When propane neared $5 a gallon a few years back, Ed put an upsized TLUD in his window glass shop for heat. Same operating principles as this instructables of the month http://www.instructables.com/id/Durable-Biochar-Producing-TLUD-Camp-Stove/
Fuel for the heater is hardwood pellets, about $200 per ton. No brainer v $5 per gallon propane. The “residue” from heating the glass shop a few months with a TLUD was a couple 55 gallon barrels of pelletized charcoal.
Yes indeed, charcoal from hardwood pellets created in a TLUD is a beautiful fuel. We first built a Gary Gilmore simple-fire for home generator. This is just as simple as it looks and one-pull starts are fairly common.
Then we used charcoal power on a 1947 Case tractor powering a chunker. https://www.youtube.com/watch?v=fMxtBDYXiik
Ed even ran his Toyota pu on charcoal for a while. https://www.youtube.com/watch?v=O3NZynm6l7g
One take away is that only a tiny amount of ash residue remains after gasifying TLUD produced charcoal pellets for engine fuel.
Our next step is to make a “sprout chunker” to turn brush and twigs into heating fuel to remove dependence on pellets - and clean up around the farm.
And BTW, the TLUD’s made out of thin metal last for years if you keep them out of the weather. Have yet to wear one out that was running normally. Have burned a couple out quickly when reaching for forge temps on natural draft ;~)