Jan. 30, 2009 -- Each year farmers in the United States reap enormous bounty from their endless corn fields and amber waves of grain. In all, some 300 million tons of food float down the Mississippi River toward waiting, hungry mouths.
But a new study suggests there is a second harvest to be had from America's vast bread basket, too -- one that could be an answer to global warming.
Sucked from the atmosphere through photosynthesis and sequestered in leftover husks and stalks are 150 million tons of carbon. Scientists now claim that all we need to do is toss them to the bottom of the sea, and a huge quantity of greenhouse gases be banished at a stroke.
"This is just recycling carbon," Stuart Strand of the University of Washington said. "It came out of the deep environment where it was stored for years as fossil fuels. We want to put it back."
Strand and co-author Gregory Benford of the University of California, Irvine have proposed what they see as a simple carbon sequestration scheme. Simply harvest about 30 percent of the straw and corn stalks left on the field after harvest, ship it out to sea on barges, weight it down, and dump in by the ton into the cold, dark depths of the Gulf of Mexico.
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If the process is mimicked for farms and crops around the world, Strand and Benford estimate their method would remove a total of 600 million tons of carbon from the atmosphere each year. That takes into consideration fossil fuels needed to transport the plant mass, which they think will emit 8 tons of carbon for every 100 tons they bury at sea. Worldwide, humanity's penchant for burning fossil fuels emits 8 billion tons into the atmosphere a year.
Compared to capturing carbon from a coal-fired power plant, or fermenting switch grass into cellulosic ethanol, the researchers' plan is technologically simple, too.
"As far as practicality, we could do this tomorrow, it's just a matter of loading up the barges," Strand said.
But some there are some major unknowns.
Depositing millions of tons of straw bales and corn stalks into a deep sea environment could have a profound impact on the local ecology. And John Harte of the University of California, Berkeley said that removing crop leftovers from fields could lead to longer-term increases in soil erosion, and declines in soil quality.
Shipping all that plant matter from the farm to the ocean could prove prohibitively expensive, too. The researchers calculated that each ton of carbon would cost about $340 to bury; in 2006 the price of carbon on the European market topped out at less than half that price.
"The real message of this paper is that to solve the problem of global warming, we need to keep thinking of new things," Harte said. "This may not make a big contribution, but we need to give it some more consideration -- it's a mistake to think that all of the good ideas have already been thought of."
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