In This Issue
Spring Issue of The Bridge on Emerging Issues in Earth Resources Engineering
April 14, 2014 Volume 44 Issue 1

Carbon Capture, Utilization, and Storage

Monday, April 14, 2014

Author: Sally M. Benson and S. Julio Friedmann

An Important Part of a Response to Climate Change

Atmospheric concentrations of carbon dioxide (CO2) have risen to 400 ppm from a preindustrial baseline of about 280 ppm. With the relentless increase in atmospheric greenhouse gases (GHG) over the past 150 years and their impacts on climate, hydrology, ocean chemistry, and landscapes, the case for urgent and profound action grows stronger (IPCC 2007, 2012, 2013; Keeling et al. 2001). Action on all fronts is needed: energy conservation and improved efficiency, a switch from coal to natural gas to reduce emissions from power generation, development and adoption of no- and low-carbon power sources such as renewables and nuclear power, land-use changes, and application of direct emission control technologies for CO2.

To avoid increasing global average temperature by more than 2°C, within the next 40 years global GHG emissions must be reduced by 50 to 80 percent (IPCC 2007). At the same time, energy supplies must grow to meet growing energy needs of emerging economies, where access to modern forms of energy is crucial for economic development and improving people’s lives (Karekezi et al. 2012). Notwithstanding remarkable improvements in energy efficiency, energy demand is expected to grow nearly 50 percent by 2050, and even greater increases are expected if efficiency improvements are not realized (GEA 2012).


Global CO2 emissions today are 35 billion tonnes (Gt) each year. Government-mandated control technologies have proven successful in reducing emissions of atmospheric pollutants other than CO2 (e.g., SOx, NOx, and particulates), but the mass of CO2 emitted from a typical power plant is more than 100 times greater than those pollutants, driving higher costs and begging the question of what to do with all that CO2. Options for converting it to useful products such as cement or industrial chemicals have been considered but, though possible, are not economical today (Mazzotti et al. 2005). Furthermore, even if such conversions could be done efficiently and economically, the sheer mass of CO2 emitted to the atmosphere by industrial activity dwarfs demand for these products, relegating most CO2 utilization efforts to niche applications (Wilcox 2013).

Figure 1

A recent Global Energy Assessment (GEA 2012) examined 41 pathways for meeting worldwide needs for energy access, energy security, pollution abatement, and climate change mitigation, and concluded that 100–300 Gt of cumulative CO2 storage will be required by 2050 and 300–2,000 Gt by the end of the century (Figure 1). Carbon capture, utilization, and storage (CCUS) in underground geological formations has emerged over the past decade as the most feasible emission control option (Benson et al. 2012; IPCC 2005; MIT 2007). However, its widespread implementation over the next several decades is likely to be focused primarily on pumping CO2 into depleted oil reservoirs to increase recovery unless emission control performance standards are imposed on industrial and electricity generation emissions or the cost of CO2 emissions (e.g., in the European Emissions Trading System) exceeds the cost of capture.

Economic studies suggest that without CCUS the costs of GHG mitigation would rise significantly (Edmonds et al. 2004) and that 15 years’ delay in CCUS development would add 17 percent to the cost of mitigation (EBRD 2011). This is particularly true for overseas markets—such as China, India, Eastern Europe, and the Middle East—where fossil energy use is extensive, ubiquitous, and growing.

CCUS Implementation: Progress and Challenges

The primary purpose of CCUS is to reduce and ultimately eliminate GHG emissions. It works in two stages. First, CO2 is captured from large stationary sources and concentrated to a purity of 95 percent or more. Capture and purification can be done in a variety of ways; the most familiar is use of an amine-based solvent, others are combustion in pure oxygen (oxycombustion) and precombustion capture (gasification to produce H2 followed by the use of physical solvents such as Selexol) (Rochelle 2009; Thambimuthu et al. 2005; Wilcox 2013). The CO2 is then compressed, transported by pipeline, and pumped deep underground for indefinite isolation from the atmosphere. Options for this underground storage include depleted oil and gas reservoirs, saline formations, coal beds, and, perhaps in the future, basalt formations (Figure 2; Benson et al. 2005).

Figure 2

The prospect of indefinitely storing CO2 underground is known to engineers and earth scientists but may at first sound far-fetched to many people. The notion that the ground under their feet is filled with rocks with microscopic pores (typically 1–100 mm) that can store fluids under sealing rocks (pore spaces ~ 1–10 nm) for geological time scales of millions of years is difficult to grasp. Yet the oil and gas trapped in these small pores under seals are the source of today’s fossil fuel–based energy, which has evolved from a century of advances in the ability to characterize underground formations, drill, extract oil and gas, inject fluids to enhance oil recovery, and monitor fluids underground. So the idea that CO2 could be safely stored underground is based on long experience and sustained technological innovation.

Table 1

Ten CCUS projects are in operation (Table 1) and individual components of CCUS are available and used in many other applications, notably CO2-enhanced oil recovery (CO2-EOR1), hydrogen production, natural gas storage, and natural gas processing. CO2-EOR is the largest industrial use of CO2, injecting over 50 Mt/yr of it underground—the equivalent of emissions from twelve 500 MW coal-fired power plants. In the long run, other options may emerge, such as production of synthetic fuels through biotic or abiotic pathways (Mikkelsen et al. 2010).

Looking to the future, higher energetic efficiencies can be realized with tight integration of CCUS with power generation, but large-scale integration remains to be achieved because of challenges related to reliability (particularly as the technology is maturing), ability to provide load-following power generation, and maintenance of a high capacity factor.

A further significant consideration is cost. In part because first-of-a-kind plants are likely to cost significantly more (Al-Juaied and Whitmore 2009), the cost of CCUS for electricity generation remains higher than most markets will accept without a regulatory mandate. It can raise the levelized cost of electricity generation by 3–6 cents per kWeh—a 50–100 percent increase compared to the baseline technology (NETL 2012). Advanced power generation and CCUS technologies are being developed that may reduce the incremental cost by 20–40 percent (NETL 2012), and revenue from the sale of CO2 for enhanced oil recovery can help offset these costs, but only partly. Substantial technology development and demonstration are needed to bolster confidence and reduce costs.

Large-scale CCUS also raises important questions about possible environmental impacts of CO2 storage. In addition to effectively retaining CO2, storage must not cause harmful groundwater and ecosystem impacts (Cihan et al. 2013; Zhou et al. 2010); ensure that leakage, if any, does not create unsafe conditions for workers or the public (Jordan and Benson 2013); and avoid pressurization-induced seismic activity that causes property damage or compromises the seal of the storage reservoir (Zoback and Gorelick 2012). More will be said about these issues below.

CCUS is often thought of as a coal technology, but it can also reduce emissions from many stationary CO2 sources, such as natural gas–fired power plants, refineries, cement and steel plants, and industrial sites. For example, the abundance and low cost of natural gas in the United States are increasing the use of gas-fired power plants, which will eventually require CCUS to achieve needed reductions in CO2 emissions. In addition, as indicated in Table 1, other large sources (e.g., hydrogen plants, gas-processing stations, ethanol plants, fertilizer and coal-to-chemical plants) produce byproduct streams of CO2 with high purity, and as such provide potential CO2 sources for early, low-cost demonstration. Two industrial-scale facilities, the Great Plains Synfuels Plant and the Weyburn-Midale Oilfield have operated this way since 2001.

International Investment in CCUS

The oil and gas industry has led the way to commercial-scale CCUS projects, motivated in part by a tax for offshore CO2 emissions of about $50/t CO2 in Norway. Beginning in 1996, Statoil, ExxonMobil, BP, PanCanadian (now Cenovus), Shell, and Sonatrach (Algeria) initiated CCUS projects associated with natural gas cleanup facilities, synfuels, or hydrogen production units (Table 1). These projects have been monitored by research teams from academia, government, and industry to ensure that CO2 stays underground and to evaluate how closely the migration of CO2 conforms to model predictions. Overall, the projects have been successful, with only one documented instance of leakage to the atmosphere (at the In Salah project, which occurred in an old exploration well that was successfully sealed after the leak was detected2; Iding and Ringrose 2010). By about 2015, seven new projects are expected to increase the total CCUS capacity to about 30 Mt/year (GCCSI 2011).

Over the past decade there has been a remarkable international upsurge in both interest and investment—government and industry commitments total more than $26 billion (GCCSI 2011), with an investment rate of $2.8 billion in 2012 (Hallerman 2013). The United States is investing nearly $6 billion in ongoing large demonstration projects and fundamental and applied R&D. Led by the Department of Energy (DOE) Office of Fossil Energy, this funding supports advanced power projects (e.g., FutureGen 2.0), polygeneration projects (e.g., Texas Clean Energy Project), chemical plants (e.g., the Archer Daniel Midlands Ethanol Plant and the Port Arthur Steam-Methane Reforming Project), and seven Regional Carbon Sequestration Partnerships.3

The Chinese government has made similar substantial investments in demonstration projects and research, such as the GreenGen project, the Shidongkou postcombustion demonstration, several oxygen-fired plants, and new R&D centers. In 2013 China’s National Development and Reform Commission announced that CCUS is “an important task in the 12th 5-year plan,” with recommendations and roadmaps for pilot demonstration and scale-up (GCCSI 2013b).

Other countries, in particular those with carbon-intensive economies, are also making substantial investments. Australia has created the Global CCS Institute and invested over $300 million to date in policy and project support; and the country’s Gorgon Project will be the world’s largest storage project (6 Mt/year) in a saline formation. The Canadian government has funded monitoring and research at the Weyburn-Midale Project and invested in large projects (e.g., SaskPower’s Boundary Dam Power Station project and Shell’s Quest Project) as well as pipeline infrastructure. Norway’s Statoil initiated one of the first and largest CCUS projects (Sleipner), injecting over 16 Mt of CO2 into a saline aquifer beneath the North Sea. The government has also supported industrial scale-up and testing (Mongstad), other large projects (Snøhvit, In Salah), a new project in Svalbard, a public-private partnership to invest in low-cost capture technology (Gassnova), and many R&D centers.

Lessons Learned

There are a number of major findings from all this investment by government and industry. CO2 has been safely injected and stored underground in CCUS as well as CO2-EOR projects. There is no evidence of groundwater contamination or habitat degradation. Numerous CO2 storage pilots have shown that many options are available for monitoring CO2 movement in the subsurface; seismic imaging and pressure monitoring are among the most useful for tracking the location of stored CO2 and detecting potential leakage. Theoretical and laboratory studies continue to strengthen the scientific foundations assessing the integrity of long-term storage (Benson et al. 2012). Demonstration of CO2 capture from power generation has been done at a scale of 100,000 tonnes/year,4 and construction of larger projects is now under way.

National and regional assessments indicate that storage capacity is large but unevenly distributed. For example, a recent study by the US Geological Survey concluded that there is about 3,000 Gt of storage capacity in the United States, more than half of it in the Gulf Coastal Plains (USGS 2013). This independent assessment aligns well with the low end of the range of a DOE (2012) report that found storage capacity is sufficient to meet anticipated national needs. Limited storage options in some regions, such as the Northeast, will necessitate long-distance pipeline transport and the attendant challenges of building large pipelines. That said, more than 5,000 km of CO2 pipelines are in use in the United States and have operated safely for over 30 years.

However, not everything has proceeded as anticipated. On the economic front, costs for first-of-a-kind plants have often exceeded initial estimates, leading to cancelled projects and concern about maintaining momentum in CCUS (GCCSI 2013a). On the technical front, a few large projects encountered unexpected complications that have led to redesigns. In Europe, local public opposition has led to the cancellation of projects and in some places prohibition of onshore storage. On the regulatory front, the EPA’s new class VI well designation for underground injection continues to evolve as implementation issues arise. In some cases, it has been difficult to find a storage formation with high enough permeability.

Learning by doing is to be expected in an undertaking of such global size and scale, and policymakers and industrial developers are wrestling with how best to take advantage of what is now known. Furthermore, new issues arise as fundamental and applied research explores the implications of large-scale storage.

A fiftyfold scale-up of the current CCUS enterprise would be needed to reduce emissions by a billion tonnes per year. Careful and sophisticated earth resources engineering is required to ensure that CO2 storage is safe and effective. Among the technical concerns about CO2 storage at this large scale is the pressure buildup caused by CO2 injection. For low-permeability formations, small and closed storage reservoirs, or multiple storage projects that use the same reservoir, excessive pressure buildup could occur if not managed appropriately and could lead to induced seismicity or brine migration, with consequent risks to groundwater and/or the integrity of the seal. The degree to which this poses unacceptable risk is the subject of debate—although such problems are rare in CO2-EOR projects and in the limited experience with saline formation storage, experienced only at the In Salah Project where CO2 was stored in a formation with very low permeability (e.g., Cihan et al. 2013; Gan and Frolich 2013; Juanes et al. 2012; Verdon et al. 2013; Zhou et al. 2010; Zoback and Gorelick 2012).

Regulations both prohibit fracturing the seal of a formation into which fluids are injected for either storage or enhanced oil recovery and limit the injection pressure. There are also methods to reduce and manage the extent of pressure buildup through careful well placement, injection rate limits, and brine extraction5 (Birkholzer et al. 2012; Buscheck et al. 2012; WRI 2008).

Leakage through abandoned wells has been cited as a significant issue in areas of hydrocarbon exploration and production (Benson et al. 2005; Celia and Nordbotten 2009; Gasda et al. 2004). In the United States more than 2.6 million oil and gas wells have been drilled since 19506; of these, about 1 million are producing oil (EIA 2011) and gas.7 For the inactive wells, unless they are located and properly sealed before CO2 injection begins, they can lead to leakage of brine, hydrocarbons, and CO2. Storage projects will have to demonstrate effective management of these risks to ensure protection of groundwater resources and the support of public stakeholders, regulators, and investors.

Finally, a collaborative and transparent approach is needed in the conduct of large-scale CO2 storage projects with appropriate monitoring, analysis, and reporting.

Getting Ready for Large-Scale Deployment of CCUS

A number of critical issues must be resolved before CCUS is likely to be widely deployed to reduce emissions from the power sector. Some are technical, such as reducing the costs for CO2 capture; others are social, economic, political, or regulatory. Critical nontechnical issues include the following: public confidence that CO2 storage is safe; development of cost-effective regulatory regimes; assurance of financial responsibility for future environmental damages if they occur; trustworthy GHG accounting and verification approaches; fair compensation of power generators for implementing CO2 emission controls; and private sector investment. Cooperation among industry, government, and academia will be needed to address these issues and lower barriers for early deployment, and will involve support for demonstration projects, fundamental and applied research, capacity building, regulatory innovation, approaches for financing early commercial projects, and international collaboration.

Access to capital for large-scale deployment could also be a major factor limiting the widespread use of CCUS. Individual large-scale CCUS projects require multibillion-dollar investments; for example, the Kemper County (Mississippi) 582 MW integrated gasification combined cycle power plant is expected to cost $4.5 billion or more.8 Project financing at this scale is difficult, and even more so when assurance of cost recovery is uncertain. Clear policy and regulatory regimes will be crucial for obtaining the capital to build these multibillion-dollar projects. A carbon tax, performance standards such as those recently proposed by the US Environmental Protection Agency,9 and cap and trade systems such as the European Union Emissions Trading System (ETS) can all provide such certainty. Further dialogue about the most effective and economically efficient means of stimulating investment in CCUS is needed.

Another way to both accelerate CCUS deployment and reduce total risk and cost is through international collaboration. Recently established programs—such as the IEA International Greenhouse Gas R&D Program, Carbon Sequestration Leadership Forum (CSLF), and Global CCS Institute (GCCSI)—are designed to help inform governments and decision makers, share information and results, and foster closer ties between governments and businesses. In addition, the US-China Clean Energy Research Center, a joint initiative of Presidents Hu and Obama, is intended to foster information sharing, business-to-business protections and support, and applied R&D for CCUS.

These international efforts will improve readiness, reduce costs, and increase the likelihood of implementation for key projects. Developing countries may also need financial and technical support for technology access, reductions in the cost of CCUS, development of workforce capacity, and training of regulators for permitting, monitoring, and oversight.

Summary and Conclusions

Control technologies for reducing CO2 emissions from industrial sources and fossil fuel–fired power plants are an important component of achieving sufficiently large and rapid emission reductions over the coming decades. Carbon capture with storage in deep geological formations is the only currently available control technology likely to be deployable at scale within this time frame, but it will require the work of engineers, scientists, and social scientists to resolve important challenges.

Today, over 20 Mt/yr of CO2 are captured from anthropogenic sources and injected underground, and there is a pipeline of projects that will raise this amount by 50 percent within the next few years. But this is still far short of the fiftyfold scale-up needed, and a variety of challenges must be addressed to achieve the necessary progress. Costs for capture are too high, particularly in the absence of regulatory drivers for CCUS.

Outstanding technical issues related to large-scale storage (e.g., pressure management, wellbore leakage, and storage capacity) will require a combination of R&D and commercial experience before they are fully resolved. Nontechnical aspects are perhaps even more important: access to capital for plant construction, regulatory issues, and public support for CCUS must also be a top priority for policymakers and industry leaders.

Above all, sustained support from governments, industry, and academia is critical for continuing progress in this important CO2 emission reduction technology.


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1 At high enough pressure and temperature (and for specific crude oil compositions), CO2 and oil become miscible and the oil that would otherwise be trapped by capillary forces can be recovered efficiently.

 2 In November 2012 BP announced that CO2 injection at In Salah had been suspended pending a business decision on whether to continue the commercial operation of the storage program at the site.

3 Information about these partnerships is available from the National Energy Technology Laboratory, at rcsp.html.

4 American Electric Power and Alstom conducted a demonstration test of capture and storage using chilled ammonia capture technology on a slipstream of 30 MW from the 1,300 MW Mountaineer Power Plant (West Virginia) in 2009–2010. The captured CO2 was stored in a nearby saline aquifer at a depth of 4.1 km.

5 Brine extraction with desalination may provide an economically attractive source of water in some regions (Bourcier et al. 2011; Breunig et al. 2012).

6 Data on crude oil and natural gas exploratory and development wells from the US Energy Information Administration; available at

7 Data on the number of producing gas wells from the US Energy Information Administration; available at

8 Reported by Reuters in July 2013, “Costs rise for Southern Co’s coal gasification plant”; available at kemper-idUSL2N0F723N20130701.

9 Available at pdf.


About the Author:Sally M. Benson is a professor in the Department of Energy Resources Engineering at Stanford University and director of the Global Climate and Energy Project. S. Julio Friedmann is deputy assistant secretary for coal at the US Department of Energy and former chief energy technologist at Lawrence Livermore National Laboratory.