Carbon capture and storage.

Carbon capture and storage is a proposed solution to the global warming problem by which human emissions of carbon dioxide (CO₂) from burning fossil fuels are reduced by capturing the gas “as it comes out of the chimney”. It is then transported to where it can be buried safely. The technology has most potential for coal, but could be applied in a lot of areas.

Carbon capture and storage is a highly industrialized approach to the CO₂ problem. It has obvious advantages over and above reducing emissions – the technology can be retrofitted onto today's coal-fired plants, capture (but not storage) technology is reasonably advanced, it can be applied to other CO₂-producing industries, it does not require major adjustments in society. It has one very serious drawback, which is that it will be very expensive indeed.

The technology exists to extract CO₂ from coal either before, during or after combustion of the coal. The latter is the most technically mature, involving passing the outgoing gas through a “scrubber” in which the CO₂ is chemically absorbed. About 85% of the CO₂ is removed from the gas, but the scrubber itself uses 10%-40% of the actual energy produced. The effective reduction in CO₂ is only 67%, and the cost of operating the plant is increased by 75%.

Storage technologies are less developed and have not attracted much funding outside Australia. Gas storage underground would preferably be in deep mines, old oilfields, or rocks such as sandstone which can absorb the CO₂, if they are overlain by an impermeable stratum. A few experiments are under way – Weyburn, Saskatchewan, and the oilfields Sleipnir in the North Sea and In Saleh, Algeria. Storage as liquid in the ocean is not favoured because of mixing with seawater.

Although there are many suitable rock formations for gas storage, they are not in general close to industrial centres where the power plants are. Any nation opting for this technique will require a gigantic infrastructure program to liquefy the CO₂, pipe it to the storage facility and bury it. This is probably the biggest drawback faced by this technology. It is a problem shared with other industrial-type approaches like the U.S. hydrogen-energy project.