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How to Clean Oyster Shells for Compost

Sue Stepp

Garden soils need amendments that contain calcium for good plant growth. Shells of all kinds make excellent calcium amendments for soil. Adding egg shells or crushed oyster shells to compost improves the growth of many vegetables, and helps avoid brown rotten spots on the bottom of tomatoes.

Use old oyster shells to make rich compost for your garden.

Before adding oyster shells, they must be cleaned. Un-cleaned shells added to a compost heap can cause bad smells, insect infestations and excess salt that can kill plants. Once the shells are cleaned, all of these problems disappear and your compost turns into rich, beautiful soil.

  1. Place oysters in a sink filled with hot, soapy water. Let the oysters soak until the water is cool.

  2. Scrub the oysters with a hard brush, removing all dirt, meat and residue inside and outside the oyster. Drain the water, and rinse the shells thoroughly.

  3. Put on protective eye wear and rubber gloves. Plug the sink with the oysters in it, and turn on the hot water. Add 1 cap of bleach to the water. Fill the sink, and let the oysters soak until the water is cold.

  4. Drain the water, and rinse the oysters thoroughly. Plug the sink, and fill it with hot water. Let the shells soak until the water has cooled. Add liquid dish detergent to the water and scrub with the hard brush again. Make sure that all of the meat particles are off the oysters.

  5. Let the water out of the sink, and rinse the shells. Plug the sink, and fill it with hot water. Let the shells soak until the water cools. Put the shells on a thick towel, and let them dry.


Place a pillow case inside a second pillow case, and fill it with cleaned oyster shells. Tie the end of the pillow cases shut, and beat the shells with a hammer until the shells are small shards. Sprinkle thin layers of oyster shells between layers of grass clippings, vegetable waste from the kitchen, and manure for faster processing in the compost heap. Layering keeps the compost heap at a high temperature and ensures that insects stay out of the compost heap.