Durban – South Africa’s plan to dump millions of tons of carbon dioxide deep below the earth could trigger earthquakes strong enough to crack open underground rock seals, causing greenhouse gas to leak back into the air.

This is the fear raised by two US university professors that has generated widespread debate in several countries hoping to combat climate change quickly by burying carbon dioxode (CO2) underground, instead of reducing greenhouse gas emissions.

South Africa plans to open the country’s first CO2 storage demonstration site in 2017, somewhere north of Lake St Lucia in KwaZulu-Natal or possibly near Port Elizabeth.

Known as carbon capture and storage, the controversial technology is being used to bury CO2 in parts of Europe, Australia, the US and oil-rich north Africa.

The local demonstration site would be designed to test the feasibility of dumping some of the 400 million tons of CO2 emitted each year from Eskom power stations, fuel refineries, cement-making and other forms of heavy industry.

This could entail burying large volumes in the sea off the Eastern Cape and the Western Cape.

But Stanford University geoscience professor Mark Zoback and his hydrogeology colleague Steven Gorelick have warned that there is a “high probability” that injecting large volumes of CO2 into brittle rock formations will trigger earthquakes.

“Because even small to moderate-sized earthquakes threaten the seal integrity of CO2 repositories, large-scale carbon capture and storage is a risky and likely unsuccessful strategy for significantly reducing greenhouse gases,” the two Stanford professors wrote in a scientific paper published in May 2012.

Soon after it was published, Massachusetts Institute of Technology associate professor of energy Ruben Juanes and two colleagues published a rebuttal, arguing that large volumes of fluids (including oil and gas) had remained safely locked away beneath the earth for thousands of years in areas where there were frequent earthquakes.

Responding in a fresh paper published in December 2012, the two Stanford University professors emphasised that they were worried that even small to moderate earthquakes could crack underground rock seals which prevented buried CO2 and other gases from leaking up to the surface.

SA Carbon Capture and Storage project manager Brendan Beck argued that Zoback’s and Gorelick’s conclusions had subsequently been “comprehensively rebutted by multiple international experts and organisations”.

“The common theme you will see is that although they all agree that the Zoback conclusions are unfounded, they also agree that it is critical with any carbon capture and storage project, that significant efforts are put into site selection and characterisation.

“As the process for the South African pilot project unfolds… if it is determined at any stage that there are any unacceptable risks associated with our geology then the project will not continue.”