My first attempt failed miserably but I improved with subsequent attempts after seeing the technology in Africa. The single barrel was superseded by a double insulated one. The technique is quite simple in which I jam-pack the wands of olive clippings into the barrel. Normally the Catalonians burn all their waste in a pile, but this way I offset the need to get special permission to burn as well as being able to manufacture bio-char at any time in the year. I now have the technique quite well established. One of biochar's added qualities is that it absorbs moisture, and so around the roots of plants it will lock carbon into the soil as well as provide minerals and a pest deterrent. I cook with it everyday more or less. The high temperatures and flameless heat ensure that pans don´t get too black. The wood burner in the caravan can burn slowly all night on one load when ash is allowed to cushion the coals. It also prevents a high fire risk under the pine trees.