Northsiders Luncheon

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By Ian Duncan, Associate Director for Environmental and Earth Systems, Bureau of Economic Geology, Jackson School Of Geosciences, University of Texas at Austin

Although the causes, effects, and remediation of global warming are still contested issues, there is a broadly held belief amongst climate scientists that carbon sequestration is the only viable solution to addressing what they see as the deleterious effects of CO2 buildup in the atmosphere. Carbon sequestration involves the capture CO₂ from combustion of fossil fuel sources, and to place the carbon into long term storage. Power plants emit more than one-third of the global emissions of CO2. One of approaches under consideration by the U.S. Department of Energy (DOE), that has the potential to reduce atmospheric carbon dioxide (CO2) concentrations, is injection of CO2 into the subsurface (geologic sequestration). The Gulf Coast Carbon Center envisions the Gulf Coast region becoming a major site, perhaps the nation’s predominant site, for a new carbon sequestration industry. The economic engine that will power the development of this industry will be CO2 based enhanced oil recovery. The Bureau of Economic Geology has made a conservative estimate that, excluding the Permian Basin, over 5.7 billion barrels of oil are recoverable from Texas. This activity can pay for the construction of CO2 capture plants, regional CO2 pipelines, and compression facilities that later can be used for putting CO2 into long term storage in deep brine aquifers in the Gulf Coast. Chemical plants and fossil fuel gasification units currently being planned for the Gulf coast area are potential souces of relatively cheap CO2.  Input from environmental and petroleum geoscientists are needed in order optimize the mechanics of CO2 sequestration and also to help society to clearly understand both the risks and benefits of geologic sequestration.

The increasing CO2 concentration in the atmo­sphere is of global concern. The United States produces one-quarter of the world’s CO2 emissions from combustion of fossil fuel; therefore, it can play a critical role in capturing CO2 and putting it into long term storage. Unfortunately the majority of these emissions are in the form of flue gas from coal fired power plants which contain low CO2 concentrations. These low concentrations result in high costs for the separation of CO2 to enable long term sequestration. Gulf Coast chemical plants (such as hydrogen plants) are potential sources for high CO2 emissions that may provide relatively cheap sources for CO2.  Gasification of coal offers another way to cost effectively decarbonize the energy from fossil fuels and to thus facilitate carbon sequestration.

Current global levels of anthropogenic, or human-produced, CO2 emissions are 25.6 Gigatons of CO2 per year. A significant portion of the global total, approximately 1 Gigatons of these emissions comes from the Gulf Coast region of Texas, Louisiana, and Mississippi, representing 16 percent of the U.S. annual CO2 emissions from fossil fuels. The Gulf Coast region also provides an opportunity for addressing the problem. Geologic sequestration enables fossil fuel to be decarbonized by capturing CO2 from the combustion products and injecting the gas compressed gas into a super-critical fluid, into the subsurface saline brine aquifer for long-term storage.

The Gulf Coast overlies an unusually thick clastic sequence comprised of highly porous and permeable sand aquifers, separated by thick shale aquitards. This sedimentary wedge provides an amount of potential storage that are best described as vast and realistically aggregate to hundreds of Gigatons of storage. The extensive blankets of low permeability shales that separate the sand aquifers should assure storage for thousands of years, well past the expected age of fossil fuel dominance.

The Bureau of Economic Geology (BEG) has formed the Gulf Coast Carbon Center (GCCC) to carry out applied research in developing strategies and protocols for long term geologic storage of carbon the in deep subsurface of the Gulf Coast. The GCCC is a partnership between the BEG and a number of corporations including BP, Chevron, Entergy, Kinder Morgan, Marathon, NRG, Praxair, and Schlumberger:

BP: generally recognized as a major oil company leader in green house gas and global warming issues.

Chevron: a leading innovator in “clean energy” including development of “syn-gas” technology.

Entergy: a major producer of coal fired electric power and a leader in the fight against greenhouse gases.

Kinder Morgan: the largest producer of oil from CO₂ injection based Enhanced Oil Recovery (EOR) in the US, the second largest producer of oil in Texas, and the largest operator of CO₂ pipelines in the country.

Marathon: a mid sized oil exploration, production and refining company.

NRG Development Company: a major northeast producer of coal fired power stations with world wide holding in electric power generation.

Praxair: the second largest seller of CO2 gas in the world and a key player in CO₂ separation and transport technology.

Schlumberger: an innovator in carbon management through geologic sequestration.

The vision of the GCCC is to seek “to impact global levels of GHG in the atmosphere by doing science and engineering studies that will support reduction of CO₂ and methane emissions and enable the development of an economically viable, multifaceted, CO₂ sequestration industry in the Gulf Coast”.

SCENARIOS FOR LARGE SCALE GEOLOGIC STORAGE OF CO2 IN THE GULF COAST

Geologic storage in Gulf Coast brine aquifers, if implemented on a massive scale, could help reduce the rate of increase of CO2 during a transition period of a few decades while society effects a change to a hydrogen-based or some other energy future. This would require decarbonizing fossil fuels by retrofitting current power plants and factories with CO2 scrubbers. This is capital intensive (except in the rare cases where a pure CO2 emission is produced) and is typically accompanied by a high energy penalty. For example carbon scrubbers installed in a pulverized coal power plant may use 20% or more of the plants power. The Department of Energy (DOE) is funding a range of research projects that seek to develop new carbon capture technologies that will capture CO2 at significantly lower costs and with much smaller energy penalties.

Power plants based on gasification of coal, called Integrated Gasification Combined Cycle (IGCCC) plants are evolving as “clean coal” technology that provides a potential bridge to a future hydrogen-based economy. The DOE’s proposed FutureGen plant is to be a state-of-the-art IGCC plant combined with CO2 sequestration. The BEG is currently leading the Texas response to the DOE’s competition to site the FutureGen plant.  

Gasification of coal, lignite, petcoke and/or biomass is a way of extracting energy from coal that has the advantage of producing CO2 in much higher concentrations than in pulverized coal power plants. Gasification plants use pure oxygen rather than air, to partially oxidize coal in the presence of water at high temperatures and elevated pressures. Gasification of coal produces syngas composed of hydrogen and CO2, with CO2 in sufficiently high concentrations that traditional separation technologies are cost effective. This gas mixture is also suitable for separation using membrane techniques (an active field of research).

In addition to CO2 capture, necessary components of a future sequestration industry in the Gulf Coast include: a regional system of a pipeline backbone and trunk lines; distributed compression plants; and development of a variety of CO2 sinks. Preliminary economic modeling supports the conclusion that such regional pipeline complexes linking many sources and sinks are both more efficient than single pipelines linking individual sources and sinks. Such regional pipelines also allow matching capture and injection rates across multiple sites. The capital costs for adding capture to existing plants, and building compressors and pipeline complexes

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    Ian J. Duncan is Associate Director for Environment and Earth Systems at the Bureau of Economic Geology, The University of Texas at Austin. Dr. Duncan received a B.A., Honors I, Earth Sciences, Macquarie University, Sydney, Australia, 1974 and a Ph.D. Geology, University of British Columbia, Vancouver, Canada, 1982. Dr. Duncan worked for 10 years as a Scientist Manager at the Virginia Department of Mines, Minerals and Energy Division of Mineral Resources. He also worked as a geology professor at SMU in Dallas and Washington University in St Louis. Dr. Duncan’s interests lie in managing integrated grant/contract-based multidisciplinary research projects in a nonprofit organization, carbon management based on geologic CO2 sequestration, development and management of large-scale pilot projects for carbon capture and long-term storage, and implementation of clean oil technologies, conceiving, designing, implementing, and managing multidisciplinary geologic information management projects and modern geologic mapping, remote sensing, structural geology, knowledge management in the earth sciences, digital mapping/ enterprise GIS, and geochronology.