Carbon capture and storage

Carbon capture and storage (CCS) 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 away from the atmosphere by different means. It can also be used to describe the scrubbing of CO₂ from ambient air as a geoengineering technique.

Bio Carbon Capture and Storage - or Bio CCS - refers to the use of biological sequestration methods to reduce greenhouse gas emissions from stationary emitters, such as coal, gas and oil fired utilities, or to reduce net levels of greenhouse gases in the atmosphere. For example, Bio CCS Algal Synthesis test facilities are being trialed at Australia's three largest coal fired power stations (Tarong, Queensland; Eraring, NSW; Loy Yang, Victoria) using piped pre-emission smokestack CO2 (and other greenhouse gases) as feedstock to grow oil-rich algal biomass in enclosed membranes for the production of plastics, transport fuel and nutritious animal feed. The term "Bio" CCS has been created, in part, to draw government policy attention to the fact that biological sequestration offers a financially and technologically viable 'bridge' in the near term, from a world heavily dependent upon fossil fuels, to a lower carbon future. Due to its comparative ease to implement to a wide range of stationary emitters - including retro-fit - Bio CCS is hoped to achieve what geo sequestration (Geo CCS) has failed to: significant CO2 net emissions reduction in the near to medium term.

The term Carbon dioxide capture and storage has also been used to describe biological techniques such as biochar burial, which use trees, plankton, etc. to capture CO₂ from the air. However, it is more conventional to use the term carbon capture and storage to describe non-biological processes 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;^[1] integrated pilot-scale CCS power plant was to begin operating in September 2008 in the eastern German power plant Schwarze Pumpe run by utility Vattenfall, in the hope of answering questions about technological feasibility and economic efficiency.

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.^[2] 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.^[2])

Capturing and compressing CO₂ requires much energy and would increase the fuel needs of a coal-fired plant with CCS by 25%-40%.^[2] These and other system costs are estimated to increase the cost of energy from a new power plant with CCS by 21-91%.^[2] These estimates apply to purpose-built plants near a storage location: applying the technology to preexisting plants or plants far from a storage location will be more expensive. However, recent industry reports suggest that with successful research, development and deployment (RD&D), sequestered coal-based electricity generation in 2025 will cost less than unsequestered coal-based electricity generation today.^[3]

Storage of the CO₂ is envisaged either in deep geological formations, in deep ocean masses, or in the form of mineral carbonates. In the case of deep ocean storage, there is a risk of greatly increasing the problem of ocean acidification, a problem that also stems from the excess of carbon dioxide already in the atmosphere and oceans. Geological formations are currently considered the most promising sequestration sites. The National Energy Technology Laboratory (NETL) reported that North America has enough storage capacity at its current rate of production for more than 900 years worth of carbon dioxide.^[4] 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.

When applied on plants which use biomass, the process is known as bio-energy with carbon capture and storage. This has the potential to be used as a negative carbon emission technique, and is by some regarded as geoengineering.

Contents 1 Capture 1.1 Cement production 2 Transport 3 Sequestration 3.1 Geological storage 3.2 Ocean storage 3.3 Mineral storage 3.4 Leakage 4 CO2 re-use 4.1 Single step methods: methanol 4.2 Single step methods: hydrocarbons 4.3 Two step methods 5 Example CCS projects 5.1 Industrial-scale storage 5.2 Canada 5.3 Italy 5.4 Netherlands 5.5 Norway 5.6 Poland 5.7 United States 5.8 United Kingdom 5.9 China 5.10 Germany 5.11 Australia 6 Limitations of CCS for power stations 7 Cost 8 Environmental effects 8.1 Comparison with other power sources 9 See also 10 Notes 11 References 12 External links

Capture

Capturing CO₂ might be applied to large point sources, such as large fossil fuel or biomass energy facilities, industries with major CO₂ emissions, natural gas processing, synthetic fuel plants and fossil fuel-based hydrogen production plants. Air capture is also possible. But air away from the point source also contains oxygen, and so capturing air, scrubbing the CO₂ from the air, and then storing the CO₂ could slow down the oxygen cycle in the biosphere.

Concentrated CO₂ from the combustion of coal in oxygen is relatively pure, and could be directly processed. In other instances, especially with air capture, a scrubbing process would be needed.

Broadly, three different types of technologies exist: post-combustion, pre-combustion, and oxyfuel combustion.

• In post combustion capture, the CO₂ is removed after combustion of the fossil fuel - this is the scheme that would be applied to fossil-fuel burning power plants. Here, carbon dioxide is captured from flue gases at power stations or other large point sources. The technology is well understood and is currently used in other industrial applications, although not at the same scale as might be required in a commercial scale power station.

• The technology for pre-combustion is widely applied in fertilizer, chemical, gaseous fuel (H₂, CH₄), and power production.^[5] In these cases, the fossil fuel is partially oxidized, for instance in a gasifier. The resulting syngas (CO and H₂) is shifted into CO₂ and more H₂. The resulting CO₂ can be captured from a relatively pure exhaust stream. The H₂ can now be used as fuel; the carbon dioxide is removed before combustion takes place. There are several advantages and disadvantages when compared to conventional post combustion carbon dioxide capture.^[6][7]

• In oxy-fuel combustion^[8] the fuel is burned in oxygen instead of air. To limit the resulting flame temperatures to levels common during conventional combustion, cooled flue gas is recirculated and injected into the combustion chamber. The flue gas consists of mainly carbon dioxide and water vapor, the latter of which is condensed through cooling. The result is an almost pure carbon dioxide stream that can be transported to the sequestration site and stored. Power plant processes based on oxyfuel combustion are sometimes referred to as "zero emission" cycles, because the CO₂ stored is not a fraction removed from the flue gas stream (as in the cases of pre- and post-combustion capture) but the flue gas stream itself. It should be noted, however, that a certain fraction of the CO₂ generated during combustion will inevitably end up in the condensed water. To warrant the label "zero emission" the water would thus have to be treated or disposed of appropriately. The technique is promising, but the initial air separation step demands a lot of energy.

• Plants that produce ethanol by fermentation generate cool, essentially pure CO₂ that can be pumped underground.^[9] Fermentation produces slightly less CO₂ than ethanol by weight. World ethanol production in 2008 is expected to be about 16 billion gallons or 48 million tonnes.^[10]

An alternate method, which is under development, is chemical looping combustion (CLC). Chemical looping uses a metal oxide as a solid oxygen carrier. Metal oxide particles react with a solid, liquid or gaseous fuel in a fluidized bed combustor, producing solid metal particles and a mixture of carbon dioxide and water vapor. The water vapor is condensed, leaving pure carbon dioxide which can be sequestered. The solid metal particles are circulated to another fluidized bed where they react with air, producing heat and regenerating metal oxide particles that are recirculated to the fluidized bed combustor. A variant of chemical looping is calcium looping, which uses the alternate carbonation and then calcination of a CaO based carrier as a means of capturing CO₂.

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.^[11] 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.^[12] 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. Techniques of this type have received widespread media coverage as they offer the promise of a comprehensive solution to global warming if they can be coupled with effective carbon sequestration technologies.

It is more usual to see such techniques proposed for air capture, than for flue gas treatment. Carbon dioxide capture and storage is more commonly proposed on plants burning coal in oxygen extracted from the air, which means the CO₂ is highly concentrated and no scrubbing process is necessary.

According to the Wallula Energy Resource Center in Washington state, by gasifying coal, it is possible to capture approximately 65% of carbon dioxide embedded in it and sequester it in a solid form.^[13]

Cement production

Cement production captures CO₂ from industrial smokestacks to be stored in cement during production. Globally, five percent of CO₂ emissions is produced by manufacturing cement.

The process of turning carbon into cement involves sea water as a major resource. In this process, sea water is split via electrolysis to make aqueous solutions of sodium hydroxide and hydrochloric acid. The resulting acid is then neutralized in a reaction with silicate rocks, producing sand and magnesium chloride. These two products can be used together or separately to melt ice on roads. The alkaline sodium hydroxide solution is combined with carbon dioxide streams from industrial smokestacks, trapping the carbon dioxide in the form of sodium bicarbonate, which in turn can be added back to sea water rich in magnesium and calcium ions, triggerring a series of reactions that lead to precipitation of magnesium carbonate and calcium carbonate. These two by-products can be used in the manufacture of cement.

This process takes a considerable amount of funding, but some of the regulations made to greenhouse-gas emissions, such as carbon tax could eventually make this profitable as well as environment friendly.

Transport

After capture, the CO₂ would have to be transported to suitable storage sites. This is done by pipeline, which is generally the cheapest form of transport. In 2008, there were approximately 5,800 km of CO₂ pipelines in the United States, used to transport CO₂ to oil production fields where the CO₂ is injected in older fields to extract oil. The injection of CO₂ to produce oil is generally called "Enhanced Oil Recovery" or EOR. In addition, there are several pilot programs in various stages to test the long-term storage of CO₂ in non-oil producing geologic formations. These are discussed below.

COA conveyor belt system or ships could also be used. These methods are currently used for transporting CO₂ for other applications.

According to the Congressional Research Service, "There are important unanswered questions about pipeline network requirements, economic regulation, utility cost recovery, regulatory classification of CO₂ itself, and pipeline safety. Furthermore, because CO₂ pipelines for enhanced oil recovery are already in use today, policy decisions affecting CO₂ pipelines take on an urgency that is unrecognized by many. Federal classification of CO₂ as both a commodity (by the Bureau of Land Management) and as a pollutant (by the Environmental Protection Agency) could potentially create an immediate conflict which may need to be addressed not only for the sake of future CCS implementation, but also to ensure consistency of future CCS with CO₂ pipeline operations today.^[14][15]

Sequestration

Various forms have been conceived for permanent storage of CO₂. These forms include gaseous storage in various deep geological formations (including saline formations and exhausted gas fields), liquid storage in the ocean, and solid storage by reaction of CO₂ with metal oxides to produce stable carbonates.

Geological storage

Also known as geo-sequestration, this method involves injecting carbon dioxide, generally in supercritical form, directly into underground geological formations. Oil fields, gas fields, saline formations, unminable coal seams, and saline-filled basalt formations have been suggested as storage sites. Various physical (e.g., highly impermeable caprock) and geochemical trapping mechanisms would prevent the CO₂ from escaping to the surface.

CO₂ is sometimes injected into declining oil fields to increase oil recovery. Approximately 30 to 50 million metric tonnes of CO₂ are injected annually in the United States into declining oil fields.^[16] This option is attractive because the geology of hydrocarbon reservoirs is generally well understood and storage costs may be partly offset by the sale of additional oil that is recovered. Disadvantages of old oil fields are their geographic distribution and their limited capacity, as well as that the subsequent burning of the additional oil so recovered will offset much or all of the reduction in CO₂ emissions.

Unminable coal seams can be used to store CO₂ because CO₂ adsorbs to the surface of coal. However, the technical feasibility depends on the permeability of the coal bed. In the process of absorption the coal releases previously absorbed methane, and the methane can be recovered (enhanced coal bed methane recovery). The sale of the methane can be used to offset a portion of the cost of the CO₂ storage. However, burning the resultant methane would produce CO₂, which would negate some of the benefit of sequestering the original CO₂.

Saline formations contain highly mineralized brines, and have so far been considered of no benefit to humans. Saline aquifers have been used for storage of chemical waste in a few cases. The main advantage of saline aquifers is their large potential storage volume and their common occurrence. The major disadvantage of saline aquifers is that relatively little is known about them, compared to oil fields. To keep the cost of storage acceptable the geophysical exploration may be limited, resulting in larger uncertainty about the aquifer structure. Unlike storage in oil fields or coal beds no side product will offset the storage cost. Leakage of CO₂ back into the atmosphere may be a problem in saline aquifer storage. However, current research shows that several trapping mechanisms immobilize the CO₂ underground, reducing the risk of leakage.

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 of rock formations in the U.S. that could be used to store 500 years' worth of U.S. carbon dioxide emissions.^[17]

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,^[18][19] or growing more solid clathrate.^[20]

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.

The time it takes water in the deeper oceans to circulate to the surface has been estimated to be in the order of 1600 years, varying upon currents and other changing conditions. Costs for deep ocean disposal of liquid CO₂ are estimated at US$40−80/tonne CO₂ (2002 USD). This figure covers the cost of sequestration at the power plant and naval transport to the disposal site.^[2]

The bicarbonate approach would reduce the pH effects and enhance the retention of CO₂ in the ocean, but this would also increase the costs and other environmental effects.

An additional method of long term ocean based sequestration is to gather crop residue such as corn stalks or excess hay into large weighted bales of biomass and deposit it in the alluvial fan areas of the deep ocean basin. Dropping these residues in alluvial fans would cause the residues to be quickly buried in silt on the sea floor, sequestering the biomass for very long time spans. Alluvial fans exist in all of the world's oceans and seas where river deltas fall off the edge of the continental shelf such as the Mississippi alluvial fan in the Gulf of Mexico and the Nile alluvial fan in the Mediterranean Sea.

Unfortunately, biomass and crop residues form an extremely important and valuable component of topsoil and sustainable agriculture. Removing them from the terrestrial equation is fraught with problems and would exacerbate nutrient depletion and increase dependence on chemical fertilizers and, therefore, petrochemicals, thus defeating the original intentions - to reduce CO₂ in the atmosphere.

Mineral storage

Carbon sequestration by reacting naturally occurring Mg and Ca containing minerals with CO₂ to form carbonates has many unique advantages. Most notabl[e] is the fact that carbonates have a lower energy state than CO₂, which is why mineral carbonation is thermodynamically favorable and occurs naturally (e.g., the weathering of rock over geologic time periods). Secondly, the raw materials such as magnesium based minerals are abundant. Finally, the produced carbonates are unarguably stable and thus re-release of CO₂ into the atmosphere is not an issue. However, conventional carbonation pathways are slow under ambient temperatures and pressures. The significant challenge being addressed by this effort is to identify an industrially and environmentally viable carbonation route that will allow mineral sequestration to be implemented with acceptable economics.^[21]

In this process, CO₂ is exothermically reacted with abundantly available metal oxides which produces stable carbonates. This process occurs naturally over many years and is responsible for much of the surface limestone. The reaction rate can be made faster, for example by reacting at higher temperatures and/or pressures, or by pre-treatment of the minerals, although this method can require additional energy. The IPCC estimates that a power plant equipped with CCS using mineral storage will need 60-180% more energy than a power plant without CCS. (ch.7, p.   321, p.   330) ^[2]

The following table lists principal metal oxides of Earth's Crust. Theoretically up to 22% of this mineral mass is able to form carbonates.

Earthen Oxide	Percent of Crust	Carbonate	Enthalpy change (kJ/mol)
SiO2	59.71
Al2O3	15.41
CaO	4.90	CaCO3	-179
MgO	4.36	MgCO3	-117
Na2O	3.55	Na2CO3
FeO	3.52	FeCO3
K2O	2.80	K2CO3
Fe2O3	2.63	FeCO3
	21.76	All Carbonates

Leakage

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.^[22] 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.^[23] 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.

For ocean storage, the retention of CO₂ would depend on the depth; IPCC estimates 30–85% would be retained after 500 years for depths 1000–3000 m. Mineral storage is not regarded as having any risks of leakage. The IPCC recommends that limits be set to the amount of leakage that can take place. This might rule out deep ocean storage as an option.

It should also be noted that at the conditions of the deeper oceans, (about 400 bar or 40 MPa, 280 K) water–CO₂(l) mixing is very low (where carbonate formation/acidification is the rate limiting step), but the formation of water-CO₂ hydrates is favorable. (a kind of solid water cage that surrounds the CO₂). [3]

To further investigate the safety of CO₂ sequestration, we can look into Norway's Sleipner gas field, as it is the oldest plant that stores CO₂ on an industrial scale. According to an environmental assessment of the gas field which was conducted after ten years of operation, the author affirmed that geosequestration of CO₂ was the most definite form of permanent geological storage of CO₂. [4]

Available geological information shows absence of major tectonic events after the deposition of the Utsira formation [saline reservoir]. This implies that the geological environment is tectonically stable and a site suitable for carbon dioxide storage. The solubility trapping [is] the most permanent and secure form of geological storage. [4]

In March 2009, StatoilHydro issued a study showing the slow spread of CO₂ in the formation after more than 10 years operation.^[24]

Phase I of the Weyburn Project in Weyburn, Saskatchewan, Canada has determined that the likelihood of stored CO₂ release is less than one percent in 5,000 years.^[25]

Detailed geological histories of basins are required and should utilise the multi billion dollar petroleum seismic data sets to decrease the risk associated with fault stability. On injection of CO₂ into the earth there is a major pressure front that can break the seal and make faults unstable. The Gippsland Basin in Australia has a 3D-GEO seismic megavolume that consists of 30+ 3D seismic volumes that have been merged. Such datasets can image faults at a resolution of 15 metres over an area 100 km by 100 km. Mid 2010 the first full geological study of the Gippsland Basin will become openfile by 3D-GEO making CCS fault risk workflow available with the associated data that constrains it. In basins around the world such studies are not available and can only be bought at a price tag of greater than a million dollars.

CO₂ re-use

Recycling CO2 is likely to offer the most environmentally and financially sustainable response to the global challenge of significantly reducing greenhouse gas emissions from major stationary (industrial) emitters in the near to medium term. This is because newly developed technologies, such as Bio CCS Algal Synthesis value captured, pre-smokestack CO2 (such as from a coal fired power station, for example) as a useful feedstock input to the production of oil-rich algae in solar membranes to produce oil for plastics and transport fuel (including aviation fuel) and nutritious stockfeed for farm animal production. The CO2 and other captured greenhouse gases are injected into the membranes containing waste water and select strains of algae causing, together with sunlight or UV light, the oil rich biomass to double in mass every 24 hours. The Bio CCS Algal Synthesis process holds a number of key advantages over conventional CCS in that it is based on well established earth science photosynthesis; the technology is entirely retro-fittable and colocated with the emitter; the capital outlays offer a return upon investment due to the high value commodities produced (oil for plastics, fuel and feed)- whereas CCS (injecting liquified CO2 deep underground) represents substantial logistical difficulty, very high cost without any financial return, and extremely limited applicability to the bulk of existing major industrial emitters. Another advantage of Bio CCS Algal Synthesis is that it offers consumption of the full cocktail of greenhouse gases normally found in smokestack emissions - not just CO2 as is the case with most CCS proposals.

Another potentially useful way of dealing with industrial sources of CO₂ is to convert it into hydrocarbons where it can be stored or reused as fuel or to make plastics. There are a number of projects investigating this possibility.^[26]

Carbon dioxide scrubbing variants exist based on potassium carbonate^[27] which can be used to create liquid fuels. Although the creation of fuel from atmospheric CO₂ is not a geoengineering technique, nor does it actually function as greenhouse gas remediation, it nevertheless is potentially very useful in the creation of a low carbon economy, as transport fuels, especially aviation fuel, are currently hard to make other than by using fossil fuels. Whilst electric car technology is widely available, and can be used with renewable energy for carbon neutral driving, there are no electric jet airliners available, nor are there likely to be in the foreseeable future.

Single step methods: methanol

A proven process to produce a hydrocarbon is to make methanol. Methanol is rather easily synthesized from CO₂ and H₂ (See Green Methanol Synthesis). Based on this fact the idea of a methanol economy was born.

Single step methods: hydrocarbons

At the department of Industrial Chemistry and Engineering of Materials at the University of Messina, Italy there is a project to develop a system which works like a fuel-cell in reverse, whereby a catalyst is used that enables sunlight to split water into hydrogen ions and oxygen gas. The ions cross a membrane where they react with the CO₂ to create hydrocarbons.^[28]

Two step methods

If CO₂ is heated to 2400°C, it splits into carbon monoxide and oxygen. The Fischer-Tropsch process can then be used to convert the CO into hydrocarbons. The required temperature can be achieved by using a chamber containing a mirror to focus sunlight on the gas. There are a couple of rival teams developing such chambers, at Solarec and at Sandia National Laboratories, both based in New Mexico. According to Sandia these chambers could provide enough fuel to power 100% of domestic vehicles using 5800 km², but unlike biofuels this would not take fertile land away from crops but would be land that is not being used for anything else. James May, the British TV presenter, visited a demonstration plant in a programme in his 'Big Ideas' series.

Example CCS projects

Industrial-scale storage

As of 2007, four industrial-scale storage projects are in operation. Sleipner is the oldest project, having started in 1996, and is located in the North Sea where Norway's Statoil strips carbon dioxide from natural gas with amine solvents and disposes of this CO₂ in a deep saline aquifer.^[29] The carbon dioxide is a waste product of the field's natural gas production and the gas contains more (9% CO₂) than is allowed into the natural gas distribution network. Storing it underground avoids this problem and saves Statoil hundreds of millions of euro in avoided carbon taxes. Since 1996, Sleipner has stored about one million tonnes CO₂ a year. A second project in the Snøhvit gas field in the Barents Sea stores 700,000 tonnes per year.^[30]

The Weyburn-Midale CO₂ Project is currently the world's largest carbon capture and storage project.^[30] Started in 2000, Weyburn-Midale is located on an oil reservoir discovered in 1954 in southeastern Saskatchewan, Canada. The CO₂ for this project is captured at Dakota Gasification Company's Great Plains Synfuels Plant in Beulah, North Dakota,^[31][32] which has produced methane from coal for more than 30 years. A subsidiary of Basin Electric Power Cooperative, Dakota Gasification Company captures roughly 50 percent of the CO₂ produced by the Synfuels Plant.^[31] At Weyburn, the CO₂ is used for enhanced oil recovery with an injection rate of about 1.5 million tonnes per year. The first phase finished in 2004, and demonstrated that CO₂ can be stored underground at the site safely and indefinitely. The second phase, expected to last until 2009, is investigating how the technology can be expanded on a larger scale.^[33]

The fourth site is In Salah, which like Sleipner and Snøhvit is a natural gas reservoir located in In Salah, Algeria. The CO₂ will be separated from the natural gas and re-injected into the subsurface at a rate of about 1.2 million tonnes per year.^[34]

Canada

In July 2008, the Government of Alberta announced a $2 billion investment in four large-scale carbon capture and storage projects.^[35] In 2009, letters of intent were signed with four project proponents and grant agreement negotiations are ongoing. It is expected the grant agreements will be signed in early 2010. The projects selected include a 240 kilometre pipeline; an in-situ coal gasification (ISCG) project; an oil sands upgrader and expansion; and an electricity plant.^{[36][37][38][39]}

A major Canadian initiative called the Alberta Saline Aquifer Project (ASAP) is a consortium of 38 industry participants that are developing a pilot site for commercial scale carbon capture and storage in a saline aquifer. The initial pilot will sequester 1,000 tonnes per day in 2010, while the commercial phase could see 10,000 tonnes per day as soon as 2015.^[40]

Another Canadian initiative called the Integrated CO₂ Network (ICO₂N)] is a proposed system for the capture, transport and storage of carbon dioxide (CO₂). ICO₂N members represent a group of industry participants providing a framework for carbon capture and storage development in Canada.^[41]

Italy

Porto Tolle, Italy, ^[42] a coal-fired energy plant of more than 2.500 MW, planned to be set up in Porto Tolle next year, with a CCS unit for abating CO2 emissions coming from a 300 MW power production line.

Netherlands

In the Netherlands, a 68 MW oxyfuel plant ("Zero Emission Power Plant") was being planned to be operational in 2009.^[43] However, this project was later cancelled.

Norway

In Norway, the CO2 Technology Centre (TCM) at Mongstad started construction in 2009, and is scheduled for completion early 2012. It will include two capture technology plants (one advanced amine and one chilled ammonia), both capturing fluegas from two sources, a gas fired power plant, and refinery cracker fluegas (similar to coal fired power plant fluegas). Total capacity is 100 000 tons of CO2 per year. ^[44]

Poland

Belchatów, Poland, ^[45] a lignite-fired energy plant of more than 858 MW, planned to be in operation in 2013.

United States

In October 2007, the Bureau of Economic Geology at The University of Texas at Austin received a 10-year, $38 million subcontract to conduct the first intensively monitored, long-term project in the United States studying the feasibility of injecting a large volume of CO₂ for underground storage.^[46] The project is a research program of the Southeast Regional Carbon Sequestration Partnership (SECARB), funded by the National Energy Technology Laboratory of the U.S. Department of Energy (DOE). The SECARB partnership will demonstrate CO₂ injection rate and storage capacity in the Tuscaloosa-Woodbine geologic system that stretches from Texas to Florida. The region has the potential to store more than 200 billion tons of CO₂ from major point sources in the region, equal to about 33 years of U.S. emissions overall at present rates. Beginning in fall 2007, the project will inject CO₂ at the rate of one million tons per year, for up to 1.5 years, into brine up to 10,000 feet (3,000 m) below the land surface near the Cranfield oil field about 15 miles (25 km) east of Natchez, Mississippi. Experimental equipment will measure the ability of the subsurface to accept and retain CO₂.

Currently, the United States government has approved the construction of what is touted as the world's first CCS power plant, FutureGen. On January 29, 2008, however, the Department of Energy announced it was recasting the FutureGen project and on June 24, 2008, DoE published a funding opportunity announcement seeking proposals for an IGCC project, with integrated CCS, of at least 250MW.^[47]

Examples of carbon sequestration at an existing US coal plant can be found at utility company Luminant's pilot version at its Big Brown Steam Electric Station in Fairfield, Texas. This system is converting carbon from smokestacks into baking soda. Skyonic plans to circumvent storage problems of liquid CO₂ by storing baking soda in mines, landfills, or simply to be sold as industrial or food grade baking soda.^[48] Green Fuel Technologies is piloting and implementing algae based carbon capture, circumventing storage issues by then converting algae into fuel or feed.^[49]

In November 2008, the DOE awarded a $66.9 million, eight-year grant to a research partnership headed by Montana State University to demonstrate that underground geologic formations “can store huge volumes of carbon dioxide economically, safely and permanently.” Researchers under the Big Sky Regional Carbon Sequestration Project plan to inject up to one million tons of CO₂ into sandstone beneath southwestern Wyoming.^[50]

In the United States, four different synthetic fuel projects are moving forward which have publicly announced plans to incorporate carbon capture and storage.

American Clean Coal Fuels, in their Illinois Clean Fuels project, is developing a 30,000 barrel per day biomass and coal to liquids project in Oakland, Illinois, which will market the CO₂ created at the plant for enhanced oil recovery applications. The project is expected to come online in mid-2013. By combining sequestration and biomass feedstocks, the ICF project will achieve dramatic reductions in the lifecycle carbon footprint of the fuels they produce. If sufficient biomass is used, the plant should have the capability to go life cycle carbon negative (meaning that effectively, for each gallon of their fuel that is used, carbon is pulled out of the air, and put into the ground.)^[51]

Baard Energy, in their Ohio River Clean Fuels project, are developing a 53,000 BPD coal and biomass to liquids project, which has announced plans to market the plant’s CO₂ for enhanced oil recovery.^[52]

Rentech is developing a 29,600 barrel per day coal and biomass to liquids plant in Natchez, Mississippi which will market the plant’s CO₂ for enhanced oil recovery. The first phase of the project is expected in 2011.^[53]

DKRW is developing a 15,000-20,000 Barrel Per Day coal to liquids plant in Medicine Bow Wyoming, which will market it plant’s CO₂ for enhanced oil recovery. The project is expected to begin operation in 2013.^[54]

In October 2009, the U.S. Department of Energy awarded twelve Industrial Carbon Capture and Storage (ICCS) projects to conduct a Phase 1 feasibility study.^[55] The DOE plans to select 3 to 4 of those projects to proceed into Phase 2 design and construction with operational startup to occur by 2015. Battelle Memorial Institute, Pacific Northwest Division, Boise, Inc., and Fluor Corporation are studying a CCS system for capture and storage of CO₂ emissions associated with the pulp and paper production industry. The site of the study is the Boise White Paper L.L.C. paper mill located near the township of Wallula in Southeastern Washington State. The plant generates approximately 1.2 MMT of CO₂ annually from a set of three recovery boilers that are mainly fired with black liquor, a recycled byproduct formed during the pulping of wood for papermaking. Fluor Corporation will design a customized version of their Econamine Plus™ carbon capture technology. The Fluor system also will be designed to remove residual quantities of remnant air pollutants from stack gases as part of the CO₂ capture process. Battelle is leading preparation of an Environmental Information Volume (EIV) for the entire project including geologic storage of the captured CO₂ in deep flood basalt formations that exist in the greater region. The EIV will describe the necessary site characterization work, sequestration system infrastructure, and monitoring program to support permanent sequestration of the CO₂ captured at the plant.

In addition to individual carbon capture and sequestration projects, there are a number of U.S. programs designed to research, develop and deploy CCS technologies on a broad scale. These include the National Energy Technology Laboratory’s (NETL) Carbon Sequestration Program, regional carbon sequestration partnerships and the Carbon Sequestration Leadership Forum (CSLF).^[56][57]

United Kingdom

The United Kingdom Government has launched a tender process for a CCS demonstration project. The project will use post-combustion technology on coal fired power generation at 300-400 MW or equivalent. The project aims to be operational by 2014.^[58][59] The Government announced in June 2008 that four companies had prequalified for the following stages of the competition, BP Alternative Energy International Limited, EON UK Plc, Peel Power Limited and Scottish Power Generation Limited.^[60] BP have subsequently withdrawn from the competition claiming it could not find a power generator partner and RWE npower is seeking a judicial review of the process after it did not qualify.^[61]

Doosan Babcock will modify a Test Rig at Renfrew in Scotland to accommodate Oxyfuel firing on pulverised coal with recycled flue gas and demonstrate the operation of a full scale 40 MW burner for use in coal-fired boilers. Sponsors of the project include the UK Department for Business Enterprise and Regulatory Reform (BERR) and a group of industrial sponsors and university partners comprising Scottish and Southern Energy (Prime Sponsor), E.ON UK PLC, Drax Power Limited, ScottishPower, EDF Energy, Dong Energy Generation, Air Products Plc (Sponsors), and Imperial College and University of Nottingham (University Partners).^[62]

China

In Beijing, as of 2009, one major power plant is capturing and re-selling a small fraction of its CO₂ emissions. ^[63]

Germany

The German industrial area of Schwarze Pumpe, about 4 km south of the city of Spremberg, is home to the world's first CCS coal plant. The mini pilot plant is run by an Alstom-built oxy-fuel boiler and is also equipped with a flue gas cleaning facility to remove fly ash and sulphur dioxide. The Swedish company Vattenfall AB invested some 70 million Euros in the two year project which began operation September 9, 2008. The power plant, which is rated at 30-megawatts, is a pilot project to serve as a prototype for future full-scale power plants.^[64][65] 240 tonnes a day of CO₂ are being trucked 350 kilometers (210 miles) where it will be injected into an empty gas field. Germany's BUND group called it a "fig leaf". For each tonne of coal burned, 3.6 tonnes of carbon dioxide is produced.^[66]

German utility RWE operates a pilot-scale CO₂ scrubber at the lignite-fired Niederaußem power station built in cooperation with BASF (supplier of detergent) and Linde (engineering).^[67]

Jänschwalde, Germany,^[68]a new Oxyfuel boiler build at Jänschwalde would be of 650 MW thermal (around 250 MW electric), which is about 20 times more than Vattenfall's 30 MW pilot plant under construction and compares to today’s largest Oxyfuel test rigs of 0.5 MW. With this milestone, Vattenfall is taking another step towards development of commercial CCS concepts. Also Postcombustion capture technology will be demonstrated at Jänschwalde.

Australia

The Federal Resources and Energy Minister Martin Ferguson opened the first geosequestration project in the southern hemisphere in April 2008. The demonstration plant is near Nirranda South in South Western Victoria. () The plant is owned by the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC). CO2CRC is a non profit research collaboration supported by government and industry. The project has stored and monitored over 65,000 tonnes of carbon dioxide-rich gas which was extracted from a natural gas reservoir via a well, compressed and piped 2.25 km to a new well. There the gas has been injected into a depleted natural gas reservoir approximately two kilometers below the surface.^[69][70] The project has moved to a second stage and is investigating carbon dioxide trapping in a saline aquifer 1500 meters below the surface. The Otway Project is a research and demonstration project, focused on comprehensive monitoring and verification.^[71]

This plant does not propose to capture CO₂ from coal fired power generation, though two CO2CRC demonstration projects at a Victorian power station and research gasifier are demonstrating solvent, membrane and adsorbent capture technologies from coal combustion.^[72] Currently only small-scale projects are storing CO₂ stripped from the products of combustion of coal burnt for electricity generation at coal fired power stations .^[73] although work currently being carried out by the New South Wales government and private industry intends to have a working pilot plant in operation by 2013.

Limitations of CCS for power stations

One limitation of CCS is its energy penalty. The technology is expected to use between 10 and 40% of the energy produced by a power station.^[74] Wide scale adoption of CCS may erase efficiency gains of the last 50 years, and increase resource consumption by one third. However even taking the fuel penalty into account overall levels of CO₂ abatement remain high, at approximately 80-90% compared to a plant without CCS.^[75] It is theoretically possible for CCS, when combined with combustion of biomass, to result in net negative emissions, but this is not currently feasible given the lack of development of CCS technologies and the limitations of biomass production.^[76]

A second concern regards the permanence of storage schemes. It is claimed that safe and permanent storage of CO₂ cannot be guaranteed and that even very low leakage rates could undermine any climate mitigation effect.^[74] However, the IPCC conclude that the proportion of CO₂ retained in appropriately selected and managed geological reservoirs is very likely to exceed 99% over 100 years and is likely to exceed 99% over 1,000 years.^[2]

Finally there is the issue of cost. Greenpeace claim that CCS could lead to a doubling of plant costs.^[74] However CCS may still be economically attractive in comparison to other forms of low carbon electricity generation.^[77] It is also claimed by opponents to CCS that money spent on CCS will divert investments away from other solutions to climate change.

Cost

Although the processes involved in CCS have been demonstrated in other industrial applications, no commercial scale projects which integrate these processes exist, the costs therefore are somewhat uncertain. However, some recent credible estimates indicate that a carbon price of US$60 per US-ton is required to make capture and storage competitive,^[78] corresponding to an increase in electricity prices of about US 6c per kWh (based on typical coal fired power plant emissions of 2.13 pounds CO₂ per kWh). This would double the typical US industrial electricity price (now at around 6c per kWh) and increase the typical retail residential electricity price by about 50% (assuming 100% of power is from coal, which may not necessarily be the case, as this varies from state to state). However similar (approximate) price increases would likely be expected in coal dependent countries such as Australia, because the capture technology and chemistry, transport and injection costs from such power plants would not, in an overall sense, vary significantly from country to country.

The reasons that CCS is expected to cause such power price increases are several. Firstly, the increased energy requirements of capturing and compressing CO₂ significantly raise the operating costs of CCS-equipped power plants. In addition there is added investment or capital costs. The process would increase the fuel requirement of a plant with CCS by about 25% for a coal-fired plant and about 15% for a gas-fired plant.^[2] The cost of this extra fuel, as well as storage and other system costs are estimated to increase the costs of energy from a power plant with CCS by 30-60%, depending on the specific circumstances. Pre-commercial CCS demonstration projects are likely to be more expensive than mature CCS technology, the total additional costs of an early large scale CCS demonstration project are estimated to be €0.5-1.1bn per project over the project lifetime.^[79]

An estimate of costs of energy with and without CCS (2002 US$ per kWh)^[2]

	Natural gas combined cycle	Pulverized coal	Integrated gasification combined cycle
Without capture (reference plant)	0.03 - 0.05	0.04 - 0.05	0.04 - 0.06
With capture and geological storage	0.04 - 0.08	0.06 - 0.10	0.06 - 0.09
(Cost of capture and geological storage)	0.01 - 0.03	0.02 - 0.05	0.02 - 0.03
With capture and Enhanced oil recovery	0.04 - 0.07	0.05 - 0.08	0.04 - 0.08
All costs refer to costs for energy from newly built, large-scale plants. Natural gas combined cycle costs are based on natural gas prices of US$2.80–4.40 per GJ (LHV based). Energy costs for PC and IGCC are based on bituminous coal costs of US$1.00–1.50 per GJ LHV. Note that the costs are very dependent on fuel prices (which change continuously), in addition to other factors such as capital costs. Also note that for EOR, the savings are greater for higher oil prices. Current gas and oil prices are substantially higher than the figures used here. All figures in the table are from Table 8.3a in [IPCC, 2005].[2]

The cost of CCS depends on the cost of capture and storage which vary according to the method used. Geological storage in saline formations or depleted oil or gas fields typically cost US$0.50–8.00 per tonne of CO₂ injected, plus an additional US$0.10–0.30 for monitoring costs. However, when storage is combined with enhanced oil recovery to extract extra oil from an oil field, the storage could yield net benefits of US$10–16 per tonne of CO₂ injected (based on 2003 oil prices). This would likely negate some of the effect of the carbon capture when the oil was burnt as fuel. However, as the table above shows, the benefits do not outweigh the extra costs of capture.

Comparisons of CCS with other energy sources can be found in wind energy, solar energy, and Economics of new nuclear power plants.

Environmental effects

The theoretical merit of CCS systems is the reduction of CO₂ emissions by up to 90%, depending on plant type. Generally, environmental effects from use of CCS arise during power production, CO₂ capture, transport and storage. Issues relating to storage are discussed in those sections.

Additional energy is required for CO₂ capture, and this means that substantially more fuel has to be used, depending on the plant type. For new supercritical pulverized coal (PC) plants using current technology, the extra energy requirements range from 24-40%, while for natural gas combined cycle (NGCC) plants the range is 11-22% and for coal-based gasification combined cycle (IGCC) systems it is 14-25% [IPCC, 2005]. Obviously, fuel use and environmental problems arising from mining and extraction of coal or gas increase accordingly. Plants equipped with flue gas desulfurization (FGD) systems for SO₂ control require proportionally greater amounts of limestone and systems equipped with SCR systems for NO_X require proportionally greater amounts of ammonia.

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.

Emissions to air from plants with CCS (kg/(MW•h))

	Natural gas combined cycle	Pulverized coal	Integrated gasification combined cycle
CO2	43 (-89%)	107 (−87%)	97 (−88%)
NOX	0.11 (+22%)	0.77 (+31%)	0.1 (+11%)
SOX	-	0.001 (−99.7%)	0.33 (+17.9%)
Ammonia	0.002 (before: 0)	0.23 (+2200%)	-
Based on Table 3.5 in [IPCC, 2005]. Between brackets the increase or decrease compared to a similar plant without CCS.

Comparison with other power sources

See also

• Biosequestration
• Carbon capture and storage (timeline)
• Carbon cycle re-balancing
• Carbon sink
• Limnic eruption
• Low-carbon economy
• Relative cost of electricity generated by different sources
• IEA Greenhouse Gas R&D Programme

Notes

References

External links

• World’s first network of demonstration projects, all of which are aiming to be operational by 2015 and commercially viable CCS by 2020.
• Canada's CO2 Capture and Storage Informtion Source This site has been designed with the public in mind, and we want your feedback. Please take some time to learn more about CCS by navigating through the ‘CCS Basics’ area of the site
• CO₂ Capture Project Global partnership of seven major energy companies working on next-generation CCS technology
• In Salah Gas CO₂ Storage Project Joint venture which has overseen capture and storage of one million tonnes per year of CO₂ from its natural gas refinery
• Zero Emissions Platform European Technology Platform for Zero Emission Fossil Fuel Power Plants
• UCL Carbon Capture Legal Programme Free online source of CCS Legal and Policy information.
• Intergovernmental Panel on Climate Change IPCC Special Report on Carbon Dioxide Capture and Storage (CCS).

• Scientific Facts on CO₂ Capture and Storage, a peer-reviewed summary of the IPCC Special Report on CCS.

• Carbon Sequestration News Recent news articles on CO₂ capture and storage.
• CO2NET - Carbon Dioxide Knowledge Sharing Network Extensive news and reports on CO₂ capture and storage events, projects and activities.
• Allianz Knowledge Site Short movie about Schwarze Pumpe, the world's first ccs pilot coal power plant.
• Stanford University Collection of recent news articles on CO₂ capture and storage.
• Paving the Legal Path for Carbon Sequestration from Coal 2009 journal article on CCS legal questions.
• DOE Fossil Energy Department of Energy programs in carbon dioxide capture and storage.
• 2007 NETL Carbon Sequestration Atlas
• Online discussion on pipeline materials for supercritical saturated CO₂
• Carbon Sequestration News, Events, Research and People Carbon Capture and Storage Information Hub
• The Global Carbon Capture and Storage Institute The Global Carbon Capture and Storage Institute (Global CCS Institute)
• "Burying Climate Change: Efforts Begin to Sequester Carbon Dioxide from Power Plants", West Virginia hosts the world's first power plant to inject some of its CO2 emissions underground for permanent storage, Scientific American, September 22, 2009.

Breakthrough guideline to boost Carbon Capture and Storage

• "What does it take to demonstrate CCS?" by Bjørn-Erik Haugan
• Mitigate your Carbon emissions by planting trees Green EU Initiative
• A Guide To Carbon Capture And Storage: Can carbon capture and storage save the climate from the consequences of fossil fuel burning?
• Powerplantccs Power Plant Carbon Capture, Storage, CO2 Sequestration
• Algae based CCS, CO2 Capture with Algae