Is Biochar a Quick Fix for Global Warming?

Biochar

Photo: Robert Flanagan

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Combine an ancient farming practice with modern ingenuity and you've got what many believe could be an answer to our environmental woes. According to researchers, there's evidence that adding so-called "biochar" to soil could benefit agriculture and remove carbon from the atmosphere in the process.

With the foundation of the International Biochar Initiative three years ago, a growing community of researchers has been hard at work trying to understand and implement what has been called one of the most powerful potential solutions to climate change by leading climate scientists such as James Lovelock and James Hansen.

What is Biochar?

Hundreds of years ago, indigenous people of the Amazon River basin added a mixture of charred organic materials, such as crop residue, bones and manure, to their soil, creating vast and fertile farmland that is still some of the richest soil on Earth today.

Studies of this soil, called Terra Preta, meaning "dark earth" in Portuguese, date back to the 1950s, but more recently, excitement has grown over the charred additive that makes it so fertile -- a fine-grained, carbon-rich charcoal.

Biochar, also called agrichar or simply black carbon, is a highly porous charcoal that helps the soil hold nutrients and moisture, creating dynamic soil activity.

"The idea is that by putting char in the soil you can increase the fertility of that soil," said Brian Bibens, a research engineer with the University of Georgia's Biorefinery and Carbon Cycling Program.

As evidenced by Terra Preta, biochar can stay in the soil for hundreds, maybe thousands, of years, sequestering carbon, increasing crop yields and possibly improving water quality. According to the International Biochar Initiative, because it is so stable, adding biochar to soil increases retention of nutrients so that less fertilizer is needed and therefore less is released as pollution.

Terra Preta was most likely made by burning organic material and covering it with dirt, which reduced the oxygen supply. Scientists today use pyrolysis or gasification, which is essentially cooking biomass or biowaste at extremely high temperatures in high-tech ovens with little or no oxygen.

Alex Green, founder of Green Liquid and Gas Technologies in Gainesville, Fla., has patented a device called the Green Pyrolyzer Gasifier (GPG), which takes waste -- anything from regular garbage to sewage sludge -- and converts it to energy.

Green, who studied environmental problems for more than 40 years as a graduate research professor at the University of Florida, has recently become interested in biochar, a by-product of biowaste-to-energy pyrolysis, and is collaborating with leading soil scientists.

Going Carbon Negative

When biowaste is cooked in a device like Green's GPG, the result is a 30% yield of biochar and a 50 to 70% yield of vapors that can be condensed into "bio-oil" and used as fuel. The remaining product is a mixture of carbon dioxide and trace gases, such as methane, that is exhausted.

"They're released into the atmosphere," explained Bibens, "but at such low quantities that when you look at the big picture and how much carbon you're sequestering, it's a net gain of carbon being pulled out of the atmosphere."

Green said the most exciting thing about pyrolysis and biochar is the potential to go not just carbon neutral but carbon negative.

The idea is that farmers could eventually use a GPG or similar device to convert waste to electricity and biochar. With pyrolysis or gasification, the decay of biowaste that re-releases carbon into the atmosphere is bypassed, and biochar in the soil creates a carbon sink. At the same time, as crops are growing even more carbon is being pulled out of the atmosphere.

"It sounds like one of those silver bullet technologies." said Bibens, "but the devil's in the details."

Will This Really Work?

Biochar is not a substitute for dramatically reducing carbon emissions, and there are things in the way of widespread implementation, explained Johannes Lehmann, the International Biochar Initiative's chairman of the board, before the House Select Committee on Energy Independence and Global Warming this June.

Lehmann explained that it is difficult for the process to be profitable and responsible. For example, if a company is transporting large amounts of biomass to a plant to manufacture biochar, then the carbon sequestered by adding it to the soil is negated by the energy expended to create it.

Lehmann also said too few pyrolysis units are available "at sufficient maturity to allow all necessary research and development."

There is a strong consensus that biochar has positive effects and could conceptually reverse some of the causes of climate change, but results have not been quantified in the field yet, Bibens said.

Currently, Green Liquid & Gas Technologies is preparing the patented GPG for market as well as developing a mobile prototype that collaborating University of Florida soil scientists may use in their research and demonstration efforts. Green said that inexpensive ways of making biochar in the large quantities needed in agriculture have not yet been figured out.

"As a soil additive it must eventually be somewhat dirt cheap to an extent that depends upon many economic factors not yet established -- carbon taxes, cost of fuels, optimum production process, etcetera," Green said.

And according to Lehmann's testimony, it has to come from up top. He advocated national and international policies, such as recognizing carbon storage in soil with biochar in carbon trading schemes, to encourage implementation.

What it boils down to is that biochar is a promising technology, but it's not ready yet, at least not for industrial scale use.

Eventually, Green hopes the GPG will be a solution for on-site elimination of waste, so farmers can avoid transportation costs, reduce their energy bill and the nation's dependence on fossil fuels, and use biochar in their soil.

Despite hurdles, Bibens said research is developing quickly, and in time, he thinks biochar will be adopted. Green is almost as hopeful: "We have proven we can gasify chicken shit, and that we can gasify human shit. Now, if we could only gasify all the bull shit on this subject we could supply the energy needs of the world," he joked.

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Photos: Alex Green, Robert Flanagan, Johannes Lehmann

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