Mayan biochar hugel kultur trench burn

This idea may be specific to my soil type (extreme clay). But I do think it combines the best that Mayan style terra preta biochar and hugle culture beds offer.

I’ve tried hugle culture beds at my place to little avail. We have extremely dry summers and the high mounds have been exposed to the drying winds as well as the heat. So I thought why not try a hugle culture bed in a more protected position that will hold water better. Like a trench. While im at it why not at my latest interest, biochar.

I’ve seen plenty of great ideas for making biochar. But most are small scale. And the large ones are extremely expensive. I’ve not seen development of old school Mayan style pit burns.

So I tested an idea the other day that combines rocket stove or heater concepts will Mayan biochar production.
The idea is too dig a trench. I’ll dig it 25cm wide with a back hoe. My first will be 30m long and about 60-90cm deep. I’ll loosely fill it with wood, trying to get roughly the same diameter. Then I’ll cover the top airtight. I’ll try to achieve this using thicker wood cross members chicken wire and soil/clay. Then cover the top with wet clay that will be pliable enough to fill the gaps.

My test so far showed me I needed a chimney to pull the air through and a constant fire at the chimney to burn the smoke from the main fire. It’s not needed to create Biochar, and the ancients probably wouldn’t have done it. But it will protect the environment and myself from nasty gases.

Ill create a wide chimney that is divided in half. regular chimney on one side. Rocket stove one the other.
Ill light the trench at the chimney. Then as the fire moves through trench away from the chimney, the flames will no longer reach fresh oxygen. This means the secondary burn will stop and smoke will pour out. But with a rocket stove constantly burning at the secondary oxygen mixing point, a clean burn could be achieved.

I believe with this system that oxygen wont need to be choked as much. Which means potentially a hotter, faster burn. And higher quality biochar. Once its done or close to done it would need to be quenched. Probably using a partial flooding of the bottom, collapse of the clay top and some top watering.

Biochar Trench

Biochar Trench

Then I want to add another idea. The BD500 is a biodynamic technique that requires a farmer to fill 500 cow horns with cow manure then bury them with the point facing toward the heavens. They swear buy it, claiming that earth energies have entered the horns etc. I think what’s really happening is; that its a perfect habitat for worms. Its got food, moisture and vitally oxygen. Having the horns turned point side up creates a cup of air impervious to rising water levels. And thus a perfect habitat for worms which breath through there skin. So in my trench I want to add to my biochar containers of manure, turned to face open side down.

Then ill layer manure, straw and food scraps to create a typical lasagne style no dig garden. And some great compost to plant into. Then some mulch to save some weeding and evaporation.

My clay lets virtually no water sink down and pass between particles. So I expect these trenches to fill with water in the winter. Plants will put up with wet feet for a few weeks. But if all oxygen in the water is depleted, the all important bacteria will change from aerobic to anaerobic and the plants will start to die. So I need to dig small culverts to allow some of the water to drain away. I think the plants will survive the wet months if a couple of inches of root mass is not submerged. The worm containers may help here too.

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