Impact of Carbon Dioxide Capturing and Storage on Climate Change
With the global temperature steadily increasing and climate change becoming more visible, humankind sets out to find a solution for this impending problem. In the recent years, scientists introduced a new technology, carbon dioxide capturing and storage, with the aim of reducing negative impact of rising carbon dioxide levels. Carbon dioxide capturing and storage, also known as CCS, is the process in which carbon dioxide is collected and stored inside a geographical formation to lessen its impact on the environment. CCS mainly uses three techniques in the collection process: post-combustion collection, pre-combustion, and oxyfuel. Post combustion targets CO2 emissions from power plants, which contribute to approximately 40% of total CO2 emissions (Fayyaz et al., 2018).
The process targets flue gas emitted from combustion in the plants, adding chemicals to the gasses to extract CO2. Some chemicals most commonly used are amines, which react with CO2 in the flue gases and forms water soluble compounds, and soluble carbonate, which react with CO2 to form bicarbonate. Pre-combustion collects CO2 before burning of the fuel by first gassing coal with oxygen and added steam. The mixture is processed via a shift converter, which converts CO to CO2 and H2. CO2 from this process is captured, while the hydrogen can be used to produce electricity through combustion. The last method of carbon dioxide capturing is oxy-combustion, where combustion takes place in a nearly pure oxygen environment. This results in a combination of CO2 and water vapour, which can then be separated and collected through condensation.
After collection processes, CO2 is then transported and stored in geological sites such as oil fields or gas fields (Figueroa et al., 2018). CO2 injected into oil fields additionally increase oil recovery rate, helping offset the capture and storage process costs. According to research, implementation of CCS projects is projected to restrict global average temperature increase of up to 2 celsius (Anwar et al., 201). As of April 2019, Global CCS Institute reports 44 large-scale CSS facilities. Some facilities are under construction and development, while some are operational. Majority of the facilities are located in Canada, United States of America, Western Europe, China, and Australia (“Facilities Database”, 2019).
Four specific CCS facilities, Sleipner, Campos Basin, In Salah, and Petra Nova were examined. The first facility, Sleipner, is located in Norway. The project began in 1996, and is the world’s first offshore CCS project. Carbon dioxide is first extracted from flue gas from power plants and subsequently injected into the Utsira saline aquifer below the ocean floor. The large size of the geological reservoir allows storage of over 600 billion tonnes of CO2. Furthermore, the remote location of the site increases the overall safety of the project and the probability that CO2 stays safely in the storage area (Furre et al., 2017). Campos Basin, the second CCS site, is located in Brazil. 17 of the total 50 fields were assessed and indicated approximately 950 million tons of total storage capacity. Additionally, injection of CO2 would benefit the matured oil fields through increased oil recovery rates. An estimation of costs was created for CO2 storage in Campos Basin’s oil fields, and results indicate relatively low storage costs of approximately 4 €/t CO2, excluding capture and transport costs. The low price increases the feasibility of carbon dioxide capturing as a main climate change reversing technology (Rockett et al., 2013). The Algerian-based In Salah CO2 Storage Project is an onshore CCS project.
The project first removes CO2 from steam generated by gas production of various gas fields via a central gas processing facility. Then, the CO2 compound is condensed, transported, and stored underground in the Krechba field. The In Salah project began in 2004, and has since then stored over 3.8 million tons of CO2 under the Earth’s surface (Ringrose et al, 2013). The Petra Nova project is based in southern United States of America and began operating in December 2016. It uses a post-combustion method to capture over 90% of emitted CO2 from coal-fired power plants. On a daily basis, the project captures approximately 5000 metric tons of CO2. Within the first year of operation, the plant captured more than 1,000,000 tons of carbon dioxide. An 80-mile pipeline was constructed from the power plant location to the West Ranch oil field, carrying the captured carbon dioxide to the injection site. Through CO2 injection, oil production of the field was increased by 1,300% in the first 10 months (“Petra Nova”, 2018).
In addition to slowing down climate change through decreasing the CO2 emission amount, CO2 capturing technology also proves to be economically beneficial through increased oil production rates of storage sites. These four CCS projects successfully captured and stored CO2 gases in various amounts through different processes. Sleipner project stores CO2 under the ocean bed and In Salah under the Earth’s surface, while Campos Basin and Petra Nova re-injects CO2 into oil fields to boost production rates. These projects in North and South America, Europe, and Africa indicate that carbon dioxide capturing is not restricted to only certain regions, but is able to be adapted and implemented successfully according to geography.
One of the largest concerns over CCS is reliability of its CO2 storage. Keller et al. (2018) indicates questions and concerns over whether storage facilities will endure over long periods of time, and whether the stored CO2 compounds will be able to escape and return to the atmosphere. Due to the exploratory nature of this technology, there was no definite answer over these concerns as of now. With no quantifiable knowledge of these risks, traditional techniques of risk assessment were not applicable and thus increases safety uncertainty levels of these projects. Additionally, levels of public acceptance or concern over the CCS project are factored into account. Although its impact is unclear, public risk perception vary among different countries. Another uncertainty of CCS is the financial feasibility of the technology.
Current costs of development are high, and even if the cost-benefit ratio of such project turns out to be positive, it does not necessarily translate to a better investment than other equally environmentally-friendly alternatives. These financial concerns determine the willingness to invest of policy-makers and investors in CCS technology. Suebsiri et al. (2011) raises further concern over CCS and the significantly decreased efficiency of a power plant through implementation of the technology. To compensate for lost energy, additional resources such as coal in a coal-fired power plant must be used. Furthermore, the entire process of CO2 capturing and storing requires additional energy to be used whether in transporting the captured compound or storing in oil fields or underground. This attributes to an increase in emission and waste generation, and is therefore counterproductive. Various options of carbon dioxide storage do not yield the same level of efficiency. Of all the currently available methods of storage, enhanced oil recovery as a storage method has shown to be the most efficient due to its oil regeneration.
On the other hand, CO2 storage underground or in deep saline aquifers are not as efficient as they do not produce any positive side effects. Lastly, Zoback & Gorelick (2012) found compelling evidence that the injection of CO2 into the subsurface holds the potential of causing earthquakes. These earthquakes could be triggered from increased porous pressure when substance is injected into deep wells, in the case of CCS, oil fields. This pressure increase reduces frictional resistance of a fault slip, which in turn releases elastic energy stored in rocks around the area in the form of earthquakes. The first documentation of this effect was observed in 1960s Denver, Colorado. Multiple earthquakes were triggered by a 3-kilometers-deep well injection near Rocky Mountain Arsenal. Although no reports of earthquakes due to CO2 storage have been reported thus far, the earthquakes caused by injection of the compound is still possible.
Although the CCS process holds many risks, it has been successful in various locations examined in this paper. Taking note from the successes, many countries are considering CCS as the solution to combating climate change. Kuwait, for example, carried out a CO2 storage feasibility study to determine probability of implementation in the future (Neele et al., 2017). India, a country heavily dependent on coal as an energy source, is also in the process of developing its own CCS system (Garg & Shukla, 2009). Implementation of additional CCS facilities around the globe is expected to decrease CO2 emissions, which would in turn reduce the negative impacts of CO2 on climate change. Although this is a positive effect on the environment, CCS cannot be taken as the perfect solution to the changing climate as the effects of large-scale carbon capturing and storage have yet to be seen and perhaps a more complete solution to climate change would appear in the future.
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