Introduction CO2 capture and geological storage in energy and climate policy
M. Gerbis, W.D. Gunter and J. Harwood, APEC Capacity Building in the APEC Region, Phase II Revised and updated byand ICF International
CO2 capture and storage (CCS) involves the injection and containment of CO2 in geological structures such as depleted oil and gas reservoirs, onshore and offshorelocated deep in the earth's crust, salt caverns or unmineable coalbeds. It is both an approach to enhance production from existing oil and gas operations as well as a means for reducing emissions. This introduction is designed to provide answers to key questions important for policy makers and those interested in investigating the potential of CCS to enhance energy production and reduce greenhouse gases.
This introduction answers the following questions:
- What is CO2 capture and storage?
- How can CO2 capture and storage fit into an economy's climate change strategy?
- How does CO2 capture and storage form part of an economy's overall energy supply and production?
- What are the benefits of CO2 capture and storage?
- Where can we capture CO2?
- How do we transport CO2?
- How safely can CO2 be stored?
- What is the potential of CO2 capture and storage?
- How can the potential of CO2 capture and storage be tapped?
- What is the future outlook for CO2 capture and storage technology?
- How can I learn more about CO2 capture and storage?
What is CO2 capture and storage?
CO2 capture and storage (CCS) involves the capture, transport, injection and containment of CO2 in geological structures such as depleted oil and gas reservoirs, onshore and offshore saline 1and unmineable coalbeds located deep in the earth's crust. CCS is currently technically feasible, although large scale commercial CCS projects are yet to be developed. Many economies have pilot and demonstration projects to further the development of CCS technologies. Details of these projects can be found in the "Global Status of CCS" reports from the Global CCS Institute.
Figure 1: Overview of the components of carbon dioxide capture and storage (courtesy of CO2CRC).
How can CO2 capture and storage fit into an economy's climate change strategy?
Carbon dioxide (CO2) is produced from a number of sources, including the burning of fossil fuels (oil, coal and natural gas) and land-use/land-use changes. CO2 is a "greenhouse gas" (GHG), which when released into the atmosphere, trap heat much like the glass in a greenhouse. Excessive trapped heat can trigger changes in the Earth's climate over time, including a rise in the global average surface temperatures. Of all of greenhouse gases, CO2 is the single largest contributor to the problem, accounting for about 60% of the direct radiative forcing of all greenhouse gases. At a global level, such changes results in warmer air and ocean temperatures, changes in rainfall patterns, an increased number and intensity of floods, droughts, hurricanes and other storms, widespread melting of ice and snow, and rise of average sea level—all of which directly or indirectly affect human and ecological systems.
Economies from around the world developed an international agreement and strategy for dealing with the global climate change called the United Nations Framework Convention on Climate Change (UNFCCC). The UNFCCC outlines the need for better scientific understanding of global climate systems public education to improve understanding of climate change, and evaluation of what how economies and regions can adapt to any climate changes that might occur. An international effort to reduce greenhouse gas emissions (through an agreement called the Kyoto Protocol) has been in force since 2005. Negotiations are currently underway on a replacement to the Kyoto Protocol, which is due to expire in 2012.
CO2 emissions are a function of several factors. Population and the standard of living are two key factors that will not be discussed further in this document. Therefore, greenhouse gases can be reduced through several means:
- Lowering the energy intensity of the economy – by increasing the energy efficiency of energy production, conversion and end use;
- Lowering the carbon intensity of the energy system - by substituting lower-carbon or carbon-free energy sources, such as renewable energy, for the current fossil-fuel based sources; or
- Increasing the capacity and capture rate of carbon sinks to store CO2
Short of sustained investment in large-scale new technological advances and major expenditures, greenhouse gas emissions are likely to continue to rise as the GDP rises and economies expand. Energy from fossil fuels currently accounts for about 65% of greenhouse gas emissions, with 28.8Gt of energy-related CO2 emitted in 2007 (IEA, 2009). Fossil fuels are likely to remain a major component of world's energy supply for at least the next several decades because of their inherent advantages, such as availability, competitive cost, ease of transport and storage, and large resources. Therefore, the option of increasing carbon sinks has become one of the major means of reducing net carbon emissions into the atmosphere in the short to medium term.
The International Energy Agency (IEA) has prepared a scenario of policy objectives aimed at stabilizing the long-term level of CO2 concentration in the atmosphere at 450 parts per million which is expected limit the increase in global temperature to 2°C. To achieve this, an estimated 1.4 GtCO2 from energy-related sources would need to be captured and stored away from the atmosphere annually by 2030 (IEA, 2009).
In the longer term, as the use of carbon-based fossil fuels decreases due to diminishing reserves and replacement by other renewable or carbon-free energy forms, storage of CO2 may no longer be as integral a part of the strategy.
Figure 2: Representation of the carbon cycle (courtesy of CO2CRC).
Carbon dioxide sinks can be grouped into three broad classes based on the nature, location and ultimate fate of CO2:
- Biosphere sinks – These sinks are active, environmentally sensitive, natural for CO2. The oceans, forests, and soils (agricultural) ecosystems are members of this class. These sinks (excluding oceans) are probably most suitable for offsetting the emissions from diffuse sources of CO2 that could not otherwise be captured, but could also be applied as offset mechanisms for industrial CO2 sources. However, using these sinks as emission reduction mechanisms can result in considerable risk as these sinks are subject to natural CO2 releasing processes and it can be difficult to validate the amount of CO2 actually stored.
- Material sinks – Carbon that has been absorbed into various living systems such as trees can be stored as a material sink when the living system is created into a material product. Material sinks include durable wood-based products (furniture, paper, etc.), chemicals and plastics. These store carbon for different lengths of times depending on the life of the product. However, outside of extensive research, it is unlikely that carbon storage in material sinks will anything but a very minor role in greenhouse gas mitigation strategies.
- Geosphere sinks - are natural reservoirs for CO2 found in deep geological sedimentary basins. Human activity is required to store carbon in this type of sink. These sinks include depleted oil and gas reservoirs, deep aquifers, oil reservoirs suitable for (EOR), and coal beds. Currently, cost is one of the most significant issues that limits the use of geologic sinks. The cost of disposing of CO2 is made up of three factors: separation costs (i.e., capture/separation of CO2 from other combustion gases), transportation costs (i.e., compression, pipelines), and injection and storage costs (compression, injection wells). Efficient, cost-effective transportation and capture/separation technologies will need to be developed to allow large-scale use of geologic sinks. The financial drivers for CCS are currently not widely in place and immature regulatory frameworks for large scale storage makes investment difficult. Other issues such as community understanding and acceptance of the technology also need to be addressed.
A number of factors will need to be considered when evaluating the use of a given sink in an integrated portfolio of emissions reduction mechanisms. These factors include: environmental impact of the proposed sink mechanism; sink CO2 capacity; retention/residence time of CO2 in the sink; potential for accelerated leakage of CO2; rate of CO2 uptake by the sink; validation of storage in the sink; suitability of the sink/match to the emission source and type; and cost of implementation/utilization of the sink mechanism.
Of the types of carbon management activities, oceans are unlikely to be approved for large scale CO2 storage because of environmental concerns, and the biosphere, which depends on land-use, is difficult to control for long periods of time. If stored in appropriate locations, geological media can offer environmental benign repository of CO2 over long periods of time. In the sedimentary basins during fossil fuel production from geological media, pore space that was occupied by oil and gas for geological time can be refilled with anthropogenic CO2, thereby reducing atmospheric GHG emissions.
How does CO2 capture and storage form part of an economy's overall energy supply and production?
Fossil fuels – coal, gas and oil, currently dominate as the world's primary energy sources to meet the current energy demands. Based on current use and estimates of future demand, energy use is expected grow in the future, especially in non-OECD countries. This will place extra burden on economies to maximize opportunities for energy production.
Typically, oil and gas reservoirs cannot be economically mined to all of their capacity and some coalbed mines are at depths which prevent them from being mined economically. As a result, significant amounts of energy resources can remain in these reservoirs. The work involved in surveying, purchasing and constructing sites for future oil, gas and coalbed energy production operations is costly and time consuming. A solution which permits these resources to be further mined economically is beneficial for a variety of reasons.
CO2 can be used successfully to increase resource extraction potential and revenues from existing or known reservoirs and mines.
- Enhanced Oil Recovery (EOR) – CO2 is injected in miscible floods into depleted oil reservoirs. CO2 dissolves in the oil, reducing its viscosity, and the oil moves the oil towards the producing well. An additional 10-12% of oil reserves can be tapped through this process. This use of CO2 is a proven technology. A portion of the CO2 will remain in the reservoir, effectively "stored" from being released into the atmosphere. Use of this sink is restricted to economies that have oil reservoirs suitable for EOR-CO2 recovery techniques and its economic potential must be weighed against the cost of oil, the cost of CO2 to inject into the reservoir and reservoir characteristics. EOR is being conducted in more than 70 locations around the world.
- Enhanced Gas Recovery (EGR) – CO2 can be injected into the base of a depleted homogenous natural gas reservoir to push natural gas to the top of the reservoir for production. Computer simulation has confirmed that this could be an attractive technology for suitable gas reservoirs, however, EGR is unproven in practice as gas reservoirs can traditionally be tapped up to 90% of their total potential production through primary production methods.
- Enhanced Coalbed Methane Recovery (ECBM) – Coal beds have significant amounts of methane gas adsorbed in the coal which is called coalbed methane (CBM). By injecting CO2 into coal beds, the CO2 is adsorbed in the coal pore matrix, releasing the methane for energy production which could not otherwise have been mined economically. This method is still in a piloting stage, with several research projects completed or underway in USA, Canada, and China. The bulk of the world's coalbed methane resource occurs in People's Republic of China, the Asian portion of Russia, Kazahkstan, and India. Australia, portions of Africa, and Central Europe, as well as the and also contain varying amounts of this resource.
What are the benefits of CO2 capture and storage?
CCS provides an additional alternative in the utilization of fossil-fuel based energy, while providing additional transition time for energy systems to move towards carbon-reduced or zero carbon fuels, such as renewables. There are a number of economic and social benefits of CCS such as:
- Reduction of CO2 emissions into the atmosphere, thereby potentially mitigating dangerous climate change
- Innovation, access to state-of-the-art technologies, job creation and continued and more sustainable economic development;
- Secondary revenue stream as emissions of GHGs that are captured and stored can be converted into a tradeable commodity that could be sold on the international market;
- Reduction in air pollution as potentially harmful pollutants have to be removed to accommodate CO2 capture;
- Opportunity for enhanced oil and gas recovery.
Where can we capture CO2?
CO2 can be captured from large stationary sources, such as natural gas production facilities (where CO2 is already separated from other gases, as part of the process) fossil fuel fired power stations, iron and steel plants, cement plants and some chemical plants. The technology to capture CO2 from these sources is being adapted from the CO2 separation technology currently used in industries such as the natural gas industry and ammonia production and also from the technology used in theindustry. New technologies are being developed. While there are other major sources of CO2 (for example. emissions from mobile sources, such as cars and planes), current technology is not practical for capture from those sources.
Challenges that currently exist for capturing CO2 are reducing the cost of capture (including the amount of energy used by the capture equipment) and deploying the technology at scale.
How do we transport CO2?
CO2 has been transported by pipeline on a large scale in the US for over 30 years for use in EOR operations, with the longest pipeline being the Cortez pipeline which is over 800 km long. CO2 for small-scale commercial use is transported by truck and there has been some ship transport of CO2.
Major pipeline infrastructure will need to be built to implement CCS on a large scale, and this presents challenges particularly in the area of public acceptance if pipelines are to traverse densely populated areas.
How safely can CO2 be stored?
The safety of CO2 storage is of prime importance. Local risks of CO2 storage include CO2 leakage from the storage location; alteration of ground and drinking water chemistry and displacement of potentially hazardous fluids that could be in the reservoir where CO2 is stored. The appropriate selection of a site for CO2 storage is the single biggest factor determining the likelihood and magnitude of the storage risks. Rough quantitative estimates of storage effectiveness and risk potential must be undertaken on a site-by-site basis.
Specific methodologies have been developed for the identification, screening and prioritization of geological basins suited to CO2 storage which also present very low possibilities for leakage. Many of these geological basins have contained oil and gas for geological timeframes and thus have proven that they are low risk options, as long there are not many wells drilled into the reservoir. Each storage site is unique and requires a specific technical and operational approach. These approaches are being catalogued through experience to standardise practice in the field and ensure safety. Leakage that does occur tends to be from isolated spots such as faults, fractures and wells which can be directly monitored.
Natural analogues and current industrial experience in natural gas storage indicate that it is possible to achieve very low risks of leakage from well designed storage facilities. It is reasonable to expect that more than 99% of CO2 would be retained for over 1,000 years. Furthermore, experience suggests that it is improbable that large scale, sudden releases of CO2 from storage facilities will pose a threat to humans or ecosystems. Industrial experience with the injection of other fluids suggests that hazards associated with groundwater contamination would be rare. Cumulative past injection of over 30 million tons of CO2 for enhanced oil recovery has not triggered any significant seismic activity. Therefore, overall storage risk is considered very low for sites that are well characterised.
What is the potential of CO2 capture and storage?
Several studies have been conducted over the past decade to estimate the amount of CO2 that can be stored in sedimentary basins. Theoretical global storage capacity is estimated to be in the range of 8,000 to 15,000 GtCO2 (IEA, 2009). This suggests that we have the capacity to store most, if not all, of the CO2 needed to prevent the build-up of harmful levels of CO2 in the atmosphere.
The potential for CO2 capture and storage of any region and at any scale is based on the following two broad criteria:
- Availability of CO2 sources - the current and forecasted existence of large, stationary CO2 sources, such as thermal power generation, refineries, cement plants, petrochemical plants and large industrial complexes, that will allow CO2 capture on a large scale is needed to supply CO2 to storage sites.
- Availability of economically suitable storage reservoirs - The existence of geological media (sedimentary basins) suitable for CO2 storage within economically viable distance that meet the criteria of capacity and safety is also required.
Circum-Pacific sedimentary basins are less favourable for CO2 storage because they are located in tectonically unstable areas with faults and have generally smaller capacity for storage. The highest potential for CO2 storage in the APEC region is in large, continental-sized economies. The most promising sites would be in areas away from the Pacific Rim. This would include: Australia, Canada, Mexico, the People's Republic of China,and the United States.
Figure 3: Sedimentary basins in East and Southeast Asian APEC economies that would potentially be primary targets for CO2 geological storage based on their proximity to major CO2 sources (modified from Bradshaw et. al., October 2004, see Table 3 for basin names).
Table 1: Sedimentary basins in Asian APEC economies that would potentially be primary targets for CO2 geological storage based on their proximity to major CO2 sources (modified from Bradshaw et.al., August 2004 (for location see Figure 3).
How can the potential of CO2 capture and storage be tapped?
In order to tap into this opportunity and increase the likelihood of public acceptance of CO2 capture and storage, a number of activities must be conducted:
- Education and outreach - The notion of capturing and storing CO2 is relatively new, and many people are unaware of its role as a GHG reduction strategy. Increased education and awareness are needed to achieve acceptance of carbon storage by the general public, regulatory agencies, policy makers, and industry and thus enable future commercial deployment of this advanced technology.
- Risk/Performance Assessment - Risk models need to be established for the leakage of CO2 (slowly and rapidly) from the storage reservoir through breaks in the seals and along well bores, both in the short (during the injection period) and in the long (over the storage period) term. Safety issues and verification strategies are key components of risk/performance assessment.
- Life Cycle Analysis - The life cycle must be identified in the context of geological storage in the evaluation of GHG emissions throughout the full product or service system life cycle.
- Assessment of Storage Sites – Detailed geological analysis needs to be conducted to ensure that appropriate sites are selected for storage.
- Economics of CO2 Storage - Avoided CO2 as well as changing regulations must be accounted for.
- Regulatory/Legal Framework - This may have to be modified in order to address the long-term issues inherent in geological storage.
What is the future outlook for CO2 capture and storage technology?
The global energy mix is becoming increasingly constrained by environmental issues. It is anticipated future energy sources will be required to evolve to minimize the release of pollutants. End-of-pipe solutions for fossil fuel conversion will gradually be replaced by cleaner conversion technologies. These, in turn, will be replaced by renewable forms of energy. CO2 capture and storage is likely to play an important role in this transition.
Reducing GHG emissions to the atmosphere by storage of carbon dioxide in geological formations is a potential bridging technology to allow the continued use of fossil fuels while minimizing their effect on the environment. The world is moving from the current GHG emission-intensive fossil energy-based economy toward a GHG emission-free renewable-based energy economy. Given that energy use will increase in the future, and that the current percentage of clean renewable energy in the energy mix is small, a significant amount of time will be needed to make the transition from a predominantly fossil-fuel energy-based world to a renewable energy-based one. However, given the changing climate and the serious implications it could have to global environmental and human health, we cannot continue to use fossil fuels, particularly coal, using the same kind of technologies as in the past.
The concept of storing CO2 (capturing it and storing it in geological formations) permits a transition to be realized between current energy use patterns and those that must dominate in the future. Thus zero emission fossil fuels (ZEFF) can be generated with lower GHG emissions.
Some experts believe that the following transitions are likely to occur in three sequential steps as illustrated in Figure 4.
- The first transition is from business-as-usual to CO2 storage Business as usual depicts what we are doing today: conventional burning of fossil fuels to produce heat and electricity with emissions released to the atmosphere. During the first transition, business as usual is modified by the addition of downstream technologies for the diffuse storage of the CO2 into biomass; or by CO2 capture through upstream (oxyfuel combustion) or downstream (post-combustion) separation techniques and injected into deep geological formations for long-term storage. Both options will be utilized. In the former case, the additional cost is low; land-use constraints are the determining factor. In the latter case, the additional cost is much higher, driven by the expense of capturing a pure CO2 stream from the emission stream or due to the expense of oxygen production from air.
- In the second transition, the fossil fuel is gasified rather than burned, eliminating upstream or downstream separation techniques, before CO2 storage occurs This process energy for heat, electricity and hydrogen, and a pure CO2 waste stream which can be stored in or geological reservoirs. of fossil fuels also produces additional environmental benefits. The is used to power fuel cells, to make electricity in stationary plants or to power vehicles.
- In the third transition, the energy mix is dominated by the renewable energy sources: solar, hydro and wind. will still dominate the transportation market, requiring a hydrogen source but generated from renewables instead of fossil fuels.
Figure 4: CCS provides an opportunity for low emission fossil fuel combustion in the transition to renewable energy.
The whole process can be driven financially byin the storage transition stages where CO2 emission permits are sold by the government and traded on the open market. A portion of the profits from the sale of these permits could be used to fund renewable energy research, development, demonstration and deployment. This would allow orderly capacity-building of renewable energy sources without severely affecting our economy and standard of living. If this scenario is correct, geological storage in sedimentary basins of emissions from power plants and other industries will have an important role to play in the future as one of several bridging technologies.
How can I learn more about CO2 capture and storage?
CCS is an emerging technology. To assist APEC member economies to understand the potential of CCS, as well as the science and process involved in identifying and implementing a CCS project, the APEC Energy Working Group commissioned the development of a training package and series of workshops on CCS.
These training materials have been designed to:
- Increase the capacity of APEC economies to undertake their own detailed technical and site analysis of CO2 capture and geological storage potential;
- Provide the tools, procedures and understanding to undertake technical and site analysis in their respective economies;
- Assist project developer to understand the importance of effective communication with communities affected by the CCS project and provide them with an outreach strategy and sample outreach materials;
- Build upon existing technical knowledge in participating economies, with a special emphasis on the needs and requirements of developing economies.
The training modules provide a more in-depth, technical discussion on the following topics:
- Module 1 – CO2 capture and geological storage: Overview
- Module 2 – CO2 capture: Post-combustion flue gas separation
- Module 3 – CO2 capture: Pre-combustion (decarbonisation) and oxyfuel technologies
- Module 4 – CO2 compression and transportation to storage site
- Module 5 –CO2 storage options and trapping mechanisms
- Module 6 – Identification and selection of CO2 storage sites
- Module 7 – Key steps involved in developing and implementing a CO2 capture and storage project
- Module 8 – Health, safety and environmental risks of CO2 storage
- Module 9 – Risk assessment, measuring, monitoring and verification in CO2 storage projects
- Module 10 – Regulatory and legal aspects of CO2 storage
- Module 11 – The
- Module 12 – Economics of CO2 capture and storage
- Module 13 – Public awareness and community consultation
- Module 14 – Potential for CO2 capture and storage in the APEC region.
- Case Study #1 - The Saline Aquifer CO2 Storage Project: Case study of CO2 storage in an underground salt aquifer
- Case Study #2 - The Weyburn CO2 Monitoring and Storage Project: Case Study of a CO2 -EOR Storage Project
Community outreach documents:
- Community Outreach Strategy for CO2 Capture and Storage Projects: A strategy for successfully working with local communities to enhance your CO2 capture and storage project.
- Frequently Asked Questions about CO2 capture and storage
- Issue Briefing: What is CO2 capture and storage?
- Issue Briefing: Climate change and CO2 capture and storage
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