Carbon capture and storage (CCS), alternatively referred to as carbon capture and sequestration, is a means of mitigating the contribution of fossil fuel emissions to global warming, based on capturing carbon dioxide (CO2) from large point sources such as fossil fuel power plants, and storing it in such a way that it does not enter the atmosphere. It can also be used to describe the scrubbing of CO2 from ambient air as a geoengineering technique. “Carbon capture and storage” has also been used to describe biological capture and subsequent storage of atmospheric CO2, such as the burial of “biochar”—the end product of “pyrolysis”, the decomposition of organic material by heat in the absence of oxygen. However, the term is more conventionally applied to non-biological methods of capturing carbon dioxide from combustion at the source. Although CO2 has been injected into geological formations for various purposes, the long term storage of CO2 is a relatively new concept. The first commercial example is Weyburn in 2000, and a couple doze other small-scale pilot CCS plants have followed since. CCS applied to a modern conventional power plant could reduce CO2 emissions to the atmosphere by approximately 80-90% compared to a plant without CCS. The IPCC estimates that the economic potential of CCS could be between 10% and 55% of the total carbon mitigation effort until year 2100 (Section 8.3.3 of IPCC report.) And yet, capturing and compressing CO2 requires much energy and would increase the fuel needs of a coal-fired plant with CCS by 25%-40%. A general problem is that long term predictions about submarine or underground storage security are very difficult and uncertain and CO2 might leak from the storage into the atmosphere. In the United States, president Obama has directed the Department of Energy to propose a plan to bring “5 to 10 commercial demonstration projects online by 2016.” Chu explained in his Science editorial why he believes CCS is necessary: “This is an aggressive goal, but the climate problem compels us to act with fierce urgency”. According to the EPA, on top of the $3.4 billion in Recovery Act money already committed, the industry is expected to put up $7 billion more in 2010. These considerations and the main pro and con arguments are examined below.
George Monbiot, Visiting Professor of Planning at Oxford Brookes University, wrote in his 2007 book Heat: How to Stop the Planet from Burning: “[E]ven if we continued to produce most of our electricity from burning fossil fuels, we could, at least in theory, cut carbon emissions by 80 or 85 percent. The technology that would make this possible is called ‘carbon capture and storage. This means stripping the carbon out of the fuel either before or after it is burnt, and burying it in the hope that it will stay where it’s put.”
“Action is urgently required but what can we do now which will allow business to continue as reliably as usual – increase wind power 40 fold, increase solar power 700 fold while simultaneously reducing dependency on coal by a similar amount and halving the fuel consumption of two billion cars? Of course we must improve the efficiency of our energy consumption as well as further developing solar, wind, wave and other renewable power sources, not to forget significantly reducing deforestation. But will fossil fuels cease to be used in the short or even medium term? No, fossil fuels are just too easy to use. The physical, social and legislative infrastructures are well established. The energy concentration is too dense for an energy hungry world to ignore, even if finding new deposits of light oil (and gas) is getting ever more difficult. We accept that a sustainable future demands that we switch to renewable energy sources as fast as possible. In the meantime CCS provides a way to minimise emissions of greenhouse gases.”
“Perhaps the only way to reduce warming enough to minimize the rise of the oceans is an all-out effort that also includes burning biomass as fuel (either to replace coal or gasoline or both) and pairing it with CO2 capture and storage. Together, they could suck down greenhouse gas levels by 180 ppm—more than enough to bring us below pre-industrial levels. As a result, sea level rise is held to just 10 centimers by 2100, according to the author’s modeling.”
George Monbiot, Visiting Professor of Planning at Oxford Brookes University, wrote in his 2007 book Heat: How to Stop the Planet from Burning: “I have come to believe that this technology… can, with sufficient political commitment, be widely deployed before 2030.”
George Monbiot, Visiting Professor of Planning at Oxford Brookes University, wrote in his 2007 book Heat: How to Stop the Planet from Burning: “The difficulties I have encountered with investigating the other [low-carbon] technologies have persuaded me that carbon capture and storage – while it cannot provide the whole answer – can and must be one of the means we use to make low-carbon electricity.”
“To make CCS available as a reasonably well-proven option by around 2020, a first tranche of demonstration plants need to be deployed as quickly as possible. A second, larger tranche of reference plants then needs to continue the learning process and demonstrate the technology at scale and ready for multiple repeat orders. After this second tranche, CCS should be ready to contribute to a rapid decarbonization of the electricity supply from coal, natural gas, and biomass power plants in developed countries in the decade 2020–2030.”
A few engineering proposals have been made for the more difficult task of capturing CO2 directly from the air, but work in this area is still in its infancy. Global Research Technologies demonstrated a pre-prototype in 2007. Capture costs are estimated to be higher than from point sources, but may be feasible for dealing with emissions from diffuse sources like automobiles and aircraft. The theoretically required energy for air capture is only slightly more than for capture from point sources. The additional costs come from the devices that use the natural air flow. Removing CO2 from the atmosphere is a form of geoengineering by greenhouse gas remediation.
Ocean storage Another proposed form of carbon storage is in the oceans. Several concepts have been proposed: ‘dissolution’ injects CO2 by ship or pipeline into the water column at depths of 1000 m or more, and the CO2 subsequently dissolves. ‘lake’ deposits CO2 directly onto the sea floor at depths greater than 3000 m, where CO2 is denser than water and is expected to form a ‘lake’ that would delay dissolution of CO2 into the environment. convert the CO2 to bicarbonates (using limestone) Store the CO2 in solid clathrate hydrates already existing on the ocean floor, or growing more solid clathrate.
George Monbiot, Visiting Professor of Planning at Oxford Brookes University, wrote in his 2007 book Heat: How to Stop the Planet from Burning: “There are good reasons to suppose that once carbon dioxide has been properly buried in the right sites, it will stay where it is put.”
David Hawkins, director of the climate center at the Natural Resources Defense Council (NRDC): “The reason that we believe CCS is a critically important part of the toolbox is there’s a huge gap between what can technically do and what we are doing, and part of that is politics.”
Peter Montague, PhD Executive Director of the Environmental Research Foundation. “Carbon Sequestration: What’s the Point?” December 1, 2008: “The ideal solution [to global climate change] would be to stop making waste CO2 by phasing out fossil fuels and getting our energy from solar power in all its forms (direct sunlight, wind, and hydro dams). We know how to do this today… Every engineer knows that avoiding waste is far better than managing waste. So CCS is fundamentally bad design.”
Peter Montague, PhD Executive Director of the Environmental Research Foundation. “Carbon Sequestration: What’s the Point?” December 1, 2008: “Sooner or later we’re going to run out of fossil fuels – all of them – so eventually we have to adopt solar power. CCS just delays the inevitable – a huge waste of time and money. We should skip CCS and go solar today.”
“Let’s take the first problem. Capturing carbon dioxide from the flue gas of a coal-fired electric generation plant is an energy-intensive process. Analysts estimate that capturing the carbon dioxide cuts the output of a typical plant by as much as 28 percent. Given that the global energy sector is already straining to meet booming demand for electricity, it’s hard to believe that the United States, or any other country that relies on coal-fired generation, will agree to reduce the output of its coal-fired plants by almost a third in order to attempt carbon capture and sequestration.”
Greenpeace International, an environmental non-profit organization, stated the following in a May 2008 report authored by Emily Rochon et al., titled “False Hope: Why Carbon Capture and Storage Won’t Save the Climate,” available at www.greenpeace.org: “Spending money on CSS is diverting urgent funding away from renewable energy solutions for the climate crisis… investing in a renewable energy future would save US$180 billion annually and cut CO2 emissions in half by 2050.”
Greenpeace International, an environmental non-profit organization, stated the following in a May 2008 report authored by Emily Rochon et al., titled “False Hope: Why Carbon Capture and Storage Won’t Save the Climate,” available at www.greenpeace.org: “Letting CCS be used as a smokescreen for building new coal-fired power stations is unacceptable and irresponsible. ‘Capture ready’ coal plants pose a significant threat to the climate. The world can fight climate change but only if it reduces its dependence on fossil fuels, particularly coal. Renewable energy and energy efficiency are safe, cost effective solutions that carry none of the risks of CCS, and are available today to cut emissions and save the climate.”
Rainforest Action Network, an environmental non-profit organization, stated the following in a fact sheet on its website titled “The Dirty Truth about Clean Coal,” available at www.ran.org (accessed Sep. 17, 2009): “CCS remains a ‘smoke and mirrors’ show – keeping attention away from real solutions. With global warming accelerating, we need to make smart energy choices now. Keeping fossil fuels in the ground is key to stopping climate change.”
Rainforest Action Network, an environmental non-profit organization, stated the following in a fact sheet on its website titled “The Dirty Truth about Clean Coal,” available at www.ran.org (accessed Sep. 17, 2009): “The concept of CCS is that we can curb climate change by capturing the emissions from coal plants and store them underground, safely away from our atmosphere for eternity. The most glaring flaw in this concept is that CCS technology is not likely to be a commercially viable option for at least another decade, and new coal-fired plants are slated to begin construction now. There are also no working models of CCS at a commercial-scale power plant anywhere in the world.”
Rainforest Action Network, an environmental non-profit organization, stated the following in a fact sheet on its website titled “The Dirty Truth about Clean Coal,” available at www.ran.org (accessed Sep. 17, 2009): “Proposals for carbon storage locations include underground depleted oil and gas fields, unmineable coal seams, and even in our oceans. Underground storage of the 1.9 billion tons of C02 waste produced annually by U.S. coal plants is hugely problematic and likely impossible.”
IPCC has provided estimates of air emissions from various CCS plant designs (see table below). While CO2 is drastically reduced (though never completely captured), emissions of air pollutants increase significantly, generally due to the energy penalty of capture. Hence, the use of CCS entails a reduction in air quality.
Vaclav Smil, PhD, Distinguished Professor in the Faculty of Environment at the University of Manitoba, stated the following in his May 2006 statement “Energy at the Crossroads,” during the Conference on Scientific Challenges for Energy Research in Paris, available at www.home.cc.umanitoba.ca: “The obvious question is why it should be even attempted given the fact that a 10% reduction in CO2 emissions could be achieved by several more rational, mature and readily available adjustments… [T]technical fixes cannot provide a lasting resolution. History shows that energy demand keeps growing even in the most energy-saturated affluent societies: encouraging worldwide diffusion of this trend (new China, and then India, aspiring to replicate the US) and trying to fill the supply through scientific and engineering ingenuity is not a formula compatible with maintaining a viable biosphere. Obviously, poor countries need more energy; but the rich ones should, sooner, rather than later, think about engineering rational reductions in energy use. All economies are just subsystems of the biosphere and the first law of ecology is that no trees grow to heaven. If we are not going to engineer thoughtful, gradual reductions, we run a considerable risk that the biosphere may do the scaling-down for us in a much less desirable (if not catastrophic) manner.”
John Deutch, PhD, Institute Professor of the Department of Chemistry at the Massachusetts Institute of Technology, and Ernest J. Moniz, PhD, Director of Energy Studies at the Laboratory for Energy and the Environment at the Massachusetts Institute of Technology, stated in their 2007 study, “The Future of Coal: Options for a Carbon-Constrained World,” available at www.web.mit.edu: “A number of geological reservoirs appear to have the potential to store many 100’s – 1000’s of gigatons of CO2. The most promising reservoirs are porous and permeable rock bodies, generally at depths, roughly 1 km, at pressures and temperatures where CO2 would be in a supercritical phase. Once in the pore, over a period of tens to hundreds of years, the CO2 will dissolve into other pore fluids, including hydrocarbon species (oil and gas) or brines, where the CO2 is fixed indefinitely, unless other processes intervene. Over longer time scales (hundreds to thousands of years) the dissolved CO2 may react with minerals in the rock volume to precipitate the CO2 as new carbonate minerals… [I]t is very likely that the fraction of stored CO2 will be greater than 99% over 100 years, and likely that the fraction of stored CO2 will exceed 99% for 1000 years… Our overall judgment is that the prospect for geological CO2 sequestration is excellent. We base this judgment on 30 years of injection experience and the ability of the earth’s crust to trap CO2… The DOE should launch a program to develop and deploy large-scale sequestration demonstration projects.”
“Shaffer calculates, if the leakage rate is 1% every 10 years, by 5000 AD mean atmosphere warming will be as bad as if no storage had been attempted. Dial that leakage rate down to 1% every 100 years, and we get to 20,000 AD before atmospheric warming is as bad as no storage at all. 20,000 AD? By this point humankind will surely be on other planets or, more likely, extinct. But Shaffer is concerned about future generations in 20,000 AD. He points out that nuclear waste management works on these timescales – tens of thousands of years. […] Yes, as Shaffer says, a leaky store will create delayed warming in the future. But what a comfortingly long way away that future is, in his projections. Moreover, he considers that future humans make no attempt at re-sequestering escaped carbon dioxide. And he does not suggest that today we might try both to capture carbon dioxide underground and reduce our fossil fuel emissions. And aren’t there many more pressing practical concerns about carbon capture and storage to consider right now – such as whether it works over a hundred years, not whether it works over tens of thousands of years?”
For well-selected, designed and managed geological storage sites, the IPCC estimates that CO2 could be trapped for millions of years, and the sites are likely to retain over 99% of the injected CO2 over 1,000 years. In 2009 it was reported that scientists had mapped 6,000 square miles (16,000 km2) of rock formations in the U.S. that could be used to store 500 years’ worth of U.S. carbon dioxide emissions.
A major concern with CCS is whether leakage of stored CO2 will compromise CCS as a climate change mitigation option. For well-selected, designed and managed geological storage sites, IPCC estimates that risks are comparable to those associated with current hydrocarbon activity. CO2 could be trapped for millions of years, and although some leakage occurs upwards through the soil, well selected stores are likely to retain over 99% of the injected CO2 over 1000 years. Leakage through the injection pipe is a greater risk. Although the injection pipe is usually protected with Non-return valves (to prevent release on a power outtage), there is still a risk that the pipe itself could tear and leak due to the pressure. A small incident of this type of CO2 leakage was the Berkel and Rodenrijs incident in December 2008, where a modest release of greenhouse gas emissions resulted in the deaths of a small group of ducks. In order to measure accidental carbon releases more accurately and decrease the risk of fatalities through this type of leakage, the implementation of CO2 alert meters around the project perimeter has been proposed. In 1986 a large leakage of naturally sequestered carbon dioxide rose from Lake Nyos in Cameroon and asphyxiated 1,700 people. While the carbon had been sequestered naturally, some point to the event as evidence for the potentially catastrophic effects of sequestering carbon. The Lake Nyos disaster resulted from a freak volcanic event one night, which very suddenly released as much as a cubic kilometre of CO2 gas from a pool of naturally occurring CO2 under the lake in a deep narrow valley. The location of this pool of CO2 is not a place where man can inject or store CO2 and this pool of CO2 was not known about nor monitored until after the occurrence of the natural disaster.
Peter Montague, PhD Executive Director of the Environmental Research Foundation. “Carbon Sequestration: What’s the Point?” December 1, 2008: “Instead of solving the CO2 problem that we’ve created, CCS would pass the problem along to our children and their children and their children’s children. Basically, buried CO2 could never be allowed to leak back out. We should take responsibility for our own problems, not pass them to our children to manage. Scientists paid by the fossil fuel companies say the CO2 will never leak back out of the ground. What if they’re mistaken? Then our children will inherit a hot, acid-ocean, ruined world.”
The environmental effects of oceanic storage are generally negative, and poorly understood. Large concentrations of CO2 kills ocean organisms, but another problem is that dissolved CO2 would eventually equilibrate with the atmosphere, so the storage would not be permanent. Also, as part of the CO2 reacts with the water to form carbonic acid, H2CO3, the acidity of the ocean water increases. The resulting environmental effects on benthic life forms of the bathypelagic, abyssopelagic and hadopelagic zones are poorly understood. Even though life appears to be rather sparse in the deep ocean basins, energy and chemical effects in these deep basins could have far reaching implications. Much more work is needed here to define the extent of the potential problems.
Rainforest Action Network, an environmental non-profit organization, stated the following in a fact sheet on its website titled “The Dirty Truth about Clean Coal,” available at www.ran.org (accessed Sep. 17, 2009): “Who pays if sequestered carbon leaks and causes fatalities or other damages? Even proponents of CCS have said the technology won’t go ahead unless the federal government assumes full liability. If that happens, our tax dollars would be spent protecting utility companies from bearing both the risk and the cost of coal.”