Ocean seeding a dead duck as carbon solution
Plankton won’t save the world
Seeding the ocean with iron to encourage plankton blooms works – kind of – but as a carbon sequestration approach, it’s hugely expensive, inefficient and probably ineffective, according to a Sydney University researcher.
The geo-engineering idea hit the headlines earlier this year when American Russ George dumped 200,000 pounds (more than 90,000 kg) of iron sulphate in the northern Pacific Ocean to spark a plankton bloom. The plankton consume carbon and, when they die, carry it to the bottom of the ocean, thereby sequestering the carbon for up to 100 years.
The problem is not in the theory, says Sydney University postgraduate researcher Daniel Harrison, here. It’s about efficiency. Harrison’s work, to be published in the International Journal of Global Warming, provides a sobering assessment of the cost of “plankton sequestration”.
He suggests that the mean price of using iron to drive plankton growth is $AU400 per tonne of carbon dioxide sequestered for 100 years or more. In Australia, a carbon permit currently trades at $AU23 per tonne.
Harris came to this conclusion by analysing the outcomes of published experiments. He told the Sydney Morning Herald the problem is that “the perfect conditions you would need are so rare that it would be a very limited contribution to the problem.”
Fertilising a square kilometre of the Southern Ocean would, he said, sequester only about 10 kg of carbon – far less than the fuel consumed by the boat on an out-and-back journey. ®
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