Researchers: Cut Carbon Dioxide by Dumping Crop Waste into the Ocean

It’s a decidedly low-tech way to deal with a 21st century problem, but a newly published paper argues that the world can cut carbon dioxide emissions up to 15 percent a year by taking the crop waste leftover after the harvest and dumping it into the deep ocean.

Stuart Strand of the University of Washington and coauthor Gregory Benford of the University of California at Irvine argue in the journal Environmental Science & Technology that such a reduction is possible by dumping 30 percent of world crop residues at least 1,500 meters deep in the oceans. The method would lock up the carbon in the crop waste deep underwater for thousands of years, the authors said.

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The deep ocean waters do not mix with waters and currents closer to the surface and would lock the crop waste in place. And if the wastes are dumped near “alluvial fans”– places off the edge of the continental shelf where rivers meet the ocean–the waste would be buried by silt from those rivers (see map). The cold waters would prevent decay, the authors say.

If 30 percent of the world’s crop waste is sunk annually, it could remove about 600 megatons of carbon–a roughly 15 percent reduction of CO2 in the atmosphere. Strand worked out a formula to rate the efficiency of other methods of disposing of carbon, and said his process topped the rating at 92 percent efficiency.

Even turning the crop waste into ethanol is only 32 percent efficient, the authors said.

The authors suggest baling the crop leftovers and trucking them to barges that would move the stuff to deep waters, where it could be sunk and weighted down with rocks.

While the technology for offshore burial already exists, it’s not clear how much it would cost. One recent estimate from the Earth Policy Institute estimated that carbon sequestration would cost $210 per ton through tree planting and agricultural management practices.

This clearly remains in the idea stage of development. No matter how secure and stationary the waste might be, the idea of dumping anything in the oceans is sure to be a hard sell. The authors call for more research on just how such a scheme would impact the creatures living in those deep sea zones.

Map Credit: University of Washington

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