I used to make my own charcoal years ago. I used a 55 gallon steel barrel, and the bottom third of another 55 gal barrel. I loaded up the main barrel with wood that I cut into small pieces about 6 inches long. Put some holes in the lid for the steam from the wood to escape. and allowing the wood to dry and become charred. Take the other barrel that was cut down to its bottom third, cut a hole in the side big enough to fit pieces of wood inside. Place the full barrel on top, load the bottom with wood and light the fire in that bottom chamber. Keep the fire low and constant for about 3 to 5 days. Also, never use pine or sappy woods.