It is the procedure of capturing Carbon Dioxide (CO2) even before entering the atmosphere, transferring it, and depositing it for decades or millennia (carbon sequestration). CO2 is usually gathered from big point sources like coal fired power plants, chemical industries, and biomass – based power plants, and then stored underground in geological formations. Countries like Algeria, Australia, Canada, China, Germany, Netherlands, Norway, United Arab Emirates, United Kingdom, and United States of America have already some ongoing projects in this field.
The topic has a high probability of being asked as a Current Affairs Question and as Environment and Ecology Questions in IAS Prelims and Mains.
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About Carbon Capture and Sequestration
The goal is to eliminate CO2 emissions from heavy industry in order to mitigate the consequences of climate change. CCS (Carbon Capture and Sequestration) is used to capture around one thousandth of worldwide CO2 emissions by the year of 2020. The majority of these projects are industrial in nature.
The stored material has a minimum 65% carbon composition and the gas is solidified before sequestration.
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Carbon Capture Techniques
Point sources, such as huge carbon based energy facilities, factories with substantial CO2 emissions, such as cement manufacturing, steel production, natural gas processing, synthetic fuel plants, and fossil fuel based hydrogen generation plants, are the most cost effective places to capture CO2. It can be extracted from the air as well, however the lower CO2 concentrations in the atmosphere relative to combustion sources complicates the engineering and makes the whole thing more costly.
This phase can be accomplished using one of the below three technologies:
- Post Combustion Capture: CO2 is isolated when fossil fuels are burnt, and this process is employed in fossil fuel-based power plants. CO2 is recovered from flue gases at power plants and other point sources. In this form, power facilities may be upgraded to integrate CCS technology.
- Pre Combustion Capture: It is mainly used in fertiliser, chemical, and gaseous fuel (H2, CH4) manufacturing, as well as power generation. The fossil fuel is partially oxidised in these applications, such as in a gasifier. The CO in the resultant syngas combines with the steam, resulting in CO2 and H2. A sufficiently clean exhaust stream can be used to collect the CO2. The CO2 is eliminated before burning, thus the H2 may be utilised as a fuel.
- Oxy Fuel Combustion: Instead of air, the fuel is burnt in pure oxygen. CO2 and water vapour make up the majority of the flue gas, with the latter condensing as it cools. As a result, the CO2 stream is nearly pure. “Zero emission” cycles are used to describe power plant operations that use oxy fuel combustion.
Carbon Separation Technologies
A variety of different technologies are employed to separate the carbon from the resultant gas stream, some of them are:
- Calcium Looping
- Chemical Looping Combustion
- Multiphase Absorption
- Oxy fuel Combustion
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Carbon Transport Methods
CO2 must be transported to suitable storage sites after being captured. Pipelines and ships are the most cost effective modes of transportation.
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Carbon Sequestration Methods
Gaseous form of storage in underground geological formations (including brine formations and depleted gas fields) and solid storage via interaction of CO2 with metal oxides to generate stable carbonates are the two options for long term storage.
Geo sequestration entails pumping CO2 into deep geological formations, usually in supercritical form. Alternatives include saline filled basalt formations, unmineable coal seams, saline formations, oil fields, and gas fields.
Fact: Supercritical Fluid (SCF) is any material at a temperature and pressure above its critical point, where distinct liquid and gas phases don’t really exist, but below the pressure necessary to compress it into a solid. It may effuse like a gas through porous solids, bypassing the mass transfer barriers that hinder liquid flow through similar materials.
Enhanced Oil Recovery
CO2 is periodically pumped into an oil field as an increased oil recovery technology, however it is not carbon neutral because CO2 is emitted when the oil is burnt.
CO2 can be delivered directly to algae or bacteria that can decompose it. Clostridium thermocellum, a CO2 metabolising bacteria, would be optimal in this process.
CO2 can react exothermically with metal oxides, resulting in stable carbonates (e.g. magnesite, calcite). CO2 to stone is a natural process that happens over many years and accounts for much of the surface limestone. One such mineral oxide is Olivine. With a catalyst, or by raising temperatures and/or pressures, or via mineral pre-treatment, the reaction rate can be increased.
Forest trees act as the best natural mechanism to capture and store carbon dioxide post its release in the atmosphere. Plants store carbon in them as well in the soil, in a significantly less concentrated form than artificial ways which has its own advantages. Forest cover can be increased at lesser cost for this purpose.
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Concerns over Artificial Ways of Carbon Capture and Sequestration
- Cost is the one of the most important factors in this process and economically viable solutions aren’t very effective.
- Leakage hazard is the most unpredictable one. Long term geological states are hard to predict and chances of natural geological forces creating leak points in the storage area are very high. Sudden high amounts of carbon leakage would be difficult to tackle with in future and would create adverse weather conditions among other possible consequences.
- The technology creates a justification for continued usage of fossil fuels.
- Using the ocean for storage would increase its acidification thereby harming the aquatic life; it was therefore banned under the London and OSPAR (Convention for the Protection of the Marine Environment of the North-East Atlantic) conventions.
- A few projects have failed in successfully achieving the goal, the prominent one among them is the FutureGen program.
Advantages of Artificial Ways of Carbon Capture and Sequestration
- The process would help dealing with the current carbon emission from various critical sources until we transition to a non fossil fuel dependent economy.
- It would create new sectors of employment generation.
- It could help tackle the need of the countries to comply with their Intended Nationally Determined Contributions to deal with Climate Change.
- Continued research and development might discover new and better ways/technology for the purpose.
Fact: Intended Nationally Determined Contributions is part of the United Nations Framework Convention on Climate Change (UNFCCC).
- ANICA – Advanced Indirectly Heated Carbonate Looping Process: It is concentrating on the development of cost-effective carbon capture technologies for lime and cement industries, which account for 5% of global anthropogenic carbon dioxide emissions.
- Port of Rotterdam CCUS Backbone Initiative: The Port of Rotterdam CCUS Backbone Program aims to create a “backbone” of common CCS infrastructures for enterprises in the Port of Rotterdam area which is in the Netherlands.
- Climeworks Direct Air Capture Plant and CarbFix2 Project: In Zürich, Switzerland, Climeworks established the first commercial direct air capture facility. Their method entails extracting CO2 straight from the atmosphere using a patented filter, separating the collected CO2 at high temperatures, and then transferring it as fertiliser to a neighbouring greenhouse. The Climeworks factory is located near a waste recovery facility, which uses its excess heat to power it.
- OPEN100: The Energy Impact Center (EIC) has released the world’s first open-source nuclear power plant deployment design. The Energy Impact Center and OPEN100 want to turn back the clock on climate change by the year 2040, and they think nuclear power is the only viable energy source for CCS without emitting additional CO2.
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