Mike Farmer

Good stuff! Looking forward to your updates!

It's a great point about using materials other than logs. Stick, wood chips, and other woody biomass that you wouldn't traditionally turn in the wood stove all would be great inputs here.

You can even make char with other hard-to-dispose of things like bones, avocado pits, nut shells, and the like. I've even experimented with making char from invasives like Japanese knotweed.

Neven Curlin wrote:
I've made an image to show the 'smolder' standing upright (see attachment). The bottom half is where the to-be-charred material goes, and then the upper half slides over it.

As you can see, the side sheets extend past the bottom, so there would be some room between the bottom and the grate. The grate is at the bottom of the fire box, so a lot of ash falls through into a small container that can be removed when the grate is lifted. It's also where the air comes from (via a duct to the exterior of the house), so maybe it wouldn't be wise to drill a hole at the bottom of the 'smolder'. Maybe better at the sides, so the oxygen is consumed by the fire outside of the 'smolder'.

As it is, without holes, I think the gasses would come out where I've added the red arrow. I don't know enough about retorts as of yet, to judge whether that's fine, or whether it would be better to have holes at the top or bottom (sides).

Thank you for the additional diagram. Based on what you shared, I would agree that the gasses should off-gas from where the overlap of the top and that should work well without an extra "base".

I hear you on durability. It really depends on how cheap the other options are and how long they last. For example, food cans might be free, but only last a few burns. An empty metal paint can may cost way less than the smolder, but won't last as long. It's a balance and really "user's choice".

Whatever method you go with, please report back on how it went if you get a chance! The more sharing we can all do of our experiences making char, the better!

Neven Curlin wrote:If there are still people around who have experience with making biochar in a wood stove, I would like to ask what you think of this stainless steel 'charcoal smolder':

Would this work in a wood stove to make biochar? And also, to fit my wood stove (see attachment), it would have to stand upright. Would that work, or would it be better to drill holes somewhere (at the bottom?). It seems gases can escape through the slits between the two parts.

My 2 cents is that the device shown would likely work in a wood stove to make char assuming it fits inside the fire box. If it had to stand vertically in your wood stove, you might want to put it in upside down so the gasses come out at the bottom? Maybe standing on a small fire brick so the hole doesn't get blocked by ash? That way you'd be sure the gasses would have time to ignite before going up the chimney.

All that being said...that charcoal maker feels like massive overkill. It's 99 Euros, which is no small investment. You can easily do something with cheaper materials like Sean's use of hotel pans shown just above. I've also had good luck with clean metal paint cans with a couple of holes punched. Several other YouTubers have videos of making biochar with reused metal food cans (small or #10) with a crimping tool.

Those may be worth exploring as they're much cheaper, only take a little DIY, and free up that 99 Euro to spend elsewhere!

I wouldn't feel safe that 100% of the undesirable stuff would off-gas or burn off in the process.

If I had a bunch of extra briquettes around, I'd probably use them to fuel the retort to char some known clean inputs.

I was back at the farm today planting some hops rhizomes around the chicken composter, and dug around a bit in the compost to expose some worms for the chickens. The little piles of biochar I had dumped in a week before had completely mixed in by the chickens...in less than a week you'd never know the piles were there. Pretty cool.

The plan is to harvest a bunch of the compost (and inoculated char) in a few weeks and put it on some garden beds.

I've read this before and it's interesting if you're producing at scale in a controlled environment, with uniform inputs. You can adjust for whatever your particular situation and goals require.

For us folks doing it at the backyard or farm level, I suspect we're getting a bit of the "best of both worlds" with varying feed stocks, sizes, and temps, we're getting some "now" biochar and some "later" biochar, maybe with a little mineral-rich ash mixed in. The imperfect process may just make the perfect biochar mix.

The "fluffing up" must reposition things in a way that makes additional passes more effective. Makes sense that after driving over a bag of biochar it gets "mushed" together in a way that more pressure just doesn't help. Moving around the pieces creates nice fresh edges and angles for more crushing.

John Suavecito wrote:That sounds very efficient in an unusual sort of way!

John S
PDX OR

Yes, the "harvesting" was really quick. The 10-12 buckets probably took me maybe 30 min of going back and forth between water source, fire pit, and chicken run in a little circle.

I'm sure this mixed a bit more ash in than many other methods, but up here in the northeast our soil is very acidic so getting it into the mix will help even out the soil a bit, while adding plenty minerals.

I was at a local non-profit farm where I'm on the board today doing some odds and ends. I knew their fire pit was a bit full of char, so was planning to clean it out. Folks had put more wood and sticks in there, and it's been damp lately. I started a fire to clean it out, but it was obvious that if I was going to burn through the residual char I'd be there a while.

So, instead, I found a metal bucket and filled it with water. I scooped out hot char and quenched it. Once it was cold out and fully saturated, I repeated the process. Probably did about 10-12 of those small metal buckets full to get the char in the fire pit down to a reasonable level.

The wet char then got added to the compost chicken dome to get charged in advance of the compost harvest in about a month. The compost/char will get worked into garden beds across the property.

As I was wrapping up, it started to rain pretty hard, so I  felt extra safe adding the char to the chicken system since everything was going to continue to get a good soaking at least through tomorrow AM.

Maybe a non-traditional way of making char, but it worked and stacked functions in that it cleaned up one area to soak up nutrients in another (chicken compost system) to eventually share those nutrients with a third space (garden beds)

Yes, lots of methods is the way.

Making lots of biochar is better than making a little biochar, but making a little biochar is better than making none.

Making a little biochar every day doing something you do anyway (like running a wood stove) is great!