**1.2 Carbon capture and storage (CCS) – A way to mitigate climate change**

Carbon capture and storage (CCS), also known as carbon capture and geological storage (CCGS), is a process to mitigate climate change by which the CO2 generated by concentrated industrial activities, such as thermoelectric plants, fossil fuel extraction and refining facilities and other industrial processes that rely on combustion, is captured and stored in geological formations.

One may question the importance of using CCGS to reduce CO2 emissions since nowadays vehicles are the main contributors to the greenhouse effect. Nevertheless, vehicles are becoming cleaner through better efficiency and the shift to different engines and fuels, such as electric cars. While the electricity used by these cars may be generated by a power plant burning coal, considered a "dirty" source, the CO2 emitted in concentrated form at this plant can be sequestered while the capture of that emitted in dispersed form by thousands of vehicles with internal combustion engines is economically unfeasible.

The study by the International Energy Agency (IEA, 2010b) shows that the reduction of GHG emissions can only be attained by adopting a series of technological measures. As seen in Figure 3, by the lines traced out to 2050, the IEA believes that if we continue emitting GHGs indiscriminately, global emissions can reach 57 GtCO2 a year over that horizon. But with an intense effort to reduce emissions, through a mixture of CCGS, carbon sequestration by biomass, increased use of renewable energies such as nuclear and enhanced energy efficiency, the world can reduce its emissions to 14 GtCO2 a year.

captured from the atmosphere by the plants from which it is produced. However, it is necessary to perform a complete life cycle analysis of the production of renewable fuels such as ethanol. Practices such as burning off litter in cane fields to facilitate harvesting and the use of farm machinery and trucks that burn fossil fuels diminish the comparative advantage, not to mention social questions. Besides this, the use of renewable energy from biofuels in general competes with land use to produce food, to meet the exploding global demand caused by the inclusion in the consumer market of lower classes from densely populated

emerging countries like China and India.

stored in geological formations.

Fig. 2. World Primary Energy Supply (TEPS) - Source: IEA (2010a)

vehicles with internal combustion engines is economically unfeasible.

efficiency, the world can reduce its emissions to 14 GtCO2 a year.

**1.2 Carbon capture and storage (CCS) – A way to mitigate climate change** 

Carbon capture and storage (CCS), also known as carbon capture and geological storage (CCGS), is a process to mitigate climate change by which the CO2 generated by concentrated industrial activities, such as thermoelectric plants, fossil fuel extraction and refining facilities and other industrial processes that rely on combustion, is captured and

One may question the importance of using CCGS to reduce CO2 emissions since nowadays vehicles are the main contributors to the greenhouse effect. Nevertheless, vehicles are becoming cleaner through better efficiency and the shift to different engines and fuels, such as electric cars. While the electricity used by these cars may be generated by a power plant burning coal, considered a "dirty" source, the CO2 emitted in concentrated form at this plant can be sequestered while the capture of that emitted in dispersed form by thousands of

The study by the International Energy Agency (IEA, 2010b) shows that the reduction of GHG emissions can only be attained by adopting a series of technological measures. As seen in Figure 3, by the lines traced out to 2050, the IEA believes that if we continue emitting GHGs indiscriminately, global emissions can reach 57 GtCO2 a year over that horizon. But with an intense effort to reduce emissions, through a mixture of CCGS, carbon sequestration by biomass, increased use of renewable energies such as nuclear and enhanced energy

Fig. 3. Technologies for reducing CO2 emissions - Source: IEA (2010b)

The IEA together with the CSLF (Carbon Sequestration Leadership Forum) prepared a report called "Carbon Capture and Storage – Progress and Next Steps" (IEA & CSLF, 2010) for the G8 summit meeting held in Muskoka, Canada, on June 25-26, 2010. This report lists 80 CCGS projects that fit under a series of criteria, among them the capture of over 500 MtCO2 per year and being in operation between 2015 and 2020. Of these 80 projects, 9 are already in operation and the remaining 71 are in one of the four phases (identification, assessment, definition or execution) that precede operation. Among these 80 projects, 73 are located in developed countries, 4 are in China, 2 in the Middle East and 1 in Africa.

In a graph, shown in Figure 4, the report predicts growth to as many as 3,400 projects in 2050, of which 65% will be located in countries not belonging to the Organization for Economic Cooperation and Development (OECD). These 3,400 projects will be responsible for capturing some 10 GtCO2 annually, representing a yearly average of 3 MtCO2 per project.

Fig. 4. Global deployment of CCGS 2010-2050 by region – Source: IEA & CSLF (2010)

Carbon Capture and Storage – Technologies and Risk Management 243

Today there are a series of CO2 separation methods already developed or under

Various factors influence the choice among these separation methods: available space for allocation and consumption of energy by the separation plant, concentration of CO2 in the gases to be processed, pressure of these gases, level of purity and percentage of CO2 separation.

Chemical absorption is a widely used process with a series of pilot plants distributed around the world. The oldest commercial CCGS plant is located in Sleipner, Norway and

The process entails using a solvent, normally an amine, which chemically reacts with CO2, forming a compound. As shown in Figure 6, this reaction occurs in an absorption tower, whose size basically depends on the flow of the flue gas from the industrial process. The compound thus formed is transferred to the regeneration unit where its temperature is raised to release the CO2. The solvent free of CO2 then returns to the absorption tower to

One example of commercial chemical absorption processes is the chilled ammonia process (CAP), which was developed by Alstom Power and is utilized in pilot plants to capture carbon developed by that company in partnership with American electric utilities. The first pilot plant, with generating capacity of 1.7 Mwatts, was the Pleasant Prairie thermoelectric plant of WE Energies in Wisconsin. The second was the Mountaineer thermoelectric plant, with capacity of 20 Mwatts, owned by American Electric Power in West Virginia (Sherrick et al., 2009). This plant operated from October 2009 to May 2011, for a total of over 6,500 hours,

development, among them the more used are:

has used this process since 1996 (Solomon, 2007).

Fig. 6. Absorption and regeneration processes

 Chemical absorption; Physical adsorption; Oxy-combustion.

**2.1.1 Chemical absorption** 

repeat the cycle.
