Re: Pit under stack of crop waste - Biochar from maize stalks


Don't know about you, but finding a windless day where we are is pretty hard, which has discouraging consequences for efficiency!

Regards "quenching," Kelpie suggests pouring out the char on the ground in a thin layer and letting it put itself out. I have not tried this and have no idea how much you might lose to the air.

One thought is to use a moisture meter to calculate the water content of your char. We found a good one on Alibaba for very little. We use it for pricing purposes, but you could use it to back calculate to dry weight.

General question: what are you charging your char with and how good is your soil? In my experience, the better the soil, the more char you need to accomplish anything, no matter how you charge. In the developing world, most of the soil is so bad that 250 grams plus manure, pee and either EM or a handful of forest dirt/litter will come close to doubling the yields of almost anything. (Response varies a lot among species.) Water retention and surface porosity are huge here, too, given clay soils that bake brick hard in the sun and then hold little water when it does penetrate. With climbing temps and more irregular rainfall, biochar is proving to be the poor person's only effective means of mitigating these two big consequences of climate change.


On Mon, Aug 2, 2021 at 7:20 AM Teel, Wayne <teelws@...> wrote:



You are correct on that.  Even in my batch retort I barely get 20% by weight.  I think you can only approach 30% in a continuous feed system where you use the heat from pyrolysis gasses to heat the new material.  I have to light a fire underneath the pyrolysis chamber and count the fuel used for that against my total yield.  On a low wind day, with very dry wood, I likely get above 15% in the Kontiki, but it is hard to measure since I use water to quench, and getting the biochar dry takes an oven since it holds water so well.  I am noticing the effect in my garden this year.  We are very dry this summer, but the biochar beds have a lot less wilt and I don’t have to water as often.




From: <> On Behalf Of d.michael.shafer@...
Sent: Sunday, August 1, 2021 5:56 PM
Subject: Re: [Biochar] Pit under stack of crop waste - Biochar from maize stalks


CAUTION: This email originated from outside of JMU. Do not click links or open attachments unless you recognize the sender and know the content is safe.



I would not complain about 15%. If I am not mistaken, the theoretical max is not much over 30% and both trench and trough pyrolysis are pretty inefficient.


I think that the key thing about Kevin's method is that he achieved his results using literally a hole in the ground. Again, if I am not mistaken, this is reaching way back to the origins of the process in E. Asia where the Japanese used a small pit.


The point is that for Africa, where no one can afford to buy or make a Kontiki, Kevin's method is efficient and effective.




On Sun, Aug 1, 2021 at 4:59 PM Teel, Wayne <teelws@...> wrote:



I have done it with hemp waste after seed harvest.  This was an experimental plot and was not repeated because of Covid.  I used a Kontiki kiln, filled it with stems and before the first addition was completely consumed I added more hemp stems, doing the entire amount I had in a single burn.  I did it alone, using just a shovel to break it down and water to quench.  The yield was good, but I estimate only about 15% of the mass was left.  Most of the biochar went to the raised beds of a local farmer to grow vegetables, and he does not hesitate to take it when I say I have more (mostly from branch wood rather than ag waste).  It is hard to see a large jump in yield on the farmer’s field because he has high quality soil to start with, but it is enough a benefit to be worthwhile.  I am in the Shenandoah Valley in Virginia




From: <> On Behalf Of K McLean
Sent: Sunday, August 1, 2021 4:31 PM
To:; Michael Shafer <d.michael.shafer@...>; Kelpie Wilson <kelpie@...>
Subject: [Biochar] Pit under stack of crop waste - Biochar from maize stalks


CAUTION: This email originated from outside of JMU. Do not click links or open attachments unless you recognize the sender and know the content is safe.

This may be a new way to make biochar from crop waste.  Our early testing with maize stalks has been very successful.


Dig a pit.  In the videos the pit is one meter in diameter and 1/2 meter deep

Stack maize straw above the pit.

Light on top and stir when necessary.


In Africa, when the fire goes out we usually smother the embers with dirt.  In the video, the embers were quenched with water.  Or, the embers could be spread in a thin layer to cool.


It's easy and fast.  Only a shovel is needed.  Smoke is minimal and we get a good amount of biochar.  Much better than open field burning.


Here are videos:


Has anyone done this and can share their experiences?


Can others test this with rice straw and other crop wastes?


Kevin McLean

Join to automatically receive all group messages.