[flv:http://pavementpieces.com/wp-content/uploads/2009/10/BiocharSlideShow.flv 320 240]

To anyone looking down on the small courtyard confined by towering apartment buildings, it may have seemed like a bizarre pagan ritual or a display of Boy Scout nostalgia. A small cloister of young New Yorkers stood around a roaring fire built in a hibachi grill, but the smell of hamburgers and kebabs was curiously absent. Instead, they stared intently at smoke spewing from a terracotta flowerpot sealed in aluminum foil.

In this tiny urban oasis, no bigger than the overpriced studio apartments that surround it, they spent all morning collecting fallen branches and dried leaves from a large tree that grew out of the concrete. Their collected detritus roasted in the flowerpot as their excited chatter accompanied the smoke rising from the fire. Finally, one of them removed the foil, peered into the pot, and declared a success.

A handful of brittle black matter emerged from the container — charcoal, but not just any kind. It was a special type of charcoal called biochar, and it was going to make their rooftop garden the most productive on the Lower East Side.

Biochar is a pure carbon product made from slowly burning biomass — stuff like wood, peanut shells, bamboo, or even manure. When added to the soil, it can improve soil quality and increase plant growth. It can also reduce the amount of fertilizers farmers use and prevent soil erosion.

In fact, studies in the early part of this decade by scientists at Cornell and the University of Georgia showed that biochar increased grain production in corn by as much as 50 percent compared with corn grown without biochar.

Biochar is a new idea for many American farmers, but in countries like Brazil, Australia, and Japan it’s agriculture as usual. In fact, Japanese farmers have been adding charcoal to their soil for over two decades.

Kazuaki Goto is the general manager of Radish Boya, a Tokyo-based company that runs Japan’s largest network of natural and organic growers. Since 1988, the network has connected small organic farms with households all over the country. Today organic vegetables from 2,800 producers reach 94,000 households.

According to Goto, 80 percent of the farmers in the network use biochar as a soil amendment to improve crop production.

“It helps the soil become healthier because it has the ability to pick up nutrients easier,” Goto said through an interpreter. “So in that sense it raises the yield and it stabilizes the quality.”

Biochar may sound like a fertilizer because it helps plants grow larger and produce better vegetables, but it’s not; and environmentalist and self-described “earth advocate” David Yarrow is quick to correct anyone who makes this mistake.

Yarrow frequently gives seminars on biochar and said that the magic of the charcoal is that it acts like a sponge for water and nutrients. It holds them in the soil as an easily accessible store for plants. It also enriches the soil by increasing the amount of friendly fungi and bacteria that live in the ground.

“Charcoal’s structure has a lot of holes,” Yarrow said. “Those holes become residential spaces for microorganisms, and eventually a sort of a rich ‘microbial reef’ is created in the soil.”

So instead of fertilizing the soil, biochar provides a stable structure that holds fertilizer and attracts communities of microorganisms making a rich mini-ecosystem in the soil in which plants thrive.

Yarrow also advocates for biochar as a carbon-negative strategy to help reduce global warming. Tilling charcoal into the soil, rather than burning it for fuel, captures carbon that would otherwise enter the atmosphere and stores it long term. So biochar can actually help reduce global warming.

“Don’t burn it. Put it in the ground,” Yarrow said. “Most people think it sounds outrageous, but other countries are already way ahead of us on this.”

Carbon is at the top of the environment’s most wanted list. When it enters the atmosphere as a gas — like carbon monoxide or carbon dioxide — it increases the greenhouse effect. But carbon that is trapped in its solid state as charcoal and buried in the soil won’t make it into the atmosphere for thousands years or more.

Theoretically, a person could reduce her carbon footprint by calculating her annual carbon emissions and then planting a comparable amount of biochar. This is the carbon-negative strategy. On a much larger scale, countries could compensate for their industrial-sized emissions by encouraging their farmers to use biochar on a large scale.

Dr. Christoph Steiner, a researcher at the University of Georgia, has studied biochar and soil composition for over a decade. In a presentation to the United Nations last December, he estimated that the U.S. has the soil capacity to plant 650 million metric tons of carbon that would offset American emissions by 11 percent every year.

“The [carbon capacity of the soil] is enormously big and we’ve already lost a big proportion of the soil’s carbon,” said Steiner. “But there are techniques to restore it and one of those could be biochar, which would be very efficient. There is almost no limit. You can add enormous quantities.”

Opponents of the strategy argue that greenhouse gasses like carbon monoxide escape into the atmosphere during the process of making the charcoal. So it could hardly be called a “carbon negative” success.

But scientists have developed the technology to capture the fugitive gasses and use them to produce energy. At the University of Georgia’s biomass conversion center, there is a machine that does just that. The project, called the “Eprida cycle,” is a collaboration between biotech entrepreneurs and researchers at the university.

The machine, as tall and wide as a warehouse, looks like something from Willy Wonka’s factory. A tangle of metal pipes snake around assorted tanks and gauges.

However, smaller versions exist in other parts of the world. For example in China, the process is condensed into a small cook stove for domestic use.

According to Steiner, biochar is not only carbon-negative, it is also a sustainable farming practice. He described the technique as an efficient carbon cycle where farmers gather the leftover biomass in their fields after a harvest. They make it into charcoal using something like the Eprida cycle so there are no emissions. Then they add the biochar to their fields, returning the carbon to soil and keeping it out of the atmosphere.

“Biochar gives us the option to remove crop residue, make renewable energy out of it, and bring the carbon back into the fields; and this is great thing,” he said.

For American farmers, biochar could increase the productivity of their fields and give them an advantage in the market.

Douglas Race has never heard of biochar. He is a third-generation American farmer. He owns a 100-acre farm in Blairstown, N.J., about 60 miles west of New York City, and has a staff of 10 to 20 people depending on the workload of the day. It’s a small family business — even his neighbors pitch in when it’s time to take the fresh produce to the farmer’s market in the city.

Like any small business owner, he is constantly working to stay competitive in the market. For Race, that means being up-to-date on the latest farming techniques. He frequently attends conventions to learn about new practices; and while he is open to new ideas, he has seen his share of failed trends.

“We’ve all done it,” Race said with a laugh. “That’s part of being in any small business is trying to get a step ahead of somebody else, trying something edgy and new; and we’ve all had our flops.”

But the flops don’t discourage Race and he continues to seek out environmentally friendly and sustainable farming methods. Biochar could be a helpful addition to Race’s sustainable farming efforts and could also give him that competitive edge in the market.

Every Monday, Wednesday and Saturday, the Race farm sets up a stand at the Union Square Greenmarket. All around, hand-painted signs shout “organic” and “locally-grown” like a worn mantra. Across the street, an organic supermarket bustles with shoppers seeking healthy, environmentally friendly food. It is clear that consumer interest in organic products has exploded.

In 2006, sales of organic food reached $3.6 billion in the United States — twice the sales in 2000. Estimates project that organic sales will increase more than 70 percent by 2011.

As the market for organic grows, more farmers and grocers are jumping in to meet the demand. In a cornucopia of organic food, small farmers like Race could use a little something to distinguish their produce from the rest. According to David Yarrow, Biochar would provide exactly that.

Carbon-negative vegetables could become the next big trend, he said. Environmentally savvy consumers would be attracted to tomatoes that combat global warming and carbon-trapping corn. But biochar still needs government approval before it is considered a safe and legitimate farming practice.

Currently, the US Department of Agriculture is plodding along in its biochar research. Last year, it granted $200,000 to the Ohio Farmers Union Family Farm Center for a biochar demonstration project. It also began a similar non-funded project in South Carolina with the Coastal Plains Soil, Water and Plant Research Center. A study released by USDA scientist David Laird called biochar a win-win scenario, but emphasized challenges facing the emerging technology.

The biochar saga is slowly beginning to unfold in the United States. It will take years before carbon-negative finds its way onto American grocery lists. Until then, biochar lurks in the farms of scientists, the gardens of environmentalists, and the back-alley courtyards of curious urbanites.