Can you provide an explanation behind capturing and using carbon dioxide?
Carbon dioxide cannot be seen, it is odorless too but is has severe consequences, If it crosses the .03% limit in the atmospheric ecosystem. The so-called atmospheric balance is quite crucial in the sustainability of planet Earth. Carbon dioxide acts as an outer cover. The ozone layer, present in stratosphere, is responsible for two important things. First it stops harmful ultraviolet rays to pass through and reach the earth surface. Second it traps heat meaning it does not allow all heat to go away when there is no sunlight. In other words ozone layer is responsible for maintaining a steady balanced temperature, when there is no sunlight, means during the night. What exactly excess carbon dioxide in atmosphere does is, it starts making a special layer in lower stratosphere- below the already present ozone layer. This follows trapping of heat radiation close to the Earth's surface. The earth starts getting warmer. The consequences could be melting of ice, rise of sea level. This Global Warming can lead to total imbalance in the earth's environment. So it is important to minimize sources of carbon dioxide like burning fossil fuels for power plants, petrol and diesel cars, industry producing the carbon dioxide gas etc. At the same time it is important to capture excess carbon dioxide and store it in usable form. In textbook language the act of capturing and using carbon dioxide is known as carbon capture and sequestration or carbon dioxide capture or storage (CCS). Carbon capture and storage (CCS) is most commonly defined as the capture of CO2 from a region where it is excessively present like industrial areas, industry, coal-based power plants, and cement production units. This is followed by its transportation and its storage in geological formations. CCS is envisaged as one of the possible technologies which can alter the affects of excess carbon dioxide in atmosphere and contribute to cost-effective emission reductions, which is the need of the hour. CCS is an effective way to control climate change.
Based on our method and direction in carrying out carbon capture and sequestration (CCS) it can be studied in many steps or sub steps.
1. Pre combustion carbon capture- In this Carbon dioxide is captured before the fossil fuel, responsible for its production is burned, which means the CO2 is captured before it is polluted by other gases like sulfur, water vapor, hydrocarbons etc. The carbon dioxide is separated from coal itself, before the coal is used in power plants or cement production units.
2. In Post-combustion carbon capture, the carbon dioxide is captured after the fossil fuels like coal is burned. The burning results in flue gases' mixture which comprises of CO2, water vapor, sulfur oxides, hydrocarbons etc , CO2 is separated and captured from the flue gases that is obtained as bi-products in the combustion of fossil fuels like coal.
3. There is another way -oxy-fuel combustion carbon capture. In this, fuel is burned in presence of oxygen which gives a gas mixture consisting mainly steam and CO2 as bi-products, together with huge amount of heat. The steam and carbon dioxide are separated by fractional distillation process - cooling and compressing the gas stream over a range of temperature wherein both gets separated due to their difference in boiling points.
There are many other process for CCS which are as follows;
Catalysis - With the help of catalysis we convert CO2 to valuable products. Catalysis refers to the development and use of effective, suitable and cheap catalysts. It is important again to consider the supply chain for catalysts. Many catalysts used in a research environment often sourced from geo-politically unstable regions like Africa or middle-east where lands are mineral-rich. It is of paramount importance to develop such catalysts that are available in large quantities and are stable under the reaction conditions and can be used extensively for the CCS process anywhere in the world so that they can be readily available and recycled over prolonged periods. Furthermore, the catalysts need to be robust and supported on a solid matrix to aid the process. Homogeneous catalysts, heterogeneous catalysts or any other can be used for this. At the end whatever the process or type of catalysts, the objective should be to capture as much as carbon dioxide from the source in a inexpensive or cheap budget.
Artificial Photosynthesis - the Considerable effort is being made to copy biological systems and processes and make their equivalents. Our environment has such facilities gifted by god wherein automatic capture of CO2 takes place. But, these are complex-catalysts which involve multiple reactions, processes, pathways. Recent studies have reported some success in individual photo- or electro-catalytic efforts but this is an area which stores considerable promise for future exploitation and research.
Photo-catalysis may be regarded as an extension to artificial photosynthesis, where the range of chemical products is extended beyond carbohydrates and oxygen through the use of a variety of simple or unique catalysts. In its most efficient cases photo-catalysis would use natural sunlight to do the process. However, by careful application of catalysts, it becomes possible to tune the catalyst and reaction to different wavelengths to gain maximum efficiency. This would result the conversion of renewable electrical energy into the light but this would ultimately allow energy to be stored in a form which can be used as per wish in future.
Electrochemical Reduction - An Electrochemical reduction of CO2 uses electric current to reduce carbon dioxide to other useful hydrocarbons which can be used in laboratory or in industry. Examples of such hydrocarbons are methyl alcohol, methane, acetyl acetate etc.
In a nutshell, it can be said that storing or capturing carbon dioxide is a great idea! But do we have resources like space, infrastructure and available land to store it underground? Therefore it is of utmost importance that this CCS should be carried out with the full cooperation of all countries in the world as we divided the earth by boundaries but actually, we are inter-connected, we have one atmosphere, we have one air -'a hole here in ozone will affect the part there in the earth.'