Tuesday, November 4, 2008

Adding lime to seawater

Shell Oil is funding a project that is studying the potential of adding lime to seawater to store carbon dioxide (CO2) in the sea.

Due to increased CO2 levels, the oceans have become more acid. Adding lime (calcium hydroxide) to seawater will increase the alkalinity of the water, making the water absorb more CO2 and reducing the release of CO2 from the water into the atmosphere.

Tim Kruger, a management consultant at London-based Corven, believes that this can be done most economically where there's plenty of limestone, and plenty of energy that is too remote to exploit for conventional commercial purposes.

"There are many such places — for example, Australia's Nullarbor Plain would be a prime location for this process, as it has 10,000km3 of limestone and soaks up roughly 20MJ/m2 of solar irradiation every day," said Kruger.

Although the process generates CO2 emissions, on paper it sequesters twice as much of the warming gas than it produces. Kruger says the process is therefore 'carbon negative'.

'This process has the potential to reverse the accumulation of CO2 in the atmosphere. It would be possible to reduce CO2 to pre-industrial levels,' he explained.

"We think it's a promising idea," says Shell's Gilles Bertherin, a coordinator on the project, which is being developed in an "open source" manner. "There are potentially huge environmental benefits from addressing climate change — and adding calcium hydroxide to seawater will also mitigate the effects of ocean acidification, so it should have a positive impact on the marine environment."

Sources and Links:

Shell Oil funds "open source" geoengineering project to fight global warming, at:
Mongabay.com

'Turning back the clock on climate change' - A technology to reverse climate change? To reduce ocean acidification? And that also promises to increase food production? Cath O’Driscoll investigates, at:
Chemistry & Industry Magazine

Adding lime to seawater feasibility study, funded by Shell, at: www.cquestrate.com

Inventory of geo-engineering proposals

Geo-engineering proposals seeking to combat global warming should be assessed according to efficacy, cost, risk, timeframe and the rate at which they can mitigate climate change, says Philip W. Boyd of New Zealand's NIWA in an article published in Nature Geoscience.

We need more thought on whether proposals like carbon burial, geochemical carbon capture, atmospheric carbon capture, ocean fertilization, cloud manipulation, space sunshades, or strategically-placed pollution can be effective on a time-scale relevant to humankind, economical, or even safe.

Meanwhile, AP reports that John Shepherd will head a working group at Britain's Royal Society to study geo-engineering proposals, with a report expected to be published in mid-2009.