Biochar with two-barrel nested retort

[cvrnut09]

whats the normal duration time of the burn usually?

[jveazebeaze]

Where do you find free or cheap 55 gallon barrels?

[cdalehendricks1101]

Yes, you got it right. The smaller holes in the inner barrel are placed so that when the volatile gas's leave the retort (inner barrel) they are right near the primary air- this enables the heat to further drive the process.

[rockrebell]

Did I get this right - the INNER barrel is turned upside down into the OUTER barrel, so the holes match the airintake of the outer barrel?

Is that to use the woodgas for the process too, or does it have another reason?

[hillbournesian]

That is very nice. I saw then built a smaller scale version without the chimney on the Terra Preta forum of hypography. Mine was a 55gal barrel sawed in half, and a metal 5 gallon bucket. I just turn it upside down inside the half barrel. The chimney idea is great though. I'll be sure to incorporate one in my next burn. :-)

[cdalehendricks1101]

Yes I bet you'll be amazed at how effective a chimney is. Fun too, Dale

[Buddebud]

Very cool must see this for myself.