The Greening of Industrial Ecosystems. 1994.
Pp. 38-60. Washington, DC:
National Academy Press.
Energy and Industrial Ecology
HENRY R. LINDEN
This discussion of energy supply and use as a critical element of industrial ecology will focus primarily on fossil fuels, broadly classified as coal, oil, and natural gas. On the production side, the term "oil" generically refers to total crude oil, lease condensate, and natural gas liquids, and "coal" includes lignite and carbonization products. On the consumption side, the term "oil" includes liquid, solid, and normally gaseous products from the refining and processing of crude oil, lease condensate, and natural gas liquids. Most of these fuels are either burned directly or oxidized indirectly, such as the use of coal or petroleum coke in the production of metals. Only a relatively small percentage of the carbon and hydrogen content of these fuels is converted to products such as plastics, road-building materials, chemicals, fertilizers, and lubricants and is, therefore, not immediately released into the biosphere.
Several factors must be considered in assessing the future role of fossil fuels in meeting future energy needs. These include the dissipative material flows from fossil fuel use into the biosphere, the benefits and costs of energy abundance, trends in energy productivity, future energy technology and utilization trends, and the magnitude of fossil fuel reserves and resources relative to the rates of consumption for oil, natural gas, and Coal. These considerations suggest that three key issues will determine the future role of fossil fuels in meeting U.S. and global energy requirements:
Resource depletion: Can the further development of the global fossil fuel resource base yield sufficient quantities of oil, natural gas, and coal to permit an orderly transition to a sustainable, non-fossil-fuel-dependent global energy sys-
tern? Moreover, can this development maintain the cost-competitiveness of these fuels (absent the imposition of large carbon taxes) and their reliability as primary energy sources for a substantial share of the useful energy services required by the various end-use sectors over a long enough period—say, 100 years?
Global ecology versus human needs: Will the benefits of continued reliance on largely fossil-fuel-based energy abundance (as the engine of human economic and social progress and the foundation of improvements in the human environment) exceed the likely costs of any associated long-term ecological consequences in terms of their impact on biodiversity and other environmental values and their impact on future human well-being?
Developing versus developed world equity: Are the industrialized countries of the Western world and the Pacific Rim willing and able to help the developing countries and the nations of the former Soviet Bloc achieve eventual parity of economic and social well-being by providing them with the technical and financial assistance required to meet their energy needs in ways that are as efficient, cost-effective, and pollution-free as possible? Doing so would avoid the creation of regional and global 'environmental problems that could easily overwhelm any conceivable improvements in energy supply and use practices of the advanced industrial countries.
In brief, the major findings concerning these key issues are as follows:
Remaining fossil fuel resources—including petroleum liquids and natural gas—could meet the major share of global energy needs at costs competitive with nonfossil-fuel options during the likely transition period to a sustainable global energy system. This would be the expected outcome of continuing advances in fossil fuel extraction, conversion, transport, and end-use technologies that are enhanced by the large price and technology elasticities of energy supply and demand, and by the efficiency gains inherent in the ongoing global trend of electrification of stationary energy uses.
There is ample evidence that the benefits of increased energy consumption measured in terms of human well-being have outweighed any quantifiable environmental costs and are likely to do so for the foreseeable future. The substitution of commercial energy commodities and energy-intensive technologies for human and animal labor and primitive renewable energy forms has been a key factor in the evolution of modem democratic societies. It has reduced the need to exploit human labor pools as evidenced by the abolition of slavery, serfdom, and child labor and, more recently, the emancipation of women (an important step in population stabilization). Increased energy Use will also be essential in curing the developing world's economic and social ills, which mirror the conditions in much of the Western world before the Industrial Revolution. However, more than a trillion metric tons of additional carbon would be released into the biosphere over the next 100 years if fossil fuel use continues to be determined by least-cost energy service considerations. The long-term ecological consequences of that release
and its associated impacts on human well-being remain open questions that require early resolution.
It is evident that without assistance from advanced industrialized countries, the developing world's efforts to improve the economic and social well-being of its burgeoning populations will most likely rely on energy technologies and practices that are relatively inefficient and environmentally undesirable. Absent such assistance, developing countries will follow the historical pattern of growth rates of primary energy consumption that approach or even exceed the rates of economic growth. In contrast, in market economies with extensive energy supply, conversion, and distribution infrastructures and access to advanced technologies, primary energy consumption typically grows only about half as fast as gross domestic product (GDP). Moreover, the ratio of the primary energy consumption to GDP continues to decline with capital-intensive, cost-effective efficiency improvements and the ongoing electrification of energy systems.
In addition, in earlier stages of industrialization inherently capital-intensive measures to minimize environmental impacts of energy supply and use tend to be given low priority. The two most populous developing countries—India and the People's Republic of China—are largely coal-dependent, and the former Soviet Bloc has to overcome a legacy of extremely low energy productivity and gross neglect of even rudimentary environmental and public health and safety standards. This heightens the urgency of creating effective mechanisms for technical and financial assistance for the part of the world whose primary energy consumption in 2020 is expected to exceed by a considerable margin the combined consumption of North America, Western Europe, and the Pacific Rim.
DISSIPATIVE MATERIALS FLOWS FROM FOSSIL FUEL USE
Of all the dissipative materials flows into the biosphere that stem from human activities, carbon dioxide (CO2) formed in the combustion of fossil fuels is clearly the largest by mass, with the possible exception of industrial waste. For example, the United States generates approximately 12 billion short tons of wet industrial waste annually (Allen and Jain, 1992), but only 0.2 billion short tons of municipal solid waste (Kaldjian, 1990). However, the industrial waste statistics are greatly inflated because large wastewater discharges from industrial operations are included in the count. In comparison, the author estimates that in 1991, the United States' use of 2.2 billion short tons of fossil fuels resulted in the emission of 6 billion short tons of CO2, while global use of 10.5 billion short tons of fossil fuels in 1991 generated 26 billion short tons of CO2. The global estimate agrees closely with a 1992 estimate by the MITRE Corporation (Gouse et al., 1992). Using the normal practice of reporting CO2 emissions, this is equivalent to 7.1 billion short (6.4 billion metric) tons per year of carbon.1 The source of this carbon in the form of CO2 was global consumption in 1991 of approximately 24 billion barrels or 3.6
billion short tons of oil, 75 trillion cubic feet (Tcf) or 1.6 billion short tons of natural gas, and 5.3 billion short tons of coal, as estimated by the author from a variety of sources (Mensch, 1992; U.S. Department of Energy, 1991 a, 1991b).
Fossil fuel use also generates much smaller, but still substantial amounts of "acid gases"—sulfur oxides (SOx), nitrogen oxides (NOx), and reactive volatile organic compounds (VOCs). In 1985 the United States emitted 23 million short tons of SOx (reported as sulfur dioxide), 21 million short tons of NOx (reported as nitrogen dioxide), and 22 million short tons of VOCs (Saeger et al., 1989). A more recent study reports 1990 U.S. emissions of 23.3 million short tons of SO x as sulfur dioxide, 21.6 million short tons of NOx as nitrogen dioxide, 20.6 million short tons of non-methane hydrocarbons, 66 million short tons of carbon monoxide, and 8.3 million short tons of total suspended particulates (Alliance to Save Energy et al., 1992). The study also reports a breakdown of these emissions from stationary and mobile fossil fuel uses, as well as from miscellaneous sources, including natural sources such as forest fires. All of these emissions in the United States are on a downward trend due to federal and state legislation and regulation.
U.S. fossil fuel use currently represents roughly 21 percent of global fossil fuel use, and U.S. commercial energy consumption 24 percent of the world total. Because U.S. and global carbon emissions bear a similar relationship, one would expect the extrapolation of U.S. data to yield global emissions of SOx, NOx, and VOCs on the order of 100 million short tons per year each. Global data on VOCs emissions from fossil fuel use seem to be unavailable. However, the World Energy Council recently reported 1990 global emissions of 64 million metric tons of sulfur, or 141 million short tons of SOx as sulfur dioxide, and 24 million metric tons of nitrogen, or 87 million short tons of NOx as nitrogen dioxide (Commission on Energy for Tomorrow's World, 1992).,This compares with 1980 global emissions of 121 million short tons of SOx and 76 million short tons of NOx (Yokobori, 1992). These two sets of data seem reasonably consistent, considering the increase in world energy consumption over this 10-year period. They also are in the range of the amounts estimated from U.S. emissions of SOx and NOx, although lower figures would have been expected, given U.S. leadership in controlling these emissions from both stationary and mobile sources and the use of a larger percentage of nonpolluting fuels in the U.S. primary energy mix. Global emissions of sulfur and nitrogen compounds into the atmosphere from fossil fuel combustion and smelting operations reported as part of a new assessment of anthropogenic nutrient fluxes by Ayres provides another basis of comparison (Ayres, in this volume). It shows annual emissions equivalent to 92 million metric tons of sulfur and 45 million metric tons of nitrogen, or 203 million short tons of sulfur dioxide and 163 million short tons of nitrogen dioxide. Primary metals production may add 44 percent to the SOx emissions from direct fossil fuel use reported by the World Energy Council, but seems unlikely to nearly double NOx emissions. The Intergovernmental Panel on Climate Change reports 1990 anthropogenic sulfur
emissions of 98 million metric tons (World Meteorological Organization and United Nations Environment Program, 1992), which supports the value cited by Ayres.
In addition to reactive volatile organic compounds, the energy system also emits methane, a chemically quite unreactive greenhouse gas whose direct global warming potential over a 100-year period has recently been reassessed at eleven times that of carbon dioxide (World Meteorological Organization and United Nations Environment Program, 1992).2 Of the total estimated anthropogenic methane emissions of 506 million metric tons in 1990, approximately 100 million metric tons (or 20 percent) is believed to be of fossil fuel origin (World Meteorological Organization and United Nations Environment Program, 1992). However, other studies give a range of 440 to 640 million metric tons of annual anthropogenic methane emissions, with fossil fuels responsible for only 12 to 16 percent of the total (Alliance to Save Energy et al., 1992). Half of this is credited to emissions of methane from coal, largely from the release of methane from the coal bed during mining operations. For an excellent summary of the sources of anthropogenic methane emissions, including the relatively minor contributions from natural gas production, transmission, distribution, and use, see the Alliance to Save Energy et al. (1992). That publication also presents a comprehensive analysis of material flows—including CO2, methane, nonmethane hydrocarbons, SOx, NOx, carbon monoxide, and total suspended particulates—into the atmosphere from the U.S. energy system under alternative energy future scenarios.
Heavy metals present in coal and residual fuel oil, are released in some form during combustion and enter the biosphere, although the exact pathways are not well defined. A 1990 study cited by Ayres reports that approximately 200,000 metric tons of potentially toxic heavy metals are released to the atmosphere from fossil fuels use and that these emissions make up a significant share (about 27 percent) of total anthropogenic contributions of such metals, although fossil fuels contribute relatively little to the emissions of arsenic, cadmium, zinc, and especially lead (Ayres, in this volume). However, fossil fuels contribute the major share of vanadium and nickel and a significant share of the chromium, copper, manganese, selenium, tin, mercury, and antimony. Natural contributions to atmospheric trace metals emissions are broadly of the same order of magnitude as total anthropogenic emissions, except that natural lead emissions are much lower and mercury emissions much higher.
It should be noted that emissions from the combustion of fossil fuels increase the natural supply of three of the four major biological nutrients: carbon dioxide in air or water, and soluble compounds of nitrogen and sulfur. (Fossil fuels do not contribute to the flux of phosphorus.) Therefore, they would be expected to destabilize the closed cycles the biosphere had developed before human intervention (Ayres, in this volume). Carbon dioxide is, of course, the largest of these in tonnage, although the anthropogenic contribution to the natural carbon cycle represents by far the smallest fraction of anthropogenic nutrient fluxes—at most 4 percent. This is based on a minimum estimate of 200 billion metric tons of carbon
per year that cycles between the atmosphere and the terrestrial and ocean sinks, and a maximum total current annual anthropogenic contribution of 8 billion metric tons, including emissions from deforestation, other land use, and cement production (Ayres, in this volume; Commission on Energy for Tomorrow's World, 1992; Post et al., 1990; World Meteorological Organization and United Nations Environment Program, 1992).
Whereas claims of potentially detrimental effects of anthropogenic CO2 emissions are of relatively recent origin and still the subject of intensive debate, emissions of SOx and NOx have been considered potential public health hazards and ecologically harmful for a long time. Because NOx is more difficult to control than SOx, the focus of legislation and regulation in the past has been primarily on the latter. The 1990 U.S. Clean Air Act Amendments are the latest embodiment of this approach. However, with consensus in the United States on appropriate caps for SOx emissions, growing emphasis is being placed on NOx control. Fortunately, unlike CO2, SOx and NOx emissions are technically controllable to very low levels at substantial but manageable costs. The issue of heavy metals emissions is just beginning to surface but also should be amenable to technical solutions at acceptable economic penalties. Only the emission of CO2 as a possible agent of climate change seems intractable, unless it can be shown that the threat has been overstated and that further enrichment of the atmosphere with CO2 as a result of continued exploitation of global fossil fuel resources up to their full economic potential carries risks that are acceptable and justified by demonstrable benefits (Linden, 1991, 1992a, 1993; Singer, 1992).
BENEFITS OF ENERGY ABUNDANCE
The benefits of substituting commercial energy forms and energy-intensive technologies for human and animal labor and primitive renewable energy forms since the beginning of the Industrial Revolution appear to have vastly outweighed the costs, including environmental externalities (Linden, 1991; 1992b). Except in Marxist, fascist, and clerical dictatorships, every measure of human well-being has been tremendously enhanced by growing energy consumption. The large increases in life expectancy and declines in infant mortality and the general improvements in public health in the industrialized world followed the virtual elimination of hunger by energy-intensive agriculture and the creation of widely distributed wealth as a consequence of the explosive rise in labor and capital productivity. 3 Naturally, this dramatic change in the human condition over a period of less than 200 years is also a result of rapid advances in every field of science and technology, but growing energy abundance clearly played the major role.
In addition to the general contribution of primary energy and electricity consumption to such quantitative measures of economic well-being as gross domestic product per capita, the social benefits of energy use have been equally important. The abolition of slavery, serfdom, and child labor and of other forms of human
exploitation was inextricably linked to the energy revolution. More recently, the emancipation of women in the Western world and now also the Pacific Rim can be traced directly to the lightening of their traditional household and family duties with energy-intensive labor-saving devices. An added benefit of energy abundance is the economic and social mobility it generates, partly because of enhanced physical mobility. This mobility, in turn, generates greater political and cultural freedom and promotes egalitarianism. The relatively high mobility of the East Germans may even have contributed to the final collapse of the Marxist dictatorships of the former Soviet Bloc. The energy-intensive communications revolution has also played an increasingly important role in loosening societal and political constraints. The United States has clearly been the leader in breaking class, sex, and caste barriers, consistent with its often maligned ranking as the world's most energy-intensive economy. Western Europe and Japan have lagged the United States in liberalizing their more highly structured societies and emancipating their women because of greater constraints on all elements of mobility and communications access, but they are rapidly catching up. The stress on energy abundance as the driving force for the unprecedented social advances of the past two centuries is not intended to minimize the equally important philosophical and spiritual contributions of the political, social, and religious revolutions of the same period.
It should, however, be noted that primary energy consumption per capita is a relatively rough indicator of human well-being. The productivity of primary energy consumption provides a better gauge. Primary energy consumption per unit of GDP expressed in 1980 U.S. dollars of the United States and Canada—the North American members of the Organization for Economic Cooperation and Development (OECD) 4 is about twice that of its other members (U.S. Department of Energy, 1991b). In the so-called centrally planned economies (i.e., Marxist dictatorships), primary energy consumption per unit of GDP was four times that of the members of OECD other than the United States and Canada before the breakup of the Soviet Bloc. Primary energy consumption per capita in the United States is also roughly double that of Western Europe and Japan. There are obvious flaws in these comparisons of the energy intensities of various economies and, especially, of the former and present Marxist dictatorships with their totally artificial currency valuations. Monetary exchange rates in the market economies also deviate significantly from purchasing power parity, with the U.S. dollar generally under-valued—in some instances by a factor of two. This inflates the true energy intensity of the U.S. economy and creates the appearance of relatively equivalent economic well-being in the United States, Western Europe, and Japan in spite of substantial differences in more specific measures of affluence than GDP per capita. Moreover, the standard measures of human well-being fail to capture many of the widely recognized social benefits of the traditional U.S. policy of cheap and abundant energy.
Aside from these considerations that put in question the presumption that the
United States still ''wastes" large amounts of energy, there are a number of additional, readily quantifiable factors that explain the high apparent energy intensity of the U.S. economy in relation to Western Europe and Japan. These factors include a much lower U.S. population density; extensive sub- and ex-urbanization, which results in greater cost-effectiveness and convenience and therefore wider use of personal transport than public transportation; greater free-standing home ownership and much larger living space per capita; more extreme climate variations and resulting greater use of year-round indoor climate control; and the relatively large contributions of inherently energy-intensive extractive and basic manufacturing industries to U.S. economic output. All of these considerations are relevant to judging the comparative merits of U.S. energy practices.
Without them, Japan can rightly claim that as the most energy-efficient and least CO2-emitting of all the major industrial economies, it is the appropriate model. However, as of this writing, the yen is grossly overvalued relative to the dollar. Moreover, the Japanese economy is inherently more energy-efficient because of the demographic factors listed above and has been systematically restructured to concentrate on high-value-added, low-energy-intensity sectors. For example, the primary aluminum industry in Japan has been shut down. As a result, Japan imports large amounts of energy embedded in aluminum ingots, which does not show up in domestic energy consumption and CO2 emission statistics, and a great deal of pollution is exported. In addition, it is, of course, well known that the average standard of living in Japan is well below that of the United States and several other members of OECD.
TRENDS IN ENERGY PRODUCTIVITY
There is little question that technology advances will continue to reduce the relative growth rates of primary energy consumption in mature industrial societies. This will occur through cost-effective efficiency improvements paced by the ongoing electrification of many stationary energy uses. Primary energy consumption in OECD countries is now projected to grow at no more than half the rate of GDP even if energy prices remain relatively stable in deflated terms. However, electricity consumption is likely to continue to be closely linked to economic growth (Linden, 1988). Obviously, if prices escalate more sharply than expected because demand for OPEC oil production will increase to 40 million barrels per day by 2010 or even sooner, or because steep carbon taxes are imposed on fossil fuel use, the growth of primary energy demand relative to GDP may be less or might again turn negative as it did as a result of the oil price shocks of 1973/74 and 1978/79. This is not necessarily a beneficial outcome. As we learned during the 1970s and early 1980s, the initial economic impact of large energy price increases is severe (Linden, 1991). Similarly, most studies of the impact of carbon taxes to stabilize CO2 emissions from fossil fuel use at 1990 levels or reduce them by 20 percent show a reduction of economic output by several percentage points
lasting through most of the twenty-first century (Linden, 1991; Manne and Richels, 1992), although this result is sensitive to assumptions about revenue neutrality (i.e., corresponding reductions in other taxes).
The detrimental economic and social impacts of high energy prices and energy scarcity on developing countries are disproportionately severe because primary energy consumption per unit of GDP is relatively high and inelastic. The basic reasons for the inefficient use of energy in developing countries are the widespread use of energy price subsidies; inadequate energy supply and distribution infrastructures and associated low levels of electrification because of lack of capital and, especially, hard currencies; and limited access to the most desirable fuels as well as advanced conversion and end use technologies. As a result, consumption of commercial primary energy sources initially tends to increase faster than GDP and remains at relatively high levels relative to GDP until considerable industrialization is achieved (U.S. Department of Energy, 1987). Of course, exactly the same happened in the earlier stages of development of the currently industrialized economies. Primary energy consumption (excluding fuel wood and other primitive renewable energy forms) per constant dollar gross national product (GNP) in the United States rose until just after World War I, but has since dropped to less than half its peak value (Linden, 1988). At the same time, the share of primary energy consumption used in power generation rose from 10 to 36 percent and the efficiency of power generation improved threefold.
In contrast to the situation in developing countries, energy consumption in industrial countries is not only highly technology elastic but also extremely price elastic. Because of the long history of relatively high energy costs in Western Europe and Japan, their energy systems have evolved in an economic climate that generally favored capital investment over energy consumption. In the United States, the rational economic decision was to favor energy consumption over capital investment in more efficient energy systems until the price shocks beginning with the 1973/74 oil embargo attempt. However, as a result of multiple price shocks, U.S. primary energy consumption actually contracted from its interim peaks in 1973 and 1979 and did not exceed its 1979 peak until 1988, although vigorous economic growth resumed in the early 1980s (U.S. Department of Energy, 1992).
It is unlikely that substantial differences in energy productivity between industrialized countries can persist in a globalized economy, with its highly efficient capital and energy markets and free flow of technology. This will result in growing equalization of the structure of the energy economies of major trading partners within the constraints imposed by the demographic and infrastructure limitations noted before and the differences in indigenous energy resource endowments. The pressures of domestic and world competition will continue to push each of the national energy systems toward cost-effective efficiency improvements that conform to least-cost energy service strategies—that is, the delivery of heating, lighting, cooling, refrigeration, shaft horsepower, and passenger- and ton-miles, to the
end users at least cost, including the costs and benefits of quantifiable externalities. Even in the absence of command-and-control policies, therefore, it is likely that emissions of greenhouse gases will be reduced through market forces.
This trend toward lower greenhouse gas emissions will be enhanced as corporations and other entities take prudent measures and internalize potential future exposure to carbon taxes in their strategies and investment decisions. Some corporations already invest in preserving tropical rain forests and other means of offsetting CO2 emission on a voluntary basis. Premature regulatory and legislative intervention based on incomplete or erroneous information, especially on an international scale, may generate fewer benefits relative to costs than these market-driven actions. Market solutions are inherently more flexible than command-and-control policies, unless prior government intervention has excessively distorted the risks and rewards of rational economic behavior. Naturally, where market imperfections inhibit pursuit of least-cost energy strategies, government can play a constructive role in removing or mitigating them. Government must also play a major role in investing in research to provide the information base for rational market behavior. This applies particularly to the issue of anthropogenic climate change and its potential costs and benefits.
OPPOSITION TO ENERGY ABUNDANCE
A number of groups in the industrialized world have had a long-standing inclination to oppose energy abundance and energy-intensive economic and social development. These views about energy abundance may have been justified when the threat of imminent depletion of the most desirable fossil fuels, namely, oil and natural gas seemed probable. The issue of intergenerational fairness was raised in this connection—the questionable morality of robbing future generations of their share of the limited resource endowment by profligate use of energy by the present generation. "Saving" energy was given special moral status over "saving" capital, labor, and other goods and services. Thus, for example, we have an "Alliance to Save Energy" but no equivalent organizations to reduce other forms of consumption. The somewhat dubious ''energy crisis" further enhanced efforts to conserve energy and mobilized other important constituencies concerned about "energy security." These concerns about energy security and the quest for "energy independence" have been a long-standing U.S. preoccupation, and were so before they were heightened in the public eye by the loss of oil self-sufficiency in the 1960s and the attempts in the 1970s by the major oil-exporting countries to restrict world oil supplies for political and economic reasons (Linden, 1987-88, 1991, 1992b). In any event, the concept of self-sufficiency in oil or other critical commodities has become an anachronism in a globalized economy, This was already apparent early on in the "energy crisis" when the International Energy Agency was formed to administer oil-sharing agreements among participating industrial powers. Nothing has ever come of it or from the huge investment in the
U.S. Strategic Petroleum Reserve to moderate sharp price increases during the several instances of temporary world oil supply reductions of a few million barrels per 'day since the 1973/74 oil embargo attempt (Linden, 1987-88, 1991, 1992b). The benefits of unified action by major oil importers and exporters in today's interdependent world economy versus an independent U.S. pursuit of energy security were forcefully demonstrated following Iraq's invasion of Kuwait in 1990.
The historical opposition to energy abundance, and campaigns against unconstrained use of various fossil fuels (and also against nuclear power for a different set of reasons) however, did generate substantial benefits. The technical community, after premature and highly diversionary efforts to develop processes for conversion of the abundant U.S. and global coal and oil shale resources into what turned out to be uneconomic and unneeded substitutes for oil and natural gas, discovered price and technology elasticity of energy supply and demand. It initially focused on cost-effective end-use efficiency improvements with spectacular results. It then concentrated on the supply side with equally spectacular results. It soon became evident that technology advances were likely to defer the threat of oil and natural gas depletion and resulting sharp price escalations for many decades. As the threat of depletion has diminished, the focus of those opposing cheap and abundant energy has shifted to environmental issues. The newest and most effective of these issues—the threat of global warming caused by the continued unconstrained use of fossil fuels—allows opponents of energy abundance to combine saving energy with saving the planet. As noted before, most of the environmental impacts of fossil fuel use are being successfully addressed by technological development and regulation. However, other than the presently discredited nuclear option, there are no technically and economically feasible near-term responses to the global warming threat—if it is indeed a threat (Linden, 1993; Singer, 1992).
FUTURE ENERGY TECHNOLOGY AND UTILIZATION TRENDS
Over the longer term, there is a rather broad consensus among technologists that the global energy system will move toward essentially complete electrification of all stationary energy uses and that most mobile energy requirements that cannot be economically or technically satisfied with electric storage batteries will be met with hydrogen in compressed, absorbed, or liquefied form. Hydrogen for this purpose and for energy storage would be produced by water decomposition with nuclear heat, by electrolysis of water with off-peak nuclear power and wind and photovoltaic power, or by various solar heat and photochemical cycles. High-tech solutions such as geosynchronous satellites that collect and convert solar energy at high efficiency and beam it to Earth in some acceptable wave form cannot be ruled out in spite of formidable environmental problems. However, least-cost considerations suggest that this electrification trend will also require a
major worldwide revival of the nuclear fission option. As a prerequisite, new reactor designs would have to incorporate such features as passive cooling that would make them inherently safe, and the fuel cycle would have to be closed through plutonium recycle or through new fuel element technologies that allow substantial bum-up of heavy fission products in the reactor. Of course, controlled thermonuclear fusion always looms on the horizon as a possible ideal alternative for creating essentially perpetual energy abundance with minimal environmental impact, but both the technological and the economic barriers still look forbidding. Even if energy systems based on nuclear fission or fusion are ruled out because of political, economic, safety, or environmental considerations, technology is on the horizon for an electricity/hydrogen energy system that uses only solar or solar-derivative energy (such as wind and ocean thermal gradient power) as input. In such a system, it is even conceivable that the atmosphere and other sinks could be "mined" for CO2 to produce methane by reacting it with water photochemically, or to produce a wider range of organic compounds using hydrogen generated photochemically or by solar-thermal cycles.
Whatever the eventual path, time scale, and end point of this energy technology evolution turns out to be, it is clear that continued electrification will inherently improve the efficiency of the energy system and reduce its environmental impact. Electrification will also facilitate the transition from fossil fuels to more abundant or inexhaustible energy forms. However, the rationale for accelerating this process beyond the rate determined by market forces and technology advances within reasonable environmental constraints does not exist at present. Projections of catastrophic global warming before the end of the twenty-first century as a result of anthropogenic greenhouse emissions are losing credibility as the underlying science evolves (Linden, 1993; Singer, 1992). However, there is ample common ground between those who continue to believe that prudent planning requires internalization of the potential cost of some degree of global warming in energy decision making, and those who do not hold that such a view is necessary to manage the evolution of the global energy system. An acceptable compromise might be achieved by using appropriate tax and regulatory incentives to modestly accelerate the existing decarbonization and electrification trends occurring in the global energy system, within an overall conceptual framework of fully internalized, least-cost energy-service strategies.
Unfortunately, least-cost energy service strategies and market forces generally cannot be relied on to govern energy investments in the developing world. There, actions are dominated by the need to improve the quality of life of rapidly growing and often desperate populations racked by abysmal poverty, hunger, and excessive morbidity and mortality rates. Such conditions do not allow the luxury of making energy and land use decisions that conform with OECD or European Community standards. To varying degrees this observation also applies to the former centrally planned economies and those still governed by Marxist dictatorships. This is unfortunate in view of the environmental havoc they have already
created by their energy, industrial, and agricultural policies. The People's Republic of China is a case in point as the world's largest coal producer and consumer of more than one billion short tons per year. China is expected to double its production and consumption by 2010. In doing so, China will overwhelm any likely CO2 emission reductions by the industrial countries. Non-OPEC developing countries will also increase coal consumption by 200 to 300 million tons. India will be a leading contributor to this trend. More generally, primary energy consumption of the OECD in the absence of carbon taxes or excessive oil prices is projected to increase from about 180 quadrillion Btu (quads)5 to 230 quads by 2010 (U.S. Department of Energy, 1991b). Even if the OECD decides to constrain fossil fuel use and energy use through taxes or other measures, the rest of the world is unlikely to follow suit and is expected to increase its consumption from 170 quads to 230 quads by 2010 (U.S. Department of Energy, 1991b). Most of this energy demand growth will be met with fossil fuels since nuclear power has temporarily lost its competitive edge and public acceptance in many parts of the world, and the high capital costs of wind, photovoltaic, and hydropower and other renewable energy resources will continue to impede their deployment. In the developing world, this fossil fuel use will generally be in inefficient and highly polluting small installations and appliances because electricity and gas transmission and distribution facilities are inadequate.
Over the longer range, it is clear that energy extraction, conversion, and end-use technologies will have to continue to improve at a rapid pace to meet the needs of a global population that the World Bank estimates will exceed 11 billion in the year 2100. At that time, primary energy requirements are estimated at 900 to 1,500 quads after reaching 600 to 900 quads in 2060 (Gouse et al., 1992), compared with 350 quads today. Fortunately, as will be shown below, the economically recoverable fossil fuel resource base is sufficient to allow for an orderly transition to a sustainable global energy system over this period—a system that will, of necessity, depend increasingly on renewable and nuclear fission or fusion options and be largely electrified.
FOSSIL FUEL RESERVES, RESOURCES, AND CONSUMPTION
Proved global crude oil and natural gas liquids reserves are now roughly 1.1 trillion barrels, corresponding to more than 45 years of supply at current rates of consumption.6 Thus, proved reserves have increased by 400 billion barrels since the days of the "energy crisis" while another 400 billion barrels of crude oil were used over that period. At the same time, estimates of remaining ultimately (i.e., technically) recoverable oil and natural gas liquids resources have increased to 2 trillion barrels. A major part of this turnaround in world oil supply prospects has been due to advances in exploration, development, and production technologies—advances that continue at a rapid pace. It is, therefore, not improbable that today's 2 trillion barrels of remaining oil potential will eventually turn out to be not only
technically but also economically recoverable. This would meet current rates of consumption for 80 years. The true global oil potential is likely to be higher—there has been limited exploration of so many frontier areas, and huge amounts of more marginal liquid fuel resources, such as oil shale, tar sands, and other bitumens, may be economically exploited in the light of ongoing technology improvements. It is entirely feasible to convert a major share of these oil resources into transportation fuels that meet very stringent emission standards at costs that compare favorably with many other proposed solutions.
Even in the United States, there remains a large potential for cost-effective recovery of crude oil from the remaining resource base. In contrast to year-end 1992 proved reserves of only 24 billion barrels, a recent (October 1992) authoritative study conducted under the auspices of the U.S. Department of Energy projects the following remaining recoverable resources at various price (in 1992 dollars) and technology assumptions (Fisher et al., 1992):
Existing technology, $20/barrel
99 billion barrels
Advanced technology, $20/barrel
142 billion barrels
Existing technology, $27/barrel
130 billion barrels
Advanced technology, $27/barrel
204 billion barrels
A 1989 study by the American Association of Petroleum Geologists reported in Fisher et al. (1992) arrived at a very similar result: an estimate of 247 billion barrels of crude oil recoverable as of December 31, 1986, with advanced technology at prices of $25 to $50 per barrel (1986 dollars). Although no comparable data on price and technology elasticity are available, assessments of the remaining U.S. liquid fuels resource potential must also consider remaining technically recoverable natural gas liquids. A somewhat out-of-date estimate is 30 to 35 billion barrels (Institute of Gas Technology, 1989), compared to current proved reserves of 7.5 billion barrels. Thus, while it is much more profitable and practical to explore for and produce oil overseas because of the relatively high costs and growing regulatory constraints in the United States, the United States could theoretically meet its current liquid fuels requirements of 6 billion barrels per year from conventional domestic resources at a relatively modest cost penalty for as long as 40 years. The remaining crude oil resources recoverable at up to $27 per barrel with advanced technology are equivalent to 75 years of supply at the 1991 production rate of 2.7 billion barrels. In addition, advances in an environmentally benign, in-situ oil shale retorting technology that extracts high-quality shale oil by electric radio-frequency heating to 650-725°F, could make up to 400 billion barrels of shale oil recoverable at $20 to $30 per barrel from the richest portion of the western oil shale deposits—the subsection of the Piceance Basin that assays at least 25 gallons per ton of oil shale (Bridges and Sresty, 1991; Bridges and Streeter, 1991).
The global and U.S. natural gas outlook is even more reassuring than the
outlook for liquid fuels. Proved global natural gas reserves are 4,400 to 4,900 trillion cubic feet (Tcf), and conservative estimates of remaining ultimately recoverable resources are in the range of 8,000 to 9,000 Tcf, compared with annual use of 75 Tcf—that is, a 60- to 120-year supply at current rates of consumption. These gas reserves and resources represent two-thirds to three-quarters of the heating value of oil reserves and resources. This undoubtedly understates the true global natural gas potential by a wide margin on the basis of U.S. experience. Technology advances have already made huge quantifies of so-called unconventional gas resources—gas from "tight" sandstone and Devonian shale reservoirs and from coal beds—economically recoverable. In addition, better reservoir characterization techniques, and improved exploration, development, production, and well stimulation technologies have vastly increased projected recoveries from conventional formations. As a result, in contrast with U.S. lower-48 proved reserves of only 155 Tel at year-end 1992, a number of authoritative sources, including the National Petroleum Council and the U.S. Department of Energy, now project that the remaining lower-48 natural gas potential is 1,000 to 1,600 Tel, with 1,300 Tcf a reasonable consensus value. This is equivalent to 50 to 80 years of supply at current rates of consumption without taking credit for the growing imports from Canada and the potential lower-48 use of the large Alaskan resources. Based on studies by the Gas Research Institute (Woods, 1991) and the National Petroleum Council (Natural Gas Week, 1992), at least half of these lower-48 natural gas resources are currently recoverable at less than $4 to $5 per million Btu in constant dollars, and, with continuing extraction technology advances, at less than $3 to $3.50 per million Btu.7 Without allowance for the higher transportation and storage costs for natural gas, this would be equivalent in heating value to $17 to $30 per barrel of oil.
If the U.S. experience is extended to a global basis, recovery of as much as 10,000 Tcf at acceptable costs seems achievable—enough to meet 40 percent (rather than today's 21 percent) of current world primary energy consumption with natural gas for 70 years. Some global energy futures scenarios now assume ultimate recoveries as high as 12,000 fief (World Meteorological Organization and United Nations Environment Program, 1992). Natural gas causes little pollution (essentially no SOk and readily controllable NOx emissions), and causes total emissions from wellhead to point of use of only one-half of the CO2-equivalent greenhouse gases caused by conventional coal-fired power generation and associated coal-mining operations. In compressed or liquefied form, natural gas is also the most promising option among alternative transportation fuels. Therefore, stress on global natural gas resource development and use would provide an obviously ideal complement to electrification. Continued direct use of natural gas in many stationary applications, compressed natural gas for automotive fleet use, and gas-fired electric power generation with combined-cycle combustion/steam turbine systems is also consistent with least-cost energy service criteria over the foreseeable future.
Coal is, of course, by far the most abundant global fossil fuel resource. Proved reserves of all ranks of coal, including lignite, are in the 1.1 to 1.8 trillion short ton range, and remaining ultimately recoverable resources are on the order of 7 trillion short tons. At current rates of consumption, proved reserves alone represent 300 years of supply. The United States has the world's largest endowment in coal and lignite resources—260 billion short tons of proved reserves and 1.0 to 1.8 trillion short tons remaining ultimately recoverable resources, compared with annual production of roughly I billion short tons. From a fully internalized least-cost energy service perspective, it may be premature to conclude that coal, because of its often high sulfur content and high CO2 emissions, has an inherent disadvantage in meeting future energy requirements. Tremendous technological advances in clean and more efficient coal use have been made and continue at a rapid pace. Typical examples are atmospheric and pressurized fluidized-bed boilers in which limestone removes most of the sulfur and lower combustion temperatures reduce NOx emissions to acceptably low levels. The latest embodiments of integrated coal gasification and combined-combustion/ steam turbine systems are not only inherently capable of reducing SOx and NOx emissions to very low levels, they also increase the thermal efficiency of power generation from 30-33 percent to 40-43 percent and should eventually be able to achieve efficiencies in excess of 45 percent through further improvements in power generation train performance and plant design (Hertz et al., 1992; Holt, 1991). The first-cost premiums of these high-efficiency clean coal technologies over conventional power generation systems are rapidly declining and may soon disappear as their commercialization proceeds.
In aggregate, the energy content of the remaining technically recoverable conventional fossil fuels is at least 160,000 quads, or more than 450 years of potential supply at current rates of global consumption. If one includes the technically recoverable energy content of all remaining fossil fuels, including oil shale, tar sands and other bitumens, and unconventional sources of natural gas, global resources are on the order of 200,000 quads, equivalent to almost 600 years of consumption at current rates. Clearly, in view of the demonstrated price and technology elasticity of the supply and demand of fossil fuels, resource depletion is not an issue, even if between now and the year 2100 primary energy consumption trends follow the highest fossil fuel use scenarios of energy futures studies of the MITRE Corporation and the Intergovernmental Panel on Global Climate Change (Gouse et al., 1992; World Meteorological Organization and United Nations Environment Program, 1992). However, the potential ecological impact of liberating 700 billion to 2 trillion metric tons (depending on the projected increase in primary energy consumption and the projected decline in its carbon intensity) of the 4 to 5 trillion metric tons of carbon contained in these huge technically recoverable fossil fuel resources quite obviously is an issue.
FOSSIL FUELS IN THE EVOLUTION OF THE ENERGY SECTOR
The following snapshot of the world energy system reflects 1990/91 data:
World energy production and consumption are about 350 quadrillion Btu (quads) annually and are expected to grow to 460 quads by 2010.
Of the present consumption, 140 quads, or 65 million barrels per day or 24 billion barrels per year, is derived from liquid hydrocarbons; 75 quads or 75 trillion cubic feet per year from dry natural gas; 95 quads or 5.3 billion short tons per year from coal; 20 quads from nuclear energy; and 25 quads from hydropower and other renewables. (Use of nuclear energy and hydropower is reported in terms of actual or fossil-fuel-equivalent heat rates in power generation and, due to rounding to the nearest 5 quads, the total adds up to 355 quads.)
Electricity production is 11 trillion kilowatt-hours annually, derived from 2.6 billion kilowatts of installed capacity, of which 315 million kilowatts (or 12 percent) is nuclear. Roughly one-third of primary energy consumption is for power production globally, compared with about 36 percent in the United States.
Annual carbon emissions from fossil fuel use are in excess of 6 billion metric tons; SOx and NOx emissions are roughly 130 and 80 million metric tons, respectively; methane emissions are. 55 to 100 million metric tons; and heavy metals emissions are about 200,000 metric tons.
Electricity consumption, because ongoing electrification tends to offset efficiency gains, continues to increase roughly in proportion to national and global economic output. Primary energy consumption in mature industrial economies (including the United States and the other members of OECD) increases at no more than one-half the rate of GDP, whereas in developing economies it increases more rapidly—sometimes as fast or even faster than GDP.
Energy consumption per unit of economic output (GDP) in the United States and Canada is about twice that of the other members of OECD because of a variety of quantifiable factors that can be readily differentiated from "waste." On the other hand, energy consumption per unit of GDP in the former Soviet Union and its Eastern European satellites was four times that of Western Europe and Japan and twice that of the United States, and is still roughly at that level in the People's Republic of China.
In considering the further evolution of this energy system, one must first decide if more CO2 is good, bad, or indifferent for the environment. If CO2 emissions (and fossil-fuel-related methane emissions) pose no imminent threat, then there are only two limitations on the use of fossil fuels: the detrimental economic and social consequences of excessive rates of depletion and the need to minimize potentially harmful SOx, NOx, and reactive volatile organic compound emissions to the environment (although SOx and NOx, like CO2, are part of biospheric nutrient fluxes). Environmental considerations would also require some degree of control of heavy metals emissions from coal and residual fuel oil combustion.
Resource depletion is not a critical issue for the foreseeable future, if the world community wishes to maintain an unimpeded flow of energy commodities. Additions to known global oil and natural gas reserves continue to outstrip consumption by a wide margin, thanks largely to technology advances. This has invalidated projections of inevitable shortages and huge price increases. Rapid advances in clean and more efficient coal technologies that can substitute for oil and gas use in such important sectors as power generation further reduce the threat of supply inadequacies or sharp price escalations. However, even in assuming that fossil fuels will continue to meet the major share of global primary energy requirements for another 100 years because their inflation-adjusted prices will increase only moderately and no prohibitive carbon taxes will be imposed, substantial further efficiency improvements can still be justified economically. In fact, there are no longer any credible dissenters from the view that choices among options for energy supply and end use must be based on least-cost strategies to meet energy service requirements (heating, lighting, cooling, refrigeration shaft horsepower, passenger- or ton-miles, etc.). By definition, least-cost strategies mandate the incorporation of all available cost-effective efficiency improvements and the internalization of the costs of any quantifiable externalities of the various competing options to meet a given energy service demand.
On this basis and on the presumption that transition to an essentially inexhaustible and environmentally benign global energy system would take no longer than about a century, fossil fuels will most likely meet a major share of global energy needs during this period except for the potential problem of greenhouse gas emissions. As noted above, the quantities and extraction costs of remaining fossil fuel resources are unlikely to constrain such continued dependence, and there are a variety of technically and economically feasible options to control the emission of sulfur and nitrogen oxides and volatile organic compounds from the use of fossil fuels. It should also be possible to find solutions to the heavy metals emission problem in residual fuel oil and coal combustion. Continued electrification will be a critical element in this evolution to a sustainable global energy system. Electrification not only improves the efficiency and reduces the environmental impact of energy supply and end use but also facilitates the eventual transition from fossil fuels to even more abundant or inexhaustible energy forms. An important adjunct to electrification is wider use of natural gas because of its huge resource base and growing availability, low pollutant and CO2 emissions, and economic advantages as a fuel for power generation and transportation.
It is also important that in an environmental strategy largely based on electrification, coal be allowed to continue to play a major role because of its abundance, low cost, and wide geographical distribution. Fortunately, power generation systems that will be able to produce electricity from coal at only 70 to 75 percent of the energy input and CO2 emissions of currently available options, without SOx, and with acceptable NOx emissions now appear both technically and commercially feasible. These and other power generation and end use efficiency improve-
ments will greatly reduce the rate of increase in CO2 emissions, especially if they are also implemented by developing economies. However, if this is insufficient because CO2 emissions from fossil fuel combustion are found to be so detrimental to the environment that they have to be capped at current levels or reduced by 20 percent or more, the next logical option would be electrification of the energy system using nuclear fission in conjunction with several reasonably cost-competitive renewable options. Obviously, the reactor designs in such an expansion of nuclear power would have to incorporate such features as passive cooling that would make them inherently safe and the fuel cycle would have to be closed even though this is not economic at present. During a 100-year transition period to a sustainable energy system, fusion power may also become practical in spite of the formidable technical and economic barriers it faces today, in addition to unresolved environmental issues. Over this time frame it is likely that nearly all stationary energy uses would be electrified and that hydrogen in liquefied, absorbed, or compressed hydrogen, hydrogen-powered fuel cells, and electric batteries would gradually displace hydrocarbon and alcohol fuels to meet transportation needs. Hydrogen would be produced by water decomposition with nuclear heat, by electrolysis of water with off-peak nuclear and hydropower, and wind and photovoltaic power, or by various solar-thermal and photochemical cycles.
From an industrial ecology viewpoint, it appears that the global energy system, while contributing a large share of dissipative material flows into the biosphere, also has sufficient flexibility and technology development potential to keep its environmental impact within acceptable bounds. However, it is still uncertain if by far the largest of these dissipative material flows—carbon dioxide emitted in the combustion of fossil fuels—as a net detrimental impact on the global ecosystem. The carbon contained in carbon dioxide is the source of the major biological nutrient—carbon, so that the small anthropogenic contributions to the annual biospheric carbon flux may have quantifiable beneficial effects. But carbon dioxide is also the major greenhouse gas. Substantial further increases in its atmospheric concentrations could, therefore, cause undesirable changes in global climate, even though the costs of global warming caused by continued optimal fossil fuel use over a reasonable transition period to a sustainable energy system may have been overstated, especially in light of the benefits of energy abundance. Yet, a credible case can still be made that over the long term the emissions of carbon dioxide, other greenhouse gases, sulfur oxides, nitrogen oxides, and heavy metals associated with the unconstrained exploitation of the abundant remaining resources of fossil fuels could pose a significant threat to the global ecology and human well-being. However, technology advances that accelerate existing trends in electrification, decarbonization, and efficiency gains of the global energy system, as well as more rigorous control of conventional pollutant emissions, should
defer this threat sufficiently to avoid the economic and social harm inherent in many proposed policy responses.
These expectations for rational evolution of the global energy system in conformance with ecological constraints as well as economic and social objectives depend to an important extent on the ability of the developing world to meet its rapidly growing energy requirements in ways that do not excessively destabilize relatively fragile biospheric cycles on which long-term human well-being depends. This clearly requires major technological and probably financial assistance to the populous nations of the developing and the former and present communist world to ensure that their often highly coal-dependent energy systems make use of the most efficient and cost-effective and least-polluting energy supply and end use options. In any event, the task of managing the transition to a sustainable global energy system that can satisfy human needs over the indefinite future with minimal environmental impact would be greatly simplified if there were no need to curtail greenhouse emissions from fossil fuel use beyond the sizable reductions inherent in the pursuit of least-cost energy service strategies. The huge global endowment in economically recoverable natural gas, oil, and coal resources could then provide a century of lead time before alternative energy forms would have to meet the major share of global demand.
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