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Biochar Workshop Notes

Published on Monday, November 24, 2014

Biochar Workshop Notes

from Sunday 11/23 at Polly Judd House, Spokane, WA

Biochar is a term of art. It simply means biomass charcoal ready to play well with plants and soil. It is a "brand", like the term "agrichar" that preceded it, but that became unavailable when some Aussies trademarked it. Any bets on how long before the term "biochar" gets similarly sidelined? Still, biochar is a valuable term, we will use it with impunity for as long as we can.

History (english language records) shows: charcoal, wood charcoal particularly, was used to great effect in horticulture, agriculture, and animal feed in the 1700s and 1800s. However, because of charcoal's value in forging "charcoal iron", alternative use for charcoal was low profile. However wide availability of charcoal persisted long enough to give us some insights on where to look for garden performance: lower disease resistance, earlier growth, more flavor, and brighter color bloom. ... to look for waste management performance: added to feed makes for sweeter smelling poop, used in dry closets (vs the water closet of Thomas Crapper fame) to control odor and make fertilizer (look up term "poudrette"), to eliminate putrefaction when composting carcasses. ... water purification, feed supplements, bedding lightning rods. There is also record of capturing and using the distillates produced by pyrolysis, especially the acetic acids (wood vinegar), valuable in a gardening context for controlling plant diseases.

Terra Preta (Amazon) speaks to the greatest ever human achievement in terraforming, apparently taking many generations of combining char with waste to transform soil vitality, empowering them to thrive in a land we would otherwise consider hostile to supporting a large population.  We similarly need to develop this sustainable terraforming skill-set. It gives us hope that a regenerative tool so capable, yet so approachable, can be harnessed by our species. Proven successful, proven to be wildly adaptable, the thoughtful production and use of charcoal deserves to be a major tool in the permaculturist's toolbox, and a critical tool for anyone engaged in whole food system management.

Charcoal makes up 5-30% of organic carbon in most soils. It makes up 40-50% in mollisols (aka chernozems) due to indigenous burning. Char in soil is not a product of humifaction therefore not "officially" humus (Humates (soluble) + Humin (insoluble)). Soil science is missing the terminology to account for this major component of the organic soil fraction. This is because even now my profession is largely ignoring the role of charcoal in soils. That role is apparently very complex. We have a basic understanding of how biochar works in soil. (see But we don't have very meaningful terminology for managing char in soil. We don't have an extensive record of repeatable results and validated hypotheses needed give terminology meaning.

We built a fire in a cone kiln (see We want a hot, smokeless fire, one that discharges only carbon dioxide and water vapor, and minimized discharge of fine particulates. Flame on top assures all the smoke is pulled into the flame and consumed. Furthermore, you want to burn all the smoke, because you need every BTU you can squeeze out of the process to heat distill your fuel in order to isolate the char carbon. and do it quickly and efficiently without avoidably high ash content. Use dry fuel, avoid windy conditions. We covered some fire building approaches to minimize the wind effects we were observing. It was cold, the heat of the fire was appreciated.

We discussed incandescent color to char temperature to carbon structure. Example Orange = 930 deg C = 100% turbostratic structure. As a charisto/charista, you can anticipate the carbon structure (amorphous:tubostratic:graphite) by observing the heat. These structures vary tremendously in their effect on biochar function and soil performance. 

Amorphous (300 - 700 deg C) has high aBsorption of water due to flexible 3-D structure in pore walls. Amorphous carbon has the highest labile carbon fraction. Composting can dramatically increase this char's cation-exchange-capacity (CEC) a common index of nutrient holding capacity. Within the 300 - 700 deg C range, 450 - 550 is considered a sweet range for "best biochar". Below 450 incomplete pyrolysis is a concern, unpyrolized torrefied biomass can be present, as well as heat distillates, which will impart a smokey smell. 

If your char has smelly volatiles, it complicates the picture but it is not defacto bad. The wood smoke smelling subset of biochar is not ready to mix with the active garden soil without curing (time out after kilning), activation (typically means biological inoculation, also means chemical alterations, like carboxylation, that improve CEC, adsorption, and support the formation of functional groups critical to biochemical processes), and charging (nutrients, humates). Composting, overwintering on a soil surface under mulch are handy ways to accomplish curing, activation, and charging.

Between 550 and 700 deg C is composite char - both amorphous and turbostratic structure are present.

Turbostratic (550 - 1400 deg C)  2D structure (graphene sheets). It conducts electricity, important to anoxic respiration. Highest aDsorption of nutrients/biology. Porosity peaks between 700 and 800 deg C. This is the other "best biochar" sweet spot. The "electrical carbon sponge" term captures the character of this material. 700 to 800 deg C is above the temperature range covered well by academic research which has generally excluded the chars available from higher temperature processes like gasification and carefully managed combustion. Container mix growers, field flower growers, formulaters of inoculated mixes, ecological restoration, and environmental remediation folks report good performance from gasification and combustion derived chars. Avista's 50MWe power plant in Kettle Falls could be retrofited to produce an abundance of economical, high quality biochar.

Flexible turbostratic structure complements macropore based absorption. Steam quenching of hot turbostratic carbon further boosts porosity. Disordered/imperfect graphene sheet structure means some portion of the turbostratic structure is labile carbon, susceptible to be broken down by soil microbes (humifacton) but this labile portion is lower than in amorphous carbon.

Amorphous and turbostratic biochar can be powdered (ball milled - use ceramic balls to avoid sparking) to produce a size compatible with spray application. Fine size percolates, penetrates deep in soil. Because ball milling destroys pore structure, fine char has low absorption capacity. On the plus side, ball milling increases surface area and adsorptive capacity. 

Graphite (1000 to 4000 deg C) 3-D structure of tightly layered graphene sheets. Semiconductor - electricity conducted on surface. Original biomass porosity largely destroyed, low porosity, Poor Absorption. Lower surface area. No labile carbon. Still very interesting in a soil context.

There is no best biochar - soil likely benefits more from a diversity of structures (amorphous, turbostratic, graphitic) than from only a single "best" structure.

Very fresh char is very hungry char. In the first hours char can attract so much oxygen that the heat of reaction can cause char to reignite spontaneously. Oxygen isn't the only constituent fresh char is hungry for. Ammonia is the other classic char attracted gas.

Very fresh ash is also very hungry, initially for oxygen, but then the oxides are hungry for carbon dioxide. Pulling carbon dioxide out of the air acidifies the ash, drifting it from pH 10-12 down to 8.3 as oxides and hydroxyls are converted to carbonates. For soil and animal feed, time to cure is your friend here. 

Similarly ash is not defacto bad, but it adds another layer of complication to your problem solving, opportunity discerning, decision making process.

Our cone kiln looked like it produced a lot of white ash on the charcoal surface. But taking a shovel to it revealed the blackness of the interiors of the stick wood, assured us that it was much more char than ash.

One handy way to remove the ash is to sink the ash in an agitated water bath, skim the floating biochar off. Rick asked what we could use the resulting ash+water for. I didn't have an answer at the time.  Combining ash water with wood vinegarcould maybe be used to produce calcium acetate and potassium acetate, as mineral and energy rich animal feed supplement. Also, I wonder how Art Donnely (SeaChar) makes his biochar soap (Indigogo reward) The char serves as an abrassive, the causticity of the ash water could lend itself to thie soap making process.

We talked about stacking functions, the need to figure out ways to use the process heat. Appreciated the warmth,it was a cold day at times. A hot tub heater came to mind.  We could have been baking potatos (it was lunchtime).

Any plant feedstock can be used to make good char. Permaculture suggests bioregionalism in feedstock will be more tuned to local ecology (bamboo and coconut shell char not as attractive to us in Spokane in this context), more likely to perform well. We didn't discuss bone char, or manure char, maybe next time.

The biochar brand excludes contaminated feedstocks. The intent in using the biochar brand is to communicate that there is no bad biochar, only too much of a particular biochar for a particular soil/plant/climate/... situation. Too much can be disruptive. Don't juke the soil system too violently or soil will "Tilt", take a time out. Too much of a given char for a low vitality soil might be just fine for a resilient, vital soil. 

And there actually is no such thing as "too much" biochar, only adding biochar too fast for biology to adapt. Small regular increments over long time periods can be used to produce soils with very high black carbon levels such as we see in our native mollisols.

I brought out the Toro Ultra vac-shredder (comes with a metal impeller) and used it to grind the biochar we made. That chart got super doused and and it was too wet to get much lift odd into the Toro. Other than that it was very promising. Judy mentioned we can get kits to replace the plastic impellers in many leaf blower/vac/shedders with metal impellers. I know this is true of some of the Stihl units.

Adding 5-10% char by volume (1/4 - 1/2 inch combined with 5 inches of soil) is a standard starting place on personal garden plots. I use 50% char in my soil blocks for starting annuals. I cure, but I seldom activate/charge the biochar alone, however I often make an effort to assure that the biochar is coming into a rich/vital soil mix.

Recall that the ability to conduct electricity (turbostratic, graphitic structures) is important to anoxic respiration. Inoculating with facultative anaerobes complements electrical conductivity, bolsters what can be a weak link in the microbial community. We used the EM1 Bokashi inoculated biochar from regenerative-earth.comto bring this out in discussion. EM stands for effective microorganisms, they are a carefully selected culture of facultative anaerobes, probiotics for the soil and more. Several asked where to purchase the EM1. sells the bokashi inoculated biochar I brought for show an tell, and you can order the same through them. Its a great product. prepares a variety of bokashi products, with different formulations to cover a variety of applications. sells the EM1 and other bokashi cultures if you want to go the DIY route. 

Also be aware that there is a growing interest in culturing indigenous facultative anaerobes, part of an effort to culture IMOs or indigenous microorganisms. IMOs can be used in concert with EMs, If folks are interested I can dig up more info on IMOs

After the biochar focus, Mariah brought out her worm bin design eveloped over the past several years, showed her worm herding secrets. Then we all leaf-mulched a large area in support of the community garden and food forest. We had great fun doing this!
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