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January 2001
Vol. 31, No. 1, pp. 14–20.
Starting the Process

Table of Contents

Nai Y. Chen

Mick WigginsEnergy in the 21st century

Improvements in the worldwide standard of living mean higher energy consumption. How will this be accomplished in the face of shortages and environmental demands?

What is the future of the energy industry? It is generally accepted that the supply of oil and gas is limited, but with the aggressive efforts in recent years, we have been able to find gas and oil at a greater rate than we consume them. Therefore, the date we run out might be extended far into the future.

Most people would agree that the energy industry, particularly the oil industry, played a major role in providing the fuels that powered the engine of industrialization. The evolution of Western society during the past two centuries followed the increase in its energy consumption. The population of industrialized nations has improved its standard of living, and people live longer and healthier lives. It is logical to assume that people in the rest of the world would like to follow suit and consume more energy to improve the quality of their lives.

By continuing this trend, however, we might be short of oil and gas before the 23rd century. Furthermore, industrialization has brought the recognition that the environment is fragile. Concerns about global warming due to excessive carbon dioxide emissions and about the other unhealthy pollutants in air, water, and soil are now subjects of discussion by the World Environmental Organization (www.world.org), which holds conferences to talk about issues such as global warming. Protection of the global environment and economic development are closely intertwined. These seemingly contradictory needs present challenges to every country to pursue the improvement of its citizens’ livelihoods while minimizing damage to the environment. The challenges involve educational, social, financial, economic, national, and international issues, in addition to the technical challenges to the energy industry in the 21st century that I will discuss.

Population and consumption

The increase in energy consumption is associated with two major trends: an increase in population and an increase in per capita consumption. In a lecture at the 1991 Spring National Meeting of the American Chemical Society (1), James Wei cited statistics on these two factors. He pointed out that the United States is the largest CO2 emitter simply because it consumes a huge amount of fossil fuels, whereas China, which ranks third after Europe, has a huge population and a low combustion efficiency. 

As shown in Table 1, the United States has about 5% of the world’s population but represents nearly 30% of the world’s annual energy consumption, whereas China has more than 20% of the world’s population and consumes less than 7% of the energy. In other words, the per capita energy consumption in the United States is more than 16 times that of China. The International Energy Agency, in its report on world energy consumption (2), projected that consumption will more than double by 2030 (Table 2), primarily because of growth in the developing countries.

Table 1. Comparison of carbon emissions with other factors
  % of world
Population, millions Population Gross national product Energy consumption Carbon emissions
United States
270  5.4 28.7 28.2 27.5
1069 21.3 1.8 6.9 9.8
Source: Reference 1.

Table 2. Projected worldwide energy demand
  2000 2030
World energy demand, MMBOE/Da 140 318
 Energy demand, % of world
OECDb 54 35
Non-OECD 46 65
a Millions of barrels of oil equivalent per day.
b Member countries of Organization for Economic Cooperation and Development.
Source: Reference 2.

It is ironic that the citizens of the United States, an active member of the World Environmental Organization, continue to consume more energy than everyone else in the world. Even with proper education of the American public on the consequences of excessive energy consumption, there may be no economic incentive to reduce consumption. Who is willing to conserve energy by driving a smaller car and paying more for clean fuel? Government regulations for automobile companies to increase fuel efficiency were enforced from the time of the first oil crisis in the early 1970s, but they have not been enforced since. The regulations were largely neglected after we could again import enough oil to satisfy consumer demands. Bigger and heavier automobiles are being built every year.

Our institutions have forgotten what happened during the energy crises: Gasoline was rationed, office lighting was turned off after-hours, and room heating and cooling were regulated by local governments. Today, most large offices are brightly lit 24 hours a day, and the room temperature of shopping malls and supermarkets is too cold in the summer and too warm in the winter, wasting energy. Are the citizens of the United States consuming more energy than they need to sustain or improve their living standard?

It is interesting that the retail business people are concerned about the impact of increased gas and oil prices on their profit margins. The public has also complained about the forecast rise in the price of gasoline, gas, and heating oil this winter. Again, we are driven by economic incentives and not by concern for the damage that excessive energy consumption does to our environment and our health.

Let me first review the history of the industrial revolution in the United States with respect to energy consumption. The pattern in America should provide guidance to the rest of the world to learn how to improve the quality of their lives without excessive consumption of energy.

Historical pattern of U.S. energy use

In 1988, Nebojsa Nakicenovic of the International Institute for Applied Systems Analysis in Laxenburg, Austria, presented his study of the pattern of energy use in the United States since 1850 at a National Academy of Engineering workshop (3). Before 1850, wood was the primary source of energy, as shown in Figure 1. Then came coal, oil, natural gas, and nuclear energy. Currently, oil provides more than 40% of the total energy consumed in the United States; natural gas and coal provide about 30% and 20%, respectively; nuclear and other sources provide the remaining 10%.

Figure 1. Graph showing primary energy sources
Figure 1. Primary energy sources in the United States since the early 19th century (3). Used with permission.

Hydrogen/carbon ratios in fuels
For compounds containing oxygen, the effective hydrogen content, or H/C atomic ratio, can be expressed as follows:

Hydrogen/carbon ratios in fuels

H, C, and O are the number of hydrogen, carbon, and oxygen atoms in the empirical formula of the fuel; [H2O], [CO], and [CO2] are the fractions of the oxygen converted to H2O, CO, and CO2. Assuming all the oxygen is converted to water, then

Hydrogen/carbon ratios in fuels

What comes next after oil? Because of its abundance, gas will certainly be available when we run out of oil. What will follow the gas wave? Some experts predict the revival of coal because of its abundance. The consumption rate of coal may increase, but a major shift to coal as an energy source is unlikely because of its adverse effect on the environment. Global warming due to CO2 emissions will be one of the major concerns of this century. Historically, fossil fuel use in the United States has evolved in waves or pulses every 50 to 75 years. In each period, more energy was derived from the hydrogen portion of the fossil fuels, as the nation moved from wood, which has an effective hydrogen/carbon ratio of zero, to natural gas, which has an effective hydrogen/carbon atomic ratio of nearly 4. (See box, “Hydrogen/carbon ratios in fuels”.)

This trend has led to the projection of an energy industry based on hydrogen, the most environmentally compatible fuel. Of course, to be truly environmentally benign, hydrogen would have to be generated from a noncarbonaceous source, such as the electrolysis of water. In this case, electric power generation would become ever more dominant in the coming century. The use of fossil fuels to generate electric power is already comparable to their use for producing transportation fuels.

Alternatives to fossil fuels are

  • safer nuclear power, 
  • less expensive photovoltaic power, and 
  • harnessing the power of nuclear fission. 

Because the total energy demand will be so much greater, even after oil is no longer the major supplier of energy, the oil and gas industry will remain large for years to come. The demand for petrochemicals will continue to grow and will consume an increasingly larger fraction of the oil and gas produced. To meet the demand for supplying truly clean fuels for transportation, full integration of fuel and petrochemical production may be the ultimate choice.

Transportation in the United States

Nakicenovic also showed that the mode of transportation in the United States has been evolving in a pattern remarkably similar to that of fuel usage. Figure 2 shows the mileage distribution of intercity transportation since the early 19th century.

Fig. 2 - Graph showing distribution of intercity transportation mileage
Figure 2. Distribution of intercity transportation mileage in the United States (3). Used with permission.
Before the development of railroads in the late 18th century, water provided the most important means of transportation. Railroads peaked around 1866 and were followed by the building of highways, which in turn peaked by 1960. Air travel is now gradually becoming the major mode of transportation. New technologies not only replace the old but also increase by orders of magnitude the total number of miles traveled, which would not be possible otherwise. This growth has increased the demand for energy, which is largely based on fossil fuels, so many in the industry advocate the development of technologies to produce substitute liquid transportation fuels using other resources, such as oil shale and coal. However, automobiles powered by the internal combustion engine may disappear from the scene before the 22nd century, just as the horse and carriage did in the past century.

Major technological innovations in transportation, like energy sources, also occurred in waves every 50 to 75 years. We are due for the start of a new wave. What is not shown in Figure 2 is the next wave after air travel. Although there is no guarantee that history will repeat itself, a new wave, the electronic age, is already here. Electronic communication will dramatically reduce our need to travel. It is not hard to imagine that we will conduct a significant number of business transactions, conventions, conferences, or even daily chores electronically, rather than traveling to do them. Furthermore, during the 21st century, cars powered by batteries or hydrogen fuel cells will probably replace cars with internal combustion engines for city transportation. If these projections are correct, we must reexamine the future of the energy industry from a different perspective.

Technical challenges—Resources

Natural gas. Natural gas is an ideal fossil fuel for generating electricity. In recent years, the use of natural gas and refinery fuel gas for power generation has become favored over coal and oil because they require less capital investment and are environmentally more friendly. The development of technology that combines gas and steam turbines in power generation increases thermal efficiency. The so-called cogeneration system, which supplies the steam requirements of an oil refinery and generates excess electricity for sale, has also become a popular practice in the United States to increase thermal efficiency.

Methanol produced from natural gas has been considered either a gasoline substitute or a blending component of gasoline to reduce air pollution. In recent years, oxygenates have been produced as gasoline additives to reduce air pollution in the United States. Methyl tert-butyl ether (MTBE), made by reacting methanol with isobutene, is a typical example, but now a few states have outlawed the addition of MTBE to gasoline because it causes unpleasant side effects such as headaches, it has found its way into groundwater, and it is a suspected carcinogen.

Methanol is also the intermediate in Mobil’s natural-gas-to-gasoline (GTG) process, which was commercialized in New Zealand in 1985. However, the process cannot be justified economically to produce liquid fuels as long as crude oils are available.

The use of remote natural gas as the raw material for producing liquid fuels, petrochemicals, and lubricating-oil base stocks could become economically attractive when this gas is valued much lower than domestic gaseous fuels. Several global oil companies, including Royal Dutch/Shell and ExxonMobil, have invested heavily in Southeast Asia using modified Fischer–Tropsch synthesis technologies (4, 5).

Crude oil and other carbonaceous resources. In the production of crude oils, today’s technology can economically recover less than one-third of the oil from reservoirs. In the past, the United States was blessed with a large resource base in energy, which contributed enormously to the growth of its economy. However, the increase in oil consumption has nearly exhausted all the domestic reservoirs, and more than 50% of the oil consumed today must be imported. It is not difficult to imagine the depletion of all the reservoirs in the world based on the current recovery technology.

New technology for economically extracting the remaining viscous heavy oil is needed to overcome the chemical and physical forces that immobilize it—to change the nature of the oil while it is in the ground to make it easier to extract. We can picture converting the reservoir into a large, complicated georeactor, filled with geological structures composed of layer upon layer of sand and rocks, subject to immense geological (tectonic) forces, and containing water, gases, and a mixture of hydrocarbons. This is the new frontier in reservoir technology.

The development of advanced reservoir technology to accomplish secondary and tertiary recovery of the remaining oil in conventional oil reservoirs will lead to the production of heavier crude oils. The heavier oil will have decreased effective hydrogen/carbon atomic ratios approaching those of other carbonaceous resources, such as Venezuelan heavy crudes, Canadian tar sands, oil shale, and coal. Excessive use of these resources will be incompatible with the global effort to reduce the emission of CO2 and other pollutants.

Biomass as an energy source. The production of biomass via photosynthesis is the major route by which gaseous carbon (CO2) is converted to solid and liquid forms—carbohydrates and other carbonaceous compounds. The burning of fossil fuels, the decomposition and fermentation of biomass, and the exhalation of humans and animals reverse this path. An imbalance between these two processes leads to either the accumulation or the depletion of gaseous carbon in the atmosphere.

Simplistically speaking, a rational solution to global warming would be to develop new technologies that can accelerate biomass production on land or in the ocean. At the same time, technologies are needed to store fresh biomass while older fossil fuels are being consumed (6, 7). It is ironic that although genetic engineering has made great strides in promoting the growth of biomass, not much attention has been paid to storage technology. The storage of biomass and the sequestration of CO2 are tasks that are much more difficult and have sometimes been written off as too expensive (8). In fact, we are running out of landfills and have to incinerate solid wastes, adding more dreaded gaseous carbon to the atmosphere.

Ethanol is produced as a transportation fuel from sugarcane in Brazil and from corn in the midwestern United States, both under government subsidies. There are three fundamental reasons that this technology is not an economical replacement for petroleum feedstocks:

  • Sugar, cellulosics, and starch are carbohydrates, literally a combination of carbon and water. Conversion to ethanol, which conceptually is a combination of two CH2 groups and one water molecule, involves trading a portion of the carbon in the biomass for the hydrogen in water. Because of process inefficiencies, the weight yield and thermal recovery are much poorer than those in petroleum refining, which is >90% efficient. This factor alone wipes out the cost advantage of the raw material. 
  • The hydrolysis–fermentation process is more capital-intensive than petroleum refining because of its complexity and low throughput per unit volume of capacity. 
  • The hydrolysis–fermentation process is much more energy-intensive than petroleum refining. The latter consumes less than 10% of its feedstock in processing. 

For these reasons, it is unlikely that biomass will replace petroleum in the foreseeable future if one accepts the premise that the relative value of various resources is tied to their Btu content, except when the supply of crude oil disappears. Making ethanol from corn actually increases greenhouse gas emission because of the fossil fuels and fertilizers needed to grow corn and the fact that the fermentation process produces CO2.

Instead of converting biomass to ethanol, it would be more thermally efficient to use this renewable resource as a boiler fuel for power generation. Direct use as boiler fuel avoids the inefficiencies of the conversion process and the huge capital investment required for conversion facilities. The development of a biomass gasifier–gas turbine power- generating technology has attracted considerable attention (9).

Noncarbonaceous resources. Solar, water, wind, and nuclear power are desirable as alternatives to fossil fuels and to help eliminate environmental hazards. The challenge is to reduce capital investment for utilization of these resources and to improve the safety of nuclear power. A successful nuclear fusion reaction using deuterium could provide a power source without producing radioactive waste. Unfortunately, these objectives are easier stated than done.

Technical challenges—Processing
Cleaner liquid fuels. The petroleum refining industry in the United States is currently taking a remedial approach to meeting the continually changing federal mandates on fuel composition. Instead of building new facilities, the industry elects to limit its investment to the modification of existing facilities in order to satisfy these mandates, namely, reduction of benzene and aromatics in gasoline, reduction of sulfur in all liquid fuels, and purchase or synthesis of oxygenates. The challenge to go beyond these short-term fixes is in catalyst technology. For example:

  • In response to the mandate to reduce aromatics in gasoline, the need is to shift naphtha reforming to paraffin hydroisomerization, to achieve octane requirements with less dependence on aromatics. 
  • In response to environmental pressure, the need is to develop heterogeneous isobutane alkylation catalysts to replace current liquid homogeneous catalysts, such as hydrogen fluoride and sulfuric acid. 
  • More effective catalysts for hydrodesulfurization and benzene removal are needed, to name just two. 

Again, easier said than done.

The alternative to these catalyst modifications is to take a proactive approach to protecting the environment by designing an environmentally friendly fuels refinery that produces a slate of safer, nonpolluting fuels and lubricants (10). Also needed is the development of environmentally compatible processes for refining other resources, such as natural gas, heavy oils, tar sands, and oil shale. In this approach, environmental health is viewed as the social responsibility of industries. However, overall cost effectiveness must also be considered.

The central theme of the proactive approach is to treat resources as mixtures of valuable chemicals and to design processes that convert potential pollutants to useful products, instead of letting them become pollutants and needing to remove them afterwards.

% of total
Liquefied petroleum gas 6.4
Gasoline 52.3
Kerosene, jet fuel  7.0
Diesel fuel, distillate 20.3
Heavy oil, asphalt, etc. 14.0
The future of processing.
Since the 1950s, the production of gasoline, diesel fuel, and jet fuels has been the mainstay of the U.S. oil industry. The table below shows the U.S. demand for refinery products in the 1990s. In fact, transportation fuels constitute more than two-thirds of the refined oil from a typical oil refinery.

A great deal of change in domestic oil refining will take place in the next 75 years in response to the following issues:

  • global warming and pollution, 
  • population growth, 
  • the renewed interest in urbanization, 
  • growth of high-speed electronic telecommunication, including the Internet and the spread of personal computer users, and 
  • growth of the electric automobile industry. 

By the end of the 21st century, oil will be past its dominance as the major source of energy. To meet the demand for truly clean transportation fuels, fuel production will be integrated with lube oil and petrochemical production. The production of jet fuel and diesel fuel will surpass that of gasoline, and all of the products from the fuel–lube oil–petrochemical complex will be synthesized almost free of pollutants. The raw material used by the complex will be extended from crude oils to other resources, including natural gas, heavy oils, tar sands, shale oil, and coal. Process technologies will be developed to reduce the cost of production and to avoid the generation of pollutants except the emission of CO2.

Facing the eventual displacement of internal combustion engines by transportation vehicles powered by hydrogen fuel cells, the oil industry may elect to provide hydrogen by producing it from hydrocarbons onboard the vehicle (11).

Efficiency, %
Gas turbine 15–25
Steam turbine  20–42
Internal combustion engine 20–25
Diesel engine  25–35

Energy efficiencies

The efficiency of converting the thermal energy in fossil fuels to work energy is relatively low for nearly all power- generating devices that require combustion of the fuel at a high temperature, because of thermodynamic limitations and mechanical losses such as friction. The table below compares the efficiency of common energy-converting devices. The challenge is to significantly increase this efficiency to conserve fossil fuels and reduce CO2 emission. For example, new technology using coal in power generation could increase efficiency from 30% to about 40%, and advanced combined-cycle power generation using natural gas could raise it to about 60%.

In a hydrogen fuel cell, chemical energy is directly converted into electricity without preliminary conversion into heat. Furthermore, the electric power generation does not involve any mechanical moving parts. Thus, the conversion efficiency of hydrogen fuel cells is much higher (60–80%) and could theoretically reduce fuel consumption by more than 50%.

The energy industries are challenged to sustain the supply of fossil fuel resources and meet changes in market demand. The demand for electric power will increase substantially in the 21st century, while our need to travel will gradually be replaced by global electronic communication. Although fossil fuels will remain major resources for power generation, advanced technologies will moderate the rate of CO2 emissions.

cartoon of two dinosaurs conversing.
"My broker said I should get into fossil fuels."


  1. Haggin, J. Chem. Eng. News 1991, 69 (17), 17–18. 
  2. International Energy Agency. 1998 World Energy Outlook; IEA Publications: London, 1998; p 396; www.iea.org/ (accessed Nov 20, 2000). 
  3. Nakicenovic, N. In Cities and Their Vital Systems: Infrastructure Past, Present, and Future; Ausubel, J. H., Herman, R., Eds.; National Academy Press: Washington, DC, 1988; pp 175–231. 
  4. Royal Dutch Petroleum Co. 1998 Annual Report. 
  5. Exxon Corp. 1998 Annual Report. 
  6. Nordhaus, W. D. Energy J. 1991, 12 (1), 37–65. 
  7. International Energy Agency. IEA Greenhouse Gas R&D Programme; www.ieagreen.org.uk (accessed Nov 7, 2000). 
  8. Hall, D. O.; Mynick, H. E.; Williams, R. H. Carbon Sequestration versus Fossil Fuel Substitution: Alternative Roles for Biomass in Coping with Greenhouse Warming; Center for Energy & Environmental Studies, Princeton University: Princeton, NJ, 1990. 
  9. Larson, E. D.; Williams, R. H. J. Eng. Gas Turbines Power 1990, 112, 157–163. 
  10. Chen, N. Y. Chem. Eng. Oil Gas (Shiyou Yu Tianranqi Huagong) 2000, 29 (4), 165–170 (in Chinese). 
  11. Chen, N. Y. Chem. Eng. Oil Gas (Shiyou Yu Tianranqi Huagong) 1999, 28 (3), 167–173 (in Chinese). 

This article was adapted from a paper by Dr. Chen published in China last year (China Petrol. Proc. Petrochem. Technol. Quarterly 2000, 1, 14–21).

More on the energy industry
For a survey of Web sites covering energy and fuels, see this month’s Touring the Net.

Nai Y. Chen is a technical consultant and energy conservation advocate (4 Forrest Central Dr., Titusville, NJ 08560-1310; 609-737-0321; naiychen@earthlink.net). He received his B.Sc. degree in chemistry from the University of Shanghai, China, his M.S. degree in chemical engineering from Louisiana State University, Baton Rouge, and his Sc.D. from the Massachusetts Institute of Technology in chemical engineering. He retired in 1994 after almost 34 years as a scientist with Mobil Research & Development Corp. He is credited with the first commercial catalytic process using a natural zeolite. His discovery of the unique properties of ZSM-5 in the late 1960s helped to pioneer shape-selective catalysis. He is the author and co-author of 10 books and numerous articles; he holds more than 126 U.S. patents. He was elected to the National Academy of Engineering in 1990.

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