Have been using the same technique with great results here in South Africa. Lowest imbeded energy method for sure. I think that bio-char holds so much potential to rehabilitate land that is effected by wild fires. In our area, once a fire has burnt through, huge amounts of partially burnt organic matter is stacked and burnt to ash to clear the material. In some cases decades of the biological output of the eco-system, in the form of organic matter is lost.