Carbon Capture and Storage (Sequestration)
Carbon capture and storage (sequestration) or CCS will probably be a necessary component of mitigation of climate change. Learn about CCS here.
According to scientists, atmospheric build-up of carbon dioxide (CO2) and other greenhouse gases as a result of human activities is changing the composition of the Earth's atmosphere and tending to warm the planet. Scientific studies link these changes to shrinking glaciers, sea level rise, changes in plant and animal habitats, and other global impacts. One possible way to avoid the negative impacts of higher atmospheric concentrations of CO2 is to avoid emitting the CO2 into the air in the first place.
Carbon dioxide can be captured at stationary sources and injected underground for long-term storage in a process called geologic sequestration (GS) (Video – WMV, 8 min.). In its Special Report on Carbon Dioxide Capture and Storage, the Intergovernmental Panel on Climate Change (IPCC) identified CO2 capture and geologic sequestration as one of several options (including energy efficiency and renewable energy) that have the potential to reduce climate change mitigation costs and increase flexibility in achieving greenhouse gas emission reductions. The IPCC estimates that there is enough capacity worldwide to permanently store as much as 1,100 gigatons of CO2 underground (for reference, worldwide emissions of CO2 from large stationary sources is approximately 13 gigatons per year) (IPCC, 2005).
Confidence in this technology is supported by the knowledge that CO2 produced through natural processes has been retained in geologic formations for hundreds of millions of years (IPCC, 2005). The presence of multiple trapping mechanisms will reduce the mobility of CO2 underground over time, decreasing the risk of CO2 leaking to the surface (IPCC, 2005). It is likely that well-selected, well-designed, and well-managed GS sites can sequester CO2 for long periods of time.
Approximately 95% of the largest stationary sources of CO2 emissions (e.g., coal-fired power plants) in the United States are within 50 miles of a candidate GS site (GTSP, 2006). Considering the large storage capacity in the United States, GS has the potential to contribute significantly toward meeting the goals of the nation's climate policy. To help realize these goals, the federal government is conducting a wide range of GS-related activities.
The atmosphere today contains almost 400 ppm of CO2 (equivalent), which is not only increasing rapidly but is already near or maybe even above the concentration where unacceptably large negative impacts of the global warming trend of climate change will occur. Because neither the transition to renewable energies nor reduction in demand can happen overnight, fossil fuels (notably coal) will continue to play an important, even if diminishing, role in the energy portfolio for some time. We cannot allow coal consumption to increase atmospheric CO2 without unacceptable risk. Hence we have to get rid of this CO2 to stop it going into the atmosphere, i.e. store it underground and/or in plants and trees. We can also remove existing CO2 from the atmosphere and store it underground. Such removal of CO2 is what sequestration means.
There are some sequestration facilities that exist today, though none of them at the required large scale with demonstrated acceptable risk. There will clearly be a tradeoff between the risks of carbon sequestration and the risks of global warming impacts.
In July 2011 American Electric Power canceled its large carbon capture and sequestration project. This was considered one of the best test pilots of installing equipment on a large, existing coal-fired power plant that captures carbon dioxide and stores the gas permanently underground in deep rock formations, or saline aquifers... Mining workers in coal-rich states such as West Virginia expressed concerns that their jobs could be at risk eventually. Utilities will be under increasing pressure to switch from coal to natural gas because of new federal regulations on coal, and the industry had been counting on carbon capture as a savior for old coal plants, said Phil Smith of the United Mine Workers.
Sequestration, should it eventually prove technologically feasible at a large scale, should NOT be used as a convenient excuse to continue "Business as Usual BAU" and avoid mitigation, as detailed in the 2007 IPCC Mitigation Report - notably avoiding a wholesale transfer from fossil fuels to better energy sources (solar, wind, geothermal, fusion), reducing energy demand etc.
As with any geoengineering concept (which sequestration is), there is a dangerous risk that BAU will remain. In that case, a good analogy would be a "Global Drug". The cessation of taking the drug of sequestration in a BAU state, or the appearance of large unexpected failures and leaks, could result in a disastrous "Drug Withdrawal Pain", which would be quick reversal to disastrous global warming. Even at a low probability level, the resulting huge impacts would make BAU unacceptable from a risk management standpoint.
Thus, mitigation must remain the major focus. Nonetheless, sequestration can be a valuable tool in the portfolio of actions against global warming.
HERE is a letter from James Hansen; see also HERE and HERE. Hansen is the outspoken NASA scientist whose research led to "350". This refers to the "safe" level of CO2 of 350ppm, below today's level. Notably, Hansen says:
Coal caused fully half of the fossil fuel increase of carbon dioxide (CO2) in the air today, and on the long run coal has the potential to be an even greater source of CO2. Due to the dominant role of coal, solution to global warming must include phase-out of coal except for uses where the CO2 is captured and sequestered.
A practical global strategy almost surely requires a rising global price on CO2 emissions and phase-out of coal use except for cases where the CO2 is captured and sequestered.
More information for point carbon capture and storage
HERE are excerpts from "Coal and Global Warming FAQ" from the Union of Concerned Scientists: ...CCS technology faces many barriers, including its currently very high cost and unanswered questions about the feasibility and safety of long-term, large-scale geologic storage...Despite these challenges, CCS has the potential to play a useful role in the fight against global warming, warranting further investment of commercial-scale demonstration projects. In the meantime, new coal plants that do not capture carbon emissions should not be built...The United States has 500 or so large, operating coal plants, and more than 100 plants are currently proposed to be built. None of the existing plants capture their carbon emissions...While the risks posed by the potential expansion of the U.S. coal plant fleet are high, so too are those posed by the widespread expansion of coal-fired power plants in the emerging economies, especially in China and India. China is reportedly building the equivalent of two new 500 MW conventional coal plants per week, and the country already consumes far more coal than the United States...
HERE is the Carbon Sequestration Leadership Forum CSLF that has resources, including the CSLF inFocus Papers on Carbon Capture and Storage Technology. The CSLF has developed a series of short educational papers (1-6 pages in length) answering some of the most common questions surrounding carbon capture and storage technology.
Why Carbon Capture and Storage? (795kb pdf)
Is Geologic CO2 Storage Safe? (756kb pdf)
Underground CO2 Storage: A Reality? (877kb pdf)
CO2 Capture: Does it Work? (616kb pdf)
CO2 Transportation: Is it Safe and Reliable? (1.2mb pdf)
10 Facts About CCS (3.4mb pdf)
HERE is a real-life example of CCS in North Dakota, "Basin Electric aims to capture carbon emissions from coal-fired power plant". This is notable because it discusses retrofitting an existing plant: "At Basin Electric’s Antelope Valley coal-based power plant, a facility with twin towers capable of producing 450 megawatts each of electricity, researchers hope to retrofit carbon capture technology to existing infrastructure".
HERE is an article in Nature Geoscience by Gary Shaffer on "Long-term effectiveness and consequences of carbon dioxide sequestration" warning about leakage of CO2 and ocean acidification.
HERE is an article on basalt storage.
HERE is an article on a new CO2 scrubbing technique pioneered by Siemens. In August, the Siemens process will be put to the test at a pilot facility built by Siemens and the energy company E.ON: the Staudinger coal-fired plant, near Frankfurt. The plant will be adapted so that part of its exhaust gases are fed into a chimney containing a 25-meter-high column that gives off a solvent mist that reacts with CO2 under pressure. As the flue gases pass through the mist, the CO2 is chemically absorbed, leaving residual gases to pass out of the chimney. The CO2 can then be separated from the solvent, which can be reused. The goal is 90% removal of CO2. The design is in this diagram:
Besides point-source removal discussed so far, CO2 can be removed from the atmosphere in a variety of other ways. Here is the EPA discussion of Carbon Sequestration in Agriculture and Forestry. For the US, the EPA says:
U.S. forests and croplands currently sequester over 600 teragrams (Tg) of CO2 equivalent (about 170 Tg or million metric tons of carbon equivalent), after accounting for both gains and losses in carbon. This current amount of sequestration in forests and croplands offsets approximately 12% of total U.S. CO2 emissions from the energy, transportation and industrial sectors.
Additional land-use and management changes can maintain and enhance these carbon sequestration levels in the U.S., reduce emissions of other greenhouse gases, and thus help address the climate change problem.
HERE is a recent interesting paper:
Genetically altered trees, plants could help counter global warming
Study evaluates prospects for boosting carbon sequestration from the atmosphere by modifying natural biological processes and deploying novel food and fuel crops
What about Biochar?
Making biochar is essentially an inverse coal process - humans make a coal-like material and store it in the ground, thus sequestering CO2.
Biochar is charcoal created by pyrolysis of biomass, and differs from charcoal only in the sense that its primary use is not for fuel, but for biosequestration or atmospheric carbon capture and storage. Charcoal is a stable solid rich in carbon content, and thus, can be used to lock carbon in the soil. Biochar is of increasing interest because of concerns about climate change caused by emissions of carbon dioxide (CO2) and other greenhouse gases (GHG). See Wikipedia and Biochar.org for more information.
Another general method of carbon sequestration is carbon dioxide capture from the air, with subsequent storage. The novel part is the capture, with storage issues as above. HERE is the Wikipedia article on carbon dioxide air capture, which reads in part:
Carbon dioxide removal (CDR) or Carbon dioxide air capture... removes carbon dioxide from ambient air by carbon dioxide scrubbing. It is a different approach to removing CO2 from the stack emissions of large point sources, such as fossil fuel fired power stations... CDR methods are notably supported by IPCC chief Rajendra Pachauri, see HERE...
HERE is an exciting new report showing that bacteria can help the CCS process. Bacteria can be genetically modified to trap CO2 faster, keeping it underground for millions of years.
Even if the US and other developed countries completely capture and sequester CO2 from all coal-fired plants, the enormous current and increasing use of coal in China and other countries without sequestration will overwhelm the earth's CO2 budget. HERE is a Bloomberg article on the current and projected coal use in China.
Many countries are making plans to limit or phase out coal over time. See HERE.
LINKS to sequestration sites from BNA
GTSP 2006. Carbon Dioxide Capture and Geologic Storage: A Core Element of A Global Energy Technology Strategy to Address Climate Change. Global Energy Technology Strategy Program.
IPCC 2005. Special Report on Carbon Dioxide Capture and Storage. Prepared by working group III of the Intergovernmental Panel on Climate Change. Metz, B., O.Davidson, H. C. de Coninck, M. Loos, and L.A. Meyer (eds.). Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 442 pp. Available in full at www.ipcc.ch (PDF - 22.8MB)
HERE is a general information video on coal, including carbon capture and storage, by Climate Central, called Georgia: Coal and Carbon.
HERE is a video against carbon capture and storage, notably for a proposed plant in Linden NJ called PurGen: