Excerpts from:

Carbon Sequestration

State of the Science

A working paper for roadmapping future carbon sequestration R&D

February 1999

(The total report can be found at http://www.fetc.doe.gov/publications/press/1999/seqrpt.pdf.)

THE ROAD MAP VISION AND GOALS

The vision for the road map is to:

Possess the scientific understanding of carbon sequestration and develop to the point of deployment those options that ensure environmentally acceptable sequestration to reduce anthropogenic CO₂ emissions and/or atmospheric concentrations. The goal is to have the potential to sequester a significant fraction of 1 GtC/year in 2025 and 4 GtC/year in 2050.

STRATEGIC ISSUES

Following are the general recommendations of the report addressing strategic issues regarding a comprehensive carbon sequestration program.

• Sequestration R&D could expand the world’s future options for dealing with greenhouse gases.

• Many carbon sequestration options are particularly amenable to improving existing activities—such as CO₂ injection during secondary oil recovery—and often provide important secondary benefits, such as improving ecosystems during reforestation.

• Some carbon sequestration options, such as improved agricultural practices, are available practically immediately. Examining ongoing, field-scale sequestration investigations in terrestrial, geological, and ocean systems can provide critical experience for designing the necessary environmental research programs.

• Some carbon sequestration options that have limited capacity or relatively short carbon residence times could nonetheless make important near-term contributions during a transition to other longer-term carbon management options. Other carbon sequestration options can provide significant long-term contributions.

• For carbon sequestration to be a viable option, it needs to be safe, predictable, reliable, measurable, and verifiable; and it needs to be competitive with other carbon management options, such as energy-efficient systems and decarbonized energy technologies.

• Carbon sequestration is an immature field, so multiple fundamental R&D approaches are warranted and significant breakthroughs can be expected. The federal government is an appropriate sponsor of carbon sequestration R&D.

• Integrated analyses of the carbon sequestration system should be periodically updated to evaluate the potential contributions, costs, and benefits of various carbon sequestration options.

• The information from the R&D program should be provided to policy makers to aid them in developing policy and selecting the most efficient and effective solutions to the issues of climate change.

Separation and Capture of CO₂ from the Energy System

In our assessment of the scientific and technological gaps between the requirements for CO₂ separation and capture and the capabilities to meet these requirements, many explicit and specific R&D needs were identified.

• A science-based and applications-oriented R&D program is needed to establish the efficacy of current and novel CO₂ separation processes as important contributors to carbon emissions mitigation. Important elements of such a program include the evaluation, improvement, and development of chemical and physical absorption solvents, chemical and physical adsorbents, membrane separation devices with selectivity and specificity for CO₂ -containing streams, molecular and kinetic modeling of the materials and processes, and laboratory-scale testing of the selected processes.

• Field tests are needed of promising new CO₂ separation and capture options in small bypass streams at large point sources of CO₂ , such as natural gas wells and hydrogen production plants.

The most likely options currently identifiable for CO₂ separation and capture include

• chemical and physical absorption

• physical and chemical adsorption

• low-temperature distillation

• gas-separation membranes

• mineralization and biomineralization

• vegetation

Sequestration in the Oceans

These approaches will require better understanding of marine ecosystems to enhance the effectiveness of applications and avoid undesirable consequences.

• Field experiments of CO₂ injection into the ocean are needed to study the physical/chemical behavior of the released CO₂ and its potential for ecological impact.

• Ocean general circulation models need to be improved and used to determine the best locations and depths for CO₂ injection and to determine the long-term fate of CO₂ injected into the ocean.

• The effect of fertilization of surface waters on the increase of carbon sequestered in the deep ocean needs to be determined, and the potential ecological consequences on the structure and function of marine ecosystems and on natural biogeochemical cycling in the ocean need to be studied.

• New innovative concepts for sequestering CO₂ in the ocean need to be identified and developed.

Sequestration in Terrestrial Ecosystems

• The terrestrial ecosystem is a major biological scrubber for atmospheric CO₂ (present net carbon sequestration is ~2 GtC/year) that can be significantly increased by careful manipulation over the next 25 years to provide a critical "bridging technology" while other carbon management options are developed.

Carbon sequestration could conceivably be increased by several gigatonnes per year beyond the natural rate of 2 GtC per year, but that may imply intensive management and/or manipulation of a significant fraction of the globe’s biomass. However, those potentials do not yet include a total accounting of economic and energy costs to achieve these levels. Ecosystem protection is important and may reduce or prevent loss of carbon currently stored in the terrestrial biosphere. The focus for research, however, should be on increasing the rate of long-term storage in soils in managed systems.

• Research on three key interrelated R&D topics is needed to meet goals for carbon sequestration in terrestrial ecosystems:

• Field-scale experiments in large-scale ecosystems will be necessary to understanding both physiological and geochemical processes regulating carbon sequestration based upon integrative ecosystem models. Such carbon sequestration experiments are needed to provide proof-of-principle testing of new sequestration concepts and integration of sequestration science and engineering principles.

Sequestration in Geologic Formations

• Fundamental and applied research is needed to improve the ability to understand, predict, and monitor the performance of sequestration in oil, gas, aqueous, and coal formations. Elements of such a program include multiphase flow in heterogeneous and deformable media; phase behavior; CO₂ dissolution and reaction kinetics, micromechanics and deformation modeling; coupled hydrologic-chemical-mechanical-thermal modeling; and high-resolution geophysical imaging. Advanced concepts should be included, such as enhancement of mineral trapping with catalysts or other chemical additives, sequestration in composite geologic formations, microbial conversion of CO₂ to methane, rejuvenation of depleted oil reservoirs, and CO₂ -enhanced methane hydrate production.

• A nationwide assessment is needed to determine the location and capacity of the geologic formations available for sequestration of CO₂ from each of the major power-generating regions of the United States. Screening criteria for choosing suitable options and assessing capacity must be developed in partnership with industry, the scientific community, and public and regulatory oversight agencies.

• Pilot-scale field tests of CO₂ sequestration should be initiated to develop cost and performance data and to help prioritize future R&D needs. The tests must be designed and conducted with sufficient monitoring, modeling, and performance assessment to enable quantitative evaluation of the processes responsible for geologic sequestration. Pilot testing will lay the groundwork for collaboration with industrial partners on full-scale demonstration projects.

Advanced Biological Processes

• Research should be initiated on the genetic and protein engineering of plants, animals, and microorganisms to address improved metabolic functions that can enhance, improve, or optimize carbon management via carbon capture technology, sequestration in reduced carbon compounds, use in alternative durable materials, and improved productivity.

• The objectives and goals of the advanced biological research should be linked to those specific problems and issues outlined for carbon sequestration in geological formations, oceans, and soils and vegetation so that an integrated research approach can elucidate carbon sequestration at the molecular, organism, and ecosystem levels.

• Short-, mid-, and long-term goals in advanced biological research should be instituted so that scale-up issues, genetic stability in natural settings, and efficacy in the field can be assessed.

Advanced Chemical Approaches

• The proper focus of R&D into advanced chemical sciences and technologies is on transforming gaseous CO₂ or its constituent carbon into materials that either are benign, inert, long-lived and contained in the earth or water of our planet, or have commercial value.

• The chemical sciences can fill crucial gaps identified in the other focus areas. In particular, environmental chemistry is an essential link in determining the impact and consequences of these various approaches. Studies to address the specific gaps identified in Chap. 7 should be conducted to ensure that other focus areas meet their potential.

Why is Carbon Sequestration Important?

It is important to carry out research on carbon sequestration for several reasons:

• Carbon sequestration could be a major tool for reducing carbon emissions from fossil fuels. However, much work remains to be done to understand the science and engineering aspects and potential of carbon sequestration options.

• Given the magnitude of carbon emission reductions needed to stabilize the atmospheric CO₂ concentration, multiple approaches to carbon management will be needed. Carbon sequestration should be researched in parallel with increased energy efficiency and decarbonization of fuel. (These efforts should be closely coordinated to exploit potential synergies.)

• Carbon sequestration is compatible with the continued large-scale use of fossil fuels, as well as greatly reduced emissions of CO₂ to the atmosphere. Current estimates of fossil fuel resources—including conventional oil and gas, coal, and unconventional fossil fuels such as heavy oil and tar sands—imply sufficient resources to supply a very large fraction of the world’s energy sources through the next century.

• The natural carbon cycle is balanced over the long term but dynamic over the short term; historically, acceleration of natural processes that emit CO₂ is eventually balanced by an acceleration of processes that sequester carbon, and vice versa. The current increase in atmospheric carbon is the result of anthropogenic mining and burning of fossil carbon, resulting in carbon emissions into the atmosphere that are unopposed by anthropogenic sequestration. Developing new sequestration techniques and accelerating existing techniques would help diminish the net positive atmospheric carbon flux.

Although the current DOE carbon sequestration program is modest in scale, many of the foundations have already been built for significantly expanding this effort. The DOE Office of Science program on CO₂ sequestration includes both the Office of Basic Energy Sciences (BES) and the Office of Biological and Environmental Research (BER). The primary relevant goal for BES is to develop major new fundamental knowledge that crosscuts DOE’s applied programs related to carbon management, including such disciplines as materials sciences, chemical sciences, geosciences, plant and microbial biosciences, and engineering sciences. BES has long standing programs in fundamental research, such as improved materials synthesis and combustion engineering for more efficient energy technologies, improved catalysts for low-carbon industrial processes, improved understanding of biological mechanisms of carbon fixation, and improved understanding of fluid flow in the subsurface for geological sequestration (www.er.doe.gov/production/bes/bes.html). In 1999, a new program in BES and BER will be initiated to conduct research in carbon management, including carbon sequestration, as a result of the climate change technology initiative. The subjects will include sequencing genomes of methane- and hydrogen-producing microorganisms; enhancing the natural terrestrial and oceanic fluxes of CO₂; and improving the understanding of biological carbon fixation, materials, catalysts, combustion chemistry, and physics and chemistry of geological reservoirs. BER has a longstanding fundamental research program on the global carbon cycle. Current research focuses on atmospheric measurements of carbon fluxes and related processes, terrestrial carbon fluxes, and advanced biological investigations of carbon in terrestrial and ocean margin systems. A key element of terrestrial carbon research involves Ameriflux, which is a network of CO₂ flux measurements across North, Central, and South America to quantify net CO₂ exchange between the atmosphere and representative terrestrial ecosystems. Free Air CO₂ Enrichment (FACE) experiments provide information about changes in the carbon content of ecosystems under increased concentrations of atmospheric CO₂, altered temperatures, and altered precipitation regimes. Relevant information can be found at www.er.doe.gov/production/ober/gc/accc-fr.html and http://cdiac.esd.ornl.gov/programs/ameriflux. Ocean research focuses on molecular biological approaches to understanding the coupling between carbon and nitrogen cycles (www.er.doe.gov/production/ober/GC/accc-ft.html). BER also sponsors a program, Integrated Assessment of Global Climate Change that supports research in understanding carbon management frameworks for integrated assessment modeling activities. DOE’s Office of Fossil Energy has a program on CO₂ capture and sequestration to develop and demonstrate technically, economically, and ecologically sound methods to capture, reuse, and dispose of CO₂. In 1998, DOE made awards for 12 "cutting-edge" research projects, ranging from the use of CO₂ –absorbing algae growing on artificial reefs to deep-ocean or deep-saline-reservoir greenhouse gas disposal. Some of these projects may be selected for further development. (Details on this solicitation can be found at www.fe.doe.gov). The Office of Fossil Energy has recently undertaken an initiative to provide formal management direction to sequestration program activities and to establish program content and funding priorities. A team has been assembled to define a research strategy clearly and to ensure coordination with internal and external stakeholders. In making its recommendations, the team will draw heavily from this report. In FY 1999, the second phase of the Fossil Energy novel concept investigations will obtain the required engineering and economic data to proceed to proof-of-concept. In the areas of geological and ocean sequestration, international government/industry projects will continue. In 1991 the International Energy Agency (IEA) established a Greenhouse Gas R&D Programme focused on analyzing technologies for capturing, using, and storing CO₂. It has expanded to include methane, as well as forestation options. The program is currently in its third 3-year phase and has support from 16 countries (including the United States) and a growing number of industrial organizations. (Details on this program can be found at www.ieagreen.org.uk.) In addition to government studies, industry is moving ahead with development of CO₂ sequestration technologies: