Have seen the 55 gal method, but local codes don't permit barrel burning. So, scaled down size, used some shed scrap and SOB, it worked! Have an over abundance of mulberry ( 5 months cut/split seasoned) so why not make lump out of it. Had alot of small prunings and lumber cut offs to use for fuel, so they're now bio-char for the garden. Was about a three hour burn and twelve hour cool down. Old propane tank was cut and drilled on bottom for air, hunk of 6"x 10" smoke pipe and two cap's. Did smoke heavy while gassing off, so will build secondary (cleaner burn) chimney during the week. Only snapped pics at end but next time will show more of process. Really happy with results;