I never intended to get tangled in biochar burner technology. My interest has always been soil—how biochar enlivens soil to support the shift from chemical to biological agriculture. But teaching a new technology requires a "live fire" demonstration, so my 10,000 words come to a practical, visual, tangible, experiential focus in the mindmap of listeners' brains. This is, after all, a very new idea. And a very big one.
I needed a teaching tool to illustrate my verbal descriptions. I also needed a large source of biochar for my own gardens to investigate how biochar affects soil, minerals, microbes, worms, insects, and plants.
And nearly all pyrolysis technology was designed as industrial mega-plants that need a team of engineers to plan, and at least one licensed engineer to operate.
I saw no person or institution designing equipment and systems scaled to farms, households and communities—especially the complex quilted styles of Northeast small farms and rural communities—seedbed of social revolutions.
So, since we can't shop for off-the-shelf biochar burners, or browse catalogs of carbon-negative equipment, necessity forced me to walk my talk down the DIY path = Do It Yourself.
My first adventure with a nested 2-barrel retort was October 2007 with Doug Clayton at Pony Farm's first Biochar Roundtable in Temple, NH. We wanted a real-time demo to "show-n-tell" how pyrolysis and char-making look. We wanted folks to feel the flames, smell the smoke, blacken a hand in char, and—most critical—sequester some in soil.
So, Doug scavenged two barrels from the Jaffrey NH Recycling Center, and assembled a Folke Gunther bucket-inverted-in-a-barrel, scaled up to a 25-gallon nested in a 55-gallon. Doug didn't seal the inner bucket to create a pressurized pyrolytic retort and associated plumbing. No lid and chimney. Utter simplicity: two containers, bottom-to-top.
It worked! Doug's ingenious equipment made a batch of beautiful biochar for Pony Farm's garden.
In 2008, Doug and I performed our carbon-negative show-n-tell about biochar at locations and events scattered across New England. A few hundred people learned about carbon-negative climate and soil strategy that year.
In 2009, I needed to stay close to home, and focus on teaching carbon-negative in NY. I scheduled workshops in June for USDA NRCS directors and council members, July at Greene County Agroforestry Center, August at Landis Aroretum, and September to Master Gardeners at Albany County Cooperative Extension. I taught two workshops at my East Greenbush home, plus two at Saratoga Apple in Schuylerville.
So, I bought four barrels for $30 each from Capital Container in the Port of Albany, and made my own 2-barrel retort. My first homemade burner included lid and chimney for better draft and fire control. With my broken back, paralyzed right hand and 3-fingered left, I was proud of my nice-looking unit fabricated from red & blue barrels—without further damage to my body.
My portable teaching tool worked well—most times. I had failures from moist fuel, moist feedstock, wind, improper loading. I began to discover limits for this particular equipment—especially at Saratoga Apple trying to char chunks of dense, twisty applewood.
Then, unexpectedly, a sharp bend appeared in the path. July 2009, Jim Welch from Troy, NY built a hybrid biochar burner on a concrete pad in my backyard. His design emerged from my suggestion to put a rocket stove under a 2-barrel nested retort. Essentially, separate the burner from the biochar retort.
Thus, fuelwood isn't packed in a narrow space between two barrels. Instead, both fuel and fire—and all air and burner controls—are under the barrels in a separate, permanent, stable structure—the rocket stove firebox. A rocket stove can deliver a fast, hot fire that rapidly heats the retort to quickly, efficiently, reliably initiate gasification. Retort barrels can be easily, cleanly flipped on and off this fixed burner base to simplify operation and boost labor efficiency.
The result of Jim's creative craftsmanship exceeded our expectations, and impressed us how much energy can be extracted from 30 gallons of biomass. While the experiment had a few problems, it taught us to scale and control this novel hybrid approach to pyrolysis.
So, for a first-effort to apply a new idea, our experience was quite promising. But considerable ingenuity will be needed to harness this outburst of gas, flame and heat.
Over winter, we separately mulled over Jim's first design effort, and developed ideas to upgrade Jim's creative contraption of spare parts and scrap pieces. We need better control over the pyrolysis process, and a bigger rocket stove firebox. We must devise a method to control the rate of gasification, so we can slow it down and stretch the time out. And we must make use of the heat released. It won't be simple or easy to tame this fire dragon.
Jim scaled down to a 5-gallon retort, and designed a small unit for his own backyard. Jim's unit is portable, so we took it to Saratoga Apple and the Permaculture Convergence for some enchanting demonstrations at biochar workshops.
I decided to stay with a 55/30-gallon nested retort to produce large volumes of char for field use—and maybe a unit large enough to heat a greenhouse. This meant scaling up Jim's rocket stove to a bigger firebox able to crank out more heat for a hot, fast, furious fire to kick off the pyrolysis phase quickly, reliably.
This latest unit is still little more than an experiment, a learning toy and teaching tool. If this year's creative contraption actually works, and shows promise as a design path, we will test and tinker with this hybrid through the fall to learn to predict and control the pyrolysis dragon. Nate Darrow has 200 crates of applewood to turn into char, but this dense wood is a challenge to crush to small grains for soil application.
The ambitious goal for 2010 is to build a unit safe and reliable enough to put in Nate's 90x30 nutrient-dense greenhouses a few feet away. A 30-gallon retort heating a greenhouse through the winter growing season will yield a few hundred pounds of biochar by spring to spread on Saratoga Apple's 200 acres of fields and orchards. Their dense clay soils are desperate for any carbon, but especially for biochar. Over a decade of operation, the carbon sequestered in those heavy soils will reach optimums.
A full-function greenhouse heater means building a few upgrades and designing and testing add-on equipment, such as refractory insulation, masonry enclosure, heat exchangers, hot water reservoir, sensors, pumps, valves.....
So far, all we have is six 20-foot test plots with a thin coating of store-bought charcoal crudely crunched under a truck tire.