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Carbon Sequestration in Farming Could Offset Carbon Dioxide Emissions


As farmers and ranchers struggle to earn a profit selling commodities in the ailing U.S. agricultural economy, many of them are looking for alternative ways to derive an income from the land. One promising new opportunity could be carbon sequestration. That's the technical-sounding name for a plan to reward producers whose crops take carbon dioxide - a greenhouse gas - out of the air and store it, as carbon, in the soil. Sequestration provides a small but valuable counter to the industrial carbon dioxide emissions many experts believe are causing global warming. The Bush administration is funding more research into carbon sequestration and its potential role as part of a farmland soil conservation program, although critics say the White House policy on global warming may limit any economic benefits to America's farmers.

In a windy field off Interstate 29 in Moody County, South Dakota State University soil chemist Jim Dolittle is surveying the growth of test plots of switchgrass. "Most often when you're looking at a field, you're seeing the above-ground portion of a plant," he said. "But what you can envision when we pull a plant up here you can imagine about the same amount of root material growing below the soil. And that's what we're studying: how much carbon is being added to the soil by that below-ground root mass."

Switchgrass, like other green plants, uses the sun's energy to take carbon dioxide from the air and build it into complex organic compounds. That's how plants grow. Carbon makes up about 40 percent of every plant. When crops are harvested or the plant dies, the root material rots. Some carbon dioxide is released into the air. But the rest of the carbon stays in the soil. This net movement of carbon from the air into the earth is the opposite of what happens when fossil fuels like gasoline and coal are burned. Combustion puts carbon dioxide into the air. Most scientists believe rising CO2 concentrations in the atmosphere are a major contributor to global warming.

That's why scientists like Jim Dolittle are trying to develop ways to get more carbon out of the atmosphere and into the ground. Still, he says carbon storage in farmland isn't a fix for global warming, because it can't offset the high CO2 emissions worldwide. "We are talking about a small amount of carbon," said Jim Doolittle. "But if we can have that small amount constantly flowing back into the soil, are hopes are that we can effect the atmospheric concentration of CO2 for reducing the greenhouse effect."

Studies by Professor Dolittle and other researchers suggest a larger role for conservation-style agriculture in the United States. The amount of carbon in the soil has actually dropped 20 percent since pioneers first tilled the virgin soils of the American prairie 200 years ago. Exposing the soil to the air meant more of the dead plant material there could decompose and release carbon dioxide. With less carbon, the soil also became less fertile. Bill Hohenstein, director of the U.S. Department of Agriculture's Global Change Office, says to reverse this trend, farmers must protect their soil carbon, using a variety of tillage practices. "Things like conservation or no-till," said Bill Hohenstein. "Or using winter cover crops. Those sorts of things are going to increase the organic content of the soil. And that's really what we're talking about when we're talking about soil carbon."

Beside soil carbon's agricultural benefits, it could also have a direct cash value for farmers. International efforts to reduce greenhouse gases like carbon dioxide have spawned a worldwide emissions-trading market. Companies and manufacturers that are required to reduce their CO2 emissions could do it in two ways: either by filtering carbon dioxide as it leaves the smokestack which is expensive or by paying farmers to change their practices so cropland captures more CO2 from the air and stores it in the soil. The U.S. Department of Agriculture estimates that based on the current price for so-called carbon credits, this could put an additional $300 million a year into American farmers' pockets.

U.S. Department of Agriculture analysts predict that as the carbon-trading market expands, cash payments to U.S. farmers could grow into billions of extra dollars annually. But the analysts note that before the carbon-trading market really becomes viable, farmers need a way to prove how much carbon their soils are capturing. So the Bush administration is funding more research to scientifically document how - and to what extent - farming practices sequester carbon. "We will look to increase the amount of carbon stored by America's farms through a strong conservation title in the farm bill," said President Bush. "I have asked Secretary Veneman to recommend new target incentives for landowners to increase carbon storage."

But another White House policy may limit the benefit farmers would get from carbon sequestration. The Bush administration has rejected the Kyoto Protocol, an international agreement on reducing greenhouse gases. The treaty officially recognizes carbon sequestration in farmland and crafts policy for carbon trading. If the agreement goes ahead without the United States, it couldn't require American CO2 emitters, the world's most prodigious, to cut emissions. Farmers fear that would significantly reduce demand for carbon credits, meaning they would earn less money. However, experts say eventually there will be more pressure for U.S. polluters to cut emissions and pay farmers to sequester carbon. Neil Cohn works for Natsource, a brokerage and consulting firm for emissions trading. "The Kyoto Protocol is, of course, one of the biggest drivers in the climate change process," said Neil Cohn. "It is not the only driver. And while the U.S. has backed out of the Kyoto Protocol Process, there will continue to be legislation on carbon constraints in the U.S., and this market is continuing to develop."

As the carbon-trading market develops, work at South Dakota State University and other research centers is revealing more clearly that agriculture has an important role in reducing greenhouse gases. SDSU soil chemist Jim Dolittle says that by adopting simple conservation practices, farmers can simultaneously improve the quality of the soil and help to combat global warming. But experts say it could take five to 10 years before farmers will get direct cash payments for it.

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