Washington, Jan 30 : New calculations by scientists suggest that making bales with 30 percent of global crop residues, and then sinking them into the deep ocean could reduce the build up of global carbon dioxide (CO2) in the atmosphere by up to 15 percent a year.

According to Stuart Strand, a University of Washington research professor, that is a significant amount of carbon.

The process can be accomplished with existing technology and it can be done year after year. Further, the technique would sequester - or lock up - the carbon in seafloor sediments and deep ocean waters for thousands of years, he said.

Strand has devised a formula to measure the carbon-sequestration efficiency of this process and others using crop residues, something no one has done before.

Carefully tallying how much carbon would be released during the harvest, transportation and sinking of 30 percent of U. S. crop residues and comparing that to how much carbon could be sequestered, Strand said that the process would be 92 percent efficient.

That's more efficient than any other use of crop residue he considered, including simply leaving crop residue in the field, which is 14 percent efficient at sequestering carbon, or using crop residue to produce ethanol, which avoids the use fossil fuels, but is only 32 percent efficient.

Worldwide, farming is mankind's largest-scale activity.

According to Strand, thirty percent of the world's crop residue represents 600 megatons of carbon that, if sequestered in the deep ocean with 92 percent efficiency, would mean the amount of CO2 in the atmosphere would be reduced from 4,000 megatons of carbon to 3,400 megatons annually.

That's about a 15 percent decrease, he explained.

Strand bases his calculations on using 30 percent of crop residue because that's what agricultural scientists say could sustainably be removed, the rest being needed to maintain carbon in the soil.

Crop residue would be baled with existing equipment and transported by trucks, barges or trains to ports, just as crops are.

The bales would be barged to where the ocean is 1,500 meters, or nearly a mile, deep and then the bales would be weighted with rock and sunk.

"The ocean waters below 1,500 meters do not mix significantly with the upper waters," Strand said. "In the deep ocean, it is cold, oxygen is limited and there are few marine organisms that can break down crop residue. That means what is put there will stay there for thousands of years," he added. (ANI)