The Scientific American article “Can we bury global warming?” [click the thumbnail for PDF download] is a useful lay-person overview of the benefits and challenges of carbon sequestration. Included are examples of test-projects underway, and 3D diagrams of typical subsurface configurations.
Though I don’t know what the total annual rate of CO2 storage is today, there are carbon dioxide capture and storage (CCS) projects operational around the world. E.g., from my time in Norway, I know that Statoil [the Norwegian state oil company] has been storing on the order of 1,000,000 tons of CO2/annum from the Sleipner West field by injecting it into a saline aquifer. This is CO2 stripped from natural gas. Norway has a CO2 tax, so the Statoil operating costs net out near zero.
The sub-surface CO2 storage techniques are similar to those of oil or gas field production enhanced-recovery methods using gas injection to increase reservoir pressures. When an enhanced-recovery candidate reservoir is suitable for CO2 storage, some of the CSS operating cost can be recovered from the increased production. The CSS function may even be profitable.
But isn’t there a worry about the CO2 leaking back into the atmosphere? Storing CO2 in geologic strata is not a forever solution – for suitable storage reservoirs we’re talking about leakage rates over hundreds of years. For sure we must avoid selecting a reservoir that has a meaningful probability of catastrophic release. Slow leakage over 200 – 500 years should be OK. I think of CSS as a pragmatic way to defer near-term carbon loading until we develop better and more economic solutions in the future. Rather like deferring taxation to be paid with future depreciated dollars.
I think it’s good policy to encourage industry to expand CSS projects. Above a certain size, the target reservoir must be licensed to ensure that best-practice will NOT result in catastrophic release, and long term release is low enough to earn the incentive. As to cost reductions I suspect this is a “learn by doing” technology. If I’m correct about that, economic incentives [such as carbon taxes] are all that is needed to promote CSS applications. I speculate that significant progress will be made both in the economics of CSS, and the longevity of the storage.
Meanwhile, we are likely to dream up more cost-effective ways to take carbon out of the atmosphere. Ray Kurzweil might argue that, given his outlook for exponential technology progress, “it won’t be that long, mate!”
E.g.,here’s an idea from my geologist mate James: very-large-scale tree farming, where the captured carbon is stored in the resulting timber. If we can’t find enough economic applications for the timber product, we can simply stack the trees for future use.
A useful part of this article is the discussion of CSS cost increases [over doing nothing] from the perspective of consumer [20%], electrical generator [50%], and coal producer [300%]:
To get a feel for the economic pressures the extra cost of carbon sequestration would place on the coal producer, the power plant operator and the home owner who consumes the electricity, it helps to choose a reasonable cost estimate and then gauge the effects. Experts calculate that the total additional expense of capturing and storing a ton of carbon dioxide at a coal gasifi cation combined-cycle plant will be about $25. (In fact, it may be twice that much for a traditional steam plant using todayâ€™s technology. In both cases, it will cost less when new technology is available.)
The coal producer, the power plant operator and the home owner will perceive that $25 cost increase quite differently. A coal producer would see a charge of about $60 per ton of coal for capturing and storing the coalâ€™s carbon, roughly tripling the cost of coal delivered to an electric utility customer. The owner of a new coal power plant would face a 50 percent rise in the cost of power the coal plant puts on the grid, about two cents per kilowatt-hour (kWh) on top of a base cost of around four cents per kWh. The home owner buying only coal-based electricity, who now pays an average of about 10 cents per kWh, would experience one-fi fth higher electricity costs (provided that the extra two cents per kWh cost for capture and storage is passed on without increases in the charges for transmission and distribution).
The key points of this article:
â€¢ A strategy that combines the capture of carbon dioxide emissions from coal power plants and their subsequent injection into geologic formations for longterm storage could contribute significantly to slowing the rise of the atmospheric CO2 concentration.
â€¢ Low-cost technologies for securing carbon dioxide at power plants and greater experience with CO2 injection to avoid leakage to the surface are key to the success of large-scale CO2 capture and storage projects.
â€¢ Fortunately, opportunities for affordable storage and capture efforts are plentiful. Carbon dioxide has economic value when it is used to boost crude oil recovery at mature fi elds. Natural gas purification and industrial hydrogen production yield CO2 at low cost. Early projects that link these industries will enhance the practitionersâ€™ technical capabilities and will stimulate the development of regulations to govern CO2 storage procedures.
The author is Robert H. Socolow, who is professor of mechanical and aerospace engineering at Princeton University. He teaches in both the School of Engineering and Applied Science and the Woodrow Wilson School of Public and International Affairs. A physicist by training, Socolow is currently co-principal investigator (with ecologist Stephen Pacala) of the universityâ€™s Carbon Mitigation Initiative, supported by BP and Ford, which focuses on global carbon management, the hydrogen economy and fossil-carbon sequestration. In 2003 he was awarded the Leo Szilard Lectureship Award by the American Physical Society.