Biochar: What We Need is in the Sky

blog-manipulating settingJanelle wanted me to generate a post about biochar; she liked the way I described it to a friend and thought my take on it might be helpful to a larger audience…does our blog readership constitute a larger audience?  Oh, well, it’s the largest we’ve got!

So what if I implied to you that the problem with the global climate change conversation is that we’re seeing atmospheric carbon as a troublesome burden, when really it’s a tremendously underutilized resource for solving the most pressing problems of agriculture?  Would that make you sit up and pay attention?  Agricultural activity over the past 10,000 years has acted to drive our precious soil carbon out of the soil and into the sky.  This has been a profound loss…we need to find ways to reverse this process and invite the carbon out of the atmosphere and back into our soils where it belongs; where it is so badly needed.

IMG_5321I’ll start my explanation with a few paragraphs (I’ll try to be succinct) about biochar facts and history.  Pyrolyzed (charred) wood has been used accidentally and/or purposefully for millennia by humans as a soil amendment and a fuel (as charcoal).  Char is created by partially burning wood…that is to say halting the combustion reaction before it turns the wood completely to ash.  Those little black chunks left over in your fire pit after a cookout…that’s char.  By manipulating the burn setting and process, a person can make it so that there is a whole lot of black stuff left over and comparatively little ash.  Traditionally this has been achieved by creating a smoldering fire with limited oxygen, and extinguishing the burn prematurely when the desired level of pyrolysis (charring) has occurred.

Medical practitioners and others will be familiar with another property of char…it is great at grabbing many kinds of chemical substances and holding on to them.  Typically the more reactive the substance, the more char wants it, so reactive toxins like heavy metals can be cleared from the body by ingesting charcoal.  I believe this is the process known as chelation.  It should not be done willy-nilly–so don’t go swallowing chunks of char as a bonus detox—because when char finishes with grabbing the most reactive stuff, it moves right into the less reactive stuff and grabs that, too.  So it can deplete the body of valuable minerals and the like if overdone.

You would think, then, that char would make a terrible soil amendment, since it is so hungry for nutrients.  Indeed it must be used with caution.  If you mix it with your garden soil straight from the fire, the reports are that there is nothing more capable of starving your plants in a hurry.  However if before you add it to the soil you “charge” it (fully stock its storage capacity) with beneficial plant nutrients, it becomes a wonderful nutrient reservoir that plants and soil microbes can draw from and deposit into over the long term.  So charging it with nutrients is what makes “char” into “biochar.”  This nutrient-bank function is one of the same roles that clay serves in the soil, but char is better at it and has other benefits.  Read on.

There is nothing more important in soil health than organic matter (dead bits of plants and other life-sourced matter).  Organic matter makes the soil lighter and easier for roots to penetrate and colonize, it provides habitat for the huge diversity and number of organisms that make up a healthy soil, it promotes healthy aeration and stores soil water and nutrients.  There are myriad types and sources of organic matter, each with its own properties.  Some stays in the soil only a little while before it degrades (fueling a plant smorgasbord of nutrient exchanges) and returns to the air as carbon dioxide, some stays around for several years, some for hundreds of years.  Pyrolyzed organic matter (char bits) is the most permanent type, lasting in the soil not for hundreds of years but thousands!  For agricultural systems purposes, then, it can be thought of as a permanent form of organic matter.  For the nation that has squandered its topsoil at devastating rates over the last century and a half, this should be a pretty attention-getting little factoid!

At this point it is worth asking the question:  Where did the plants and trees we make biochar from get their carbon in the first place?  The answer may surprise some folks:  From the air.  Atmospheric carbon dioxide.  The very same supply of carbon dioxide that is pressure-cooking our planet.  So put it together with me here:

  • There used to be a lot of carbon in the soil, in the form of organic matter.  That was good!
  •  We plowed the soil, allowing the topsoil to erode and promoting decay/oxidation of that organic matter, driving it into the air (one third of CO2 overproduction has been from this source).  That was bad!
  • We learned how to burn high-carbon fossil fuels for extra energy, releasing even more carbon and letting us plow even more.  That was very bad!
  • Trees and plants use atmospheric CO2 to build their tissues, reducing atmospheric carbon.  Yay!
  • Charring this plant tissue immobilizes it and renders it a permanent soil asset, keeping it out of the atmosphere over the very long term.  So the more biochar we hungrily generate to feed our starving soils, the more we solve our climate problem.  Holy Cow!


And speaking of cows, using a combination of prescribed burns (grasses pyrolyze, too!) and skillful rotational grazing is perhaps the most powerful way of reducing atmospheric carbon while building agricultural soils for the long term.  In fact, grass fires are part of how I got interested in biochar.  I had read about archeological digs in which there were found pieces of char from cooking fires that had lasted for many thousands of years in the soil, virtually unchanged.  It got me thinking about whether this process could be used to sequester carbon, especially if half-burned grass bits could be the material in question, since grass regenerates so quickly after fires.  So I fired up ye olde search engine and, sure enough, there was this whole body of knowledge and inquiry around the topic.  It turns out that this was one of the major factors in building the fantastic topsoils of the American Midwest.  Prairie fires, intentional and accidental, have been a conditioning and capacity-building influence for as long as humans have lived there.

Perhaps the most stunning example of the soil-creating powers of char comes from the Terra Preta soils of the South American tropics.  I am unclear on whether these are known to have been intentionally created, but the story goes that when researchers looked into the back story of some fabulously productive, seemingly inexhaustible soils in the Amazon (I think), they found that the soils were built from leftover char from cooking fires accumulated to something like a twenty foot depth over the millennia in these locations, and that time had allowed full charging of the char.  The result was jaw-dropping, and I find the implications staggering.  Give me some of that!  Never was the Permaculture maxim of misallocated or excess resources equaling pollution so clearly demonstrated.  Carbon is aresource, folks.  And if there is one thing modern western culture is good at, it is exploiting resources.  There is even the possibility in my mind that if we got good at putting carbon to excellent use in our soils, we might even end up with a more productive planet than we’ve ever seen in the history of humanity.  Stick with me a minute:  Two-thirds of the CO2 resource has come from carbon that’s been out of commission since the dinosaurs.  If we can get a hold of that, too, and add it to carbon-poor soils around the globe, we might be sitting pretty, even with 7 billion of us and rising, albeit with a nod to the law of unintended consequences.

blog-burn processSo how might we go about tapping into this resource?  On a large scale (municipal, industrial) it needs some kind of “through-process” system to be efficient, perhaps making use of agricultural and sylvicultural (tree-growing) wastes or by-products such as tree tops from sustainable wood products, orchard prunings, corn stalks, wheat straw and chaff, etc.  On a small decentralized scale, this is almost surely going to be done in batches (my first attempt is described in the last blog entry), with the exception of grassland management systems, which are more infinitely scalable.  Some of the most exciting developments I see are systems being built for home-scale use (many could be adapted for larger work) that are using the surplus heat from biochar kilns to provide domestic hot water, home heat, greenhouse heating, cooking heat, and the like.  There is potential for using the excess gases to run internal combustion engines, and one creative company has even managed to refine jet fuel and other hydrocarbons from them!  Of course, one worries about the consequences of Americans learning how to burn trees to make their SUVs run…


blog-small scaleMuch of my information about technical developments in biochar come from Wayne Teel, our local biochar tinkerer extraordinaire, and a JMU professor in sustainable agriculture specializing in agroforestry.  It can be done on almost any scale, and we need lots of common people playing with it to create a fertile environment for innovation and acceptance on a broad and/or large scale.  Before long the corporations may recognize what a valuable resource is in the air over our heads and all around us…then they’ll find a way to claim it for themselves and charge us for it!  Get it while you can!

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