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FOSSIL FUEL RESERVES AND DEPLETION
In 1955, Farrington Daniels, professor of chemistry at the University of Wisconsin from 1920 to 1959 and a pioneer in solar energy applications, stated (Daniels and Duffle, 1955):
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-s — POPULATION, BILLION EJ/YEAR
FIGURE 1.7 World population and consumption of fossil fuels, 1860—1990.
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EJ/YEAR GJ/CAPITA-YEAR
FIGURE 1.8 World consumption of coal, oil, and natural gas, 1860-1990.
. . . our fuels were produced millions of years ago and through geological accident preserved for us in the form of coal, oil, and gas. These are essentially irreplaceable, yet we are using them up at a rapid rate. Although exhaustion of our fossil fuels is not imminent, it is inevitable.
Few people paid any attention to such remarks at that time. Many regarded them as the usual gloom-and-doom commentary of the day.
Between 1860 and 1990, the world’s population and the consumption of fossil fuels per capita sequentially doubled almost three times and four times, but over the same period of years, global consumption of fossil fuels passed through six sequential doubling cycles. The doubling times for global fossil fuel consumption, population, and fossil fuel consumption per capita in the mid-1990s were approximately 25, 35, and 50 years, respectively (Table 1.4). These trends suggest several features of a society whose gradual and then rapid industrialization has depended on the availability of energy and fuels, namely that fossil fuel consumption is disproportionately increasing as more and more of the world’s population is industrialized despite the large improvements in the efficiency of energy utilization over the past 50 years. Human activity and interactions at all levels require the acquisition and consumption of energy and fuels, no matter what the living standards are. It is simply a matter of increasing population and the apparent preference for energy-rich, high-quality fossil fuels. Questions of where recoverable fossil fuel deposits are located and the size of these deposits are obvious. How long will it be, for example, before the world’s supplies of petroleum crude oils begin to permanently fall short of demand?
Energy specialists and reservoir engineers in the United States and several other countries use “proved reserves” to predict the amounts of coal, oil, and natural gas that can be produced and marketed. Proved reserves are defined
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TABLE 1.4 Approximate Times in Years for Sequential Doubling of World Population, Fossil Fuel Consumption, and Fossil Fuel Consumption Per Capita from 1860 to 1990 Fossil fuel Fossil fuel Population consumption consumption/capita
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as the estimated portion of a natural fossil fuel deposit that is projected from analysis of geological and engineering data with a reasonably high degree of certainty, usually a combination of experimental field data, modeling, and experience, to be economically recoverable in future years under existing economic and operating conditions. Unfortunately, there are no international standards for estimating or defining reserves, and there are many problems associated with development of accurate proved reserves figures. They are, however, the best running accounting method available today to project fossil energy supplies.
Examination of the world’s proved reserves of coal, crude oil, and natural gas and their regional locations shows that well over half of the world’s crude oil and natural gas supplies are located in the Middle East and the former Soviet Union, while North America, the Far East, and the former Soviet Union have over 70% of the coal reserves (Table 1.5, Fig. 1.9).
Intuitively, these data suggest that countries in those regions having large amounts of specific proved fossil fuel reserves would tend, because of proximity to these resources, to consume more of the indigenous fossil fuels than those
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TABLE 1.5 Global Proved Coal, Oil, and Natural Gas Reserves by Region’1
The coal data are for the end of 1990 (World Energy Council, 1992). The oil and natural gas data are for January 1, 1993 (Gulf Publishing Company, 1993). The reserves data for coal, oil, and natural gas are indicated in tons, barrels, and cubic feet, respectively, as published and were not converted to SI units. The world average heating values for subbituminous, bituminous, and anthracite coals; lignite; oil; and natural gas are assumed to be 27.9 GJ/t (24 million Btu/ton), 16.3 GJ/t (14 million Btu/ton), 5.9 GJ/bbl (5.6 million Btu/bbl), and 39.3 MJ/m3(n) (1000 Btu/ft3), respectively. The result of multiplying the amount of reserves by the world average heating value may not equal the EJs in this table because of the variation in fuel value of specific reserves within a given fuel type. The sums of individual figures may not equal the totals because of rounding. |
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TOTAL = 1039 BILLION METRIC TONNES
WESTERN EUROPE 2%
FAR EAST & OCEANIA 6%
TOTAL = 163.7 BILLION CUBIC METERS
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FORMER U. S.S. R. 42%
MIDDLE EAST 28%
TOTAL = 136.4 TRILLION CUBIC METERS
that are not within their confines. This is often the case, as illustrated by some of the data in Table 1.3 for the world’s 10 highest energy-consuming countries. There are many exceptions. The proved reserves-to-annual consumption ratios calculated from the proved reserves and annual consumption data for coal, crude oil, and natural gas for a few selected countries illustrate some of these exceptions (Table 1.6). In theory, these ratios indicate the number of years until the proved reserves of a particular resource are exhausted, assuming no imports of fossil fuels, a constant rate of fuel consumption, and no further discoveries of economically recoverable coal, oil, or natural gas. According to these data, a 258-year supply of coal, the world’s largest energy resource of the three conventional fossil fuels, is available in the United States, whereas oil and natural gas have much shorter depletion times. Nevertheless, coal currently contributes less to energy demand than either oil or natural gas. In contrast, other countries such as China, Germany, and India have large proved reserves of coal and consume relatively large amounts, while Saudi Arabia has essentially no proved coal reserves and consumes none. Worldwide, coal consumption grew at an annual rate of 1.4% between 1980 and 1993 and accounted for about 25% of the world’s total energy use in 1993, so it continues to be an important energy resource.
Oil is clearly a much smaller fossil energy resource than coal. Because of its intrinsic properties such as high energy density, ease of transport, storage, and conversion to storable liquid fuels, and an existing infrastructure that facilitates worldwide distribution of refined products to the consumer, it is the fossil fuel of choice for the manufacture of motor fuels. Some countries, such as Japan, that have little or no proved reserves of oil consume relatively large quantities and are therefore strongly dependent on imports to meet demand. Some countries, such as Saudi Arabia, have an abundance of proved oil reserves and supply their own demands as well as a large fraction of the world’s markets. Global consumption of oil increased by 18.4 EJ between 1983 and 1992 at an annual rate of growth of 1.5% (U. S. Dept, of Energy, 1994). Motor fuels from oil are expected to remain the dominant international transportation fuel for the foreseeable future. Other projections indicate that global consumption of oil will exhibit a growth rate of nearly 2% per year up to 2015 (U. S. Dept, of Energy, 1996). While natural gas and renewables are making inroads into the energy markets of OECD (Organization for Economic Cooperation and Development) nations, leading to a decline in oil’s share in those
FIGURE 1.9 (a) World coal reserves by region, December 31, 1990. (b) World oil reserves by region, January 1, 1993. (c) World natural gas reserves by region, January 1, 1993.
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TABLE 1.6 Proved Reserves-to-Annual Consumption Ratios for Fossil Fuels for Selected Countries and World”
“Data adapted from U. S. Department of Energy (1994). |
markets, its share is rising in the developing nations as transportation, industrial, and other uses for oil expand.
Natural gas is somewhat similar to oil in that it is a relatively clean-burning fuel compared to coal. Long-distance pipelines have been built in many developed and developing countries to deliver gas from the producing areas to large urban markets where it is delivered to the consumer via local gas distribution networks. In modern combined-cycle, cogeneration systems, it is generally the fossil fuel of choice for electric power production and stationary applications. Again, a correlation does not necessarily exist between the location of indigenous proved reserves in a given country and energy consumption in that country. Japan is an example of a country that has no natural gas reserves, yet consumes considerable natural gas that is transported to Japan from producing countries as liquefied natural gas (LNG) in large cryogenic tankers. Another example is the utilization of the large reserves of natural gas in Eastern Europe. Consumption is high in Eastern Europe, but high-pressure pipelines are used to transport natural gas from producing regions in Eastern Europe to Western Europe where proved reserves are small. Natural gas is the fastest-growing fossil fuel in the world’s energy mix. Its annual rate of growth in production was 3.7% from 1983 to 1992, and it contributed 22% to world energy demand in 1993.
A somewhat more quantitative estimate of depletion times for fossil fuels can be calculated under specific conditions using a simple model that accounts for proved reserves and growth rates in consumption (Appendix B). Application of this model to the consumption of global proved reserves of petroleum crude oils is presented here. Calculation of global depletion times eliminates the problem of accounting for imports and exports. The conditions assumed for these calculations are those for 1992. The world’s proved reserves are 6448 EJ, the annual consumption is 144 EJ, and the average annual growth rate in consumption of petroleum products is assumed to be a conservative 1.2%, which is projected by the U. S. Department of Energy to hold until 2010. Under these assumed conditions, the depletion time of the proved reserves of petroleum is 35 years, or the year 2027.
Current estimates of proved reserves do not represent the ultimate recoverable reserves because of ongoing oil exploration activities and new discoveries, which have generally been able to sustain proved reserves for several decades. For this reason, and because changing economic conditions and technical improvements affect the assessment of proved reserves and the economic recoverability of oil from lower-grade reserves and unconventional reserves of tar sands and oil shales, calculation of the depletion time for several multiples of the proved reserves is also of interest. The depletion time for five times the proved reserves (32,240 EJ) at the same consumption rate is 108 years, or the year 2100. The ultimate recoverable reserves are believed to be closer to two times the world’s proved reserves of oil and syncrudes (12,896 EJ) from unconventional sources (Institute of Gas Technology, 1989). Note that the depletion time of 108 years for five times the proved reserves is not a factor of five greater than that calculated for proved reserves of 6448 EJ because of the compounding effect of the growth rate in consumption of 1.2% per year; it is about three times greater. The changes in remaining reserves with time from these calculations are illustrated in Fig. 1.10.
Despite the facts that world trade in the international oil and natural gas markets is flourishing and there is little sign of a significant reduction in energy
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PERCENT REMAINING RESERVES
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RESERVES OF 6448 EJ FIVE TIMES RESERVES
BASELINE CONSUMPTION IN 1992 IS 144 EJ
FIGURE 1.10 Global depletion of petroleum reserves at annual consumption growth rate of 1.2%.
consumption, the limited data and simplified analysis presented here suggest that gradual depletion of oil and natural gas reserves can be expected to become a major problem by the middle of the twenty-first century. Without preparation and long-range planning to develop alternative fuels, particularly nonpolluting liquid motor fuels for large-scale worldwide distribution and clean-burning fuels for power production in stationary applications, energy and fuel shortages could become severe. The disruptions in energy and fuel supply and availability that occurred in the 1970s illustrate the potential impact on society. The oil marketing policies of the Organization of Petroleum Exporting Countries (OPEC) and the resulting First Oil Shock in 1973-74 had a lasting impact on the international oil markets and the energy policies of most industrialized nations. In 1973, Mideast light crude oil spot market prices rose to about $13 per barrel from a low of about $2 per barrel. The Second Oil Shock began in 1979 as a result of OPEC’s curtailment of production until spot Mideast oil prices peaked in early 1980 at $38.63 per barrel. Major policy changes and legislative actions occurred in many industrialized countries to try to counteract these conditions. The First Oil Shock resulted in a flurry of legislative activities and executive orders by the executive and legislative branches of the U. S. Government, for example, that affected literally all energy-related sectors. This was actually the beginning of national policies in many countries to develop new indigenous energy supplies. In the United States, the federal laws that have been enacted since the First and Second Oil Shocks have had a profound and continuing impact on all U. S. energy production and utilization. When it was realized that oil prices and availability could be manipulated or controlled to a significant extent by outside forces and how important these factors and their impact are for the U. S. economy, massive programs were undertaken to make the United States less dependent on imported oil. Other nations have taken similar actions. Many of these programs continue today.
A few words of caution are warranted in dealing with depletion times and the proved reserves of fossil fuels, that is, the possibility of new discoveries, the variability of depletion time, the effects of new technologies, and the uncertainty of predictions. Detailed assessment of the proved reserves-to — consumption ratios for oil and natural gas over the past several decades shows that although there has been a slight decline in the values of specific proved reserves reported by some sources, new additions to proved reserves have been able to sustain market demands over many years while the calculations indicated that depletion should have occurred in just a few years. The estimated depletion times calculated in the mid-1970s showed, for example, that the global reserves of natural gas should have been depleted by about 1995. Discovery of large new reserves capable of economic production, the development of significantly improved gas producing and processing methods, higher gas utilization efficiencies by end-use equipment, and lower actual annual growth rates in consumption than those predicted have all contributed to prolong depletion and the time of depletion. Basically, the estimates of the world’s total remaining recoverable reserves of oil and natural gas have been sustained and continue to keep pace with consumption. But given the extensive periods of time required to replenish finite supplies of fossil fuels, the earth is not an infinite source of these materials when considered in terms of world energy demand and population growth. Presuming Professor Daniels’ prediction that depletion of coal, oil, and natural gas is truly inevitable, it is still prudent to use these natural resources wisely. This will help conserve our valuable fossil fuels and extend the time when depletion and the unavoidable rise in energy prices and shortages occur and become a fact of life. The coupling of fossil fuel usage and environmental problems may eventually result in the equivalent of mandated conservation of fossil fuels.