What is Carbon Capture and Storage?
Friday, December 11, 2009 at 05:30PM By Lester Tan
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.
After being captured, the carbon dioxide can be either stored undergound ( geological sequestration ) or in the ocean ( ocean sequestration ).
Geological Sequestration
1. Oil fields and Aquifier Storage
The carbon dioxide that is captured can be stored in depleted or depleting oil and gas fields, deep saline aquifiers and unmineable coal seams. The benefits of pumping carbon dioxide in existing oil fields is that it actually improves oil yield and the carbon dioxide is stored in the fields. This greatly help in the development of enhanced oil recovery ( EOR ) projects. Storing carbon dioxide in saline aquifiers is also possible as deep saline aquifiers has the potential to store huge quantities of carbon dioxide.
One example of carbon storage in saline aquifiers is at the Sleipner West field in the Norwegian North Sea . It is operated by Statoil.
2. Carbon dioxide Sinks
Carbon dioxide sink is actually a European project where they aim to store carbon dioxide in subterranean rocks. Recently, Germany has inaugurate Europe's first underground carbon dioxide storage site. 60,000 tonnes of carbon dioxide will be pumped into the porous, salt- water filled rocks at depths of more than 600m over the next 2 years.
Pros and Cons of Geological Sequestration
Pros
1. We can store the carbon dioxide with our current infrastructure like oil fields
2. Can help to improve oil yield
Cons
1. May not have enough geological reservoirs to store the carbon dioxide
2. The carbon dioxide may leak due to the corrosion of the cement walls that lines the well
Ocean Sequestration
1. Use of marine phytoplankton
Marine phytoplankton assimilate carbon from seawater and when they die, they carry the carbon eith them to the deep ocean. However, phytoplankton growth is limited by the lack of the nutrient, iron. Thus if iron were to be introduced into the ocean to promote the growth of these phytoplankton, it could help in the absorption of carbon dioxide. But these method has many downsides. Firstly, very little of the carbon dioxide is taken in by the phytoplankton makes it to the deep ocean. Instead, as the phytoplankton decays, it releases the carbon back into the water. Secondly, if the growth of these phytoplankton were to be left unattended, it could cause the region of the ocean to become a dead zone because as the phytoplankton dies and decomposes, it actually requires oxygen.
2. Direct Injection into the Deep Ocean
By injecting carbon dioxide into the ocean at a depth of 3000m, the carbon dioxide can be kept away from being in contact with the atmosphere for 200 years. At ocean levels between 800 and 3000m a stream of liquid carbon dioxide is less dense than seawater and tends to rise to the surface, slowly mixing and dissolving with the surrounding water. At below 3000m liquid carbon dioxide reacts with the seawater to form clathrate, a solid ice-like substance that is denser than the surrounding water.
Pros and Cons of Ocean Sequestration
Pros
1. The ocean has an enormous natural capacity to absorb and store carbon
Cons
1. Environmental Issues - storage of carbon dioxide in the deep sea may lead to the pH of the seawater to decrease and become acidic.
2. Social Issues - Some consider carbon dioxide to be an industrial waste and thus dumping it in the ocean is similar to contributing to water pollution.
The setback of CCS is that it requires energy and with this we need to use more fossil fuel. The intergovernmental panel on climate Change (IPCC) estimates that the cost of CCS technology would increase the energy needs of power plants by 10-40% and increase the cost of energy from plants by 30-60%. One solution would be to use renewable energy to provide for the energy required.
Because of the global impact of this issue, it cannot be addressed by any one nation or by special-interest sector. It must be addressed at an international and intergovernmental level. But first, we need to promote public awareness so as to let the public understand and accept CCS as a safe and technologically sound option for carbon dioxide abatement.
References
Physorg.com, 2008, Germany to start storing carbon dioxide underground
<http://www.physorg.com/news134055385.html>, 17th July 2008
RSC.org, 2008, Can we bury our carbon dioxide problem
<http://www.rsc.org/ScienceAndTechnology/Policy/Bulletins/Issue3/CarbonDioxide.asp>, 17th July 2008
Ioc.unesco.org, Ocean Brief: Ocean sequestration
<http://ioc.unesco.org/iocweb/co2panel/sequestration.htm>, 17th July 2008
Article source: http://EzineArticles.com/?expert=Lester_Tan
NOTICE - All Rights Reserved Except as Stipulated Below. PHOTOS MAY NOT BE REPRODUCED IN ANY FORM. Our reporters and journalists break or report stories and their sources and information are protected by the doctrine of free press as expressed in the First Ammendment, Reporters Privilege Statues, and also the Canadian Charter of Rights and Freedoms.This article if a feature or opinion piece is the opinion of the author or reports the news and opinions of others and is NOT INTENDED TO OFFER ADVICE. FOR OPINION STORIES: This story/article/ feature may be an opinion piece — and should be treated accordingly — or reporting on the opinions of others, and should never be considered as a sole source of information or as a suggestion, instruction or prescription. FOR CRIME STORIES: always read the word "allegedly" in any story mentioning "suspects" or "persons of interest". FOR BUSINESSS AND MONEY STORIES: For money/ trade and exchange stories, this magazine and its writers accept no responsibility for accuracy — always check with other sources for important decisions. FOR HEALTH AND LIFESTYLE STORIES: In the case of food/health stories, these facts have not been evaluated by the United States Food and Drug Administration (FDA). Information stated here should be NOT be considered as medical, health, psychological or behavior advice. All information in this story and on this site is provided for educational or entertainment purposes ONLY. Always seek the advice of experts, including doctors for medical opinions. Only a licensed medical doctor can offer medical advice. FOR EXPERT, ADVICE OR HOW-TO STORIES: Legal advice or other expert advice is best referred to experts in their respective fields. NO RESPONSIBILITY: The publishers and editors, authors, researchers, employees, heirs and assigns accept no responsibility whatsoever for any advice, facts, opinions in this story, nor for resulting actions of readers of this information. ALL READERS ACCEPT THAT THIS INFORMATION IS PRESENTED ONLY AS NEWS, EDUCATION, ENTERTAINMENT OR OPINION/INFORMATION AND AGREE IN READING THIS STORY OR THIS SITE THAT USE OF THIS INFORMATION IS SOLELY THE RESPONSIBILITY OF THE READER. Copyright by the byline author unless otherwise indicated. EXCERPTS from other magazines or media sources are posted under fair use doctrine, on the basis of no more than 5-10% of content with links and credit to source for the complete story. These are posted in the interest of providing interesting links (description as excerpt) with navigation to the source. Likewise, we encourage our many subscribers to excerpt with credit and links to our e-zines, up to 10% of content. To use more content than 10%, please contact the e-zine for permission. ALL RIGHTS RESERVED except as stipulated herein. IMPORTANT: this web content also includes a forum and comments function, which allows for posting from users not employed by this publication. We accept no responsibility for posts, content, language or accuracy of posts from outside parties but will attempt to correct any inaccuracies reported within the context of free speach. Where possible, spam, lewd or obscene comments WILL BE REMOVED.
Persona Corp. and Blogertize publishes several webzines, magazines, e-zines for news, entertainment and information, but cautions readers to read the NOTICE above:
* Secure Network News Sponsored Advertisers Jameson Bank – Canada's "It's Taken Care Of" Bank Amer.com – Technology for Life
Reader Comments