What is your end goal with biochar?

When I started making biochar, I had been reading for a few years about how much it can help the soil and the garden. I had finally found a method that I believed I could use. I did use it and it's been a game changer for me.  

After making biochar for a few years, I started to ask myself, "How long am I going to keep making biochar?" I think that 2024 will be the first year in which I actually make less biochar than the year before.  I have an average suburban yard, so there is a limited amount of space in which to put the biochar.  I have a lot of outside interests, I still work, I have a family, and I have a lot of other things to do.  

I have been digging the biochar in around the dripline of trees and bushes.  I put it in around several, and found that they grew and produced better.  After awhile, I decided that I wanted biochar near most of my plants so that they could access it.  I noticed some plants doing better when they had biochar within a few feet.  I also noticed that some did better with extra biochar.  I am filling up my yard so that there is biochar around every tree or bush, in every raised bed, and soon within 3-4 feet of every larger plant.  I guess, at this point, that is my end goal.  I may end up making biochar less frequently as I get closer to this goal.  Of course, I will still make some and listen to the rest of you, as people are always coming up with new ideas and techniques that seem to work better.

What is your end goal with making biochar?

John S
PDX OR

Hey John,

Good question. I'm always reading your posts and wanted to say thanks for the dialogue about biochar you keep with everyone on here.

I guess I'd say my end goal is to add more good biology to the soil. There are parts of my yard that are rock hard clay, other parts aren't as bad. But I've noticed that the addition of biochar seems to help everything I give it to, it just sometimes takes a year or at least that's what it seems like. I'm just assuming that it's robbing nutrients at first if it's not "charged".

I've been wanting to ask you (and I'm sorry if you've gone over this before) if you noticed the biggest difference the year AFTER your biochar application? It seems to me after playing with biochar the last handful of years that it takes a year to settle in or however you want to say it. I'm admittedly bad at charging but have also heard some people don't charge at all, I just like to let mine sit for a while and maybe get rained on a couple of times, or run some through the compost. Like you, I'm putting it around all of my plants and trees. I don't make huge amounts at a time, I just put my fire out a little early when it's almost done burning and I'll come back a couple days later and sort through it. I'll even take a half charred log and drop it around the tree on top of the mulch. I did one of my seedling crabapples like that and it's one of my few survivors from last year. I wish I had more to play with, but I think even a small addition to a planting hole or a little bit in the drip line of a tree makes a difference in what the tree can take up from the soil around it.

I've got alliums planted all over my yard and the biggest, brightest green onions I have are directly beside a trench I dug two years ago and did a burn in. I don't think it's a coincidence as I'm assuming that plant (and the others around it, garlic chive, crimson clover, hairy vetch) is getting the most it can out of my soil. I'm also adamant about adding leaf mold, leaf debris around everything. That way the charcoal is getting charged every time water washes mulch into the soil beneath it. I've had good success with this and can't imagine not doing it going forward. We have summer with no rains here and I've got to assume that the charcoal is holding onto to some good things that would other wise not be there, or just get washed away with a rain. Thanks again for your time.

Hi Thombo,
Thanks for your nice comments.  Sometimes, after the initial biochar, the plant takes off just that year immediately.  More frequently, it takes a year.  Sometimes it has moderate growth both the first year and the second.  

I don't think that rain water is going to help much in charging your biochar.  Compost should work really well, although you might want to leave it longer than you would for liquid inoculants.  Some people use compost in combination with chickens or rabbits, and that seems to work really well for them.

I think a lot of people are going to use your method of partial burning if that's all they have time for.  Even digging out camp fires and field burning could help.  Getting more people to participate in some way can have tremendous benefits.   Really, you're making a combo hugulkultur and biochar, which might end up being really great in the long run.  It may end up being more similar to what many of the indigenous groups have done world wide.  Much of scientific progress occurs because of accidents, experiments or "that's all I had time/money/resources for".

I love the particular results like that your onions did super well when they had access to the biochar.

We also have summers with no rains.  Great for making biochar.  I think you're right that since biochar is "hotels for microbes", it holds onto the microbes, which hold onto minerals and other nutrients, and sets up the structure of the soil. Then mycelium can travel more easily.   This is in addition to the benefits to the texture, as Elaine Ingham et al would explain.  Yes, I put my biochar first into areas where the soil was worse.  I'm also adding leaf litter, mulch, compost, etc.  They don't compete with each other as techniques. They are complementary.  The worse the soil, the more the need for amendments, IMHO.
Great post.
John S
PDX OR

My primary goal is adding value to wildfire fuel reduction work that already needs doing. If what I do can also help my garden, which I believe it does and that it will continue to be beneficial with a lot more biochar, then it justifies the work even more and saves time and resources watering or amending soil in the future. Maybe if my garden and food forest is epic enough to motivate others to emulate my wildfire prep work, which is also watershed restoration and water/carbon sinking work, it will have a larger impact.

John, it's a good question.

For me it's a triad of things that mesh together:
1. -- fire load reduction/dead brush management
2. -- building soil fertility and moisture retention
3. -- offsetting my fossil fuel carbon emissions.

(If I had time, I'd build an ASCII graphic. Just because.)

1.  I have dangerously large amounts of brush that I have to deal with, on steep hills, as part of wildfire control. Burning this into char instead of ash makes this endless chore a bit more meaningful, since there's a useful end product as a result of my labour.

2.  I have been using char to build soil tilth for at least 15 years, first on a heavy clay base and now on a sand/silt hilltop. In all cases, I feel the results are positive. My latest experiment in our drought is a four-part mix of anaerobic ferment, char, compost and half-digested wood chips, with maybe a little weathered straw mixed in and left to soak a while. When I generously top-dressed garden annuals that were withering with this brew, they suddenly caught hold and started thriving and producing. The plants have spoken!

3.  Where I live, there is no avoiding some use of fossil fuels. And, I would like to make a couple of 1-hour flights to see family who are a bit too far away for driving. This requires some pretty significant biochar production as a hardcore, meaningful offset rather than a $3 feel-good greenwash. And that brings me around to #1 ...

I first experimented with biochar as an addition to my chicken coop bedding and potential dietary supplement for the chickens.  I made my first batch in December of 2020 in two metal paint cans in the fire pit, and it worked great. The biochar kept the odor down in the coop and then the coop got cleaned out into our sizable chicken-run compost system.

As I start to use some of the sizable amounts of compost I have created with chickens, more biochar to mix into it as I add it to our soil is appealing. I'm running a small chicken tractor over my yard to have the chickens tear up the scrubby, weedy excuse for a backyard I have, then laying down a thick layer of compost and replanting grass. Little by little, I plan to eventually redo the whole backyard in this manner.

That should keep me busy for a while, and the idea of creating biochar with invasive species is really interesting to me, I'm small scale, currently making batches in a 30-gallon metal trash can in my firepit, so it's really all about finding a way to make a lot of batches. I may try to set it up so my 12 year old can do a campfire in the backyard any day he wants after school and make me some biochar at the same time.

But I'm hoping to not stop making biochar. I think it's such an amazing thing to do for soil and the planet in general that even if I need to dump char in the woods or into random fields, it's worth it for me.

My goal with biochar is to add a water retention quality and to add lasting fertility to the soil.  

I use biochar for my winter chicken run. I confine the chickens for the winter over my garden to boost its fertility. Using charcoal from my woodstove I use it in my deep litter system to reduce the ammonia and smell of chicken manure. It also charges at the same time. In spring time I use the deep litter of leaves, charcoal and manure to make the compost pile for the year. I also put a small amount into the chicken food as a health and mineral supplement. I also add it to compost to supply carbon and absorb the nutrients and microbes. However, I make too much charcoal for just the chickens so I mix the rest with urine and then dump it on the garden after it soaks for a week or two.

My end goal really is to recreate terra preta soil in my garden. I want the soil so dark, organic and stable that archaeologists dig it up thousands of years later and argue about its origin. I suppose that will be accomplished when the black soil starts to expand of it's own accord and the soil around the garden starts to darken. The other indication of success will be a kick butt potato harvest. Any extra biochar I'll put at the base of trees and bushes.

Skyler Weber wrote:I want the soil so dark, organic and stable that archaeologists dig it up thousands of years later and argue about its origin.

I love this sentence. You have now given me a goal to work towards as well. Love it!

I'm excited about bio char but i have some hang ups and can use help

...my goal with bio char is to find out if it is safe...
-Does it bind to heavy metals and lock them up in the soil? or from the metal in char making kiln/barrels?

The metal in my barrel is steel, I believe.  Mostly iron probably, which is a human nutrient and healthy for the soil.  Biochar has been used for hundreds and maybe thousands of years, intentionally or unintentionally.  I have never heard of any concerns with that, and there are multitudes of really smart scientists working on it.  My guess would be that it's not a big concern.
John S
PDX OR

every ton of biochar is a ton of carbon that is removed from the atmosphere on a relatively permanent basis (as long as it is put into soil and not burnable). I investigate how to use biochar as a way to encourage carbon dioxide removal (CDR) and soil carbon sequestration. We can't make too much of it.

I guess I have a nested set of goals in terms of biochar. At the micro level, I want to make better use of the excess biomass that our land produces and create more fertility and diversity with it, as well as doing what I'm able to pay off my carbon debt and keep drawing down that atmospheric excess as much as I can. On the community and regional scale, I want to get as many people as I can excited about making the stuff, using it, or both, and eventually having lots of small producers supplying local demand. When it comes to the big picture, I want to see biochar talked about -- and put into action -- instead of all the whizzy, shiny, expensive and (in my view) pointless industrial "carbon capture" technology that grabs headlines and soaks up huge investment from oil companies and airlines.

My production has tapered off considerably over the past year, mostly because I took on some contract work that's chewed into my spare time, but also because I'm at the mercy of the weather with flame cap methods. I average about one burn every two months, for a yield of 600-900 litres per burn, and I'm still sitting on a stockpile of about 10 cubic metres of biochar. I bag up and sell a little bit through a friend's heritage fruit tree nursery, and also move a bit out the farm gate. The biggest delivery this year was a trailer load to go into the substrate mix for a living roof on a timber and earth sensory deprivation meditation room.

I don't go out of my way to market what I produce, mostly because I can't scale up the commercial aspects in a way that is sustainable for my time, material and energy inputs. I could easily use every bit I make on the land right here, and that is happening gradually as I keep adding it to the garden beds, fruit trees, berry patches, and building materials. Soil that used to go anaerobic in the wet season and turn to rock in mid summer is now crumbly, dark, and fragrant. I spread it on the paddocks in chunk form and let the grazing animals work it into the topsoil and that is making a massive improvement to the productivity of the pasture. And I use the dry material that gets made in the fire over winter as bedding in the chicken coop to stretch the renewal interval of the wood shavings, as well as throw a bucket out for the birds to peck at.

So that's the shape of it at the moment. Maybe the coming year will be the one where I can get the stars aligned to set up a bigger system...who knows? There is certainly a lot more interest and awareness than there was five years ago, so it all comes down to the business side of things.

Phil Stevens wrote:When it comes to the big picture, I want to see biochar talked about -- and put into action -- instead of all the whizzy, shiny, expensive and (in my view) pointless industrial "carbon capture" technology that grabs headlines and soaks up huge investment from oil companies and airlines.

I agree...as fun as having a whole bunch of high tech "pilot plants" running for a few years until they burn through all the investor money and then shut down, actual shovel (and match?) ready technology exists and isn't utilized because it's not glamorous enough.

The potential for stacking functions with biochar is what I think is really amazing. Does it make sense economically as a way to reduce waste? Probably not completely. What about as a soil amendment? Perhaps not.  What about as a CO2 sink? Not compared to other "carbon credit" schemes. But when you combine all three? And maybe add in benefits to livestock production? There's not anything else out there that can do all three, while employing a bunch of people at the scale biochar would.

I mean, if you looked at a map of area with access to significant waste biomass and/or railroads where that biomass could be transported in (and biochar back out) with areas of low employment, I bet there'd be a bunch of places both in the US And globally that would benefit greatly from a biochar production facility.

I don't know if it's government who should step in, or big business, or something else. Certainly don't want a political discussion about that. I will say that when I see really rich owners of massive amounts of US farmland like Bill Gates worrying about climate and talking about lab-grown meat from his private jet, it does make me a little nuts. There's a guy who could jump-start the biochar industry in a major way! Anyone got his number?

Being my first 'real' season of making bio-char hard to even think of 'end' goals. I've been composting my leaves with cardboard and adding my worms to create another grow area. I watched a video of another doing the same and adding the bio-char to the mix. As it steals neutriments for the leaves, it breaks they down, win/win as I see it. The other use I've learned of was using this mix as mulch on 'all' the beds.

When, should if, I'm done making beds, then using it as mulch seems to be the continuance. Like I say, first real year of producing and a long way to go before even thinking end goal.. :>)  

Welcome aboard the biochar train, RJ Howell!

Biochar mixed with compost is used successfully  by many as a mulch. I would hesitate to use pure, even crushed and inoculated biochar as a mulch/top dressing, as it can dry out and kill the life within it.  I always try to put some mulch over it, especially during our very dry season.

John S
PDX OR

10% by volume, 6 feet deep across my full 12 acres.

OK, that's my dream, but most of my land is in forest so I'll just be happy to top dress it every decade.

Greg Martin wrote:10% by volume, 6 feet deep across my full 12 acres.

OK, that's my dream, but most of my land is in forest so I'll just be happy to top dress it every decade.

Dream big! That's why I'm not concerned about what to do with my "stockpile" and future production. We're on just under a hectare here and getting to 10% by volume to 30 cm depth would require over 250 cubic meters. That's a decadal project for one man with a kontiki (never mind the fact that this particular one is getting a bit long in the tooth and cranking out 25 cubes a year could be overly ambitious). I'd be happy with an average of 1-2%, going higher in the garden beds and berry patch.

I have lots of comtainer plants and it gets costly to buy all the potting mix every year. Besides, I ran into some contaminated mix a few years ago that killed quite a few of my plants. My goal is to make most if not all of my own potting soil. It will ideally be mineral soil based, well draining and fertile.  I incorporate a lot of biochar since it has many desirable properties and makes good use of my available resources.

1. Biochar in certain extent can replace peat moss or coconut coir for water retention.
2. Biochar can add to drainage. Although I crush some char to increase the surface area, I also set aside char made from fine textured feed stock as is to light up the potting soil.
3. Biochar is highly absorbent for nutrient. Especially in winter time when where is few growth happening, I add fresh chicken manure to the char to sequester the excess nitrogen.
4. Biochar makes great compost. I usually need lots of potting soil in the spring while autumn leaves (mostly oak) won't be breaking down by then. With biochar inoculated with nitrogen rich manure and kitchen waste, I am able to speed up composting chopped leaves during winter.

So far the potted plants growing in the new potting soil with biochar are doing great, with the exception of gardenia maybe. When I have extra biochar I will add the goodies to the garden area too.

I didn't have the time, energy, or equipment to make my own biochar - SO - I bought 4 large bags of real charcoal (chunks) and I applied that to my raised beds and tilled it in.

I think I could have gotten by with just 1/2 per raised be as they are only 3 ft X 15 ft. and I keep pulling out larger chunks that pop up to the top.

These are like little motels for all of the good microbes that benefit our soil and plants!

Jesse,
I think you'll find that if you look into it, buying charcoal doesn't serve the same purpose as real biochar.

John S
PDX OR

Here are some responses: https://permies.com/t/233548/Commercial-charcoal-biochar

https://permies.com/t/193954/handy-guide-charcoal-biochar-activated

https://permies.com/t/150787/Biochar-charcoal-bought-store

John S
PDX OR

We are not yet using biochar - but this year I'll create the means to generate biochar in preference to winter burn piles.

My property generates too much wildfire fuel load. One of the main reasons for maintaining a cow herd - apart from the fact I raise a rare breed and therefore helping to preserve rare genetics - is to eat brush that helps reduce the fuel load. Its not enough, we still have to do chainsaw work every year, that produces slash. So far we have just burned the slash that did not get incorporated via chipping. But I'd like to mostly produce biochar instead of burn piles.

The biochar would then be used generally on my property to increase soil water retention. Ideally, I would use compost tea to charge the biochar with biology. I also want to start feeding biochar to the cows, thereby helping to spread the biochar in the pastures.

We have a project planned for this spring to rejuvenate the way we currently use the main farm garden (which is fenced from the deer). I'd like to incorporate biochar and rotted wood underneath the raised beds.

I'm no rancher, but I would think that goats would be more effective than cows at eating brush.

Compost tea is a very effective means of charging your biochar.

Many people feed or mix their biochar with animal droppings.

Rotted wood and biochar are a great combo for soil.  

I love the win-win-win of using chopped/fallen wood, decreasing fire risk, and rebuilding soil!

John S
PDX OR

John Suavecito wrote:I'm no rancher, but I would think that goats would be more effective than cows at eating brush.

John S
PDX OR

Hi John - however useful goats might be in a one-off clearance operation, they are banned from my property on an ongoing basis. Sheep maybe, goats never. Goats are too destructive of everything they come in contact with (including playing king of the hill with vehicles). Trying to keep them fenced into an area is just too much work and expense. We don't keep horses either. Both goats and horses will rapidly make a desert out of a green paddock. I'm not going to go down the route of keeping a livestock guardian dog (or two) and in North Idaho with wolves, coyotes, foxes, bears and cougars (all of which frequent our property), the smaller ruminants are just too much at risk. We even have pine martins - which have been known to predate on lambs, so I imagine kids would be on their menu as well. The predators that visit our farm have taken down elk, deer and moose. So far we have never lost a cow or her baby to the local predators - but I'm not planning to increase the temptation with smaller tasty morsels.

You'd be surprised at how much brush cows will take in, when they get bored with grass. The brush probably provides other nutrients as well.

Great info, Mary.  Sometimes an overall strategy works best.
John S
PDX OR

Mary Combs wrote:You'd be surprised at how much brush cows will take in, when they get bored with grass. The brush probably provides other nutrients as well.

Yes, cattle reduce underbrush. They will tear off young leaves and new growth from trees and saplings. What they don't eat they will rub against or trample. The downside is that native plant cover like wild strawberries is also destroyed; I used to fell trees to create no-go zones -- islands where native plants could thrive.

Douglas Alpenstock wrote:

Mary Combs wrote:You'd be surprised at how much brush cows will take in, when they get bored with grass. The brush probably provides other nutrients as well.

Yes, cattle reduce underbrush. They will tear off young leaves and new growth from trees and saplings. What they don't eat they will rub against or trample. The downside is that native plant cover like wild strawberries is also destroyed; I used to fell trees to create no-go zones -- islands where native plants could thrive.

That's a good idea. We get a fair amount of wind thrown trees every year - usually saplings up to 6 inches in diameter. We could use those stems to create no-go areas without a lot of expense. The manpower needed would be just a little more than normal maintenance clearance.

Mike Farmer wrote:

Phil Stevens wrote:When it comes to the big picture, I want to see biochar talked about -- and put into action -- instead of all the whizzy, shiny, expensive and (in my view) pointless industrial "carbon capture" technology that grabs headlines and soaks up huge investment from oil companies and airlines.

<snip>

I don't know if it's government who should step in, or big business, or something else. Certainly don't want a political discussion about that. I will say that when I see really rich owners of massive amounts of US farmland like Bill Gates worrying about climate and talking about lab-grown meat from his private jet, it does make me a little nuts. There's a guy who could jump-start the biochar industry in a major way! Anyone got his number?

I agree that it makes more sense to incorporate more "low tech" solutions.  I think we'd be better off with more, smaller, local entrepreneurial solutions in most respect than leaving it to the big boys.  I did 13 years time in the Canadian federal government and it got to be too much inefficiency and bureaucracy for this son of a farmer.  Also, when solutions are more local, we reduce shipping of both biomass and the char and, if is it loaded up into biochar then the microbes involved are more locally correct / adapted.  That also plays to the permaculture principle of using small and slow solutions.

I've just started mucking around with it a bit.  I wish I could get more locally sourced easily, but after discussing with a producer in Calgary, whose solution was for me to purchase a lot of his biochar, then ship it about 1300 km, then have to activate it, I resolved to do what I can with what I have.  As others have mentioned, I'm just working with cleaning up deadfall on the property (I do leave some brushpiles as habitat, but wind up with more than I can handle that way).  I have a chipper/shredder that can handle stock up to 3" (if it's straight enough to feed in) so I strive to create some wood chip to use as mulch.  Other material is typically cut and stacked for the firepit, but that pile has grown much faster than we've been burning.  Like someone else mentioned, I'm thus far effectively just managing with some of the charcoal that is left from fires.  An 8 lb sledge hammer helps to break it down into finer pieces, then into nearly finished compost.

We have about 3 acres or so of our property that has been industrially / chemically farmed, so I do want to restore that soil.  Increasing organic matter and adding some biochar to that soil should help improve soil health over time, which will support our gardening / orcharding / copse efforts.  For me, a higher priority is dealing with a barrier to prevent overspray from the field around us (an overspray event into our small orchard is what prompted taking back the land).

So, for goals, I see creating it as a method to reduce dead wood on the property, enjoy a fire, improve the soil, and sequestering some carbon long term is a bonus.  

Derek Thille wrote:
I agree that it makes more sense to incorporate more "low tech" solutions.  I think we'd be better off with more, smaller, local entrepreneurial solutions in most respect than leaving it to the big boys.  I did 13 years time in the Canadian federal government and it got to be too much inefficiency and bureaucracy for this son of a farmer.  Also, when solutions are more local, we reduce shipping of both biomass and the char and, if is it loaded up into biochar then the microbes involved are more locally correct / adapted.  That also plays to the permaculture principle of using small and slow solutions.

On the production side, I agree 100% fairly small, local production is probably the best approach. I'm looking to the big guys to help create demand.

One thing I've love to see is some kind of reasonably priced, preferably mobile units that would allow for some scaling. Maybe something the size of a 20' shipping container or similar. High volume without being industrial scale.

Last weekend, I took a stroll in the woods with the kids. At one point, we were on a long, paved road into the wildlife preserve. If you collected just the deadfall from within say 50 feet of the road and dragged it to the road for processing, you could likely spend a summer just in that one small spot in one small town in the smallest state in the US. More capacity would make it go quicker.

Mike Farmer wrote:
One thing I've love to see is some kind of reasonably priced, preferably mobile units that would allow for some scaling. Maybe something the size of a 20' shipping container or similar. High volume without being industrial scale.

Last weekend, I took a stroll in the woods with the kids. At one point, we were on a long, paved road into the wildlife preserve. If you collected just the deadfall from within say 50 feet of the road and dragged it to the road for processing, you could likely spend a summer just in that one small spot in one small town in the smallest state in the US. More capacity would make it go quicker.

Mike, that's like the holy grail of dispersed production and I would love to see it happening by default. I think for most situations a big limiting factor will be water availability. In the "medium tech" department there are two useful ways I see this technology developing. One is with the mobile container as retort: Line the interior with refractory and fill it up with biomass, then light it and control the airflow, TLUD-style or via some other means. A lot of the designs use interior vessels and sacrificial feedstock. You don't need water to quench if you can let it cool in place.

The other direction is the air curtain burner. There's a unit called the Char Boss that is towable and can go through several tons a day. Ben Zumeta talks about it in this thread. The same company makes bigger, container-sized units, and another vendor has one called the Tiger Cat. The Char Boss uses water to quench in a continuous process. Not sure about the Tiger Cat.

Then, there's low tech. Pits and trenches, vessels like Kelpie Wilson's Ring of Fire, or a steel tank cut in half flipped like a turtle when the burn of complete. All these methods can be used without the need for large volumes of water to quench.

I like that people are considering the climate issue with biochar. But I should mention that experts are saying we need to be sequestering carbon at a rate of tens of gigatonnes per year by mid-century. At best, biochar yield from wood is about 20% by weight, though it is theoretically possible to do better. Although the density of wood varies quite a bit, a dry cord weighs around 1-2 tons - say 1.5 ton average? And let's be generous and pretend that is a metric tonne. So if we did all the carbon sequestering with biochar (which we won't), and did it all with cordwood; we have 10 Gt/year x 5 tonne biomass/1 tonne char x 1 cord/1.5 tonne = 33 gigacords - or about 99 cords of wood per year for each person in the US. That is why I said earlier, we can't make too much. I'll make what I can but if I convert more than ONE cord per year, I will be impressed.

But I think biochar will eventually be industrialized - the pyrolysis gas we burn to make the char will become too valuable to burn. It will become the replacement for petroleum that chemical industries will need to make all the chemicals the modern world has come to demand. Although we can all cut back on plastics, broader society will find it hard to give up paint, detergents, medicines, etc.

Phil Stevens wrote:Mike, that's like the holy grail of dispersed production and I would love to see it happening by default. I think for most situations a big limiting factor will be water availability. In the "medium tech" department there are two useful ways I see this technology developing. One is with the mobile container as retort: Line the interior with refractory and fill it up with biomass, then light it and control the airflow, TLUD-style or via some other means. A lot of the designs use interior vessels and sacrificial feedstock. You don't need water to quench if you can let it cool in place.

The other direction is the air curtain burner. There's a unit called the Char Boss that is towable and can go through several tons a day. Ben Zumeta talks about it in this thread. The same company makes bigger, container-sized units, and another vendor has one called the Tiger Cat. The Char Boss uses water to quench in a continuous process. Not sure about the Tiger Cat.

Then, there's low tech. Pits and trenches, vessels like Kelpie Wilson's Ring of Fire, or a steel tank cut in half flipped like a turtle when the burn of complete. All these methods can be used without the need for large volumes of water to quench.

I've looked at the Char Boss, but my understanding is that the output is pretty low as a % of input - it's really designed to burn the forestry slash to get rid of it, and create a little biochar. But the size is right, something like a shipping container.

The water requirement is an interesting one to consider, and might push more towards enclosed system that use "sacrificial feedstock" for heat. The Exeter Retort is an example that's actually a pretty decent size. If it could be made say three times that size would be even better, but maybe just having three of them (or 10 of them) works too.

The place I walked the other day would be ideal for a setup where a team (paid or volunteer) pulled and prepped feedstock. There's enough down and dead wood that you'd never even consider cutting a live tree unless you wanted to do a little active management.  If they hauled it out of the woods, stacked and maybe covered it to keep it dry. Then a 1-2 person team could follow behind doing 8-hour burns in one or more Exeter-type retort. Show up in the morning, empty yesterday's char, fill the retort, and start it burning. Repeat tomorrow.

I personally don't mind the idea of "sacrificial feed stock" - I think you may get the same amount of final product compared to a more open pit approach, and if all the inputs are waste material anyway, it's not that big a deal. Plus, around here, the soil is acidic and could use a nice dose of ash along with biochar.

End goal is nicer soil. I did a burn a few years ago and was quite impressed with the soil lightness the next season, from a base of heavy clay. I add my fireplace ash and charcoal all winter long to the garden pit. It gets buried with all the leaves and trash and wood and scraps, and in subsequent years dug back up and mixed.

It isn't 'biochar' in the sense of being finely ground, more chunks of charcoal that get more and more broken down each year. It seems to work very well.

Thom Bri-I would be careful if you have alkaline soils, because ash is so alkaline, that it may move your soil too far away from neutral Ph.

John S
PDX OR

Our end goal was always soil improvement.  We use a much smaller, less sophosticated "exeter retort" type system. The outside drum is a 55 gallon drum with a clamp on removable lid with a 40 gallon drum with a tight fitting lid for a retort.  The 55 gallon drum has a series of 1" holes drilled injseries everr 5 inches staggered along the lower 15" with an 60" tall 8" diamter stack in the center of the removable top. The retort has holes drill in the bottom so that the pyrolosis gases add to the burn.  We have three os these set up and can burn two setrs each day alowwing them to cool completely before we empty them and reload.  

We are basically lazy biochar makers,  We let mother nature dry the ingredients, pine to burn, hardwoods in the retort (we used pine in the retort but the yeild was much lower).  We only use dried wood, cut in the summer or fall and biocharred the following season.  We don't pit burn and quench because we lose too much and the quench makes it very difficult to reduce the charcoal in to a semi fine grain. this we do in a cxement mixed with small stones as a ball mill.

We charge our charcoal (10gal) in 55 gallon drums with water 5(5gal), urine(5gal), essential elements and humic an fukvic acids additives.  We stir it every couple of days and deem it ready when the charcoal is sinking rather than floating.  Before we spread it we add equal amounts of sawdust and let it soak with the biochar for about a week.

The stuff works miracles and the only problem is getting it spread in the beds,  We have to rake it out to spread it evenly.

This was a VERY informative thread! Both my daughters have chickens & I have plenty of wood stove charcoal...I need to get some good chicken poop and inoculate some charcoal...My soil sucks! Hardcore clay from Hell...I want good soil before I croak

Cade Johnson wrote:I like that people are considering the climate issue with biochar. But I should mention that experts are saying we need to be sequestering carbon at a rate of tens of gigatonnes per year by mid-century. At best, biochar yield from wood is about 20% by weight, though it is theoretically possible to do better. Although the density of wood varies quite a bit, a dry cord weighs around 1-2 tons - say 1.5 ton average? And let's be generous and pretend that is a metric tonne. So if we did all the carbon sequestering with biochar (which we won't), and did it all with cordwood; we have 10 Gt/year x 5 tonne biomass/1 tonne char x 1 cord/1.5 tonne = 33 gigacords - or about 99 cords of wood per year for each person in the US. That is why I said earlier, we can't make too much. I'll make what I can but if I convert more than ONE cord per year, I will be impressed.

You are entitled to your perspective, but personally I don't buy the gloomy doomie we're-all-dead-anyway-so-why-should-we-try scenario. It's rubbish. "Experts" have been peddling disaster narratives based on dodgy mathematical projections since forever, and nature keeps confounding them with her resilience. Our problems are real enough; and shovels in the ground matter. When I find that young neighbours (stuffed with our wonderful produce) have started growing their own gardens and keeping chickens, and I start tossing ideas about organic methods that beat the supply chain, I know I am making headway. And I will char one full cord of wood this week if I have time, and there is much more that needs to go in the kiln.. I respectfully suggest you can do much more, if you have the will; and I hope you will. My 2c.

Cade Johnson wrote:But I think biochar will eventually be industrialized - the pyrolysis gas we burn to make the char will become too valuable to burn. It will become the replacement for petroleum that chemical industries will need to make all the chemicals the modern world has come to demand. Although we can all cut back on plastics, broader society will find it hard to give up paint, detergents, medicines, etc.

Transportation of biomass to central facilities pretty much negates all benefits -- it's hand waving. Rather, I see a cottage industry where smallholders can extract heat and distill valuable pyrolosis products in situ, build the char back into the land, and sell the stinky gold like farmers sell milk and cheese. We're in the money baby!