Alexis T. Bell
University of California at Berkeley
Tobin J. Marks
Considerable international concerns exist about global climate change and its relationship to the growing use of fossil fuels. Carbon dioxide is released by chemical reactions that are employed to extract energy from fuels, and any regulatory policy limiting the amount of CO2 that could be released from sequestered sources or from energy-generating reactions will require substantial involvement of the chemical sciences and technology R&D community.
Much of the public debate has been focused on the question of whether global climate change is occurring and, if so, whether it is anthropogenic, but these questions were outside the scope of the workshop, which instead focused on the question of how to respond to a possible national policy of carbon management. Previous discussion of the latter topic has focused on technological, economic, and ecological aspects and on earth science challenges, but the fundamental science has received little attention. The workshop was designed to gather information that could inform the Chemical Sciences Roundtable (see Appendix C) in its discussions of possible roles that the chemical sciences community might play in identifying and addressing underlying chemical questions.
The first session was devoted to setting the context of the workshop—the broad view of the problem, including its magnitude; the motivations for a carbon management policy; the interplay between public, private, and government sectors in the areas of policy; and the strategic issues and options associated with energy production and use, as well as CO2 separation and sequestration.
James Edmonds, from Pacific Northwest National Laboratory, presented the motivations for carbon management (see Chapter 1). He articulated the theme that carbon management may prove to be one of the greatest challenges of the twenty-first century since, driven by climate change issues, the global energy production and utilization system will have to undergo radical transformation during this period. He suggested that the need to stabilize the atmospheric CO2 concentration implies that net anthropogenic carbon dioxide emissions—the contributions to the ocean-atmosphere in excess of the CO2 uptake by other parts of the carbon cycle—must decline to zero. This technological premise, in conjunction
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Page 1 Summary Alexis T. Bell University of California at Berkeley and Tobin J. Marks Northwestern University Considerable international concerns exist about global climate change and its relationship to the growing use of fossil fuels. Carbon dioxide is released by chemical reactions that are employed to extract energy from fuels, and any regulatory policy limiting the amount of CO2 that could be released from sequestered sources or from energy-generating reactions will require substantial involvement of the chemical sciences and technology R&D community. Much of the public debate has been focused on the question of whether global climate change is occurring and, if so, whether it is anthropogenic, but these questions were outside the scope of the workshop, which instead focused on the question of how to respond to a possible national policy of carbon management. Previous discussion of the latter topic has focused on technological, economic, and ecological aspects and on earth science challenges, but the fundamental science has received little attention. The workshop was designed to gather information that could inform the Chemical Sciences Roundtable (see Appendix C) in its discussions of possible roles that the chemical sciences community might play in identifying and addressing underlying chemical questions. OVERVIEW: ECONOMICS AND OTHER DRIVERS FOR CARBON MANAGEMENT The first session was devoted to setting the context of the workshop—the broad view of the problem, including its magnitude; the motivations for a carbon management policy; the interplay between public, private, and government sectors in the areas of policy; and the strategic issues and options associated with energy production and use, as well as CO2 separation and sequestration. James Edmonds, from Pacific Northwest National Laboratory, presented the motivations for carbon management (see Chapter 1). He articulated the theme that carbon management may prove to be one of the greatest challenges of the twenty-first century since, driven by climate change issues, the global energy production and utilization system will have to undergo radical transformation during this period. He suggested that the need to stabilize the atmospheric CO2 concentration implies that net anthropogenic carbon dioxide emissions—the contributions to the ocean-atmosphere in excess of the CO2 uptake by other parts of the carbon cycle—must decline to zero. This technological premise, in conjunction
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Page 2with the need to carry it out in a cost-effective manner, would have several important near-term implications for the character of efficient policy development. Using the premises that there are sufficient economic fossil fuels to last for the next century and that continued economic development will ensure a continued growth in energy demand, he described existing patterns for world use of low-cost fossil fuel and identified the need for a portfolio of technologies that will change those patterns. He argued that investments to develop those technologies and their associated infrastructure will require funding a full spectrum of R&D, coordinated among many nations and with the participation of both public and private sectors. However, he showed that global energy R&D has declined over the last 15 years. In his view, public policy will play an important role in signaling the need for new technologies and in facilitating their development and deployment. David Thomas of BP Amoco discussed various options for CO2 mitigation and presented the approach that BP has taken (see Chapter 2). He presented examples of methods for reducing energy consumption from various manufacturing processes practiced by BP and described possible separation technologies for the CO2 that is emitted. Separation of CO2 could occur early, in capture from natural gas, or much later, from combustion processes. He also described options for storing CO2 safely, particularly in geological formations. Thomas reiterated Edmonds's point that mitigation techniques must be cost-effective if they are to be widely adopted. Brian Flannery of ExxonMobil (see Chapter 3) pointed out that concerns about anthropogenic emissions of CO2 and their possible effect on climate change have led to policy proposals that would dramatically restrict future emissions. He revisited some of the issues discussed by Edmonds and provided a historical perspective on energy use, energy decarbonization and energy efficiency. His talk emphasized the magnitude of the problem and time scale for penetration of new technologies. He presented several scenarios that could lead to CO2 stabilization at various levels over the next century, noting that the associated social, environmental, and economic costs would be sensitive to the availability and performance of new technologies. He emphasized that effective implementation of any new energy technology would require extensive infrastructure development, and that any policy requiring stabilization of atmospheric CO2 concentrations would depend on development and widespread global implementation of technologies that are not commercially available today. He identified a twofold chemical R&D focus that would enhance our ability to assess the extent and consequence of climate change and would contribute to the development of appropriate advanced technologies. Opportunities for carbon emissions control in the electric power industry were addressed by John Stringer of the Electric Power Research Institute (see Chapter 4). He emphasized that the problem is very large, that the dominant worldwide generation fleet will increasingly consist of fossil fuel-fired thermal stations, and that no clearly superior methods for carbon management currently exist. On that basis, he concluded that research on multiple candidates—including combustion systems, nuclear energy, and renewable energy—will be critically important. He highlighted the importance of having a long-range roadmap for planning the supply of electricity for the next 50 years, since most of the world's current generating capacity would be replaced during that period. He described options for reducing CO2 emissions associated with power generation and discussed the issues associated with the principal fuels: petroleum, natural gas, and coal. He summarized opportunities for CO2 capture, particularly for coal-fired plants and identified the issues associated with alternative sequestration strategies. Finally, he reiterated Edmonds's point that a commitment to emissions mitigation should not be made too soon, lest the approach prove unsuitable or unachievable at a reasonable cost. In the panel discussion following the first session, an effort was made to focus on identifying a research agenda in chemical sciences and engineering that would be aimed at reduction of CO2 emissions. Nevertheless, the majority of the discussion concerned the economics of carbon mitigation, and
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Page 3 participants reported that simple steps, such as fuel switching, are occurring. Several participants expressed the need for creative and innovative research to lay the foundations for the next generation of technology—as argued by Brian Flannery, current approaches appear unlikely to succeed in the near term. SCIENCES R&D ISSUES IN MANAGING PRODUCED CARBON DIOXIDE The presentations in the second session of the workshop were centered on the efficient use of carbon resources that could lead to a reduced contribution to the CO2 pool. The presentations covered a number of perspectives, ranging from laboratory research to industrial policy. Strategies suggested to accomplish the goals ranged from a system of renewable fuels that could avoid CO2 emissions to a system that would rely on fossil fuels with separation and sequestration of the CO2. Carol Creutz of Brookhaven National Laboratory reviewed the use of carbon dioxide as a starting material for organic synthesis, for potential industrial chemical applications, and as a feedstock for fuel production (see Chapter 5). She put this in perspective by comparing the estimated net anthropogenic increase of 13,000 million tons of CO2 added to the atmosphere annually with the annual total of 110 million tons transformed into chemicals—mainly urea, salicylic acid, cyclic carbonates, and polycarbonates. She suggested that increased use of CO2 as a starting material would be desirable, potentially producing a positive—although small—impact on global CO2 levels. Use of supercritical CO2, a hydrophobic solvent that can replace organic solvents in a number of applications, could consume additional amounts. Reactive use of CO2 is limited by the fact that it is very stable, and energy must be supplied to drive most transformations. Dr. Creutz suggested that renewable energy sources be considered in driving CO2 utilization, such as direct hydrogenation to CH3OH or CH4 via a variety of routes, including photochemistry. She concluded her presentation by identifying several areas of ongoing and future research directions that could lead to CO2 utilization in new polymers. James A. Spearot of General Motors discussed advanced engine and fuel systems for minimizing CO2 generation (see Chapter 6). The goal of the automotive industry is to respond to the global demand for the freedom provided by modern transportation technology and thereby achieve sustainable “auto-mobility.” He suggested that for society to continue to enjoy the benefits of personal mobility, we will need long-term energy forms that are renewable and vehicle technologies that have zero impact on the ambient environment. He discussed reduction of carbon emissions by improving the efficiency of vehicles and propulsion systems—through the auto industry-government program known as the Partnership for a New Generation of Vehicles (PNGV). Various improvements in fuel economy might be obtained through use of lightweight bodies, advanced combustion technologies, and advanced transmissions. In addition to combustion engines, fuel cell-powered vehicles operating with either gasoline or hydrogen could provide significant efficiency improvements and CO2 emission reductions, but the penetration of hydrogen-fueled vehicles would require the development of a hydrogen infrastructure. Spearot reported that significant progress has been made, but he cautioned that future emission standards, particularly for NOx and particulates, might limit utilization of some of the near-term advanced technologies. Advanced propulsion systems also will require advanced fuel compositions, and the use of hydrogen—the ultimate fuel—will require significant advances in on-board hydrogen storage as well as the development of a fuel delivery infrastructure. Spearot also suggested that biomass-based ethanol could represent a CO2 conservation option, but this was challenged by Flannery, who earlier had presented a different perspective (see Chapter 3). John Turner of the National Renewable Energy Laboratory discussed renewable energy storage, generation, and utilization (see Chapter 7). He proposed that advanced renewable energy systems may
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Page 4 provide the basis for a sustainable energy supply without net anthropogenic emission of CO2. He argued that large-scale implementation of renewable energy technologies could eliminate the need for CO2 sequestration by reducing the use of—and ultimately eliminating the need for—fossil-based energy production. The renewable energy systems he discussed include photovoltaics, solar thermal (electric and thermal), wind, biomass (plants and trees), hydroelectric, ocean, and geothermal. He described the impressive growth of wind power, particularly on wind farms. He emphasized the need for energy storage technologies that would overcome the intermittent nature of several of the renewable energy sources, as well as the need for basic research in all aspects of renewable energy generation. One option he emphasized for energy storage was electrolysis for renewable hydrogen generation. David W. Keith of Carnegie Mellon University ( Chapter 8) spoke about industrial carbon management to permit the continued use of fossil fuels for energy. Industrial carbon management links processes for capturing the carbon content of fossil fuels while generating carbon-free energy products such as electricity and hydrogen and sequestering the resulting carbon dioxide. The energy content of the fossil fuels would first be separated from their carbon content in one of three separation schemes: post-combustion capture (combustion in air followed by removal of CO2 from the combustion products), oxyfuel (separation of oxygen from air followed by combustion in pure oxygen and CO2 capture), and pre-combustion decarbonization (with a first step of reforming the fuel to produce hydrogen and CO2 followed by capture of the CO2). The third alternative has the advantage that a power plant could sell zero-CO2-emission hydrogen for a hydrogen infrastructure. In all cases, CO2 sequestration is the substantive challenge. For such technologies Keith estimated the cost of electricity to be about 2-3 cents per kilowatt-hour more than from current technologies, roughly comparable with the cost of electricity via wind, biomass, or nuclear power. He argued that the advantage of industrial carbon management is its fit with the existing infrastructure for power generation and distribution, and he suggested that a carbon tax might provide the economic driver to accelerate this approach. The discussion following this session brought up the issue of biological sequestration of carbon. David Thomas questioned whether regional politics might influence national decisions on sequestration, and David Keith suggested that biological sequestration could have a significant short-term impact. There was extensive discussion among the panel and participants on the costs and challenges for hydrogen storage and renewable energy sources. EFFICIENT UTILIZATION OF CARBON RESOURCES The third session of the workshop was devoted to the efficient utilization of carbon resources. Two perspectives were presented: the first was devoted to efficient utilization of hydrocarbon resources in “traditional” chemistry, and the second focused on using plants as the feedstock for making chemicals and polymers. Leo Manzer of DuPont ( Chapter 9) described how selective industrial catalytic oxidation could be used to reduce carbon losses from processes for making olefins and oxygenated products. He began by noting that catalytic oxidations usually exhibit selectivities for desired products of less than 90% and account for much of the CO2 released from chemical processes. He illustrated how reductions in CO2 emissions could be achieved by several means, including a two-step oxidation process in which a hydrocarbon is oxidized anaerobically by the catalyst and the partially reduced catalyst is then reoxidized in a separate step. Such processes have been found to yield higher product selectivities than those obtained from aerobic oxidation. Higher product selectivities can also be achieved by using alternative oxidants such as hydrogen peroxide (H2O2) and nitrous oxide (N2O), but the cost of these oxidants would have to be reduced significantly before they could become commercially attractive compared to
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Page 5 oxygen. He described the potential use of hydrogen-oxygen mixtures for selective oxidation but noted that serious safety issues would have to be addressed. Manzer also showed how creative new catalytic technologies could be used to achieve higher product yields and reduced CO2 emissions. He also suggested that the use of CO2 as a mild oxidant is an interesting new development to be pursued. However, he argued that it is not economical to replace existing chemical plants, so financial incentives would be needed to commercialize improved technologies. The theme of efficient utilization of hydrocarbon resources was continued by Harold Kung from Northwestern University ( Chapter 10), who noted that oxidation catalysts exhibiting higher selectivities are needed for processes such as the oxidative dehydrogenation of alkanes to olefins and the selective oxidation of alkanes to oxygenated products. Kung observed that the hydrogen-to-carbon ratio of most petrochemicals is higher than that in crude oil, so hydrogen must be added to make these products. Since hydrogen is produced by the steam reforming of methane, a process that generates CO2, reducing the consumption of hydrogen would lead to a reduction in CO2 emissions. He illustrated several alternatives by which oxygenated products might be produced to minimize the loss of hydrogen as water, and he urged the development of novel processes that minimize the consumption of energy. For example, if acetic acid could be produced by direct heterogeneous carbonylation of methanol, then the energy required to separate acetic acid from the water solvent, a considerable component of the energy consumption, could be avoided. Opportunity also exists to develop new strategies for reforming liquid fuels to produce hydrogen for fuel cells. The production of polylactic acid (PLA) from cornstarch was addressed by Patrick Gruber of Cargill Dow (see Chapter 11). PLA was chosen as a target for process development because it exhibits adequate performance as a commodity polymer and would command a reasonable market price. Since CO2 is fixed in crops to make starch, the starting material for PLA comes from a renewable source. Gruber addressed the market opportunities and potential for PLA and the relationship between the production of PLA and the net consumption or production of CO2. Currently there is market demand for PLA in three areas: fibers, packaging, and chemical products. Long-range opportunities also exist for converting lactic acid, the monomer for PLA, into a variety of commodity and specialty chemicals, as well as polymers other than PLA. Gruber projected that in its first year of operation, the cradle-to-pellet emission of CO2 for the production of PLA would be comparable to that for the production of polypropylene, but with further process development, PLA production would become a net consumer of CO2. His overall conclusion was that products made from renewable resources, such as PLA, offer advantages over the petrochemical-based products that they would replace, and he argued that the development of successful renewable resource-based products will require the skillful combination of expertise in fermentation and biotechnology with that in more conventional chemistry and polymer science. John Frost of Michigan State University described the production of chemicals from plants (see Chapter 12). He began with the observation that virtually all commercial chemicals are synthesized from petroleum feedstocks; very few are isolated as natural products from plants or produced microbially from plant feedstocks. He argued that there is enormous opportunity for the production of chemicals from renewable feedstocks and, hence, a net consumption of CO2, since plants can be thought of as immobilized forms of CO2. His strategy is based on the development of new syntheses and synthetic methodologies compatible with the use of water as the reaction solvent. Also critical would be effective interfacing of microbial catalysis with chemical catalysis and the discovery and use of genes encoding biosynthetic enzymes. Frost illustrated the opportunities for his approach with a number of examples. Shikimic acid is a key intermediate in the synthesis of Tamiflu, an effective anti-influenza drug, but is available in only limited quantities. He showed that shikimic acid could be synthesized from readily available starting materials via a biosynthetic route. Examples were presented also of how one might
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Page 6 synthesize hydroquinone and adipic acid from glucose. Frost ended his presentation with a call for chemists to view construction of microbial catalysts as an activity every bit as central to chemical synthesis as the development of inorganic and organometallic catalysts. Both Frost and Gruber emphasized the need for broadly trained scientists who understand chemistry and can move across disciplinary boundaries. The panel discussion following the third session began with the question of how the issues presented by the speakers could be translated into a research agenda for the chemical sciences. In response to questions about the use of computer modeling, the speakers indicated that this was an important component of industrial research, but it is just one component. Several participants asked if the increasing national emphasis on biologically related research might undermine progress in the physical sciences. Manzer and Gruber indicated that industry needs scientists who can work across the boundaries of the disciplines, and others suggested that future success in carbon management would require broad efforts at understanding the chemistry of CO2 in both biological and geological contexts. The contributions in this report from the workshop speakers indicate that a program of carbon management would pose enormous challenges. Several speakers described ways that R&D could reduce the amount of CO2 that is generated by chemical industry. While it was noted that this is only a small fraction of the total amount of anthropogenic CO2 (see the discussion following Chapter 2), reductions could be economically important to the chemical industry if a carbon management policy were to be established. Several speakers pointed to ways that R&D in the chemical sciences and engineering might lead to reduction of emissions by the power and transportation sectors, which are responsible for the preponderance of CO2 generated by human activity.