Josiah Hunt has been doing commericial biochar longer than just about anyone. He is perhaps the finest example we have of small scale, low tech biochar entrepreneurship. Being in Hawaii helps - he has abundant feedstock, abundant need (poor tropical soils subject to leaching rainfall) and an educated public of permacultural farmers who get it. But despite the advantages of location, it was Josiah's genius that drove him to invent an economically sound biochar production method that allowed him to actually start a business. Not only that, his method is pretty clean, unlike traditional charcoal pits that smolder wood for many days and emit methane and carbon monoxide. In the open pit method, these gases are burned off so there is very little smoke.
Josiah uses a pit. No metal cone required. His method of gradually adding new wood over glowing coals is exactly the same method as the cone kiln. One difference is, he quenches with dirt instead of with water. Here is the link to his description of the method, with pictures:
He has since moved on to better, even cleaner biochar production methods, but for those just getting started, you might want to consider the pit.
Josiah - thank you for sharing!