Editor's note: The references footnoted here are continued in numerical order from the first part of this article (OGJ, Jan. 19, 2003, p. 18); some references footnoted here appear in the first part.
This is the second of two parts.
Part I of this article addressed the widely different projections of the timing and magnitude of peak production of conventional crude oil and natural gas and of their remaining recoverable resources.
It also reviewed the potential of oil shale as a source of liquid and gaseous fuels and the large potential resources of heavy hydrocarbons—oil and tar sands and other bitumens and extra-heavy crude oil—as well as the potential resources of unconventional natural gas. The first part also considered a big increase in the estimate of potential resources of unconventional petroleum liquids, which could bring the total remaining recoverable resources of all petroleum liquids to as much as 8,000 billion bbl.
Such a large increase in this estimate raises the issue of extreme global climate change due to much higher potential emissions of carbon dioxide—the surrogate for all of the greenhouse gases—from natural gas and especially from both conventional and unconventional petroleum liquids.
The resulting problems of anthropogenic climate change and of development of technologies to limit these carbon emissions to acceptable levels were discussed in detail.
Part II of this article deals primarily with the options for extending the lead time for conversion of the global energy system to sustainable and carbon emission-free sources of power and hydrogen.
Energy system lead time
It is fortunate that the still-growing abundance of economically recoverable natural gas and petroleum liquids resources gives us several decades of lead time to decide how to stay most cost-effectively within a cumulative anthropogenic carbon emission limit of 1,000 gigatonnes between 1991 and 2100.
The obvious first priority of US energy policy must be to bring down natural gas prices by increasing supply so that this least carbon-intensive and least-polluting fossil fuel—which is the ideal energy source for highly efficient central, modular, and distributed power generation—is utilized to the fullest extent.
This maximum utilization is needed to reduce current reliance on inefficient coal-fired, steam-electric plants, with their inherently high levels of conventional pollutant and CO2 emissions, for more than 50% of US electricity use.
The basic problem in achieving this, of course, is that these are largely or fully depreciated coal plants, and the low delivered price of coal (about $1.25/MMbtu) make them a very low-cost source of power. The high efficiency of natural gas-fired, combined-cycle power plants cannot overcome this advantage at a total investment cost of roughly $500/kw and current natural gas prices at $3.50-5.50/MMbtu. However, further increases in utilization efficiency are expected, both for natural gas and for petroleum products used as transportation fuels. Natural gas prices also may drop to competitive levels if the traditional delayed producer response to high prices materializes and increases exploration and production investments.
In the surface transportation sector, hybrid electromotive propulsion in which a generator powered by a small internal combustion (IC) engine using conventional petroleum fuels displaces the much less efficient and inherently more polluting total reliance on IC engines. Another hybrid, which operates entirely with electromotive drive with an even smaller IC engine-driven generator operating in parallel with an oversize battery for temporarily high power demands, is already entering the market. The same is true of even more efficient and nearly emission-free fuel cell-powered automobiles, vans, trucks, and buses.
The ideal interim source of the hydrogen needed to operate the preferred fuel cell system (proton exchange membrane, or PEM, fuel cells operating at about 180° F.) is onboard compressed storage from hydrogen "filling stations" that use the fully commercialized natural gas steam reforming technology.32 Unfortunately, even under the best of circumstances, from the preceding analyses it already appears likely that reliance on natural gas and conventional petroleum liquids, in conjunction with nuclear, hydro, and wind power, may not provide the several decades of lead time necessary to convert the global energy system entirely to high-tech renewable energy sources. Energy sources such as solar-thermal and photovoltaic power in addition to wind power could provide a sustainable and carbon emission-free source of electricity for all stationary energy requirements and electrolytic hydrogen produced with this power as the dominant transportation fuel.
Extending this lead time by the use of the large resources of oil and tar sands and other bitumens, extra-heavy crude oil, and shale oil would result in substantially exceeding the limit of 1,000 gigatonnes of anthropogenic carbons emissions limit during 1991-2100. This is why it is so important to further develop and commercialize coal-fired power generation in which the coal is first converted to hydrogen and CO2, the CO2 separated and sequestered, and the hydrogen used for highly efficient, combined-cycle power generation and possibly as a source of transportation fuel.30 31
Such a shift in central power generation to a modification of the already fully developed integrated coal gasification, combined-cycle (IGCC) process could give us more than a century of lead time, thanks to the large global coal and lignite reserves, before we must rely on emission-free and sustainable energy sources.
An additional consideration is what role nuclear breeder reactors of the inherently safe and proliferationproof integral fast reactor (IFR) design—which uses onsite pyroprocessing of metallic fuel rods and whose reactor core is submerged in a pool of liquid sodium—could play in providing a very long-term source of emission-free power and of electrolytic hydrogen.33
It certainly seems prudent for the US to resume nuclear breeder reactor research, development, and demonstration in concert with other industrial countries in order to assess this alternative or supplemental option for extending the lead time to complete conversion of the global energy system to truly sustainable technologies. Simply expanding the global fleet of 350 gw of light-water reactors to 1,500 gw as recommended in a 2003 study by the Massachusetts Institute of Technology is not feasible because the existing fleet alone has only about 50 years of economically acceptable natural uranium supplies costing no more than $80/kg ($30/lb U3O3).34 35
Only breeder reactors that increase the roughly 0.6% utilization of natural uranium by 60-80 times and vastly increase the economically recoverable uranium resources at costs as high as $800/kg would overcome this problem.
However, as noted before, continued reliance on coal—with separation and sequestration of CO2 produced in the pressurized steam-oxygen gasification and catalytic water gas shift steps to yield hydrogen for highly efficient combined-cycle power generation, distributed generation, or as a surface transport fuel—would extend this lead time by at least 100 years.
Options for global energy
As shown by a number of articles published in OGJ last year, including the Future Energy Supply series (OGJ, July 14-Aug. 18, 2003),36 the primary concern has been with the time and magnitude at which the production of conventional crude oil and natural gas will peak.
Correspondingly, given the quantity of the remaining recoverable resources of these essential energy and raw material sources, the controlling factors in determining the primary energy mix are likely to be environmental constraints and revolutionary changes in surface transport technology.
There is a growing belief that climate change resulting from human activities is a quantifiable phenomenon. Since 1860, the average global surface temperature has increased by about 0.6-0.7° C., but the surface temperature record shows wide, unexplained fluctuations both below and above the 1961-90 average.26 27
For example, the increase of about 0.5° C. from 1860 to 1945 could not possibly have been caused by emissions of anthropogenic greenhouse gases and most likely was due to continued recovery from the "Little Ice Age" (1350-1850 AD), when surface temperatures were 0.5° C. below normal. This was followed by a decline of 0.2° C. during 1945-76, just when substantial emissions of CO2 began.
The final increase of about 3.5° C. during 1976-2000 is not a reliable measure of the anthropogenic greenhouse effect, for numerous reasons.27 For example, there is the failure of much more reliable satellite measurements by the National Aeronautics and Space Administration of the lower troposphere from about 15,000 ft to the Earth's surface to show any rising temperature trend since 1978 (except for the spike caused by the unusually severe 1998 El Niño event).37 Similarly, National Oceanic and Atmospheric Administration weather balloon measurements at 5,000-28,000 ft since 1958 show no definite increasing temperature trend.
The climate-change alarmists, some of whom wrote the Summary for Policy- makers of the 2001 Third Assessment Report by the Intergovernmental Panel on Climate Change (IPCC),26 using a wide range of emission scenarios, also emphasize the upper bound of 5.8° C. (10.4° F.) of the postulated average global surface temperature increase from 1990 to 2100.
But they do not point out that the equally probable lower bound is only 1.4° C. (2.5° F.). Even their average model results, using a mean climate sensitivity of 2.8° C. (5.0° F.) with CO2 doubling to 550 ppmv from preindustrial levels, give a range of average global surface temperature increases from 1990 to 2100 of 2.0-4.6° C. (3.6-8.3° F.).
The alarmists also generally fail to note that more than 95% of the greenhouse effect is due to water in various forms and is benign, since without it the average global surface temperature would be –18° C. instead of +15° C., and most of the Earth would be an arctic desert.27 Nevertheless, release of 5,150 gigatonnes of carbon contained in the Earth's crust in the form of remaining recoverable conventional natural gas, crude oil and condensate, and coal and lignite, as estimated earlier,5 would unquestionably cause unacceptable global warming. Under such a scenario, CO2 concentrations would rise to 900-1,000 ppmv by 2100, with highly unlikely business-as-usual scenarios, from a preindustrial level of 280 ppmv.25 26
Such a volume of carbon, of which coal and lignite represent 4,450 gigatonnes, does not include the unconventional sources of petroleum liquids and natural gas discussed in other parts of this article.
Thus, the prudent course is to follow the IPCC recommendations and limit cumulative emissions of carbon in the form of CO2 between 1991 and 2100 to 1,000 gigatonnes.
As noted before, this would require major technology changes in heavily coal-dependent power generation by first converting the coal to hydrogen and CO2, and then sequestering the CO2 in suitable geologic formations, coal beds, or the deep ocean. The remaining high-pressure hydrogen then could be used for extremely efficient power generation and as a regional source of surface transport fuel if the widely anticipated revolutionary conversion to electromotive propulsion using PEM fuel cells in tandem with oversized storage batteries as the power source materializes.30-32 This would increase the efficiency compared with IC engines about threefold.
This is one scenario for technological change to a carbon emission-free "hydrogen economy" that, although unsustainable because even the supply of coal is not inexhaustible, would increase the lead time to achieve such an economy by at least 100 years. The question of continued use of conventional natural gas and petroleum liquids until their exhaustion then would become irrelevant, because the total carbon content of their remaining recoverable resources is about 700 gigatonnes.5
Of course, if a major effort is made to increase the supply of nonconventional hydrocarbon fuels by the measures evaluated in the recent series in OGJ and the preceding discussion, the picture would change drastically. There is no assurance that nonconventional-hydrocarbon technologies plus CO2 sequestration that were economically competitive with a coal-hydrogen conversion plus CO2 sequestration scheme could be developed since, as noted previously, coal in the US delivered to power plants now costs only $1.25/ MMbtu.
Thus, we need to assess alternative scenarios for achieving essentially carbon emission-free and sustainable sources of electricity for all stationary energy uses and electrolytic hydrogen from these power sources for surface and, eventually, air transport. As discussed by Bob Williams in the last installment of the Future Energy Supply series (OGJ, Aug. 18, 2003, p. 18), the progress in developing such carbon emission-free and sustainable sources of power and hydrogen has been painfully slow. Wind power is furthest advanced and close to economically competitive but still handicapped by its intermittency, visual pollution, and general incompatibility with the efficient operation of the power grid.
Photovoltaic and solar-thermal power have made less progress in achieving commercialization because of high investment costs and an even greater problem of intermittency.
Hydropower has captured a substantial share of the electricity market and meets all of the requirements for being carbon emission-free, sustainable, and cost-competitive, but the global potential is limited, and there is also public resistance in expanding hydropower capacity, for environmental reasons.
A widely publicized potential source of sustainable and carbon emission-free energy is biomass but, in extensive studies by the author, it has been found that as a replacement for fossil fuels, biomass would have far greater land requirements than are available for energy crops, excessive labor costs, and the undesirable environmental impacts of monocultures. Widespread use of biomass energy also would upset the natural carbon cycle in the form of CO2 in which 200 gigatonnes circulate annually among the atmosphere, the ocean, and terrestrial sources and sinks.25 26 38 39 The basic problem with biomass is that photosynthesis is only 1-2% as efficient as photovoltaics in converting solar radiation into power.
This brings us back to nuclear power. It is evident that only breeder reactors could make a long-term contribution to carbon emission-free energy supply. But this still would not be a sustainable (i.e., inexhaustible) source, in spite of the sixtyfold to eightyfold increase in the utilization of the 0.71% of fissionable U235 in natural uranium—which eliminates the cost constraint of $80/kg of uranium ($30/lb U3O8) for light-water ("burner") reactors. Moreover, there is now a widespread reluctance to develop even a proliferation-proof and inherently safe design of a breeder reactor because of the enormous development costs, public opposition to nuclear power, and the likelihood that a commercially deployable breeder reactor would be too expensive.33
Decision by 2050
Thus, certainly by no later than 2050, we will have to come to a decision of how to restructure the global energy system so that it can continue to supply power and fuels needed for delivery of least-cost energy services to end users (i.e., heating, cooling, refrigeration, lighting, passenger miles, ton-miles, shaft horsepower, etc.).
If it becomes evident that such a decision cannot be made to convert to photovoltaic, solar thermal, wind, and other carbon emission-free and sustainable sources of power and hydrogen in time to stay within the proscribed anthropogenic carbon emission limit between 1991 and 2100, then the various alternatives to extend the lead time for such a decision need to be evaluated and compared.
One such alternative would be a drastic reversion of the declining share of coal as an energy source in conjunction with CO2 sequestration. A less likely alternative would be a huge expansion of the existing 350 gw fleet of light-water nuclear reactors, with and without reprocessing of the spent fuel, simultaneously with the development and deployment of economically viable breeder reactors.
What is already clear is that increasing the remaining recoverable sources of petroleum liquids from the various current estimates of as high as 3,600 billion bbl to as much as 8,000 billion bbl with the addition of unconventional sources (excluding oil shale) will lead to anthropogenic carbon emissions in excess of 1,000 gigatonnes prior to 2100, especially if shale oil and new, abundant potential sources of natural gas (such as methane hydrates) are added.5 9
This problem will be compounded by the (albeit unlikely) rapid phase-out of coal as a conventional source of power in inefficient (30-35%) steam-electric plants, especially if the modified IGCC option that includes CO2 sequestration continues to have estimated investment costs of $1,800/kw (excluding the cost of CO2 sequestration).30 31
This conundrum makes it unlikely that we can expect a continuation of the 60-year cycles for shifts to ever-lower carbon-intensive energy sources first postulated by Cesare Marchetti at the International Institute for Applied Systems Analysis, on whose advisory board the author served. This rationalization was further developed and updated by Nebosja Nakicenovic. Figs. 1 and 2 clearly show these 60-year cycles of conversion from primary dependence on fuel wood with an atomic carbon-to-hydrogen (C-H) ratio of 10:1, to coal with a ratio of 2:1, to petroleum liquids with a ratio of roughly 1:2, and now to natural gas with a C-H ratio of 1:4.40
The question is: What comes next? We all know that hydrogen is merely an energy carrier, not an energy source, and that nuclear power as a share of global energy supply has been declining (see table),11 so that a designation of the next 60-year cycle as "solar-hydrogen" or especially "solar fusion" is not very definitive.
It certainly seems unlikely that we can expect a very rapid decline in the share of coal as a global energy source, with such coal-rich and populous developing economies as China and India placing heavy reliance on this relatively cheap domestic energy supply. It also seems unlikely that China and India would choose the high capital cost, not yet fully developed, of modified IGCC technology to fill their power needs.30 31 Moreover, if the coal-based interim solution to the CO2 emissions problem is pursued, the 60-year cycle rationalization would become irrelevant, because the decline in the coal share of global energy use would be sharply reversed.
Optimize natural gas use
In any event, it would be wise to make a strenuous effort to optimize the contribution of natural gas to global energy supply as shown in the logarithmic version of the 60-year cycle chart (Fig. 2). In any event, natural gas is the logical transition fuel to a carbon-emission-free and sustainable global energy system thanks to its low carbon intensity, low conventional pollutant emissions, and inherent capability to be used for high-efficiency, low CO2 emission modes of power generation (such as combined-cycle turbines and fuel cells after conversion to 80% hydrogen and 20% CO2).
Thus, if we succeed in increasing the remaining recoverable global resources of natural gas and can build the long distance transmission lines and the facilities to move gas from stranded resources as LNG to major consumption areas, we may be able to substantially raise our estimate of those gas resources to as much as 20,000 tcf.
Another major advantage of natural gas is that it is already the largest source of hydrogen of whatever purity is required for many large-volume applications, such as petroleum refining, ammonia production, food processing, etc., and that it would be simple to separate and sequester the CO2 produced in catalytic steam reforming, followed by catalytic water gas shift to convert the carbon monoxide in the raw product gas with steam to more hydrogen and CO2. All of these operations have seen commercial use for many decades (except CO2 sequestration), so the top priority should be to confirm the storage capacity of geologic formations and coal beds and the economics of this final step in producing a large interim source of carbon emission-free hydrogen.22 3941
Most important is a comparison of the economics of using coal and natural gas as interim sources of hydrogen. Coal has, of course, two basic advantages: an extremely large US and global resource base and, in the US, a current wholesale cost of about $1.20-1.25/ MMbtu vs. $3.50-5.50/MMbtu for natural gas.
Options
This study of the options for the evolution of the global energy system was triggered by OGJ's unique Future Energy Supply series that dealt primarily with assessing the outlook for production of liquid petroleum fuels and natural gas from conventional and unconventional sources.
This effort, involving leading experts on these critical questions with widely different views, has been resolved with a wealth of data in favor of the optimists, who demolished the contention of the alarmists that global production of conventional crude oil will peak as early as 2004 at a level of 27 billion bbl/year—only slightly above current production.
A similar conclusion was reached on conventional natural gas production that the alarmists projected to peak at only 130 tcf/year in about 30 years.
However, there is a problem in restoring confidence in the long-term supply of the most desirable fossil fuels —natural gas and petroleum liquids—at reasonable price levels.
Fortunately, a convincing case was made that we are at the threshold of commercializing the recovery of oil and tar sands and other bitumens and of extra-heavy crude oil to raise the estimate of remaining global recovery of liquid hydrocarbons, including natural gas liquids and these heavy hydrocarbons, to as much as 8,000 billion bbl, and for remaining recoverable conventional sources of natural gas to as much as 20,000 tcf. These are far above the widely cited mean values of ultimate recovery of 3,000 billion bbl of conventional crude oil and of at most 15,700 tcf of remaining recoverable conventional natural gas.
However, unfortunately, this creates a new problem, in that utilization of these larger remaining recoverable hydrocarbon resources would emit about 1,200 gigatonnes of CO2 and thereby exceed the present consensus that total anthropogenic emissions of carbon in the form of CO2 equivalents between 1991 and 2100 should not exceed 1,000 gigatonnes in order to limit further global surface temperature increases to 2.0-2.5° C. (3.6-4.5° F.). This leaves the following options for continuing improvements in social and economic well-being of the world's growing population by providing ample and affordable supplies of environmentally benign forms of energy:
- Therefore, we must consider a fall-back option for extending the lead time for development and deployment of a global, sustainable, and carbon emission-free energy system by more than 100 years and limiting cumulative anthropogenic carbon emissions between 1991 and 2100 to 1,000 gigatonnes stabilize atmospheric CO2 concentrations at 550 ppmv, thus limiting further global surface temperature increases to 2.0-2.5° C. (3.6-4.5° F.). This fall-back option entails completion of the development and commercialization of technologies for power generation from coal, the most abundant fossil fuel, in which the coal is first gasified under pressure with steam and oxygen into a raw product gas containing hydrogen, carbon dioxide, and carbon monoxide. This raw product gas then is catalytically converted into more hydrogen and CO2 either before or after sulfur removal, with additional steam by the well-known water gas shift reaction (CO + H2O ‡ H2 + CO2) and, finally, the CO2 is separated and sequestered in suitable geological formations, coal beds, or the deep ocean. The remaining relatively pure (90%) high-pressure hydrogen then can be converted to electricity in highly efficient combined-cycle turbine systems, as well as used regionally by means of hydrogen transmission, distribution, and storage systems as a transportation fuel or for distributed power generation. The CO2 sequestration option also can be utilized in producing pure hydrogen relatively cheaply by catalytic steam reforming of natural gas followed by catalytic water gas shift and CO2 removal, with additional processing to remove any residual carbon monoxide and sulfur compounds, as long as supplies are ample. All of these process steps are fully commercialized and serve as the major source of hydrogen today.
References
Correction: Reference No. 39, shown here, was listed incorrectly as Reference No. 32 in the list of references at the end of the first part of this article, which appeared last week (OGJ, Jan. 19, 2003, p. 18).
32. Linden, H.R.,"Let's Be Rational About Hydrogen as a Vehicular Fuel," Public Utilities Fortnightly, Vol. 140, No. 6, Mar. 15, 2002, pp. 8-9.
33. Chang, Yoon I., "Status of Progress in IFR Development," Paper No. 94-JPG-NE-14, presented at the American Society of Mechanical Engineers Joint International Power Generation Conference, Phoenix, Oct. 2-6, 1994.
34. Deutch, John, and Moniz, Ernest J., co-chairs, "The Future of Nuclear Power—An Interdisciplinary MIT Study," Massachusetts Institute of Technology, 2003.
35. Uranium 1999 Resources, Production and Demand, A Joint Report by the OECD Nuclear Energy Agency and the International Atomic Energy Agency.
36. Williams, Bob, "Peak-oil, global warming concerns opening new window of opportunity for alternative energy sources," Oil & Gas Journal, Vol. 101, No. 32, Aug. 18, 2003.
37. "Earth Track," Environmental & Climate News, Heartland Institute, Chicago, September 2002, pp. 2,4.
38. Linden, Henry R., "Pathways to a Sustainable Global Energy System," Presented at the Goddard Engineering Colloquium, Goddard Space Flight Center, Greenbelt, Md., Oct. 6, 1997.
39. Linden, Henry R., "Let's Focus on Sustainability, Not Kyoto," Electricity Journal, Vol. 12, No. 2, March 1999, pp. 56-67.
40. Private communication, Nebojsa Nakicenovic, International Institute for Applied Systems Analysis, Laxenburg, Austria, Aug. 20, 2003.
41. IEA Greenhouse Gas R&D Program, as reported in Clean Coal Today, Office of Fossil Energy, US Department of Energy, Spring 1998.
The author
Henry R. Linden is Max McGraw Professor of Energy and Power Engineering and Management and director, Energy & Power Center, at the Illinois Institute of Technology, Chicago. He has been a member of the IIT faculty since 1954 and served as IIT's interim president and CEO from 1989 to 1990, as well as interim chairman and CEO of IIT Research Institute. Linden helped to organize the Gas Research Institute (GRI), the US gas industry's cooperative research and development arm that merged with the Institute of Gas Technology (IGT) in 2000 to form Gas Technology Institute, on whose Strategic Advisory Council he now serves. He served as interim GRI president in 1976-77 and became the organization's first elected president and a director in 1977. Linden retired from the GRI presidency in April 1987 but continued to serve the group as an executive advisor and member of the Advisory Council. From 1947 until GRI went into full operation in 1978, he served IGT in various management capacities, including four years as president and trustee. Linden also served on the boards of five major corporations for extended terms during 1974-98. He worked with Mobil Oil Corp. after receiving a BS in chemical engineering from Georgia Institute of Technology in 1944. He received a master's degree in chemical engineering from the Polytechnic Institute of Brooklyn (now Polytechnic University) in 1947 and a PhD in chemical engineering from IIT in 1952.
