When I began volunteering at Gibbs Road Community Farm, a teaching farm devoted to enriching the greater Kansas City area, I was sixteen years old. I sought out the small, organic urban farm because I had always enjoyed gardening with my mom, and I wanted to explore farming as a possible career. As I weeded, mulched, and seeded, the beauty of the farm and the incredibly hard work that was required to run it became clear. I got to know the people who performed most of this hard work at Gibbs Road, along with other urban farmers. I attended several workshops covering topics such as soil health and seed propagation, as well as several annual meetings of farmers and growers from the region. Before I tackled the SARE project I completed a Food Not Lawns class which detailed such practices as no-till organic gardening, integrated pest management, and alternative weed control. Since then I have felt a part of the growing urban agriculture movement in Kansas City.
When I decided to apply for a grant from SARE, I knew that the project would require many hours of research, writing, and thinking about a particular aspect of sustainable agriculture. My ideas ranged from mushroom cultivation to starting a school garden, but these just didn’t quite fit. I chose biochar because I was fascinated by the history of its origin, the science of its benefits, and its practical implications for urban farmers. From the beginning, my biggest goal was to make biochar. I wanted to design a pyrolysis unit that would easily and efficiently burn organic material until all that was left was a chunk of carbon. After researching biochar, it became obvious that there was a dearth of clear, simple instructions on how to build a kiln and make biochar, so it became another one of my goals to fill this gap.
From the beginning, the most time consuming step in my project was research. I spent hours reading instructions from many different sources about how to build a biochar kiln, and how to conduct a “burn”, the physics involved in pyrolysis, and descriptions of the various benefits biochar has on the environment and on soil.
The design I decided on was influenced by cost, size, efficiency, and ease of assembly. What it amounts to is a large 55 gallon barrel with a smaller 30 gallon barrel inside of it. The biomass (any carbon based, organic material) that you want to turn into biochar is placed inside the 30 gallon barrel and inverted into the 55 gallon barrel, then a lid and stovepipe are placed on the top. I obtained the lid and stovepipe from the farm I volunteer at, but I bought the barrels off of Craigslist. Here is the list of materials that I used to make my biochar kiln:
• 1 – 55 gallon steel barrel with lid
• 1 – 30 gallon steel barrel
• 1 1/4; diameter drill bit for cutting the barrels
• 1 steel stovepipe
• 1 drill
The design is called a double barrel retort kiln, and there are many different versions of it, but they all work on the same principle: biomass, sealed in an oxygen-free environment, is surrounded by burning material that bakes it into charcoal. The only change I made to the basic design, a decision I made after much trial and error, was drilling one-inch holes every three inches around the upper rim of the 55 gallon barrel. I was lucky to be able to reuse the lid of a similar retort kiln for my project, but if I hadn’t I would have had to cut a hole in the lid big enough for a tall stovepipe to fit over.
Once I had my barrels and the lid with the stovepipe on it, I was ready to burn. Finding biomass ended up being difficult: I had to find wood that was dry and small, generally not any thicker than three inches. I picked up some firewood somebody was giving away and ended up splitting it until it was the correct size. Then I packed it into the 30 gallon barrel as tightly as I could and flipped it over into the larger barrel. The inversion of the smaller barrel into the larger is a rather difficult process. I found it easiest to lay both barrels on the ground and slide the 30 gallon into the 55 gallon, then, while holding the 30 gallon with one hand, stand them up. Once that was complete, I surrounded the inner barrel with a mixture of medium to small pieces of wood and kindling, again trying to use as dry of material as possible, until the top of the inner barrel was covered. I then stuffed paper under some of the kindling at several places around the barrel and lit it with matches. I had to relight it several times before it really caught on fire. Once I could tell there was a good blaze going, I set the lid with the stovepipe on top and weighed it down with several bricks.
At this point, smoke poured out of the stovepipe for five or ten minutes, but once the fire got hot enough, the smoke turned clear and all that was emitted were gasses and pure heat. Depending on the dryness and the size of the outside wood, and how tightly it is packed around the inner barrel, the fire can vary in length from one to five hours. After there is no more heat coming out of the stovepipe, the fire is probably out, but you still want to let it sit, covered, overnight. This is because if you expose the hot char to oxygen in the air it would combust and burn away. At this point, everything was cooled down and the biochar was ready to be tilled into the ground or used as a layer in a no-till garden bed.
• Anne Bloos: Brainstormed, conducted burns, and researched with me.
• Daniel Dermitzel: Provided me with parts of a biochar kiln that he had made, and discussed the aspects of it that he thought would improve the design.
• Marty Craft: Consulted with me as to the best design for the kiln.
• Alicia Ellingsworth, farm manager at Gibbs Road Farm: Allowed me to conduct burns on her farm, informed me of SARE grants.
• I.B.I (The International Biochar Initiative): Consulted with me about what aspect of biochar would be of greatest use to study and research.
My first few burns were unsuccessful. I would excitedly pull the inner barrel out, only to find a mix of black and beige half-charred wood. Through more research, I determined that this failure was due to a combination of things. First, the wood in the inner barrel was too wet. I used wood chips from a recently felled tree in our front yard; I thought they would be perfect because of their size, but they turned out to be too fresh. Second, the wood surrounding the inner barrel had burned unevenly. I attribute this to wetness, poor air circulation, and having used very quick-burning materials in the outer barrel that didn’t burn long enough for the inner barrel to heat up. Third, at least for the first burn, I was using too large of an inner barrel. The larger inner barrel left less room surrounding it to place wood, which meant that the outer wood burned too quickly for it to cook the wood on the inside.
Through more experimenting, I fixed all of these problems: I found dry wood, I drilled air holes in the top of the outer barrel to facilitate, and I bought a new, smaller inner barrel. After correcting all of these problems, I finally had a successful burn. I pulled the inner barrel out, and chunks of pitch black biochar tumbled onto the ground. This took place in early June of 2012, at the start of the tortuous drought in the midwest.
Unfortunately, the severe heat and dryness caused my city to put into effect a no-burn order, preventing anyone from starting fires. I tried to burn again, but after fifteen minutes I noticed that the leaves on the tree far above the kiln were starting to tremble and blacken from the immense heat that shot from the stovepipe, so I knocked it over and sprayed it with water, narrowly avoiding disaster. I opted not to break the no-burn order again, thus putting my project on hold. Because I wasn’t able to conduct any burns that summer, I couldn’t make enough biochar to till into the soil and test its benefits, a major disappointment.
Even though I was not able to fully complete my project, I still feel like I learned a lot from the experience. I was able to construct a biochar kiln and create charcoal that, this coming summer, will be tilled into my mother’s garden and our community garden. The fact is, droughts are a common occurrence that farmers have to deal with. I learned that fact last year, along with many others about design, chemistry, and sustainable agriculture.
When I was researching biochar, and then also when I made and used the kiln, I was introduced to several aspects of sustainable agriculture. First of all, the history. Biochar was first discovered in the Amazon rainforest; pieces of tile mixed with charcoal were discovered in the soil dating back thousands of years. Biochar helped retain moisture and attract nutrients in the inhabitant’s soil, allowing them to grow crops and build sustainable communities in the forest. Secondly, baking the biomass into charcoal eliminates almost all of the nutrients except carbon. Because of the chemical structure of carbon, the char is formed into a highly-porous lattice, which, since the lattice causes there to be [creates] more surface area, is able to hold much more water than soil without char. Additionally, the biochar has a knack for attracting nutrients that are sometimes hard for roots to reach and making these nutrients available for consumption.
Above all of these benefits however, is the fact that when you burn biomass in an oxygen free environment you essentially “lock” the carbon in place. Normally, a felled log would eventually decay, sending large quantities of carbon dioxide into the air, degrading our atmosphere and leading to the warming of our planet. But when you burn a felled log, that carbon is solidified; so far none of it has escaped into the air, and scientists expect that it will be hundreds, if not thousands, of years before it gets out. This means that biochar is actually carbon negative, and some have even suggested that it be used as a carbon offset. One proposed benefit for example, is its use in developing countries. In many rural areas in Africa and South America, there is a scarcity of clean drinking water and electricity. It has been suggested that people in these rural communities could use small, inexpensive stoves that simultaneously make biochar and provide heat that could be used to boil water or cook food. This stove would have the added benefit of being carbon negative; instead of the normal open-fire heating methods that release CO2 and tar into the atmosphere, this stove would actually benefit the environment.
Biochar’s effect on soil quality could potentially help farmers increase their crop yield, and its effect on the environment could be another blow to global warming. I hope that my efforts to understand biochar and the process of making it will make a difference locally through informing farmers and gardeners of its benefits, by encouraging them to make their own kilns and use biochar in their gardens.
Over the last two years I have spent time explaining my SARE project and the benefits of biochar to other farmers, gardeners, and members of my community. I informally did this at farmers meetings and through discussions with people interested in sustainable agriculture. Since I didn’t have the chance to perform field tests I wasn’t able to publish the results. However, I still plan on sharing my experience making the biochar kiln and producing biochar through the Cultivate Kansas City newsletter. I have also communicated with I.B.I., who has offered to let me put pictures and a description of my project up on their website.
From the beginning of the project onward, SARE has allowed me to delve into a fascinating aspect of sustainable agriculture. The money that they granted me was instrumental in helping me achieve success in my project, and every interaction with them was pleasant and helpful. I can honestly say I have no complaints or suggestions.