John Saltveit wrote:A pit makes too much smoke and doesn't burn the wood vertically, so it's not efficient.
John Saltveit wrote: A pit makes too much smoke and doesn't burn the wood vertically, so it's not efficient.
Greg Martin wrote:Looks like we were typing at the same time Michael! How much biochar volume can you produce in your trench at a time? I've been thinking of trying the trench geometry to allow for the use of longer wood and I'm wondering how large a single person can go before it's hard to manage the fire without losses. Thank you for sharing this!
John Saltveit wrote:
The tepee structure makes sense as it can make it more vertical, like a rocket mass heater, and thus more efficient. That is not what I've seen from most pits.
Michael Cox wrote:From personal experience I hate the tepee structure for fires in general. It seems nearly inevitable that the inner core burns out quickly, and drops away from the outer layers. The outer layers are self supporting, so don't drop down as the charring wood beneath collapses, so end up further from the combustion zone. Then you end up with a smokey fire, and more wood that burns away completely. I'm sure you can work around this - drier wood that chars faster would help, as would cutting to shorter lengths, and more careful management of loading - but it is much more work than simply laying whole stems horizontal along a trench.
Chris Kott wrote:That is literally and exactly what I suggested in my post above. Thanks for posting that, Jan.
Michael Cox wrote:Jan - That is a neat design for tidying up small diameter stuff. I visited a vineyard once where they burned the prunings. But they had made a funky fire-barrow - they had adapted a wheel barrow base with half an oil drum and long handles. They could wheel the drum down the rows while they were pruning and chuck the stems straight in to burn. It didn't catch char like yours, but it could have.