Mistakes you've made in biochar

I was just thinking that since biochar is a pretty new thing to Western modern culture, it might be useful for us to share some mistakes that we have made so that others can avoid those problems.

I'll start.  At first, I was going to make a brick tower around my 55 gallon metal drum, full of wood, so that it would be a large retort.  I would then build the brick tower over it each time.  What I didn't realize is that I have to burn my biochar in the driveway, in an enclosed fire, so that I don't create a fire in my yard during our hot dry summer weather.  That means that I would have to haul and build a brick tower over my metal drum each time.  Way too much extra work.  I had to give away the bricks.

Another mistake I made was packing my wood into the 55 gallon drum tightly in the spring or winter before I burned the wood.  It was tidy and it made the area look more cleaned up, but the wood never dried.  Burning wet wood makes lots of smoke and not much biochar, and sometimes I couldn't burn it at all.  

Another mistake I made was burning the biochar during the morning to warm me up. The problem is that often the wood and the air are much more filled with humidity at that time.  Often, nothing has dried out enough to make a really good fire, making lots of smoke and less char. Now I burn here in the afternoon, when everything has dried out a bit.  It may be different in your climate.  

Another mistake I made was letting the fire go on to long, so I ended up with lots of ash and not as much wood.  I figured I shouldn't have any unburned wood at all, and I have since learned that when I have a small quantity of unburned wood, I have the maximum amount of char and less ash, so it's optimal. I just burn the small unburned quantity during the next biochar burn.

I would love to hear from others about mistakes you've made so that we can help each other to avoid problems and create more successful biochar.

John S
PDX OR

I just thought of another mistake I made. I would just gather any wood I could find and burn it.  Then I realized that wood that was aged enough would smoke significantly less than green wood and give me more biochar.  So I started making piles from about the same time that I cut or gathered the wood.  Then if I wanted the wood to be at least, say, 9 months old, I would go to that area and collect the wood.  Another one is that sometimes, even if it was aged enough to not be green, it could get rained on in the few days before I burned it, so I take enough wood for a burn and leave it in a covered area for that week or so before the burn to make sure it stays dry and burns efficiently.

JOhn S
PDX OR

Since I started collecting the crushed biochar weekly for inoculation, I keep drenching it every day until it's done.  I usually wait two weeks.  At the beginning, I didn't have any way to really distinguish the one week old crushed biochar from the two week inoculated stuff.  One time  I accidentally put out the stuff that had been inoculated for only one day, and left the stuff that was already inoculated for yet another week.  After that, I put two different colored lids on the inoculating biochar.  Because I had yellow and gray lids, I use the yellow for the first week.  Yellow is like the morning sun, so it's the new, first week stuff.    I use the gray for the second week.  Like gray hair= old.  I make a big deal out of digging in the two week old  biochar into the garden and the "graduation" of the new biochar to the veteran biochar and changing the colors of the lids.  I haven't made that mistake again.

John S
PDX OR

I made a very novice mistake. I made charcoal and scattered it around without inoculating it with anything. So it's probably been a sink, draining nutrients for a while now... I suppose it will eventually pay back in dividends, but inoculating it first would have avoided that misstep.

Sort of an intentional mistake: I used to burn huge piles of brush and then extinguish them with the hose to scavenge the char. It is pretty effective as long as you constantly add brush to the top, actually. But once I dug a trench and did it that way I was getting a much better input/output ratio. The reason I was burning was for fire clearance so I wasn't going to be able to burn all that in a trench anyways but I can assure you that it's worth it if your main goal is to collect the char.

The fire suppression angle has really become important out here in the West, so it's a good area of discussion.

I don't have acreage, so I'll never be able to do that, but I am interested in if people who use the trench method have found ways to inoculate their biochar.  I know for some, it's mostly a long term, climate change carbon sequestration issue, but I would love to hear about it.  I just have a suburban garden, so I use a 55 gallon drum as the oven TLUD and inoculate in 5 gallon buckets.
John S
PDX OR

I sawed up a tree and I decided I would burn the branches in a pit to make biochar.      It was great I piled on and piled on branches and the charcoal was piling up.    except the heat was so intense that the leaves were being picked up and landed on my insect netting burning holes in it from about 6 feet away.        Slow and steady far better than fast furious and starting more fires.

When I first started adding the inoculants to the raw char, I added them, mostly powders,  first. Then I added the liquids and the char.  Then I stirred the whole thing.

After inoculation, which for me is mostly drenching the 5 gallon buckets once a day, I got ready to dig the inoculated biochar into my garden soil.  At the bottom of the bucket, I noticed a horrible smell and a solid block of white powder: ag lime.  The ingredients really hadn't mixed when adding, nor during the whole inoculation process.

Now I add all the inoculants, then add all of the liquids (mostly urine in my case), but no char at all,  then stir thoroughly.  It turns into a chunky, gray thick liquid, but it is completely mixed before I add any char.  Result: no bad smells and no heavy blocks of any one substance. Everything is well mixed now.

John S
PDX OR

In my case it's just a small trench so I dig the char out into buckets and inoculate that way. I am only making 7-8 buckets (about 35 gallons) of char at a time. I am going to get my neighbor to  dig me a full size trench when I clear my lower property (about 3 acres) and try to get serious with it.

Anyways, another mistake I have made was trying to crush it by hand, in a square container, with one of those packer-wacker tools. Hand tamp? The results were not much better than running it over with my truck and it took forever. The truck, even on dirt, allows for more production. I have a lot of nasty land to rehab here! Really this is a scale issue and not a mistake. If you are making just a few gallons then the truck would be ridiculous but when doing it by hand, I almost gave up. Which would be the ultimate mistake.

I think my biggest biochar mistake was simply over-complicating it.  I agonized over every detail, studied every method, basically had analysis-paralysis to the point that it took me forever just to start making charcoal.  It just isn't that hard.  People made something amazing long before anyone ever heard of a retort, or logged temperatures, or had a perfect plan.  My advice to people new to this is to just start making charcoal.  This thread is proof you'll make mistakes.  Make them, and move on.  Like anything else, you learn from doing and you'll make mistakes, get better at this, make less mistakes, and so on.  

And use really dry wood :)

Seconding Trace here,

First, be safe.
Second, just do it.
Third, realize what you did wrong and do it better next time.

If you're unfamiliar, this is the iterative model of business. It applies to a lot of tasks in life.

Normally, I fill a 5 gallon bucket of biochar about every week that's been crushed in the driveway.  I start with just the char, and then inoculate it.  One of the things I add is rotten fruit. Since I have an orchard, I have a lot of that.  Normally, I'll add 5-8 fruit each week. Then when I have all of the other ingredients, I drench it once a day.   Last week, I had tons of pears. I added 20 rotten pears to the 5 gallon bucket.  Then I realized the problem: I couldn't drench it. The liquid wouldn't flow. It was like jello.  I decided that the only thing I can do is to stir it, which I have been doing every day.  The next time I inoculate it, I'll be going back to 5-8 fruit, no matter how much I have on hand.  The rest goes into the compost.  Sometimes, more isn't better. It's worse.  Sometimes, much worse.  

John S
PDX OR

Over complicating. I messed around with retorts and things, but my best results and easiest process have just been a trench in the ground and quenching with a hose. I can process a lot of volume in one burn, for minimal fuss, and produce great quality char. I see complex retorts now and scratch my head in puzzlement.

I have since made a "portable trench" but cutting an oil drum in half down it's length. I take it to where the fuel is, just carrying it by hand. Super easy.

I've tried repeatedly to turn white pine logs into char using a pit method.  They seem to go from log to ash without much of a coaling stage.  A retort might work, but barrel based retorts are too small and too labor intensive for my purposes.  And I don't want a huge retort taking up space on my property.  So I guess I will let most of the white pine logs rot and feed the soil that way.

Very interesting Gray.
I use a lot of pallet scrap in my char making.
I think most of it is white pine, perhaps the heat treatment changes how it pyrolizes?

@John Suavecito
Im guessing you dont have animals,  or at least not enough to keep up with the fruit?
Maybe you have the ingredients for making a wholr lot  of vinegar?
I only have few trees that fruit, but its enough that I'm considering setting up a barrel with crushed fruit and champagne yeast, followed by apple cider vinegar mother and an aerator.
The leftover pomace would probably be great compost material or even chicken feed, and the vinegar has so many uses.

@William Bronson. You are correct. My wife would love to have chickens, but we are specifically prohibited by the ccnrs.  We have composting red wriggler worms, but that doesn't count. With climate change, it's hard to tell when the season is anymore, so I can't tell if the apples and pears are unripe, ripe, or overripe until I check them out.  I think I'll throw most of it in the compost.

John S
PDX OR

Gray Henon wrote:I've tried repeatedly to turn white pine logs into char using a pit method.  They seem to go from log to ash without much of a coaling stage.  A retort might work, but barrel based retorts are too small and too labor intensive for my purposes.  And I don't want a huge retort taking up space on my property.  So I guess I will let most of the white pine logs rot and feed the soil that way.

Your problem sounds like it is that you are using logs. It takes a long LONG time for the middle of a log to get sufficiently hot to char nicely, and in most fire arrangements the outside is burning away to ash while you wait. If you want to use that material I suspect that you will need to split it down. I get best results if everything is 2" or less, but as long as most of the material is below that it will cope with an occasional piece that is 4".

Partially charred pieces are annoying because the don't break up nicely, so I usually just thrown them back in the bottom of the pit for the next burn.  Most of my biochar actually now spends a few months in the chicken pen, and they do a great job of both inoculating it and physically breaking down bigger pieces. I'm a little less fussy now compared to when I manually broke it down myself before using in the garden. The chickens don't care about unburned pieces.

If you don't want the labour of splitting those logs maybe look at hugelculture? Or can you save labour by splitting them in long lengths using a series of wedges, rather than cutting to short rounds?

Good point michael. I chop my wood up evenly.
John s
Pdx or

I have KNF pigpens. I have 8 8x8 pens. The pens are layers of biochar on the bottom, logs and stump ends in the middle, and lots of wood chips on top. It is a mix of oak, madrone, manzanita, and pine; some composted, some fresh.  The pens all have different amounts of biochar in them. I sourced the biochar because of the amount I needed, I think at that point I used about 12 yards. The pens that have at least 6" of biochar under the logs perform the best. Some pens have had way more biochar dumped on top but it breaks down with the chips and absorbs nutrients, but it doesn't regulate the moisture of the pens as well.

Back to the OP: the mistake I make too often is assuming the char is fully extinguished.

I often burn in the winter, when it's safe and I have time. I can't quench the char with liquid water -- I have none at hand (and anyway I want to soak it with stinky fermenty green juice later). You'd think that packing two feet of snow on top and stomping it tight to exclude oxygen would work. Nope, at -25C I have to check it, re-pack the snow and tamp out the hot spots for the next week.

I guess that's a safety note from hard experience. Assume nothing, or your char will become ash (or worse, spread fire).

I once did a pit burn and at the end I covered it with some of the dirt that came out of the hole. I thought a week would suffice to wait before I unearthed it. It was still warm, and as I shoveled deeper the coals in the center of the pit started glowing. Buckets of water solved that, but my advice to pit practitioners is now to wait 2 weeks minimum.

I want to make a couple of cubes without water quenching in order to have clean, dry material for insulation, so I'm getting a piece of stainless sheet cut in a circle to fit my big kontiki. I'll seal the edge with clay for airtightness and try to be patient.

Phil,
Great example, but I'm not sure what the cubes are or how they fit in. I don't live on a farm.  How does that work?
THanks,
John S
PDX OR

Cube = cubic meter

A while back, I made a TLUD biochar cooker with a gallon paint can, a sheetmetal chimney, and a sheetmetal outer shell. As I understood the TLUD designs, part of the idea is to draw air down an annular space between the inner fuel chamber and the outer shell - preheating the hair so it can perhaps start pyrolysis of the fuel even before the flame burns down to that fuel. And on the gallon-scale, this seemed to be working. At least the fuel in the paint can was all rendered to charcoal with pretty good efficiency (about 20% yield pound-for pound).

In late 2023, I built an up-sized version. I made a reduced size drum from a 55 gallon drum, put a bunch of holes in the bottom and made some short legs and placed it down in an open-top 55 gallon drum. The annular space is about one inch all around. A drum lid is modified with a central hole of 10-inch diameter and fitted with a three-foot tall, 10-inch diameter chimney of sheet metal.

This design DOES NOT WORK. Although I once had a very hot fire that burned right to the bottom, most of the time the fire will burn down about 1/3 or 1/2 of the barrel and then begin heavy smoking from the chimney. The flame quenches. I believe this is loss of updraft or perhaps there never was updraft and the fire was always being top-fed with air. Anyway, I cut some holes in the sides of the outer drum, in case air was being heated but then being less dense, could not displace the colder air in the bottom of the drum. But first holes at mid-height, and then holes right at the bottom of the outer drum did not solve the issue. So maybe the bottom of the fuel chamber is not adequately ventilated. It has 30 1/2-inch diameter holes, plus some other incidental gaps due to how it was constructed. I have put a grate in the bottom to keep wood and falling coals from blocking these air holes. This also is no help.

Of course I can simply discard the inner fuel chamber, and use the outer drum as a burn barrel. I can still put on the chimney - which is required by local fire protection ordinance. But I am perplexed by the poor function of the double-wall design. What is causing the quenching? Maybe it is the falling coals from the upper section burning that are blocking off the upflow air enough to stop the smokeless burn? I cannot "poke the fire" in this design so the coals fall where they like and remain there. I may try one more burn with the inner chamber - modifying it with a few intermediate-height air holes. But this will seem to render the whole point of a double wall design irrelevant. Others here have not tried double-wall burners much it seems, so maybe I am just wasting my time.

To burn a TLUD, it doesn't have to be a retort. Mine is not.  I decided not to do a retort with my 55 gallon TLUD because it didn't seem like I would get enough biochar production at the end.  

I wish I had a more direct answer to your question, but it's a great question and one that could help move someone from frustrated would be biochar maker to happy and successful biochar enthusiast.

John S
PDX OR

Cade, does this help at all? May not, but thought I would share in case it provides another idea to try.

https://urbanwormcompany.com/guide-biochar-101-introduction/
(scroll about half-way down, with the header of "Method 2: Top-Lift Updraft or TLUD")


credit: UrbanWormCompany

Great image and great article, R Dell!

John S
PDX OR

Not a mistake in production, but a mistake in handling.

Dry biochar fines are easily dispersed by stray winds. I did not appreciate this and ended up getting a face full of char dust when I bent over while transferred biochar from one container to another.

Inhalation should be avoided. 1/10 Experience.

Always evaluate risk before embarking on projects to try and minimize these kinds of mistakes is what I learned from this experience!

Initially, I used a narrow tube as my chimney. It was the only one that was available at the restore, so I used it. I just completely didn't know.  It wore out after a few years and I used a much wider one, like 10 " diameter instead of 5".  It worked so much better! I posted about this, but I know not everyone wants to dig back through years of threads.  I get more char, it burns better, and there is less smoke.  It is on a TLUD, using a 55 gallon barrel.

John S
PDX OR