ISU researchers use biochar to improve soil

By James Pusey
Staff Writer
Published: Thursday, June 24, 2010 10:13 AM CDT
Agricultural researchers at Iowa State University are developing a way to make Iowa farms more profitable while reducing their impact on the planet.

The key is a product called “biochar,” said David Laird, soil scientist with the U.S. Department of Agriculture National Laboratory of Agriculture and Environment, and though it may sound complex, the technology is far from new.

The idea first came about, Laird said, when archaeologists discovered that an ancient Amazonian civilization had developed a way to turn the leached, unproductive soil of the jungle into soil useful for agriculture.

“These people would cut down the forest and they would char the soil,” Laird said. “They were able to create terra preta soils, which are dramatically different from the adjacent soils, which are highly weathered, low-productivity soils.”

“Terra preta” means “black earth” in Portuguese, and the soil was named thus because of its high charcoal content.

Laird said he and others at ISU are researching how farmers can benefit from the use of charcoal in agriculture.

Biochar is another term for charcoal, Laird said, but the different term is used because of biochar’s intended use. Charcoal is for grilling meat, for instance, while biochar is used for growing plants.

The biochar comes from cellulosic biomass found on the farm, such as corn stover, and is ground up and mixed with the soil to add carbon and nutrients, Laird sad.

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Robert Brown, distinguished professor of mechanical engineering and director of ISU’s Bioeconomy Institute, said he has witnessed the benefits of biochar in his own garden.

“My wife insisted that I try it, and our square-foot garden was the perfect place to conduct the experiment,” Brown said.

He planted different plant species in adjacent plots, applying varying amounts of biochar to each plot. He said he was astonished by some of his results, noting that spinach with biochar yielded around 15 percent more and baby bok choy with biochar produced 300 percent more.

“That was a lot of baby bok choy,” Brown said, pointing to a picture of his wife with her arms full of the massive plants.

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Laird expects that the most effective use of biochar will be to increase yields on low-grade soil. Research has shown that biochar has very little effect on yields in higher quality soils, but a recent trip to the ISU research farm showed how it can affect soil of lower quality.

Laird pointed to one sad-looking plot, just visible on the south side of U.S. Highway 30 between Ames and Boone. The field is more brown than green, with pools of standing water on its surface.

“This is really the worst soil we’ve got around here,” Laird said.

Even so, there is some corn growing on the plot, and three distinct rows stand taller and greener than the rest.

“That middle three rows stand out,” he said. “Those were the rows that we put about 30 to 40 tons of char on.”

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Biochar is produced at ISU’s Biocentury Research Farm, Brown said, where a process called “fast pyrolysis” burns biomass and converts it into three products: biochar, bio oil and natural gas. This use for cellulosic biomass materials is good news for Iowa farmers’ profitability, Brown said, as well as the planet.

Biochar has a much longer half-life than most carbon materials found in the soil, Laird said, at about 1,000 years compared to six months. That means less carbon is being released into the atmosphere.

“The carbon that’s in the char that you put down is going to be stable for a long period of time,” Laird said. “This is a huge carbon credit and it is one that we can easily measure.”

Though initial results have been promising, Laird said, there are still a lot of challenges to overcome before biochar becomes marketable in the mainstream. This will be one of the topics of discussion at the second-annual

James Pusey can be reached at (515) 663-6922