A Univ. of Sydney engineer has ruled ocean iron fertilization an uneconomical solution to carbon capture and storage despite its early promise.

Ocean iron fertilization is a process that attempts to encourage phytoplankton growth in regions with unused nutrients and stores carbon away from the atmosphere.

Daniel Harrison, a postgraduate researcher and author of a paper published in this month's International Journal of Global Warming, says while iron fertilization of high-nutrient, low-chlorophyll regions of the ocean captures and stores carbon dioxide from the atmosphere, it does not store carbon long enough to be an attractive contributor to climate management.

Iron fertilization is more expensive than carbon capture and storage (CCS) and is much more expensive than the Australian carbon price, which is currently charged at $23 per ton of carbon dioxide, says Harrison.

In his paper, Harrison argues that the cost of iron fertilization will vary with the oceanographic conditions at the time and location of fertilization, but in almost all situations it is an expensive operation. As well as being expensive, the amount of carbon stored for more than a century is so small that it is uncertain whether measurable storage will occur at all.

"This means that while under certain conditions the cost may be moderate, under less ideal conditions, iron fertilization may actually create more greenhouse gas than is sequestered," says Harrison.

The study used average results from iron fertilization experiments conducted in the Southern Ocean and concluded that the mean price will be over $400 per ton of carbon dioxide sequestered from the atmosphere for 100 years or more.

"If the ocean is to play a greater role in storing carbon, we will need to develop more effective and economical technologies that are competitive with abatement opportunities on land," says Harrison.

Harrison's research is being conducted at the Sydney Institute of Marine Science, part of the Univ. of Sydney's cross-disciplinary research program investigating the impact of climate change on the ocean. Attention at the university will now focus on other ocean carbon storage strategies that have promise to store carbon at less than $23 per ton of carbon dioxide.