8. BIOLOGICAL CARBON SEQUESTRATION RESEARCH AND TECHNOLOGY

The burning of fossil fuels adds carbon to the atmosphere, principally in the form of carbon dioxide, and the potential environmental impacts have made carbon management an international concern.  There is increasing national and international interest in enhancing natural mechanisms to slow the rate of atmospheric CO₂ increase, or in developing new approaches to mitigate the current atmospheric rise in CO₂ levels.  A DOE report on carbon sequestration science and technology (see reference 7) describes research needs and technology requirements for sequestering carbon by ocean and terrestrial systems, including a discussion of advanced biological processes and chemical approaches.  This topic focuses on biological mechanisms that offer the potential to slow the rate of atmospheric CO₂ increase, convert carbon into relatively stable organic or inorganic forms, and utilize biosystems to achieve the simultaneous production of fuel or chemicals while sequestering carbon.   Research is needed to identify and quantify mechanisms for CO₂ transformation at rates that will lead to the long term fixation or sequestration of large quantities of carbon (i.e., where10,000 to 100,000 tonnes or more of carbon per year transformed or fixed is considered significant) when applied to either natural (e.g., unmanaged terrestrial ecosystems) or managed biosystems.

Plants are known to fix CO₂ into biomass, and various terrestrial and aquatic microbial populations also fix greenhouse gases (CO_2, CH₄ and CO), either incorporating them into biomass or transforming them to potentially useful organic compounds.  Biochemical pathways have been identified in unicellular microorganisms that carry out the following transformations:  (1) CO₂ to CH₄ (methanogens); (2) CO₂ to organic material, i.e., biomass and/or other potentially useful byproducts (nonmethanogenic autotrophs); (3) CO to organic material (various, including carboxydotrophs, and methylotrophs); and (4) CH₄ to organic material (methanotrophs).  These desired activities are characteristic of bacteria, archaeae, unicellular algae, and yeasts.  The useful microorganisms may be either photosynthetic (as are algae and blue-green bacteria) or nonphotosynthetic (most microorganisms). 

In some cases, microbial carbon fixation activity leads to the direct production of long-chain hydrocarbons (up to C₃₆).  Both CH₄ and hydrocarbons are useful fuels, as is H₂, which is also produced by various microorganisms such as autotrophs.  This H₂-producing activity may occur directly via carbon fixation, or indirectly by the reductive biotransformation of organic carbon-sequestration products by other microbes.  Alternatively, some micro-organisms that are capable of fixing CO₂, CH₄, or CO, may instead, when coupled to other fermentative microbial cultures (e.g., bacteria or yeast) in a two-stage process, transform the gaseous substrates to useful alcohols (e.g., ethanol or 2,3-butanediol).  Other two-stage processes can produce oxychemicals that are themselves valuable commodity chemicals (acetate, lactate, acetaldehyde, acetoin, etc.).

Grant applications must provide for a systematic evaluation of proposed biological mechanisms and carbon sequestration systems.  Estimates of the amount of CO₂ transformed also must be provided, and any assumptions concerning quantities and conditions for carbon fixation and sequestration must be clearly defined.  Feasibility tests (analytical, bench, or field) performed in Phase I must demonstrate that the proposed approach, when scaled up, could theoretically result in a significant rate reduction in atmospheric CO₂ concentration, significant sequestered amounts of carbon, or the production of significant amounts of value-added food, fiber, chemicals, construction materials, or fuel products.  Phase I should provide preliminary data on prospective rates and quantities of enhanced carbon transformation and sequestration with more comprehensive and peer-reviewed data sets developed in Phase II.  Grant applications proposing only computer modeling without improvements in physical mechanisms or field approaches will not be considered. 

The facilities and expertise of the DOE Consortium for Research on Carbon Sequestration in Terrestrial Ecosystems (CSITE) can be made available to potential SBIR applicants to this topic.  The CSITE is a consortium based at Oak Ridge National Laboratory (ORNL), Pacific Northwest National Laboratory (PNNL), and Argonne National Laboratory (ANL).  The co-directors are Gary Jacobs (ORNL/e-mail: jacobsgk@ornl.gov) and Blaine Metting (PNNL/e-mail: fb_metting@pnl.gov).  Scientists at Texas A&M University, Colorado State University, the University of Washington, North Carolina State University, and the Joanneum Research Institute in Austria can also provide support to potential applicants.  The DOE also supports carbon sequestration research at the National Energy Technology Laboratory (NETL).  Grant applications are sought only in the following subtopics:

a.       Plant and Soil Sequestration of Carbon—Terrestrial vascular plants effectively capture CO₂ from the atmosphere and produce organic compounds, which sustain productivity of the Earth’s ecosystems.  Some of the fixed carbon is sequestered in soils or sediments and in wood products of terrestrial ecosystems.   Woody species, for example, sequester carbon as lignocellulose, which is a stored product for the lifetime of the tree.  Also, above- and below-ground biomass carbon contributes to soil organic matter, which may store carbon for long periods of time.  Grant applications are sought to identify and quantify the biological pathways and mechanisms leading to increased quantities of carbon sequestration by biotic and soil components of terrestrial ecosystems.  Areas of particular interest include:  (1) research on plant metabolic pathways or mechanisms that allow increased CO₂ fixation rates, achieved through conventional molecular or traditional genetic means, and leading to overall productivity increases; (2) novel technologies for managing vegetation (such as cost-effective nutrient management, forest regeneration, and ecosystem modification) to enhance carbon uptake and retention, thereby significantly increasing CO₂ fixation and C storage; (3) techniques for increasing the fraction of recalcitrant organic compounds produced during natural microbial conversion of plant biomass in soils, resulting in increased long-term C-storage; and (4) measurement techniques that would allow for the validation of technologies developed to enhance net long-term C sequestration in man-made and natural environments.

Proposed approaches should exhibit a capability to increase, or to measure increases of, carbon fixation or sequestration by at least 1 tonne per hectare per year.  Grant applications should provide information about rates and quantities of carbon fixation or sequestration enhancement by the proposed technologies.  Phase I must demonstrate basic feasibility and efficacy of proposed sequestration mechanisms, with the larger field-scale applications designed and tested in Phase II.

b.      Development of Enhanced Carbon-Sequestering Biosystems—Previously-identified, naturally-occurring cultures have been shown to fix carbon along with the production of fuels or commodity chemicals.  Grant applications are sought to further optimize these processes via one or more biotechnological techniques (strain improvement including the use of genetic engineering, culture medium optimization, novel reactor design, or improved reactor operation).   Desired improvements should increase carbon sequestration rates by at least 50%.  Grant applications should focus on:  (1) the development of microbial cultures with improved carbon-sequestering abilities, (2) the development of improved reactors or their operating protocols configurations that support improved growth, or (3) a combination of (1) and (2).  Phase I must demonstrate the improved carbon sequestration biosystem(s) on a bench scale.  Larger, pilot-scale demonstrations would be tested in Phase II.

c.   Production of Commodity Chemicals—Grant applications are sought to identify and characterize new one- or two-stage biosystems capable of fixing carbon along with the production of nonfuel commodity chemicals – acids, alcohols, and/or aldehydes.  (“Stage” refers to a discrete microbial culture containing either a single organism or a consortium – two-stage cultures are operated sequentially.  “Biosystem” refers to a culture grown in a bioreactor.)  Although a single biosystem would not be expected to perform all of these tasks, a single stage biosystem that produced large amounts of biosolids would still be of interest – provided that the biosolids could be used as petrochemical-sparing feedstocks for chemical production (either via traditional methods or as agricultural soil amendments via composting).  For biosolids produced as chemical feedstocks, no special attributes are required.  However, biosolids produced for agricultural purposes must be more resistant to subsequent biodegradation than typical cellulosic materials.  Areas of interest include (1) the identification of new, naturally-occurring microorganisms with acceptable carbon-sequestering abilities; (2) the identification of novel configurations for growth of useful microorganisms at the expense of greenhouse gases, or (3) a combination of (1) and (2). 

Proposed approaches based on these new biosystems must show significant potential for rapidly fixing large quantities of carbon.  An acceptable carbon sequestration rate would be the consumption of at least 5 grams of carbon (expressed on an atom basis) per gram cell dry weight per hour, at an ambient temperature of at least 15 degrees C.  This rate corresponds to a generation time of no less than approximately 24 hours.  In the case of chemical production, the overall process must demonstrate a net CO₂ consumption through the formation of biomass as a by-product.  (It is understood that CO₂ production, through normal cell metabolism, is unavoidable, but significant net yield of fixed carbon should be the design objective and performance measure.)  Phase I must demonstrate basic feasibility and efficacy of the proposed carbon sequestration mechanisms on a bench scale.  Larger, pilot-scale demonstrations with emphasis on yield performance would be tested in Phase II.

d.   Production of Fuel Chemicals—Grant applications are sought to identify and characterize new one- or two-culture biosystems capable of fixing carbon along with production of fuel chemicals – H₂, CH₄, fuel hydrocarbons including oils, or fuel alcohols such as ethanol.  Areas of interest include:  (1) the identification of new, naturally-occurring microorganisms with acceptable carbon-sequestering abilities, (2) the identification of novel configurations for growth of useful microorganisms at the expense of greenhouse gases, or (3) a combination of (1) and (2).  It is understood that no single biosystem would be capable of performing all of these tasks.

Proposed approaches based on these new biosystems must show significant potential for rapidly fixing large quantities of carbon.  An acceptable carbon sequestration rate would be the consumption of at least 5 grams of carbon (expressed on an atom basis) per gram cell dry weight per hour, at an ambient temperature of at least 15 degrees C.  This rate corresponds to a generation time of no less than approximately 24 hours.  In the case of chemical production, the overall process must demonstrate a net CO₂ consumption through the formation of biomass as a by-product.  (It is understood that CO₂ production, through normal cell metabolism, is unavoidable, but significant net yield of fixed carbon should be the design objective and performance measure.)  Phase I must demonstrate basic feasibility and efficacy of the proposed carbon sequestration mechanisms on a bench scale.  Larger, pilot-scale demonstrations with emphasis on yield performance would be tested in Phase II.

References:

1.       Belaich, J. P., ed., Microbiology and Biochemistry of Strict Anaerobes Involved in Interspecies Hydrogen Transfer, New York: Plenum Press, 1990.  (ISBN: 0-306-43517-9) (FEMS Symposium)

2.       Greenhouse Gases, Global Climate Change and Energ, U.S. DOE National Energy Information Center, 2002. http://www.eia.doe.gov/oiaf/1605/ggccebro/chapter1.html

3.        Jefferson, J., Looking to the Light, 2000.  (Available on the Web at: http://www.ornl.gov/ornl94/looking.html)

4.       Lal, R., ed., Soil Processes and the Carbon Cycle, Boca Raton: CRC Press, 1998.  (ISBN: 0-8493-7441-3)

5.       Ratledge, C., ed., Biochemistry of Microbial Degradation, Netherlands:  Kluwer Academic Publishers, 1994.  (ISBN: 0-7923-2273-8)

6.       References from Technical Sessions 3C, 4C, 5C, First National Conference on Carbon Sequestration, Washington, DC, May 14-17, 2001.  (Available on the Web at: http://www.netl.doe.gov) (Select “Publications” from menu on left.  Scroll down and select “Conference Proceedings.” A list of conferences in chronological order will appear, with the most recent loaded first.  Scroll down and select conference title.)

7.       Reichle, D., et al., Carbon Sequestration Research and Development, Washington, DC: U.S. Department of Energy Offices of Science and Fossil Energy, 1999.  (Full text available at http://www.ornl.gov/carbon_sequestration/)

8.       Rosenberg, N. J., et al., eds., “Carbon Sequestration in Soils: Science, Monitoring and Beyond,” Proceedings of the St. Michaels Workshop, St. Michaels, MD, December 1998, Columbus, OH:  Battelle Press, 1999.  (ISBN: 1-57477-084-5) (Available from Battelle Press.  Telephone: 800-451-3543.  Web site: http://www.battelle.org/bookstore.  Search by author.) (Summary and conclusions available on the Web at: http://www.cast-science.org/9812carb.htm) 

9.       Rozema, J., et al., eds., CO₂ and the Biosphere, Boston, MA:  Kluwer Academic Publishers, 1993.  (ISBN: 0792320441) (Also in Advances in Vegetation Science, Vol. 14. ISSN: 0168-8022) 

10.   Various articles from Natural Sinks of CO₂:  Proceedings of the Palmas Del Mar Workshop, Palmas Del Mar, Puerto Rico, February 24-27, 1992, Water, Air and Soil Pollution, 64(1-2), 1992.  (ISSN: 0049-6979)