Mussels are one of the cheaper seafood options and can liven up any pasta or seafood soup being prepared for dinner. Only the soft inside of mollusks are eaten, and the shells of mussels remain even after the rest of the meal has been digested. If mussel shells are biodegradable, should they be thrown away in the trash or tossed into a compost pile to break down?
Will Mussel Shells Decompose in a Compost Pile?
Shells of mussels will break down in a compost pile organically through the natural soil and bacterial microbes. The hard membrane of common mussel shells makes them slow to decay in garden beds and cold compost heaps. Composting mussel shells is effective, and the calcium carbonate inside is the key ingredient in garden lime, a useful soil additive.
Crab shells, shrimp, and other uneaten portions of a seafood dinner are a great source of calcium, an essential element for the development of cell walls and plant growth. While they shouldn’t be thrown directly on garden beds, they can be worked into the soil using the trench method to help fertilize plants for many seasons. Composting mussel shells work best in a hot compost pile or when the shells are dried and ground to a powder.
How to Use Mussels and Other Shellfish Shells in the Garden
Shells from mussels and other shellfish shells can be used throughout our lawns and gardens. It is important to make sure that when you are using the shells, they are clean and free of meat pieces, or you may attract unwanted pests. It is also possible that shellfish that has not been prepared correctly for soil and compost use will have a bad odor causing additional problems in your yard.
| Use | Benefit | Process |
| Nitrogen-Rich Materials | Soluble nitrogen fertilizer for long-term productive plants | Add mussel shell compost or mussel shell powder to your soil for rapid plant growth |
| Alkaline Soil Amendment | Turns acidic soil neutral by raising the pH and releasing soil-locked nutrients | Adding an alkaline-rich soil amendment can help most plants thrive in a better soil environment since acidic soil builds up over time |
| Improves Drainage | Seafood shells have a role in soil structure and prevent clumps of soil from collapsing and compacting | Crush shellfish waste into gravel size chunks then bury them under several inches of soil in gardens, compost piles, flower pots, and potted plants |
| Adds Plant Micronutrients | Micronutrients are an element for plant health that are found in green materials, fruit scraps, coffee grounds, and nut shells | Shellfish shells ground up and buried under several inches of soil will increase the nutrient content of the area and make garden soil fertile |
| High Calcium Mineral Content | Leftover shellfish have plenty of calcium which is needed for healthy plant growth | Add mussel shells to the holes where plants will be planted to give deeper roots better access to calcium deposits |
| Kills Slugs and Snails | The exoskeletons of mussels can be used to stop soft-bodied pests from entering your garden | Clean and crush shells from mussels and place them around plants and areas of the garden vulnerable to pest infestation |
Plant Health
The greatest advantage of composting mussel shells rather than tossing them in the trash is the boost to your overall plant health. The sea has many micronutrients that plants need to thrive, and it is available in a form that is easily absorbable by roots. All of these trace elements combine to give you stronger plants and also make your edible vegetables and fruits even more scrumptious.
Calcium is a macronutrient that all plants need. While it is just below the NPK hierarchy on fertilizer packs, it is a nutrient in plants that is very noticeable when it is lacking. Cell wall development is an energy-intensive plant growth process, and the calcium supplied by seafood shells goes a long way in providing all your growing plants will need.
Nitrogen is the most important nutrient you want to be abundant in your garden soil. The slow release of nitrogen into your garden bed for months to years will help give generations of garden plants the boosts they need to grow big and strong. Sprinkling crushed mussel shells and watering them into potted plants or garden plots can give your plants a rapid boost of nitrogen right when they need it most.
Soil Additives
Some plants need certain soil conditions to thrive. Based on our location, we may not have the best natural soil for the garden plants we desire. It can be expensive to buy all-new soil to grow your plants, but it is possible to slowly change the composition of the soil your plants will be planted in. Mussel shells biodegradable properties can drastically raise soil pH over time.
Soil can easily become compacted and break down in structure. When this happens, plant roots have a hard time getting oxygen and can rot or die. Adding mussel shells to garden soil and mixing it well can build pockets that keep the soil loose and porous. This is especially effective in potted plants and raised beds where you have the most control over soil structure.
Other Benefits
Shellfish shells that have been cleaned and crushed can be powerful apply in keeping slimy pests away from your plants. Slugs and snails like to come out at night and dine on your garden plants, but the sharp edges of crushed mussel shells will make them retreat in a hurry. Make sure the shells are free of meat, or it could have the opposite effect and bring larger pests that could dig up your garden and destroy even more of your plants.
Can You Compost Uneaten Shellfish?
It is not advisable to compost uneaten shellfish for the same reasons that dairy and meat are avoided. The meat will stink and attract pests as it rots. Even if it is buried deeply, most predators can easily smell through the ground and will dig up seafood in a flash. You can compost uneaten shellfish, but you may want to prepare it first to avoid unpleasant compost situations.
Cooking the seafood first, even if it is just boiling it and then tossing it, will help combat some of the stenches. It will also make shells and other hard components softer and reduce overall composting time. Try to crush or cut up large pieces of uneaten shellfish and mix them thoroughly into the pile with other composting materials.
Making hot compost and adding uneaten shellfish to a mature heap is also a great option. You will need to layer green materials and brown materials to get the right ingredients for a hot pile. Add the seafood to the middle of the pile and add water and mix every couple of days. The more you turn it, the hotter it gets, and the faster the food will become compost for your plants.