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14 Future Challenges for the Chemical Sciences in Energy and Transportation Safe, secure, clean, and affordable energy and transportation are essential to the economic vitality of the world. As we look to the future the next 50 years and beyond there will be many severe challenges to both energy and transporta- tion created by population growth, economic growth, ever-tightening environ- mental constraints, increasing climate change issues and pressure for carbon dioxide emission limits, geopolitical impacts on energy availability and the energy marketplace, and a changing energy resource base. Science and technology- specifically the chemical sciences will play a significant role enabling the world to meet these challenges. The opportunities are challenging and exciting. Advances in nanosciences, information sciences, biosciences, materials science, and chemical sciences will lead to solutions not contemplated today. The key will be fundamental research at the intersection of these sciences and developing new engineering to bring the new technologies to fruition. To define the energy and transportation challenges and opportunities for the chemical sciences in the 21st century, future needs can be divided into two time frames midterm (through 2025) and long term (2050 and beyond).) In the mid- term: World energy demand will increase approximately 50 percent above 2002 levels. (Alexis Bell) Fossil fuels will remain abundant and available as well as continue to provide most of the world's energy. (Nathan Lewis) iThese future needs were identified by the committee based on the Workshop presentations. For each the presentation from which the need was identified is identified in parentheses. 80

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FUTURE CHALLENGES FOR THE CHEMICAL SCIENCES 81 There will be a drive toward fuels with higher hydrogen-to-carbon ratio but balanced against the need to utilize the extensive low hydrogen-to-carbon coal resource base in the United States. (Venki Raman, Nathan Lewis) Tighter environmental constraints will be imposed. (Nathan Lewis) Government-mandated carbon dioxide limits will be initiated, leading to a need for carbon dioxide sequestration technology and introduction of large amounts of carbon-neutral energy. (Stephen Pacala) A real but acreage-limited role will be found for wind and hydro energy sources. (Nathan Lewis) Nuclear, solar, and biomass energy will play a growing role in the nation's energy mix. (Patricia Baisden, Jiri Janata) Cost-effective Hydrogen-2 fuel cell technology for transportation and power will be developed. (John Wallace, James Katzer) A significant penetration of vehicles with new high-efficient clear power sources will be seen in the transportation market. (John Wallace, James Katzer) . Most Hydrogen-2 will be produced from fossil fuels.2 In the long term: World energy demand will rise to approximately two times the present energy usage. (Nathan Lewis) Fossil fuels will remain abundant and available, but limitations on their use will arise because of worldwide constraints on carbon dioxide emissions. (Nathan Lewis, Alexis Bell) There will be a need for significant carbon-neutral energy. (Most of the presenters) . . Fully developed carbon dioxide sequestration technology will be one of the important approaches to solving the energy problem. (Stephen Pacala) Coal and nuclear energy will continue to play a significant role in meeting world power demands. (Nathan Lewis, Alexis Bell) Renewable energy (wind, biomass, geothermal, photovoltaics, and direct photon conversion e.g., solar photovoltaic water splitting) will play an increas- ingly important role. (Nathan Lewis, Ralph Overend) Most of world's vehicles will run on hydrogen from a carbon-free source or other fuels that are carbon-neutral. (John Wallace, James Katzer, Venki Raman) New cost-effective solar technology will be widely available. (Nathan Lewis, Ralph Overend) Hydrogen-2 and distributed electricity will be produced by solar energy, either through photovoltaic electrolysis or by direct solar photoelectrolysis. (Nathan Lewis, Ralph Overend) 2Venki Raman, in his presentation to the Energy & Transportation Workshop, noted that presently eighty percent of the hydrogen produced is made from natural gas steam methane generation.

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82 ENERGY AND TRANSPORTATION While these scenarios can be debated, the drives they create in the chemical sciences are not greatly affected by the severity of the scenarios. They do point to a need to enhance the energy efficiency of fossil fuels in production and utiliza- tion, to develop a diverse set of new and carbon-neutral energy sources for the future, and to maintain a robust basic research program in the chemical sciences so that the technical breakthroughs will happen to enable this future. The path will not be straightforward, however. While it is possible to predict research areas that most likely will have an impact on the development of more efficient energy and transportation systems, and direct resources to these research areas accordingly, looking back over the previous 50 years has shown that some of the most significant breakthroughs that have impacted energy and transporta- tion were not foreseen. For example, advances such as the development of solid state physics and the broad applicability of lasers to many areas not only in scientific research, but daily life as well were not anticipated when these break- throughs were first made. Advances such as these point to the continued impor- tance of basic research. While future advances and challenges cannot always be predicted, robust long-term basic research can help to meet challenges, both anticipated and unexpected. Particularly in the United States, interest and appreciation of the importance of science and technology is decreasing. Fewer U.S. students are entering techni- cal careers. Energy research is decreasing significantly in both the private and public sectors. While this workshop and report do not address these issues, they must be resolved or the United States will be in jeopardy of not being able to meet its future energy and transportation requirements. KEY CHALLENGES IDENTIFIED AT THE WORKSHOP ON ENERGY AND TRANSPORTATION The needs of the energy and transportation sectors provide a number of challenges over the next century that the chemical sciences are uniquely suited to play a critical role. Many of the issues discussed in Workshop on Energy and Transportation, from increased energy efficiency from fossil fuels, to reduction of pollution, to sequestration of carbon dioxide, to development of new materials for vehicle fabrication, to new low cost renewable energy technologies, if not wholly chemical in nature, contain significant chemical science content. As chemical scientists seek to address these issues, the crosscutting nature of many of these challenges should be recognized at the outset. Many of the challenges in energy and transportation will be met with technologies that have broad applica- tions in a number of different fields new catalysts for increased reaction speci- ficity and efficiency, new membranes for better separations, and new methods of fabrication to produce materials with predictable and very specific properties are just a few of many such examples. By working with scientists and engineers in other disciplines, such as materials scientists, bioscientists, geologists, electrical

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FUTURE CHALLENGES FOR THE CHEMICAL SCIENCES 83 engineers, information scientists, mechanical engineers, and others, a multi- dimensional approach to these challenges will be accomplished and the likeli- hood for comprehensive new solutions will i, increase significantly. The following challenges were identified resulting from the presentations and discussions at the Workshop. Although these challenges were identified as a result of the Workshop, final responsibility for these statements rests with the organizing committee. ENERGY Fossil fuels will remain an abundant and affordable energy resource well into the 21st century. Since potential limitations on carbon dioxide emis- sions may restrict their utilization in the long term, it is imperative that chemical sciences research and engineering focus on making significant increases in the energy efficiency and chemical specificity of fossil fuel utilization.3 Professor Bell identified new multifunctional highly selective catalysts and membranes and corresponding process technologies as key research areas where opportunities will exist for major steps forward. These new catalysts and materials will allow much greater process efficiency (reduced carbon dioxide) through operations at lower temperatures and pressures and also by combining multiple process functions (i.e., shape selectivity and oxidation) in a single catalyst par- ticle, thus reducing the number of process units in a plant. These new materials and processes will increase the efficiency and environ- mental cleanliness of hydrocarbon production and refining and also enable refineries to produce chemically designed fuels for future vehicle power trains. These chemically designed fuels will play a key role in new power trains. These engines will require fuels that can optimize the efficiency of the entire power cycle while at the same time produce essentially no harmful exhaust. The best way to accomplish this is by designing the engine and fuel interactively, and this will lead to more chemical specificity requirements on the fuel. Natural gas has tremendous potential for meeting the energy needs of the future because it has a high hydrogen-to-carbon ratio and can be converted to Hydrogen-2 and environmentally clean liquid fuels.4 Current technology for converting natural gas to liquid fuels is by Fischer- Tropsch technology, which converts methane to syngas (carbon monoxide and 3Alexis T. Bell, University of California, Berkeley, Presentation at the Workshop on Energy and Transportation. 4Alexis T. Bell, University of California, Berkeley, Nathan Lewis, California Institute of Tech- nology, presentations at the Workshop on Energy and Transportation.

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84 ENERGY AND TRANSPORTATION H2) and the syngas to liquids (the Fischer-Tropsch step). While there have been major advances in the technology in the past decade, it is much less energy effi- cient than today's refining processes. New catalysts, membranes and processes are needed that will convert methane directly to H2 and liquid fuels without going through syngas. This would tremendously increase the energy efficiency of methane conversion. Liquid products from these processes are chemically pure, containing no heteroatoms (i.e., sulphur, nitrogen, metals). Management of atmospheric carbon dioxide levels will require seques- tration of carbon dioxide. Research and development into methods to cost effectively capture and geologically sequester carbon dioxide is required in the next 10 to 20 years.5 As noted in Professor Pacala's presentation, effective management of the increasing anthropogenic output of carbon dioxide into the atmosphere will be a significant challenge for the chemical sciences and engineering over the 21st century. Development of sequestration technology to address this issue will require a thorough understanding of carbon dioxide chemistry and geochemistry along with an elaboration of the mechanisms involved in carbon dioxide absorp- tion, adsorption, and gas separation. Also, effective sequestration will require new engineering knowledge to capture and transport the carbon dioxide to the sequestration site most likely a geological reservoir. A more thorough under- standing of the geochemical, geological, and geophysical nature of the sequestra- tion site will be required to ensure that carbon dioxide does not escape over centuries of storage. Biomass has the potential to provide appreciable levels of fuels and electric power, but an exceptionally large increase in field efficiency6 is needed to realize the huge potential of energy from biomass.7 Biologically based strategies for providing renewable energy can be grouped into two major categories: (1) those that use features of biological systems to convert sunlight into useful forms (e.g., power, fuels) but do not involve whole living plants, and (2) those involving growth of plants and processing of plant components into fuels and/or power. Both are very important. Long-term im- provements can be expected in the development of both biomass resources and the conversion technologies required to produce electric power, fuels, chemicals, materials, and other big-based products. As molecular genetics matures over the Stephen W. Pacala, Princeton University, presentation at the Workshop on Energy and Transpor- tation. sin agriculture, field efficiency is the ratio of effective field capacity and theoretical field capacity. 7Alexis T. Bell, University of California, Berkeley, Nathan Lewis, California Institute of Technol- ogy, Ralph P. Overend, National Renewable Energy Laboratory, presentations at the Workshop on Energy and Transportation.

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FUTURE CHALLENGES FOR THE CHEMICAL SCIENCES 85 next several decades, for example, its application to biomass energy resources can be expected to significantly improve the economics of all forms of big-energy. Improvements in economics, in turn, will likely lead to increased efforts to develop new technologies for the integrated production of ethanol, electricity, and chemical products from specialized biomass resources. Near-term markets exist for corn-ethanol and the co-firing of coal-fired power plants. By the middle of the 21st century, global energy consumption will more than double from the present rate. To meet this demand under potential worldwide limits on carbon dioxide emissions, cost-effective solar energy must be developed.8 At present consumption levels, the supply of carbon-based fuels will be suf- ficient to meet our energy needs for well over a century. However, as noted in both Professor Bell's and Professor Lewis' presentations, the anticipated growth in energy demand over the next century, combined with climate change concerns, will drive the increased use of alternative sources of carbon-neutral energy. While a number of potential sources of renewable energy show promise for meeting part of this increased demand, including wind, biomass, geothermal, and expanded use of hydroelectric sources, solar power is most likely to meet the largest portion of this need. However, in order for use of solar power to increase substantially over the 21 st century, new discoveries in photovoltaic and photochem~cal energy technologies must be made to reduce costs, increase conversion efficiency, and extend operating life. Advanced materials such as organic semiconductors and sem~conducting polymers are needed to reduce energy costs from photovoltaics and make them competitive for electric power and H2 generation. Current silicon- based photovoltaics are highly efficient but also very expensive. New technolo- gies are needed to bring costs down. New photovoltaic materials and structures with very low cost-to-efficiency ratios by lowering costs of fabrication, improv- ing the efficiency, or both will produce a step change in the use of photovoltaic technologies. For example, the use of grain boundary passivation with poly- crystalline semiconductor materials might lead to the replacement of expensive single-crystal-based technology. The development of new, inexpensive, and durable materials for photoelectrochemical systems for direct production of hydrogen and electricity generation will be one of the main factors that will enable broad application of solar power to meet future energy needs. Widespread use of new, renewable, carbon-neutral energy sources will require major breakthroughs in energy storage technologies.9 Alexis T. Bell, University of California, Berkeley, Nathan Lewis, California Institute of Technol- ogy, Ralph P. Overend, National Renewable Energy Laboratory, presentations at the Workshop on Energy and Transportation. 9Nathan Lewis, California Institute of Technology, Henry S. White, University of Utah, presenta- tions to the Workshop on Energy and Transportation.

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86 ENERGY AND TRANSPORTATION Development of these technologies is dependent, in part, on breakthroughs in the design of energy storage systems due to the intermittent nature of many forms of renewables. Batteries, whose basic design has remained relatively unchanged for over a century, need to be fundamentally reexamined, as they will play an important role in meeting future energy needs. For example, Professor White highlighted advances in nanotechnology and its use in three-dimensional electrochemical cells as offering the possibility of increased energy density com- pared to conventional battenes, but these advances are still in the early stages of development. In addition, fundamental research breakthroughs are needed on thin- film electrolytes in order to develop high-power-density batteries and fuel cells.~ For full public acceptance of nuclear power, issues such as waste disposal, reactor safety, economics, and nonproliferation must be addressed. Future energy consumption trends indicate the need for additional sources of carbon-neutral energy. No one source of power will be sufficient to meet all of the projected increase in future power needs. Dr. Baisden in her presentation noted that nuclear power offers a plentiful supply of energy that is free from local emissions and produces no carbon-based greenhouse gases. However, nuclear power is unique in that political considerations are as important as technical chal- lenges. One of the main technical challenges is waste management and disposal. Significant amounts of uranium can be reprocessed and reused in reactors, but this technology comes with significant concerns about nuclear proliferation and safety. Particularly in light of recent terrorist actions in the United States, the development of safe nuclear waste forms that not only will survive long-term repository storage but also allow secure transit to a repository remains an impor- tant pnonty. Another significant issue facing the United States is the growing shortage of nuclear technical expertise. This threatens the management of the nation's cur- rently installed nuclear capacity and certainly the development of the science and engineering needed to expand nuclear energy use in the future. The training situ- ation is dire in nuclear chemistry, radiochemistry, and nuclear engineenng. To address this shortage reinvestment in the education system will be required. TRANSPORTATION Vehicle mass reduction, changes in basic vehicle architecture, and im- provements in power trains are key to improved vehicle efficiency. The that present fuel cell systems are being piloted for distributed generation backup power. This may provide another source of energy storage. Patricia A. Baisden, Lawrence Livermore National Laboratory, Jiri Janata, Georgia Institute of Technology, presentations to the Workshop on Energy and Transportation.

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FUTURE CHALLENGES FOR THE CHEMICAL SCIENCES 87 development and use of new materials are crucial to improved fuel efficiency.l2 Dr. Sachdev noted in his presentation that reductions in the body mass of passenger vehicles will depend to a great extent on the successful integration of new light weight materials. The dual needs in these applications for materials that are both lightweight and strong continue to present challenges and oppor- tunities in the chemical sciences. The development of new polymers and nanocomposite materials will play an increasing role in vehicle mass reduction. The combination of high strength and light weight makes them ideal for many of these applications. Along with new materials, manufacturing and recycling processes will have to be developed that are both cost effective and environmentally effective. As with the development of new catalysts, effective new materials benefit from a thorough understanding of structure/property relationships. This involves multiscale modeling and experimental efforts in surface science, including morphology. Enabling the use of new materials will also require extensive devel- opment of new nano- and microfabrication techniques, including biodirected or self-assembly syntheses. Cost remains one of the main factors that determine both the need and the acceptance of new materials for applications in energy and transportation. In addition, passenger safety, which may be affected by the development of more lightweight vehicles, must also be taken into consideration. The imperative of low-cost, high-performance materials in the automotive industry will be driven by future environmental and CAFE regulations. Reduced material cost is key to widespread use of the proton exchange membrane (PEM) fuel cellos As with other materials challenges, selective and energy-efficient separations are a highly desirable characteristic in many areas of energy and transportation research and engineering. Development of low-temperature, corrosion-resistant, thin membranes will further PEM development. However, development of new catalytic materials to replace the very expensive platinum in today's design is the most critical need.~4 Low-cost materials in fuel cells will be one of the key decid- ing factors in whether the United States readily transitions to a hydrogen economy. i2James R. Katzer, ExxonMobil, Kathleen C. Taylor and Anil Sachdev, General Motors Corpora- tion, presentations to the Workshop on Energy and Transportation. i3John R. Wallace, Ford Motor Company, presentation to the Workshop on Energy and Transpor- tation. i4A complementary goal to replacing expensive Pt in today's design is reduced Pt loading. to develop catalysts with

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88 ENERGY AND TRANSPORTATION The lack of hydrogen generation, transportation, and storage infrastruc- ture presents one of the main challenges to introducing hydrogen into the mass market as a transportation fuel and energy carriers Effective hydrogen management and creation of the needed infrastructure will both be key to widespread adoption of hydrogen fuel cells to meet the country's energy needs for transportation and power. The challenges are great. New-generation technology is needed in the short- to midterm for hydrocarbon- based local refueling sites. In the long term, science and technology will have to be developed to generate hydrogen from carbon-free sources such as water, or at a minimum from carbon neutral sources. Whether this new energy source is based on nuclear, solar, or something that remains undiscovered, it will be one of the largest technical challenges the chemical sciences has ever undertaken. Another significant challenge to effective hydrogen management is the devel- opment of efficient hydrogen storage, both onboard the vehicle and at a hydrogen generation facility. As with many other challenges, effective hydrogen storage is a crosscutting one that will require breakthroughs in a number of research areas. Progress is being made with metal hydrides and carbon nanotubes but a com- mercial solution is a long way off. New materials will be key. These technical challenges regarding hydrogen presently hinder widespread commercial use of hydrogen fuel cell technology for transportation and power. Until these challenges are met, it is unlikely that fuel-cell-powered vehicles will ever make up a significant portion of the passenger vehicle market. CROSSCUTTING Development of new, less expensive, more selective chemical catalysts is essential to achieving many challenges in both energy and transportation. Catalysts are expected to play a role in virtually every challenge where chemi- cal transformations are a key component. The development of new catalysts to solve challenges in energy and transportation will require the ability to design catalysts for specific needs. Utilization of new materials, nanotechnology, new analytical tools, and advanced understanding of structure/property relationships will create major catalytic advances. One of the major areas where these advances are needed is in controlling nitrogen oxide emissions from lean-burn engines and nitrogen oxide from coal power plants. Others are increased energy efficiency of fossil fuel processes, delivery of chemically designed fuels to new vehicle power systems, and direct conversion of natural gas into liquid fuels and Hydrogen-2. Another is the discovery of less expensive catalysts for the electroreduction of i5Venki Raman, Air Products and Chemicals, presentation to the Workshop on Energy and Transportation.

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FUTURE CHALLENGES FOR THE CHEMICAL SCIENCES 89 oxygen and the oxidation of fuels that can play an important role in fuel cells. As noted earlier, the global supply of Pt is insufficient to support a fuel cell transpor- tation fleet using known electrode technology. Catalysts for promoting oxygen and hydrogen evolution from water, are also important in the design of photo- electrochemical systems. CONCLUSION Chemical research is required for substantial breakthroughs in the areas of energy and transportation. For example, the discovery of new catalysts, materials, and photoelectrochemical systems will require fundamental research in chemistry. Many of the challenges described above will only be met by effective interaction of the chemical sciences with other disciplines. In light of this, it is important to maintain a comprehensive and integrated approach to meeting these challenges. Also, chemical scientists should interact with researchers in other disciplines during the early stages of research planning in order to set and maintain this integrated approach. While it is not possible for chemical scientists to have a comprehensive knowledge of other disciplines, it is necessary for those in the chemical sciences to have a broad understanding of the nature of the interface in order for its impact to be fully appreciated. When working to address these challenges, chemical scientists must always be watchful for unintended consequences. The energy and transportation sectors, being so closely tied to environmental impacts, must be particularly aware of solutions that may carry potentially negative impacts. Finally, in addition to sci- entific concerns, social, political, and economic impacts must be taken into account when addressing these challenges. Public perception and acceptance are key to many developments in energy and transportation and, as a result, should be considered when chemical scientists attempt to meet these challenges. Because this report is based on only a 2-day workshop, details of chemical science research and engineering programs need to be further developed. The workshop's organizing committee suggests that the National Research Council pursue development of these detailed programs because of the importance of energy and transportation to our nation.

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