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Independent Professional: Experienced educator and management consultant for engineering educational institutions, researcher, trainer, technical consultant on sustainable technologies, related to cement manufacturing and characterisation, using industrial and agricultural wastes in cement and concrete, durability of concrete and fuel cell power.

Saturday, March 21, 2009

Controling Climate Change: Land or the Oceans as the Carbon Sink

One effective method of sequestering carbon is through the massive burial of charcoal. It would mean farmers turning all their agricultural waste - which contains carbon that the plants sequestered through photosynthesis - into non-biodegradable charcoal and burying it in the soil. Then you can start shifting really hefty quantities of carbon out of the system and pull the CO2 down quite fast. Farmers burn their crop waste at very low oxygen levels to turn it into charcoal, which is then then ploughed into the field. A little CO2 is released but the bulk of it gets converted to carbon. The farmer gets a few per cent of biofuel as a by-product of the combustion process, which he can sell. This scheme needs no subsidy as the farmer makes a profit.

Another way is making bales of the crop residue – the stalks and such left after harvesting – and then sinking the bales into the deep ocean. With 30 percent of global crop residues, the build up of global carbon dioxide in the atmosphere could reduce by up to 15 percent a year, according to one calculation [2]. The 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 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. 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.

Strand and Benford [2] carefully tallied how much carbon would be released during the harvest, transportation and sinking of 30 percent of U.S. crop residues and compared that to how much carbon could be sequestered. They say 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. Sequestering crop residue biomass in the deep ocean is essentially recycling atmospheric carbon back into deep sediments.

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