I have spent years hemming and hawing about the cleanest way to make biochar, in the meantime not having any since it seemed so complicated and all the metal kilns so expensive, and the small stoves so unproductive in terms of quantity...I have a small market garden. This year I followed the instructions on Turkeysong's blog linked to here in another thread, and just dug an oblong pit. It was amazing! I had a pit full of char in just a couple hours burning all the small diameter woody yard waste. It was quite forgiving, and all the small diameter stuff, like raspberry canes, was still there as char rather than as ash. Yes, there was smoke at the beginning, could have been a lot less if I had started with dry material, but all in all I feel a very reasonable compromise for the amount made and the low tech accessible nature of the process. Basically burning the yard waste, cut as I had taken it from the yard, no trimming, sooooo easy and fast.
I found this link to another pit method person, my pit is nowhere the size of his, more coffin size, and a couple feet deep.
Just start with a small fire and keep layering your material as he says, as the coals build so does the cleanliness of the burn. I mixed diameters near the end without seeing a problem, it all ended up as char except for the last pieces, larger diameter....he says to finish with small.
One thing, I quenched but not enough, ideally the pit needs perhaps to be flooded. The hose from the top did not penetrate very easily to the bottom of it
and it was smoking a little the morning after.
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Ed Sitko wrote:Looks like a great way t make a large quantity of biochar.
So what do you do with that much biochar?
My plan is to use it for urine collection first, then mix it with my worm compost, and spread it on the (very large) garden. I tried saving pee and it stunk soooo much! I read about people using char in a bucketcompost system, so hopefully this will be the golden missing link for that idea. It sounds so perfect, the acid urine should balance the high ph of the char, an issue for me here with a neutral to slightly alkaline soil. Charge the char, and not flushing fertilizer all the time. I hope this will help in water as well as nutrient retention. Plus, housing for as a diverse microbial population as possible.
Burra Maluca wrote:We have these two pits on a bit of land we bought, which are rumoured to be charcoal pits.
It's on the list of 'things to do one day' to try them out.
So easy! Just burning yard waste. Is there a water source nearby? Quenching with water seems like a much easier option than burying with soil.
I don't think you need much of a pit, not sure, the idea is to block the coals from side air drafts, so I guess that would depend on how much you burn per session.
Congrats on your pit full of char! I know it's a good feeling. I too have successfully made a lot of biochar using an earth pit kiln. It seems to me to be the lowest barrier to entry for making biochar on a homestead. I hear metal drums burn out after 10-20 burns so unless you're having a custom kiln made out of thick gauge steel like the kon tiki, I think an earth pit is the way to go. I wrote a detailed article on how to make biochar in an earthpit: Earth Pit Biochar
I hope that helps someone thinking about trying this method but not knowing where to start. For me it was like a wild goose chase finding all the info I needed.
"Every organism on earth is intimately and irrevocably connected to every other and to the nonliving elements of the planet. We unite with our environment to form communities and ecosystems, whether we know it or not." -Edible Forest Gardens Vol 1 pg 26