Can You Compost Mussel Shells? (And Are They Biodegradable?)

Despite earth being the only habitable planet, so far, that can house humans and other living things, the planet is about 71% water. And even for all this water, 96.5% of it is held by oceans with the rest existing as water vapor, in lakes, rivers, aquifers, as soil moisture, in glaciers and icecaps. This water is home to fish and other vertebrates, sea worms, crabs, lobsters, slugs, clams, starfish, mollusks and many other species.

Some of these molluscs from freshwater and saltwater habitats have their outer layer covered with a shell. The common mussel shells can be found in several species on all coasts, as long as there is a suitable underground present. The shells offer support for soft tissue, protection from predators and protection against desiccation for the invertebrate, while humans tend to use them for decoration or as fertilizer.

Are Mussel Shells Compostable?

Yes, mussel shells can be composted and used in the garden. When used in the garden, the shells enrich the soil and can help you grow healthy and productive plants. The exoskeleton of these mussels along with those of other crabs, shrimp, lobsters, crayfish and other insects, contains a substance called chitin, which is a slow-release of nitrogen needed by plants, and viable inside the composting bin.

Additionally, when the shells are added to the soil, composted or not, they stimulate and increase populations of chitin-devouring bacteria and fungi. Once these have decomposed the shells, they go on to devour certain chitinous pests, most notably root-knot nematodes, which can lead to poor yields in several crops.

The shells are also a valuable source of calcium carbonate, the key ingredient in garden lime. The shells of mussels, clams and oysters are rich in calcium, another essential element for plant health, that raises the pH of soils in areas that are too acidic.

When it comes to composting mussel shells, the prevailing advice is to hot compost them. This is largely because they might contain remains of meat on them, which will then attract vermin and pests. Hot composting them will result in compost, but will not have the pests lurking around.

You should therefore clean or rinse them thoroughly after using them and before composting them. You also need to crush them into smaller pieces, the logic being that they will compost quite easily and quickly as they will be fully exposed to the composting process.

As such, use a large rock or any other large object that you can use to crush the shells and do it until they are as tiny as gravel. Next, you will need to add a couple of layers of carbon content, like dry leaves, coffee grounds, twigs or sawdust, among many others.

Also add a layer of nitrogen-rich materials like fresh grass clippings, vegetable and fruit scraps or manure. Build your compost, water it like twice a week and turn it after every few days.

Are Mussel Shells Biodegradable?

Oh yes! Mussel shells are biodegradable, explaining why they are compostable. For a substance or object to be biodegradable, it means it can be decomposed by bacteria or other living organisms, thereby avoiding pollution.

The chitin in the exoskeleton is a slow-release source of nitrogen. Because of this, it does not leach out of the soil, meaning it does not pollute waterways the way other soluble nitrogen fertilizers do. Once the shells are crushed into a fine powder, they are added to the compost where the conditions allow bacteria and other microorganisms to work on the shells, breaking them down into compost.

Even if the shells are added whole, they will still disintegrate, although this will take quite a long time. it is therefore advisable to crush them before composting them. The fact that they can decompose naturally into fine compost that is valuable to the soil and crops means they are biodegradable.

How Long Does It Take For Mussel Shells to Decompose?

Mussel shells can fully decompose in just a few weeks or a few months. The duration is determined by their state when they are entering the composting bin. If the shells were crushed before being composted, they can take a few weeks before they fully decompose. However, if they were added whole without being crushed, they can take months.

Additionally, if they are added to a compost that is not aerated, watered or hot enough, they will take longer. If you put them in hot compost, they decompose even more quickly. The shells also release some nitrogen to the composting bin, meaning they are part of the green materials. This means you can add them in large numbers, provided they are crushed first.

Unlike other browns that absorb the moisture, mussel shells have no problem with the water or moisture inside the composting bin. The calcium in the mussel shell does not break down as rapidly as other crustaceans do, but this is not too much of an issue. With the right conditions, they will decompose quite easily within a few weeks or months.

Are Mussel Shells Good for Plants?

Absolutely! Mussel shells, first, by being compostable, means they are a positive addition to the compost and subsequently the soil and the plants. Secondly, they contain various nutrients that are necessary for proper plant growth and development.

For instance, they contain calcium carbonate, the key ingredient in lime. Lime is necessary to neutralize or raise the pH of an area, especially if it is overly acidic. the shells with therefore work on the pH of your soil, making it suitable for plants that do not like acidic soils.

The mussel shells also contain calcium, an essential element for plant health. The primary function of calcium in plant growth is to provide structural support to cell walls. Calcium also serves as a secondary messenger when plants are physically or biochemically stressed.

The exoskeletons of mussels alongside other insects, crayfish, crabs, lobsters and fish, contain a substance called chitin. Chitin is a slow-release source of nitrogen, equally valuable to plants. Chitin is the second most abundant polysaccharide, after cellulose, and is rich in nitrogen, calcium, magnesium and other vital minerals required for healthy microbial activity.

When released in the soil, chitin increases the availability of nitrogen to soil microbes and plants. Additional nitrogen to plants helps with forming chlorophyll, the agent used by plants to use sunlight energy and feed the plant. The other mineral and elements are also vital for various aspects of plant health, including flowering, root health and resilience.

Moreover, when mussel shells are added to the soil, they stimulate and increase populations of chitin-devouring bacteria and fungi. If the devouring pests, most notably root-knot nematodes, are not combated, the crops will produce poor yields. Mussel shells are therefore very valuable to the soil and plants.

7+ Amazing Ways To Reuse Mussel Shells

1. Making compost

You can compost mussel shells and have their properties added to your garden. The shells contain calcium carbonate that gives plants a boost. It also neutralizes overly acidic soils, making it easier to grow some plants that do not like the acidic soils. The shells are also rich in calcium, a necessary ingredient to the proper growth and development of plants.

Additionally, the shells contain a substance called chitin, which slowly releases nitrogen to the compost and plants. When the shells are added to the soil, they also stimulate and increase populations of chitin-devouring bacteria and fungi. This ensures the crops produce a rich yield after every harvest.

All you need to do is clean the shells, crush them into a fine powder and add them to the composting bin. You also need to add some nitrogen- and carbon-rich materials for proper compost. All these benefits provided by the shells will be available in the compost and will aid in positive yields every time.

2. Making seafood broth

There is plenty of tastiness in mussel shells alongside other shells such as those from oysters, clams, lobsters, crabs and shrimp. You only need to add aromatics, herbs and water, and simmer for a few hours.

Before you know it, you will have the perfect stock for risottos and soups. In fact, seafood broth is equally delightful and tasty like chicken, beef and veggie stock, but is much less popular.

3. Making a soap dish

You can always a new way to repurpose the beautiful shells from mussels and other sea invertebrates. For instance, you can use them to grace your kitchen sink, shower or bathroom sink as they make a perfect soap dish. They might not be big enough but if you manage to get the big shells, they will work perfectly for a standard-size bar of soap.

4. Making a salt bowl

There is a reason why seafood and salt go hand in hand and one cannot think of one without thinking of the other. Mussel shells are perfect as your salt dish. You only need to clean them and you will be placing your salt in and on them pretty soon.

They can come in handy at your next barbecue event and you need some salt as you prepare the meals for your family and friends

5. Holding jewelry

Imagine repurposing mussel shells to store your lady’s jewelry. They are excellent for holding her earrings and rings and will be a cute way of doing it. shells make a perfect bowl for holding jewelry and other household items including keys and are a beautiful addition to your house.

You can also think outside the box and use them as jewelry, rather than holding it. You can clean and sterilize them and then drill a small hole with a craft drill and make a pendant

6. Presenting food

It might be an old-fashioned trait but it still serves the purpose for those who hold it dearly. Yes, you can use mussel shells for presenting foods and serving appetizers. You definitely have to clean the shells before the first use and of course after each subsequent use.

7. Beautifying flower pots

You can also use the shells to beautify your flower pots. All you need to do is attach them to the flower pots and you will really dress up your spring and summer flowers. It will also present your house in a much more beautiful and creative way

8. Making a shell wreath

This is another creative idea, that you can do with your kids. You can make a wreath out of shells and hang it on your door or use it to surround a glass candle lamp on the picnic table.

You will need to clean the shells first, and also incorporate some hot glue. Place the glued shells around the entire flat wreath, fitting the shells together like a puzzle. The wreath will come to gather in no time at all and can be used year-round.


Share on:

About Rinkesh

A true environmentalist by heart ❤️. Founded Conserve Energy Future with the sole motto of providing helpful information related to our rapidly depleting environment. Unless you strongly believe in Elon Musk‘s idea of making Mars as another habitable planet, do remember that there really is no 'Planet B' in this whole universe.