"We cannot neglect any technology that will assist us to address the matters of energy security and climate change," said Energy Minister Dipuo Peters on Tuesday, as she officially opened the South African Carbon Capture and Storage (CCS) conference.

She explained that although South Africa did not have binding greenhouse gas (GHG) emission mitigation targets under the Kyoto Protocol, the country has a long-term mitigation scenario (LTMS), under which it committed to increase GHG emissions only until 2020, plateau those emissions until 2025, and then reduce emissions.

"The answer is CCS. We must wean ourselves of coal and onto nuclear and renewable energy," Peters said.

South African Centre for CCS head Dr Tony Surridge noted that for South Africa, CCS was a transitional technology, as the country moved from being heavily reliant on coal-fired power generation, to including more nuclear power and renewable energy technologies into the energy mix.

Peters highlighted that the achievement of the goals under the LTMS also included implementing energy efficiency, and renewable energy projects. "Renewable energies are being studied and implemented - although not fast enough," she added.

Surridge emphasised that the conference started from the premise that GHG emissions caused climate change, and Peters said that CCS was one, of a suite of key technologies being relied upon to mitigate emissions.

The South African centre for CCS was currently establishing storage atlas, to identify geological storage sites for the captured carbon dioxide (CO₂). This was expected to be completed by mid-2010, and would form the basis for future geological storage in South Africa.

Once the atlas is completed, a test injection site will be identified to determine the suitability of local geology as a storage medium, and this was expected to be completed by 2016. Next on the South African CCS road map was a demonstration plant by 2020.

International Energy Agency GHG research and development programme manager John Gale noted that, currently, the total anthropogenic CO₂ being captured and injected worldwide, was about five-million tons a year. This would need to be increased significantly if future emission reduction targets were to be met.

The major plants in operation today, storing CO₂ were: Snøhvit in the Barents Sea; Sleipner, also in the North Sea; Weyburn, in Canada; In-Salah, in Algeria; and Rangeley in the US.

Peters also highlighted that the mitigation of GHGs was a global matter requiring a global approach, with international co-operation. Thus, she welcomed the international experts in CCS research who were in attendance at the CCS conference in Johannesburg.

CCS is described as a fairly simple principle of extracting CO₂ from exhaust emissions, and re-injecting it underground, where the fossil fuel originated. In practise, it is more complicated and CCS is broken down into four stages: capture, which separates CO₂ from other exhaust gases, like nitrogen; compression and transport to the storage site through a pipeline; injection of the gas into a depleted gas or oil field or deep saline aquifer; and monitoring and verification to ensure the CO₂ stays buried.

CO2 can be captured from large single-source emission sites, such as power stations and synthetic fuel plants. In fact, South Africa's Sasol and PetroSA synfuels plants are said to be in a prime position for CO₂ capture, as they already produce a stream of almost 95% concentrated CO₂ through coal-to-liquids processes, bringing down capture costs.

Research is being done into capture from other industrial sources, such as cement production facilities.

Storage must be at depths below 800 m, as the CO₂ becomes a supercritical liquid and occupies less space. It is not trapped in a cavernous space, but within porous rock, like a sponge. It is trapped underground by the cap rock, as well as by the capillary action of the ‘sponge' storage rock; and, in the case of deep saline aquifers, it is trapped by dissolving in the water; and, finally it is trapped through a process of calcification as the gas becomes part of the rock - the reaction takes times, but at this stage storage is permanent.