Carbon Capture and Sequestration

A carbon capture and sequestration/storage (CCS) system is designed to remove CO₂ at the source of emission, such as a coal or natural gas plant, or from the environment. The CO₂ can be stored in a sealed underground chamber or used for another purpose. Currently about 40 million tons of CO₂ are captured each year, about 0.1% of total emissions ¹.

For industrial heat and process emissions from major commodities, CCS may be the only economically viable tool to reduce emissions by more than 30% ².

Cost

We estimate the following costs of carbon capture from various industrial sources.

Costs from industrial sources are given by Folger ³ and the IEA (⁴ and

⁵). Costs from coal power are estimated by Gillingham and Stock ⁶, Hardisty et al. ⁷, Hu and Zhai ⁸, and Rubin et al. ⁹. Costs from natural gas are estimated by Budinis et al. ¹⁰ and Rubin et al. ⁹. Fasihi et al. ¹¹ estimate the cost from direct air capture. The IPCC ¹² estimates the cost from bioenergy and carbon capture and sequestration (BECCS).

Seawater may also be a promising venue for extracting carbon dioxide ¹³, though reliable potential costs estimates are limited. Recent analysis suggests that the CO₂ abatement cost of synthetic diesel from seawater may range from $373 to $717 per ton ¹⁴.

A major determinant in the monetary and energy costs of CO₂ capture is concentration, with lower costs from higher concentrations. The following are estimates of primary energy requires to capture a ton of CO₂ from various sources.

Sources: Malins ¹⁵ and von der Assen et al. ¹⁶, with primary energy conversion

given by the Building Energy Codes Program ¹⁷.

Sources of Carbon

While industrial sources of carbon tend to be cheaper than diffuse sources such as direct air capture, only limited amounts of them are available, and fossil fuel-based sources in particular will hopefully be phased out eventually. Following are estimates of how much carbon will be available at midcentury from non-fossil sources.

Source: ¹⁸.

Usage

Most captured CO₂ today is used for enhanced oil recovery, with most of the remainder stored geologically.

Source: Global CCS Institute ¹.

A barrel of oil releases about 500 kg of CO₂, and if CO₂ enhanced oil recovery is used, about 300-600 kg CO₂ are injected into the well ¹⁹.

For the industrial CO₂ market more broadly, the dominant uses are urea for fertilizer and enhanced oil recovery. The world market of 230 million tons of industrial CO₂ is less than 1% of world emissions of about 40 billion tons annually as of 2022.

Source: IEA ²⁰.

Potential future uses of captured CO₂ include methanol, hydrocarbons, methane, mineralization into building materials, working fluids for coal and geothermal power plants, fertilizing plant growth in greenhouses ²¹, feedstock for the chemical industry, and several niche industrial uses ²², ²³.

If CO₂ is captured from fossil fuels or cement, and then used to produce synthetic fuels, the overall process may have lower emissions than the conventional alternative, but it is not a true low-carbon process. Rather, in this scenario, each molecule of CO₂ is emitted over two processes rather than one.

Enhanced Oil Recovery

Enhanced oil recovery, also known as enhanced oil extraction or tertiary recovery, is a means of injecting heat, chemicals, or a high pressure gas, often carbon dioxide, into an oil well to increase production. Applied after primary (without additional injection) and secondary (water flooding), EOR works by mixing the injected fluid with the oil, thereby increasing the ease of recovery ²⁴. The sources of injection for EOR are estimated as follows.

World EOR projects by type, as of 2017. Percentages do not add to 100% due to

rounding. Source: International Energy Agency ²⁵.

As of 2019, it was estimated that 70% of CO₂ for EOR was sourced from natural geologic deposits. Such EOR provides no carbon sequestration benefit ²⁶. When CO₂ is captured from an industrial source, it is important to credit the carbon savings to either the source of capture, or to the oil well, but not to both ²⁶.

As of 2018, about 2% of oil was produced via EOR, and lower prices and competition with other emerging production technologies had diminished interest in EOR ²⁷. The International Energy Agency has estimated that EOR has the potential to sequester 60-240 billion tons of CO₂ from 2015 to 2050, or 1.7 to 6.9 billion tons per year over that period ²⁸. If the source of CO₂ is from the atmosphere or from another industrial process, then each captured ton of CO₂ used for EOR will reduce emissions on net by 0.63 to 0.79 tons, taking into account leakage and the effect of increased oil consumption overall ²⁸.

The leakage rate of carbon dioxide injected into oil wells has been estimated at less than 1% over 1000 years ²⁴, but this requires that the well is properly sealed after production has ceased ²⁹. Induced seimicity has been observed as a result of EOR, though this can be managed by controlling the rate of injection ³⁰.

Direct Air Capture

Direct air capture (DAC) refers to a system that captures and removes carbon dioxide from the ambient atmosphere, rather than a concentrated industrial waste stream. The International Energy envisions that DAC will remove 980 million tons of CO2 per year by 2050, compared to just 0.01 million tons per year now ³¹. The two leading technologies are liquid solvent DAC (L-DAC) and solid sorbent DAC (S-DAC). Following are estimates of the resources required for 1 billion tons of DAC per year, about 2.5% of current emissions.

Cost estimates are based on current values and would almost certainly decrease with a large buildout. The IEA projects an eventual cost of less than $100/ton for CO2 removal by DAC. Land use estimates are for the DAC facilities only, and not the energy infrastructure required to fuel them. Source: IEA ³¹.

S-DAC can operate with lower temperature heat, enabling it to use geothermal or solar thermal energy. L-DAC requires high temperature heat.

If an L-DAC system had to desalinate its own water usage, it would add $3.50 - $9.50/ton CO₂ to the cost of carbon removal ³¹. It is possible to run a DAC device intermittently on renewable electricity as a load balancing strategy, but this would further raise the cost ³¹.

Geological Storage

It is estimated that the world could store 8,000 to 55,000 billion tons of CO2, the equivalent of 200-1275 years of emissions at current rates ³¹. In the United States, it is estimated that over half of onshore storage could be developed at less than $10/ton CO2, while more than half of offshore storage could be developed at less than $35/ton ³¹. Carbon leakage is estimated at less than 0.01%, slow enough for CCS to be secure as a mitigation solution ³².

References

1. Global CCS Institute. "The Global Status of CCS". 2018. ↩ ↩²

2. Organization for Economic Cooperation and Development, International Energy Agency. "CCS 2014: What lies in store for CCS?". 2014. ↩

3. Folger, P. "Carbon Capture: A Technology Assessment". Congressional Research Service. July 2010. ↩

4. International Energy Agency. "Technology Roadmap - Carbon Capture and Storage, 2013 Edition". ↩

5. International Energy Agency. "Transforming Industry through CCUS". May 2019. ↩

6. Gillingham, K., Stock, J. "The Cost of Reducing Greenhouse Gas Emissions". Journal of Economic Perspectives 32(4), pp. 53-72. November 2018. ↩

7. Hardisty, P., Sivapalan, M., Brooks, P. "The Environmental and Economic Sustainability of Carbon Capture and Storage". Int J Environ Res Public Health 8(5), pp. 1460-1477. May 2011. ↩

8. Hu. B,. Zhai, H. "The cost of carbon capture and storage for coal-fired power plants in China". International Journal of Greenhouse Gas Control 65, pp. 23-31. 2017. ↩

9. Rubin, E., Davison, J., Herzog, H. "The cost of CO₂ capture and storage". International Journal of Greenhouse Gas Control 40, pp. 378-400. September 2015. ↩ ↩²

10. Budinis, S., Krevor, S., Mac Dowell, M,. Brandon, N., Hawkes, A. "An assessment of CCS costs, barriers and potential". Energy Strategy Reviews 22, pp. 61-81. November 2018. ↩

11. Fasihi, M., Efimova, O., Breyer, C. "Techno-economic assessment of CO₂ direct air capture plants". Journal of Cleaner Production 224, pp. 957-980. July 2019. ↩

12. IPCC. "Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change". [Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum, S. Brunner, P. Eickemeier, B. Kriemann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel and J.C. Minx (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 2014. ↩

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25. International Energy Agency. "Number of EOR projects in operation globally, 1971-2017". November 2018. ↩

26. McGlade, C. "Can CO2-EOR really provide carbon-negative oil?". International Energy Agency. April 2019. ↩ ↩²

27. McGlade, C., Sondak, G., Han, M. "Whatever happened to enhanced oil recovery?". International Energy Agency. November 2018. ↩

28. International Energy Agency. "Storing CO2 through Enhanced Oil Recovery". November 2015. ↩ ↩²

29. Ide, S.T., Friedmann, S.J., Herzog, H.J. "CO₂ leakage through existing wells: current technology and regulations". In 8th International Conference on Greenhouse Gas Control Technologies (Vol. 1, pp. 19-33). June 2006. ↩

30. National Petroleum Council. Meeting the Dual Challenge: A Roadmap to At-Scale Deployment of Carbon Capture, Use, and Storage. Chapter 8: CO₂ Enhanced Oil Recovery. March 2021. ↩

31. International Energy Agency. "Direct Air Capture: A key technology for net zero". April 2022. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

32. Miocic, J. M., Gilfillan, S. M. V., Frank, N., Schroeder-Ritzrau, A., Burnside, N. M., Haszeldine, R. S. "420,000 year assessment of fault leakage rates shows geological carbon storage is secure". Scientific Reports 9: 769. January 2019. ↩