Taming any kind of beast is a huge task in itself until off course you are some whiz kid or Super Hero. But we mere mortals have a task in our hand. That task is gaining significance as each second goes by and with each breathe we take. We have a job to do. We have to tame a beast or bury it underneath to survive. In our case the beast is even more dangerous as it slowly takes up a massive scale without us realizing the fact that it has outgrown to such an extent that our very existence is being questioned.
Can you guess which beast I am talking about? Let me give you some hints; this creature does not have any shape or size. You cannot see it with open eyes, unless it appears in its most dark form. These are the properties which has helped it grow bigger and stronger without us noticing its growth. Have you guessed it yet? If no then let me tell you that it is something which the Mother Nature has failed to tame and one of the strongest and peaceful ambassador of mother earth, the Trees are only able to keep it inside them till they have the Sun supporting them. But once the Sun God goes for a nap this creature splurge out of the trees and threatens the entire world!! It has become so powerful that it is now changing the way the world looks from high up in space.
Got it now? Its nothing but the thing we breathe out each moment. Yeah it is CO2 that I am talking about. It is something which looked pretty innocuous at the onset and till date. But it has grown to such grimmer proposition for mankind, that it is high time we do something about it. Or else humankind can get wiped out from the earth. The increasing amount of CO2 in the environment is causing global warming and that is not a new fact. It is causing havoc by melting polar ice at such a fast rate that the earth stands a chance of getting major portion of it submerged under sea water. The extensive use of the fossil fuels has led to tremendous increase in the CO2 content of the air and this has led to severe global warming problems. Without talking much about the global warming problems which is very much known to us, let us look into one approach which organizations world over are considering as a serious step to reduce the carbon emission.
Carbon capture and storage (CCS) is an idea that is used to reduce the contribution of the fossil fuel emissions to the global warming, based on capturing carbon dioxide (CO2) from large point sources such as fossil fuel power plants. This way the carbon dioxide might then be permanently stored away from the atmosphere. The term Carbon dioxide capture and storage are also be used to describe biological techniques such as biochar burial, which use trees, plankton, etc. to capture CO2 from the air. However, it is more conventional to use the term ‘carbon capture and storage’ to describe non-biological processes.
Now some statistics:
1. It has been calculated that CCS applied to a modern conventional power plant could reduce CO2 emissions to the atmosphere by approximately 80-90% compared to a plant without CCS.
2. The economic potential of CCS could be between 10% and 55% of the total carbon mitigation effort until year 2100.
3. Capturing and compressing CO2 requires much energy and would increase the fuel needs of a coal-fired plant with CCS by 25%-40%. These and other system costs are estimated to increase the cost of energy from a new power plant with CCS by 21-91%.
Current figures suggest that the cost of implementation of CCS, more so in an already existing plant, appears to be prohibitive. But proper R&D and steps towards the right direction might actually make CCS a more cost effective, efficient and without an iota of doubt a more environment friendly process.
Capturing CO2 might be applied to large point sources, such as fossil fuel or biomass energy facilities, industries with major CO2 emissions etc.
Mainly three processes are used for capturing the CO2:
1. Post Combustion Capture: Here carbon dioxide is captured from the flue gases obtained post combustion at the large point sources.
2. Pre-Combustion Capture: In these cases, the fossil fuel is partially oxidized, for instance in a gasifier. The resulting syngas (CO and H2) is shifted into CO2 and more H2. The resulting CO2 can be captured from a relatively pure exhaust stream. The H2 can now be used as fuel; the carbon dioxide is removed before combustion takes place.
3. Oxy-Fuel Combustion: The first major difference here is the fact that the fuel is burned in oxygen not in air. The flue gas consists of mainly carbon dioxide and water vapour, the latter of which is condensed through cooling. The result is an almost pure carbon dioxide stream that can be transported to the sequestration site and stored.
After capturing the carbon dioxide the same needs to be transported to a location were it can be trapped and stored to undo its bad effects to the environment. This is mainly done using the pipeline which is the cheapest source of transport.
Carbon Dioxide Storage:
Carbon Dioxide can be stored in various forms like:
1. In gaseous form in deep geological formations. This method involves injecting the CO2 in the deep geological formations.
2. Another proposed form of carbon storage is in the oceans. Several approaches have been proposed:
a. ‘dissolution’ injects CO2 by ship or pipeline into the water column at depths of 1000 m or more, and the CO2 subsequently dissolves.
b. ‘lake’ deposits CO2 directly onto the sea floor at depths greater than 3000 m, where CO2 is denser than
water and is expected to form a ‘lake’ that would delay dissolution of CO2 into the environment.
c. convert the CO2 to bicarbonates (using limestone)
d. Store the CO2 in solid clathrate hydrates already existing on the ocean floor, or growing more solid clathrate.
3. Mineral Storage is another option that is being exercised. This is done by reacting CO2 with naturally occurring Mg and Ca.
Recently oil major like Shell is also considering the use of CCS projects and according to them it could help reduction of pollution level by 40%. But the current challenges that are coming as hurdles in the mass implementation of CCS are the cost factor which is becoming prohibitive at this moment and also scare of leakage which can turn the whole CCS implementation upside down by itself becoming a source of pollution. Current cost estimates suggest that CCS project might cost Shell around $2 billion for each million tons per year of emissions.
Given all this and based on expert views it can be said that although the CCS technology looks to be very extravagant at this juncture but it surely does have the potential to become a big technology which can reshape the world and its environment and trap the growing beast forever!!! But we also need to keep it in mind that this is a beast that we have grown by our neglect and our self centred development plans. A bit of concious effort from each one of us can ensure that never such a beast arises!!