The Permaculture Podcast

    Episode 1326: Biochar, Gasification, and Woodlot Management (Permabyte)


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    This episode is about my recent field day on “Renewable Energy for the Farm: Charcoal Production for Power & Fertility” where we covered three main topics: charcoal & biochar production, renewable energy, and wood lot management. The Pennsylvania Association for Sustainable Agriculture and Village Acres Farm made this field day possible. Before we begin, I’d like to share with you a little bit both.

    The Pennsylvania Association for Sustainable Agriculture, abbreviated by locals as PASA, was created in 1992 as a way to promote profitable farms that produce healthy food while respecting the natural environment. PASA is the largest statewide, member-based sustainable farming organization in the United States. This organization does a ton of good work in Pennsylvania with a variety of programs, but the two that have the most impact on me, and I think is of value to other permaculture practitioners, the is Farm Based Education and the Farming for the Future Conference. The farm based education is how I went to the Energy for Your Farm event and PASA holds these kinds of activities all the time. A few coming up as I write this are: “Forest Farming for Wild Edibles: Ramps, Nettles, Fiddleheads, and More”, “Animal Handling Workshop for New & Beginning Farmers”, and another Renewable Energy for the Farm focusing on micro-hydro. All of these have application to people interested in permaculture, and let you get out and see farms in operation. This last part matters because if you aren’t farming, or near a rural area, it’s hard to get a grasp on the broadscale picture. These events also let you network with people interested in sustainable practices.

    All those ideas are at play with PASA’s Farming for the Future conference. Held shortly after the new year in central Pennsylvania, this conference condenses what you can do throughout the year via Farm Based Education into four amazing days of workshops, lectures, keynote speakers and other events. Not to mention that this event draws around 2,000 people from all over. You’re likely to find someone who knows more about any particular interest you might have relating to sustainable agriculture, and is willing to share what they know.

    But neither of these resources would be available without the aid of the farmers who make it happen. For this most recent workshop, I was at Village Acres Farm. An organic operation in Mifflintown, PA, run by Roy and Hope Brubaker, they recently transitioned into a partnership with Debra, Roy’s daughter, making this a multi-generational operation that is also inter-generational as other family members own and operate Blue Rooster Farm nearby and provide meat for the on-farm CSA. Another interesting aspect of the farm, and something I wouldn’t have learned about without this farm based experience, was the FoodShed. Though a simple name, the building this name encapsulates is a gorgeous timber framed design with a radiant floor, passive solar lighting, and other energy efficient and sustainable features. Here they serve food from the commercial kitchen and hold a variety of events. This is where we had lunch that day, and I was very thankful that the family members who served us were understanding of food allergies.

    We’re almost to the material from the workshop, but remember, this show is listener supported. Find out how to lend a hand by going to: and remember to like the show on facebook, or follow me on twitter: @permaculturecst.

    Now then, the field day. In covering this I focus mostly on the question and answer material we covered during the class. I say this because charcoal and biochar production is something you should experience to get a understanding of. So, give a listen, look at the pictures on the website, check out some videos, and sign-up for a workshop. This is a great hands on project for any gardener, farmer, or permaculture practitioner.

    Gary Gilmore with his Charcoal Gasifier in the background.

    Gary Gilmore with his Charcoal Gasifier in the background.

    Our workshop was taught by Gary Gilmore, a Forester for the Pennsylvania Department of Conservation and Natural Resources, and, as someone identified him that day, a “char-vangelist”. He’s passionate about the possibilities of charcoal and bio-char for a more productive, local, and thriving culture. So much so that it’s almost infectious. His background combined with the science involved from his current occupation tied together such that the session was science and numbers heavy. I’m including the pieces I understood enough to write down and will include everything I can.

    We began the day, after introductions, with charcoal and bio-char production.

    What is Charcoal or Biochar?

    Both are essentially the same thing: carbon, along with some oxygen, hydrogen, and minerals, left over after burning the source material in a low-oxygen, or oxygen-free, environment. They are very similar end products and the distinction is in how we use them.

    Charcoal is larger and used primarily as fuel. If you think about lump charcoal, not the briquettes, this is about what charcoal produced at home looks like when it first comes out of the kiln. Mr. Gilmore, during the second section of the class, showed us his grinder that he uses to make the charcoal a uniform size for gasification.

    Bio-char, on the other side, is very fine, to the point of resembling black dust or powder that is in turn used as a soil amendment by digging it into the garden. This fine material has a much much larger surface area by volume, allowing for more nutrient holding, water retention, and the other benefits currently being researched.

    Though the terms can be used interchangeably, for this conversation, charcoal is for fuel, and has one set of characteristics, and biochar is used for a soil amendment.

    What about Direct vs. Indirect production?

    TLUD Direct Production Kiln.  Primary air comes in through the bottom.

    TLUD Direct Production Kiln. Primary air comes in through the bottom.

    Direct production is where you burn wood directly in order to produce charcoal. This can be done as simply as with two metal barrels, one on the bottom to hold the wood with holes in the bottom for primary air intake, and another larger barrel on top acting as the afterburner to create cleaner combustion. This is known as a Top Light Up Draft gasifier, or TLUD, as the fire is lit from the top and burned downward, which causes gasification, and the gases move up and are ignited. The primary air from the holes in the bottom of the barrel allow the wood to burn, while secondary air, coming up through the crack between the two barrels where they meet, is the secondary air flow that aids final combustion. This design is very very clean burning. Once it got started there was little to no visible smoke.
    All of the demonstrations at this workshop were with this TLUD style of direct production.

    Indirect production is what you might see where there’s one barrel inside of another, or a specially built biochar kiln where an external fire is applied to the

    TLUD Kiln with afterburner in place.  Very little smoke.

    TLUD Kiln with afterburner in place. Very little smoke.

    material to be converted into bio-char. In this case heat is applied from the outside to “bake” the material inside, driving off volatile gases, and turning it into charcoal.

    What do I use to make charcoal or biochar?

    Mr. Gilmore recommended making Charcoal out of wood that had air-dried for one year, which means it has about a 20% moisture content, considerably lower than fresh cut wood. This wood should come from the heart of the tree and not contain a great deal of bark, as bark contains more minerals which leads to more ash. Instead, bark is excellent for biochar.

    Using indirect production, you can use just about any garden refuse you want, because the process doesn’t require the material being turned into biochar to fuel the process directly. Material with higher mineral content, such as wood bark or green plant material, work well in this case, as the mineral content helps to build the soil.

    What is the difference between High Temperature vs. Low Temperature production?

    High temperature production, via the indirect method, produces a higher quality fuel because the pyrolysis drives off more of the oxygen, hydrogen, and other materials. High temperature production is not appropriate for use as bio-char. Low temperature production, in the 600-800 degree range, produces a material that is around 70% carbon, 30% other materials, and is useful for both fuel and soil amendment.

    The direct method uses some of the source material as fuel, leaving you with around 60% of the starting weight in charcoal. The indirect method is more efficient for converting to charcoal, leaving you around 70% of the starting weight, but requiring external energy to produce, leading to a potentially less efficient system. I have seen indirect methods that cycle the volatile off-gases back into the firebox to increase efficiency. Time and tests will tell which works better, but to get you started the direct method is great.

    I’m interested in biochar production as a way to turn multiflora rose and mile-a-minute into something useful for my garden, as they are rather pernicious non-natives that quickly spread and smother out other vegetation. In my interest to design myself out of the system, reducing them in my area is important while the system establishes itself and can better minimize this kind of rapidly spreading plant.

    How much charcoal or biochar can you get from your source material?

    I don’t have number on garden waste, because of how much this varies from plant to plant, when you cut it, etc. However, for wood, it’s a little more straight forward, though of course your end results will vary, but your end result is about 40%, by weight, of what you started with.

    For those of you interested in the numbers, I came to this figure because Mr. Gilmore recommended using wood that had air dried for one year, which is about 20% moisture, then burned through direct production. Fresh wood is around 50% moisture. So if you start with 10 lbs of freshly cut wood, after 1 year you’ll have 7lbs of wood ready to go in the kiln. You lose another 40% through pyrolysis, 20% being the moisture driven off and 20% as fuel, resulting in about 4lbs of charcoal in the end.

    Charcoal, biochar, and climate change.

    When we hear conversations with people such as Connor Stedman or Eric Toensmeier about taking action to mitigate climate change, with things like carbon farming, what role does charcoal production and biochar play in that?

    Charcoal represents, to the best of my understanding, a carbon neutral fuel source if, and that if is very important, we use well managed wood lots and industrial waste, such as lumber mill refuse, to provide the base material in a way where we grow what we burn at an equal replacement rate, while using that material for both fuel and charcoal. For every pound of material harvested, we need a pound of growth to replace it. In this way, the wood takes carbon out of the air to grow and then returns it when combusted. That’s a simple recycling of material. Where this doesn’t work is in using fossil fuels to burn material grown specifically for charcoal or bio-char production.

    Where things get more interesting is in the using this as a soil amendment. Carbon, in the form of biochar, is very very stable in the soil and can last for centuries. There’s evidence that the terra preta from which the idea of biochar arose, is pre-columbian in nature and dating back over 1,000 years ago. That’s a long time for this to be locked up in the earth. According to Mr. Gilmore, for every pound of carbon sequestered in this way, we keep upwards of 3.5lbs of CO2 from forming due to decay of the original material. And it can be done on a home scale.

    However, and I hope this points to the question about whether or not this is really carbon negative, a point raised by Brent Virrill on the facebook page announcing this episode, the value Mr. Gilmore gave is correct about 1lb (454g) of carbon sequestering around 3.5lbs (1.66kg) of eventual CO2, a figure confirmed by two friends who know a lot more about chemistry than I do, is an ideal theoretical maximum conversion of carbon into CO2, which is not reflective of what actually happens through the biological cycling processes that lock-up and then release CO2, so the actual ratio of sequestration is probably lower than that 3.5lb figure. Also, as low temperature biochar production results in a product around 70% carbon and 30% other, you’d need to bury 1.4lbs of bio-char to sequester that 3.5lbs.

    In creating biochar, for it to be carbon negative, the inputs need to be small enough in carbon output relative to the storage potential so the inputs don’t outweigh the sequestration value, which may be one of the issues of industrial versus small scale production of bio-char. Gasoline releases 19lbs of CO2 per gallon burned, while diesel releases around 22lbs. Using gasoline equivalence figures, natural gas requires around 128cu/ft for the same amount of heat energy (measured in BTUs), which releases 15lbs of CO2 on complete combustion, and bituminous coal requires 10lbs and releases 28.6lbs of CO2.

    Now, with all these numbers rolling around, you can see why using gasoline or diesel to transport the material to a central location, then moving the final product out again to where it’s used, and then digging it in with machinery can quickly deplete the benefits of burying biochar in the ground for sequestration on an industrial scale. Once you include fossil fuels to create this material there’s even greater loss of how much carbon is stored versus created.

    Though this was a quick shot that’s number heavy, I was going to include a lot more of math here to break down how charcoal and biochar production converts between these different fuel sources, but I wasn’t confident I had everything right. The few pieces I could find that gave numbers don’t show the work from point A to B and I don’t want to extrapolate that. If someone knows the numbers behind how much energy is required to convert wood to charcoal and can do a comparison between the different fuels, please let me know.

    But, bio-char has other values to us when buried beyond just carbon sequestration.

    Biochar in the soil.

    So, what does biochar do when we add it to the soil? The reported benefits are many, here’s a sample:

    Enhanced plant growth.
    Suppressed methane emission.
    Reduced nitrous oxide emissions.
    Reduced fertilizer requirements.
    Reduced leaching of nutrients.

    These last three in particular were of interest to Mr. Gilmore because of the impact they have on waterways regarding nutrient runoff. As I’ve mentioned before, reducing the daily total load from run off into streams and rivers in my watershed is very important because of the impact it on the Chesapeake Bay. Integrating biochar and reaping these benefits is one pathway to do this.

    Two things you need to do in order to use the biochar. The first is to make sure it is a small size, like dust or grains of sand. This is where using garden waste for conversion comes in because grass and leaves are finer grained to begin with and power readily. Whatever you need to do to get them to this point, go for it. I’m thinking my 3yo son and a butter churn filled with charcoal is the ideal way to reduce charcoal to powder, but Mr. Gilmore commented about mixing it with wood chips and spreading it over a section of his driveway and letting vehicle traffic reduce it over time. His current process is to add the course charcoal to his horse stalls where the horses tramp it down, while also mixing their urine and manure with the charcoal.

    This leads to the second point recommended by both Mr. Gilmore and Dale Hendricks, another biochar enthusiast who attended the course to assist, to charge the bio-char. Charging is introducing an initial source of nutrients into the biochar before incorporating it into the soil. In addition to animal pens, there was a suggestion of adding biochar to a composting toilet in place of brown material, or as the main absorbant in a urine bucket, or mix it with compost or compost tea.

    One thought Mr. Gilmore had, and I’m interested in experimenting with or hearing from you if you’ve done so, is if you can use charged biochar directly as a growing medium, without any soil or other additives. Have you tried this? Let me know.

    Gasification as Energy

    Mr. Gilmore's homemade charcoal grinder.

    Mr. Gilmore’s homemade charcoal grinder.

    After lunch we talked about using charcoal as a fuel source. Opening this conversation Mr. Gilmore began by holding a can of gasoline and bundle of wood. The two fuels are roughly equivalent in energy: one gallon of gasoline to 25lbs of air-dried, seasoned wood. If you burn wood directly, you get about the same amount of energy. But, you can also use the wood in a wood gas generator to create syngas, short for synthetic gas, by using the pyrolysis method to generate charcoal and biochar to drive off the volatile gases in the wood, which an internal combustion engine can use directly with little to no modification. Another option, is to create charcoal and use it for gasification into syngas to run an engine. Of these three methods, Mr. Gilmore prefers using charcoal gasification because the charcoal gas generator system is less complicated than a wood gas generator, and will still run his engine directly.

    Rather than get into the full details of the difference between these two systems, what I can say is that the benefits of a wood gas generator is that it is more efficient in time because you don’t need to convert you fuel from wood into charcoal, and more efficient in generating gas because you don’t lose the 20% of so you would in burning the wood to charcoal. However, the wood gas generator is more complicated because you need to include traps in the system for the moisture being driven off as well as the ash, tar, and other materials that can gum up or degrade an engine. Also, because of inconsistencies between outputs from various woods, a way to control the gas flow into the engine is also important.

    If you want to learn more about wood gasification there are websites devoted to it, and there is also a book recommended during the workshop called “Have Wood Will Travel” written by Wayne Keith. You can buy it directly from Wayne at his website,, for the price of $50. Seeing what Mr. Wayne is doing by driving with wood gas already has my mind turning for other, down the road, projects.

    But, what I got to see the day of the workshop was Mr. Gilmore’s functioning charcoal gasifier, which he ran to show us that yes, this does work, and how everything was setup.

    The burning charcoal gasifier.

    The burning charcoal gasifier.

    The basis of the system was a barrel to burn the charcoal in, with an air inlet consisting of a piece of 1” threaded pipe, which I believe was stainless steel, going through a homemade bulkhead into the barrel, about a ¼ of the way up from the bottom. Attached to the outside of this pipe was a valve. On the inside, this was covered with a larger piece of iron pipe with about a quarter of it’s circumference removed, lengthwise, to create a shield to cover the inlet. Charcoal is added on top and shaken down into the bottom. The lid is then added, which has an outlet that attaches via a piece of plastic tube to a filter can. Inside the filter can, from top to bottom, is a piece of wool fabric sewn to a metal wire shaped to fit the top of the can fairly tightly. Beneath this is a thick section of open cell foam rubber, and beneath that wool fabric scraps. Mr. Gilmore uses wool as part of his filter based on some research he read from Australian charcoal gasifiers that wool is one of the better natural filters. The filter connects by more tubing to an electric fan that creates a draw to move the gas from the gasifier through the filter to the engine, with the tubing from the fan running directly into the carburetor for uptake by the engine. The exhaust from the engine is then routed back to a valve connected to the inlet so some of the exhaust gases can be recycled, producing cleaner combustion. The valve allows for control of this gas flow being recycled to control the combustion temperature, as the exhaust gases are hotter than the charcoal gas being generated. From there, the final gases run out through a combined radiator and exhaust.

    One note here is that the charcoal gas for most of the burn is fairly cool, under 120 degrees. The piece of plastic pipe Mr. Gilmore uses to connect the gasification barrel to the filter is one of his fail-safes, because it melts at 120 degrees. If something happens that the system temperature rises too much, this pipe fails and prevents damage to the other components.

    Once everything is setup and connected, it is lit through the inlet pipe near the bottom of the charcoal barrel. Within maybe a few minutes of lighting the system, Mr. Gilmore started the gasoline engine on the charcoal gas and allowed it to run for 15 or 20 minutes while we talked about and explored how it worked.

    The engine attached to the system was a standard, unmodified 10hp gasoline engine. Using charcoal gas, the system produces around 8hp because charcoal gas is less energetic than gasoline with a resulting loss of around 20 to 25%. He estimates he could run this engine for about an hour to an hour and a half on around 6lbs of charcoal, whereas he has a larger 25 hp engine, with a resulting 20hp output, that runs for around 30 minutes on the same amount of fuel, all off of the basic system he showed us with a 1” inlet and outlet for air and gas flow. He thinks that a 25hp base engine is about the limit for a 1” flow setup, but that by increasing the inlet and outlet size it scales up easily, with a similar increase in fuel consumption as well, so you’d need to include a larger gasifier unit, filter, fan, and so on as things get larger.

    What really got me about this system is the potential to do real work with unmodified or lightly modified existing machinery, without fossil fuels. These aren’t novelty applications, as was reinforced by Mr. Gilmore talking about running his 25hp walk-behind tractors on charcoal gas, and he even ran a vintage air-cooled beetle Volkswagen on it, traveling about 11 miles in his tests. That’s one side, the other is that this can be used to generate electricity as we saw from a pair of lights attached to, and run off of, the charcoal gas demonstration system. This is small scale portable solution that could be used now in emergencies, or off in off-grid arrangements as back up to solar and wind, or as a possible long term solution for local generation of power.

    And, as was stated several times during the workshop, cool and cold weather is the time to produce charcoal and biochar from the previous year’s brush and scrap wood, so you could potentially build a charcoal kiln as a heater so as not to let all that energy go to waste. Creativity with good design leads to many many yields in this system. One participant in the workshop commented about using the exhaust from a gasifier to warm and elevate the CO2 levels in a greenhouse. Though I’m sure there would have to be safety measures in place, so as not to cause safety issues due to the carbon monoxide and other gases in the exhaust, it is a possibility.

    Which, is where the warning goes, making one of these systems is not inherently dangerous, but there are risks involved. If you don’t feel comfortable with something, don’t do it! Work with someone with more experience to build or design your solution and learn to operate it safely.

    I’m also not going to argue that these are the most efficient systems around by any means for producing useful work, creating electricity, or the time required to do so, but they remain options that can make a difference for the choices we make in our desire to build a better world. It’s not about a one size fits all solution for everyone, but a series of options to use where appropriate to build more flexible alternatives.

    Champion TLUD stove.

    Champion TLUD stove.

    That also goes for another use of gasification, and that was a TLUD stove design Mr. Dale Hendricks of Green Light Plants shared with us that day. The particular stove he brought is called a Champion TLUD and is based on an award winning design from a cleaner burning stove competition. The idea behind this is the same as the wood gasification for charcoal production, and the stove even produces a small quantity of charcoal, except in this case applying the designed to a small scale for cooking.

    One note here is that if you use this type of stove to cook and produce charcoal, you’ll want a bucket of water several times the size of your stove with water in it to quench the charcoal in when you are done cooking. A handle on your stove to lift and move it probably helps too. In his demonstration Mr, Hendricks used compressed hardwood pellets for fuel, and I thought it was a simple way to use pellets that might have been damaged by moisture and no longer usable in a regular wood pellet stove. I say this because I have several bags sitting around at the moment a friend gave me after their basement flooded and a stove like this fits easily in my thoughts.

    This TLUD stove is another option to include for emergencies, or potentially to replace other forms of stoves in off the grid or no-grid situations. There’s plenty of information available on how to build your own if you are interested, as well as people making them for purchase. Consider experimenting with this and adding your experiences to the growing pool of knowledge on these simple, yet revolutionary, systems.

    Woodlot Management

    That brings us to the final part of the workshop material, which was woodlot management. Being a forester by training, Mr. Gilmore shared with us how to apply the way a forester thinks with our production of charcoal and biochar.

    To that end we started with a conversation about invasive species that kill trees, such as the emerald ash borer here in Pennsylvania and other parts of the U.S. Knowing your local area and what threats there are to your trees lets you make choices. If a tree is highly likely to be killed, you can harvest it before that happens and make use of what you can, or be prepared to cut it down when it does die and know what you’ll do under the new conditions.

    From there we walked into a woodlot at Village Acres Farm, and began by looking up at the canopy, or over-story, trees to see which ones won the war for sunlight. The losers could be selectively harvested to open up more of the canopy to allow success to begin in that spot, and use the removed tree for charcoal production or some other means.

    But, before making that choice, after looking up, we looked around to identify the trees that were there. To see which ones are rare, so should be preserved, which ones are unique for some reason, such as trees having a unique or pleasant form, which ones you might consider invasive and want to remove, or which ones might be valuable for coppicing. Using that information, then make decisions on which to keep and which to remove based on your overall site plan and usage patterns.

    While doing so, be sure you don’t mine the woods for resources, because then a process that could be sustainable becomes extractive. Rather, make the choices so that you can regenerate the forest as you make use of it. One point Mr. Gilmore made was to not remove the down woody material on the forest floor. The twigs, sticks, and limbs we find resting against the soil play an important role in maintaining soil fertility and supporting fungi, so should be left. I was left with the impression that selectively removing and using trees had a lower impact on the forest ecology than scavenging for what can be found on the forest floor.

    Going back to the invasive, or non-native, or exotic plants for a moment, I’m of a mind that removing some of the more pernicious ones to you area, to help re-establish the succession of local woodlands, is important, and also provide a resource for bio-char production through the indirect method that could be quite useful for soil amending while leaving trees and other dense woody material in place. I know the native/non-native, native/invasive, native/exotic conversation is still open to a lot of debate and one we’ll keep circling around for a while. For me, thinking about the problem as the solution, and in turn obtaining a yield, converting this material that I don’t want into something I do plays a role in my long term strategy.

    And since I mentioned the word of a hot subject, we did touch on coppicing, but by this point in the day information was tossed around quicker than I could make notes. So here’s what I did pick up:

    – In Pennsylvania and other northern hemisphere cool temperate climate areas, the time to coppice trees is during the plants dormant period, which is the months of R: January, February, March, April, September, October, November, December.
    – Evergreens like pine or hemlock do not coppice.
    – Deciduous trees generally do.
    – Deciduous should be ones that do not form root suckers, such as locust or aspen. There were also comments that beech and birch do not coppice well, but I didn’t note why.
    – Trees mentioned that do coppice well: maple, oak, ash, willow, hickory, black walnut, hazel, and chinese chestnut.
    – To coppice, you want to cut the tree down to a stump nearly at ground level, perhaps a few inches high, and at a slight angle to allow water to run off and not rot the stump. This forms a new crown that additional growth occurs from.

    Coppicing wrapped up the conversation and brought the workshop to a close. We walked out of the woodlot, said our goodbyes, and went our separate ways.

    Listener Questions

    Now then, the listener questions, submitted by Brent via the Facebook page.

    Hugelkultur vs. Biochar

    “I would like to understand more about why hugelkultur is more highly recommended for colder climates, while biochar is recommended for warmer climates. I understand why you might not want to bury wood in tropical areas. Because there is no cold cycle, bacterial and fungal action are amped up in tropical soils and break down all organic matter faster. But I don’t see why biochar wouldn’t work as well in colder climates as it does in warmer ones, perhaps even in conjunction with wood.”

    To the question specifically regarding non-tropical regions: biochar works and there’s no reason not to implement it as part of your overall strategy where appropriate. Using the permaculture zone model, I wouldn’t dig it into zones 3, 4, or 5, but would certainly include it in the hole for trees and shrubs when planting them, and incorporate it fully in garden and production beds in zones 1 and 2.

    More broadly, I think what’s going on with hugelkultur compared to biochar is that hugelkultur is more widely understood as a technique and less intensive to implement, while still providing benefits such as a raised bed, improving the garden conditions, and building the soil. Though you can dig a trench to bury the woody material for the bed, it isn’t necessary. Pile it all in place, dump soil and compost on it, mulch it, let it age if so inclined, and eventually plant in it. I like hugelkultur because my children and I can collect the material in one place while playing in the yard, or I can start building a new bed as I find things without having to complete it all at once. Hugelkultur can also be taught in an hour or two and people can go home and start right away.

    Biochar, on the other hand, takes time to gather the materials, some equipment to create it in, even if it’s just a pair of metal barrels, and then remaining with it to manage the burn. Yes, you can do some other work while it’s burning, but should remain with it on fire watch. Once done, it needs reduced to a powder, charged, and then dug into the A and B horizons of the soil. This is considerably more work than hugelkultur, and limits implementation on a broader scale.

    Brent also asked about whether or not biochar is truly carbon negative, which I think I handled to some degree earlier. If you’d like more research and contemplation of that, please let me know and I can work something with more detail.

    “I wonder about the wisdom of single purpose biochar kilns. I see things on the internet, youtube videos, instructables, even products you can buy, and most especially kilns that charities are making for developing countries, and I cringe. All that energy that could have been useful for something is wasted to make biochar. Biochar is great and all, but wouldn’t it make sense to make use of all that heat?”

    I agree with you on the idea of search for other solutions and ways we can use that heat, but from the designs I’ve seen of single purpose biochar kilns they’re potentially an efficient way to convert non-woody material, like grass, dry leaves, or end of season plant stalks and so on, into biochar because they are usually an indirect means of production with a sealed chamber heated by an external source, allowing the moisture in the plant material to be cooked off and then convert what’s left into charcoal in a controlled way, something that isn’t as easy to do with this finer material in a direct system. These also allow the ash, and the mineral content contained within, to be collected as an added benefit to building soil with biochar.

    This goes back to one thing that Mr. Gilmore and Mr. Hendricks mentioned several times during the workshop: charcoal and biochar production is based on ancient systems we’re rediscovering in the modern era.

    What that leads me to is that making charcoal and biochar isn’t hard. Where the difficulty rests is when we start thinking about how to use all our knowledge in the current age and these big brains of ours to eek out the widest range of yields for the system like the most efficient kilns or determining which biochar is more effective for soil building. The designs that exist at this moment represent some of the earliest, simplest options we’ve come up with us as we figure all that out. As these design advance and we continue to learn we should be able to produce more, with less, and increase the benefits benefit from all the possibilities.

    Or at least, that’s my thought on it. What’s yours? I’d love to hear from you. If you have a comment or question about this show, a guest request, or want me to cover a particular topic, please feel free to contact me through any of the many ways available:

    E-mail: show [at] thepermaculturepodcast [dot] com
    Phone: 7one7-8two7-6two66
    A direct message on twitter: @permaculturecst
    A message on facebook:

    Pennsylvania Association for Sustainable Agriculture
    Village Acres Farm
    Gary Gilmore’s Youtube Videos
    Biochar @ Pbworks
    Wayne Keith – Drive on Wood
    TLUD (Biochar) Stoves @ International Biochar Initiative

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