Nice biochar kiln. I may make one at some point, but the pit method works pretty well too. I'm not too worried about getting less biochar, wood is abundant here. This was a quick and easy approach. I still have a large amount of char. If I wasn't burning wood that was 7-10 feet in length, I would have tried a dryer drum set on the ground to plug the holes. It works as a great burn barrel when off the ground. I like to build things out of pallets and bedframes, so when I have a pile of scraps this burns it up fast.

I have a lot of green & brown waste too. The simple kiln is incredible at burning through it all. Very minimal smoke even when burning green leaves. The size allows you to add whole branches and logs without spending hours chopping into smaller peices. It's a brilliant design (also not mine).

Tip: It's easier to reduce the ash and maximize the charcoal if you build a simple kiln for your fire.

I've built a few & settled on an open kiln made out of corrugated iron. I've found just getting charcoal in the ground to be super beneficial. My priorities are getting the most charcoal with as minimal time/effort as possible. I've no shortage of branches & debris to burn here. Basically cut 5 or 6 lengths of corrugated iron about 1.2m long. Bolt then together top and bottom with some overlap, making sure 1 side is even (it will be sitting on this end). You need it to be about 4.5m long because you'll fold it up into a 1m² square. Wire some old star pickets to the top to provide structural support & you're done.