I was wondering if anyone has any tips for me. I have an ongoing supply of large amounts of mussel shells and some oyster and scallop shells. I would love to make use of them, or at the very least dispose of them in a nice way. So far I have considered crushing them up as a liming agent (here in western Scotland we have very very acid soil), but how to crush enormous amounts of shells small enough is beyond me. I also considered burning them, but I didn't know if that would turn the lime into a form that was bad for the soil.
Depending on how many you have and the relative garden space..... I use them whole in the garden for decoration, plant markers, water catchment and homes for beneficial insects, every new tree, bush and plant hole gets a bunch, in the bottom of potted plants they are great for aeration and drainage and my chickens enjoy eating them.
I still have a concern, (just like bringing in anything from "outside" the garden) do they introduce a negative effect. Most of our waters are contaminated and I would think such toxins would accumulate in the shell. I am curious if there is any truth to this theory. As far as breaking them up, I put them in my dirt drive way and run over them with my truck.
You don't Really need to break them up before you use them, just spread on some bare soil, and turn them in with a shovel, the shovel will break them down to smaller pieces. If you feel the need to break them down before use put them in a paper/cloth bag, Put on your boots, and crush them.
burning your own lime only really makes sense if you've got the wood or other fuel to spare. where I'm at, lime is pretty darn cheap to buy. learning to do things ourselves is good and important, but it isn't always the most affordable option. so this might not be the best use of limited time, money, and other resources.
that said, building a well-insulated and clean-burning kiln to burn your shells in would dramatically reduce the amount of fuel required and might be worth the time if you plan to do it a lot.
you could also try crushing them, leaching out the lime, and using the remaining keratin for the local university medical school.
the keratin is a blood coagulant, used in the new high tech bandages.
the keratin can also be dried, and used as a "scaffold" , to re-grow damaged digits. just moisten the end of damaged finger, and dip into the powder, and re-bandage. Repeat as often as the surface dries out. You need to keep it moist to re-grow.
Doc in California doing it now.
Here is a collagen design , think keratin works better for bone....
Some people use them for paths and driveways, another use is under grape vines and maybe fruittrees, they reflect light and assist with ripening.
Lime is fast acting, but in my experience needs to be applied every year, shells are a slower acting, but pretty much permanent source of calcium for your plants.
Another idea that I just thought of, and is theoretical at this stage. Use them in the same way that you would use a line of stones to diffuse sheet flow erosion. Or as a dryland mulch, and any other water harvesting feature that would normally use small stones or gravel.