Date: April 14, 2014 by
Charlie O’Brien
No other soil amendment offers as many positive
environmental impacts as biochar. From
adding nutrients, to improving water-holding capacity to reducing greenhouse
gases, it is truly a jack-of-all-trades.
Biochar, is a carbon-rich material that is produced by
heating biomass at very high temperatures in an oxygen free environment. In the
production of bio-oil, plant biomass is put through a pyrolyzer, where it is
rapidly heated then cooled, transforming it into a renewable liquid fuel and
biochar. When biochar is mixed with soil it becomes part of the soil humus, thus
improving the quality of the soil.Increasing the water holding capacity of the soil is a key
property of biochar.
“Biochar increases the soil’s surface area and thus
increases the soil’s ability to hold water. The water is held in the char
particles’ internal pores,” said David Laird, CenUSA Bioenergy collaborator and
professor of agronomy at Iowa State University. “With the extra water storage
from biochar, these water reservoirs can help a crop survive a dry period.”
According to Laird, biochar is especially useful for degraded
and eroded land which has reduced ability to hold water and plant nutrients.
Biochar acts as a sponge, holding more water while allowing less water and
nutrients to flush through the soil and into the ground water or nearest creek.
It has also been used to help reclaim degraded areas like
mine land and urban industrial sites; adding biochar to these soils can help
them to start growing vegetation again.
Besides having the ability to act as a soil enhancer and reduce
nutrient and water loss from agricultural land, biochar also plays a role in helping
to mitigate climate change. The half-life of biochar placed on land is in the hundreds
to thousands of years, this long-term stability effectively sequesters carbon
in the soil making any biofuel produced in the process carbon negative.
“When I say carbon negative, I mean that the
pyrolysis-biofuel-biochar system takes more carbon out of the atmosphere than
it puts into it,” Laird said. “In net, you have taken carbon out of the
atmosphere.”
Laird compared leaves to biochar for long-term stability. In a very short time, leaves (or any biomass) added to the soil, will decompose and the plant carbon will return to the atmosphere as carbon dioxide. But when you take the same leaves and transform them into biochar first, carbon is very stable and does not dissipate quickly.
CenUSA Bioenergy and David Laird are working on several projects
pertaining to biochar. In addition to examining how it affects agricultural
production, soil quality and greenhouse gas emissions, they are studying its
chemistry and exploring new ways to use biochar.
Currently biochar is sold worldwide by about 150 companies,
mostly small garden and specialty retailers. Most of the biochar sold is used
for plant potting, green roofs, land remediation and filtration of runoff.
“Right now the price of biochar is very high and too
expensive for farmers to use extensively,” Laird said. “In the future we expect
companies to expand their production of biochar which will bring the price
down; then we will see farmers adopting it for farmland usage.”
