Carbon Capture and Storage

Intergovernmental Panel on Climate Change has issued a draft summary for policy makers on one of the technologies expected to help us meet the need to reduce carbon emissions 70% worldwide, more than 90% per person in the US, even while population and per capita energy consumption increases. (This reduces carbon emissions to the amount the oceans can absorb; more reductions are needed to protect the oceans.) This reduction is needed no matter the final level of atmospheric carbon, 400 parts per million volume (ppmv), as International Climate Change Taskforce proposes for the initial limit, or double pre-industrial levels of 280 ppm.

One (metric) tonne is 1.1 American tons. Units can be tonne CO2 or tonne C. CO2 has 44/12 as much mass as the carbon alone.

From the report:

1. Carbon dioxide (CO2) capture and storage (CCS) is a process consisting of separation of CO2 from industrial and energy-related sources, transport to a storage location, and long-term isolation from the atmosphere. This report considers CCS as an option in the portfolio of mitigation actions for stabilization of atmospheric greenhouse gas concentrations.

2. The Third Assessment Report (TAR) indicates that no single technology option will provide all of the emission reductions needed to achieve stabilization, but a portfolio of mitigation measures will be needed.

3. Capture of CO2 can be applied to large point sources. The CO2 would then be compressed and transported for storage in geological formations, in the ocean, in mineral carbonates, or for use in industrial processes.

[Currently, large point sources account for 13,500 million tonnes (metric tons) of carbon dioxide/year, 3,700 million tonnes of carbon. Major industries are electric power, cement, oil and gas, iron and steel, petrochemical, and bioethanol and bioenergy – energy from plant matter.]

4. The net reduction of emissions to the atmosphere through CCS depends on the fraction of CO2 captured, the increased CO2 production resulting from loss in overall efficiency of power plants or industrial processes due to the additional energy required for capture, transport and storage, any leakage from transport, and the fraction of CO2 retained in storage over the long term.

A power plant equipped with a CCS system (with access to geological or ocean storage) would need roughly 10 – 40% more energy than a plant of equivalent output without CCS, most of it for capture and compression-CCS systems with storage as mineral carbonates, would need 60 – 180% more energy than a plant of equivalent output without CCS.

What is the current status of CCS technology?

5. There are different types of CO2 capture systems: post-combustion, pre-combustion and oxyfuel combustion. The concentration of CO2 in the gas stream, the pressure of the gas stream and the fuel type (solid or gas) are important factors in selecting the capture system.

6. Pipelines are preferred for transporting large amounts of CO2 for distances up to around 1,000 km. For amounts smaller than a few million tonnes of CO2 per year, or larger distances overseas, use of ships, where applicable, could be economically more attractive.

7. Storage of CO2 in deep, onshore or offshore, geological formations uses many of the same technologies that have been developed by the oil and gas industry and has been proven to be economically feasible under specific conditions for oil and gas fields and saline formations, but not yet for storage in unminable coal beds.

8. Ocean storage potentially could be done in two ways: by injecting and dissolving CO2 into the water column (typically below 1,000 meters) via a fixed pipeline or a moving ship, or by depositing it via a fixed pipeline or an offshore platform on the sea floor at depths below 3,000 m, where CO2 is denser than water and is expected to form a “lake” that would delay dissolution of CO2 into the surrounding environment. Ocean storage and its ecological impacts are still in the research phase.

10. Industrial uses of captured CO2 as gas or liquid, or as a feedstock in chemical processes that produce valuable carbon-containing products are possible, but are not expected to contribute to significant abatement of CO2 emissions.

What is the geographical relationship between the sources and storage opportunities for CO2?

12. Large point sources of CO2 are concentrated in proximity to major industrial and urban areas. Many such sources are within 300 km of areas that potentially hold formations suitable for geological storage. Preliminary research suggests that, globally, a small proportion of large point sources is close to potential ocean storage locations.

Scenario studies indicate that the number of large point sources is projected to increase in the future, and that, by 2050, given expected technical limitations, around 20 – 40% of global fossil fuel CO2 emissions could be technically suitable for capture, including 30 – 60% of electricity generation and 30 – 40% of industrial CO2 emissions.

13. CCS enables the control of the CO2 emissions from fossil fuel-based production of electricity or hydrogen, which in the longer term could reduce part of the dispersed CO2 emissions from transport and distributed energy supply systems.

Electricity could be used in vehicles, and hydrogen could be used in fuel cells, including in the transport sector. Gas and coal conversion with integrated CO2 separation (without storage) is currently the dominant option for production of hydrogen.

What are the costs for CCS and what is the technical and economic potential?

14. Application of CCS to electricity production, under 2002 conditions, is estimated to increase electricity generation costs by about 0.01 – 0.05 US dollars per kilowatt hour (US$/kWh), depending on the fuel, the specific technology, the location, and the national circumstances. Including the benefits of EOR [Enhanced Oil Recovery] would reduce additional electricity production costs due to CCS by around 0.01 to 0.02 US$/kWh (see (tables) for absolute electricity production costs and for costs in US$/tCO2 avoided). Increases in market prices of fuels used for power generation would generally tend to increase the cost of CCS. The quantitative impact of oil price on CCS is uncertain. However, revenue from EOR would generally be higher for higher oil prices. Whilst applying CCS to biomass-based power production at current small scale would add substantially to the electricity costs, co-firing of biomass in a larger coal-fired power plant with CCS would be more cost-effective.

Costs vary considerably in both absolute and relative terms from country to country. Since neither Natural Gas Combined Cycle, Pulverized Coal nor Integrated Gasification Combined Cycle systems have yet been built at a full scale with CCS, the costs of these systems cannot be stated with a high degree of confidence at this time. In the future, the costs of CCS could be reduced by research and technological development, and economies of scale.

15. Retrofitting existing plants with CO2 capture is expected to lead to higher costs and significantly reduced overall efficiencies than for newly built power plants with capture. The cost disadvantages of retrofitting may be reduced for some relatively new and highly efficient existing plants, or where a plant is substantially upgraded or rebuilt.

17. Energy and economic models indicate that the major CCS system’s contribution to climate change mitigation would come from deployment in the electricity sector. Most modelling as assessed in this report suggests that CCS systems begin to deploy at a significant level when CO2 prices begin to reach approximately 25 – 30 US$/tCO2. [$90 – 110 tonne C]

18. Available evidence suggests that worldwide, it is likely that there is a technical potential2 of at least about 2,000 GtCO2 (545 GtC) of storage capacity in geological formations.

There could be a much larger potential for geological storage in saline formations, but the upper limit estimates are uncertain due to lack of information and an agreed methodology. The capacity of oil and gas reservoirs is better known. Technical storage capacity in coal beds is much smaller and less well known

19. In most scenarios for stabilization of atmospheric greenhouse gas concentrations between 450 and 750 ppmv CO2 and in a least-cost portfolio of mitigation options, the economic potential of CCS would amount to 220 – 2,200 GtCO2 (60 – 600 GtC) cumulatively, which would mean that CCS contributes 15 to 55% to the cumulative mitigation effort worldwide until 2100, averaged over a range of baseline scenarios. It is likely that the technical potential for geological storage is sufficient to cover the high end of the economic potential range, but for specific regions, this may not be true.

20. In most scenario studies, the role of CCS in mitigation portfolios increases over the course of the century and including CCS in a mitigation portfolio is found to reduce the costs of stabilizing CO2 concentrations by 30% or more. [not compared to other alternatives, but compared to not using CCS and so needing to use other very costly technologies.]

23. Adding CO2 to the ocean or forming pools of liquid CO2 on the ocean floor at industrial scales will alter the local chemical environment. Experiments have shown that sustained high concentrations of CO2 would cause mortality of ocean organisms. CO2 effects on marine organisms will have ecosystem consequences.

The chronic effects of direct CO2 injection into the ocean on ecosystems over large ocean areas and long time scales have not yet been studied.

25. Observations from engineered and natural analogues as well as models suggest that the fraction retained in appropriately selected and managed geological reservoirs is very likely to exceed 99% over 100 years, and is likely to exceed 99% over 1,000 years.

26. Release of CO2 from ocean storage would be gradual over hundreds of years.

34. There are gaps in knowledge regarding some aspects of CCS. Increasing knowledge and experience would reduce uncertainties and thus facilitate decision-making regarding deployment of CCS for climate change mitigation.

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