Welcome to low-tech charcoal production. You can make an earthen kiln to produce Bio-Char. Using ground charcoal as a soil amendment is proving to increase yeilds and sequester carbon among long lists of other positive benefits. We should all be adding it to our gardens and compost as the ancient cultures of the Amazon did. In the areas of the rainforest where this was practiced, there are still several feet of topsoil, also known as Terra Preta.
Google it if you're interested to learn more.
Now, for the earthen building part, this diagram I created shows the basic layers and features of the kiln and the following photos show how we built one.
We even added a thermal probe to test the temperature fall-off of the kiln and to ensure the quality of our charcoal. In Thailand, charcoal is often used for cooking because it smokes less and also for water filtration. This is an extremely important product in developing countries.
There will be an article in Permaculture Activist soon with the results of this study.