Seeding the world's oceans to capture carbon is costly
By Sid Astbury, dpa
January 2, 2013, 12:02 am TWN
SYDNEY--One way to curb greenhouse gases that speed climate change is to seed the ocean with iron dust to create plankton blooms that suck in carbon dioxide and then sequester it on the ocean floor.
The science is not in question: after Mount Pinatubo in the Philippines erupted in 1991 and spread 40,000 tons of iron dust over the ocean there was a measurable decline in carbon dioxide in the atmosphere.
What is in doubt is the economics: Can this form of geo-engineering ever be made cost-effective? Sydney University engineer Daniel Harrison thinks not.
His study, published in the International Journal of Global Warming, shows that supplying iron to iron-deficient areas of the ocean does not store carbon long enough to be a commercially attractive contributor to climate management.
Weighing on the economics is the difficulty of making sure you are seeding in the right place at the right time.
"It may be very difficult to identify you were fertilizing under the ideal conditions until afterwards," Harrison said. "And every time you fertilized under less than ideal conditions you push the overall cost up towards the very high average cost I calculated for the Southern Ocean."
His study of geo-engineering in the stretch of water to Australia's south found that spreading iron sulphate only when conditions were absolutely ideal would mean the overall contribution to cleaning up the planet would be very small.
The study used average results and calculated the price at 400 U.S. dollars per ton of carbon dioxide sequestered from the atmosphere for 100 years or more.