Biochar Questions no one seems to answer?

After attending Nick Ferguson's class up in Michigan, I went home and made a few barrels of char. So, a few questions.

I have a one-acre farm with pigs, chickens, rabbits, and a produce operation. We just cleared mature trees off half the land and there's a lot of wood laying around. I'm running a single 55 gallon barrel burning brush and small sticks, and quenching it when full. The quality of the char has carried, but I'm getting better at managing the temperature and burn in the barrel.

My questions are, how long should I soak it to charge it and how strong a solution? Planning on trying both rabbit manure tea and just tossing it in the chicken coup to absorb manure. How do I know when it's full? How could I test the strength? Also, any idea how I could measure the pH?

I want to get up to around 5 percent char to my topsoil, so about 1/2 inch or about 4 cubic feet per 100 square feet. I guess one barrel full (about 36 cubic feet) should do about 900-1000 square feet of soil, which seems about as heavy as I would apply manure.

Great questions, Jordy. The answers could be complicated or simple, and you could go deep into reading scientific papers or go with your gut. My take: Establishing a functional population of beneficial fungi and bacteria in fresh biochar is probably a lot faster and easier than a lot of people make it out to be.

Remember that what we want to do is similar to broadcasting a seed mix on bare ground. Not all the seeds will germinate, and early in the process some species might dominate. Over time, the balance will shift according to what nature throws at it. If our biochar is a blank canvas, all we are doing is putting on the first broad brush strokes ahead of a longer-term masterpiece that will develop out of sight.

So, go ahead with what you're planning to do. Both drenching in manure tea and mixing with coop litter are good methods. I'd advise a relatively short soak, no longer than a week, so that nothing starts to go anaerobic. Adding an aerator or doing a daily bucket tip wouldn't be a bad idea either. The pH will decrease with time as soluble compounds from the ash leach out, and it will settle into the same range as the soil you add it to. At a target rate of 5% to your soil volume, it's not going to make any appreciable difference to your soil pH (and even if it did, it would be temporary as leaching and the buffering effect of carbonates from rainwater do their thing).

Your barrel burns are looking good. Have you tried angling the drum to change the airflow pattern?

I like the idea of soaking them with pond/aquarium water which is has alot of purple non-sulfur bacteria. Then you can just add some water kefir which is very acidic. Then you can just soak it for a week in compost.

Hi Jordy,
Congratulations on your set up. I haven't got very far with my biochar manufacture. Partly because I can't get myself organised to manufacture it on purpose and am still just raking out coals from my wood stove...
I think Phil gave some great suggestions. My take is that it's best to use what you have. Using it for chicken litter sounds awesome and will certainly add the nutrients to the char and crush it for you (which also seems like an issue for people (see this thread for more ideas there).
I suspect that the real reasons no one answers in detail are that "it depends" and those that are doing it successfully either don't want to give away their secrets, or their situation will be different from yours so won't apply anyway.
Although I believe biochar is definately worthwhile for many soils, it is still for the long term and having created the environment for the biology to thrive the only missing ingredient is time. Innoculation just gives you a bit of a short cut to getting that soil biology established, so I wouldn't stress too much about it. I suspect a few days or a week is all that is needed to get a little extra biology into the mix, or just an hour or so good soak if all you are adding is nutrient like urine, or soaking in compost tea.

Nancy just reminded me of another useful service the chickens will provide. They will happily eat smaller pieces, which will get ground up in their gizzards and be massively inoculated by the time they are deposited on the ground. And your birds should be all the healthier for it. Triple win.

Jordy Buck wrote:My questions are, how long should I soak it to charge it and how strong a solution? Planning on trying both rabbit manure tea and just tossing it in the chicken coup to absorb manure. How do I know when it's full? How could I test the strength?  

I haven't made biochar using the soaking method though here are some suggestions:

Christopher said, " Going to try to break to an even 1inch chuck  material and then soak in a high nitrogen rich liquid  nutrient for about 5 months or so.

https://permies.com/t/218794/Biochar#1854665

Dan said, "I soak mine in compost tea and usually some nitrogen source for 2+ weeks.

https://permies.com/t/181158/long-inoculate-biochar#1426511

Phil Stevens wrote:

Your barrel burns are looking good. Have you tried angling the drum to change the airflow pattern?

I aught to try it on an angle, it might work better I suppose.

Nancy Reading wrote:Hi Jordy,
Congratulations on your set up. I haven't got very far with my biochar manufacture. Partly because I can't get myself organised to manufacture it on purpose and am still just raking out coals from my wood stove...
I think Phil gave some great suggestions. My take is that it's best to use what you have. Using it for chicken litter sounds awesome and will certainly add the nutrients to the char and crush it for you (which also seems like an issue for people (see this thread for more ideas there).
I suspect that the real reasons no one answers in detail are that "it depends" and those that are doing it successfully either don't want to give away their secrets, or their situation will be different from yours so won't apply anyway.
Although I believe biochar is definately worthwhile for many soils, it is still for the long term and having created the environment for the biology to thrive the only missing ingredient is time. Innoculation just gives you a bit of a short cut to getting that soil biology established, so I wouldn't stress too much about it. I suspect a few days or a week is all that is needed to get a little extra biology into the mix, or just an hour or so good soak if all you are adding is nutrient like urine, or soaking in compost tea.

I think the more important part would getting it full of nutrients, not microbes. Microbes are in healthy soil enough already. I would think that if I put out a 1/2 inch of empty char across my soils, it may really suck the available nutrients up. So, soak it in a nutrient-rich conglomeration first. I'll also probably apply it in the fall so I have time to see it's effect on available fertility well before growing season.

The best way to check how the inoculation worked is to try it out: Prepare one set of pots with your normal soil, (A), one set of pots with soil and biochar (B), and one set of soil with inoculated biochar (C). Ideally in the proportions in which you would use them. Seed something (garden cress for example)

Then look how they grow.

Some plants like beans who fix nitrogen do not show a growth depression when growing in un-inoculated biochar.

You can use an ec meter (electrical conductivity) in the water you are soaking the biochar. The measuremwnts will rise as minerals are released from the manure and after a while they will get lower or stable as the biochar removes them from the water.

Alternativelly, just leave for as long as it is practical for you.

If you worry about anaerobes, drsin the water, mix some good finished compost or vermicast and leave it for a few days. If not to fine, biochar will have aerobic conditions and your aerobic microbes should dominate. If the pile geta hot, just wait for it to cool and smell it before aplication. Hope this helps.

Camilo

Microbes and minerals work together.  As Phil was saying, you don't know the exact output, but you are trying to make a reasonably fertile supplement to your soil.  Microbes make the minerals work, as Elaine Ingham has shown for decades.  It would be hard to put microbes out without healthy nutrition, and they wouldn't live long without something to live in and on. I use a chimney on my 55 gallon barrel. It has been recommended for years. Something about the temperature and flow.  Mine shows no wear after about 30 biochar burns.  It may be something about limiting the amount of oxygen.

John S
PDX OR

Seeking advice - my backyard kiln is a 30g retort (in 55g oven) supported over a 55g TLUD, with a 6' afterburner:   the support rack over the TLUD I've used is a rack made of old bedframe angle iron (1/8" thick? steel), however it bends during a burn under the load.   It get very hot there, not just over the TLUD but also right under the retort furnace -- the steel turns red, but not white that I've noticed.  I assume that this is around 1200degF, meaning that the retort may be baking at the target high temperature of perhaps 800-1000degF.    The problem is that the load must stay level through the burn or it could fall  (btw I use 4 chains to hold the afterburner stack upright over the retort oven).  Using compensating spacers to level out the 30g retort and 55g retort oven is a bit precarious.  I'm looking for a more lasting solution.

Question:  what material can I use (hopefully not too expensive and not too difficult to fabricate into a support rack) that will last more than a couple of burns without bending under the heat and load?  Ok I might be willing to pay a metal shop fabricate something suitable (what am asking for?) given my time does have value, and I've gone through several angle iron racks that take time to cut and bolt together.

In the works to try unless you have a better suggestion :
     - stacks of (scavenged) limestone tile, with pieces of steel sheet metal to distribute the weight over that brittleness:   will it turn into lime dust during a burn?
          I've tried looking for used ceramic tile, however unless the tile is marked what I've seen to date is not convincingly the higher heat resistant ceramic type necessary.
     - heavy (3/16" thick? steel) 1" and 2" steel pipe (scavenged free), bound with pipe clamps (drilling holes to bolt it quite a hassle, although perhaps necessary)
     - heavier 1/4" thick steel 1-2" steel box rod i.e. square pipe, with holes to bolt together or without just gravity.  Perhaps some used exercise equipment at thrift store has sections with holes I could adapt.

thank you for your constructive suggestion ...

[   my backyard biochar kiln design was informed by:
    https://cdn.permaculturenews.org/files/biochar_john_rogers-jan8-2012.pdf
    https://biochar-us.org/sites/default/files/presentations/3_4_2_Baker_Norman_0_USBI_TLUD_biochar_2016.pdf
]

James - the problems you describe are why I abandoned the TLUD path early on in my biochar R&D phase. Too many steel things, exposed to high heat in an oxidising environment. I was also put off by how fiddly a stack reburner can be and didn't like how many test burns had copious amounts of smoke early in the cycle, nor was I a fan of cutting my feedstock into even lengths. So I switched to flame cap methods...first a pit, and then steel drums and finally kontikis. The tradeoff is that when I do a burn it's a good chunk of the day. But I am a natural-born pyro and tending a fire for 4-5 hours is a great way to unwind.

My setup is a big cone with about 900 litres capacity when full. Things I like about doing it this way:

Very little preparation of the feedstock. I do lots of brush and prunings, and the size of the kiln (130 cm diameter at the top) means I can put in branches up to 2m long into the fire, especially in the first half of the burn.

Range of material I can put in goes from chips and sawdust up to small logs and root balls. The upper limit is about 75-100 mm cross section, but it's not a dealbreaker if a piece doesn't get charred all the way through. It will go into the next burn.

I can keep smoke down close to zero and it's interactive rather than making changes to the design of my rig.

I can do other tasks in the immediate vicinity...watering, pruning, stacking for the next burn, mowing the lawn or making hay, screening compost, you name it.

I like standing around a fire, especially when it's cold out.

I started in the retort direction, but it seemed too complicated. It also didn't produce enough char.  The TLUD non-retort has been the best for me. After about 30 burns, there is no sign of wear.  It is simple and makes good biochar.  I think the most important thing to think about is what is going to work the best for your particular situation. I live in the suburbs and I can't make a trench and burn 700 pounds of wood. They would call the fire department. Plus, I would destroy my orchard. I just don't have that much space.

John S
PDX OR

I respect my local air pollution ordinance so can’t do open burn kilns.  I like the 30g retort, which ends up producing as much product as the 55g tlud after ash removal; just as soon skip sifting or rinsing out the ash.  But doing both together works well for me, now that I’ve figured out feedstock moisture and size composition, and how to control primary and secondary forced air.    Although perhaps I’m running it all too hot, resulting in bent support frame..

When you say "after ash removal", are you getting ash in your biochar? I don't hardly get any in my TLUD.  You may be burning too long or something.   I would check it out.
JohN S
PDX OR

James, it might be a bureaucratic detail in your local ordinance that prohibits open burning for air quality reasons, but a well-tended flame cap burn using dry wood emits close to zero particulates and very little visible smoke (mostly just at startup and quench time). It's probably a long process to get there, but it would be nice if municipal and rural district authorities got a primer on pyrolysis done well so that they could carve out some exemptions for what some of us want to do.

reply to John S ..  there are tradeoffs with my setup (retort over TLUD) -- sure I could just use TLUD and tend it closely to minimize ash, but I prefer the benefit of my current arrangement with respect to having learned the right feedstock mix (size range smaller for TLUD than retort which suits my feedstock on hand; species e.g. variability in wood gas volatiles & latent moisture for a given seasoning) such that I put more attention to setting things up right then I don't have to tend the burn other than watching for the burn phase changes to adjust the forced air (I use variable speed fans (hair dryer with the heat element off at the bottom of TLUD =  primary air, computer fan with PWM speed control into the top of the TLUD barrel = secondary air).   Over all I'm satisfied with the balance/tradeoffs between TLUD and retort, in particular given that I have a huge pile of Liriodendron=tulip tree wood split to 2" which is my greatest feedstock -- generally too big for TLUD but can do a higher proportion of larger pieces in the retort.

reply to Phil S .. G'day mate! I was fortunate to be an exchange student in Christchurch many years ago, and hold great affection for kiwis and New Zealand..   Our particular air pollution regulatory arrangement will be dominated by far greater concerns than hobby biochar enthusiasts -- history of irresponsible barrel-burners,  wildfire catastrophe and associated misplaced hysteria (I mean was this not foreseen and largely preventable:  where people build & insurance subsidy, forest management practices, climate change),  ag burning of orchard trimmings (seems to me a wide open opportunity for promoting flame cap burning methods towards orchard benefits of biochar) as so on.

James Dempsey wrote "size range smaller for TLUD than retort...."

I don't understand this. If i used a 30 gallon retort inside a 55 gallon barrel for a retort, the size for the retort would have to be smaller.  The wood for the TLUD can fill the whole barrel.  Since the retort is smaller and inside the barrel, it would have to be smaller.  I fill up the entire barrel with wood, spaced appropriately to burn hot and not smoke. I can put much larger pieces inside the TLUD than I would be able to put into the retort.  Maybe there is some part of this that I don't understand yet, but it doesn't make sense to me at this point.

John S
PDX OR

In regards to the OP’s question.  I wouldn’t overthink it, just mix what you have with what you make and spread it when you get around to it.

Litmus paper and char mixed with distilled water will give you an idea of pH.  MI soils are likely acidic.  Do a soil test every couple years to make sure you are not way off the mark with your amendments.  

responding to John S:    
    If I was in an area geographically less subject to air particulate issues (as well as immediate neighbors, and regulations I understand, respect and support) I might have considered sticking with an open TLUD alone and save extra trouble of fabrication, and if I had the energy & time to carefully tend ongoing burns to minimize smoke and optimize output  -- but I don't want to, more interested that the device do more of the work if that can be arranged ...  your thoughts are still correct:  there are fortunately a variety of ways to go about it to suit different folks in different circumstances.
    The volume to place wood into the 30g retort is (presumably) 30g;  the volume to place wood into the 55g TLUD in my case is 55g less the primary air diffuser (bottom 3" of the barrel interior) and less about 4" below the modified lid at the top to accommodate my secondary air blower intake.   Yes, you are correct I think that the resulting volume is larger for the TLUD that I use,  vs. the 30g retort.     However...
    By "size range of wood feedstock", I mean that in order to optimize my particular retort-over-TLUD setup, what seems to work best in my experience for the (untendable) TLUD is a smaller feedstock size range -- generally under 1" smallest dimension of a given piece (which could potentially be up to say, 38" long?), and if I use any of the very abundant 2" feedstock that I most desire to use, that requires in my experience to add a larger portion of <3/4" to compensate.   In the retort I use larger feedstock size range, usually as much 2" feedstock as I can fit (that is, pieces 2" x 2-10" x 8-30") filled out with smaller material as space allows.  Solid wood will produce more biochar end product than the equivalent volume occupied by pieces since the pieces will have more air space and surface area (and in the TLUD subject to oxidation to ash).  There does need to be sufficient space between pieces in the retort for water vapor and then volatiles (wood gas) to pass through and out the bottom, as well as heat to penetrate, so in both my TLUD and retort they don't work well packed tightly -- end up with undercooked pieces that need to run through again, certainly for any pieces larger than 2" (in their smallest dimension).
    ... the other issue with my dual retort-over-TLUD setup is that the TLUD is not necessarily 'done' at the same time as the retort:  the retort can be left to run itself out and cool to be harvested at my leisure, but not the TLUD.  On the TLUD I can seal the primary and secondary air intakes as well as the hole in the top lid while it still burns, but the latter generally only after the retort furnace blast (and need for secondary air) has run it's course - I've learned to tune the feedstock mixture (size ranges, and e.g. in the retort use some softwood along with hardwood feedstock for sufficient volatiles i.e. wood gas) such that when the retort is puffing it's last gasp is the time to seal the TLUD.  I water down the TLUD contents and when I'm satisifed the seal is good (not letting any oxygen get in) I generally leave the whole rig to cool overnight before disassembly.  And that works pretty well.   A little ash to sift or rinse out in the TLUD's output of mostly medium/small/fine bits, no ash in the retort output of mainly large/medium chunks.  
    The resulting output volume of each is similar (a full wheelbarrow for each, possibly more from the TLUD but not that I have noticed), after I have accounted for differences in suitable size range of feedstock for each, in the setup prior to the burn, given the operational limitations of this setup.  I suppose a more accurate and meaningful measure would be to grind the respective output as I do after innoculation, and then measure the 0-1/8" granular dust volume and the 1/8-3/8" bits volume for each (TLUD and retort).

Great details, James.  I think my TLUD is a bit different.  I do place 2" and bigger diameter branches in there. I just need to be careful to let the wood dry.  Obviously, it has to be less wide than the barrel, unless I angle it a bit.  As I said, I have to carefully place pieces in there according to air space and size to get it really burning.   I actually will put some thicker pieces in there once it really starts burning well.  I add some wood after filling the barrel, when it has burned for a while.  My goal is to make about 2 1/2 buckets (5 gallons each) of burned char to take out of the oven, to place on the panels of plywood so I can run over them. Then after crushing under our truck for a week, I extract a bucket of crushed char to inoculate each week.  So I burn about every 2 weeks, and every week, I take out a bucket of crushed char to inoculate, and every week, I dig in a 5 gallon bucket of crushed, inoculated biochar into the garden.  That bucket of biochar has been charged for two weeks.

John S
PDX OR

Phil Stevens wrote:James, it might be a bureaucratic detail in your local ordinance that prohibits open burning for air quality reasons, but a well-tended flame cap burn using dry wood emits close to zero particulates and very little visible smoke (mostly just at startup and quench time).

I have no doubt that is true, and yet I think it the feedstock is a factor.

Well dried, seasoned hardwood seems to get into the clean burning zone quite quickly.

Softwoods like spruce or pine, no matter how dry, seem to be smoke generators in an open fire. I mix with hardwood whenever I can as a control measure.

The vortex is the key. A good flame cap will develop a rolling zone of turbulence that mixes any smoke back into the flame zone. I can burn sappy pine and macrocarpa and get a smokeless burn with a kontiki or a pit...as long as I don't overfuel the fire. Then it goes into hot overrun and produces black smoke.

A plain old open air fire with softwood is a smokefest, that's for certain. We have to control the airflow if we want a clean burn.

Phil-
Is that why a TLUD with a chimney is efficient? Because the smoke gets burned twice?
THanks,
John S
PDX OR

John - If it's designed well, the stack on a TLUD will function as a reburner. I've seen some where all it did was to loft the mess higher up, not unlike the factory smokestacks of old. Make it the next town's problem.

To get complete combustion on a TLUD you need the right combination of secondary air, turbulence, and heat retention to keep it alight. Easier said than done, especially if your feedstock is not always consistent from one burn to the next. And it's more of a problem at the early and late stages of a session, because when the inner vessel really starts pumping you usually get into a situation where it's drafting great and there's lots of excess heat.

Great info Phil.
Thanks,
John S
PDX OR

re  

James Dempsey wrote:    "Seeking advice -  30g retort (in 55g oven) supported over a 55g TLUD, with a 6' afterburner:   the support rack over the TLUD .. bends during a burn under the load.          Question:  what material can I use .. will last more than a couple of burns without bending under the heat and load?  "

I  did a little research and discovered that common steel (carbon steel, galvanized with zinc, or straight iron) is not adequate to those temperatures (>1200degF) under load but stainless steel is (alloys #304 and better #316, which contain in particular more chromium and molybdenum which maintain strength at higher temperatures).   Unfortunately, new stainless steel box tubing (two ~1"x16.5", and two ~2"x20") cost a lot - so where could I scavenge something used like that?        I'm now looking for discarded 'chromoly' bicycle frames:   'chromoly' is steel alloy #4130 with chromium and molybdenum, which for bicycle frames makes it much lighter with the right amount of strength & flex -- I'm hoping incidentally also suiting the high temperature strength I'm looking for.

Any insight you have is much appreciated ...

[   my backyard biochar kiln design was informed by:
    https://cdn.permaculturenews.org/files/biochar_john_rogers-jan8-2012.pdf
    https://biochar-us.org/sites/default/files/presentations/3_4_2_Baker_Norman_0_USBI_TLUD_biochar_2016.pdf   ]