Micronizing the Char

It sounds odd to say it, but the smaller the particles, the more habitable surface area the char will contain. The International Biochar Institute (IBI) has found that particle sizes less than 2 mm are best. These tiny bits are made up of many tubes which are the vitrified plant cells. Turns out, heating coals 'til they glow is like firing pottery. Not only does the material turn into something like glass, the particles lose half of their size as well. (The charring process shrinks parent material by half as the hydrogen and oxygen, tied up as carbohydrates, are driven off.)  When the carbon is heated to between 450 and 500 degrees F (230-260C) in the absence of air, it is transformed forever. See the entry: "Making". This small particle size also allows earthworms the ability to consume the char and have it come out the other end enriched with worm castings! 

 

This is what the structure of a particle of char looks like once turned to powder. This image is a scale model of what a 0.1mm (0.004 inches) piece of char would look like. This is still massive compared to most soil microbes. Many refer to char as being like condominiums for microbes. The moisture, nutrients and minerals we add to char are akin to stocking the refrigerators, mini bars and pantries of this massive complex for life.

Try as I might, some people just cannot comprehend this living zone under our feet. I understand that it will forever remain invisible, but we can understand what goes on there if we know how to look.

I have developed soils that were over 8% organics and when organics in soil get high, many weeds do not grow optimally, especially peculiar is quackgrass, which gets large underground systems that can't even put up a single leaf. It is almost like it is trying to grow toward poorer soil before it even tries to grow anything above ground. Remember though, 90% of the carbon added to the soil as compost is lost in one way or another, within four years.

Fully half of what we call soil is either air or water. Soil air, or soil atmosphere as some call it, has slightly less oxygen and nitrogen than above ground air and many times more carbon dioxide in it than air we breathe, again, a result of soil microbe metabolism. Atmospheric carbon dioxide is 0.04%. in soil it can be 0.25% In any case, depending on the water holding capacity of soil, saturation levels, and compaction, soils can range up to ten percent more air, or water, at intervals, it swings back and forth around 25% of each. Most of the remainder is mineral. Up to half of the material is just "dirt", a mineral complex waiting to become habitable. One might imagine parent rock as pure mineral without organic material added in yet. Often it is referred to as bedrock. Fertile soil, on the other hand has this once living carbon component that is residue of life. Soil tilth comes, in part, from this. Fungal hyphae exploit it and turn it into structural elements within the soil complex. The microbes who feed in, on and around these stored reserves flourish and give rise to other trophic levels.

Looking at just the tiniest section of the pie chart, the 5-8% which represents the organic carbon, dead plant roots, dead plant residue, dung, dead microbes and other life, etc. we see a community made up of billions of organisms per tablespoon. healthy soil is completely different than dirt. Just considering the tiny fraction of the soil we can control, component by component, further investigation reveals this:

Soil microbiome in healthy soil is diverse and contains all these interactive elements. So many epiphitic and filial relations exist between members of the soil community, it is difficult to diagram them all. Each trophic level can concentrate minerals, nutrients and, sadly toxins, to tenfold increase above background levels in their tissues. All parts of this system provide vital resources for other trophic levels. Unlike above ground life, every creature or plant can feed on the others, making them top predators.

I was challenged by a friend to create a diagram of the carbon cycle and this is just my first stab at it. Soil carbon as I have diagrammed here, is mostly living or recently living. The tiny bit of carbon biochar adds is less than a single percentage. The rest of the life that goes on, the biome, the active living tissue of billions of microscopic organisms per tablespoon of soil, once consumed or used as resources  for sustaining amoebae, ciliates and/or flagellates, however these same soil organisms can feed on the tissues of any of the representatives from any and all other trophic levels.

90% of organic carbon added to soil leaves within the first four years, so if you compost, never wait five years to add it to your garden beds or crop producing fields. Soil life depends on dead roots, dead leaves, manure and other organic matter, typically the sorts of things we throw into our compost bins, typically food that would smell bad within a few days. This is exactly the kind of stuff that soil microbes love. without a constant supply of nutrients, like us, they wither and die.

What makes biochar different is that vitrified carbon, pyrolized carbon, lasts forever. The organisms who use it for housing don't eat it or digest it, they just use the surfaces within it for habitat. That is, why making the surface area available, by making tiny particles, is worth the effort. Unleashing the power of char takes place when the material is crushed to powder. If you ever see a charred log in the woods, it is almost always virtually sterile. Nothing will grow on it. When the particles are tiny, it becomes possible to saturate it with nutrients and food for life. In a large chunk, there is comparatively little surface area exposed to air, water and nutrients.

My feedstock for making char is primarily sawdust. I live in a forest products state and have virtually unlimited amounts of it free. It is expensive to transport away. Making char from sawdust yields small bits that do not need to be crushed to powder or small grains. Perhaps you think it lazy, but really, it is efficient. If there are agricultural areas near sawdust anywhere on Earth, the highest use for them is char production! Get on this human beings, let's make this happen!
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When I heard that there is as much surface area in a chunk of char a third the size of a sugar cube to equal the area of a soccer pitch, my mind was completely and utterly blown. Looking at it another way, a handful of the stuff has fourteen acres of surface area. Again, mind-blowing. I'm nearly ten years in to my experience with biochar and my mind is still blown when I consider it! When you factor in the ability of microbes to flourish in and on the char, it has even more power to transform soils for the better. Water holding capacity is increased not only because char holds six times it's weight in water, but once colonized by the microbial community, that amount increases because the microbes hold water in their cells as well.

<2mm 2mm="" a="" again="" ahead="" am="" and="" becomes="" but="" can="" char="" charred="" clogs="" coffee="" could="" crushing="" difficult="" doing="" dust="" equipment.="" for="" full.="" get="" grinder="" hammer="" hand="" handling="" hard="" i="" if="" is="" it="" large="" material="" me="" mill="" moisten="" more="" of="" p="" particles="" pretty="" quantities="" quickly.="" requires="" respirator="" single="" sub="" terrible.="" than="" the="" thing="" to="" turns="" use="" work="" you="">
<2mm 2mm="" a="" again="" ahead="" am="" and="" becomes="" but="" can="" char="" charred="" clogs="" coffee="" could="" crushing="" difficult="" doing="" dust="" equipment.="" for="" full.="" get="" grinder="" hammer="" hand="" handling="" hard="" i="" if="" is="" it="" large="" material="" me="" mill="" moisten="" more="" of="" p="" particles="" pretty="" quantities="" quickly.="" requires="" respirator="" single="" sub="" terrible.="" than="" the="" thing="" to="" turns="" use="" work="" you="">When I began, I tried everything to crush the nuggets of char I made. In addition to being dusty as all get out, there were no good ways of doing it. I drove a large vehicle back and forth across a big burlap bag, lined with a plastic bag to catch as much of the char powder as possible, after about twenty times of driving over it, about a quart of use-able char was produced, the rest remained big pieces. I tried a hammer and made some small bits, but many bigger chunks went flying. I even tried a large mortar and pestle, which worked, but is not nearly as romantic as it appears in those movies they show in anthropology class. There is a reason that mills figure greatly into most local lore. Once you didn't have to pound or grind wheat to flour, by hand, things were golden! The tool of choice that I have settled on for smaller areas, garden beds and smaller, is to use a hand grinder for coffee. You can change the fineness of the grind and sub 2mm is easy enough to get with it. You just have to slowly feed chunks into the feed auger, which requires paying some attention to, but, if you are the person cranking the handle, you should not hurt yourself too badly. Please, please, please, do not breathe the dust!

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Finally, for larger acreages, you can utilize a hammer mill to crush char. Especially if you have acres to enrich, but only logs and large chunks of wood to char. It can be done, but do not breathe the dust! Always wear a respirator if you are going to be around char dust! Another caveat of the hammer mill that is if you try to use water to keep the dust down, the workings will get gummed up. Always remember, what seems tiny to us is cavernous to the microbes we are helping to thrive in the soils we are building.

Making Char

This first step in creating of biochar.
In essence, all you do is heat dry plant material to between 450 and 500 degrees F (230-260 C), basically making it glow, without allowing air to get to the reaction site. This process is called pyrolysis. When the material glows, it changes form and makes it like more like fired clay, than wood or dirt. when vitrified, ut becomes permanent in the environment and not subject to degradation. Charcoal has been made around the world, throughout human history. When human beings learned of the power of char, and how it is turned into biochar is still a mystery. It is well established that as recently as 2,000 years ago, humans were making it and some tribes and cultures still use this practice in modern times.

It is sad that intact cultures are referred to as primitive, because they are often far more scientifically advanced and sophisticated than that term implies. Utilizing biochar is one of the indicators of a highly advanced agriculture.  My tool of choice in the matter of making char is a retort, a basic scientific instrument designed to allow heating and vapor release, without introducing oxygen (air). Typically, the retort has but one opening to allow gasses to escape, mine actually has three, but they can be closed during cooling.  Here is a schematic view of a retort.

Below is picture of my old retort in use and I have made other types of charring equipment as well. It is important to understand all the ways to do this step, so you can pick the one that suits your needs, available resources and needs. In my classes I discuss at least five types of charring techniques, the pit or flame cap, build and bury, similar to how much char was made before the fossil energy revolution and the current infatuation with liquid fuels; retort, of course, because it is my preferred method, the can within a can (which pretty much explains itself) which could also be called a retort in a chimney, and the TULD, Top Lit Up Draft. The method you choose varieties depends on how much you are making, what materials you have available and how pure you want/need to make your char. In addition to teaching facts about biochar, making and using it, I try to get across a feeling, or attitude of appreciation and the desire to teach and share with others the ancient miracle that is biochar. Making char requires nothing more than a basic popcorn, cookie or cracker tin. Just pop a few holes in it to release the gasses and fasten the lid on with self-tapping pan head screws, then char away. You can even use dry garden clippings, woody yard waste or herb stems, any dry woody debris will do, as long as it is completely dry. Typically, I just put the whole container right in the fire pit while enjoying a camp or bonfire. At first, the container smokes a little, but then the flammable gasses come off, making pure clean flame. When that flame dies down, and disappears, even if you shake the container around, it is finished. Lay it on a surface that won't burn with the holes you poked facing toward the ground to smother off as much air as possible from getting into the container. When it cools, it is ready to start processing. Beware though, wood and sawdust, or organic material is a good insulator, so the coals may stay warm for several hours or more depending on how large a container you use.

This retort is made from a Cornelius keg, it holds five gallons of material (I prefer dry sawdust) and reduces to approximately one kilogram of material. Making char from sawdust eliminates the need for micronization, because the pieces are small enough to be used without further smashing into powder. A typical firing of a retort like this takes about three hours with dry sawdust used for the feedstock, or parent material. The value of this will become evident in later posts. (see Micronizing) As in nature, stacking functions is the key to increased efficiency.

I did not have a big enough fire pit to roast the material in this retort, a sealed 55 gallon drum, with conduit to direct the gasses out the bottom. Although it worked well enough to produce the flammable gas, it was just not enough to help warm the drum.  Had I been able to build a larger bonfire, it would have been able to make over ten kilograms of finished char. That would be enough to amend a ten foot wide bed forty feet long to a depth of three inches.

If you are not able to make a fire for some reason, you can use high end charcoal that is readily available at grilling outlets. Typically it has names like natural charcoal, cowboy charcoal or lump charcoal. Essentially it should appear like burned wood. If it has been compacted into uniform briquets, typically it will have contaminants and binders that reduce the quality of your finished product. In this case, I must admit that I am a bit of a carbon snob. The goal is to get the open grains of the wood's cellular structure, binders, paint, stain and other foreign material can close the ends of the pores and render the finished product either contaminated or useless. If you had a scanning electron microscope, tiny particles of the finished product would look like this:

It is really that simple. Dry organic, woody material, the cellular structure of the plant is what gets preserved at approximately half size. As the material is heated, the gasses liberated are nearly pure oxygen and hydrogen, these flammable gasses must be able to leave the retort and they will readily be burned off during the process. The nice thing about the retort is that when the gasses stop coming out, you know that the char is done roasting. After removing the retort from the fire, loosely plug or  cover the hole(s) to keep air out and let the char cool. Another way to tell if the char is done is to feel the weight of the container. When finished, the char is very light and when you touch finished char, there will be very little black carbon that sticks to your hands. Incompletely fired or poorly pyrolized char will still have oily soot-like residue. It gets your hands dirty when you handle it and it will smell or taste of creosote.

 A good way to tell if char is finished is to smell or taste it. There will be no taste or smell. The best char, is pure carbon. After it cools, if you stir the pieces, it will almost sound metallic or like broken glass shards, especially after it is moistened, but that will be covered in the next post. Poorly made char can degrade as it breaks down in soil, so take care and do whatever it takes to make the best char possible, it will reward future generations, many times over, not only for seven generations, but for geologic time.

There are other ways to make char and they include something called a flame cap burner, basically a container that does not allow air in either the bottom or sides. In this method, you have to build a rick. (a rick is like a log cabin, but the logs are layered from side to side like a nearly solid floor on each level, but to maximize air flow, room is left around each log, stick or branch, not like a solid floor of wood, but a lattice in three dimensions.)  A small fire is built atop the rick and when the material burns down, you will notice that the fire only exists at the top of the vessel, where air first contacts the hot gasses. Material inside will just glow, but not burn. Keep adding material until all that is left is the glowing bed of coals, when the flame cap stops burning, the gasses have all been released, the char is done and has to be quenched with water or have a loosely fitting lid ready to cover the vessel to keep air out. This method is great if you do not have strict burning regulations because it gets smoky if you put too much material on at once. The ideal rate for adding material to the flame cap burner is evidenced by the absence of smoke. You want a very clean burn, if you get any smoke, either you have put too much on at once, the inside of the container is not hot enough, or the material is too wet to char. This can even be accomplished by just digging a hole in the ground and building your fire large enough to fill the pit with glowing embers. Quench or smother them out with the soil that remains from digging the hole. It is "primitive", but if you know what to do and how to know it is done, it can work beautifully.

The TLUD (Top Lit Up Draft) burner and the vessel within vessel method are also useful if you have the materials and metal-working skills to make them. First, for the vessel within a vessel technique, you would need a small, sealing, steel container and it would need to fit within another larger steel container, I have seen them made from a 30 gallon drum inside a fifty five gallon drum. Holes are made in the bottom of the thirty gallon vessel 2-4 inches (5-10 cm) up from the bottom, to allow gasses to escape.  This container is then filled with the material you are going to char and sealed. The larger drum also has holes in the bottom and is kept up off the ground at the start to let fresh air in when lighting the fire, but since they are in the bottom, when the burn is complete, you can pretty much seal them closed by simple lowering the container to the ground. The larger drum also has a lid, but it needs to have a hole prepared to accept a stovepipe. About six feet of stovepipe above the  penetration in the lid, to keep all the smoke up and away from people. This device is very smoky upon starting as can be the TLUD  In any case, the large drum gets propped up off the ground to start the burn, the smaller vessel, once filled with material to be charred and the opening of the drum is sealed, it goes into the larger vessel, atop a bed of tinder and other fire starting material, vent holes down. The inner drum is propped up off the bottom as well. The space under the smaller vessel holds the kindling wood and helps air to flow upward during the main burn.

The next step is to be to fill the space around the inner drum with dry, burnable material An easy way to start the burn is to make ready some coals, like you would use for grilling, dump them down into the tinder and quickly fill the drum with the wood, quickly capping it and installing the stovepipe. As the outer wood burns, it begins to heat the inner drum and as that happens, flammable gasses begin to escape making the fire hotter. Eventually the smoke stops as the outer sleeve of wood goes to char, then ash, but by then the additional heat, from the escaping gasses leaving the inner vessel, continue to burn, also heating the inner vessel. This allows it to finish the process. As the material finishes, less and less gasses are produced until there is no more flame, just glowing coals within the inner vessel. At that point let the outer drum drop to the ground, sealing out the air. Some people like to throw a "seal" of sand around the edge, or do that and then moisten the sand to help keep out the air that could get in the bottom. I have not worried about it and done well, just getting a good solid seal on flat ground. To reduce the updraft of the chimney, which could draw air in the bottom, you could add a flue damper.

The TLUD kiln is similar to the flame cap, but the flame essentially working its way to the bottom, using up all the available oxygen before it can burn the char all the way to ash. I'm not completely thrilled with this technique because some creosote residue might be deposited on the finished char. I have not fired one myself and it requires one to not have to worry about making lots of smoke, again when you get it started, it will smoke to beat the ban, until the flame front gets established. In a TLUD kiln, it works like the flame cap, but the air coming in the bottom is severely limited, and the flame actually advances down from the top, as it goes toward the small amount of air, it uses up all the oxygen in the process of burning and the hot material left behind is hot enough to continue to give off gasses. In this sort of kiln, typically, they run a stack with an afterburner to burn off the gasses when they finally get out into the air. These can be impressive and may bring to mind a fire breathing dragon! To my understanding, having the material loosely packed in the kiln is crucial to success, you can't pack the material in the kiln because the air flow, although small, is crucial. When packing the TULD kiln, the feedstock needs to be about as dense as a natural sponge, so air flows around and through the material, rather than if it were packed tightly, or irregularly, it would choke off the air flow, burn unevenly or only partially char. I plan to make one of these and try it for myself. The people who use them swear by them.

You can put any vessel over fire, as long as you have somewhere the flammable gasses can escape. When the gasses stop coming off, if you stir the material and the flame does not continue, or flare up, pull it from the fire and put a loose fitting lid on it, seal it with the ground, or quench it out with water, because as it contracts, air will make it into the retort, but the goal is to not have it touch any glowing char that has not yet cooled below 400 F, otherwise it could continue to burn when oxygen gets in. I have had batches where the integrity of the seal was compromised and the char continued burning for over ten hours, without me even noticing. I went to sleep and in the morning, the container was still warm, opening it revealed the embers had consumed almost half the char! When making char in any sort of retort, it is important to wait until the material is fully cooled before exposing it to the air. If you do not, it can reignite on contact with air. The still warm char gets wasted when it turns to white ash. Keeping this white ash production to a minimum in all but the most acidic of soils and getting the highest percentage pure carbon as possible is the goal. It is critical to getting the most from your effort.

The most important thing to remember about white ash, is that it is very alkaline, lye is made from fully burned ashes. DO NOT USE white ash. It is no longer carbon, even that gets burnt. Once burned to white ash, only minerals remain. We want the carbon, that is what benefits the soil, when it becomes fully pyrolized. Wood that has not fully charred will decay and lose carbon as well, so make sure that you fully char the material you use. The embers must glow and completely, lose all their hydrogen and oxygen. Pure, vitrified carbon will remain fixed in soil for geologic time. Once prepared this charred material has fourteen acres of surface area per handful. All that surface area needs to be nourished to become a healthy precursor to soil. That is whay the next five posts will cover. Basic science rules those phases, but for now, keeping with the title of this post, making char is easy, if one has some simple tools, a fire and patience to make sure your woody material is fully finished before you remove it from the fire. I will cover more about the golden ratio of minerals and nutrients, in the post "Mineralization"

If you choose to make a retort, vessel in vessel, TULD burner, or use a flame cap  method, the only requirement is to have complete pyrolysis without either un-charred material or white ash. The best tests for quality are look and feel, smell and taste. It should be ultralight and the darkest black you will ever see. Occasionally it may have a rainbow oxidization, but the predominant feature is to be super black (the best char sounds a bit like glass when pieces are touched together. You will hear a hollowness to the pieces and they will be very light) Testing char quality by smell, (should smell fresh, not like creosote or smoke) Char is a great deodorizer. There should also be no taste; again, smoky or oily flavors are evident straight away. Material not thoroughly heated for long enough will smell like smoke. Excellent char will not taste like anything, in fact, the predominant sensation is that it sucks moisture from your tongue. Truly an anti-taste.

This material is so much more valuable than gold, I cannot begin to tell you. This beginning ingredient, char, when treated and processed properly will double crop production when added at the rate of one kilogram per cubic meter of soil, or roughly two pounds per cubic yard. If anyone ever needs help determining how much char they need, please contact me directly. My land line is nine twenty, double 8 four, triple two 4. Mornings in Wisconsin (Central Time) are the best time to reach me. Best wishes on your journey. When you use your char and see the benefits, think about who taught you how to make it and send a token of thanks. Think long and hard about the principles within sustainability, which  urge us to equitably distribute the abundance. That is all I ask. Ubuntu as they say in Africa, namaste' as they say in India. We are each incarnations of the godhead and without a single one of us, all would be diminished. I truly am, because of you! Appreciatively, Tony C. Saladino