What’s one thing no one wants to think about during the height of a delicious seafood dinner? That ever growing pile of shells just waiting to stink up your apartment, or attract peckish wildlife who might get a little adventurous in your trash bin. You know it, we know it, no one wants to deal with it.

The discarded aftermath of a crab feast can sour that sweet, buttery taste real quick, and is one of the things that sadly deters potential consumers from choosing our favourite local crustacean more regularly. 

Discarded, not disappeared. Important distinction. 

The out of sight out of mind mentality isn’t one that ever increasingly aware seafood consumers are prescribing to. Consumers are more mindful than ever of food waste, whether in the form of single-use plastic packaging or unutilized biomass. So what, then, of the untold tonnes of crab shells going into landfills globally? While it might not fall into the category of plastic and other offensively non-biodegradable products, food waste is no less detrimental. 

But here’s the thing – there is a right way and a wrong way to manage the shell waste in order to see it make a productive return to the ecosystem, and some of them may surprise you! 

Here are our top Do’s and Don’ts of dealing with your shells to help send them back to support the natural world, and help you skip the stewing bag of room temperature seafood scrap in the process.  

Do’s for Dealing with Crab Shells

1. Do Make Crab Stock:
   • This is the classic go-to for giving your crab shells a second life. Boil the shells with aromatics to create a rich, flavorful stock that can be used in soups, stews, and sauces.
2. Do Compost the Shells:
   • Add well washed, dried, and crushed crab shells to your compost pile or city green waste bin. They enrich the compost with calcium and other minerals, benefiting the garden soil in the long run. If you don’t garden yourself, consider donating your crushed crab shells to local gardeners or community gardens. 
   • Tip: HUGE emphasis on wash, dry and crush those shells! Otherwise they’ll be attractive to all the wrong critters!
3. Do Create Natural Fertilizer:
   • Wash, dry and grind the shells into a fine powder and sprinkle it around your plants as a natural fertilizer. The nutrients in the shells help improve soil quality and support plant health. Read til the end of this blog for our Shell Fertilizer Recipe!
4. Do Make a Natural Cleaning Scrub:
   • Believe it or not, crushed crab shells can be used as an abrasive cleaning scrub. Mix finely crushed shells with a bit of baking soda and use it to scrub pots, pans, or even your sink. It’s an eco-friendly alternative to commercial scrubbing powders, and it adds a little seafood flair to your cleaning routine.

Don’ts for Dealing with Crab Shells

1. Don’t Dispose of Shells in Regular Trash:
   • Avoid throwing crab shells in your regular trash bin if at all possible. If you’re waiting for green bin pickup day, bag them and throw them in your freezer to avoid those dank odours. 
2. Don’t Flush Shells Down the Drain:
   • We wouldn’t have to say it if someone hadn’t done it… Don’t ever try to dispose of crab shells by flushing them down the sink or toilet. They can cause serious clogs in your plumbing, lead to costly repairs, and where will they end up? That’s right, landfill.
3. Don’t Burn the Shells:
   • Maybe if they’re just boiled in saltwater…maybe. But overall burning crab shells isn’t the most environmentally friendly or ecosystem effective way to dispose of shell. Plus they can release some weirdly unpleasant odours.
4. Don’t Return Cooked Shells to the Ocean:
   • Bet you didn’t think that was on the Don’t list! While it might seem like a natural choice to return crab shells to the ocean, it’s generally not recommended to do so after they’ve been cooked. 

This deserves a deeper dive. When a crab dies in nature, its shell is gradually decomposed by scavengers, bacteria, and fungi. This process releases valuable nutrients like calcium and nitrogen back into the environment, enriching the soil or seabed. The remaining shell fragments may become part of the sediment and provide temporary habitats for small marine organisms along the way. This decomposition process plays a vital role in maintaining ecosystem balance – but those shells weren’t cooked, buttered, or seasoned with Old Bay.

When cooked the chemical composition of the shell itself has been altered, which could affect how they break down in the ocean, and residual oils, seasonings, or other substances that it came in contact with could disrupt the marine environment. As well, many coastal areas have regulations against disposing of food waste, including shells, in the ocean that could inadvertently impact local marine life, either by introducing foreign materials or by altering the habitat.

So while this option seems to make the most sense, upon further exploration it’s probably best to help those nutrients find their way back into the ecosystem through other means!

Now you’re armed with the do’s and don’ts to help you handle your shell waste in a way that allows you to get the most out of your crab, and divert nutrient rich shell waste from the landfill and back to the ecosystem!

Need a kick start? Next time you’ve slayed a crab boil, try turning your shells into plant fuel with this nutrient packed crab shell fertilizer recipe!

Crab Shell Fertilizer Recipe

Ingredients:

• Cooked crab shells (rinsed and dried)
• A mortar and pestle, food processor, or hammer and cloth
• Garden gloves (optional)
• A large bowl or bucket

Instructions:

1. Prepare the Shells:
   • Start by thoroughly rinsing your cooked crab shells to remove any residual seasoning or oils. Allow them to air dry completely.
2. Crush the Shells:
   • Once the shells are dry, use a mortar and pestle, a food processor, or hammer on a hard surface to crush the shells into small pieces. If you can make it into a fine powder that’s even better!
3. Collect the Crushed Shells:
   • After crushing the shells, transfer them to a large bowl or bucket. The smaller and finer the pieces, the quicker they’ll break down and release nutrients in your garden soil.
4. Application:
   • Sprinkle the crushed crab shells directly onto your garden soil around the base of plants. For best results, lightly mix the shells into the top layer of the soil using a garden fork or your hands.
   • You can also add the crushed shells to your compost pile to enrich it with calcium and other trace minerals that will benefit your garden later.
5. Water the Soil:
   • After applying the crab shell fertilizer, water your plants as usual. The water will help the shells start to break down, releasing their nutrients into the soil over time.

Tips:

• Frequency: Apply crab shell fertilizer a few times a year to keep your soil enriched.
• Storage: If you have leftover crushed shells, store them in a dry, airtight container for future use.

Top up your soil every 4-6 months for a natural nutrient boost.

This project is supported by the BC Government’s Buy BC Partnership Program; delivered by MNP LLP with funding from the Government of British Columbia.