Ocean may be new CO2 dumping ground
ABC Science Online
Dissolving CO2 deep in the oceans needs to be considered, says a German expert who is calling for more research (Image: iStockphoto)
Pumping carbon dioxide into the oceans may be one way to help save us from global warming, says a chemical engineer who admits the subject is “taboo”.
Professor Wolfgang Arlt, who has been visiting Australia’s Swinburne University of Technology in Melbourne, says governments see this so-called ocean sequestration as too politically risky, compared to geosequestration, when CO2 emissions are buried underground.
Since ocean sequestration was first proposed 20 years ago, Arlt says it has been the subject of relatively little research, and he is calling for more.
“I want to have every option equally researched,” he says, emphasising that reduction of CO2 emissions is the first priority before any form of sequestration.
Alrt, who is based at the University of Erlangen-Nuremburg in Germany, stresses he is not supporting ocean sequestration, only its investigation as an option to help stop global warming.
Arlt’s speciality includes the science of separating different chemicals such as CO2 and air and he calls ocean sequestration “the natural option”.
“Nature does it already,” he says. “If you look at our total emissions of carbon dioxide, one part is stored in the air, and the other part is dissolved in the ocean.”
The oceans are Earth’s main buffer system, he says.
He says increased concentration of CO2 in the atmosphere has led to increased amounts of the gas dissolved in the surface of the ocean and this in turn has led to an increase in ocean acidity that is harmful to marine life.
But, says Arlt, his initial calculations suggest ocean sequestration does not have to significantly increase the acidity of the oceans as long as the CO2 is injected deep into the ocean and is mixed across the whole planet.
Arlt says CO2 can be injected into “down-welling” areas of the ocean and, in its dissolved form, will tend to stay at the bottom of the ocean where it can then be mixed by deep ocean currents across the planet.
He says one modelling exercise suggests CO2 injected near Europe will be distributed as far as Australia in 100 years time.
Arlt says he predicts that the effect on ocean acidity using this method would be so small it would be unmeasurable, and would not affect sea life on the ocean bottom. But he thinks this should be investigated further.
He says another option is to neutralise the CO2 before sequestering it in the oceans by mixing it with alkaline minerals such as limestone.
IPCC warns on ocean acidification
A recent report on CO2 capture and storage from the Intergovernmental Panel on Climate Change (IPCC) canvasses options for ocean sequestration but does not include Arlt’s argument.
The report says ocean sequestration could help lock up CO2 for hundreds of years, with deeper injection being more effective than shallower injection.
But it warns increased acidity at the ocean surface can harm marine organisms.
The report does not mention Arlt’s point about down-welling waters and deep ocean currents.
Alrt says the IPCC had wanted him to co-author the report, but because of time problems he did not contribute.
“So my ideas are not inside the report,” he says.
The IPCC report notes that the effect of increased CO2 in the deep ocean has yet to be studied.
Whole range of options
An Australian co-author of the IPCC report, Dr Peter Cook, chief executive of the Co-operative Research Centre for Greenhouse Gas Technologies, agrees little is known about ocean sequestration and more research is always good.
“We’re going to need the whole range of options for decreasing CO2 emissions,” he says.
But he says the IPCC took a “very cautious view” about the future of ocean sequestration.
“We have to be very careful about doing it before we have a great deal more information,” Cook says.