Toward a Carbon-Negative World 

Bear Kaufman says being carbon-neutral isn't enough.

Now that green consciousness has percolated into the mainstream, you may have begun to ponder your carbon footprint. Perhaps you've even paid to have a tree planted to offset the amount of carbon your energy use puts into the air.

Bear Kaufman hopes to help us go much further, all the way to becoming carbon-negative. The senior at San Francisco State University's earth system science department has been experimenting with a scheme to return most of the carbon created by generating power to the ground in the form of charcoal, where it can improve the soil. Tactics like this, which keep carbon dioxide from being released into the air, are known as sequestration.

"You can have an integrated system with energy production, carbon sequestration and — due to the application of the charcoal — agricultural benefits," Kaufman said. "It's win-win-win."

Burning almost anything organic releases carbon dioxide into the air. Carbon dioxide, or CO2, is one of the so-called greenhouse gases that are trapping too much of the sun's warmth. Green plants, and especially trees, use carbon dioxide for photosynthesis. But deforestation, combined with the heavy use of fossil fuels, has upset the balance.

In today's world, to become carbon-neutral you'd both reduce your carbon dioxide-emitting activities and offset the rest by paying for something that reduces carbon dioxide elsewhere, such as the construction of wind farms or reforestation projects. In Kaufman's world of the not-too-distant future, you'd burn some kind of renewable organic fuel like wood by-products or agricultural waste to generate power, and then plow the resulting charcoal, or biochar, back into the ground. This form of sequestration wouldn't just store the CO2, it would put it to good use. The key to making this a clean process is heating the organic matter under pressure in low-oxygen conditions to generate the maximum amount of heat with the least emissions, and then stopping the process while the carbon remains in the fuel.

Scientists first got interested in charcoal's power to build soil structure and retain nutrients in the early 1990s, when they noticed deposits of especially rich soil in the Amazon basin. These pockets of super-soil also contained pottery shards and fish bones. "It's not clear whether these sites were created intentionally, or whether they were just dumps," Kaufman said. In any case, biochar makes up 35 to 45 percent of the soil.

Kaufman has always been interested in environmental science, and biochar is an emerging technology that's early-stage enough so that even non-Ph.Ds working independently can contribute. "All the renewable energy options can provide energy that's carbon-neutral, and we need all of those things to get to a point where net emissions are low," Kaufman said. "But even then, we're probably going to have higher levels of atmospheric CO2 than scientists recommend."

Kaufman is part of a casual international network of professional and indie scientists who experiment and trade notes. Through September 20, he'll be working on the project at Berkeley's Shipyard, which in March was recast as a "Center for Art and Energy." The two-month-long experiment explores what's the optimal proportion of biochar to add to soil used for growing crops. First, Kaufman put batches of bamboo or fir chips through a slow burn to create the charcoal. He's already set up sixty flowerpots with varying proportions of sand, soil, and biochar, and planted wheat and pea seedlings.

Next, he'll weigh the plants' mass to see which thrived and which, if any, shriveled. Then, he'll analyze the data to get what he hopes is a definitive answer as to the best mix. In a previous experiment, a mix containing 30 percent charcoal gave the best results. That's a helluva lot of charcoal for a farmer to plow into the ground.

"If a farmer agrees to put ten tons of carbon into the field, she gets ten carbon credits she can sell," Kaufman explained. "It may be so beneficial you wouldn't need to pay her to use it." This scenario depends on a well-developed carbon market, where people could buy and sell permits to emit CO2. It's something that's beginning to shape up. On August 15, the Chicago Climate Futures Exchange completed the first trade of carbon permits; the exchange expects to officially launch next year.

There are some barriers, Kaufman admits. Because the biomass to be burned and the resulting biochar are heavy, the system breaks down if you have to transport them. Ideally, the biofuel plant would burn local vegetable matter to generate power that's used locally. For example, a large apartment complex might have its own bioenergy-generation station, and could sell the biochar to local gardeners.

Before you'll see charcoal cookers in the East Bay, however, someone will have to come up with a cooker that's both clean and unobtrusive. Then, they'll have to make massive changes to zoning regulations.

"My feeling is, there's going to be a broad array of different solutions that will be necessary," Kaufman said. "This probably won't be the solution, but it will be part of the broader solution."

Kaufman will publish his findings on TerraPreta.bioenergylists.org to contribute to the global knowledge base. Making good use of that extra carbon for growing crops could indeed be that win-win-win Kaufman is seeking. The Bay Area is a hotbed of work in alternative energy and, if his project leads to a career in the field, it will be a win for him, too.

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