Make Biochar in a Burn Pit

Ready to enrich your soil naturally? Try making your very own light and powdery biochar in a burn pit with this easy tutorial.

Photo by Cody Gantz

A burn pit is simply a conical hole in the ground. The conical shape pulls air up from the narrow point in the bottom of the hole, evacuating oxygen from the feedstock. Free access to air at the top allows the fire to burn the gases being released from the pyrolyzing feedstock below. This helps keep down smoke and noxious gases by burning them off, but it’s less effective than making biochar in a TLUD.

1. Test Your Soil Drainage

If you’d like to build a permanent burn pit for making biochar, you’ll first need to determine how well your soil drains water; if you have clay soil that holds water, you may end up with a stagnant swamp over time. To test your drainage, perform a perc test: Dig a small 1-foot-deep hole in the ground and fill it with water from the hose. After it drains, fill it again. This second filling should have completely drained out within an hour. If it does, then your soil percolates well and your fire pit won’t fill up with rainwater. If it doesn’t drain within an hour, consider building a cooker instead.

If you want to make biochar in a pit, you need soil that drains relatively well. Photo by Cody Gantz

Make a Burn Pile on Bare Ground

Rather than dig a pit, you could, instead, build the burn pile on the bare ground, which is easier than digging into the earth. However, the biochar won’t be as high in quality because the feedstock will be exposed to a lot of air. Not only that, but just as you would for a fire pit, you need your local fire department’s permission for open burns on bare ground. Sparks can float away and set nearby brush on fire. Open burns can produced a lot of smoke. If you must burn on open bare ground, follow the safety rules mentioned previously and keep your piles small - just 3 or 4 feet square, made of very dry wood stacked in layers set at 90-degree angles to each other, no more than 3 feet high. Keep it small and douse the wood when it’s reduced to red coals.

2. Dig the Pit

The burn pit should be conical, with the point facing downward. Dig the fire pit so it’s about 3 feet in diameter, with sides that slope toward the deepest point in the center, about 3 feet deep. Remember, you don’t have to dig it all at once! Take a few days if you need to.

4/16/2020 12:33:54 PM

I was going to ask same thing, I tried to make biochar pit but just dug a horizontal trench filled with kindling, brush weeds etc it seemed to work.

Mary W
4/16/2020 9:03:27 AM

What is feedstock - can't find where you explained that anywhere. Looks like lumber pieces?



Learn from Home!

Survival Skills, Garden Planning, Seed Saving, Food Preservation, Natural Health – Dozens of courses, 100+ workshops, and interactive Q&As.


Become a Preferred Subscriber and start enjoying the benefits today!

Fall in love with the flavor, versatility, and beauty of Mother Earth Gardener

Mother Earth GardenerDelight your taste buds, mind and eyes with beautiful photos and inspirational techniques on everything you need to know to grow, preserve and cook your own heirloom fruits and vegetables. You won’t want to miss the stories about plants passed down from generation to generation.

Don’t miss a single issue of Mother Earth Gardener. Published by the editors of MOTHER EARTH NEWS, Mother Earth Gardener provides decades of organic gardening experience from the most trusted voices in the field. Join today and save off the newsstand price! Get one year (4 issues) for only $24.95! (USA only)

Facebook Pinterest Instagram YouTube