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student, alumnus build a biochar stove

Antioch's biochar stove

Katie Wiebke ’15 standing beside Antioch College’s first biochar stove, which she and alumnus Peter King ’86 built during Reuion 2012. Photo by Dennie Eagleson ’71

So, what is a biochar stove?

Alumnus Peter King ’86 collaborated with student Katie Wiebke ’15 to construct the College’s first biochar stove during Reunion 2012. This special stove was made using old steel barrels to create a double-cylinder design that produces a special kind of charcoal in an oxygen-free environment.

Not only is the stove efficient, producing an immense amount of heat with a small amount of fuel (wood and other dry biomass), but it also produces biochar that will be mixed into the compost to improve the soil on the Antioch Farm.

So, what is a biochar stove? A biochar stove is made to function similarly to any wood-burning stove and can be used for cooking and/or heating. What distinguishes it, however, is the end product: biochar.

In a traditional wood-burning stove, ashes remain after combustion. In a biochar stove, fuel is not combusted but pyrolyzed. Pyrolysis is a chemical breakdown that occurs as a result of heat in an oxygen-free environment. When organic matter, or biomass, undergoes pyrolysis, charcoal is produced. Biochar is a specific type of charcoal, made with the intention of being applied as a soil amendment.

Studies show that plant growth can nearly double when biochar is added to soil. This is because the structure of the char is extremely porous, with a high surface area to volume ratio. Just one gram of biochar can have hundreds of square feet of surface area. These conditions create an inviting habitat for beneficial bacteria, fungi, and other soil microbes. In other words, biochar molecules are like skyscraping condos for soil biota. And because the char is such a stable form of carbon (the result of pyrolyzing organic matter), it will remain in the soil for at least 1,000 years and some estimates record biochar as staying in soil for up to 4,000 years. “This allows microbes to move in and out freely without having to pay rent or worry about losing their home,” Wiebke said.

The other exciting half to that long-term presence in the soil is that by spreading biochar over fields, carbon can effectively be sequestered. Currently most of the Earth’s carbon is getting absorbed by the oceans, making the waters more acidic and thereby threatening the entire marine ecosystem. Moving carbon from the atmosphere to soil not only keeps it out of the oceans, but also put it back into previously agriculturally devastated lands, ultimately restoring soil fertility and improving food production.

As if this weren´t enough, biochar stoves become even more incredible in their designs. Limited only by imagination, there are numerous options, and most are feasible do-it-yourself models. Hence, biochar stoves are very inexpensive, and with a little dumpster diving, can even be free. Furthermore, with a little bit of simple engineering, a biochar stove can become extremely fuel efficient and surprisingly clean. In fact, a properly constructed stove will not produce smoke, only water vapor. This is due to a phenomenon where pyrolysis off-gases are fed back into the fire as a secondary fuel that keeps the flame and subsequent heat going all the way until the biomass is completely broken down.

Antioch is still in the pioneering stages of this project. Biochar itself is just burgeoning as an alternative renewable energy source. There is still a lot to be discovered and improved upon.

To volunteer or get involved in this project, contact Katie Wiebke with inquiries: .


Nicole Wroten is the assistant director of communications at Antioch College. Katie Wiebke ’15 is a current student.