Carbon sequestration, also known as carbon capture and storage (CCS), is a technology that is being pursued which might allow the continued use of fossil fuels, especially coal. Unfortunately, CCS has developed more slowly than expected, and the technology is unlikely to make a major contribution to reducing carbon pollution until after the 2020s.
Burning fossil fuels releases carbon dioxide into the atmosphere, and that carbon dioxide is the primary cause of recent global warming. In general, the vast majority of strategies to reduce such carbon dioxide emissions involve reducing fossil fuel combustion, either by replacing fossil fuels with carbon-free sources (such as solar energy or nuclear power) or by using a technology that does the same job but simply uses less energy (such as an energy efficient light bulb or motor).
To ensure fossil fuel combustion does not release carbon pollution into the atmosphere, the carbon dioxide from a coal-fired power plant (or potentially a gas-fired one) must be captured and stored somewhere forever. That carbon dioxide could be removed before combustion or after combustion. Doing so before you burn the fossil fuel is much simpler and cheaper because after combustion, the carbon dioxide begins to diffuse in the exhaust (flue) gas and then the atmosphere. The more diffuse the carbon dioxide, the more difficult and costly it is to extract from the air.
On the other hand, coal can be gasified, and the resulting “synthesis gas” (syngas) can be chemically processed to produce a hydrogen-rich gas and a concentrated stream of carbon dioxide. The latter can be piped directly to a carbon storage site. The former can be burned in a highly efficient “combined cycle” power plant. The whole process—integrated gasification combined cycle (IGCC) plus permanent storage in underground sites—is considerably more expensive than conventional coal plants. In 2009, Harvard’s Belfer Center for Science and International Affairs published a major study, “Realistic Costs of Carbon Capture.” The Harvard analysis concluded that first-of-a-kind CCS plants will have a cost of carbon abatement of some $150 per ton of carbon dioxide avoided, not counting transport and storage costs. This yields a “cost of electricity on a 2008 basis [that] is approximately 10 cents/kWh higher with capture than for conventional plants.” That price would effectively double the cost of power from a new coal plant. In 2003, The National Coal Council explained a key problem that is slowing development of IGCC: “Vendors currently do not have adequate economic incentive” to pursue the technology because “IGCC may only become broadly competitive with” under a “CO2-restricted scenario.”
It would certainly be more useful to have a CCS technology that could capture and store the carbon dioxide from the exhaust or flue gas postcombustion produced by thousands of existing coal plants than to have CCS technology that works only on newly designed plants. However, that technology has historically been even further from commercialization at scale and necessarily involves capturing carbon dioxide that is far more dilute. As a 2008 U.S. DOE report had pointed out:
“Existing CO2 capture technologies are not cost-effective when considered in the context of large power plants. Economic studies indicate that carbon capture will add over 30% to the cost of electricity for new integrated gasification combined cycle (IGCC) units and over 80% to the cost of electricity if retrofitted to existing pulverised coal (PC) units. In addition, the net electricity produced from existing plants would be significantly reduced—often referred to as parasitic loss—since 20-30% of the power generated by the plant would have to be used to capture and compress the CO2.”
Given how very expensive early-stage carbon capture and storage is, jump-starting accelerated development and deployment of CCS requires:
- A rising price on carbon dioxide to make CCS profitable or
- Large subsidies by some government entity or
- Significant investment and financing by the private sector or
- Some combination of those three things
Perhaps the major reasons for the very slow development of CCS for both new and existing power plants have been (1) lack of a price on carbon dioxide or other government policy that could provide large ongoing subsidies coupled with (2) lackluster interest and investment by the private sector.
How slow has development been? In October 2013, the New York Times summarized the state of CCS with their headline, “Study Finds Setbacks in Carbon Capture Projects.” The story noted that, “the technology for capturing carbon has not been proved to work on a commercial scale, either in the United States or abroad.” One major CCS demonstration at a West Virginia coal plant was shut down in 2011 because “it could not sell the carbon dioxide or recover the extra cost from its electricity customers, and the equipment consumed so much energy that, at full scale, the project would have sharply cut electricity production.”
The 2013 survey on the “Global Status of CCS,” by the Global CCS Institute found that “while C.C.S. projects are progressing, the pace is well below the level required for C.C.S. to make a substantial contribution to climate change mitigation.”
The Norwegian oil and gas company Statoil is one of the few in the world that has actually captured carbon dioxide from natural gas processing facilities and stored it geologically (in former gas and oil fields). Statoil’s vice president for CCS said in late 2014, “Today the cost per ton is economically prohibitive,” and so “We need public-private partnerships where the government takes commercial exposure and some of the risks.”
A key issue for CCS is that although the development of large-scale commercial projects has been very slow, the requirements for CCS to make a major dent in the global warming problem are huge. Vaclav Smil, Distinguished Professor Emeritus of the Environment at the University of Manitoba in Canada, described “the daunting scale of the challenge,” in his analysis “Energy at the Crossroads”:
“Sequestering a mere 1/10 of today’s global CO2 emissions (less than 3 Gt CO2) would thus call for putting in place an industry that would have to force underground every year the volume of compressed gas larger than or (with higher compression) equal to the volume of crude oil extracted globally by [the] petroleum industry whose infrastructures and capacities have been put in place over a century of development. Needless to say, such a technical feat could not be accomplished within a single generation.”
There are many other issues with CCS. For instance, there is the leakage issue. Even a very small leakage rate from an underground carbon storage side (TK CHECK:site?) (less than 1% a year) would render it all but useless as a “permanent repository.” In addition, a Duke University study found the following: “Leaks from carbon dioxide injected deep underground to help fight climate change could bubble up into drinking water aquifers near the surface, driving up levels of contaminants in the water tenfold or more in some places.” What kind of contaminants could bubble up into drinking water aquifers? The study noted: “Potentially dangerous uranium and barium increased throughout the entire experiment in some samples.” This problem may not turn out to be fatal to CCS, but it might well limit the places where sequestration is practical, either because the geology of the storage site is problematic or because the site is simply too close to the water supply of a large population.
Public acceptance has already been a major problem for CCS. Public concern about CO2 leaks (small and large) has impeded a number of CCS projects around the world. Modest leaks risk water contamination, but large leaks can actually prove fatal because in high concentrations, CO2 can suffocate people. As BusinessWeek reported in 2008:
“One large, coal-fired plant generates the equivalent of 3 billion barrels of CO2 over a 60-year lifetime. That would require a space the size of a major oil field to contain. The pressure could cause leaks or earthquakes, says Curt M. White, who ran the US Energy Department’s carbon sequestration group until 2005 and served as an adviser until earlier this year. ‘Red flags should be going up everywhere when you talk about this amount of liquid being put underground’.”
With the use of hydraulic fracturing to produce natural gas in the United States, we have seen considerable concern about leakage of methane and other potentially harmful substances. There is a growing body of research linking hydraulic fracturing to earthquakes. That has been especially true for the so-called reinjection wells, where millions of gallons of wastewater from the fracturing process are injected deep underground, much as the carbon dioxide would be in CCS. Research published by Stanford University concluded in 2012:
We argue here that there is a high probability that earthquakes will be triggered by injection of large volumes of CO2 into the brittle rocks commonly found in continental interiors. Because even small- to moderate-sized earthquakes threaten the seal integrity of CO2 repositories, in this context, large-scale CCS is a risky, and likely unsuccessful, strategy for significantly reducing greenhouse gas emissions.
Concern about leaks helped kill one of the world’s first full CCS demonstrations of capturing, transporting, and storing carbon dioxide by the Swedish company Vattenfall in northern Germany. The project started operation in 2008. In 2009, Germany tried to introduce legislation that would have had the government assume liability for companies injecting carbon dioxide underground. The legislation failed to pass. Vattenfall did not get a permit to bury the carbon dioxide. As a result in July 2009, the plan “ended with CO2 being pumped directly into the atmosphere, following local opposition at it being stored underground.” In May 2014, the company announced that it was ending all CCS research.
Carbon capture and storage has a long way to go to become a major contributor to addressing the threat of climate change starting in the 2030s. We will need vastly more effort by the public and private sector if CCS is going to provide as much as 10% of the carbon dioxide emissions reductions needed by 2050.