Global GHG Emissions

ESTIMATION OF CO₂ STORAGE CAPACITY IN OIL AND GAS FORMATIONS

Introduction:

This chapter provides an introduction to Global Green House Gas (GHG) emissions, effects of Global warming, mitigation of global warming and the Sequestration technology.

Water vapor, carbon dioxide (CO2), methane (CH4) and ozone (O3) can be termed as major GHGs. GHGs normally have a natural origin in ecosystem, but because of industrialization, emissions of these gases increased by burning fossil fuels for energy production. Therefore, concentration of anthropogenic GHGs (human made emissions) has been increasing in the atmosphere, especially CO2.

Table 1 shows a list of the GHGs and the most recent concentration values compared with the values since pre-industrialization which is Pre-1750. The tropospheric concentrations of CO2 has increased by 35% from pre-industrial time values of 280 ppm to 375 ppm over the past 150 years and the increased concentration of Carbon Dioxide arises the degree of the greenhouse effect and the global warming issue.

Table 1: Current GHG Concentrations (Blasing and Jones), (Torrealba, 2006)

Carbon Dioxide is the most serious anthropogenic GHG and a major contributor to the global warming. CO₂ emission occurs generally from the burning of fossil fuels, such as those used for electric power generation, automobile engines and furnaces used in residential and commercial buildings and it continued an upward trend because fossil fuels are the dominant form of energy utilized in the world. It generally produced when carbon based fossil fuels are combusted as shown in equation (1):

-------------------- (1)

Figure 1 shows total CO₂emissions from per capita worldwide from 1950 to 2001.

Figure 1: Worldwide Total Carbon Dioxide Emissions per Capita 1950-2001 (Torrealba, 2006)

Figure 2: Global Fossil Carbon Emissions in Oil and Gas industries (http://www.boards.ie/vbulletin/showthread.php?p=56328129)

The above figure depicts the Carbon Emissions from oil and gas industries till 2004. According to International Energy Agency (IEA) total emissions from fossil fuel consumption and flaring of natural gas were 24 GtCO2 per year (6.6 GtC per year) in 2001(Intergovernmental Panel on Climate Change, 2005). Using several assumptions, (Intergovernmental Panel on Climate Change, 2005) in the third assessment built a set of scenarios of what might happen to emissions up to the year 2100 which yielded projected future CO2 emissions for the 21^st century lie in the range of 3,480 to 8,050 GtCO2 (950 to 2,200 GtC)

Global Warming Effect:

The global warming may cause disruption in the chemical composition and physical dynamics of Earth's atmosphere, leading to the distribution of heat or energy around atmosphere abnormally(Emre, 2006). Figure 3 expresses Global average temperature is going up compared to pre-industrialization era which suggests that earth is warming. The average temperature of 14.02 ˚ C in the 1970s rose to 14.26 ˚ C in the 1980s. In the 1990s it reached 14.40 ˚ C and during the first six years of this 21^st Century, global temperature has averaged 14.62 ˚ C (Goddard Institute for Space Studies, 2006). This rise in temperature is due to the buildup of GHGs in the atmosphere, particularly CO₂. The CO₂ that released into the atmosphere, traps heat that would otherwise escape back into space which can be realized by figure 3. Rising global temperatures are anticipated to increase sea level, and shift or switch precipitation and other local climate conditions which could change forests, crop yields, and water supplies. It could also jeopardize human health and many types of ecosystems (Enrique, 2003).

Figure 3: a) Average Global Temperature 1880-2005

b) Average Global Temperature with projection to 2100 (Goddard Institute for Space Studies, 2006)

Figure 4 demonstrates the comparison of the minimum sea ice concentration for the Arctic in 1979 and 2003 made by NASA. There is a decrease of 18% in arctic sea ice from 1979 to 2003 which suggests that decreasing ice concentrations are due to a significant increase in ocean warming. Decrease of the ice cap means more open water. This connotes greater absorption of solar energy and afterwards an increment of the rate of warming in the ocean, which of course tends to yield blistering rates of ice loss (Torrealba, 2006).

Figure 4: Comparison of Sea Ice Concentration in the Arctic from 1979 and 2003 (NASA, 2003)

Extenuation of Global Warming

With the creation of the UNFCC (United Nations Framework on Climate Change) in 1992, most of the nations agree on the severity of global warming, and signed a obligatory treaty for reducing greenhouse gas emissions known as the Kyoto Protocol in 11 December 1997 which required these countries to cut down greenhouse gas emissions to the level stipulated for each of them in the treaty. A total of 181 countries have validated the agreement as of May 2008

-------------- (2)

Major factors influencing CO2 emissions can be identified by using above equation (2) which shows that the level of CO2 emissions depend directly on the size of the human population, on the economic growth (GDP), on the energy intensity of the global economy, and on the emissions originates from the production and use of energy. At present, the population continues to rise and average energy use is also increasing (Intergovernmental Panel on Climate Change, 2005). So accomplishing heavy reductions in emissions will demand major changes in the energy use and emissions in this equation, if all other aspects remaining constant.

There is a broad variety of technological options to bring down net CO2 emissions, as will be talked about below. The targets for emission reduction will influence the extent to which each technique is used. The extent of utilization will also depend on factors such as cost, capacity, environmental impact, the rate at which the technology can be introduced, and social factors such as public acceptance (Intergovernmental Panel on Climate Change, 2005).

Figure 5: Mitigation Strategies (Emre, 2006)

The above figure 5 exemplifies the strategies suggested for mitigation of global warming which include (Emre, 2006):

Cut down energy use, conservation, energy efficiency
Switching from carbon-based fossil fuels to renewable secondary energy sources
CO₂ Sequestration

CO₂ Sequestration

It is also termed as carbon capture and storage (CCS) which is considered the most promising strategy for mitigating global warming, by capturing big volumes of CO2 from ample sources such as power plants and storing it away, for the long term, instead of releasing it into the atmosphere (Emre, 2006). There are mainly two types of CO2 sequestration.

Indirect CO2 sequestration which is also known as terrestrial sequestration involves of enhancing natural processes to remove CO2 from the air, which involves capturing the CO2 that has been relinquished to the atmosphere by fixing carbon in the soil or through intake by plants and by the application of land management practices directed towards modifying these natural sink abilities. Indirect sequestration offers inexpensive and environmentally safe approaches by using forest, grasslands, wetlands, and croplands, which do not need large-scale and potentially dearly changes to the energy infrastructure (Emre, 2006)
Direct CO2 sequestration, known as geologic CO2 sequestration consists of capturing CO2 at the source before it can be released to the atmosphere and its subsequent storage underground. Direct CO2 sequestration is envisaged as being integrated as a process in large stationary sources e.g. power plants, refineries and cement industry etc that first removes CO2 from fuel gas or exhaust gas at major point sources, and injects CO2 in safe storage sinks deep underground or deep in the ocean (Emre, 2006).

EMRE, O. (2006) Assessment of diffusive and convective mechanisms during carbon dioxide sequestration into deep saline aquifers. Graduate School of Natural and Applied Sciences. Middle East Technical University.

ENRIQUE, G. J. (2003) Fluid Dynamics of Carbon Dioxide Disposal into Saline Aquifers. Berekely, University of California.

GODDARD INSTITUTE FOR SPACE STUDIES (2006) Global Temperature Anomalies in .01 C. NASA Goddard Space Flight Center, Earth Sciences Directorate.

INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (2005) Carbon Dioxide Capture and Storage, Cambridge University Press.

NASA (2003) Recent Warming of Artic May Affect Woldwide Climate.

TORREALBA, M. A. T. (2006) A Strategy for Prevention of Sequestered CO2 Seepage from CBM Formations. Department of Petroleum and Natural Gas Engineering. Morgantown, West Virginia University.

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