The commercial season for Dungeness crab opened on November 15. That's always a much anticipated event around here, we love crab, especially those big meaty Dungeness, and frankly, around here Dungeness crab is synonymous with crab, there are few other crabs worthy of our gastronomic attention. We've enjoyed four crab meals already thanks to the CSF (community supported fishery) that we belong to, two distributions of two 2-pound crabs. The crab is delivered cooked and cleaned but still in the shell. The only work required is to get out the picks and crackers and pluck the goodness. At the end of the meal there's just a bowlful of empty shells.
Ah, but what to do with those empty shells? Well, feed the garden, of course. The primary source of nitrogen that I put in my vegetable garden is crab or crustacean meal. I buy it in 35 pound bags, one of which will last at least a year. Crab meal, sulfate of potash, compost, and a mycorhizal innoculant are the typical amendments that I dig into the soil when I prepare a bed or a section of a bed for planting. Lately I've also been using a micro-nutrient amendment such as Azomite or glacial rock dust. Crab shells are a good source of nitrogen and phosphorus but contain little or no potassium, which means they have a NPK of (4-3-0), (N - nitrogen, P - phosphorus, K- potassium, the numbers you see on fertilizer packages in the US). Crab and crustacean meals are also good sources of calcium and magnesium. They are also reputed to help suppress nematode populations because the bacteria that break down the chitin in the crab shells produce an enzyme that weakens the shells of any nematode eggs that happen to be nearby and perhaps even the exoskeletons of adult nematodes. One more benefit to using crab meal is that it breaks down slowly which means I generally don't have to do any supplemental feeding other than for very long standing vegetables that produce for more than 6 months or so.
My sister used to collect her crab shells in the freezer and when she ran a load of garden trimmings through her chipper/shredder she would run the frozen shells through and compost them. I don't have room in my freezer to stash crab shells. So I've come up with an alternative and easier way to process the shells, I simply grind them up in my VitaMix blender. The first time I tried grinding the shells I just put the wet shells into the VitaMix and gave them a whirl. The mix came out a bit chunky but usable. Then I thought that it was going to get stinky if I didn't use it right away and since I didn't have a spot in the garden that needed amending I girded myself to stink up the kitchen a bit and dry them out. First I thought of using the dehydrator, nah, too messy. So I turned the oven on low - 200ºF (93ºC), spread the shells out on a parchment lined baking sheet and popped them in the oven for a bit. What a pleasant surprise it was when the kitchen didn't get stinky.
The next round of shells went into the oven before I ground them up. That worked so much better, still not stinky, neither in the oven or fully dried. It doesn't take very long to dry the shell enough to get a fine grind, 10 minutes at 200ºF and then turn the oven off and let them sit. Last night we had another crab so after dinner I popped the shells into the oven for 10 minutes and then turned the oven off and left them for the night, this morning they were perfectly dry and not stinky. No fuss and no stinky garbage the next day. Gotta love it, not only do I avert garbage from the landfill but I get to feed my vegetable garden too!
The photo below shows the wet ground and then dried shells on the left and the ground dried shells on the right. It's so much easier to dry the shells, collect them, and then do one big grind, like I do with my egg shells. I prefer the finer grind so I gave the dry chunky stuff another whirl and it ground up nice and fine.
Two crabs produced only 6.5 ounces (190g) of dried ground shells, so I'll still be purchasing those 35 pound bags of crab meal. We don't eat that much crab.