You know that charcoal and biochar is not the same thing, right?
These items have been discussed over at the soil forum into the minute details.

"I am making them homemade biochar out of clam and scallop shell."
I am curious as to what exactly you are making. I have lots of scallop shells and wonder how to use them in a worm bin.

It is my understanding that biochar is charcoal made for the express purpose of putting into or under the soil. Where as charcoal is made to burn or filter, biochar is valued for it's nooks and crannys for wee beasties.

http://www.youtube.com/watch?v=RXMUmby8PpU&feature=related

MAKING BIOCHAR: with Peter Hirst of New England Biochar

Here he explained the difference between Charcoal and Biochar and since you are planning to make your own Biochar, you might be interested in watching this video.

The inside of the young coconut has like a pudding or yogurt consistance inside for humans to eat after drinking the healthy, refreshing, similar to gatorade, water. The inside looks just like the inside of a huge egg shell. I think the worms are going to love it. I will put it in empty. Like the guy who put the thick paper tube into the bin to harvest just castings, I think inside the shell will end up with just castings too. This may be a two year project. I do not expect the shell to ever breakdown in the bin. Worse than a mango seed.

Hi cathyca,

I too am curious as to what exactly I am making.

The shell I used because like you, "I have lots of scallop (and quahog) shells and wonder how to use them in a worm bin." Native Americans of course created huge mounds or middens of shells. I guess even back then people had many more shells than they could make good use of.

I would use them in the garden around plants as a mulch or path but they always end up broke and sharp and ugly forever. Archaeological sites often have bone and shell in the fire pit. I had chared some bone and it looked like it had lovely micro structure when crushed to add to the bin and ultimately to the garden. I can remember reading only a bit about charring shell. So I'm not the first person. I can hear sbryce now saying it is a mineral just like egg shell not organic. I can't really argue with that fact. I think the heat breaks down the material in to smaller pieces of... mineral. Maybe the plants have better access to it. At the very least I was hoping it would act a bit like pottery in terra preta by providing different sized habitats for wee beasties than plant char.

I was surprised the thin scallop shells seem much tougher than thick quahog shells do to a little bit of heat.

When I fire pottery on shells, the shells make a glaze on the pottery surrounding the shell, and the shell will come out of the kiln looking normal, but the least bit of humidity will make it heat and turn to powder. I have wondered why, but never have taken the time to look up what makes it do this. The heat from the turning-to-powder-shell is hot enough to burn my hand if I am not careful, so I have to immediately put the used shells into a glass bowl and either cover them to keep them dry, or wet them to get them to finish turning to powder.

A month ago I put a young coconut into the bin. These are white and chopped open to get the clear liquid inside to drink. The outside material has now turned into the familiar brown coir color. I was easily able to peel off the one inch thick coat of it. This left a very thin hollow shell. The worms did not seem interested in the inside of the shell. I will not put it back in the bin. It has given up all of its goodness. I may char it as coconut char is highly prized. The outside the worms love. It is a thick mat of wetness. Held in the hand it does not drip. Squeeze and one can see tons of water was being held. This can be a retreat for the worms if the bin gets to dry. I expect this material will cycle through the bin a few times before seperating and disapearing. I intend to add more of these unique items. They were fun. I think it is the same as what is purchased in bricks dry.

antoniab, what you are making in your kiln is quick lime. Keep it out of your eyes It can badly burn until it is slaked with water.
When I was in the Seabees we ran out of lime for a project on a Pacific island and had to burn shells and coral to make our own.