With the effects of climate change and ocean acidification caused by greenhouse gases worsening, government bodies worldwide are pressed to find a way to curb with carbon dioxide emissions. But with fossil fuel still proving to be the dominant source of fuel and with the recent G8 agreement to target a 50% reduction in carbon dioxide emission by the year 2050, it may seem to be a daunting task. Therefore, there is a need to find a technology that allows us to continue the use of fossil fuels but with minimal or zero carbon dioxide emission.

One such technology is Carbon Capture and Storage or CCS. The basic principle behind CCS is this - Capture and isolate the carbon dioxide produced during the combustion of fossil fuel and then store it. A very simple idea but it may not be as simple as it looks. To facilitate the understanding of CCS, I will be breaking it down into 2 parts : Part 1 - Capturing the carbon dioxide and Part 2 - Storage of carbon dioxide.

Capturing the Carbon Dioxide

There are several methods of capturing carbon dioxide. Theses methods can either be human induced or it can happen naturally. Lets take a look at them.

1. Pre-combustion

Carbon dioxide is captured from a gas mixture produced by partial oxidation of natural gas or biomass. As the mixture contains predominantly hydrogen and carbon dioxide, physical absorption is used to capture the carbon dioxide.

2. Post-combustion Capture

Carbon dioxide is captured at low pressure and low carbon dioxide content from flue gas by separation from nitrogen and oxygen gas. This is achieved through the use of chemical absorption by monoethanolamine.

3. Oxyfuel combustion

For this process, oxygen is separated and is then used to burn fossil fuels. A part of the flue gas, which consists mainly of carbon dioxide and water is recycled to the combustion chamber to enhance the carbon dioxide concentration for subsequent removal.

4. Direct Capture from the atmosphere

This method can be achieved by building “carbon scrubbers” or towers that can capture carbon dioxide from the atmosphere.

5. Biological Capture

CCS may seem to be a new technology to us but in fact it has been occurring naturally throughout history. The ocean has the natural ability to absorb atmospheric carbon dioxide. According to a report by RSC(Royal Society of Chemistry), about 90 gigatonnes of carbon are exchanged between the ocean and the atmosphere each year with a net uptake by the ocean of 2.2 gigatonnes. It is because of this ability and also with the increase in carbon dioxide emission that is causing ocean acidification.

Now with a better understanding of how the carbon dioxide is captured, in the next part, I will present how the carbon dioxide is stored. Do stay tune.

Refer to part 2 of this article : What is Carbon Capture and Storage : Pt 2 - Storing Carbon Dioxide

Image - IEA Green