5
Novel Niches

INTRODUCTION

The objective of the Novel Niches sessions at the workshop was to explore potentially practical niche technologies for CO2 conversion to useful products (including moderate to large-scale production of plastics and fuels), for CO2 removal and sequestration from flue gases, for its removal from the atmosphere and storage, and for noncarbon energy production processes other than “conventional” energy technologies such as nuclear, biomass, and various renewable energy technologies. Important opportunities may exist either for the development of a novel concept of sequestration or for ways of applying new science and technology from areas far removed from current CO2 sequestration efforts. These opportunities may occur in CO2 separation, CO2 capture, CO2 storage, CO2 recycling, or CO2 conversion into useful commercial products.

For the most part, the discussions in the Novel Niches sessions concentrated on novel concepts involving CO2 recycling and CO2 products as well as on new scientific and technological means to achieve these goals. Also, the notion of a “niche” opportunity was thought of as an area that might contribute to ameliorating at least a small part of the carbon management issue but would not necessarily be the major approach to managing or “solving” the carbon problem (i.e., not a “silver bullet”). Thus, if a particular niche application could address the carbon problem in some small degree, the application of several niche technologies could make a significant contribution.

One main thrust of discussion concerned the general area of biomass production and use. Ideas were put forth on a number of possible new ways to enhance CO2 uptake from the atmosphere by manipulating plant genetics, enzymes, microbes, cyanogens, and catalytic pathways.

Another area of potential advancement is that of the design of advanced catalysts (using nanotechnology) to allow carbon sequestration on an accelerated, less energy-intensive basis by promoting various carbon-based chemical reactions. The potential for new CO2 separation technologies involving absorption on advanced-technology activated fibers was proposed as a way to reduce the energy cost of CO2 capture and regeneration. (Also see Chapter 2, “Advanced Separations Techniques.”)

Finally, the Novel Niches subgroup noted that, although this is not a technology related to carbon management, more accurate measurements of carbon fluxes between terrestrial, oceanic, and atmospheric reservoirs would enable better understanding of the carbon cycle. Of particular merit would be a better understanding of the potential to optimize the percentage of energy and carbon capture of the total energy and carbon flux in the immediate vicinity of growing terrestrial and marine systems. An enhanced understanding of the carbon cycle would offer the potential for advances in carbon flux manipulation that would improve opportunities for terrestrial and marine carbon sequestration.

The wide-ranging discussions of the Novel Niches sessions were organized in four areas in which there appear to be opportunities for carbon management if breakthroughs, improved scientific understanding, and new technology applications are developed. The four



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Novel Approaches to Carbon Management: Separation, Capture, Sequestration, and Conversion to Useful Products - Workshop Report 5 Novel Niches INTRODUCTION The objective of the Novel Niches sessions at the workshop was to explore potentially practical niche technologies for CO2 conversion to useful products (including moderate to large-scale production of plastics and fuels), for CO2 removal and sequestration from flue gases, for its removal from the atmosphere and storage, and for noncarbon energy production processes other than “conventional” energy technologies such as nuclear, biomass, and various renewable energy technologies. Important opportunities may exist either for the development of a novel concept of sequestration or for ways of applying new science and technology from areas far removed from current CO2 sequestration efforts. These opportunities may occur in CO2 separation, CO2 capture, CO2 storage, CO2 recycling, or CO2 conversion into useful commercial products. For the most part, the discussions in the Novel Niches sessions concentrated on novel concepts involving CO2 recycling and CO2 products as well as on new scientific and technological means to achieve these goals. Also, the notion of a “niche” opportunity was thought of as an area that might contribute to ameliorating at least a small part of the carbon management issue but would not necessarily be the major approach to managing or “solving” the carbon problem (i.e., not a “silver bullet”). Thus, if a particular niche application could address the carbon problem in some small degree, the application of several niche technologies could make a significant contribution. One main thrust of discussion concerned the general area of biomass production and use. Ideas were put forth on a number of possible new ways to enhance CO2 uptake from the atmosphere by manipulating plant genetics, enzymes, microbes, cyanogens, and catalytic pathways. Another area of potential advancement is that of the design of advanced catalysts (using nanotechnology) to allow carbon sequestration on an accelerated, less energy-intensive basis by promoting various carbon-based chemical reactions. The potential for new CO2 separation technologies involving absorption on advanced-technology activated fibers was proposed as a way to reduce the energy cost of CO2 capture and regeneration. (Also see Chapter 2, “Advanced Separations Techniques.”) Finally, the Novel Niches subgroup noted that, although this is not a technology related to carbon management, more accurate measurements of carbon fluxes between terrestrial, oceanic, and atmospheric reservoirs would enable better understanding of the carbon cycle. Of particular merit would be a better understanding of the potential to optimize the percentage of energy and carbon capture of the total energy and carbon flux in the immediate vicinity of growing terrestrial and marine systems. An enhanced understanding of the carbon cycle would offer the potential for advances in carbon flux manipulation that would improve opportunities for terrestrial and marine carbon sequestration. The wide-ranging discussions of the Novel Niches sessions were organized in four areas in which there appear to be opportunities for carbon management if breakthroughs, improved scientific understanding, and new technology applications are developed. The four

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Novel Approaches to Carbon Management: Separation, Capture, Sequestration, and Conversion to Useful Products - Workshop Report areas are (1) biomass management, (2) catalytic and/or photolytic CO2 reduction, (3) biocatalysts for CO2 binding and reduction, and (4) technology opportunities. The following sections describe the basic concepts, discuss their potential significance, and indicate areas in which research presents opportunities for breakthroughs. BIOMASS MANAGEMENT Terrestrial sequestration of carbon by biomass production is an approach for sequestering significant amounts of CO2. Sequestration through biomass offers the opportunity for CO2 to be recycled through fuel utilization or value-added products or for CO2 to be directly sequestered. Although biomass production systems currently exist, advances in the utilization of biomass for sequestration could have a significant impact on the adoption of this technology, since biomass processes offer the prospect of obtaining a high-concentration CO2 stream from the processing of the methane or higher-molecular-weight compounds. These feedstocks would arise from aerobic or anaerobic biodigestion of biomass, gasification of biomass with subsequent chemical processing, or extraction of oils or solids from biomass for direct use or subsequent chemical processing. The products that could result from biomass-based processes include useful fuels such as methane, liquid ketones for hydrogenation into transportation fuels, and novel cellulose sheets. In addition, biomass is a possible means of producing a condensed phase of CO2 that could be sequestered directly in the ground leading to a net removal of carbon from the atmosphere. Suggestions of novel means of drastically reducing the capital cost of a biomass plant were presented. This area of biomass management is of importance for the following reasons: Research directed at novel approaches for increasing biomass production, improving processing, and enhancing utilization and sequestration would make a significant contribution to enhancing this technology. Recent advances in modern biology, including advances in genomic sciences, provide new and promising approaches for enhancing biomass production, enhancing biomass processing, and producing novel products. Research Opportunities Areas in which research presents opportunities for breakthroughs in biomass management include the following: There is the opportunity to capitalize on advances in genomic science to develop a basic understanding of the biology of plants, which could lead to the development of approaches that will have a significant impact on biomass production. Research would include studies of basic mechanisms of CO2 fixation, manipulation of plant respiration, altering the way in which carbon is partitioned to different parts and structures of plants, and enhancement of nitrogen use efficiency. Improvements are needed in the processing of biomass into either fuel or products, including opportunities offered by genomics, innovations in low-cost fermentation processes, or other conversion methods (e.g., thermal-chemical

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Novel Approaches to Carbon Management: Separation, Capture, Sequestration, and Conversion to Useful Products - Workshop Report conversion). Particularly needed are improvements—specifically reductions—in the following: The capital cost and complexity of the equipment, particularly that arising from the need for biological isolation, The life-cycle energy required to produce fuels or products, The amount of non-raw-material inputs (e.g., nutrients), and The fraction of carbon that is respired versus that converted to products. Biomass also offers the opportunity to sequester CO2. It is possible that novel approaches for innovative sequestration processes could be developed and integrated with these methods. In particular, major opportunities exist for using microbes for enhanced, low-cost cellulose production with polymeric materials as substitutes for petroleum-based plastics. CATALYTIC AND/OR PHOTOLYTIC REDUCTION OF CO2 The basic notion of catalytic and/or photolytic reduction of CO2 is to use inorganic catalysis or photosynthetic processes, possibly including photoelectric effects, to directly reduce CO2 and water to form fuels such as methane (which could be used as fuel for heating and/or transportation) or higher-value carbon compounds (e.g., methanol, ketones, aldehydes, and acids) in a process with low capital and operating costs. Direct sunlight is envisioned as the source of the energy for the CO2 reduction. The CO2 may be in concentrated form as a pressurized high-density fluid from capture and transport processes, or it may be highly dilute as in the atmosphere. In a virtually all-electric economy, many forms of direct manufacture of electricity including photovoltaic energy would have significant advantages and would significantly reduce the emissions of carbon dioxide. However, the photolytic reduction of carbon dioxide might still be used to make starting materials from carbon and to make carbon-based fuels to whatever extent they are used. Carbon-based fuels would have significant storage and transportation advantages over electricity. The application of a large-scale, single-cell photosynthetic culture has new potential for CO2 utilization through the body of research carried out in the last several decades. Single-cell culture processes could be improved by employing more effective reactor designs and advanced light-capturing technologies. The production of single-cell microorganisms for useful polymeric products offers potential for a new CO2-based utilization. Successful research in this area is of importance for the following reasons: Present photovoltaic devices demonstrate solar energy collection efficiencies per unit of area that are greater than that of photosynthesis. It is recognized that this greater collection efficiency comes at the expense of a much greater capital cost. That may well need to become the focus of the research. Success would lead to a fuel or higher-value hydrocarbon that could be used instead of fossil-based hydrocarbons in transportation fuels or chemical feedstocks. The technical, environmental, and economic challenges of sequestration would be avoided. The production of a hydrocarbon fuel or higher-value hydrocarbon would enable the equivalent of storage and transportation of sunlight energy, which is otherwise

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Novel Approaches to Carbon Management: Separation, Capture, Sequestration, and Conversion to Useful Products - Workshop Report discontinuous and not necessarily available on an as-needed basis at a particular point of use. Research Opportunities Areas in which research presents opportunities for breakthroughs in the catalytic and/or photolytic reduction of CO2 include the following: Inorganic catalysis studies leading to the right combination of materials and surface interactions to accomplish CO2 reduction while supplying the necessary energy input at the surface and not in the bulk phase, and application of nanotechnology surface construction techniques to achieve sufficient selectivity; Devices that have low capital cost that capture sunlight energy and simultaneously channel that energy only to the catalytic surface; Prevention of reoxidation of the produced hydrocarbon back to CO2 in the presence of the coproduced oxygen; and Photosynthetic microbial fixation of CO2 at the surface with production of hydrocarbons, followed by subsurface sequestration of waste biomass through nucleation of metal carbonates. BIOCATALYSTS FOR CO2 BINDING AND REDUCTION A wide variety of microorganisms and their enzymes perform diverse chemical reactions that can be used for the binding and reduction of CO2 from the atmosphere. Two new scientific developments in this field offer the opportunity to dramatically enhance the binding and affinity for CO2 and the rate of reduction of CO2 into an array of useful biochemicals. First, a wide variety of extremophiles (i.e., microbes that can grow at either high pH or low pH, high temperature or low temperature, at high salt, or that catabolize unusual substances such as CO, or metal salts) have been discovered. These organisms produce “extremozymes” that are stable and active under harsh process conditions. Second, the advent of molecular biological tools enables the biotechnologist not only to clone and overexpress these proteins in industrial hosts but to utilize site-directed and random mutagenesis to dramatically enhance the affinity of CO2 binding and the rate of its conversion into useful biochemicals. Furthermore, the newest technology that has emerged enables the custom design of a combined CO2-binding and CO2-reducing enzyme system using protein fusion technologies. A more efficient and rapid conversion of atmospheric CO2 into a variety of reduced biochemicals can enable the following: The utilization of these extremophile genes and enzymes in biomass systems or biofilter systems (e.g., immobilized microbe or enzyme bioreactors) to consume CO2 from the atmosphere or smokestacks or flue gases; The production of plant polymers from CO2 such as cellulose, starch, and polyesters for application to high-volume markets; and

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Novel Approaches to Carbon Management: Separation, Capture, Sequestration, and Conversion to Useful Products - Workshop Report The production of a wide variety of higher-value biochemicals by microbial CO2 reduction, including ethanol and other organic alcohols, amino acids, succinic acid and other organic acids, and other polyesters. Research Opportunities Areas in which research presents opportunities for breakthroughs in biocatalysts for CO2 binding and reduction include the following: Characterization of CO2 binding and reducing enzymes and their genes from extremophiles; Enhancement of enzymatic CO2 binding efficiency, CO2 reduction rates, enzyme stability, and acceptor substrate range by protein engineering techniques; Design of customized CO2 binding and reduction biocatalysts composed of multiple enzymes using protein fusion technologies; and Investigation of opportunities offered by genomics and proteomics to improve microbial processes. TECHNOLOGY OPPORTUNITIES There are niche opportunities to diversify and improve major technologies for CO2 management. These range from CO2 separation methods to accelerating the rate of sequestration or conversion of CO2 to other materials. Niche technologies will expand and strengthen the portfolio of methods currently under development and offer potential for substantially higher efficiencies in fossil fuel use. The discussions in the Novel Niches sessions identified research opportunities with significant potential that are described below. One area identified, engineering systems analysis for optimum CO2 reduction or sequestration, is a crosscutting opportunity and is discussed in Chapter 6, Crosscutting Issues. Research Opportunities The following niche technologies do not easily fit in any of the previous categories but may offer potentially large reductions in CO2 emissions: Separating carbon and hydrogen from coal. This approach covers processes and concepts to differentiate solid carbon from hydrogen while avoiding coal combustion. The hydrogen would be used as fuel while the carbon would be used to produce carbon-based building and structural materials—for example, to substitute for cement and steel. Separation could be accomplished by coking, for example. The separated carbon could then be used to produce high-tensile-strength material, such as carbon fiber beams for a steel substitute, or high-compression material formed into carbon bricks for building and structural construction.

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Novel Approaches to Carbon Management: Separation, Capture, Sequestration, and Conversion to Useful Products - Workshop Report “Zero” emission processing. This technology complements the process developments occurring in DOE’s Office of Fossil Energy Vision 21 Program by looking for new, closed-loop fuel production/electricity production cycles that involve essentially no pollutant emissions. Direct flue gas treatment. This area is crucial for application to commercial fossil-fuel combustion processes. There are methods that should be explored, including flue gas biofiltration or advanced CO2 hydrate formation. (Also see Chapter 2, “Advanced Separations Techniques.”) Removal of CO2 from ambient air. Alternative methods for low-cost, efficient removal of CO2 from the air may be feasible using biofiltration combined with wind-induced airflow through the filter. This area merits exploration as an alternative to biomass production. (Also see Chapter 2, “Advanced Separations Techniques.”)