Half Barrel Method?

Hi: I'm interested in making biochar in my 1/4 acre. After looking at various design, it looks like the cone pit / trench method will work best, but I don't have the room to dig a large trench. I'm wondering if anyone has tried this approach that Edible Acres on YT (https://www.youtube.com/watch?v=lOSDwp20EKM) used: Take a used metal drum and cut it open, and use it as an "above ground" trench. Add material as it burns and drench out the fire at the end, just like the cone pit or trench method.

Thoughts? I'd love to hear your advice!

Hi w and welcome to permies! This looks like a workable contraption, as low-tech pyrolysis vessels go. From what I saw skimming through the videos, the overhanging lip resulting from the smaller cutout helps create a sort of toroidal vortex like you would get with a kontiki or conical pit. And the end product looks to be a decent quality char.

One thing I have noticed with smaller containers is that you lose a lot of process heat from the high surface area:volume ratio. I have counteracted this by wrapping ceramic fiber blanket around the vessel to keep the heat in and develop higher temperatures throughout the duration of the burn. But that's me tinkering and shouldn't be necessary if you're using dry feedstock and tending the fire properly.

Try it out and report back. We're always curious around here.

I would love to have a barrel that could take really high heat.  Possibly stainless steel would be able to handle the temperatures but it's so expensive.  I would love to make an insulated system that pipes the wood gas back under the barrel and into the fire.  The more wood gas that came off the system, the hotter the fire, and then more wood gas, and then hotter fire...  I think I could make a super efficient system that would only use enough wood on the exterior of the barrel to get the wood gas started, and then it should continue the process on it's own, just using the gas coming from inside the barrel.

Regardless, i saw that video on Edible Acres as well as it seems like a great way to make pretty large batches with little waste.  I haven't tried it yet, but I'm anxious to see your setup and the results you get from it.

I love that channel, and that method.
I am making char in trenches at the house, but digging at at our grow yard is very difficult.

I aim to turn a water heater into a similar retort.
It will be longer and narrower,allowing for linger peices.
It's also plumbed for easy quenching.

I use this process almost exactly and love it. It is ideal for processing large quantities of branch material, and the char produced is great quality and plentiful for the effort involved. It is a little less efficient than a retort for conversion rates, but not as bad as I initially expected. I can process a batch start to finish in about 3 hours, including quenching. Fuel is added regularly through the process to keep a continuous flame front over the coals, to stop them burning away to ash.

I love how simple and portable it is - I can literally pick up the whole drum and carry it to where the fuel is.

Thanks for all the comment. Great to hear the positive results using this method.

One tip I heard from other places is that to avoid large amount of steam (which may cause concerns to my nextdoor neighbors) is to add water from the bottom up, rather than douse it from the top.

Yes I know the drum won't last but that's ok. I just need to get rid of a large batch and don't expect I'll have too much to do on an ongoing basis.