Geological storage of CO2
Carbon capture and storage is the process of collecting CO2 from industrial sources, compressing it and transporting it to a storage location where it remains isolated from the atmosphere. Current plants are capable of capturing between 85 and 95 per cent of the CO2 they process. There is an energy cost; a power plant with a CCS facility would use 10 to 40 per cent more energy than a plant without. However, the net result would still be a reduction of CO2 emissions of between 80 and 90 per cent.
There are several approaches to storage. Geological storage, or geosequestration, is the most advanced. This involves trapping the CO2 in deep geological formations, such as oil and gas fields and unminable coal beds. Ocean storage, in which CO2 would be fed into the water column from ships, platforms or fixed pipes, is still in the research phase. Below 3,000 metres, CO2, which at that depth is denser than water, is expected to pool, delaying its release into the environment. The ecological impact of this approach is still being assessed, but experimental "tracer" data and model calculations suggest that, depending on the depth and location, the fraction of C02 retained after 100 years would be between 65 and 100 per cent and after 500 years between 30 and 85 per cent.
Another area of research is mineral carbonation; the reaction of CO2 with the metal oxides found in silicate minerals and, in small quantities, in waste streams, produces stable carbonates. However, the natural reaction is very slow and the necessary pre-treatment of the minerals is energy-intensive.
Published: January 17, 2010 04:00 AM