There is some confusion between the terms charcoal and biochar.
The term BIOCHAR comes from Peter Read and refers to charcoal used to improve soil. Here is my article on Biochar
The purpose of biochar is agricultural. Any larger chunks are usually crushed before being added to soil.
Charcoal is exactly the same material as biochar except it is usually intended as a material to burn, such as for cooking or firing forges. There is nothing to stop you from taking so called biochar and burning it, or taking charcoal and crushing it to put in your garden. Don't use reshaped briquettes, they are not pure charcoal and would add other stuff as well as charcoal.
How I make Charcoal
I've tried several methods of making biochar/charcoal and they have all had pros and cons. Using the special stove means that charcoal is a by product of cooking. The charcoal is the leftover and can be re used for heat, to sell, or added to garden to improve soil. Making charcoal in a pit works well but you need a big space to make a pit.
I now make charcoal in my fireplace and have found this is the simplest method of all. It's controlled and quite safe. I don't have to babysit the fire, I just make it as I warm the shop.
After I launch my boat, I plan to try melting and casting aluminium. I've been collecting tins and bits of scrap and I have made enough hardwood charcoal to run a few experiments.
Making Charcoal in the Fireplace
Charcoal is simply wood that has been allowed to burn in a very low oxygen athmosphere. The woodgas is given off and burns but a lot of carbon is left over as charcoal. This is allowed to cool and this is the charcoal.
Here I am using a large cookie tin with several holes made in the lid using a large nail.
This batch is going to go into the garden to help improve it so I'm using sawdust. If you use sawdust use only wood dust, not plywood or particle board. You don't want to run the chance of adding poisons to your soil.
Charcoal can be made from many materials including chunks of wood and branches, trimmings from pruning trees, dried leaves or pine cones and bark.
This particular tin was not very strong and warped when I put it in the fire. I wired it shut before putting it in the fireplace and this worked very well. Some of the tins are very thin and burn out quickly. The large round tin was good for about 15 firings.
Around Christmas time a lot of cookies come in metal tins and that is where mine came from.
I make a fire in the shop to warm it in winter and after the shop is warm I let the fire burn down and put my cookie tin full of bits of wood and sawdust into the fire. The fire is actually quite low but exposure is tricky when photographing bright objects.
I have an ash shovel that I use to put the tin in and remove it from the fire.
I have a woodstove in the shop and this works very well. You could also do this in an open fire outside or in a fireplace. Just be careful.
Within a few minutes small flames start appearing at the holes in the lid. This is the woodgas being produced and burning as it comes out.
When I'm burning sawdust the woodgas and flames are only present for about 15 minutes. When I'm burning chunks of hardwood there can be flames for an hour.
When the flames have all died out it is safe to remove the cookie tin. Place it on a couple of bricks on a flameproof surface. It will be hot. It needs to cool without being opened. If you open it while it is hot, there is a chance the charcoal will start burning. You will know that is happening if you see some glowing coals in the tin or white ash on the charcoal, or if your tin stays hot.
I often just leave the tin to cool in the fire at the end of the day and empty it the next morning.
BE CAREFUL. Don't leave it un attended or where kids or pets can get to it. Have some water handy and an extinguisher.
Once the tin feels cool to the touch you can open it and remove the charcoal. I have a metal bucket where I put the charcoal. I use metal just in case I missed some hot spot and it starts burning. Larger chunks of wood, bark and pine cones also make charcoal.
I like the sawdust charcoal because it mixes very easily in the soil without having to be crushed.
If you're careful, this is a quite safe easy way of making charcoal. I keep the large chunks in a old grain sack and I'm planning to try melting aluminium in another experiment so I've made enough for this.
The sawdust charcoal goes in plastic buckets to be dug into the garden when the snow melts.
email me: Christine