Posts filed under BioChar

What to Do With Those Axe Cut Woodchips? The Burning Question

One of the most common questions, if not the most common question on my axe related content is some combination of what do you do with the chips, aren't they wasteful compared to a saw and wouldn't it be better to just use a saw.  The video below is about that and what we can do with the chips which are quite useful for anyone with a garden or who burns wood.  Below that are some further thoughts not really covered in this video.

What I covered in that video was, in short, yes there are a lot of wood chips produced when processing wood with an axe.  This tree was probably 9 inches in diameter and I estimated about two good firewood logs worth of chips were produced.  It takes under 5 minutes to pick up 80% or more, in this case 3.5 minutes.  I talked about what you can use them for, like biochar, mushroom growing and fuel, and how whether it is viewed as wasteful or not is a matter of context.  What I didn't really talk about is why some of us use axes and not saws for hand processing firewood. 

I didn't talk about that, because I more or less just forgot to!  I think that in my head it would be self evident that not I, nor anyone else, is using an axe because it is the quickest and most efficient method of firewood production.  I like saws.  I like my chainsaw.  I'll be using my chainsaw a lot for processing wood this year, not because I need the wood, but because I need to deal with a lot of sick trees that will soon be a fire hazard and which represent a short term opportunity to gather some resources that will soon be unavailable.

But, when I set out to do the cordwood challenge myself the previous season, challenging myself to cut a cord of wood in 3 months, I was slightly wary.  Before committing I think I went and cut up a small tree or two just to be sure I should be announcing to the entire internet that I was going to go for it.  Aside from potential personal limitations though, I knew I could do it, because people used to do it.  Dudley cook said in The Axe Book, that a good axeman could put up 2 cords a day!  I knew the cord he was talking about had to be in at least 24 inch lengths, and not the 16 inch stove lengths I was cutting.  More probably it was cut into between 32 and 48 inch lengths for industrial use, transportation in bulk and most probably very wide fireplaces.  Charcoal makers would cut wood even longer to make large stacks of wood.  Still, do the math.  I'm cutting about 3 times as much to get my 16 inch logs as a guy cutting 32 inchers, but even the slowish guy could probably put that up in just 3 days of average work!

Well, that is interesting to think about, but it doesn't prove anything to me for real or gain me a lot of real insight.  To gain knowledge it is required of us to take information and do more than absorb it, more than mull over it and make assumptions and inferences.  For me that process looks more like taking in information, contemplating it, putting it into practice, maybe getting more information, more experience, more contemplation etc.  At some point, something resembling truths begin to gel out of that process.  In short, I knew that to gain real insight into the problem of axe work and what it's potentials and limitations really were, I had to put it into practice for reals.  Not only that, but I actually had to improve my own skills to a certain level before I could really understand what that potential was and where an axe may be more or less useful than a saw.  Give an unskilled person an axe and a hand saw and tell them to limb this same tree and they are likely to conclude that the saw is easier and faster.  But no matter how good they get with that saw, I'll have the same tree limbed up more quickly, with much less physical effort and many of by knots will be trimmed more closely than theirs.

I'll also have way more fun doing it!  Axe work is engaging, exciting, focusing, cultivates coordination and provides a diverse form of exercise.  Sawing by comparison is dull and tedious work and the best you can do is trade off one side for the other.  I like sawing up to a point.  It is good honest contemplative work.  It is also skilled work and a good hand with a saw will out saw a newb every time.  But it is only so skilled and lacks the special combination of things that makes axe work really engaging and fun.  Saws have their place as do axes.  But the place an axe has in any one particular persons hands is informed by that persons skill level and understanding of it's efficient use, and that requisite skill is only gained by extended use, and not by dabbling at the thing.

All of which is to point out that, while my use of an axe on that fir tree in these last couple of videos did result in two fewer logs worth of large firewood, rather than smaller chips, such is simply part of the cost of admission into that understanding of what is and is not possible with an axe and what place it does or doesn't have in our tree work.  It's a rather small price it is to pay when they are easy to pick up and decidedly very useful as fuel or for other purposes.

And repeat thousands of times :)

And repeat thousands of times :)

Considering Biochar Burning Methods Conversion v.s. Context

A common mistake in design and assessment is to focus on one or two narrow parameters at the expense of everything else.  For instance, elevating one factor so high in priority that outlandish expense is gone to in order to achieve it without considering cost/benefit ratio.  No doubt in some cases prioritizing something that highly is the correct thing to do, but a common trap is to fail to consider design or assessment of a system in context.  As I was finishing up writing this blog post, I received this comment on my video about burning brush in open piles to make biochar.

“Looks more like a video on how not to do it. Cone pits or trenches are much more efficient and produce far less ash. Even a proper 55 gallon oil drum burn does better in my experience, although thats more for scrap pallet wood. ”

This comment seems to highlight the mistake of putting a single parameter, in this case conversion efficiency, above all other considerations, and in their context presumably and not mine, which they clearly don't understand.  You can read my reply to that comment on youtube, or watch this follow up video about considering context in comparing charring methods, which that commenter obviously missed (I hope lol) but everything important I have to say about it is also in this rather lengthy article; the purpose of which is to elaborate on why I use open burn methods and possibly more importantly, to simply discuss the importance of context, resources and cost/benefit when defining priorities and making decisions.



Using simple methods of production, I have been able to accumulate hundreds of gallons of char and should have hundreds more by the end of the burn season.  The intimidation or time and materials required in the building of a retort or TLUD burner, or even a stand alone cone kiln, hold many people back from getting started with biochar.  Building those can be intimidating or otherwise hard to pull off.  There are also claims about charcoal quality from the various systems, which may have people holding out to produce "real" biochar and not just charcoal.  But, there doesn't seem to be any consensus on that, and there is plenty of evidence that just about any charcoal is effective to a degree, whether it is hard or soft, burned hot, or burned cool.  That is not to say that some types are not more effective, or that such has not already been proven.  I'm not really up on the latest, or up on that discussion at all really.  While some systems are undoubtedly more conversion efficient than others, there are other considerations and many of the possible draw backs of open burns are basically eclipsed by the great ease, minimal processing and speed of open burn systems.

A TLUD system, for instance, requires chips or other small, somewhat homogenous fuel sizes, which is only great if you have easy access to that kind of fuelstock.  If you have easy access to an industrial strength chipper, maybe that makes it a viable option as well, but to purchase and own such a thing is a great expense and would not make sense for most people.  I'm pretty sure it would have a higher conversion efficiency than the trench or pile approaches I use, that is higher charcoal produced for the amount of wood put in, but that has to be weighed against having to chip the stuff.  This is what I'm talking about with the focus on one aspect.  Conversion efficiency, i.e. WOOD/CHARCOAL ratio, has to be weighed against many other factors in order to make a rational decision.

One of those factors is labor and the input of other resources.  Even with the large amount of wood my land produces (and the neighbors' land if I were to expand operations), I couldn't justify buying, or even renting a chipper until I hit an economy-of-scale tipping point.  So, lets say I hit that point and rent a chipper for 700.00 for a week or whatever it costs.  Then I have to have metal TLUD kilns to burn it in.  On that scale I'd be burning through 55 gallon drums pretty fast and probably burning 4 to 6 of them at a time to produce 100 gallons of charcoal in a run.  Contrast that against open piles which require a shovel and a hose, no fuel, no cost and less handling and transportation in many cases, and the TLUD starts to lose points, even if there is a significant conversion loss to ash in the open burns.  Lets say that loss is as high as 20%, which i really have no idea.  But say it is.  I still have to think hard about adopting that expensive system, especially if I start thinking about building larger, more robust burners that will produce 100 gallons in a single run and not burn out quickly.  I could go on, but it's energy, financial expense and time v.s. conversion efficiency.  And the truth is that I still don't know how efficient or inefficient the open burns are.  My impression from the beginning is that they are actually surprisingly efficient, but there is an obvious loss to ash, and probably considerably more in the open piles than the open trenches.

Retort systems use some quantity of wood to heat an inner chamber of charcoal.  A simple retort would be a drum full of wood that is sealed off except for a pipe coming out the top, which terminates under the barrel.  If you build a fire under that barrel, it heats the wood inside, releasing gasses in the sealed drum that travel through the pipe and back into the fire underneath.  The gasses are flammable (wood-gas), so the wood in the drum helps burn itself as the gasses are flared off underneath.  That's one of the first ways I learned to make charcoal for smithing many years ago.  One obvious consideration for a retort is that the system requires fuel to be consumed to make the charcoal, which is an inherent inefficiency.  That inefficiency can be reduced to an extent by design and should probably always be more refined than a simple drum with a fire underneath it, but the consumption of fuel is inherent to the method and has to be considered in a fair assessment.

In comparing retorts to open burns, there are a couple of possible advantages to retorts.  One would be that it produces a harder charcoal, which some people claim is better.  I just don't know if that is true or not and I've seen the opposite claim as well.  Certainly, if you are producing charcoal for industrial use, heating or cooking, you want a hard, dense, long burning charcoal produced in a low oxygen environment.  Another possible advantage to retorts would be that since the wood that is being charred is mostly sealed up, with just small holes in the container for the gasses to escape as it's heated, it can't really over burn.  So, if you had the system dialed, hopefully you could load it, fire it off, walk away and come back to finished extinguished charcoal.
If the charcoal from a retort really is more effective as a soil amendment, then a careful comparison would have to take that into account as a possible counterbalance to the fuel consumed in it’s own production, especially when comparing to an open burn which also has some inherent loss to ash, no matter how well it is run.

A clear disadvantage to a retort is that dry fuel is going to be much better performing.  It rained yesterday, but I could still go out and mix my dead and green material together and fire it off, or burn a trench and not only get away with burning my now damp wood, but burning some green stuff with it as well.  I do not have storage or drying facilities for the large quantities of wood I’m dealing with to burn dry wood in a retort or TLUD.  To burn dry wood I would either have to build a large dedicated shed area also requiring that I handle the wood more, or a large vegetation free area, probably even a screened room, to be able to burn in the summer when it’s very dry.

There is a lot of information I don’t have and a lot of information out there that I have not availed myself of.  But in a big picture context, I’m not focused on any single factor and my personal context drives my choices.  What I know is that I can produce very large quantities of charcoal with NO MONEY INPUT AT ALL, or building or rebuilding anything, just a shovel and a hose, and in the case of open piles I don’t even need the shovel.  I can do that with minimal processing of the fuel and no careful storage.  It is fast and requires almost no size reduction of the stock, though I prefer to burn trimmed poles and limbs for ease of handling, storage and they function much better in the pit that twiggy stuff does.  I trim out the larger, easier limbs for the pit and burn the really brushy stuff in piles, though there is overlap in this spectrum for sure, I find the two methods VERY complementary to each other.  They are simple and low input, and with the quantities of wood I have to deal with, I would probably get less wood actually burned in a small retort or TLUD system, while scaling up to a large TLUD or retort would probably get expensive.
Again, there is information I don’t have here and I’m not suggesting my way is better, just that it seems better in my context, especially since I can get it done.  Even if someone was able to prove to me that retort produced char is twice as effective, I would still have to consider whether I could pull off charring the quantities of wood I have available, or consider just letting half of it rot and charring less, while also weighing in the added financial outlay and work of setting the system up, as well as the drying and storage of wood.  And lets examine that effectiveness of different char types thing next, because that gets interesting. 

My positive results using biochar have not been uniformly phenomenal, but they have been almost uniformly obvious.  The most phenomenal was my leek bed this year with what I estimated to be 400% to 600% higher productivity at 10% char, all of it open burned or scrounged up from firepits and woodstoves.  That is 4 to 6 times the production all other things being equal, so the char is effective.  The question at this point is just about quantities and level of effectiveness of different chars, rather than if they are effective at all.  If retort char were more effective, it would have to be quite a bit more effective to start tilting me in it’s direction when looking at the other considerations I’ve already brought up.  BUT, check this out. 

I used 33% in one test bed, and 25% in another., both two feet deep.  Both of those sections also have 50% char in the top 4 to 6 inches of the bed!  Is that crazy?  Well, I can tell you it takes a crazy amount of charcoal!  But damn are those beds nice.  Only long term observation will convince me if they work better or worse than beds with less, or even more char, but there is an obvious advantage in weeding, soil crusting and therefore maintenance. 

I’ve been gardening here and elsewhere for a long time, and one of the great problems of gardening is soil crusting.  Why it isn’t discussed more I have no worldly clue.  No soil I've ever worked with is completely immune to it and most are very susceptible.  If you disturb soil and water it, the problem of soil crusting manifests it’s flat and ugly visage.  It impedes water penetration, but causes more rapid evaporation.  Water a crusty bed and a lot of the water can run off instead of soaking in, and then you’ll lose the water that does make it into the soil more quickly unless you cultivate to create a “dust mulch” as soon as you can, or cover the whole soil surface with something.  In those two test beds with 50% char in the top 6 inches, soil crusting is no longer an issue, period.  The soil is very loose, which makes weeding easy.  Water penetrates, period.  No matter what the history of the bed, weather, vegetation cover etc and so on, water penetrates every time.  EVERY TIME I WATER! Chunks of charcoal migrate to the top of the bed and cover at least 50% of the surface as a mulch.   Don’t forget, that is a MULCH THAT DOESN’T EVER ROT!  I can add surface amendments for nutrition, like compost or coffee grounds, but gone is the need to either cultivate or cover the soil surface with mulch after watering.  GOOOONE!!!  Wow, I freaking love those beds.  Though they are just two small sections of two small beds, I have a sinking, unhappy, I’m-wasting-my-time feeling when I have to plant in any other beds.  Just today I was out planting tomatoes in my 10% and 5% char beds and it was fairly lumpy, crusted over and generally unpleasant to work with.   I’m going on a tangent, but I have a point in the context of this article, which is that at application levels of 25% to 50%, the quality of the char may become somewhat irrelevant if the goal is as much about high charcoal content for physical effects as it is about the reasons that biochar is probably more usually applied for, like nutrient holding.

To tie this up, my guess is that a majority of people reading this will be best off at least just starting with open burn methods, unless you have access to chips, in which case you might consider building a TLUD.  At the very least it gets you off the ground and running immediately.  There will be more wood to char later.  It is fast and you can do it all over your property or even on other people’s properties, rather than always transporting all of your wood to a single location or transporting burners.  I’ve already heard from a number of people that they busted a move with the trenches or open burn piles and are now producing char instead of ashes, or instead of accumulating wood waiting for the day when they get some device together that they thought they needed.   David the Good's recent comment was "Open burns really are the way to go. I thought about biochar for a long time and looked at all kinds of systems that I really didn't feel like building... then started making big fires and spraying them with the hose. Now I have lots of char." 

I’ve said it over and over again, the primary problem of biochar that needs solving for the masses is accessibility.  The idea that you have to make the proper kind of char, the proper way, or that there is a material difference between “biochar” and charcoal in every context is unsupportable.  The best biochar is the biochar you get made and buried in the ground, just like the best camera is the one you have with you.  We can always view things in ideals like super high production, beauty, convenience and so on, but that view approach minimizes the importance of context.  If anyone interprets this article as being negative against, or disregarding other methods of biochar production, you aren’t reading carefully enough.  I could definitely see adopting other methods than open burns in the future, but only when and where they make sense.  I am just as much not trying to sell you in particular on open burns v.s. other methods.  I’m just imploring everyone to think in context and consider, costs, benefits and resources in making these decisions.

We can apply this type of thinking to life, problem solving and decisions in general, and we should.  We may not always have all of the information, or the best information, or be able to foresee everything that we need to foresee to make the perfect decision, but that is not what problem solving is about.  Good problem solving, design and understanding are a journey not a destination.  For all I know someone will read this article, drop some new knowledge or information on me that affects my thinking and ultimately changes the way that I produce biochar.  That would be great.  Better is better and that’s where I’m always trying to head.  But that also doesn’t mean that I’m going to put large amounts of resources into research and experimentation to refine the process and my approach to it to within a gnats ass of perfect efficiency, because the time and energy and thought space to do so is also part of my context and my personal cost v.s. benefit equation.  So, at this point, I’m fairly content to just hang here with what I’m doing and refine it in small ways as I can until I have some reason to stretch out in other directions, or someone wanders along and drops some game changing knowledge on me.





No Brush Left Uncharred! The New Scorched Earth Policy!

It's not much harder to make a big pile of charcoal out of a burn pile instead of just burning it to ashes.  The short version is that you light it from the top and then put it out with a hose.  There is a little management involved and I do like to stack it neatly myself, but you can cut all kinds of corners and still end up with a lot of charcoal.  The charcoal lasts forever, and works amazingly well in my garden, so it's a pretty good deal!

Rawhide, Leeks and Roads

Apparently I can't keep up with myself.  Here is a backlog of recent videos on everything from rawhide to roads.


The difference between the different sections of the leek bed are even more obvious now, confirming more what I observed this summer, which is that the soil with charcoal (biochar) has what is generally referred to as heart.  That is to say it has staying power and isn't easily used up without regular additions of fertilizer.  I've been very negligent with this leek bed and it really shows on the control end with no charcoal, but not much on the 10% char end.  The 5% section is better than half way between the two others, but there is an obvious difference except that within one foot of the 10% section, the plants are nearly indistinguishable from most of the rest of the 10% section.  The very end of the 10% section drops off in size, but that may be due to the shape, of the bed, which is pointed on the end.  Also, many gardeners will have observed that plants tend to do less well on the ends of beds.  If you took the difference between the control end and the 10% end as at least 600% difference, that could be interpreted as the 10% char end making 600% better use added amendments.  That is a sloppy interpretation and doesn't take into account all possible factors, but it's still impressive and probably on the low side if anything. The leek seed from this project will be ready in the fall for planting about this time next year.


This one is a quick primer for what will be a series on the design of graveled roads based on what I learned and have observed building mine, as well as paying attention to other unpaved roads and what happens to them in various circumstances.  It will have to potential to save a lot of people, time, money, unpleasant driving conditions, all while saving resources ultimately and keeping sediment out of stream beds.  In the meantime, you can download the handbook for forest and ranch roads for free here.  It is a dry read, but very worth putting to use if unpaved roads are a regular part of your life.


This is the final part of the rawhide axe handle brace.  As usual for me, this series wasn't just about making this one tweak, but about rawhide and sinew and hide glue and context and related stuff.

Simple Remote Biochar Production Experiment Part 1

I have a situation that is faced by many in my part of the world.   After many decades of wreckless logging, the whole area is pretty much a mess.  Overgrown forests with massive quantities of Dead, Diseased, Decrepit, Dying, Deformed, Decadent (I'm running out of D's, whats a D word for crowded? Dense maybe...) trees and brush.  Just the amount of already dead and down wood is sometimes enough to make a bunch of charcoal at any given site.  The forests are generally unhealthy and not very productive of food for wildlife.  The trees are crowded and instead of having a reasonable number of healthy trees we tend to have a lot of competing trees that are just hanging in there, with very healthy large productive trees of any kind being the exception.  The forest is seeking an equilibrium as always, but that is a process that takes time and we can intervene to speed up the process or steer the ecology in a certain direction such as managing for diversity, wildlife, timber, or all three at once.


Given the general success of biochar growing experiments and the remarkable prehistoric and historic examples of charcoal amended soils, it just makes sense to pursue conversion of a portion of that biomass into charcoal.  While sophisticated methods utilizing the energy released in charring will no doubt be developed (and should as soon as possible), there is no good reason for citizens with woodlots not to engage in small scale production of charcoal and at this point I think it's pretty much nuts to burn brush piles into ash.  With the pit and trench methods, we have completely eliminated the need for chopping up or chipping wood 3 inches diameter and down.  That is a huge step and makes burning charcoal extremely accessible to anyone that can get away with having open fires.  But, I find myself faced with a problem that many others will also have.  That is extinguishing the charcoal once it is formed.  Most of my brush is in areas with no water.  This simple idea might take care of that problem and make burning charcoal in remote areas very easy.

Anywhere I walk in the woods here there is clearing to be done.  I think most areas that are unmanaged I could probably dig a trench and produce at least a couple hundred gallons of charcoal without having to drag the wood very far.  Otherwise, I have to clear a way to drive in so I can either drive the brush out or bring water in (sometimes feasible and sometimes not).  While my idea is very simple, solving that problem opens up huge possibilities for me and anyone else in a similar situation.  

My friend Erica and her daughter Jessica live on 200 acres with the same problems.  Like me, Erica does forestry practice, just because it is the right thing to do and needs doing.  The result is huge amounts of biomass that could be converted to charcoal.  When they have a window of good weather to come over, we're going to test out this idea and possibly be looking toward further experiments to assess the feasibility of char production as a cottage industry for land holders in this situation.   I think there is great possibility there.  I'm always interested in ways that people here can make a living doing something useful using the local resources of which none is more abundant than excessive biomass.  That is more relevant than ever since the economy has been artificially buoyed by black market marijuana production for some time, and that won't last much longer as more people in more states are going into Marijuana production which is causing prices to plummet.  Good riddance I say, but don't get me started on that!  Eventually, we will no doubt return to the kind of hardscrabble existence that characterized the area previously.  Personally, I see that as mostly a good thing as it forces people to be creative and do a diversity of things to get by.  I have lived in areas like that before and there are negatives for sure, but I generally like the "necessity is the mother of invention" kind of effect which makes for interesting and less entitled people.  It certainly weeds out the weak.  I think that most people have become too lazy to pick up a shovel, walk off into the woods, produce some charcoal, haul it out, set up some processing apparatus and then prepare, bag and sell biochar; but I'm hoping that it may actually be feasible at this particular point in time to do so, and actually make enough doing it to make is profitable enough to pursue for people that like that kind of work.  Personally, there is hardly anything I like more than being out in the woods with some hand tools and cutting, trimming and burning stuff.  Most people would benefit from that kind of exercise and meaningful, direct work.  That's my idea of a good time!

Permanent Soil Improvement Experiments w/ Biochar Continue, Catch Pit for Artichokes

This is the fourth such experiment in long term deep soil modification using a simple system of trenches or pits.  For now I'm using the term catch pit.  The basic concept is a hole where you toss in stuff that builds soil and feeds plants, backfilling with charcoal and dirt as you go.  It's cool.  Everyone should do it so we can find out how well it works.  I think default thinking these days is to let someone else prove things first, but I think that is backwards and everyone's context is different anyway.  I'm not just interested in how the finished soil performs, but how it ends up fitting into people's lives.  To me that part is just as interesting.  A society that feels an obligation not to waste soil nutrients and to build soil for the future is the one I'd like to live in, so that's what I'm doing.  I don't really know about the state of the rest of the world, but I think America would benefit from picking up a shovel more often and investing in an uncertain future.

BITE ME! revisited, Checking in With My First Seedling Apple and a Few Others

I only had a few specimens of my seedling apple this year.  The first couple were unripe, but the last one seemed better than any I had last year.  That is not surprising since fruits either grafted or from seed can take a few years to start bearing exemplary fruit.  BITE ME! is from an open pollinated Wickson seed, which means that I don't know whos spread powdery pollen was spread over Wickson's sticky stigma.  This year BITE ME! seems to have more of the Wickson flavor that motivated me to use wickson as a parent in breeding.  That flavor and the high sugar content (up to 25%) have encouraged me to make a lot of intentional Wickson crosses with other apples.  It's encouraging that the flavor came through in the this case, although the sugar content of BITE ME! seems average.  I will definitely be sending out scions of bite me to whomever wants to try it.  It has potential and I'd like to see what others think of it in the long run and how it does in other regions.  I will probably start selling scions in the webstore here about FEB 1st.  That is the plan at this point.

Also in this video we taste a few other apples, one that is probably Northern Spy, Zabergau Reinette, Vanilla Pippin and Suntan.

Much Improved Growth of Leeks in Biochar Test Bed

About three years back I set up my first biochar test bed.  I divided the bed into three sections of 10% charcoal, 5% charcoal and 0% charcoal.  The sections were all treated the same, except the 0% section was amended with a small amount of wood ash in an attempt to approximate the amount that would have been added incidentally with the charcoal.  I even dug the 0% section exactly the same as the 5 and 10% sections.

The first year the char sections of the bed performed poorly.  Lettuce failed to thrive in the char sections, but did fine in the 0% section because the charcoal sapped the soil of nitrogen and who knows what else.  several growing seasons later though, it's a different story.  I forgot to mention in my leek planting video that the bed I used was this test bed.  now that the leeks are established and growing, there is an obvious difference in the three sections with the 10% doing the best and 0% by far the worst.  While there could be some other factors involved, it's pretty clear that the charcoal is having a very positive effect.  I would say that the 10% section could be doing as much as 600% better than the 0% section.  The weeds look a lot happier too.

What the exact effect is, I don't know, and while I'd like to know, I don't necessarily need to.  It is just working and that is the important thing.  It seems that the charcoal amended sections are making better use of whatever resources are put on them.  We'll see how the leeks progress through the season.

What I learned from this experiment so far is that 10% is better than 5% and 10 inches deep makes a difference.  I'd like to put in a similar experiment with 10%, 15% and 20%.  I'd also like to do sections of a bed at a constant percentage, but one dug to 2 feet and one dug to only 12 inches.  And there are many more experiments I could do.  Each bed I install will be a different test of some kind.  It is easy enough to set them up and I could potentially learn from them for years.  I hope some of you out there will start collecting or making charcoal and setting up your own experiments.  If you already are, leave a comment and tell us about it.


A Few Juicy Accounts of Biochar Use in 19th Century N. America and Europe

Some of you that have been around a while will remember a research piece I did on the use of charcoal as a soil amendment in 19th century America and Europe.  I'm always trying to push this information out there, so In this video I read a few of the more interesting passages, which I'll also paste in as text below if you would rather read them..  This is the information that really compelled me to jump into biochar experimentation with both feet.  I have quite a few experiments installed now and quite a few more I'd like to do as soon as possible.  I have accumulated a pretty good pile of charcoal, so now it's mostly a matter of some planning and digging.  Also down the page is a video that I published last Wednesday of peeling a tan oak stump with a few comments about the historic tan bark industry here in California.



Every observing farmer who has been accustomed to raise wheat cannot have failed to notice the luxuriant growth of cereal grain round about the places where charcoal has been burned, even more than thirty or forty years ago. The growing stems of wheat that are produced on such old charcoal-beds are seldom affected with rust; and besides this, the straw is always much stiffer than that which grows where there is not a dressing of charcoal.

& from the same publication

The field was sown with barley in the spring previous ; yield small (eighteen bushels per acre). I turned in the stubble the last week in August, harrowed it over, then took about eighteen bushels charcoal crushed fine, and top-dressed a strip through the middle of the acre over about one-third of its length; I then sowed on my wheat broadcast and harrowed it over twice. The result was, the heads when ripe were at least twice as long as where no coal was put on. I harvested all together; the yield was forty-three bushels. I think by applying about fifty bushels of coal to the acre as a top-dressing, made fine by grinding in a common bark mill, it would increase the yield at least four hundred per cent., if the soil is poor.

The American wheat culturist: 1868



By keeping the surface of the earth well stirred, no crops appear to suffer by drought that are manured by charrings, but continue in the most vigorous health throughout the season, never suffering materially by either drought or moisture”.

“A Dictionary Of Modern Gardening” 1847



In the midst of the disastrous drouth of last summer, while crossing a field in Moriah, occupied by Mr. Richmond, in pursuit of some Durham cattle I wished to examine, I observed a lot with its surface deeply and singularly blackened. -Upon inspection I found it thickly strewn with pulverized charcoal. The field presented a rich verdure, strongly contrasting with the parched and blighted aspect of the adjacent country.
The following detail of this experiment, supplied at my request, attests the value of this material as a fertilizing principle. “The soil is loamy. The charcoal was applied on four acres of dry land, and one acre of moist soil, by top-dressing. The amount used was about one thousand bushels to the acre, spread on so as to make the surface look black, but not to incumber or obstruct vegetation. It was applied in September and October, 1850, at an expense by contract, of forty dollars. It was procured at a furnace, from a mass of pulverised charcoal left as useless, and was drawn one mile and a half. The effect was immediate. The grass freshened, and continued green and luxuriant after the surrounding fields were blackened by the early frosts. Although the last season had been so unfavorable for vegetation, Mr. Richmond realized one-third more than the ordinary yield of hay, and sufficient to repay the whole outlay. He thinks that he cut nearly double the quantity of grass upon this lot, that he did upon any similar meadow on his farm, and that the quantity of the hay is improved.”


“I began the use of it in the year 1846, and first employed it as a top-dressing on a strong clay soil, which was plowed in the fall of 1845. I spread on about fifteen wagon loads of the dust to the acre, after the wheat had been sowed and harrowed one way. I was surprised to find my crop a heavy one, compared with my neighbor’s, raised on the same kind of land. The wheat was of better quality and yielded four or five bushels extra to the acre. I have since used it on similar land, sometimes mixed with barn-yard manure, and sometimes alone, but always as a top-dressing, usually on land seeded for meadow. ‘ The results were always the most favorable. I find my land, thus seeded, produces more than an average crop of hay and always of the finest quality.
“I have also used the dust on loamy and interval land, with the potato crop. During the series of years in which the rot almost ruined the potato crop, I scarcely lost any potatoes from that cause, and supposed it was owing to the coal dust I used. My manner has been to drop the seed and cover it with a small shovel-full of the dust, and then cover with earth. In this way I have used all the coal dust I have been able to save from the coal consumed in a forge of five fires, and which amounts to about 250 loads per year.”
In the colder regions of the Adirondacks, charcoal dust has been used with great advantage. The note of Mr. Ralph presents the experiment in tho following language: “As a top-dressing for meadows, charcoal dust and the accumulation of ashes and burnt earth left on old charcoal pit bottoms have been used here with remarkable results, and I judge from the trials which have been made, that this application has added at least one-third to the hay crop, where it has been used. It was remarked during the past very dry season, when vegetation was almost burnt up by the long continued drouth, that those fields which had been dressed with this substance were easily distinguished by the rich green color of their herbage.”

The cultivator, 1853


“NEW” FERTILIZER FOR GRAPES.  Our impression is that the benefit to be derived from the use of chopped up cuttings has been greatly over-rated. We tried the plan once, selecting out the smaller shoots and cutting them up with a straw cutter, while the larger we cut with a small hatchet. We applied the prunings of ten vines to the roots of five, and then we invested the amount which we thought we ought to have for our labor, in charcoal which we applied to the remaining five. We thought the charcoal produced the best results.
Since that time we have disposed of our prunings of all kinds by converting them into charcoal and at the same time burning with them a quantity of heavy clay. The greatest difficulty is to make the heap sufficiently compact to allow it to be covered conveniently. This we accomplish by means of a few stout hooked stakes. After all the rubbish from the fall, winter and spring prunings, has been collected together, we lay a few stout branches or poles on the top. These poles are then pegged down by means of two or three hooked sticks applied to each pole, and in this way the mass is rendered so compact that it is easily covered with sods and similar matter. The heap after being kindled is allowed to smoulder away, more earth being thrown on as the fire progresses. Several days generally elapse before the work is finished,
but at the end of that time we find ourselves in possession of several tons of material of the very best kind for fertilizing vines or any kind of fruit trees. It consists of a mixture of ashes, charcoal and burned clay, and our present opinion Is that there are no better fertilizers for fruit trees, and especially grape vines and peach trees, than just these three articles.

Country gentleman, Volume 33


his trial on a field of four acres with potatoes in 1847, was very remarkable. They were planted in ridges, or, as termed here, ‘lazy beds;’ one-half the field manured with farm-yard manure, the other with peat charcoal only, about a handful thrown on each seed. The result was more than a double crop from the charcoal; and he informed me that he was himself so astonished at the fact, that he requested Lord Donegal to see and vouch it. At my suggestion he planted oats the next year On the whole field without any further manure, and he assured me the increase on that portion manured with charcoal was nearly in the same, ratio as the potatoes.  In February last he planted a large field in drills, manured as usual, not then having charcoal; but in. April he got some, and, before the potatoes being earthed, he top-dressed a few yards at the foot of all the drills as far as he had charcoal. He authorizes me to state that the result was not only very nearly a double crop, but that there was not a taint in one of them, while all the rest of the field was more or less diseased.

I must tell you his reply to my inquiry as to his experience of its value for grass land. He said,1 Nothing can exceed it; and there is little or no labour in using it.’ My friend Fenwick swears by it, and he declares he will write his name on the best grass in the country with black charcoal, and it will be the greenest part of the field in ten days.”

The Plough, the loom, and the anvil, Volume 2


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

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 shriveled..

The Farmers’ cabinet, and American herd-book, Volume 11 1847



For two years past I have used some fifty loads each season of refuse charcoal, and being fully convinced that it pays, I wish to recommend it to my brother farmers. I have tried it on grass, corn and potatoes—hare tried it alone and in the compost heap, and in all situations it has proved faithful to its trust. As a top dressing for grass, it gives a green color and luxuriant growth.. Applied to half an acre of early potatoes the last summer, the yield was 75 bushels of as fine healthy potatoes as could be desired, that sold readily for one dollar per bushel, and yielded the best profit of anything raised on the farm.

..It absorbs from the air those gasses offensive to the nostrils, but the main food of plants. And this it will do, not once only, or for one season, but very possibly for a century. Where an old coal-pit has been burnt, the land never seems to wear out, and the first settlers point to the coal bottoms that are fifty years old, still by their exuberant vegetation marking well the spot where the wood was converted into coal.

The New Jersey Farmer Vol. II, No. 1, September 1856


It will be recollected by our readers, that in our last two volumes we have published several able papers upon the virtues of charcoal as a fertilizer of the soil, and of its supposed efficacy in the preservation of wheat from rust. One of these papers, by Judge Hepburn, particularly points out cases in which lands which had been dressed by charcoal had grown wheat free from rust, when wheat grown on other lands, contiguous, which had not been so treated, had suffered greatly from that cause. We allude to these circumstances now, with a view of introducing the subjoined paragraph to the notice of our readers ; by which it will be seen, that in France the same virtues have been ascribed to charcoal as in our own country. 

We have been astonished at the enormous increase of the wheat crop in France within the last eight or ten years, and have devoted some attention to the investigation of the subject. It appears that charcoal—an article that can be obtained here for a tithe of its cost in France—has been extensively used, and with marked effect, in fertilizing the wheat lands in that kingdom. A correspondent of the New Farmers’ Journal, an English print, states that during a sojourn in one of the central departments of France he learned that some of the most productive farms were originally very sterile; but that for a number of years their proprietors had given them a light dressing of charcoal, which had resulted in a large yield of wheat of excellent quality. Since his return to England he has tried the experiment upon his own lands with the same happy effect. The charcoal should be well pulverized, and sown like lime, after a rain or in a still, damp day. Even in England, the writer says, “the expense is a mere trifle, in comparison with the permanent improvement effected, which on grass is truly wonderful.”— He states one other very important result from its liberal use. “I am quite satisfied that by using charcoal in the way described rust in wheat will be entirely prevented; for I have found in two adjoining fields, one of which was coaled and the other manured with farm-yard dung, the latter was greatly injured by rust, while that growing in the other was perfectly free from it.”—Buffalo Commercial Advertiser.

Southern planter, Volume 3 1843



ln striking cuttinps or potting plants, fine charcoal is a valuable substitute for sand, plants rooting in it with great certainty. Plants will flourish in powdered charcoal alone with considerable vigor, and, added to the other materials used in potting, it is found greatly to promote healthy growth in most plants.)

Fruit recorder and cottage gardener 1875



there are two features connected with its use which have always commended it to my favor. One is its mechanical effects upon the soil, rendering it more open and friable, and consequently more easily worked, and more open to the action of the atmosphere. The other is the warming effect produced where it is applied in any considerable quantity. A dark soil, we all know, has the power to a greater extent of absorbing heat than a light-colored one. This, in many locations, is a great desideratum. Many plants which it is desirable to grow, but which, for the want of a sufficiently warm soil, is next to impossible, may be cultivated by the use of charcoal....   In gardens, therefore, I esteem it highly, and have found it, for the purposes briefly named above, most excellent

The American farmer:  1861


Charcoal is undoubtedly a powerful fertilizer, and one of great duration, as is shown by the continued fertility of places where the aboriginal inhabitants of New England built their camp-fires more than two hundred years ago, while nothing peculiar to those spots can be discovered beyond the admixture of large quantities of charcoal and clam-shells with the soil.

Annual report of the Commissioner of Patents, Part 2 1855


Charcoal as a Fertilizer.
Mr. Bateham:—Sometime since there was an enquiry in your paper, respecting the use of charcoal as a fertilizer. I have one word to offer on the subject, which is this: some 15 or 20 years since, while owned by another individual, there was much coal burned on my farm while in the act of clearing the land. The land since that time has undergone much tilling, with little or no manure and not much rest until lately; and notwithstanding the time that has elapsed, the places where the coal pits were burned, produce the best of crops of every kind whenever the fields in which they are found are tilled. I am so much pleased with it that I wish my farm was covered I 3 or 4 inches thick with pulverized charcoal. I think the benefits of it could never be exhausted.

Ohio Cultivator vol. 3 No. 1 1847



We have all noticed that where a charcoal pit has been burned the soil remains good for a long time. On the mountains of Berkshire we have seen white clover growing luxuriantly on the bed of an old charcoal pit, making an oasis in the desert of ferns and briars that surrounded it, and on inquiry we found that the coal pit must have been burned half a century ago. On digging into this soil we discovered the charcoal with little if any appearance of decay, and promising to do good service for half a century more.

Agriculture: twelve lectures on agricultural topics:1871



The first day of our trip, we saw the farmers engaged in burning stocks of millet, &c., in heaps of earth, as it is done in the manufacture of charcoal, in order, we supposed, to bring out their fertilizing properties. It a very likely then, that, in China, they have known the value of charcoal as a fertilizer long before us, It’s use for that purpose being among us of a recent date.


Commercial relations of the United States with foreign countries 1872



Refuse Charcoal.  The refuse charcoal, obtained from the rectifiers of spirits, from the Railroads where wood is burned in locomotives, from old charcoal beds, &c., is a very useful material in the garden. As a mulching about fruit trees I consider it very valuable. It keeps out frost in winter: it keeps the soil loose and moist in summer, and it does not afford a harbor for mice or insects. In the soil, it assists to promote moisture in a dry season;........ It is an excellent mulching for Strawberries, in winter or summer.

The Gardener’s monthly and horticultural advertiser, Volume 9  1867


Peeling Oak Bark for Tanning Leather and Apple Breeding Update

Here are a couple of recent videos I did on the stuff I do around here.  One is a short update on labeling and protecting fruit that was pollinated earlier this year as part of my apple breeding project.  I talk a little about the breeding parents and related stuff, but it's pretty straightforward and short, with a quick visit to my new pig. The second is a follow along while I cut down, cut up, and peel the bark off of a tan oak tree that is infected with the organism involved in sudden oak death.  I use the bark for tanning skins.  I'm working on a book right now on tanning with plant materials like bark, various leaves and pods and stuff like that.  Writing, research and experiments around that project now consume most ofmy time, energy and thought.  In the video I show a few pieces of leather tanned with oak bark, peel the bark, split the wood and clean it all up.  There are few things I'd rather do with my time than that type of forestry work.  Splitting wood, playing with wood, using my axe, burning brush to make charcoal, etc..   is all my idea of a good time!  woo hoo!  It's really hard for me to cut these videos down and focus them in.  There are so many satellite topics I want to talk about!   Definitely some stuff coming on axe use, wood splitting tutorials, forestry and forest ecology, and lots of tanning and skin working stuff.

Simple, Efficient, Cheap, Flexible Biochar Trench Video, and Frankentree Trailer

Coming next weekend!  I guarantee the actual video is less exciting than the trailer, but it is much more edifying!  This video will just be an introduction to the idea, and the benefits of frankentreeing.  I will certainly put together a much more technical video in the future.

Below is my second fast motion video on the two simple biochar methods I've been experimenting with.  A few notes...

Fuels:  I suspect that pieces larger than about 3 inches are better either split down or charred by another method, and chips might be better done in a TLUD or some such device.  I haven't tried either in the trench though, so that's just speculation.  I doubt that large wood will char well in the trench because it takes so long to char all the way through, but chips might be just fine if fed pretty constantly in thin layers.  As long as everything you're putting in turns to charcoal and you're not getting a lot of ashes or a lot of smoke with it, you're doing well.  I've done green and dry wood.  Dry is better of course.  I think the jury is still out on green wood.  The one I did mostly with pretty green wood was a very hot, large pit and the wood was brushy allowing for the ingress for large amounts of air.  It was still pretty sluggish and I'd certainly tend to let the stuff dry for a summer first if possible.

Wood size and shape:  It's hard to say without actually measuring things, but the trench seems to have a very efficient conversion ratio (wood to charcoal with low ash production) if the material is of a nature that it can be laid thickly and flat onto the coals, and of course if it is tended adequately.  This method takes a little more effort than last week's open burn, since you have to dig a hole, but it handles certain materials better.  I've done a number of these now and have found that they don't handle tangly brush all that well.  I did pretty good with douglas fir limbs, but not with oak, madrone and similar branches that have a lot of twigs poking in every direction.  The fir limbs are pretty linear and stack into the trench closely enough to get by.  If the fuel doesn't lay into the trench well, it will allow too much oxygen to reach the coals and result in more ash formation.  So, really tangly stuff that takes up a lot of volume of space might be better burned in an open pile, or reduced in size and shape to fit into the trench better.  When I take trees down, I typically limb up the 2 1/2" to 3" branches and larger, setting them aside, while anything smaller is brush for burning.  So, I'll usually end up with a pile of each, larger stuff with little to no brush for the firewood pile or the trench, and small tangly stuff for the open pile method.

A trench burn using mostly untrimmed douglas fir limbs worked adequately well.  Better than very spreading tangly type branches, but not quite as well as lengths and chunks of wood without any small branches.
A trench burn using mostly untrimmed douglas fir limbs worked adequately well. Better than very spreading tangly type branches, but not quite as well as lengths and chunks of wood without any small branches.

Trench v.s. Pit Shape:  You could just dig a round pit, and that might be good for small wood, and especially small chunks like lumber cutoffs, but the long shape allows burning of long wood without cutting it up which can be a huge savings if long wood is what you've got.  It of course works fine for short wood too.  I haven't done a burn in just one end of the trench, but it seems like it should work fine as long as the open end of the fire has wood added to it same as the top.  If nothing else, the trench could be blocked with dirt of bricks for small burns of short stuff.

Other options:  FYI, this is based on the Japanese Cone Kiln concept, and you can also do it in other containers, like a webber BBQ for micro scale (be sure to seal any holes on the bottom).  I think you could also use an old wheel barrow body.  You can see Backyard Biochar for more on the cone kilns and other simple methods.

The burn requires maintenance, but not constant maintenance, so bring a book or a project to work on.

Summarizing:Between this and the open burn pile method in last week's video, a lot of wood types that most people have access to can be charred easily, with a minimum of preparations, planning or technology.  Considering the simplicity and low inputs of these two methods, there seems little reason not to turn the woody resources that accumulate around a homestead, or even backyard, into charcoal instead of ash.   That is my main message here.   You could of course turn smaller stuff into compost, but since charcoal can serve some of the purposes of organic matter in the soil (nutrient reservoir, microbe housing, moisture holding and soil texture changes)  but permanently with a one time applications, it's worth considering charring it in your webber for a while, or some of it at least.  It's not a complete substitute for organic matter, but it should, in theory, help you get more out of the organic matter and other nutrients you add to the soil in the future.  I add some organic matter to the soil, but I consider the most important the plant roots that are left behind after every crop.  

Anyway, that's more than enough said.  Most of what you need to know is in the video...

Posted on October 4, 2014 and filed under BioChar, Forestry, Garden Stuff.

Simple Biochar Production, and Grape Reviews, a Few Videos

Yay, burn season is here!  Just uploaded a few videos.  A couple of short grape variety reviews, The pretty darn good Glenora and the excellent Reliance (of which I'm eating some right now, and they're super tasty!).  And a somewhat long winded, but cool, video of burning a top lit open burn brush pile to make biochar (Which Kelpie of Backyardbiochar calls TLOB).  This is one of the two charring methods I've been messing with, the slope sided pit (or container), and the open top lit piles.  I think each has it's merits, but probably more importantly, each might be better suited to certain materials that people commonly have.  Both can be scaled up and down in size and neither should produce a ton of smoke if the wood isn't either soaking wet or green.  A pit burn video should be forthcoming.  Hopefully I'll get better at shooting and editing video, learn to talk faster and develop a video personality at some point.  In the meantime, pop some popcorn and check it out. No Guinea Pigs were harmed during the making of these videos, although some chickens were verbally assaulted.

Sloping Pit Charcoal Kiln and Agave Roasting

charcoal cone pit headerIn the comments on the biochar experiment post, Lars mentioned Japanese cone kilns.  I checked them out on Kelpie’s cool blog, Green Your Head and they do indeed look way cool.  Although slapping a crude one together out of sheet metal would probably be pretty easy, Lars had just simply dug a pit in the same shape.  I tried Lar's pit idea the other day, burned some charcoal in it, and learned a few things that I want to pass on.  This is slightly premature compared to most of my post, which are typically backed by a bit more experience and contemplation, but I'd like to get this idea out there more.  There is very little posted about it anywhere on the net, but it seems very promising, accessible and meets a lot of criteria for a good charcoal production system with very little effort. Commercially available cone kiln from Amazon Japan

Part one.  Sage, Agave and fishes (which have little to do with charcoal production.)  If you are interested in burning charcoal and have a short attention span from internet overstimulation, skip ahead!

When I was in my 20’s I spent a lot of time backpacking out of Big Sur, on the coast of Central California.  One of the common plants is Black Sage, White Sage’s little known, and much more potent sibling.  I've always loved Black Sage and much prefer burning it to the white.  When I moved here, I got some cuttings from someone and rooted them so I could have it around me.  The scent still evokes a lot of fond memories from those good times out in the mountains.  At the time, I lived in the Santa Cruz mountains and used to pick Black Sage and tie it into smudges.   I now have quite a few plants growing, and tying Black Sage smudge sticks is one of many crafty cottage industry occupations that help bring in a little income around here.  Most sage bundles are tied with cotton thread, wrapped in a spiral.  That was way too domesticated for me  back then, so I tied mine off with another plant I harvested in the Big Sur area, Yucca.

Black Sage

When I’d go out backpacking, I’d always harvest some yucca leaves on the way in to camp, pound them on a log by the river, and wash them clean of pulp to extract the long fibers.  I’d twist those fibers into a cord, attach that cord to a stick, add a couple feet of fishing line on the end.  The hook was nearly always a crude fishing fly I'd make by wrapping on whatever bits of feathers or fur I spotted on the hike in.  My fishing kit fit in a tiny pouch, and that’s all I had to carry.  My crude makeshift fishing rig worked awesome!  Wow did those fish bite.  Anything that remotely resembled a bug in the water got hit.  That is elegance.  extremely effective, low input, low cost, less junk to carry, connects me with the environment, builds skills, very little landfill material.  Anyhoo, I always brought out some extra fiber or yucca leaves with me when I eventually made my way back to civilization, and ended up using yucca to tie up my sage bundles.  The practice stuck.

There are several ways to process yucca.  You can pound it fresh with a wood mallet on a smooth log and repeatedly wash and scrape it.  (the pulp is soapy, so you can wash your clothes or dishes while you’re at it.)  The pulp is somewhat tenacious though, so it’s easier to clean off if it is softened by either cooking it, or rotting in water in a process known as retting.  Retting in water is pretty easy, but it takes a long time, and boy does it stink!  The fibers don’t absorb the smell at all, but hands sure do.  If left soaking too long, the fibers are also attacked by bacteria and weakened.

Up around these parts, there isn’t any yucca, but my neighbor Rob grows a lot of Agave americana, a large plant related to yucca which is also used to make tequilla.  Agave americana is not the best agave species for fiber, but it is decent and good enough for tying sage bundles.  I recently harvested some leaves over at Robs garden, an impressive meandering wild affair built up on a bare skim of soil over a serpentine rock  outcrop and consisting only of the toughest most drought resistant plants.  I wanted to bake the leaves because the last batch I tried to ret didn’t work out that great, and it’s winter so it could take months to ret a leaf that is 2 to 3 inches thick in some sections.

agave leaves

 Ok, on to the charcoal kiln:  I couldn’t just build a cone kiln.  As soon as I saw the shape of the cone, I knew I’d be spending a lot of time cutting wood to fit it.  That is a problem with many charcoal making apparatus.  Fuel sometimes has to be reduced to a certain size.  I figured that the principal of the Japanese cone kiln ought to work just as well (and actually better for my purposes)  if the shape were longer.  With a longer kiln pit, much less wood cutting would be entailed.  I don’t mind doing work to get what I want.  I’m not workophobic.  I like cutting wood.  But I like getting shit done too, and cutting longer wood means more wood cut at the end of the day, which equals more charcoal.  I also like efficiency.

 So I put agave leaves and charcoal pit together.  I could dig a long pit kiln, burn the long wood and use the residual heat to roast long agave leaves to soften them up for processing out the fiber.

Ideally the kiln would have been even longer for even less wood cutting (UPDATE: which I've now done and it was great for long unprocessed limbs with twigs and all), but I didn’t have a ton of wood set aside to fill it this time around, and didn’t need a huge pit to cook the leaves in.  I think the opening was probably about 6 feet long and sloped down from there on all four sides.  I didn’t screw around trying to make it nice, even though I had already generated ideas about how to best build and run such a pit.   This run was all about observing what did happened, rather than second guessing exactly what was going to happen.  I knew I’d learn something by just digging a hole and going for it.  I lined the bottom of the pit with bricks to retain heat for roasting the agave.  It is sometimes possible to use just the heat stored in soil to cook things in the ground, but I knew it wouldn’t be adequate in this case, especially since the ground was already wet.  I had doubts that one layer of bricks would even provide enough mass for heat storage, but I just left it at that.  I think more mass would have been better, but it worked okay.

The fire was built and maintained until the pit was fairly full.  The coals were then raked out (most of them anyway) and a few scrappy sacrificial leaves laid on the bottom against the hot bricks and coals, followed by the remaining leaves.  About a gallon of water was thrown on for steam, and the dirt was piled back on as quickly as possible.  No really, as quickly as possible, like all out, fast as you can.  (No pictures of putting the pit together, since I was rushing in order to retain precious heat.)  The charcoal was quenched with water on the ground.  A small brush fire was built on top of the pit for about 8 hours to keep heat in.

This is toward the end of the burn.  I could have fit at least two more layers, but I was running out of wood.  Note the close spacing and attempt to cover the top pretty well in order the shield the coals below from receiving too much air.


Here is some of what I learned.

The cone kiln concept works.  The principal is so simple that I’m surprised I hadn’t heard of it before and almost surprised that I didn’t think of it myself.  You start with  a fire and establish a layer of coals covering the bottom.  When each layer is almost burned to coals, another layer is added.  Each new layer effectively uses up incoming oxygen before it can get to the coals below, thus putting them out, or causing them to barely burn.  You can see this effect in a brush burn pile.  Generally there is a good pile of unburned charcoal in a burn pile when the flames subside, and it takes up to a day or more to finish burning out.  That is with piles that are managed for less smoke by piling stuff on one layer at a time as the fire burns, which is how I usually do it.  I don't like making piles way ahead and burning them, because lizards, frogs, salamanders and snakes all move in and get burned up.  A brush pile is a wildlife magnet.  Kelpie builds brush piles and burns them from the top down to reduce smoke and produce char.  The cone pit burns with very little smoke.  Low smoke is a huge departure from most primitive charcoal making methods, and one of my criteria for a good system of char production.  You could probably do this in many backyards without raising any eyebrows or calls to the fire department.

I think that using wood of similar size for each layer is important.  Each new addition should burn down fairly evenly, that is with all pieces burning at a similar rate.  If half the wood is one inch diameter and the rest is 3 inch, the one inch material is going to be burned to ash by the time the 3 inch stuff is burned down enough to add a new layer of fuel.  This principal probably would also apply to differences in wood species and condition, i.e. oak mixed with pine, or green mixed with seasoned.

The layer of wood added should be tightly spaced and/or thick enough to adequately smother the fire below.  Think of each layer of wood as an intercepting shield.  the shield should adequately cover and protect the layer below from infiltrating air.  I chopped the pieces to fit as necessary, and packed them pretty close together.  I left just enough room between pieces to let a little air in between them to keep it all burning cleanly.  More experimentation should be revealing as to what can be gotten away with.  At some point too much attention to detail is going to cost more than it gains.

Square corners are an issue.  I should have seen this one coming.  Square corners create cold zones.  Visualize fire in a rounded corner, v.s. in a square corner.  The rounded corner creates no cold zone and heat is radiated back into the fire in a parabolic effect, like a satellite dish, or solar dish cooker.  I had trouble filling the squared corners with wood in order to keep a hot fire in them.  The corners also ironically tended to burn out underneath once they did get going due to too much oxygen infiltration.  In short, they seemed hard to manage.  Not horrible or anything, but they seemed unpreferable.  I’m not sure one couldn’t effectively manage a pit with square corners, but it seems more finicky at the least.

The shallowly sloped walls are there for a reason.  I mean duh, we’re dealing with Japanese technology here, elegant and effective.  I think the shallowly sloped walls are there because they lead to more effective covering of the previous layer.  Wood on top extends out past the previous layer shielding it from oxygen more effectively.  I could tell I was having losses on one side that was dug with a pretty steep wall, making it more difficult to cover the lower layers adequately.  That's what it seemed like anyway.  Maybe some other reason will become apparent with more experience, but I think that is the reason.

Dirt is messy.  I dug this pit, barely cleaned it out, raked the charcoal out onto the ground and dumped water on it.  It was messy.  Lots of rocks and dirt in the charcoal,  and grass and leaves everywhere.  It would have been much easier to get the charcoal out of the pit if the sides were smooth and clean.  And, it wouldn’t hurt to have a clean area to rake coals out onto.  Dirt and rocks can be washed out by throwing all the charcoal in a tub of water and swirling it around for a second.  All the rocks and nails or whatever will fall to the bottom, and the charcoal is scooped out with a colander, but it’s a messy hassle.

I plan to test all of these observations and assumptions in the future.  For now, I feel like I know where to go next.  If you want to experiment with the cone kiln principal, here are some bullet points.

*Use shallowly sloping sides.  Just like the free standing metal kiln in the picture above.

*If you dig a long pit, make rounded corners.  More like a diminishing oval than a diminishing rectangle.

*Dirt can be dealt with and may not even be a significant hassle in some contexts, but if the kiln is to be used many times (as for biochar production) paving the sides with brick or pasting it over with a clay sand mix might be in order.  Adding that mass would also make the pit into an effective oven as well.  With the right sized pit and enough mass, you could cook large amounts of food, a whole animal, agave leaves, or whatever.  It’s nice to be able to use all that residual heat for something, even if it's just to set a pot of beans in there overnight.


The metal cone kilns are way cool and have the obvious advantage of portability.  But they are also expensive, if you can even find one to buy outside of Japan.  You can probably have one fabricated out of stainless steel at a metal shop.  You could also probably whip a decent one up out of sheet metal with a pop riveter and a pair of metal shears, which I hope to get around to (caution, don't use galvanized metal.  Zinc is toxic when burned.)  It doesn’t have to look good, though the seams might need to be reasonably tight to prevent air infliltration.  The pit is very attractive as an idea.  Anyone can dig a pit, and many could effectively line it with stone or masonry.  A pit is going to be cheap or free, and you can use the residual heat to do other stuff.  One idea I had was to build an above ground pit.  Here I can only burn in the rainy season, so a lined “pit” built in a raised mound of well draining material like gravel or gravelly soil, would be ready to use all year, even when the ground is soaked.

My yield of charcoal to fuel burned seemed decent, and there were almost no unburned pieces remaining.  I think there may be room for improvement in yield with better management or feedstock, but I'm happy enough with what I got out of it.  I want to go other places with this concept eventually, with as much function stacking as possible.  For instance, burnt clay is also a great soil amendment and could be produced by lining the pit with clay and chipping it off to add a new layer each time the pit is burned.  Maybe a few shells could be added to make some agricultural lime while we’re at it.  Wish I'd thought of that this last time around.

Many char producing systems will only take one size/shape of wood.  In the cone system, it seems like each layer should be composed of pieces of similar thickness, but otherwise, there is a lot of leeway in fuel size and shape.  Some methods also use up extra fuel in order to burn the charcoal.  Not using extra wood to generate adequate heat, and being relatively efficient, are other good design parameters that the cone kiln, in spite of it's simplicity, seems to do pretty well with.  In producing char, it is probably going to be best to have a variety of options here for the different types of feed stock that might be produced on 40 acres of varied species, combined with pallet and scrap wood, wood chips I can scrounge up, etc.  For now, the cone kiln concept seems well worth pursuing further, and a great addition to the stable.  I'm actually pretty excited about it, because it possesses a lot of good points, combined with simplicity/accessibility.   I’ll leave you with some agave processing pictures.

(edit:  Since writing this, I trailed some links back to find Josiah Hunt is doing something similar in Hawaii.  His burning style is different, but pretty much the same concept.  Check it out.!topic/biochar-hawaii/ohoqDcuHMiQ )

Roasted leaves look like dead fish.

agave leaf structure

scraping agave fibers

Some cleaned fibers.

Finished smudge sticks.  Frequent discreet ties mean no unravelling.  My smudge sticks are ridiculously dense, ridiculously intense and won't unravel when you travel.

Posted on December 21, 2013 and filed under BioChar, Forestry, Garden Stuff, Uncategorized.