Can You Compost Lobster Shells?

When I was younger, I spent some time in Maryland and would have crab feasts every summer. Shellfish like crabs and lobsters can be expensive, but in certain places during specific times of the year, crustaceans can be affordable. If you happen to host a lobster feast at your home, you might end up with an abundance of lobster shells. 

I knew shellfish shells can be used to make stock and to flavor other dishes, but I had already had my fill of seafood for the time being. I wanted to dump the shells in one quick go but didn’t want to just throw them in the trash. I got to thinking, can lobster shells go in the compost pile?

Can Lobster Shells Be Composted?

Lobster shells in compost bins are fine and can be composted with grass clippings and other yard waste to help them break down faster. Lobster shell compost will be high in calcium and carbon and may also have high levels of salt. For rich compost and boosted plant growth, make sure to add other kitchen scraps to speed up the composting process. 

Lobster shells should not be thrown directly in the garden or on the compost pile. Large pieces of lobster shells take a very long time to break down, even when surrounded with fast-decomposing materials like grass clippings. Calcium carbonate is a key ingredient in plant growth, but it needs to be broken down first.

How Does Lobster Shell Benefit Compost?

Compost Lobster Shells

Lobster shell aids the composting process in a number of ways, including building organic matter and adding fertilizer for plants. Calcium is a key plant nutrient, and lobster and crab shells have plenty of it, but it needs to be broken down to finished compost before plants can use it. 

Lobster compost also releases chitin. This is a compound that helps the compost heap retain moisture and repels harmful insects. Adding lobster compost with the rest of your kitchen scraps and a couple of inches of soil can help build your compost heap quickly.

Plants that Benefit from Extra Calcium

Some plants need extra fertilizer than what is naturally generated or supplied for a garden. Certain kinds of trees, vegetables, tubers, and legumes need an extra helping of calcium to grow even better. Without calcium available in the soil, plants will not be able to build strong cell walls or produce the fruit we eat. 

Fruit TreesExtra NutrientsMore Fruit
VegetablesExtra CalciumBigger Vegetables
ConifersExtra NutrientsStronger Root
LegumesExtra CalciumMore Beans
NightshadesExtra CalciumHealthier Fruit

Fruit Trees

Trees can be amended readily with lobster shells. Like eggshells, crustacean parts can be sprinkled underneath perennials. The calcium in the shells will break down slowly over time, releasing the nutrients over many years. Unwashed shells could contain high levels of salt or a smell that attracts pests. Both are bad for compost heaps.

Breaking lobster shells down into organic plant food with a boost of calcium for fruit-bearing and edible plants is a better way to help your trees. Outdoor compost pits with the right compost materials can get hot. Increased compost heat and high levels of moisture will break lobster shells down quickly.


Calcium works best when it is added to the soil before planting and at the root zone. Cruciferous veggies like broccoli and cabbage need an additional calcium supplement to support their large crowns and heads. The increased calcium content should be available for the mature plant’s roots deep in the soil. 

Lobster shells with chitin will also help to repel harmful pests from eating vegetables. The natural pest defense mechanisms in plants are strengthened by lots of calcium and help plants survive pests all the way until harvest. Garden plants benefit most from well-broken down and powdered lobster shells.


Pine trees like the extra calcium found in lobster shells. Placing lobster compost mixed with pine needles and other organic materials under conifers can help them grow stronger and straighter. Large trees need strong cell walls to transport fluid throughout the trunks from root to crown.

For maximum calcium potential, lobster compost should be added at the time the tree is planted and then mixed into compost and added every year. By constantly supplying much-needed calcium, pine trees can grow even stronger and weather harsh winters and blistering summers even better. 


These helpful plants are known to put tons of nitrogen back into the soil. This can be helpful when preparing a garden for big leafy vegetables. Unfortunately, legumes feed heavily on the calcium in the soil and can leave it depleted. Planting vegetables in nitrogen-rich but calcium-empty soil might not work out the way you hope. 

Add lobster compost when you plant and after you harvest legumes to replenish the soil. Any plants grown after the legumes will have the added benefit of nitrogen and calcium-enriched soil. These are the perfect conditions for tomatoes to thrive. 


Tomatoes and eggplants are some of the most common nightshade vegetables we eat. The leaves and stems are toxic, but the fruits are delicious and culinary staples around the world. These vegetables need huge amounts of calcium to grow correctly.

Tomatoes suffer from a condition called blossom end rot. As the fruits start to develop, a tomato plant can’t grow as fast as the fruit. The bottom splits and invariably becomes infected. This infection can quickly spread and makes tomatoes inedible. Adding lobster shell compost when you plant nightshades will completely eliminate blossom end root. 

How to Prepare Lobster Shells for Compost?

If you throw the lobster shells directly from your plate into the compost pile, it probably won’t work out very well. Most lobster shells will be high in salt, which can affect the microbes in your compost pile. Some shells may still have flesh attached, and as it rots, they will put out an odor.

If pests smell the rotting lobster, they will dig it out of the pile, make a mess, and interrupt the composting process. To make sure none of that happens, lobster shells should be properly prepared. First, the shells should be washed and dried.

Breaking the shells into small pieces or grinding them into powder once they are dried is the best way to add them to the compost. If you want to add some moisture retention and build soil structure, then you can smash the pieces and add them with eggshells and other slow decomposers to the compost pile.

Other Uses for Lobster Shells

If you don’t have compost or any plants that need additional calcium, you can think of some other uses for lobster shells. A few of my favorites are for stock and for golf balls.  You can also use lobster shells to make seafood seasoning.

If you are making stock with your lobster shells, crush them and submerge them in water. Boil the water briefly and let the shells simmer for several hours. Once the seafood flavor has been extracted from the shells, you can strain the liquid and dispose of the shells. 

When making seasoning, you can clean and dry the shells. Once the lobster shells are clean, you can grind them into a powder. This seasoning can be mixed with other seafood flavors to create a seasoning for shellfish dishes. Mix it with sea salt and use it on shrimp with lots of butter for an exceptional flavor.

Cruise ships and resorts allow golfers to hit balls into the ocean. Unfortunately, traditional golf balls are not biodegradable and pollute the ocean. Lobster shells can be broken up, shaped into a ball, and held together with biodegradable glue to make an ocean-friendly golf ball. These balls can be hit into the ocean guilt-free, breaking down into natural ocean material in only 3 weeks.