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Biochar and forest management

 
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I've recently been reading a decent amount regarding biochar and its applications and I'm curious about people's thoughts on my future management strategies.  The majority of my land is oak-hickory-pine forest that is predominantly overcrowded with sweetgums and pines.  I've been slowly thinning the woods with the primary goal being to improve forest health, and secondary goals of transitioning the forest to being principally deciduous and slowly adding food forest trees and shrubs as gaps appear.  I've been cutting down the larger undesirable trees and bringing them to the floor, minimizing damage to desired trees as much as possible with the thought being that the decaying above ground trees will add to the the organic matter of the topsoil, but I'm thinking about modifying this strategy to produce biochar from the pines that are felled for other uses.

There are a few reasons for this - from the research I've done, conifers take significantly longer than hardwoods to decay in a forest setting (See here for models of decay rates of various trees), making them a more obvious candidate than the hardwoods for biochar.  The hardwoods can remain on the forest floor to directly build the topsoil (of which there's only an inch or so), and provide more habitat for fungi.  In my observations, fungi colonize the fallen trees quite quickly, and in areas termites have been assisting as well.  The areas that I've thinned already have a good amount of wood cluttering the floor, so I'm hoping to speed the rate at which it clears up by removing the pines.  Lastly, I'm a one-man operation.  The fewer trees I need to drag out of the woods the better so I can focus on the thinning work instead.

The biochar I'm planning on utilizing for plantings in other areas - gardens and tree plantings in a field that I'm converting to a food forest as well.  From what I've read, biochar is quite effective at improving soil quality in acidic ultisols in tropical regions, so I think the acidic heavy clay ultisol we have in the Piedmont will benefit as well.  One thing that I've been wondering about is application rates.  The rates seem to vary widely depending on the soil type it's applied to, and most recommendations are for extensive field testing in an area before attempting to determine a broad rate of application.  Many of the studies I've read imply that over application of biochar can have negative effects as well.  Does anyone have any experience with this in the Piedmont or surrounding regions?  I'm also curious if people are knowledgable about using pine for biochar - it's been unclear from what I've read if the parent material for biochar has a significant impact on the quality of the biochar itself.

Thanks!
 
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I use any kind of wood, as well as dried weeds, nut shells, any organic woody material.  I haven't noticed any difference in the areas with different types of wood.  I think once all the oils and things are burned out, carbon is carbon.

Application rates is still very much an ongoing topic.  To complicate things further, I have seen growth tests that show some plants grow best at 10% biochar, some at 20%, some at 30%.  The good news is, that unless you are making truly enormous amounts, I think not having enough is going to be a bigger concern than too much.  For a starting point, I think I would try to get to 20%, and maybe test some areas with more.
 
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hau Chris, I do believe that the rates of decay you mentioned for pinus species was for intact trees, which would not particularly be the same for char made from those trees.
Charcoal or better described as pyrolyzed  wood, leaves only the carbon matrix that used to be lignin (the support structures of all plants and trees are made of lignin), and in the carbonized state, the decay rate for any such pyrolyzed wood would be the same no matter the species.

Now if you were doing the partial burn off, such as the way they make the charcoal for BBQ and Grilling, you don't have pyrolyzed wood, you have partially carbonized wood, because there are still many contaminates present, that weren't burnt off in the making of charcoal.
The differentiation is important since charcoal will deteriorate at a faster pace than pyrolyzed woods would, the contaminates are what cause the difference in decay rate.

I would personally take out most all (if not all) of the pines and definitely take out the sweet gums, this will leave you a good hardwood forest, probably with lots of open space between trees or at least a few meadow areas.
I wouldn't worry so much about getting that pyrolyzing heat into the downed wood as much as I'd work to get it all partially burnt, then broken up into small chunks and spread over the soil (the smaller the chunks the better this works).
Once you have the char spread over the ground, you can inoculate with microorganisms with compost additions and or mushroom slurries.
Try to make char additions every year, this isn't necessary but it helps get enough char into the soil so that you can experience the beauty of Terra Preta soil for growing your crops.

The originators of Terra Preta did their char additions over many years, so don't sweat not having enough at the start, just keep plugging along at adding what you can when you can and you will see benefits sooner than later.

Redhawk
 
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I was rather disappointed with the benefits of biochar; like many things, it works well on a small scale, but very hard to scale up. In my case I calculated how much biochar I would need to adequately fertilize (1) 15 acre field I had, and deduced it would take 1600 cords of wood. Just for the record I typed that right...no decimal point is anywhere in that number. One Thousand and Six Hundred Full Size Cords. When I mentioned the staggering amount of wood required to make enough biochar on this site, the consensus was unanimous: scale back, which I could do yes...but...that was just one field...I was scaling back compared to the others I have.

Here in Maine, where back in the olden days we made charcoal for iron smelters, hardwood was always used, and sometimes...but less so...pine. Other softwoods would burn rather than char.

My own tests on making biochar with pine at significant scale (1 full cord) ended dismally. It either fully burned up to ash, or just scorched the blocks of wood, but did not produce biochar.


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[Thumbnail for 22281774_1679958938682852_4582325664220890019_n.jpg]
 
Trace Oswald
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Travis Johnson wrote:
My own tests on making biochar with pine at significant scale (1 full cord) ended dismally. It either fully burned up to ash, or just scorched the blocks of wood, but did not produce biochar.



That is one of the problems I found with making charcoal in an open pit.  Some thing, like pine as you noted, burn up very fast.  It's especially problematic is you have mixed species and use an open burn method of making charcoal.  In a retort it isn't an issue to use pine, but of course, the amounts a person can make at the scale of home-sized equipment is very much reduced.
 
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The main difference you will find in various feedstocks comes out in the mineral content of the biochar. The way to tell is by the relative amounts of ash left behind if they burn completely. Hardwoods tend to have a higher ash fraction, so those chars will be contain more minerals and tend to have a higher pH. Pine and most softwoods have lower mineral content in general, so these chars will be purer carbon and lower pH (but still alkaline in nearly all cases). Straw, bamboo, stover and other grass feestocks produce a char with high mineral content, especially silica. Bone, manures and sludge solids give the lowest carbon and highest mineral chars, with the welcome addition of phosphorus.

I've recreated a table below that summarises some of this. The BC+100 value is the percentage of the black carbon expected to last at least 100 years in soil, and sBC+100 is the amount of that fraction in grams per kg of biochar.



This data comes from Marta Camps' chapter on classification and methods in the book Biochar for Environmental Management published by the International Biochar Institute.
 
Phil Stevens
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If you're having trouble making biochar in a pit, it's usually either a problem with the angle of the sides of the pit or the process. Pit burns are done just like a kontiki...start with small stuff to get the bed of coals established, then add material in sufficient amounts to keep the flame cap, but not so much as to cool the fire and produce smoke. It's an active, hands-on process. If you want to do a large amount of material and not tend it throughout the process, a conservation burn (top lit pile) is probably the way to go. You will only get about half the yield of a pit or kontiki (lots more ash) but you can wander off and do something else until it's quench time.

Also, there is no "right amount" of biochar to add to a field. Even a small amount can make a difference and because it persists, you just keep adding over the years. At farm scales, it would be hard to overdo it.
 
Chris McKenney
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Trace Oswald wrote:
Application rates is still very much an ongoing topic.  To complicate things further, I have seen growth tests that show some plants grow best at 10% biochar, some at 20%, some at 30%.  The good news is, that unless you are making truly enormous amounts, I think not having enough is going to be a bigger concern than too much.  For a starting point, I think I would try to get to 20%, and maybe test some areas with more.



After reading this, I realized I've spent an excessive amount of time trying to figure out application rates by comparing studies, and I think the right approach is more in line with your methods.  Basically I need "a lot".  I'm thinking my approach for my new garden beds will be to do the same prep I have done before, with the addition of broadforking in a lot of biochar from the surface as deeply as I can.  Since I'll be in a position to make additions to several beds over several years, I think that an experimental approach is the way to go rather than try to figure it out from other studies so I can determine what is a good (or good enough) rate.  Basically doing what the literature already says to be doing :)  This may be a good future topic in this forum.

Bryant RedHawk wrote:hau Chris, I do believe that the rates of decay you mentioned for pinus species was for intact trees, which would not particularly be the same for char made from those trees.



Hello Redhawk, I completely agree.  The standpoint I was looking at this from was whether or not to leave the whole pine trees on the forest floor after cutting them down and allowing them to decompose there.  Compared to the sweetgums and other hardwoods that I have been chopping and dropping, the decay rate is slower, and why they're my main candidates for biochar.  The sweetgums may not break down much by the time I want to focus on an area more, necessitating cleanup, but that's fine as I can always turn it into biochar later.

Bryant RedHawk wrote:
Now if you were doing the partial burn off, such as the way they make the charcoal for BBQ and Grilling, you don't have pyrolyzed wood, you have partially carbonized wood, because there are still many contaminates present, that weren't burnt off in the making of charcoal.
The differentiation is important since charcoal will deteriorate at a faster pace than pyrolyzed woods would, the contaminates are what cause the difference in decay rate.
...
I wouldn't worry so much about getting that pyrolyzing heat into the downed wood as much as I'd work to get it all partially burnt, then broken up into small chunks and spread over the soil (the smaller the chunks the better this works).

Once you have the char spread over the ground, you can inoculate with microorganisms with compost additions and or mushroom slurries.



This is interesting.  I've seen a lot of YouTube videos that people describe as making biochar, and the trench method is the one I'm planning on using.  The people there frequently describe "good" biochar as having a non-greasy feel, a sound and brittleness like glass, and completely blackened throughout.  It sounds then like these characteristics alone are not enough to determine if the wood has been fully pyrolyzed, but if this is not vital, I won't worry about getting the higher temperatures for now, but building a retort or TLUD in the future could be a fun project.  I'm planning on innoculating any biochar I create before I spread it, though I have to admit I haven't done much research yet on compost tea or mushroom slurries.  

Travis Johnson wrote:
My own tests on making biochar with pine at significant scale (1 full cord) ended dismally. It either fully burned up to ash, or just scorched the blocks of wood, but did not produce biochar.



Travis, are you sure you're not Mad Max?  That picture is badass - flames and bulldozers go well together.  I'm wondering if the problems you encountered were related to the size of the pieces you were using, some of them look quite large in that photo.  Point taken though - if you need that much biochar to treat a field, producing tons of it just isn't feasible, especially if you'd need to break it down into smaller pieces.  I'll be interested to see what my experience is like with using pine - hopefully it doesn't all burn before I can get it to char.

Phil, that's an interesting chart.  If I'm reading that right, pine's persistance in soil does decrease with lower charring temperatures as Redhawk mentioned, but it still sticks around for quite a while and the difference isn't too great.  What does the class column indicate?
 
Phil Stevens
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Hi Chris - Yes, that's in keeping with what Kola Redhawk says. Lower temperatures leave behind more volatiles and not all the carbon atoms are fused into aromatic rings, so the char breaks down over time. The classes in the table are designations of carbon storage value.

ClasssBC+100 (g/kg)
1< 300
2300-400
3400-500
4500-600
5> 600
 
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I make periodic batches of biochar. I have decided long ago that it is a useful biproduct from brash disposal, but not a product that I would intentionally invest resources (good fuel material, excessive time etc...) if I didn't already have a need to dispose of large amounts of brash. I have had good success with trench burns, based on kontiki type methods - get a good bed of embers going, then add more fuel in layers. The flame front protects the char beneath.

I also found it helpful to cut the material and leave it for at least a few weeks to lose some moisture.
 
Travis Johnson
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In my case I was NOT trying to Trench-Biochar. I was using machinery to do what they used to do in Maine: make charcoal. Back in those days they did so by hand, and my own family tells of making charcoal for the local blacksmith in the early 1800's. It was an interesting reading on how they did it.

I did so with mechanization, but it rather failed.

 
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So if I am understanding this correctly, the pine at 600 C produces the most of the type of char product that persists for more than 100 years in the soil. So the pine that you want to remove, Chris, is about the best source for biochar you could be using, for the purposes of creating long-lasting biochar. Have I read this right?

I was considering the issue of how to best employ limited quantities of biochar. Working small bit by small bit seems to me to be a fine idea, but in my opinion, that approach seems more small-scale agricultural than horticultural.

If I were in such a situation that fertigated (fertilised and irrigated in the same process, I think that's the word they use), as can be seen in some tree growing operations that make use of treated municipal wastewater and treated mixed solids, I would simply add the biochar to the part of the process after the harmful pathogens have been eliminated, and the mix was being swirled in a vortex and bubbled.

Even if I wasn't fertigating, I would still be applying fungal slurries and compost extracts to soils at need, so the biochar would be applied to the compost extracts during the brew, and would make its way into the soil that way.

I have often thought that in producing fungal slurries and compost extracts, that unless I scale up, I will always be trying to maximise the impact of too little compost extract, fungal slurry, and biochar on too much land. I figured the way that I would handle this is by amending swales and woodchip access paths that would act as such. In that way, in putting those good things in places where, at the driest, least hospitable times of the year, those places, deep down and buried by a wood chip and biochar sponge would still be hydrated and hospitable to soil life, we put beneficial soil life in a situation where it can best perpetuate itself, and grow. I often refer to structures such as these as soil life bioreactors. They have the effect of nurturing healthy populations of the soil life we want to encourage in the soil, those organisms that go out and work the soil for us so we don't have to.

The benefit of this approach on broad-acre permaculture of any kind is that you're setting in place a self-sustaining system. Set-it-and-forget-it soil healing. And every time it rains, the soil downplume of you gets a fresh dose of healthy microbiota.

I was thinking, also, that for me, inoculating well-made charcoal to produce biochar wouldn't involve a separation from my compost, because what would be the point? So if I am adding compost, either to potting mixes for seedlings, or top-dressing new plantings, or to a new or refurbished bed, that's another vector for getting the biochar where we want it.

I just had one further thought about swales and biochar distribution. Let's stack functions. So you have these swales with the slight berm downslope, right? You have seasonal rain events that flood them, and though you've designed them to be level, you constantly monitor them for erosion, as any good land steward does.

So why not top those berms with a biochar-heavy compost mix, or place them just behind the berm, so that the seasonal rains can do the work of spreading your biochar for you? This certainly wouldn't work in all situations, but if the swales are designed for the water to top them evenly, a loose topping of composty biochar would quickly become mobile, and would be spread over the surface of the soil, accumulating at any sediment-trapping feature, such as another swale, or specifically arranged sediment traps as simple as fallen tree limbs placed on-contour.

This would have the added effect of making it visibly obvious wherever there was erosion, making problem spots easier to spot, track, and manage.

Stepping back a bit, I think I would be combining the brewing of compost extract and the inoculation of my charcoal into a single step. It would therefore follow that I would be applying my biochar with my compost extract, whatever the specifics of the infrastructure on the ground. I would still try to inoculate wet areas first, to act as microbiological oases.

If I was producing truly large amounts of charcoal, too large to crush down and inoculate with the actively aerated compost extract in the tank, I was thinking about treating it as woodchips, perhaps mixing them, even. That would offer a lot of microbiological edge habitat between food, being the woodchips, and housing, being the biochar, and virtually any amount sitting in healthy soil will become inoculated, so treating charcoal with compost extract, itself brewed with a significant portion of biochar, would bring the tenants to the housing all the faster, with food in place and plenty of room to spread out and multiply.

I like the kon-tiki-style of biochar production, but what I really want to do is to convert an old propane storage tank into a retort for use in situations such as waste heat streams, such as that from a glass furnace, say. I would valve the thing for the collection or redirection and combustion of wood gas, and probably sit it inside a suitably large shipping container converted to act as an alternate ending to the exhaust stream, on tracks so that a tractor could be used to pull it out and manipulate it. I would cut one end off and hinge it as a door, and I would make it swing clear, such that once removed from the outer retort, the sealed end of the tank could be raised mechanically to dump out the finished charcoal.

Yes, I am suggesting the construction of a retort just large enough to fill a shipping container, powered by the waste heat of a glass furnace or other industrial process. I think this is the scale that you'd be looking at if we are talking about broad-acre application in a forest management setting. Of course, I will be scaling it to the availability of raw materials for conversion, so maybe I will work up to the shipping container-sized tank.

-CK
 
Bryant RedHawk
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I have used and really like the TLUD over the retort furnace for making char and charcoal.
I use pine charcoal in my forge for making Japanese steel edged items.

I am preparing to do a recreation burn for an addition to the Terra Preta I am making as part of a study on this type of amended soil.
One of the parameters of this study is to find out how well the fungal network responds when it encounters Terra Preta.

I am interested in your retort project Chris, let me know how it goes along please.

Redhawk
 
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Last Friday I made about a cubic yard of pine/spruce/fir char in three hours just burning it up on flat ground. Only rule to remember is "when any part of the coals start to turn white, cover it with another piece of wood." Spray it out real good when you're done, rake it back and forth to make sure there aren't any parts still burning. When the pile stops steaming drive back and forth over it with a truck until it's finely crushed.

This method works good and you can avoid the embarrassment of having to explain that that hulking rusted out metal wreckage making your yard look all Mad Max is "actually a charcoal kiln"
 
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My own property is 99% pines right now, and my plan is to trim off the branches when I fell trees for a wofati, and that following winter burn the branches with the target of creating biochar for my first garden the following spring. I dropped a few very small pines (like 2-3" diameter, 15' tall) that were overcrowding a parent tree, and after 18 months most still have all their needles still, let alone any decay of the wood. So the biochar route seems like the way to go there. Next step is convincing the neighbors to let me haul away their slash piles instead of burning them!
 
Travis Johnson
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Mark Brunnr wrote:My own property is 99% pines right now, and my plan is to trim off the branches when I fell trees for a wofati, and that following winter burn the branches with the target of creating biochar for my first garden the following spring. I dropped a few very small pines (like 2-3" diameter, 15' tall) that were overcrowding a parent tree, and after 18 months most still have all their needles still, let alone any decay of the wood. So the biochar route seems like the way to go there. Next step is convincing the neighbors to let me haul away their slash piles instead of burning them!



If you lived closer, you could have any one of my three slash piles: one is bigger than my house. I do plan on burning them, but it will be this winter, and when I do, I am pretty sure you could see them from space.
 
Chris Kott
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I have another dumb question.

What if you took waste cardboard and layered it thickly overtop of a slash pile, wetting it or letting it get rained on to make it quasi air-tight? And then, what if it was top-lit at a hole at the top of the pile? It could be done after a snow or two, such that the melting snow keeps hot cardboard from burning. The snow could actively be shoveled up if it helped, in fact.

-CK
 
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