In this part of the country, we eat a lot of shellfish. It’s great stuff, and easy to find (even if it is getting a little expensive as more people in the world discover it). The question is what to do with the shells after dinner?
I had thought the answer was simple because the mantra we heard growing up was always “If it comes from the ocean, it can go back there!” I recall tossing some used lobster shells into the cove near our property and watching an amazing number of little creatures appear from all around and instantly attack them for the tiny morsels still left there.
In fact, the answer is not that simple for several reasons. First, because we don’t always eat the stuff next to the ocean. Second, large piles in one place, like the shell middens of old, are now recognized as not the best thing to do to a shoreline or wetland. Third, it’s argued that there are differences in the bacteria and other pathogens carried by shellfish and that these can differ widely within a relatively short distance along the shoreline. Conceivably, introducing these bacteria to a new area could have unpredictable results, although I would think that would mostly apply to shellfish eaten raw. The same argument holds for the bacteria and that might be introduced by the humans eating the shellfish and passing the bacteria onto the shells we then throw away.
The shells of sea creatures are mainly composed of calcium carbonate, which decomposes fairly slowly in nature, and they tend to not decompose at all in large piles, such as a landfill (or a midden).
To some responsible reporters, that, and the bacterial issues make the shells incompatible with the collection of organic waste for composting. The stuff doesn’t decompose, they suggest, and the end result, if it did decompose, is not good for the soil. Those folks advocate putting the shells into the trash bin.
The other side says just the opposite. They argue that composting gives the shells the best conditions for breaking down, especially if you crush them a bit first, and that the end result is good for the soil, not bad.
In Brunswick, Garbage To Garden picks up organics from the curb, so I asked them, and they tell me the shells are definitely compostable within their system, and provide important minerals to the compost, so they’re happy to take them.
An interesting argument in favor of putting the shells back into the water is they can absorb some of the excess acidification while they break down there, and that sounds reasonable if the shells are scattered about. That would also serve to increase, however slightly, the amount of calcium in the water for other creatures to use in shell construction. The argument continues, however, to suggest that the shells need to be dried out for a period of time first, and can only then be safely returned to the water. As noted above, I would think that more especially applies to shells whose contents were eaten raw, not cooked, but I am very much not prepared to discount the possible problems.
We should lastly consider the upcyling of the shells. There is a company, for example, on Cape Cod that collects shells (they especially like oyster shells), then reuses them for walkways and driveways, or dries them and paints the insides for use as ornaments, wreaths, or other decorations.
The Recycle Bin is a weekly column on what to recycle, what not to recycle, and why, in Brunswick. The public is encouraged to submit questions by email to brunsrecycleinfo@gmail.com. Harry Hopcroft is a member of the Brunswick Recycling and Sustainability Committee. This column is a product of his own research.
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