Experimental Homestead

Experimenting with Biochar: pursuing the promise of charcoal as a soil ammendment

char header



I have this neighbor up here.  He’s always saying sustainability and permaculture and stuff like that, but I was surprised in a recent conversation to find out that he did not know the term, or concept of, biochar.  For others who don’t know, that’s a catchy marketable name for charcoal that is intended as a soil amendment, the claimed benefits of which I’ll delve into further on.  I’m not even sure I like the term biochar.  Why name something that already has a name?  Maybe so you can market it?  Charcoal with special properties?  Anyway, I guess I thought it was more in peoples consciousness than it probably is, and since my sustainably hip neighbor was unfamiliar with the concept, I got to wondering how many other people haven’t yet encountered the concept and thought I’d present some thoughts and information here in case I might be able to convince more folks to delve into experimenting with the idea.

I had seen some interesting, and even exciting, articles and videos on using charcoal as a soil amendment.  But, all the references were based on the discovery of terra preta, which are these human modified soils in the Amazon containing a large amount of charcoal.  The claim is that these soils are still highly fertile compared to the natural soils surrounding them, even after many hundreds of years of heavy Amazonian rains.  The mysteries of terra preta are still being prodded and examined, but clearly charcoal is a major player, and likely the key ingredient.  If it functions as advertised, adding char is a permanent improvement, unlike the treadmill of organic matter and nutrients that we add to our soils every year and which mostly flush away in the rain.  I’ve seen what happens to gardens when they are abandoned.  The fertility quickly declines remarkably fast and eventually disappears.  The possibility of making really permanent improvement to gardens, orchards and pastures is very compelling and worth some great effort.

Having trained myself to be somewhat cautious and critical of new and exciting ideas, I was naturally slow to adopt.  I was very interested though and began to save any charcoal I could for experimenting.  One day while researching heirloom apples, I found a 19th century reference to using charcoal in potting soil, which gave me the idea to search google books for the terms – charcoal fertilizer – ,.  I limited the search to the 19th century.  Bingo!  I found a bunch of very interesting references. Now that I had something besides the much recycled terra preta hype to fuel me, I was much more excited to experiment.  If you haven’t read that post, you totally should.  It’s quite fascinating.  You can skip my usual rambling and go straight to the accounts.  Biochar use in Europe and North America in the 19th century.  Since most of you won’t actually click the link and read it, here is a tasty extract…


The Farmers’ cabinet, and American herd-book, Volume 11
From the Farmer and Mechanic
Comparative Merits of Charcoal and Barn-yard Manure as Fertilizers.
In the year 1788, my father purchased and removed upon the tract of land in Hanover township, Morris county, N. J. The land, owing to the bad system of cultivation then prevailing, was completely exhausted, and the buildings and fences in a state of dilapidation. The foundation of the barn was buried several feet beneath a pile of manure, the accumulation of years: little or none ever having been removed upon the lands. Even the cellar, beneath the farm-house, was half filled with the dung of sheep and other animals, which had been sheltered in it. The former occupant of the farm had abandoned it on account of its supposed sterility, and taken up the line of march for the Valley of the Miami, along with the first caravan of pioneers who accompanied Judge Symmes.

The barn, before referred to, was removed to another situation soon after its foundation was uncovered, by the removal of the manure to the exhausted fields; and its site,
owing to the new arrangements of the farm, became the centre of one of its enclosures. During the seventeen years which I afterwards remained upon the farm, the spot could easily be found by the luxuriousness of the grass, or other crops growing thereon; though the abatement in its fertility was evident and rapid. On revisiting the neighbourhood in the autumn of 1817, I carefully examined the corn crops then standing upon the spot, and was unable to discover the slightest difference in the growth or product, upon that and other parts of the field. This was about twenty-eight years after the removal of the barn.

Upon the same farm and upon soil every way inferior, were the remains of several pit-bottoms, where charcoal had been burned before the recollection of any person now in the vicinity, and most probably, judging from appearances, between the years 1760-70. These pit-bottoms were always clothed, when in pasture, with a luxuriant covering of grass, and when brought under tillage, with heavy crops of grain. Eleven years ago I pointed out these facts to the present occupant, and his observations since, coincide with my own, previously made; that they retain their fertility, very little impaired, a period probably of about seventy or eighty, certainly not less than sixty-five or seventy years.
Here then is an excellent opportunity of observing the comparative value of charcoal and barn-yard manures, as a fertilizer of lands. The former has not, after at least sixty or seventy years exposure, exhausted its powers of production, while the latter lost its influence entirely in twenty-eight years, and most probably in much less time.

I have since had many opportunities of’ observing the effects of charcoal left in pitbottoms, upon vegetation, one of which only,. I will relate. The last season, in the northern part of Ohio, was one of uncommon frost and drought . In May, the wheat fields, when promising a luxuriant crop, were cut off by frost;—especially in the valleys, and very much injured in the high lands—which was succeeded by the most severe drought ever experienced in the West. The moiety which escaped both these scourges, was afterwards very much injured by rust. Near the village of Canton, upon a farm on high ground, which had been mostly cleared of its timber by its conversion into charcoal, it was observed that upon the old pit-bottoms, the wheat grew very luxuriantly—was clear of rust—and had ripened plump in the berry; while in the adjacent parts of the field it was short in growth, the stem blackened with rust, and the berry light and shrivelled.”

All the results are definitely not in on using charcoal as a soil amendment.  It is being sold as a panacea for the ills of the planet and human society, and large corporate interests are even becoming involved.  The biggest claim is that charring gajillions of tons of woody debris and burying it can help mitigate climate change.  About half of the carbon in woody material can be converted into charcoal, an extremely durable material capable, at least in some cases, of residing in the soil for thousands of years.  Not only that, but if that buried charcoal increases plant growth and fertility, as it is claimed, the extra abundant growth on previously less fertile soil will absorb even more carbon which could then be charred as well.  If the wood decays naturally, little of the carbon remains in the soil, but instead ends up back in the atmosphere.  While it seems hard to believe we could char our way out of the enormous quantities of carbon we’ve released in the last 00 years of so of burning fossil fuels, that is the hopeful claim of many biochar champions.  Other claims, relevant to us as gardeners, are increased water retention in the soil, reduced leaching of nutrients (because they bind strongly to the charcoal which is a virtual magnet for all types of substances) and therefore a decreased reliance on fertilizers, better and earlier soil warming, and Increased microbial activity (the miles of pore space and surface area in a piece of charcoal, rich with absorbed nutrients, providing a huge habitat for living things.).  One issue though, is how char will work when applied to differing soils in various climates.  The truth is that there is a lot we don’t know about the practical applications and benefits under varying circumstances. carefully designed long term studies might help, but If we wait for science, and possibly more relevant, its interpreters, we may be disappointed or behind the curve.  Besides, there are so many climatic/gardening style/fertilizer and soil type factors to account for.  You and I only have one agenda, to see if the stuff works in our soils and gardens.  I suspect that it will work for some of us, so lets just find out on our own.  It’s not really that hard to just try the idea out in small areas.  If charcoal amended areas of our garden consistently grow the giganticest healthiest plants ever, that’s probably a green light to keep burying charcoal.

The first idea I was able to reject in order to move on was the idea that I needed special charcoal, burned in a special way.  The 19th century references were using whatever charcoal was available.  Most of it was probably slow burned in piles since that was the common method, but I feel pretty sure that whatever charcoal we can come up with is probably worth trying, even if it isn’t ideal, (which I’ve seen no compelling evidence so far to say it’s not.  Not that I’ve looked very hard).  It takes a lot of charcoal to reach a soil content of 10% in a significantly large area.  Save charcoal wherever you can get it.  Avoid the moulded “charcoal” briquets that people use to barbeque.  Those are made with coal and are actually “coke” briquets (coke is the term for the equivalent of charcoal made from coal).  I have been partially successful at convincing others around here to save the charcoal from the woodstove every morning, which adds up over a winter.  I also collect it from campfires and burnpiles.  Once a burn pile is down to just embers, it can be spread out and/or doused with water to prevent the charcoal from burning all the way down to ash.

this picture is just to keep you interested in case you have a short attention span ;)

this picture is just to keep you interested in case you have a short attention span ;)

I’m also planning to produce charcoal intentionally.  I have this friend that is always telling me about the newest best thing ever.  Biochar is one of them.  While this guy is much less cautious than me in accepting an idea as worth pursuing, while I was still getting excited about biochar, he was making 17 yards in one winter!  The guy gets mad respect for GSD (getting shit done) and pursuing his goals for self reliance.  Charcoal has traditionally been a very polluting activity producing enormous quantities of very dirty smoke.  This friend burns his in a barrel with a flue on top, which burns much cleaner than traditional methods of smothering.  He learned the method from this video.  The technique could no doubt be refined, but it is where I’ll be starting.  I’m also hoping to adapt the same kiln for lime burning, or making char and sea shell lime at the same time.  My friend added a fan which feeds into the bottom of the barrel.  Most other methods burn up some fuel all the way to ash in order to make the charcoal, but this kiln achieves two very important goals relatively well, efficient fuel use and low emissions.  I have some barrels and, time and energy permitting, I’ll be setting up a couple of these kilns and charring some wood chips.

My soil amending experiments have just begun.  This spring I ground up and buried some charcoal in a garden bed.  I divided this long bed into three 7 foot long sections.  Section one has about 10% charcoal in the top 10 inches of soil.  Section two has 5% and section three has none.  It is generally said that a certain percentage is required to start seeing real benefits, so adding a quantity to a small area rather than just spreading it out over a whole bed or garden seems like the way to go.  Some say that the charcoal should be pre-charged with nutrients because it is so adsorptive of plant foods that it will deplete the soil at first until an equilibrium is achieved.  I chose not to pre-charge to see what would happen, and so I could treat the control section the same as the charcoal sections.  I also dug the no-char section just the same as the other two sections, even going so far as to go through the same motion of sifting in the char that wasn’t there.  I did add a sprinkling of woodash to the no-char section to try to imitate the small amount of ash present in the pulverized charcoal.

2x4's are use to roughly measure the depth of the charcoal.

2×4’s are use to roughly measure the depth of the charcoal.

char spread out

Char laid out before being dug into the soil. It was sifted in with a digging fork to about 12 inches. The control section of the bed with on charcoal was treated exactly the same, down to the sifting motion, except a small amount of wood ash was added to simulate the small amount of wood ash in the charcoal.

This experimental bed was planted to peas, spinach and lettuce, with the rows running the full length of the bed.  At first things grew well, but as time went on, it was apparent that the more charcoal there was in the soil, the less the lettuce and spinach grew.  The 10% charcoal end of the bed was a total loss as far as lettuce goes.  The Peas did okay through the whole bed, but not great.  It was difficult to discern much difference, but that was complicated by part of the pea row being attacked by birds and bugs.  Anyway, it appears that it is probably true that the charcoal should be pre-charged or it will sap the soil of nutrients in the beginning.  I would probably charge by mixing with compost or soaking in compost tea, except that sort of screws up the experiment of doing the same thing to all areas of the bed except for the charcoal content.

Although I’m very excited about biochar and plan to scale up production and experiments, I will approach it somewhat cautiously at first since it is a permanent addition and can’t be undone.  I will continue to plant primarily test plots as outlined above, but with variations in depth and quantity of charcoal.  Next I’d like to do a bed that has charcoal at varying quantity, up to 20%, but 24 inches deep instead of 12, and one with the same quantity of charcoal in each section, but dug in to various depths.  I also plan to bury some in the meadow to see the long term effects there.  finally, I’d like to see what happens if I just throw the stuff down on the meadow without burying it.  I plan to do dug control plots in all cases, because that eliminates the possibility that it is just the act of digging that is making a difference.  These few simple tests should yield up some fundamental information that can tell me whether to proceed to char everything I can get my hands on, or spend my time on something else.

If you can collect charcoal from burn piles, campfires or the woodstove, it doesn’t take all that much to put together a very small test plot.  It probably should be used in adequate quantity per area.  10% would be something around one and a half inches deep dug into 12 inches of soil.  I’m mostly planning to use 5%, 10% and 20%.  Grinding the charcoal can be a problem.  I have been using an old corn, bone and shell mill that someone gave me.  It grinds the charcoal to pea sized and down, which is what I decided I want for now, though it could be adjusted finer or coarser.  I’m tempted to do some tests with various sized grinds, and probably will eventually.  a hammer mill of the garden variety chipper shredder type would probably work and I’ve thought about running it over with a car or a heavy roller of some kind.

The Enterprise corn, bone and shell grinder in use for grinding oyster shells. Works great for charcoal.

The Enterprise corn, bone and shell grinder in use for grinding oyster shells. Works great for charcoal.

My first experimental bed is now planted to leeks for the winter as it’s second crop.  I’ll continue to plant the whole bed uniformly to the same crops for comparison, and I hope by next growing season to be able to discern any obvious effects.  When you realize how much charcoal it actually takes to amend 100 square feet at even just 5%, you may be discouraged, but remember that this is potentially a permanent soil improvement.  Remember too that It can also be done in small sections as charcoal becomes available, so there is not necessarily a need for a heroic effort.  If it really is as useful as we all hope, it is also quite possible that it will be worth buying the charcoal if need be, though it seems ideal to figure out how we can char whatever debris we might have on the home place, including crop wastes.  Since the process produces quite a lot of heat, there seems to be great potential for working charring into home systems.  For instance one could potentially heat water, boil bark for tanning skins, make lime, cook, can food, dry food, heat greenhouses, heat living spaces, etc… all while producing char.  The trick is going to be figuring out char producing stoves and kilns of various kinds for these purposes, which use the fuel sizes and shapes that we have available.  Once that is figured out though, charring, rather than being an extra job will be integrated into homestead life.  That’s a pretty neat vision.


October 16, 2013 - Posted by | Garden Stuff | , ,


  1. Hey Steven, really enjoyed reading your thoughts on charcoal. I heard of a guy recently, over here in the UK who’s been making biochar rocket stoves to combine heating and charcoal production like you mentioned. You might be interested to check out his site, and i’m sure you could contact him for more info if you wished. http://www.soil-carbon-regeneration.co.uk/biochar/instructions/biochar-rocket-building-instructions/
    All the best, Chris

    Comment by chrissfoodjourneys | October 17, 2013 | Reply

    • Thanks Chris, that looks really neat. That whole realm of integrated char production seems like the next step for sure. Such a waste to produce all that heat making char and not use it for something. I just canned tomatoes last night in the mega canner and I could have producing char instead of ash if I had something like this together. Also, if a person is already cooking, heating water, etc… then it’s not an extra job so much as just life. Even small amounts of charcoal add up over time. Hopefully there will be some great innovations coming out. It seems like there are a lot of possibilities with the TLUD concept. I’ll be talking about that briefly in my upcoming lime burning post, though it is mostly theoretical at this point. One stumbling block is fuel size. Lots of gasifier type designs require a feedstock of uniform size.

      Comment by Stevene | October 17, 2013 | Reply

  2. HI,

    I really appreciate your article on biochar. I’d like to add a few comments. You are right about using any charcoal. There are articles that biochar must be made in a special way. Biochar is essentially a mechanical process depending on the huge amount of surface area in the char ( a teaspoon contains an estimated acre of surface area). Biochar made in the most effective process (proper temperature, etc.) is indeed more effective but the percentage improvement is so small, who cares! There are two additional elements that I think are important to know. Biochar adsorbs the nutrients already in the soil and stores them till the plants need them. This makes biochar especially effective in sandy soil where the nutrients are readily washed away by rainfall. Not only are the nutrients stored but, since they aren’t being washed away, this has a greatly reduces the polution in surface water. In addition, the pores in the biochar fill with water and serve as a reservoir of moisture. But, due to these two conditions, if “raw” biochar is worked into soil, you can actually go backward with your plants at first due to nutrient and moisture starvation. To compensate for this, we “charge” the biochar before using it. This is a simple procedure where the biochar is put in a bucket and covered with water with a soluble fertilizer in it (I use fish emulsion). Let it stand for about a week and add water if needed to keep the biochar covered. The second comment is that a commonly disregarded effect that biochar has is to significantly promote soil microorganisms. Albert Bates who wrote “The Biochar Solution” says “when microorganisms find biochar in the soil, it’s like they’ve found a luxury condominium”. Soil microorganisms have been shown to be extremely important in the uptake of nutrients by plants. With all these conditions, biochar cannot be expected to provide immediate improvement. It takes biochar about 6 months to get fully conditioned to the soil it’s in, but, from then, it does it’s thing essential “forever”.

    Comment by Wae Nelson | October 17, 2013 | Reply

    • Thanks very much for your thoughtful comments. All that sounds pretty much in line with what I’ve read, thought and suspected. I have a fairly high rainfall with not sandy, but light soils. They are acidic from calcium leaching, so stopping those nutrients from leaching out is pretty compelling. The reasons I didn’t pre-charge are two. First, some of the 19th century accounts report good results with raw charcoal. I just wanted to see if I really needed to go through the trouble. It has occured to me though, that those guys were often collecting charcoal from forges and steel works and such, free for the hauling. In that case, it is quite possible that the stuff was adsorbing a great deal of goodies from just being outside and being rained on etc. I think one of the old accounts I found mentions that plants could be grown in pure charcoal as long as it was watered with rain water, but the plants would not grow with distilled water. That would be a neat experiment to try.

      Reason two is that it would be difficult to treat the control bed the same if pre-charging the charcoal. Perhaps mixing the charcoal with a given amount of moistened compost for a few weeks, and adding an equal amount of compost to the control bed would work. It was a good learning experience. The nutrient deficit was very obvious. The lettuce crop in the 10% char section was a complete loss as far as any of them heading up or growing significantly large. I thought I took pictures, but I can’t find them. Either way, I can either accept the 6 month to a year non-productive period if I have to, or I’ll try a charge of known quantity relative to the control area of the bed. It’s not a very good control, but I’m not after pure science here. I think good enough is good enough when observing over years, which is really my goal. My additions to the beds are not measured either. I just put roughly the same treatment to the whole bed when fertilizing. If I can put in say three of these test beds and the results are obvious over a few years, that’s certainly good enough for me to go on ahead.

      Comment by Stevene | October 17, 2013 | Reply

      • One of the accepted means of “charging” biochar is to add it to a compost pile as it’s being constructed. Once the pile has finished, the biochar has been charged and inoculated with microorganisms. When the compost is added to the soil, you’re adding biochar as well.

        Comment by Wae Nelson | October 23, 2013

    • Do you have any ideas for simple home char grinding? I feel like this is a major stumbling block for home scale experimenters. I was lucky to have this grinder. Also, any thoughts on particle size? My thought is sort of the finer the better, but not everyone seems to agree.

      Comment by Stevene | October 17, 2013 | Reply

      • Hi Stevene,

        I “grind” my lump charcoal by putting it in a cloth bag of some kind (burlap, pillow case, etc.) and drive over it with the wheel of my car several times. Sometimes there are still pieces remaining that are still too large. In that case, I feel through the bag to find them and smack them with a large rubber mallet I got at Home Depot for about $3. My recommendation for size is “rule of thumb” which is nothing larger than the first joint of my thumb.

        Comment by Wae Nelson | October 23, 2013

  3. I love the fix to the grinder. :D

    I understand the concerns about nutrient uptake by the char at first. If one were not running an experiment I begin to wonder if it might not be a bettter, long-term, practice that char was put in the worm bin, or laid down in a thin layer with compost on top in the fall just before fallow season etc. Take a few pieces out of the wood stove and throw them in the bokashi bucket, etc. etc. Pick your poison in this case.

    I wouldn’t aim for 10% up front in that case but 10 or 20% over the course of 5 years. Not that one wants to go 5 years for the “teh awesome” gardening answer but because then it becomes a regular regeneration practice, less likely to be forgotten or overlooked by new gardeners if it is a “mix char with compost and lay it down in the fall” sort of “best practices” that we figure out and begint to suggest to others.

    Just thoughts.

    I look forward to reading about your experiements this next year.

    Comment by c. | October 17, 2013 | Reply

    • I was meaning to fix that grinder forever. It’s really nice. It grinds raw oyster shells pretty well and charcoal great. It has some seized parts, so it’s not adjustable, and a bit of a project. Just happens to be stuck on a setting that grinds charcoal pea sized and down, which is what I decided to start with. I was glad to find it works well enough with the C clamp, but still hoping to pimp it out someday with paint and everything.

      For home gardeners, urine would probably be perfect for inoculation. I see a little bit of an issue with figuring out how to work in small amounts, while being sure you end up with enough in each area, or knowing how much has been added. If I added it just to my compost, it would be a long time until it built up enough to start making a difference. I guess I was thinking that I should get it over with for each bed and then move on to the next, so I know what is and isn’t done and so at least some of the garden is up to full speed. I see your point though.

      Comment by Stevene | October 17, 2013 | Reply

  4. Earlier this year I had the chance to make biochar using a japanese cone kiln. It’s a very simple and portable design, basically a metal cone that’s open on either end, with the smaller end sitting on the ground. They come in various sizes, this one was about three feet across on top and one foot on the bottom, about a foot and half tall. I can’t find the exact dimensions right now. I’ve heard there’s traditionally a smaller one and a much larger one. It seemed to be extremely efficient and fast. In two hours of burning we converted two wheelbarrow loads of split wood into one wheelbarrow plus one 5 gallon bucket full of charcoal. In total it filled six buckets full, so we made around 30 gallons. There was only a handful of incompletely burned material and barely any ash. Granted the wood was extremely dry and there would be more waste with wetter wood. I tried replicating the cone kiln with a pit I dug and the results weren’t nearly as good, but I was using much wetter wood. I still got a decent amount of wood. The person whose kiln it was has experimented with many different kilns over the years, and thought this one was the most efficient and user friendly of all, both in terms of time spent and material used.

    Comment by Lars | October 23, 2013 | Reply

    • Thanks for sharing that Lars. They look easy to make with some scrap sheet metal and rivets. I like systems that don’t burn up a lot of extra fuel to produce the charcoal, and create little smoke. Those are two of my primary design goals. This looks like it probably fits those two. I like your equivalent shaped pit idea too. Having dryish ground and dryish wood does seem likely to be important though. If it was used regularly, maybe it would be worth lining with brick or something. I’ve used a rectangular pit and then quenched or covered it with soil or sheet metal, but it was never very efficient and tons of smoke.

      Comment by Stevene | October 23, 2013 | Reply

      • Actually, as a permanent set up if the cone does work really well, one could do a raised pit, completely above ground level lined with brick. If the medium was well drained, it would always be dry enough to burn. That’s an issue here where we can’t burn anything in the dry season. A stainless version would last a really long time though. I wonder if there would be any significant advantage or disadvantage to having some mass in the walls from bricks.

        Comment by Stevene | October 23, 2013

  5. I love the cone kiln suggestion. Enough to get me thinking about how it could be used as a firepit in the city and then put away to keep theft away. (Always dealing with local conditions.)

    I was thinking about sourcing a grinder of some sort and the closest I came to a solution was to look for what potters use to grind up old pottery into grog. I figured the texture/hardness of material would be in the same range as biochar.

    Hammermill, grist mill, and corn grinder were all mentioned here:


    I’ll have to run over and have a gander at our local potters and see what they’ve sourced for their studios and if they’ve any better ideas.

    Comment by c | October 23, 2013 | Reply

    • Grinding is a bit of a hurdle for sure. I think driving over it with a car is worth experimenting. You’d have to put the char in a durable tarp of some kind first, and then still sift it, but if nothing else was available… Even walking over a tarp full of char habitually, like in a pathway, seems worth a try. I think a hammermill type yard shredder should be great. I’ve got one that needs a motor or drive of some kind. I’ll probably use the PTO on the little tractor here. I want it to chip bark for tanning skins anyway. I ground about 8 or 10 gallons of charcoal today by hand in the Enterprise 750 corn, bone and shell grinder. It is slow and the pieces have to be broken down to an inch or less or they will often clog the hopper. Breaking up the pieces keeps my occupied while grinding though. I probably ground for an hour or an hour and a half, maybe even two. It’s good exercise though and it’s not hard at all. The intertia of the pretty heavy flywheel really makes a big difference. It could easily be hooked up as a motor. The fly wheel is cast with a crown, probably to take a flat belt.

      The fire pit idea is pretty intriguing. If it really doesn’t smoke too much.

      Comment by Stevene | October 23, 2013 | Reply

  6. […] on my list until last week, when I looked at the latest post by one of my recommended blogs: Turkeysong. I’ve been interested in biochar for awhile, but figured I needed to acquire–more […]

    Pingback by Breaking Through the Gloom | astroplethorama | October 25, 2013 | Reply

  7. My friend and fellow Biocharist Chuck Gay takes a barrel of char and fills it with water, then runs it through his limb chipper. The water prevents loss of the fines. In Utah we are making char with a portable pyrolysis kiln that also makes bio oil.

    Comment by Darren McAvoy | November 1, 2013 | Reply

    • I have usually dampened my char before grinding, just to cut down on the dust. My grinder works better though if it’s dry, so I’ve just started wearing a dust mask. Some fines are lost, but not that much, that probably nothing compared to a chipper. I’m sure there are all kinds of cool things going on with different burning methods and experiments out there. I haven’t spent a ton of time yet trying to sift through it all yet. Looks like some useful links in the UBRG presentations page. I’m glad there are people out there working on some of the problems that need solving. I’m interested in more sophisticated systems, and in wood vinegar, but I’m also really interested in accessibility and simplicity.

      Comment by Stevene | November 1, 2013 | Reply

  8. Hey, Steven, I’ve just been loading my wet char (from the end of the burn in a wood-fired oven, mostly) into a shallow metal pan or an empty wheelbarrow and pounding it w/a homemade tamper (a 4″ log whittled down to make a nice handle — a 2×4 would work, tho). It doesn’t take long, and it’s pretty fine and consistent. Good job for the ten year old boy, too… Then I toss it in an old barrel, cover w/pee, and when the barrel is full I spread it. I’d like to be making more, but there’s too much else to do!

    Re: the notion of char-making and climate change, Albert Bates put me onto an interesting (long and detailed) article from the Annals of the Association of American Geographers: The Columbian Encounter and the Little Ice Age: Abrupt Land Use: Change, Fire, and Greenhouse Forcing, by Robert A. Dull; Richard J. Nevel; William I. Woods; Dennis K. Bird; Shiri Avnery; William M. Denevan. Here’s the abstract: “Pre-Columbian farmers of the Neotropical lowlands numbered an estimated 25 million by 1492, with at least 80 percent living within forest biomes. It is now well established that significant areas of Neotropical forests were cleared and burned to facilitate agricultural activities before the arrival of Europeans. Paleoecological and archaeological evidence shows that demographic pressure on forest resources—facilitated by anthropogenic burning—increased steadily throughout the Late Holocene, peaking when Europeans arrived in the late fifteenth century. The introduction of Old World diseases led to recurrent epidemics and resulted in an unprecedented population crash throughout the Neotropics. The rapid demographic collapse was mostly complete by 1650, by which time it is estimated that about 95 percent of all indigenous inhabitants of the region had perished. We review fire history records from throughout the Neotropical lowlands and report new high-resolution charcoal records and demographic estimates that together support the idea that the Neotropical lowlands went from being a net source of CO2 to the atmosphere before Columbus to a net carbon sink for several centuries following the Columbian encounter. We argue that the regrowth of Neotropical forests following the Columbian encounter led to terrestrial biospheric carbon sequestration on the order of 2 to 5 Pg C, thereby contributing to the well documented decrease in atmospheric CO2 recorded in Antarctic ice cores from about 1500 through 1750, a trend previously attributed exclusively to decreases in solar irradiance and an increase in global volcanic activity. We conclude that the post-Columbian carbon sequestration event was a significant forcing mechanism of Little Ice Age cooling.”

    Others apparently suggest that the burning required to clear neotropical forests may have contributed to a warming trend that helped push the moors into Spain, which helped fuel the cultural developments that helped fuel the “Columbian Encounter.” If so, what an amazing story!

    I’ve been enjoying all your posts. Thanks!

    — Kiko Denzer

    Comment by kiko denzer | November 5, 2013 | Reply

    • Thanks for that Kiko. That theory has to be based on parsing a whole lot of data. Hard for me to put my faith in scientists to interpret that much information. Interesting idea, but I remain skeptical.

      I actually just had the idea to run char through the garbage disposal that I use for grinding apples sometimes. It’s basically a hammer mill of sorts with little spinning chunks of stainless steel which bash things to pieces. The one I have is a full horsepower motor, so it does some damage to apples. It overheats, but i think a fan will take care of that. dealing with dust would be an issue, but maybe it will go through damp or even wet. I had thought of making something like what you describe using a 5 gallon bucket as a sort of mortar. Glad to hear that works. I was just reading a great thread over on the yahoo biochar list that made me want to grind finer. My initial intuition was to grind fine, and some of this stuff reinforces that inclination. Also, the thread is about the Japanese cone kiln that Lars already mentioned, which definitely check that concept out if you haven’t. I’m thinking of the same thing, but long for burning long branches.

      I’m envisioning lately a fast straw clay kiln slapped together for just one or a few uses (even quicker and dirtier than the pets). Fire from the top with mixed layers of wood and shells or small limestone. Extinguished early to collect char, slake the lime, and pulverize the whole lot, kiln, and all for soil improvement. It’s quite a bit of work, but potentially a long term investment. Won’t know if it works till I try it.

      Comment by Stevene | November 5, 2013 | Reply

  9. Experiment with the cone kiln concept. […] the comments on the biochar experiment post, Lars mentioned Japanese cone kilns.  I checked them out on Kelpie’s cool blog, Green Your […]

    Pingback by Japanese California Cone Pit Charcoal Kiln Agave Roast! « Turkeysong | December 22, 2013 | Reply

  10. […] to permanently improve soils.  If you’re not familiar with that idea, a little research on biochar might be helpful. […]

    Pingback by Proposal For a Moveable Soil Improvement Oriented Latrine System Using Biochar « Turkeysong | July 29, 2014 | Reply

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