Volume 24, Number 4 October 1995


Symposium on Sustainable Technology and Jobs, and Why Physicists Should Care

Tina Kaarsberg

We present here a summary of the six talks given at an invited session at the March 1995 APS Meeting in San Jose, California.


The intent of this session was to demonstrate the physics research aspects of areas of technology that are important to society because they are resource-efficient and reduce or avoid pollution. A theme in all the talks was the looming global environmental problems that necessitate increased R&D and investment in more resource-efficient technologies. The session focused on energy-efficient technologies in the end-use sectors of buildings, transportation and industry as well as on more efficient energy conversion. We discussed the technologies themselves and public policies to promote their use. Finally, because of Congressional efforts to reduce spending in areas deemed to be more appropriate for the private sector, we discussed the reassessment of the federal government's role in supporting applied R&D.

The room was packed and, with all the questions, we ran out of time. Our internet addresses are given with the summary of each talk; please contact us for more information or copies of our handouts.


Tina Kaarsberg (Vista Technologies Inc., tina.kaarsberg@hq.doe.gov) introduced the session by discussing political changes between July 1994 when the Administration released "Technologies for a Sustainable Future" (and this session was conceived) to the end of the first 100 days of the new Congress.

In July 1994 there were high expectations of growth in federal funding for resource efficient technologies. The Clinton Administration gave pollution-avoidance technologies high priority in its proposed budgets and Congress supported this priority. There appeared to be a good argument for increased federal investment in such technologies. The Department of Energy (DOE) and others argued that environmental technologies have a high economic payoff and that these technologies create more jobs than any other federal infrastructure investment. Now, however, the federal role in programs involving such industry partnerships appears likely to decrease. Federal involvement in developing more sustainable technologies now appears to be unpopular with Congress. (UPDATE: House Congressional Resolution 67, the budget resolution agreed to by the House and Senate on 29 June 1995, would cut DOE's energy conservation R&D by 62% in constant dollars by 2002; most of the projects described in these talks come from this budget.)

Innovation and the environment: a new facet in environmental policy

Robert Lempert (Critical Technologies Institute at RAND Corporation, robert_lempert@rand.org) focused on studies of the innovation process with emphasis on environmental technologies and appropriate public policy response.

In recent years, environmental policies have begun to focus more on encouraging technological innovation throughout the private sector to help protect the environment. For instance, the Clinton Administration report "Technology for a Sustainable Future" links regulatory reform, R&D policies on environmental technologies, export promotion, and other policy areas with the aim of stimulating long-term economic growth which creates jobs while improving and sustaining the environment. The policies explicitly aim to help industry shift towards pollution avoidance instead of pollution control, and towards more efficient resources use. While environmental policies in the past have induced technical changes, they have not focused on science and technology, and in many cases have discouraged innovation. These new policy approaches explicitly aim to tap what appear to be tremendous technological opportunities which can help reduce the economic costs of environmental protection, use environmental technology as a competitive advantage for U.S. firms, and address some of the needs in developing countries for balancing both economic growth and environmental protection. Current initiatives, such as the Clinton Administration's recent excellence and leadership program, would allow firms to voluntarily adopt long-range plans to use innovative technologies to reduce pollution below the levels required by law. In return, the firms would remain substantially free of EPA permitting and reporting requirements as long as they remained within the boundaries of their pollution reduction plans.

This talk also suggested that assessments of costs and benefits of environmental regulations should take into account important new results in the economics of systems with increasing returns to scale. In such systems (which include many cases where new technology plays an important role), regulations may spur the development of new environmental technologies, which while more costly in the short-run, may in the long run provide economic and environmental benefits far in excess of current technologies. The auto industry's response to emissions regulations illustrates the effects of command and control versus using advanced technology for environmental benefits. Lempert, who did his PhD research in condensed matter theory, was asked how his physics background prepared him for policy research. He responded that general quantitative skills, as well as the ability to create simple phenomenological models, were useful.

From the lab to the marketplace: harnessing DOE laboratories to make U.S. buildings more energy-efficient

Evan Mills (Lawrence Berkeley National Laboratory, emills@lbl.gov) gave an overview of LBNL's efforts in energy-efficient building technologies and illustrated the lab's role with examples of past research success in windows and lighting, minimum efficiency appliance standards, and computer programs for building design.

One of the great challenges facing DOE is harnessing the power of its national laboratories in the post-cold-war era. With a workforce of over 30,000 scientists and engineers and a world-class R&D infrastructure, the labs are a major national asset. In fact, some laboratories have operated as a catalyst in the energy-efficiency marketplace since the first oil crisis, providing an substantial rate of return on federal research investment by helping bring new technologies to the marketplace. In this interdisciplinary field, pioneered largely by physicists, the approach is not one of belt-tightening, but rather a coordinated technological strategy for doing more with less energy while saving money, creating jobs, and protecting the environment. Partnerships with industry, utilities, government agencies, and universities are an integral part of the story.

As a case in point, since the mid-1970s a cumulative $70-million DOE research and development investment at LBNL helped to spawn a $2.5-billion annual U.S. market for electronic fluorescent ballasts, advanced glazing materials, and residential appliance efficiency standards. As of 1993, this R&D investment leveraged energy savings worth an estimated $6 billion to consumers. By the year 2015, these technologies will be saving consumers a net $16 billion annually, after subtracting the consumer costs of purchasing these efficient technologies. These and other savings will be facilitated by new computerized building design tools also developed at LBNL. The national labs' broader role in the buildings arena includes analyzing public policy issues such as the role of efficiency options as a mitigation strategy for global climate change, developing planning and demand-management methods used by electric and gas utilities, identifying technologies and analytical methods for improving indoor air quality, contributing energy information to the Internet, focusing on the special problems and opportunities presented by energy use in the public sector, and training young scientists to work in this new field. Much of the talk was based on Mills' January 1995 report entitled "From the Lab to the Marketplace" which was distributed at the sessions and is now is posted on the Web at http://eande.lbl.gov/ CBS/Lab2Mkt/ Lab2Mkt.cfm.

Materials and the greening of industrial ecosystems

Deanna Richards (Technology and Environment Program, National Academy of Engineering, drichard@nas.edu.) provided an overview of changes in material trends over the last couple of decades and its implications for managing materials from an industrial ecology perspective.

Industrial ecology, according to the White House report "Technologies for a Sustainable Future: A Framework for Action," is a new paradigm for environmentally sustainable development. This paradigm uses natural ecology as an analog for industrial systems where an assessment of the circulation of materials and energy flows through the economy and the natural ecosystem forms the basis for sound materials management strategies. To relate industrial ecology to product oriented life cycle analysis, Richards quoted physicist Robert Frosch: "a product is a transient embodiment of material and energy occurring in the course of material and energy process flows on the industrial system. "

The talk began with an overview of the changing nature of materials use in the economy, for example the increasing use of specialty materials, and the dissipative nature of their application. Richards examined trends in environmentally conscious manufacturing to highlight some of the technical challenges industrial ecology poses for industrial materials management. Barriers to better materials management include the lack of information exemplified by inadequate data to assess the potential for recovery of useful by-products from one industry to another. Other barriers are the need for reliable markets for waste stream products; the need for information about who has what (supply), who needs what (market), and who could produce something useful (potential supply); the disincentives in regulation which prevent the linking of industries or industrial processes; the lack of data for decision-making about the environmental preferability of materials. Over the long haul, improvements in separation technologies will be needed as recycling of durable products grows in importance. Finally, it takes energy to increase the recirculation of materials in the economy. Energy efficiency improvements alone are unlikely to fully meet these needs, and cleaner energy supply systems will be needed.

Energy conversion and the environment: the role of fuel cell technologies

Sivan Kartha (Center for Energy and Environmental Studies, Princeton University, icecream@princeton.edu) outlined the key environmental issues associated with our current modes of energy conversion, which are primarily based on fossil fuel combustion, and discussed a particularly promising near-term alternative: fuel cell technology.

Fossil fuel combustion technologies have come a long way from the high emissions and low efficiency of first generation power plants and vehicles. Still, the environmental costs of even today's relatively advanced combustion technologies are unacceptably high. A recent World Health Organization study of air quality and respiratory health has concluded that it is the rule rather than the exception that health guidelines are unmet for concentrations of atmospheric pollutants such as sulfur oxides, carbon monoxide, and lead in urban areas. Combustion of fossil fuels is also responsible for more diffuse and hard to target environmental problems such as acid precipitation and the threat of global climate change due to rising atmospheric CO2 concentration. Attempts to adapt fossil fuel combustion technologies to these increasingly apparent environmental constraints are likely to produce only marginal results. What is needed, in addition to concerted energy conservation measures, is an energy conversion technology that is inherently clean, efficient, and compatible with renewable energy sources.

Fuel cell technologies show tremendous promise for meeting this challenge. Fuel cells produce power by electrochemically reacting fuel and oxygen, avoiding those pollutants formed as a by-product of combustion and yielding higher efficiencies even at very small scales. First used in the aerospace program in the 1960's, fuel cells have in recent years advanced well beyond limited niche markets and are currently heading toward commercialization of the first generation of power plants, cogeneration in buildings, and transportation applications. A main impetus for this is the extremely clean operation of fuel cells; emissions from fuel cell power plants are two or three orders of magnitude lower than Clean Air Act standards for emission of sulfur oxides, particulates and nitrogen oxides from power plants, and emissions from fuel cell vehicles using hydrogen are zero. Moreover, the release of CO2 from the entire fuel cycle of a fuel cell vehicle would be significantly lower than that of a gasoline internal combustion vehicle even if the primary energy source were a fossil fuel such as natural gas or coal. With hydrogen produced from a renewable energy source such as biomass, wind, or solar, the carbon dioxide emissions from the fuel cell vehicle's fuel cycle could be drastically reduced below the current gasoline vehicle's carbon dioxide emissions. Since the study of fuel cells is still a fledgling field, there is considerable scope for basic research to rapidly translate into technological advances. For example, inefficiencies associated with processes occurring at electrode-electrolyte interfaces could be understood at a much more fundamental level, and efforts to advance overall fuel cell performance could thereby benefit deeply from the tools and ideas developing in surface science. As electric utilities and automotive manufacturers have realized, fuel cells have tremendous potential for answering the environmental challenges which we now face. While research, development, and the first steps of commercialization are already underway, it will still be necessary for basic and applied research to play significant roles in helping fuel cell technologies displace conventional combustion technologies from their central position.

Technology needs for resource efficient vehicles: the PNGV and beyond

Jim Anderson (Ford Motor Company, janderson@smail.srl.ford.com) discussed the new PNGV initiative, and Detroit's commitment to partnering with the federal government.

The Partnership for a New Generation of Vehicles (PNGV), announced in September 1993, is a unique joint venture between the Federal Government and the auto industry. Three factors motivate PNGV: (1) improving US balance-of-payments, (2) improving the global competitiveness of the domestic auto industry, (3) reducing petroleum consumption and CO2 emissions. PNGV has three goals: (1) improved automotive manufacturing, (2) near-term technologies for lower emissions and higher corporate average fuel economy, (3) a breakthrough vehicle with three times today's fuel efficiency. The PNGV 3X Fuel Economy Vehicle must be affordable (i.e. it must have an equivalent price of today's Chrysler Concorde, Ford Taurus or GM Lumina adjusted for economics). Further, it must maintain safety, emissions and recycling metrics. Production prototypes are to be available by 2004. Meeting all these targets simultaneously will require such technical innovation that goal #3 is sometimes viewed as a research program only. But in fact the PNGV time line rules out unproved research concepts, and goal #3 aims at demonstration programs in which proven technologies, developed for aerospace and defense applications, are applied to automobiles. Many PNGV programs focus on reducing the cost of these aerospace technologies.

This talk described the Technology Roadmap (obtainable by sending an email), completed on March 15, to the PNGV Economy Vehicle. Current plans call for a 40 percent reduction in total weight through use of aluminum- and graphite-reinforced composites in place of steel; acvanced powerplants including fuel cells as one option; and hybrid systems that recover energy lost in vehicle braking via generated and stored electricity, flywheels or ultracapacitors. NSF and DOE sponsored a workshop in January 1995 to look beyond the 10-year horizon. Auto industry technical people identified six technological areas for further investigation: energy storage devices such as on-board hydrogen storage; energy conversion such as advanced fuel cells; lightweight materials; atmospheric emissions; emission controls using clean NO_x catalysts; and sensors. Anderson was asked a wide variety of questions ranging from the safety of lightweight vehicles ("crash tests say yes") to Congressional PNGV funding ("could go either way--industry supports PNGV objectives and partnering with the government--reduced funding may just stretch out the time frame").

Why physicists should care

Finally Tina Kaarsberg emphasized the need for directed research--including physics research--in these technological areas to achieve the large improvements in environmental efficiency that will be needed.

The previous talks showed that there is important physics research on sustainable technologies. This talk showed the need for more directed basic research in the materials and systems areas by showing the large differences between non-industrialized and industrialized countries' energy use, emissions, and materials flows. Since population and hopefully per capita domestic product are both increasing, large improvements in the energy and resource efficiency of technologies will be required to sustain global society economically and environmentally. It is no accident that all of the talks in this session used transportation as examples. In the United States, the most urgent need for more sustainable technology is in the transportation sector. Crude oil and petroleum supply 97% of U.S. transportation energy and are responsible for $51 billion (38%) of the trade deficit. Vehicle miles traveled have increased 43% and transportation energy consumption has increased 14% since 1980.

. As we discussed at other sessions at the March meeting, there is a need for new areas of employment for physicists. Thus, increasing physicist involvement in research that leads to sustainable technologies is a win-win proposition. This talk emphasized the role of physics and physicists in such work. In particular, all the panelists are either physicists or work with physicists and thus it is possible for physicists to work in such areas.

Finally, although there is a bright future for these types of technologies, the substantial federal role described in the previous talks appears likely to decrease. In particular, many of the programs described are funded through applied DOE programs, and DOE itself has an uncertain future. New paradigms for joint government-industry development of more sustainable technologies, such as DOE's "technology partnerships," may be nipped in the bud. These partnerships are being attacked from the left, which complains about corporate welfare, and from the right, which complains that the Government is picking winners and losers. (UPDATE: House Resolution 1816, passed by the full House Science Committee in June, specifically forbids DOE from spending funds on technology partnerships).

The author is with Vista Technologies Inc., Suite 807, 1735 Jefferson Davis Hwy, Arlington VA 22202.

Why No Progress in ABM/TMD Negotiations?

Alvin M. Saperstein

The following observations stem from my one year of service as a Foster Fellow in the U.S. Arms Control and Disarmament Agency. They do not represent my beliefs or recommendations, nor may I speak for any official part of the U.S. Government; they are my perceptions of the beliefs of the relevant civil and military agencies and of how the political process is driving ballistic missile defense issues. Readers are welcome to try to affect the outcome of this important issue by engaging in the political process.

Two years ago we [for conciseness, I often use "we" for the U.S. Government] started negotiations with Belarus, Kazakhstan, Russian, and the Ukraine to allow the parties to develop and deploy Theater Missile Defenses (TMD) within the context of the Anti-Ballistic Missile (ABM) Treaty. It was thought that the talks would be quickly concluded since the presidents of Russia and the U.S. agreed on the following goals in their September 1994 Summit Statement: "The Presidents agreed on the fundamental importance of preserving the viability and integrity of the ABM Treaty...Both sides have an interest in developing and fielding effective theater missile defense systems on a cooperative basis." Yet no agreements have been reached, the formal channel for the talks is in abeyance, informal high-level talks creep forward fitfully, and Congress seems intent on stopping even those. Why no progress, despite the agreement of all Treaty parties on the need for effective TMD?

The impact of the SCUD missiles used by Iraq in the Gulf War went far beyond the military. Many nations, some of them considered "rogues," have actively deployed such theater ballistic missiles. There is good reason to believe that much more capable (in range, accuracy, load, ease in rapid and covert firing) missiles will soon be available throughout the third world. Without the perceived ability to defend its troops against such missiles carrying conventional or mass destruction (biological, chemical, nuclear) warheads, American policy-makers would be reluctant to project our forces abroad. And they now believe that an effective defense based upon fast interceptor missiles is technologically feasible.

Preserving the ABM Treaty

The Clinton Administration and its negotiating partners from the former Soviet Union also agree on the necessity of preserving the ABM Treaty, negotiated between the U.S. and USSR. in 1972. It was generally considered that the Treaty constrained the ability of the two superpowers to defend themselves against intercontinental nuclear missile attacks launched by them at each other, thus preserving an international stability based upon mutual assured destruction (MAD). The continued Treaty compliance of the parties allowed them to restrain the growth of offensive missile stocks (the only real threat to the heart of America since the War of 1812!) and allowed them to eventually reduce the size of this threat via the START Treaty process: START 1 has been ratified; START 2 is under legislative consideration by the U.S. Senate and the Russian Duma; its final ratification has been fundamentally tied, by the Duma, to the maintenance of the ABM Treaty, which thus fundamentally undergirds the future security of the American heartland. Presidents Clinton and Yeltsin acknowledged in May 1995 that "The United States and Russia are each committed to the ABM Treaty, a cornerstone of strategic stability."

The Treaty prohibits the testing of "non-ABM" interceptor missiles, such as the desired TMD interceptors, in "an ABM mode," i.e. against strategic ballistic missiles. However, nowhere in the Treaty are such target strategic ballistic missiles defined. Early on in the "demarcation" negotiations (the formal negotiations in Geneva these past two years attempting to create a demarcation line between the mutually desired TMD and the Treaty-constrained ABM defense), the parties agreed that testing against target missiles having a maximum speed below 5 km/s (range below 3500 km) would not be considered to be testing in an ABM mode. A TMD testing program against target missiles limited in such a way would be agreed to be in compliance with the Treaty.

However the Treaty also says that "non-ABM" systems should not be given "capabilities to counter strategic ballistic missiles," without defining such a capability. Russia (and the other Treaty negotiating partners) feared that highly competent interceptors, though only tested in a Treaty-compliant manner, may still have an inherent ABM capability, thus enabling the party possessing them to suddenly "break out" of the Treaty. It thus attempted to negotiate interceptor performance limits such as restrictions on their maximum speed.

We countered that the physical parameters of a single interceptor could not, by themselves, determine whether a system had ABM capability. (In fact, even a few pebbles, appropriately placed by slingshot or by rocket, have the ability to destroy an incoming strategic ballistic missile. Conversely, the fastest interceptor imaginable would not be able to counter a missile attack if it were one and the attackers many, especially if the interceptor's kill mechanism was direct impact with the incoming warhead rather than a nuclear explosion in its vicinity.) Further, we argued that we were not about to depend upon a non-ABM tested system to carry out vital ABM defenses. Nevertheless, we did acquiesce to the demand for interceptor speed limits, but only if they would not interfere with any of the TMD program development we contemplated. We thus proposed alternative and much higher speed limits for some interceptor basing modes. Russia refused to accept our proposed speed limits. And so there was an impasse at the formal Geneva negotiations.

Effect of the 1994 elections

Meanwhile, after the November 1994 elections, important parts of the U.S. House and Senate refused to entertain any limits on interceptor speeds or modes of employment nor would they consider any proposed limitations on remote or space-based sensors, for example limitations on cueing and guidance of interceptor missiles from off-base radars or satellite detectors. Fear was expressed that we were negotiating for a new TMD Treaty rather than simply adjusting the old ABM Treaty. In fact, bills were introduced forbidding us to negotiate on any demarcation terms other than the testing against 5 km/s target missiles.

We have argued that Russian concerns about interceptor capability were only valid, at best, in an engagement between one attacker and one interceptor and were irrelevant to any conceivable real encounter between Russian and U.S. strategic forces. Constraints on the latter were the real "meat" of the ABM Treaty; we said they were not diminished by the U.S. proposals.

The arguments moved to a higher level, that of Deputy Secretaries and Ministers, in London, Moscow, and Washington, where attempts were made to find agreed upon principles upon which the Russian and American Presidents could subsequently agree at their May 1995 Moscow Summit. There, agreement was announced that "Theater missile defense systems may be deployed by each side which (1) will not pose a realistic threat to the strategic nuclear force of the other side and (2) will not be tested to give such systems that capability." The term "realistic threat" was a source of contention. We have interpreted the phrase to imply force-on-force capability, where the forces are the American and Russian strategic forces. This would eliminate contentious negotiation over the properties of individual interceptors and their associated guidance and sensing instruments (though we have not specified how to measure this "realistic threat"), thus presumably allowing the U.S. to press ahead with its desired TMD developments and deployments under the Treaty. Others may take it to mean no less than the "inherent capability" interpretation held by the negotiators of the former Soviet republics at last year's Geneva sessions, a posture which denied Treaty sanction to our programs. The game is now back in the higher level court, where attempts will be made to see if there is enough overlap in the two major party's understandings of the joint Presidential demarcation principles to expect a successful outcome if we go back to the five-nation negotiations in Geneva.


We should go there in any case. Tradition requires two meetings per year of the Standing Consultative Commission (SCC), which is Treaty-enjoined to consider clarifications or modifications of the Treaty such as ABM/TMD demarcation, and there have been none this year. The question is whether the ball will come down on the side of an agreement allowing each side to proceed with the TMD programs they are presently contemplating, or on the no-agreement side. If there is an agreement, the ABM Treaty will still be said to be "operative"--treaties mean whatever the parties to the treaty agree they mean. In this case we will have agreed that the desired TMD is not ABM. We and the Russians can then get on with trying to create a stable, competitive peace between us as we each build our desired missile defenses, the "agreement" being an important part of that process. If there is no agreement, TMD systems will probably still be deployed, with each side acting unilaterally, but the relationship between the two countries will then be based more on weapons than on negotiations. Unilateral actions are not usually conducive to the building of communities, whether domestic or international.

The author is Professor of Physics at Wayne State University in Detroit, Michigan, 48202.

Natural Gas and Transportation

Albert A. Bartlett and Robert A. Ristinen

A recent article entitled "The Emergence of Natural Gas as a Transportation Fuel" (1) suggested that there would be great advantages if we in the U.S. would use natural gas instead of petroleum as the fuel for our vehicles. In support of this thesis the article gave a very optimistic picture of U.S. reserves of natural gas relative to our needs for fuel for transportation. The implication is that the gas reserves of the U.S. are sufficiently large to allow us to continue the conventional use of natural gas and also to supply the needs of U.S. transportation for an unspecified but long time. When we do the calculations, using data from a standard source, we find a very different picture.


We take our data from a U.S. Department of Energy (DOE) publication (2). DOE gives four estimates of U.S. natural gas reserves, where the "low" estimate is the quantity for which there is a 95% probability that there is at least this amount, and the "high" estimate is the quantity with a 5& probability that there is at least this amount.

The estimates of the Potential Gas Committee (PGC) and the National Petroleum Council (NPC) are described in a footnote in these words:

There are a number of recent non-government-generated natural gas resource estimates that are large, in part because (a) they include natural gas from sources such as coal beds and light sands, beyond the conventionally producible reservoirs that were included in the 1987 Department of the Interior estimate, and (b) they reflect larger estimates of ultimate recovery appreciation. For example, the PGC published in "Potential Supply of Natural Gas in the United States, December 31, 1992" is 1,001 trillion cubic feet. NPC's one-time, 1992 mean estimate, published in "The Potential for Natural Gas in the United States: Source and Supply," a was 1,065 trillion cubic feet.

It is important to note that the industry estimates are larger than the DOE estimates by about a factor of three, and the estimate in Physics and Society (1) is about 60% larger than the largest industry estimate.

In order to answer the question of the substitution of natural gas for petroleum, we need to make an estimate of the quantity of natural gas that has the same energy content as the petroleum consumed as motor fuel in the U.S. In (2) we find (pg. 161) that in 1993 the consumption of motor gasoline was 7.48 Mb/d (million barrels per day), of jet fuel 1.47 x 106 Mb/d, and of distillate 3.03 Mb/d. Some of the distillate is used for heating, so we made a guess that half is used for diesel trucks. This gives an estimate of the total transportation consumption of 10 Mb/d or 3800 Mb per year.

We now calculate the quantity of natural gas that has the same energy content as 3800 Mb of petroleum. In (2, p. 161) we find that one barrel of petroleum has the energy content of 5600 ft3 of natural gas (159 m3). The energy content of the motor fuel used in the U.S. in 1993 could be supplied by 60 x 1010 m3 of natural gas. The conventional use of natural gas in the U.S. in 1993 was 57 x 1010 m3. Thus, the annual energy consumption of liquid petroleum by vehicles in the U.S. is about the same as the present annual energy consumption of natural gas. So, if all U.S. vehicles shifted from liquid petroleum to natural gas, the shift would approximately double the rate of consumption of natural gas in the U.S.

Table 1 shows the results of simple calculations using each of the estimates of natural gas reserves. Column 4 gives the life in years of each of the estimates of U.S. reserves of natural gas at present rates of consumption, i.e. the number of years to consume the stated reserves of natural gas if the rate of consumption does not change from its 1993 value. Column 5 gives the life in years of each of the estimates, at present rates of consumption, if natural gas is supplying both the 1993 conventional needs plus the 1993 vehicle needs with no growth in demand in either category.

Table 1. Life Expectancies of U.S. Natural Gas

Five estimates of the reserves of natural gas in the U.S. and their life expectancies, at present rates of consumption. Column 3 shows the life expectancies in years for the present uses of natural gas. Column 4 shows the life expectancies in years if natural gas supplies the present needs plus the energy needs of U.S. motor vehicles.

Estimate	Reserves, 	Reserves, 	Present    Life* with
 	       	10^14 ft^3       10^12 m^3      Life*,y    vehicles, y
Low(2)          3.068            8.688           14           7
High(2)         5.072            14.36           24          12
PGC(2)          10.01            28.35           47          24
NPC(2)          10.65            30.16           50          26
Ingersoll**      17.7            50.0            83          42   
*	At present rates of consumption.
**	Includes "unconventional recoverable resources" not included in the DOE/PGC/NPC reserves.

The effect of growth

The economic expectations are for growth in the resource consumption rates, and growth obviously shortens life expectancies to values smaller than those shown in Table 1 (3). For the decade 1983-1993, the average growth rate of consumption of Rmotor gasolineS was about 1.5 %/yr (2, p. 161), which indicates that, although great improvements in vehicle efficiency have been made, the annual increase in total vehicle miles more than offsets the savings from the increases in efficiency of vehicles.


The calculated life expectancies shown in Table 1 should give pause. Would it be wise to make the enormous capital investment in shifting the fueling of even a fraction of the U.S. vehicle fleet over to natural gas when the effect would be to hasten the expiration of the resource upon which we currently depend for much of our home heating and industrial process heat? What would our children and our grandchildren use to heat their homes and operate their industries?

The estimates of natural gas reserves vary by about a factor of six from the lowest estimate cited by the DOE to the high estimate that is used in (1). When this range of uncertainty is present, and when the corresponding life expectancies are as short as those shown in Table 1, we must face the question of prudent behavior. Should we take steps to approximately double our rate of consumption of natural gas with no thought for the future, or should we reduce our rate of consumption so as to leave some of this wonderful fossil fuel for future generations?

Which path should we follow?

Some people argue that we can use resources as fast as we want because science and technology will always take care of our needs in the future. Others argue that we should reduce our rates of fossil fuel energy use, by what is popularly called "conservation," so that some of these resources will be available for our children and grandchildren. Given the enormous uncertainties in the amount of natural gas remaining, which path should we choose?

People are puzzled by the conflicting claims of scientists, some of whom say there are plenty of resources and that we need not worry, while others urge that we reduce rates of resource consumption. How does the average person choose between conflicting paths when there are "experts" advocating each path?

Fortunately there is a sound way to make the choice. Of the two conflicting paths, we suggest choosing the path that will leave society in the less precarious position in case we find later that we have chosen the wrong path. We can illustrate this by asking which of the following two positions is the less precarious: (a) We reduce rates of consumption of resources in the belief that resources are finite, and then, in 30 years we find that resources are really infinite and there was no need for our reduction of consumption. (b) We go on increasing rates of consumption in the belief that resources are infinite because scientists will always find substitutes for anything that runs out, and then in 30 years we find that resources are not infinite, the promised substitutes are not available, and/or they are too costly to be widely available.


"Sustainability" has become a popular term. It is used in all manner of planning at all levels from the local to the international. The definition of sustainability was given in the Brundtland Report (4): "Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs."

Because "sustainable" implies "for a time long compared to a human lifetime," and because the arithmetic of growth leads to large numbers in modest time periods, it is possible to write laws of sustainability (5). The First Law of Sustainability is: "Population growth and/or growth in the rates of consumption of resources can not be sustained." Although this law is absolute, it is ignored by many who speak of "sustainability."

The term "sustainable growth" is an oxymoron

We must help our students to learn to be extremely thoughtful and thorough in their evaluation of promises of great gifts when the gifts carry no indication of the range of uncertainty that goes with them.

1.	J.G. Ingersoll, Physics and Society April 1995, 5-7.
2.	Annual Energy Review  1993; U.S. Department of Energy, 
        DOE/EIA-0384(93), July 1994
3.	A.A. Bartlett, American Journal of Physics Vol. 46 (1978), 876-888.
4.	G.H. Brundtland, Our Common Future, World Commission on Environment
        and Development, Oxford Univ. Press, New York (1987), 43.
5.	A.A. Bartlett, Population and Environments Vol. 16, September 1994,

The authors are at the Department of Physics, University of Colorado, Boulder, CO 80309-0390