Carbon capture and storage

  

Capturing carbon dioxide emissions from power plants and storing it underground is seen as a crucial technology to reduce the global warming impact of fossil fuels such as coal and gas, on which the world will continue to rely for decades.

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Overview

To fight global warming, governments are looking at technological solutions to keep the release of carbon dioxide in the atmosphere under control. One of the most promising technologies is carbon capture and storage (CCS, also called 'carbon sequestration').

The technology is seen as crucial to reducing the global warming impact of fossil fuels such as coal and natural gas, on which the International Energy Agency says the world will continue to rely for decades (see Shell's quick guide to CCS).

CCS usually involves a series of steps:

  1. Separating the carbon dioxide from the gases produced by large power plants.
  2. Compressing the CO2 into liquid form.
  3. Transporting it to a given location (usually via existing pipeline networks or shipped by trucks or ships).
  4. Injecting it into geological formations deep underground or under the ocean bed (often depleted gas fields). 

Depending on the the plant's location, CO2 can sometimes be directly injected underground, without having to compress and transport the gas to a suitable location. The CO2 is pumped straight underground, where it is compressed by higher pressures and essentially becomes a liquid, which then becomes trapped in the rock.

The science and technology behind CCS is already manifest, but has not yet been implemented with the intention of reducing CO2 emissions on a large scale. Further developments regarding CO2 capture and separation processes in particular will be needed if CCS is to be accepted as a fully fledged mitigation solution for climate change. Costs will also need to be brought down if the technology is ever to be deployed on a commercial scale.

A distinction is usually made between two methods for CCS: 

  • Pre-combustion, where the CO2 is captured on location, during the extraction of natural gas or oil before it is burned. This process has already been tried and tested since 1996 by Norway at its Sleipner offshore platform in the North Sea (EurActiv 7/12/07).
  • Post-combustion, where the CO2 is captured during the process of burning coal or gas for electricity production. More research is needed into this area, which holds the most promise for climate change mitigation as it would allow countries that rely heavily on coal (China, US, Germany and Poland) to continue using this source of energy without putting the world's climate at risk. One of those capture technologies, oxy-fuel combustion, is proving to be the most advanced at the moment. Post-combustion techniques can also be applied to other energy-consuming industries, such as paper, steel, cement and refining.

A number of CCS demonstration projects are now at various stages of development all over the world. According to the IEA, CCS technology could be deployed by 2015 on a broader scale, should these demonstration projects deliver good results.

The main players in CCS are multinational oil and gas companies (ExxonMobil, Shell, Total, Statoil and others). For an overview of existing projects, see this map of existing CO2 capture projects and the European Commission's document 'European CO2 capture and storage projects'.

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