course of years – even decades – holding them for use by plants
Biochar is used with nearly every growing thing at Green
Fire Farm: disked into reclaimed pastures, worked into the soil
of the vegetable gardens and berry patches and fruit orchards,
added to the dirt around tree seedlings, even incorporated into
the animals’ bedding pack to enhance the manure and extend its
usefulness once that bedding is used as fertilizer.
A modern day Jack-of-all-trades, Low works as a builder
during the warm months and logs during the colder ones. He
has cleared about 14 acres of land on the farm over the past eight
years, managing one to five acres each year. That translates to
5,000-15,000 board feet of spruce, fir, and pine annually and
2,000-4,000 board feet of fence post cedar. Low uses the wood
for building materials and his woodworking, as well as biochar
production. Much of the logging and biochar-related work is
animal-powered, though Low also uses tractors.
In the spring, while many of his neighbors are sugaring, Low
makes charcoal, transferring some 50 cords of wood into his
own version of black gold.
The magic happens in an Adam retort. A brick kiln designed
by a German engineer, Chris Adam, the Adam retort was
originally created for use in developing countries as a means
of making fuel charcoal from local biomass. Its small scale
and what Low calls “mid-tech” bearing are ideal for Vermont
Biochar, which remains a one-man operation.
Low’s kiln cost about $4,000, including materials and the cost
to hire a mason to help with construction; it allows the wood
to cook through pyrolysis, burning without oxygen. The brick
retort measures roughly four feet tall, five feet wide, and nine
Each batch of char uses a full wagon load of wood – one
cord of scrap wood, split pulp wood, and tree branches bundled
together – delivered by Will and Abe (Low’s oxen team) and
stacked neatly into the kiln to allow the best gas flow during
pyrolysis. Low places a steel frame sealed with wood ash over
the wood box and fires the kiln early in the morning. Gradually,
the moisture cooks out of the wood and is released through one
of two chimneys. A second chimney drafts the firebox under the
kiln. This first step of creating the biochar, cooking the moisture
from the wood, lasts until around mid-day, with Low feeding
the fire box regularly.
As the moisture is cooked out of the wood, volatile gases
are released, and Low shifts the kiln to the gasification phase.
He closes the first chimney, forcing the gases through the fire
chamber where they heat the kiln (to temperatures of more than
900 degrees) in a self-sustaining loop – and reduce the amount
of smoke released into the air. This phase lasts most of the
afternoon and is less labor-intensive, requiring only occasional
feeding of the fire box.
Not one to sit still for long, Low uses this relative downtime
to complete other tasks – carving wildly shaped planters from
cedar logs, spending time in his blacksmith shop, or splitting
wood. This year, in keeping with the farm’s animal-powered
practices, Low purchased a horse-powered treadmill wood-splitter. With this addition, Breeyore will help split the 65 cords
of wood – 50 for charcoal production and 15 for firewood
– used each year at Green Fire Farm.
Near supper time, when the gases have burned out, Low seals
the retort, leaving the charcoal to cool overnight. In the morning,
he shovels the char – bone dry and pure black to shimmering
silver – into metal trash cans, where it will cool completely
before being processed through a chipper-shredder.
Low inoculates his biochar in small batches and only when
he has orders to fill. Into a large wheelbarrow he pours a lab-made blend of microbes and mycorrihiza onto the char, which
soaks up the water-soluble inoculant. The biochar is then
packed into 2-gallon or 8-gallon bags which sell for $12 and $40
Low and Brent use 10-25 cubic yards of the material on their
own farm, and produce an additional 25-30 cubic yards for sale
both onsite and online. Their own testing with the product has
convinced them of its benefits.
“When we started, we could hardly graze two cows on the
land, and now we get three to four tons of hay per acre,” says
Low. “In five years of carbon farming and using biochar, we’ve
grown the land’s carrying capacity by 450 percent.”
Meghan McCarthy McPhaul lives in Franconia, New Hampshire, where she writes on a
variety of subjects and maintains a blog: Writings From A Full Life.
Wagner Forest Management, Ltd., is pleased to underwrite Northern Woodlands’ series on forest entrepreneurs. www.wagnerforest.com