AG-BIO: Keeping CO2 Down on the Farm
New farm practices and new breeds of crops might someday aid in controlling greenhouse gases that contribute to global climate change. Research under way at Purdue University (West Lafayette, IN 47907; Tel: 765/494-4600; Website: purdue.edu) seeks to corral carbon on the farm in a process known as carbon sequestration. The research is being supported with a grant of nearly $1 million to Purdue from the Consortium for Agricultural Soil Mitigation of Greenhouse Gases (CASMGS, pronounced “chasms”), a nine-university consortium of which Purdue is a member. Kansas State University is administering the $15 million program.
According to CASMGS, as much as 20% of the projected carbon emission reduction called for by the Kyoto Protocol could be accomplished by using U.S. farmland. Ronald Turco, professor of agronomy and director of the CASMGS program at Purdue, says that such a decrease would be enough to offset the United States’s annual contribution to carbon dioxide in the atmosphere.
“We’re hoping that with enhanced agricultural production methods we can take that annual increase to zero just by trapping the plant residue carbon in soil,” Turco says. In addition to production practices to aid carbon retention, Turco thinks it will be possible to develop new crop plants that help sequester carbon.
“Much of the carbon is held in the soil in what we call aggregate soil structures, and we’ll be looking to find exactly what part of the plant goes into creating those aggregate structures,” says Turco. “Once we know which parts of the plant are involved, we can genetically modify plants to increase the amount of those plant materials in our crops.”
As they grow, green plants and trees fix carbon dioxide from the atmosphere and convert it to tissue. After they die, the carbon in their tissue is incorporated into soil material and can remain in the soil for hundreds or thousands of years. Some of that carbon is released naturally into the atmosphere as carbon dioxide, but human activity has sped the process. Fossil fuels, such as coal and oil, are carbon-based and release carbon into the atmosphere as they are burned. Also, cutting forests can cause an increase in carbon dioxide in the atmosphere as carbon that was held in the trees is released.
Carbon can be released from the soil into the atmosphere when it combines with oxygen. This can happen when a carbon-based fuel, such as gasoline, is burned. But it also can happen when a plow turns over the soil before planting. “Every time you put a plow in the soil it lets in oxygen and stimulates microbial activity,” Turco points out. “Increased microbial activity will result in carbon dioxide being released into the atmosphere.” Charles Rice, professor of agronomy at Kansas State University and director of the CASMGS program, says carbon dioxide in the atmosphere began rising in the 1700s and continued until today.
“Approximately 50% of the carbon in the soil, which was held in the organic matter, has been lost over the last 50 to 100 years in the United States,” Rice said. “However, rather than look at this as a loss, we can look at it as the potential for returning and storing carbon in agricultural soils.”
Rice said the CASMGS program will be investigating ways that agriculture can reduce greenhouse gases such as carbon dioxide. “The goal is to determine the potential and how to implement carbon sequestration into agricultural soils,” he says. “We are also looking to reduce the other greenhouse gases in an agriculture system, particularly nitrous oxide and methane.”
“Economic analysis suggests that carbon sequestration in the soil is one of the most beneficial and cost effective options available for reducing greenhouse gases,” he says. “This is particularly true over the next 30 years until we are able to develop alternative energy sources with less use of fossil fuels.”
Turco says adding carbon to the soil will do more than help the environment. It also will help farmers by improving soil quality. “Putting carbon in the soil improves tilth, soil structure, nutrient retention, rooting depth and stability. All of the good things you can think of with soil are attributable to adding carbon and increasing soil organic matter,” claims Turco.
In additional to improving the soil, farmers may also see a more direct benefit in the form of payments. According to CASMGS, the potential market for carbon credits is $1 billion to $5 billion per year over the next 30 to 40 years.
“You can imagine a stock exchange-type trading system where farmers sell carbon credits to companies that need to buy them to stay in compliance with environmental regulations,” Turco says.
Purdue, through its partnership with CASMGS, is developing a Web- based system that would allow such trading to take place. Bernie Engle, professor of agricultural and biological engineering, is developing a Web site that would list the amount of carbon sequestered at particular sites, such as individual farms.
“We’ve built similar Web sites for water quality and other environmental issues in agriculture,” Engle says. “Since carbon uptake is related to so many environmentally friendly farming practices, such as no-till, this is a natural extension of our work.”
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