# Contents * the following line creates the automatic table of contents {:toc} ##The idea ## **Carbon capture and storage**, also known as **carbon capture and sequestration** or **CCS**, describes a variety of ways to reduce the carbon dioxide emitted by burning fossil fuels. Most commonly it refers to methods based on capturing carbon dioxide from large point sources such as fossil fuel power plants and storing it so that it does not enter the atmosphere. It also refers to ways of removing CO₂ directly from ambient air, for example by biological methods such as [[biochar]]. In the following paper: * D'Alessandro <i>et al</i>, Carbon dioxide capture: prospects for new materials, _Angew. Chemie Int. Ed._ <b>49</b> (2010), 2--27. the authors summarize two of the key issues as follows: : Two points must first be made with respect to capture materials and potential capture technologies, given the sheer magnitude of global CO₂ emissions. First, any chemical employed to capture CO₂ will rapidly exhaust its global supplies if it is used in a once-through manner; and second, any chemical produced from CO₂ as a reactant will rapidly saturate global markets for that chemical. These considerations underscore the necessity that capture materials must be regenerable. In this case the energy input for regeneration is one of the key factors in determining the efficiency and cost. ## List of methods ## +-- {: .standout} We need a listing of different methods of CCS. What follows is a start. Then: how they work, how well they can be scaled up, and some scientific and engineering challenges that need to be addressed for each one! =-- ### Injection into the ground ### One widely studied approach to CCS is simply injecting CO₂ into the ground. See: * National Academy of Engineering (NAE) and Board on Energy and Environmental Systems (BEES), _The Carbon Dioxide Dilemma: Promising Technologies and Policies_. Franklin M. Orr, [Sequestration via injection of carbon dioxide into the deep earth](http://www.nap.edu/openbook.php?record_id=10798&page=17). In 1991, Norway became the first country in the world to impose a federal tax on atmospheric CO₂ emissions from operations such as coal-fired power plants. Later this tax of &#36;55 of per ton of CO₂ was extended to cover offshore oil and gas production. This motivated Norwegians to set up an operation called **Sleipner** which strips CO₂ from natural gas offshore in the North Sea and reinjects 0.3 megatons of carbon a year into a non–fossil-fuel–bearing formation. This is apparently the world's largest carbon capture and storage project. However, a one-gigaton '[[stabilization wedges|wedge]]' would require building 3500 Sleipner-sized projects (or fewer, larger projects). <div align="center"> <img width="500" src="http://www.bellona.org/imagearchive/Utsira.JPG" alt="" /> </div> For more details, see: * [Sleipner gas field](http://en.wikipedia.org/wiki/Sleipner_gas_field), Wikipedia. * James W. Johnson, [A solution for carbon dioxide overload](https://www.llnl.gov/str//Johnson.html), _[Science and Technology](https://www.llnl.gov/str//12.00.html)_ , December 2000. For safety issues, see these comments on the Sleipner project: * Bellona, Factsheet: [Security of CO2 storage in Norway](http://www.bellona.org/factsheets/1191928198.67). Among other things, they write: >The injected CO₂ will potentially be trapped by geochemical processes. Solubility trapping has the effect of eliminating the buoyant forces that drive CO₂ upwards, and through time it can lead to mineral trapping, which is the most permanent and secure form of geological storage. ### Solubility trapping### **Solubility trapping** is where the CO₂ dissolves in water. It’s harder for the CO₂ to escape the reservoir when it’s dissolved, rather than just sitting on top of water in a light buoyant phase. The solution itself sinks deeper and more securely into the reservoir, because it’s heavier with CO₂ in it. **Mineral trapping** is where the CO₂ chemically reacts with minerals so that carbon gets sequestered in stable, solid precipitates. On [Azimuth](http://johncarlosbaez.wordpress.com/2010/11/23/stabilization-wedges-part-2/#comment-2754), [[John Furey]] writes: +-- {: .quote} I don't have any confidence in high volume injection over the long term. Our species has been geologically injecting at all only about 50 years. The ground underneath our feet is not in homogeneous layers, contrary to the cartoons comprising most all modeling, and even if it were there are unpredictable side effects at any given site. If you've been following the news about fracking, you're aware that the most experienced corporations with the most economic incentives to do things right environmentally fail miserably because they do not really understand even shallow injection: * [A colossal fracking mess](http://www.vanityfair.com/business/features/2010/06/fracking-in-pennsylvania-201006), _Vanity Fair_. Of course leaking, contamination, etc is to be expected (rational i.e. calculated risks). What is not being reported is volcanos of fracking fluids kilometers from injection sites. They scratch their heads, close that well, and move over horizontally a little bit. =-- Hank Roberts writes: +-- {: .quote} Worry seems to be that old oil and gas fields will have had lots of old wells drilled over time -- often not mapped or recorded -- plugged with concrete and abandoned, and increasing CO2 pressure will accelerate failure: * [http://www.google.com/search?q=gas+well+concrete+plug+co2+damage](http://www.google.com/search?q=gas+well+concrete+plug+co2+damage) =-- Here are some further references discussing trapping mechanisms and sometimes failure modes: * Plains CO₂ Reduction Partnership, [Factors affecting the potential for CO2 leakage from geologic sinks](http://www.undeerc.org/pcor/newsandpubs/pdf/FactorsAffectingPotential.pdf), October 2005. Here is the executive summary: +-- {: .quote} The success of geologic carbon dioxide (CO₂) sequestration as a large-scale carbon management strategy is critically dependent on the ability of the geologic sinks and trapping mechanisms to confine the injected CO₂ for hundreds to thousands of years. Leakage of CO₂ from geologic sinks could result in significant release of the CO₂ back to the atmosphere, potentially reducing, if not negating altogether, the benefits of geologic CO₂ sequestration. For example, a leakage rate of 1% per year from 1 billion tons of geologically stored CO₂ (10 million tons) would exceed the current annual CO2 emissions from all the power plants in North Dakota (4 million tons). Further, leakage could have negative ecological effects and present the potential for health problems other than global warming. Clearly, the more CO₂ that is stored, the greater the potential that leakage from geologic sinks could result in adverse environmental and atmospheric impacts. It has recently been proposed that leakage rates of 0.01% per year be established as a performance requirement for geologically sequestered CO2 (White et al., 2003). This report provides an analysis of how the physicochemical properties of CO₂ would affect its trapping potential and mobility in various types of geologic environments. Analog studies of geologic environments containing large, concentrated amounts of CO₂ or hydrocarbons gas were also used to derive insight regarding the leakage processes that would be inherent in geologic CO₂ sequestration. The analogs included a) naturally occurring deposits of high-purity CO₂, b) a mature CO2 flood enhanced oil recovery (EOR) project, c) an aquifer natural gas storage reservoir, and d) coalbed natural gas deposits. Injected CO₂ can be trapped in geologic sinks by four types of mechanisms. Different types of geologic sinks in combination with their site-specific properties would trap CO₂ by different mechanisms. More than one type of trapping mechanism would typically be present in a single geologic sink. Most trapping mechanisms do not permanently immobilize CO₂. Thus leakage of CO₂ to the surface can potentially occur from all types of geologic sinks. In the right types of geologic settings, a large, concentrated amount of CO₂ could be stored for a geologically long time period without the risk of significant CO₂ leakage to the surface. The dominant, but by no means sole, barrier to CO₂ leakage to the surface from geologic sinks is not the trapping mechanism(s) but rather the permeability characteristics of the rock layers overlying or adjacent to the geologic sinks. The hydrologic properties of the formations containing the geologic sinks would also affect the potential for CO₂ leakage. Geologic settings with relatively static hydrology, i.e., low formation. =-- * Stuart M. V. Gilfillan _et al._, [Solubility trapping in formation water as dominant CO2 sink in natural gas fields](http://www.geos.ed.ac.uk/research/subsurface/diagenesis/Gilfillan_Nature_09.pdf), _Nature Letters_ **458** (2009), 614-618. >Injecting CO2 into deep geological strata is proposed as a safe and economically favourable means of storing CO2 captured from industrial point sources. It is difficult, however, to assess the long-term consequences of CO2 flooding in the subsurface from decadal observations of existing disposal sites. Both the site design and long-term safety modelling critically depend on how and where CO2 will be stored in the site over its lifetime. Within a geological storage site, the injected CO2 can dissolve in solution or precipitate as carbonate minerals. Here we identify and quantify the principal mechanism of CO2 fluid phase removal in nine natural gas fields in North America, China and Europe, using noble gas and carbon isotope tracers. The natural gas fields investigated in our study are dominated by a CO2 phase and provide a natural analogue for assessing the geological storage of anthropogenic CO2 over millennial timescales. We find that in seven gas fields with siliciclastic or carbonate-dominated reservoir lithologies, dissolution in formation water at a pH of 5–5.8 is the sole major sink for CO2. In two fields with siliciclastic reservoir lithologies, some CO2 loss through precipitation as carbonate minerals cannot be ruled out, but can account for a maximum of 18 per cent of the loss of emplaced CO2. In view of our findings that geological mineral fixation is a minor CO2 trapping mechanism in natural gas fields, we suggest that long-term anthropogenic CO2 storage models in similar geological systems should focus on the potential mobility of CO2 dissolved in water. * [CO2 Capture Project](http://www.co2captureproject.org/co2_trapping.html), website. * NETL Simulation/Risk Assessment Best Practice Manual (draft, 17 June 2010), [Appendix 1: brief summary of CO2 trapping mechanisms](http://www.interpartnership.org/appendix.pdf). * Kjetil Haugen and Abbas Firoozabadi, [CO2 injection in the subsurface](http://www.eng.yale.edu/aflab/pdf/CO2Injection.pdf). ### Direct capture from the air ### In capturing CO₂ from point sources, the dominant cost is supposedly the cost of capture rather than storage. However, [[David Keith]] has argued that direct capture from the air could be viable: * David Keith, [Direct capture of CO2 from the air](http://people.ucalgary.ca/~keith/Misc/AC%20technology%20Feb%202009.pdf), February 2009. * David Keith, Why capture CO₂ from the atmosphere? _[Science](http://www.sciencemag.org/cgi/content/abstract/325/5948/1654)_, **325** (September 2009), 1654--1655. ### Enhanced weathering ### One of the main long-term mechanisms that removes carbon dioxide from the ocean and atmosphere is the natural weathering of rocks. We can vastly accelerate this process by digging up suitable rocks, crushing them into powder and spreading them around. The rock dust then 'weathers' by reacting with carbon dioxide. This method of carbon capture and storage is called **enhanced weathering**. In principle it can also serve as a source of [[carbon negative energy]]. For more details, see [[Enhanced weathering]]. ### Cement manufacture ### The manufacture of ordinary Portland cement uses a large proportion of limestone. This is heated in a kiln, driving off the CO₂. By replacing the calcium from limestone with magnesium from minerals such as serpentine it is possible to make the manufacture low- or even negative-carbon, producing a cement which has similar properties. Annual world production of cement, 2010, is around 2 billion tonnes. See: * Celtic Cement, [Cenin](http://www.celticcement.com/assessment.html). ### Making methanol ### This is not exactly a form of carbon capture and _storage_, but related. See [[Methanol economy]]. ### Coal bed methane extraction ### Disused and uneconomic coal mines continue to emit methane. They can also be used to sequester carbon dioxide. Coal has a stronger affinity for CO₂ than methane. So, putting CO₂ in mine shafts displaces the methane, which can be captured and used as it rises to the surface. This idea is called **coal bed methane extraction**. It may constitute a source of [[carbon negative energy]]. See: * [Coalbed methane](http://en.wikipedia.org/wiki/Coalbed_methane), Wikipedia. * [Coal bed methane extraction](http://en.wikipedia.org/wiki/Coal_bed_methane_extraction), Wikipedia. * [Virginia Center for Coal and Energy Research](http://www.vtnews.vt.edu/articles/2008/12/2008-791.html). ### Methane hydrate reactions ### Another idea, due perhaps to 'Uncle Al' of internet fame, is to pump liquid CO₂ into methane hydrate formations. He claims that the recovered natural gas plus sequestered CO₂ has net zero carbon footprint. The reactions involved are CH₄ + $n$H₂O(s) $\to$ CH₄(g) + $n$H₂O(l) + 54.44 kJ/mol gas CO₂ + $n$H₂O(s) $\to$ CO₂(g) + $n$H₂O(l) + 63.6 kJ/mol gas For more on the chemistry of methane hydrates (also known as methane clathrates), see * John J. Carroll, [An introduction to gas hydrates](http://www.telusplanet.net/public/jcarroll/HYDR.HTM) * [Methane clathrate](http://en.wikipedia.org/wiki/Methane_clathrate), Wikipedia. ## Carbon capture and storage for coal-fired power plants ## See the page [[Carbon capture and storage for coal-fired power plants]]. ## References ## For starters, try: * [Carbon capture and storage](http://en.wikipedia.org/wiki/Carbon_capture_and_storage), Wikipedia. * [The Carbon Capture Report](http://www.carboncapturereport.org/) --- daily reports, daily newspaper and analytics from the University of Illinois. * [ICO2N](http://www.ico2n.com/about) --- the Integrated CO2 Network, a group of Canadian companies representing multiple industries, including coal and the oil sands. All ICO_2­N member companies claim to have a strong interest in developing carbon capture and storage. Other references: * Interagency Task Force on Carbon Capture and Storage, [Final report](http://www.fossil.energy.gov/programs/sequestration/ccstf/CCSTaskForceReport2010.pdf), 2010, USA --- a series of recommendations on overcoming the barriers to the widespread, cost-effective deployment of CCS within ten years. [[!redirects carbon capture and storage]] [[!redirects carbon capture and storage]] [[!redirects carbon capture and sequestration]] [[!redirects Carbon capture and sequestration]] [[!redirects CCS]] category: carbon