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Building an Underground ‘Highway’ for Carbon Dioxide

by Lincoln Pratson | July 28th, 2008
posted by Erica Rowell (Editor)


Permalink | 8 comments
Engineers are working on ways to snag global warming pollution from the air, liquefy it and send it to underground storage sites through a pipeline network.

Reducing carbon emissions is key to combating global warming. You probably knew that. What you might not know is that scientists are working to develop a viable way to trap carbon dioxide (CO2) emissions, squeeze them into a liquid form, and then pipe that fluid somewhere it can be injected underground (see graphic below).

The process is called Carbon Capture and Sequestration (CCS), and it’s receiving considerable attention. It could allow us to cut emissions while still burning fossil fuels like coal for our electricity and other energy needs.

What Will the Pipeline Look Like?

 

While the first U.S. demonstration plants (like the recently canceled FutureGen project) will likely be built over a storage site, if the technology takes off, many power plants won’t be so well positioned. Studies indicate that locating future carbon-capturing plants close to areas with high electricity demand will be the most cost-effective.

 

 
(Montana Environmental Information Center)

Plus, since relatively new plants nowhere near sequestration sites already have expensive systems to trap smog-forming nitrogen dioxide and acid-rain producing sulfur dioxide, they will probably be retrofitted with carbon-capturing technologies rather than abandoned. So we’ll need significant infrastructure to connect those CO2 sources to underground sinks.

Who will build the pipeline network and what it will look like remain unclear (see analysis). But its makeup, in both form and investment, will likely be complex. Here’s a look at some of the complicating factors.

Multiple Players – Utilities alone are unlikely to shoulder the pipelines’ costs. Storage site operators in need of customers may be motivated enough to help connect them. Oil companies like ConocoPhillips are prepping to be among these operators, and where necessary for business they will help build pipelines. Pipeline operators themselves, like Kinder Morgan, which is experienced in helping develop a CO2 pipeline network for Enhanced Oil Recovery (see map below), are well positioned to grow a CCS network. And then there’s the federal government, which might build CO2 trunk lines to sequestration sites that power plants could tie in to.

 
CO2 pipelines in operation in the United States (European Energy Forum)

Sequencing – A CO2 pipeline network will take time to evolve. Here’s a likely scenario. Early-mover utilities will establish the network’s first nodes by building capture-ready power plants before carbon emissions have a price (from a cap or tax). When the price becomes high enough to make joining cost effective, the remaining plants will connect. Similarly, different sequestration sites will add onto the network as demand for storage rises along with storage costs.

Routing – Factors influencing the pipelines’ routes compound network uncertainty even more. Many new pipelines could end up following existing infrastructure (such as transmission lines and train tracks), as rights-of-way for these have already been established. Elsewhere it may be cheaper to forge new routes. In either case, new pipelines will require approval and regulation, the responsibilities for which are still being worked out between state and federal governments.

And then there is the issue of network redundancy. Multiple pathways from a power plant to one or more sequestration sites would ensure that the plant can discharge emissions, and sequestration sites can receive them and get paid for storing them, even if a segment of the network shuts down.

Geosequestration Potential – Finally, we need much more information about the capacity and costs of candidate storage sites. In some cases, the quality of available reservoirs may make shipping CO2 to a faraway site cheaper than storing it nearby. And if it turns out that there are one or two sites with exceptionally large and low-cost storage, it may be more economical to connect plants far and wide to an extended pipeline network that converges on these sites rather than build a more intricate, distributed network linking smaller groups of plants to the nearest sequestration sites.

A Big Pipeline With Huge Potential

 

Given these unknowns and others, it is too early to predict who will ante up the construction costs for a pipeline network and what form it will assume. One thing that probably can be counted on is that CCS will be much bigger than just the utilities and government. Along with it an industry will emerge. We should help promote this.

Consider that in 1994, then vice president Al Gore argued with Robert Allen, AT&T’s CEO at the time, over how to build the electronic superhighway, now of course known colloquially as the Internet. Gore thought government should build it; Allen deemed it a job for industry. Fourteen years later, the Internet is the product of industry and we can’t live without it. CCS will be expensive, but we need to cut emissions. Let’s similarly engage industry in the development of this CO2 super highway to bring it on as quickly, efficiently and economically as possible.

Lincoln F. Pratson is associate professor of sedimentary geology at the Nicholas School of the Environment at Duke University.

 

 

 

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8 Comments

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  1. Emily Sharp
    Oct 29, 2008

    It has been suggested that the carbon produced by coal plants will contain contaminants that will dramatically affect the performance of the pipeline. Others seem to think that this isn’t a problem, and that the pipelines as they currently exist will be fine. What do you think? ” title=”Contaminants

    • erica
      Oct 30, 2008

      Professor Pratson responds – I contacted my colleague here at Duke, Dr. Munish Chandel, who is working on the capture and transport side of CCS. He related to me that possible contaminants in CO2 captured from the power plants include H2S, water, N2, and oxygen. What the mix and fraction of contaminants are will depend on the flue gas characteristics and the process of CO2 capture. The presence of contaminants could indeed affect pipeline performance. For example, the presence of free water can lead to the formation of carbonic acid, which in turn can cause/enhance pipeline corrosion. As an example of what the limit to the volume of impurities permissible in the CO2 transport may be, here is the average composition of the CO2 captured by the Great Plains plant in North Dakota: *95+% Carbon Dioxide *1.1% Hydrogen Sulfide *1.0% Ethane *0.3% Methane *0.8% Other” title=”Contaminants could indeed affect pipeline performance

  2. Daniel Wedgewood
    Jul 28, 2008

    Professor Pratson – does the CO2 pipeline map show existing CO2 pipelines, or projected ones? Why is it centered around the midwest? Do you have a map of the U.S. that shows CO2 production – perhaps in a topological way? Thanks.” title=”CO2 Pipelines

    • Lincoln Pratson
      Jul 29, 2008

      Apologies for the slow reply, Daniel. I was in Washington D.C. yesterday discussing CCS with Congressional staffers and was not able to get to your inquiry until now. The map in my post shows the approximately 3,600 miles of CO2 pipelines operating in the U.S. today. These carry CO2 from naturally occurring underground reservoirs, natural gas processing facilities, ammonia manufacturing plants, and a large coal gasification project (the Great Plains Synfuels Plant in North Dakota — http://www.dakotagas.com/) to oil fields for use in Enhanced Oil Recovery (EOR). The pipelines are largely situated in the midwestern to western U.S. because that is where significant EOR is occurring. The map in my post indicates the CO2 sources –- they are the yellow areas ringed by a black line. Unfortunately, I don’t have a better map I can direct you to. However, see Congressional Research Service Report RL33971 for a more detailed analysis of how the existing CO2 pipelines might affect and be affected by emerging policy issues concerning large-scale development of CO2 transport infrastructure (http://opencrs.com/document/RL33971).” title=”CO2 pipelines

  3. James Wang
    Jul 28, 2008

    I heard a presentation by Jeff Bielicki at a scientific conference last December in which he explored the potential for sequestering CO2 within deep sea sediments. The ideal locations would be those where there is both a “negative buoyancy zone” and “hydrate formation zone,” which results in double trapping of the CO2. This occurs at a depth of greater than about 2700 meters, there seems to be widespread potential geographically, and particularly relevant is the fact that much of the population lives close to the coast. I don’t know what special environmental risks may be associated with sequestration in sediments though. Have you heard much about this form of sequestration, and if so, what is your opinion as to its potential and feasibility?” title=”CO2 seaways?

    • Lincoln Pratson
      Jul 29, 2008

      James, Jeff Bielicki of Harvard (http://www.people.fas.harvard.edu/~bielicki/) was kind enough to speak on this subject of CO2 within deep sea sediments at the Nicholas School as well. I find it to be a really innovative idea. I need to give more thought to what environmental risks there might be. Off-hand, I can’t think of many. Deep ocean currents along the U.S. East Coast can reach speeds fast enough to erode the sea floor, and there has been at least one occasion tens of millions of years ago (in the late Eocene to early Oligocene) when vigorous ocean-bottom circulation cut back the U.S. continental margin (the continental shelf and slope) by tens of kilometers. However, erosion by the deep currents today appears to be limited to remobilizing modern sediments, so CO2 buried 100 meters or more below the sea floor should be buffered. And the massive erosion that happened in the past occurred when climate was cooling not warming. There is the risk of catastrophic sea floor failures, which in the process of collapsing could disintegrate any embedded CO2 hydrates, but these avalanche-like events would also carry the CO2 deeper into possibly even colder waters where it would remain negatively buoyant. And then there is the possibility that warming of the oceans could melt the CO2 hydrates and might even warm deep-ocean CO2 accumulations so that they are no longer negatively buoyant. But if such warming occurs, we’re going to have more problems from the melting of methane hydrates than from the release of CO2, as methane is a more potent greenhouse gas and not good to breathe either. The biggest issue I see with Jeff’s idea, at least along the U.S. East Coast, is the low permeability (or connectivity of pore spaces between grains) of sea floor sediments at these water depths, sediments which tend to be muds. Without good permeability, it will be difficult to get the CO2 into the sediments. In fact, such muds provide an ideal cap for preventing CO2 from leaking from the subsurface back to the seafloor. Dave Goldberg and colleagues at Lamont-Doherty Earth Observatory of Columbia University have recognized this in suggesting that ocean-floor basalts adjacent to continents may be even better sequestration sites (see http://www.ldeo.columbia.edu/news-events/undersea-volcanic-rocks-may-offer-vast-repository-greenhouse-gas). Although hard rock, these basalts are commonly highly fractured and so can have decent permeability in certain regions. And CO2 reacts with basalt to form solid precipitates, providing yet another even more stable mechanism for trapping the gas. While not as widespread along continents as sediments, ocean-floor basalts may be an excellent first place to test just how good ocean floor sequestration could be. ” title=”CO2 seaways

      • Jeff Bielicki
        Jul 31, 2008

        Hi Lincoln, Hi James, To clarify, my talks about storing CO2 in deep sea sediment at the AGU annual meeting in December, Duke in May, and elsewhere, are based on the work by some colleagues of mine that was published in 2006: House et al, (2006). “Permanent Carbon Dioxide Storage in Deep Sea Sediments” Proceedings of the National Academy of Sciences, 103(33): 12291-12295. The negative bouyancy and hydrate formation zones are described in their paper. In my talks I introduce their idea and then present if/how we can get CO2 to the locations where these trapping mechanisms operate. I agree with Lincoln… permeability can be an issue and basalt storage can be advantageous in this respect. Basalt storage also has the added advantage that mineralization reactions can occur. If the basalt is located in the seafloor CO2 will mix with the seawater and react with the basalt to form carbonate minerals, and, in deep enough water, CO2 can be gravitationally trapped (negative buoyancy zone) and CO2 hydrates can form (hydrate formation zone). Dave Goldberg and his colleagues describe this in: Goldberg, D. et al (2008). “Carbon Dioxide Sequestration in Deep-Sea Basalt.” Proceedings of the National Academy of Sciences, 105(29): 9920-9925.” title=”CO2 Storage in Deep Sea Sediment

        • Lincoln Pratson
          Aug 1, 2008

          Many thanks Jeff. Your excerpt:encoded of the apparent advantages of CO2 storage in subsea basalts described by Dave Goldberg and colleagues is more complete than mine. I would just add that as Dave et al point out, the low permeability sediment drape blanketing the top of these basalts provides yet another trap inhibiting CO2 leakage were the gas stored in the basalts.” title=”CO2 Storage in Deep Sea Sediment

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