and quality of life, too.

Oyster shells for hens can be prepared by baking, drying, and then splintering or crushing them. Hens can eat small fragments as well as fine powder and won’t be endangered by medium-sized flakes of the shell.

The same powder can be used in turkey feed, cattle feed, pig feed, and goat feed to boost calcium levels. Apart from a supplement within livestock feed, what other uses do oyster shells have around the home?

Other Uses for Oyster Shells

So, what else can you do with crushed oyster shells around your home or garden? Oyster shells can be an excellent substitute for gravel on a driveway. We’ve seen many driveways on Cape Cod that use this same material in place of gravel, asphalt, or concrete.

Old oyster shells can also do the job of mulch and help retain water in a garden’s soil while breaking down and nourishing the garden over time. Oyster shells that have been ground to a very fine powder can also be added to wild bird seed for extra nutrition and to help birds grind their food in their gizzards.

Oyster shells can also take the place of lime in industrial and agricultural contexts and are quite a bit safer for humans to touch and breathe in than lime.

In larger projects, oyster shells have been used to help regrow wild oyster reefs, in turn protecting the shore from the full impact of storms as well as providing a place for wild shells and fish to live safely.

Conclusion

You can successfully compost oyster shells once they’ve been ground, crushed, or broken up into tiny flakes. You can do this by hand using a hammer or a mortar and pestle or by crushing the oyster shells with an industrial machine.

Oyster shells can be obtained by eating oysters or from your local fish market, wharf, or from seashore if permitted by law.

Oyster shells add beneficial calcium to compost and can help decaying vegetable matter retain nitrogen over a longer time. However, make sure to remove all oyster flesh and meat from the shells, as this can attract predators to your yard.

Chickens also love oyster shells. Ground oyster shells can help add calcium to a chicken’s regular diet. Oyster shells can also replace gravel driveways and mulch in gardens and can help scientists regrow oyster reefs in the wild.

Sources

Was this article helpful?

YesNo