by Lawrence George

Created on: September 07, 2010   Last Updated: February 19, 2011

Climate Change is the most serious issue facing the world today. It might be shrouded in political controversy, but the science is clear - the world is warming because of increased carbon dioxide in the atmosphere. Our whole economy is driven by oil and coal, the two major contributors to the increasing carbon dioxide (CO2) levels. So one way of trying to prevent climate change without ceasing or revolutionising power generation is to try and prevent some of that CO2 escaping - to capture it, in other words, and then to store it somewhere.

Carbon capture and storage (CCS) is the term we give to the idea of preventing coal and oil-fired power stations pumping CO2 straight into the air. Essentially, the carbon dioxide is extracted from the emissions and transported elsewhere, without entering the atmosphere at any point.

There are different ways that this can be achieved. Some are already in use: BP has a plant in the Sahara which pumps carbon dioxide into porous rocks, which will hold it in the same way they hold natural gas.  Indeed, some ideas suggest transporting the carbon dioxide by pipeline to former oilfields, where there is already space for it in the rocks. CO2 could also be pumped into saline aquifers - underground reservoirs of water in porous rocks that is too salty to drink. This is currently being researched, because more needs to be known about the geological structures affected.

The three main types of carbon capture and storage are known as pre-combustion, post-combustion and oxyfuel. Post-combustion CCS involves separating the CO2 from the gases created by burning coal through a chemical reaction. The carbon dioxide, once isolated, can be removed and stored. Pre-combustion CCS is similar, but happens before the coal is burned. It leaves hydrogen as the main -clean - fuel once the carbon dioxide is taken away. However, this does involve building completely new plants. Oxyfuel CCS means burning the coal in pure oxygen. This creates a mixture of carbon dioxide and steam. The steam is easily cooled and thereby separated from the CO2. 

The current estimates are that CCS can capture significant amounts of carbon dioxide. In the UK, the government has begun a project to build power stations which will capture up to 25% of produced CO2. The UK in particular has no choice but to expand its power stations, because it is facing a shortfall of 15-20 Gigawatts by 2015.

Theoretically, a very efficient form of CCS could reduce the emissions of a

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