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FIGURE 1.6 World oil production vs. time for various amounts of ultimate recoverable resource. (From Bartlett, A. A., Mathematical Geology, 32, 2002. With permission.)

If BP's estimations of oil reserves are correct, we may have already peaked in world oil production. If, however, estimates of the ultimate reserves (discovered and undiscovered) are used, we may expect the oil production to increase a little longer before it peaks. However, changing the total available reserves from 3X1012 bbl to 4X1012 bbl increases the predicted time of peak production by merely 11 years, from 2019 to 2030. There is no question that after the world peak is reached and oil production begins to drop, either alternative fuels will have to be supplied to make up the difference between demand and supply, or the cost of fuel will increase precipitously and create an unprecedented social and economic crisis for our entire transportation system.

The present trend of yearly increases in oil consumption, especially in China and India, shortens the window of opportunity for a managed transition to alternative fuels even further. Hence, irrespective of the actual amount of oil remaining in the ground, peak production will occur soon. Therefore, the need for starting to supplement oil as the primary transportation fuel is urgent because an orderly transition to develop petroleum substitutes will take time and careful planning.

1.4.2 Natural Gas

According to BP (2006), the total proven world natural gas reserves at the end of 2004 were 179.5 trillion m3. Considering the production rate of gas in 2004, with no increase in production thereafter, these reserves would last for 67 years. However, production of natural gas has been rising at an average rate of 2.5% over the past four years. If production continues to rise because of additional use of CNG for transportation and increased power production from natural gas, the reserves would last for fewer years. Of course, there could be additional new discoveries. However, even with additional discoveries, it is reasonable to expect that all the available natural gas resources may last from about 50 to 80 years, with a peak in production occurring much earlier.

1.4.3 Coal

Coal is the largest fossil resource available to us and the most problematic from an environmental standpoint. From all indications, coal use will continue to grow for power production around the world because of expected increases in China, India, Australia, and other countries. From an environmental point of view, this would be unsustainable unless advanced "clean coal technology" (CCT) with carbon sequestration is deployed.

Clean coal technology is based on an integrated gasification combined-cycle (IGCC) that converts coal to a gas that is used in a turbine to provide electricity with CO2 and pollutant removal before the fuel is burned (Hawkins, Lashof, and Williams 2006). According to R.C. Kelly, President and Chief Executive Officer of Minneapolis-based Xcel Energy, the company is about to build such a plant in Colorado, U.S.A. The plant will capture CO2 and inject it underground, possibly in depleted oil fields. According to Kelly, an IGCC plant can cost 20% more to build than a conventional coal plant, but is more efficient to operate (Associated Press 2006). According to an Australian study (Sadler 2004), no carbon capture and storage system is yet operating on a commercial scale, but may become an attractive technology to achieve atmospheric CO2 stabilization.

According to BP, the proven recoverable world coal resources were estimated to be 909 billion tons at the end of 2004 with a reserve to production ratio (R/P) of 164 years. The BP data also shows that coal use increased at an average rate of 6% from 2002 to 2005, the largest increase of all fossil resources. Because China and India are continuing to build new coal power plants, it is reasonable to assume that coal use will continue to increase for at least some years in the future. Therefore, the R/P ratio will decrease from the present value of 164 years. This R/P ratio will decrease even more rapidly when clean coal technologies such as coal gasification and liquification are utilized instead of direct combustion.

1.4.4 Summary of Fossil Fuel Reserves

Even though there are widely differing views and estimates of the ultimately recoverable resources of fossil fuels, it is fair to say that they may last for around 50-150 years with a peak in production occurring much earlier. However, a big concern is the climatic threat of additional carbon that will be released into the atmosphere. According to the estimates from the IEA, if the present shares of fossil fuels are maintained up to 2030 without any carbon sequestration, a cumulative amount of approximately 1000 gigatons of carbon will be released into the atmosphere (based on Figure 1.7). This is especially troublesome in view of the fact that the present total cumulative emissions of about 300 gigatons of carbon have already raised serious concerns about global climate change.

1.4.5 Nuclear Resources

Increased use of nuclear power presents the possibility of additional carbon-free energy use and its consequent benefit for the environment. However, there are significant concerns about nuclear waste and other environmental impacts, the security of the fuel and the waste, and the possibility of their diversion for weapon production.

FIGURE 1.7 World energy-related CO2 emissions by fuel. (Data and forecast from IEA, World Energy Outlook, IEA, Paris, 2004. With permission.)

According to the IAEA (2005) nuclear fission provided 16% of the electricity in the world in 2004, with a worldwide capacity of 368 GW. An additional 20 GW of nuclear power capacity was under construction during the same year. The IAEA also estimates that the worldwide nuclear power capacity will increase at an average rate of 0.5%-2.2% until 2030 (IAEA 2005). At present, uranium is used as the fissile material for nuclear power production. Thorium could also be used for nuclear fission; however, to date nobody has developed a commercial nuclear power plant based on thorium. Terrestrial deposits of both uranium and thorium are limited and concentrated in a few countries of the world. Estimates from the International Atomic Energy Agency (IAEA) and other sources show that the recoverable assured uranium reserves in the world are about 2.3 million tonnes to as much as 3.2 million tons (UNDP 2004). If additional estimated resources (not yet discovered) are also included, then the total resources become 5.1 million tons (UNDP 2004). Additionally, there are nonconventional uranium resources, such as sea water which contains about 3 parts per billion uranium and some phosphate deposits (more than half of them in Morocco) which contain about 100 parts per million uranium. These resources are potentially huge; however, their cost effective recovery is not certain.

Generating 1 TWh of electricity from nuclear fission requires approximately 22 tonnes of uranium (UNDP 2004). Based on the 2004 world capacity of 368 GWand an average annual growth rate of 2%, the present known uranium reserves of 2.3-3.2 million tonnes will last until 2030-2037. If all of the estimated (discovered and undiscovered) reserves of 5.1 million tonnes are considered, they will be used up by 2050. This estimate does not consider regeneration of spent fuel. At present, nuclear fuel regeneration is not allowed in the United States. However, that law could be changed in the future. Development of breeder reactors could increase the time period much further. Nuclear fusion could potentially provide a virtually inexhaustible energy supply; however, it is not expected to be commercially available in the foreseeable future.

1.4.6 Present Status and Potential of Renewable Energy (RE)

According to the data in Table 1.3, 13.3% of the world's total primary energy supply came from RE in 2003. However, almost 80% of the RE supply was from biomass (Figure 1.8), and in developing countries it is mostly converted by traditional open combustion, which is very inefficient. Because of its inefficient use, biomass resources presently supply only about 20% of what they could if converted by more efficient, already available technologies. As it stands, biomass provides only 11% of the world total primary energy, which is much less than its real potential. The total technologically sustainable biomass energy potential for the world is 3-4 TWe (UNDP 2004), which is more than the entire present global electrical generating capacity of about 3 TWe.

In 2003, shares of biomass and hydropower in the total primary energy mix of the world were about 11% and 2%, respectively. All of the other renewables, including solar thermal, solar PV, wind, geothermal, and ocean combined, provided only about 0.5% of the total primary energy. During the same year, biomass combined with hydroelectric resources provided more than 50% of all the primary

TABLE 1.3 2003 Fuel Shares in World Total Primary Energy Supply

Source

Share (%)

Oil

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