‘Oven’ Turns Brush Into Soil Additive That Stores Carbon Over Long Term
Bob Wells, New England Biochar, March 23, 2010
Bob Wells cooked up a batch of biochar using his Mobile Adam Retort.
By ELISE R. HUGUS
Spring has undoubtedly inspired residents to clear the brush from their yards these days. But instead of burning those fallen tree limbs or taking them to the town compost dump, one Hatchville resident spent the weekend turning the detritus of winter into a substance that will help him grow vegetables, all while reducing his carbon footprint: biochar.
Starting at 9 AM on Saturday, Joseph L. Hackler, a researcher at the Woods Hole Research Center, and Robert Wells, of Eastham-based New England Biochar, started loading seasoned wood and collected brush into a biochar retort [oven] of Mr. Wells’s invention. By noon, the warmth of the sun was rivaled by the heat coming from the steel combustion retort, which the men kept at a steady temperature of 842 degrees Fahrenheit.
The plan was to slowly “pyrolyze” three cubic yards’ worth of woody biomass, which Mr. Hackler and his wife, Karen R. Schwalbe, will spread on the fields of their three-acre Tomten Farm. Similar to charcoal, but not intended for burning, biochar has been hailed as a miracle for its ability to enhance soil structure and water-holding capacity, as well as biological activity and nutrient availability. Composed of dead plant material, bones, or animal waste that would otherwise decompose, biochar is immobilized in the soil for at least 1,000 years, reducing the amount of carbon dioxide that would otherwise be released into the atmosphere.
“We’re short-circuiting nature by taking carbon that would otherwise be released into the atmosphere and putting it directly into the soil,” said Mr. Wells. “We’re doing the opposite of what the coal companies are doing.” Because the biomass is burned in a chamber with little or no oxygen, the material does not turn to ash. The methane, carbon monoxide, and hydrogen gas created in the batch process is diverted back into the burn chamber, where the gases add fuel to the fire. Eventually, an exothermic reaction takes place, Mr. Hackler said, at which point the fire sustains itself. Once the fire burns out, all that is left is biochar.
With the help of Peter Hirst of Wellfleet, Mr. Wells designed the Mobile Adam Retort to reduce 75 percent of the carbon dioxide emissions that would normally be created in such a process. Only small amounts of CO2 and water vapor are released from the smokestack, he said, much less than is typically produced by creating charcoal from wood.
“Making charcoal is a smoky, nasty business. It’s the main energy source in Third World countries, and people die at a young age from lung problems because of it,” said Mr. Wells. Biochar was first developed by natives in Brazil and used as a soil amendment for the past 2,000 years, according to the International Biochar Initiative website. The technology has been embraced as a way to help reduce the pollution and disease resulting from charcoal production in developing nations, and more recently, as a way to reduce greenhouse gas emissions.
Since biochar was adopted by agronomists in Japan and South America, its benefits as a natural agricultural additive have also spread around the world. Having designed a mobile retort, Mr. Wells demonstrates it around New England, and receives requests for information from as far away as India and Australia. “Now everyone wants me to show them how to do it. I could tour the world if I wanted to,” Mr. Wells said, noting that his mobile system could be shared by an entire community. “We’ve got a long way to go, but we’ve also come a long way.”
The energy created by Mr. Wells’s retort is enough to run a small engine or charge batteries. In addition, the heat created in the process could be recovered to heat a building, especially if it was used on an industrial scale, Mr. Wells said. As the moisture from the wood burns off, it passes through a condenser, turning into pyroligneous acid. “You can buy this for $4 a bottle at the store. It’s liquid smoke,” said Mr. Wells, opening a faucet on the condenser to release a stream of brown, smoke smelling liquid. He estimated that a typical biochar batch will create 30 gallons of the food additive.
Mr. Wells witnessed the benefits of biochar firsthand on his Redberry Lane Farm, where he said the sandy soils of Eastham impacted his ability to grow turnips, blueberries, and a variety of market vegetables. Now, in addition to greater crop productivity, Mr. Wells said he no longer has to pay for the “junk” wood left over from the trees he sells as firewood. And one of the most satisfying aspects of pyrolyzing plant material, he said, is getting rid of invasive species, such as multiflora rose, that plague his six-acre farm. Once he cooks up a batch of biochar, Mr. Wells said he runs over it with a tractor to reduce it to a fine dust. From there, he mixes it in an even ratio with compost, and sells the mixture by the 40-pound bag. It can also be added to compost “tea” for faster results, he said. Though it can take up to a year for biochar to innoculate in the soil, Mr. Wells said its effects are worth the wait. On a microscopic level, the biochar “opens a latticework of carbon, which provides spaces for microbes to live,” he said. These beneficial microbes help transport nutrients and water to plants. Just how much biochar increases the productivity of Cape Cod soil is the subject of a study that Mr. Hackler and an intern from Duke University will conduct this year, using Tomten Farm as an experimental field site.
The Falmouth Enterprise, Volume 119 Number 97 Tuesday, March 23, 2010
