Carbon capture and storage (
CCS) is a means of
mitigatingMitigation of global warming involves taking actions to reduce greenhouse gas emissions and to enhance sinks aimed at reducing the extent of global warming. This is in distinction to adaptation to global warming which involves taking action to minimize the effects of global warming. Mitigation is...
the contribution of
fossil fuelFossil fuels or mineral fuels are fuels formed by natural resources such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...
emissions to
global warmingGlobal warming is the increase in the average temperature of the Earth's near-surface air and oceans since the mid-20th century and its projected continuation. Global surface temperature increased 0.74 ± 0.18 °C during the last century...
, based on capturing
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
(CO
2) from large point sources such as
fossil fuel power plantA fossil-fuel power plant is a power plant that burns fossil fuels such as coal, natural gas or petroleum to produce electricity.Fossil-fuel power plants are designed on a large scale for continuous operation...
s, and store it away from atmosphere by different means. It can also be used to describe the
scrubbingA carbon dioxide scrubber is a device which absorbs carbon dioxide. It is used to treat exhaust gases from industrial plants or from exhaled air in life support systems such as rebreathers or in spacecraft, submersible craft or airtight chambers....
of CO
2 from ambient air as a
geoengineeringThe modern concept of geoengineering is usually taken to mean proposals to deliberately manipulate the Earth's climate to counteract the effects of global warming from greenhouse gas emissions...
technique.
The term
carbon dioxide capture and storage has also been used to describe biological techniques such as
biocharBiochar is charcoal created by pyrolysis of biomass. The resulting charcoal-like material is a form of biosequestration or atmospheric carbon capture and storage. Charcoal is a stable solid and rich in carbon content, and thus, can be used to lock carbon in the soil...
burial, which use trees, plankton, etc. to capture CO
2 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 CO
2 has been injected into geological formations for various purposes, the long term storage of CO
2 is a relatively new concept. The first commercial example is Weyburn in 2000; integrated pilot-scale CCS power plant was to begin operating in September 2008 in the eastern
GermanGermany , officially the Federal Republic of Germany , is a country in Central Europe. It is bordered to the north by the North Sea, Denmark, and the Baltic Sea; to the east by Poland and the Czech Republic; to the south by Austria and Switzerland; and to the west by France, Luxembourg, Belgium,...
power plant Schwarze Pumpe run by utility
VattenfallVattenfall is a Swedish power company and one of the leading energy producers in Northern Europe. The name Vattenfall is Swedish for waterfall, and is an abbreviation of its original name, Royal Waterfall Board...
, in the hope of answering questions about technological feasibility and economic efficiency.
CCS applied to a modern conventional power plant could reduce CO
2 emissions to the atmosphere by approximately 80-90% compared to a plant without CCS. The
IPCCThe Intergovernmental Panel on Climate Change is a scientific intergovernmental body tasked to evaluate the risk of climate change caused by human activity. The panel was established in 1988 by the World Meteorological Organization and the United Nations Environment Programme , two organizations...
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.)
Capturing and compressing CO
2 requires much energy and would increase the fuel needs of a coal-fired plant with CCS by 25%-40%. These and other system costs are estimated to increase the cost of energy from a new power plant with CCS by 21-91%. 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.
Storage of the CO
2 is envisaged either in deep geological formations, in deep ocean masses, or in the form of
mineralA mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific...
carbonateIn chemistry, a carbonate is a salt or ester of carbonic acid, characterized by the presence of the carbonate ion, or a carbonate functional group O=C2....
s. In the case of deep ocean storage, there is a risk of greatly increasing the problem of
ocean acidificationOcean acidification is the name given to the ongoing decrease in the pH of the Earth's oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere...
, 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. In its
2007 Carbon Sequestration Atlas, the
National Energy Technology LaboratoryThe National Energy Technology Laboratory is a science, technology, and energy laboratory owned and operated by the U.S. Department of Energy . As part of DOE's national laboratory system, NETL supports DOE's mission to advance the national, economic, and energy security of the United States...
(NETL) reported that North America has enough storage capacity at its current rate of production for more than 900 years worth of carbon dioxide. A general problem is that long term predictions about submarine or underground storage security are very difficult and uncertain and CO
2 might leak from the storage into the atmosphere.
When applied on plants which use
biomassBiomass, a renewable energy source, is biological material derived from living, or recently living organisms, such as wood, waste, and alcohol fuels. Biomass is commonly plant matter grown to generate electricity or produce heat. For example, forest residues , yard clippings and wood chips may be...
, the process is known as
bio-energy with carbon capture and storageBio-energy with carbon capture and storage is a greenhouse gas mitigation technology which produces negative carbon emissions by combining biomass use with carbon capture and storage....
. This has the potential to be used as a negative carbon emission technique, and is by some regarded as
geoengineeringThe modern concept of geoengineering is usually taken to mean proposals to deliberately manipulate the Earth's climate to counteract the effects of global warming from greenhouse gas emissions...
.
CO2 capture
Capturing CO
2 might be applied to large point sources, such as large fossil fuel or biomass energy facilities, industries with major CO
2 emissions,
natural gas processingNatural gas processing plants, or fractionators, are used to purify the raw natural gas extracted from underground gas fields and brought up to the surface by gas wells...
, synthetic fuel plants and fossil fuel-based hydrogen production plants. Air capture is also possible. But air away from the point source also contains
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
, and so capturing air, scrubbing the CO
2 from the air, and then storing the CO
2 could slow down the
oxygen cycleThe oxygen cycle is the biogeochemical cycle that describes the movement of oxygen within and between its three main reservoirs: the atmosphere , the biosphere , and the lithosphere...
in the
biosphereThe biosphere is the global sum of all ecosystems. It can also be called the zone of life on Earth. From the broadest biophysiological point of view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements...
.
Concentrated CO
2 from the combustion of
coalCoal is a readily combustible black or brownish-black sedimentary rock normally occurring in rock strata in layers or veins called coal beds. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
in
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
is relatively pure, and could be directly processed. In other instances, especially with air capture, a
scrubbingA carbon dioxide scrubber is a device which absorbs carbon dioxide. It is used to treat exhaust gases from industrial plants or from exhaled air in life support systems such as rebreathers or in spacecraft, submersible craft or airtight chambers....
process would be needed.
Broadly, three different types of technologies exist: post-combustion, pre-combustion, and oxyfuel combustion.
- In post combustion capture
Post combustion capture refers to the removal of CO2 from power station flue gas prior to its compression, transportation and storage in suitable geological formations, as part of carbon capture and storage. A number of different techniques are applicable, almost all of which are...
, the CO2 is removed after combustion of the fossil fuel - this is the scheme that would be applied to conventional power plants. Here, carbon dioxide is captured from flue gasFlue gas is gas that exits to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, it refers to the combustion exhaust gas produced at power plants...
es at power stationA fossil-fuel power plant is a power plant that burns fossil fuels such as coal, natural gas or petroleum to produce electricity.Fossil-fuel power plants are designed on a large scale for continuous operation...
s 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. In these cases, the fossil fuel is partially oxidized, for instance in a gasifier
Gasification is a process that converts carbonaceous materials, such as coal, petroleum, biofuel, or biomass, into carbon monoxide and hydrogen by reacting the raw material, such as house waste, or compost at high temperatures with a controlled amount of oxygen and/or steam. The resulting gas...
. The resulting syngasSyngas is the name given to a gas mixture that contains varying amounts of carbon monoxide and hydrogen. Examples of production methods include steam reforming of natural gas or liquid hydrocarbons to produce hydrogen, the gasification of coal, biomass, and in some types of waste-to-energy...
(CO and H2) is shiftedThe water-gas shift reaction is a chemical reaction in which carbon monoxide reacts with water to form carbon dioxide and hydrogen:The water-gas shift reaction is an important industrial reaction...
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.
- In oxy-fuel combustion 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 vapour, 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
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug, best known as the type of alcohol found in alcoholic beverages and in modern thermometers. Ethanol is one of the oldest recreational drugs...
by fermentationEthanol fermentation is a biological process in which sugars such as glucose, fructose, and sucrose are converted into cellular energy and thereby produce ethanol and carbon dioxide as metabolic waste products....
generate cool, essentially pure CO2 that can be pumped underground.http://www.energycurrent.com/index.php?id=2&storyid=7910 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.http://www.marketresearchanalyst.com/2008/01/26/world-ethanol-production-forecast-2008-2012/
An alternate method, which is under development, is
chemical looping combustionChemical looping combustion typically employs a dual fluidized bed system where a metal oxide is employed as a bed material providing the oxygen for combustion in the fuel reactor...
(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 bedFluidization is a process similar to liquefaction whereby a granular material is converted from a static solid-like state to a dynamic fluid-like state...
combustor, producing solid metal particles and a mixture of carbon dioxide and water vapour. The water vapour 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 CO
2.
A few engineering proposals have been made for the more difficult task of capturing CO
2 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 CO
2 from the
atmosphereAn atmosphere is a layer of gases that may surround a material body of sufficient mass, by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low...
is a form of
geoengineeringThe modern concept of geoengineering is usually taken to mean proposals to deliberately manipulate the Earth's climate to counteract the effects of global warming from greenhouse gas emissions...
by
greenhouse gas remediationGreenhouse gas remediation projects are a type of geoengineering and seek to remove greenhouse gases from the atmosphere, and thus tackle the root cause of climate change. These techniques either directly remove greenhouse gases, or alternatively seek to influence natural processes to remove...
. Techniques of this type have received widespread media coverage as they offer the promise of a comprehensive solution to
global warmingGlobal warming is the increase in the average temperature of the Earth's near-surface air and oceans since the mid-20th century and its projected continuation. Global surface temperature increased 0.74 ± 0.18 °C during the last century...
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
coalCoal is a readily combustible black or brownish-black sedimentary rock normally occurring in rock strata in layers or veins called coal beds. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
in
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
extracted from the air, which means the CO
2 is highly concentrated and no
scrubbingA carbon dioxide scrubber is a device which absorbs carbon dioxide. It is used to treat exhaust gases from industrial plants or from exhaled air in life support systems such as rebreathers or in spacecraft, submersible craft or airtight chambers....
process is necessary.
According to the
Wallula Energy Resource Center in Washington state, by gasifying the coal, it is possible to capture approximately 65% of carbon dioxide embedded in coal and sequester them into the solid form.
CO2 transport
After capture, the CO
2 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 CO
2 pipelines in the United States, used to transport CO
2 to oil production fields where the CO
2 is injected in older fields to extract oil. The injection of CO
2 to produce oil is generally called "
Enhanced Oil RecoveryEnhanced Oil Recovery is a generic term for techniques for increasing the amount of crude oil that can be extracted from an oil field...
" or EOR. In addition, there are several pilot programs in various stages to test the long-term storage of CO
2 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 CO
2 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 CO
2 itself, and pipeline safety. Furthermore, because CO
2 pipelines for
enhanced oil recoveryEnhanced Oil Recovery is a generic term for techniques for increasing the amount of crude oil that can be extracted from an oil field...
are already in use today, policy decisions affecting CO
2 pipelines take on an urgency that is unrecognized by many. Federal classification of CO
2 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 CO
2 pipeline operations today.
CO2 storage (sequestration)
Various forms have been conceived for permanent storage of CO
2. 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 CO
2 with metal
oxideAn oxide is a chemical compound containing at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon...
s to produce stable
carbonateIn chemistry, a carbonate is a salt or ester of carbonic acid, characterized by the presence of the carbonate ion, or a carbonate functional group O=C2....
s.
Geological storage
Also known as
geo-sequestration, this method involves injecting carbon dioxide, generally in
supercriticalA supercritical fluid is any substance at a temperature and pressure above its critical point. It can diffuse through solids like a gas, and dissolve materials like a liquid. In addition, close to the critical point, small changes in pressure or temperature result in large changes in density,...
form, directly into underground geological formations.
Oil fieldAn oil field is a region with an abundance of oil wells extracting petroleum from below ground. Because the oil reservoirs typically extend over a large area, possibly several hundred kilometres across, full exploitation entails multiple wells scattered across the area...
s, gas fields, saline formations, unminable coal seams, and saline-filled basalt formations have been suggested as storage sites. Various physical (e.g., highly impermeable
caprockThe Caprock is a region in the Panhandle of Texas . It is the land to the west of the Caprock Escarpment, which separates it from plains stretching to the east at a much lower elevation....
) and geochemical trapping mechanisms would prevent the CO
2 from escaping to the surface.
CO
2 is sometimes injected into declining oil fields to
increase oil recoveryEnhanced Oil Recovery is a generic term for techniques for increasing the amount of crude oil that can be extracted from an oil field...
. Approximately 30 to 50 million metric tonnes of CO
2 are injected annually in the United States into declining oil fields.. This option is attractive because the geology of hydrocarbon reservoirs are 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 CO
2 emissions.
Unminable coal seams can be used to store CO
2 because CO
2 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 recoveryEnhanced coal bed methane recovery is a method of producing additional coalbed methane from a source rock, similar to enhanced oil recovery applied to oil fields...
). The sale of the methane can be used to offset a portion of the cost of the CO
2 storage. However, burning the resultant methane would produce CO
2, which would negate some of the benefit of sequestering the original CO
2.
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 CO
2 back into the atmosphere may be a problem in saline aquifer storage. However, current research shows that several
trapping mechanisms immobilize the CO
2 underground, reducing the risk of leakage.
For well-selected, designed and managed geological storage sites, the IPCC estimates that CO
2 could be trapped for millions of years, and the sites are likely to retain over 99% of the injected CO
2 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.
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 bicarbonate
In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...
s (using limestoneLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geologic record...
)
- Store the CO2 in solid clathrate hydrate
Clathrate hydrates are crystalline water-based solids physically resembling ice, in which small non polar molecules are trapped inside "cages" of hydrogen bonded water molecules...
s already existing on the ocean floor, or growing more solid clathrate.
The environmental effects of oceanic storage are generally negative, but poorly understood. Large concentrations of CO
2 kills ocean organisms, but another problem is that dissolved CO
2 would eventually equilibrate with the atmosphere, so the storage would not be permanent. Also, as part of the CO
2 reacts with the water to form
carbonic acidCarbonic acid has the formula H2CO3. It is also a name sometimes given to solutions of carbon dioxide in water, which contain small amounts of H2CO3. The salts of carbonic acids are called bicarbonates and carbonates. It is a weak acid...
, H
2CO
3, 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 CO
2 are estimated at US$40−80/ton. (2002 USD) This figure covers the cost of sequestration at the powerplant and naval transport to the disposal site. [2]
The bicarbonate approach would reduce the pH effects and enhance the retention of CO
2 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 fanAn alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain...
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 MexicoThe Gulf of Mexico is the ninth largest body of water in the world. Considered a smaller part of the Atlantic Ocean, it is an ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United...
and the Nile alluvial fan in the
Mediterranean SeaThe Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by Africa, and on the east by the Levant. The sea is technically a part of the Atlantic Ocean, although it...
.
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.
In this process, CO
2 is
exothermicIn thermodynamics, the term exothermic describes a process or reaction that releases energy usually in the form of heat, but also in the form of light , electricity , or sound. Its etymology stems from the Greek prefix ex- and the Greek word thermein...
ally 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
limestoneLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geologic record...
. 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
IPCCThe Intergovernmental Panel on Climate Change is a scientific intergovernmental body tasked to evaluate the risk of climate change caused by human activity. The panel was established in 1988 by the World Meteorological Organization and the United Nations Environment Programme , two organizations...
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)
The following table lists principal metal oxides of
Earth's CrustIn geology, a crust is the outermost solid shell of a rocky planet or moon, which is chemically distinct from the underlying mantle. The crusts of Earth, our Moon, Mercury, Venus, Mars, Io, and other planetary bodies have been generated largely by igneous processes, and these crusts are richer in...
. Theoretically up to 22% of this mineral mass is able to form
carbonateIn chemistry, a carbonate is a salt or ester of carbonic acid, characterized by the presence of the carbonate ion, or a carbonate functional group O=C2....
s.
| Earthen Oxide | Percent of Crust | Carbonate | Enthalpy change The standard enthalpy change of reaction is the enthalpy change that occurs in a system when one mole of matter is transformed by a chemical reaction under standard conditions.For a generic chemical reaction...
(kJ/mol) |
|---|
| SiO2 |
59.71 |
|
|
| Al2O3 |
15.41 |
|
|
| CaO |
4.90 |
CaCO3Calcium carbonate is a chemical compound with the chemical formula CaCO 3. It is a common substance found in rock in all parts of the world, and is the main component of shells of marine organisms, snails, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural...
|
-179 |
| MgO |
4.36 |
MgCO3 Magnesium carbonate, MgCO3, is a white solid that occurs in nature as a mineral. Several hydrated and basic forms of magnesium carbonate also exist as minerals...
|
-117 |
| Na2O |
3.55 |
Na2CO3Sodium carbonate , , is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate; and is domestically well known for its everyday use as a water softener...
|
|
| FeO |
3.52 |
FeCO3 |
|
| K2O |
2.80 |
K2CO3 Potassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...
|
|
| Fe2O3 |
2.63 |
FeCO3 |
|
|
21.76 |
All Carbonates |
Leakage
A major concern with CCS is whether leakage of stored CO
2 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. CO
2 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 CO
2 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 CO
2 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 CO
2 alert meters around the project perimeter has been proposed.
In 1986 a large leakage of naturally sequestered carbon dioxide rose from
Lake NyosLake Nyos is a crater lake in the Northwest Province of Cameroon, located about northwest of Yaoundé. Nyos is a deep lake high on the flank of an inactive volcano in the Oku volcanic plain along the Cameroon line of volcanic activity...
in
CameroonThe Republic of Cameroon is a unitary republic of central and western Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the Bight of...
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.
For ocean storage, the retention of CO
2 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–CO
2(l) mixing is
very low (where carbonate formation/acidification is the rate limiting step), but the formation of water-CO
2 hydrates is favorable. (a kind of solid water cage that surrounds the CO
2). [3]
To further investigate the safety of CO
2 sequestration, we can look into Norway's
Sleipner gas fieldThe Sleipner gas field is a natural gas field in the North Sea, about 250 km west of Stavanger, Norway. Two parts of the field are in production, Sleipner West , and Sleipner East . The field produces natural gas and light oil condensates from sandstone structures about 2500 m below sea level...
, as it is the oldest plant that stores CO
2 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 CO
2 was the most definite form of permanent
geological storage of CO
2. [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]
Phase I of the
Weyburn Project in
Weyburn, SaskatchewanWeyburn is a city in southeastern Saskatchewan, Canada. It is located on the Souris River southeast of the provincial capital of Regina and is north of the border with the United States. The name is reputedly a corruption of the Scottish "wee burn," referring to a small creek...
, Canada has determined that the likelihood of stored CO
2 release is less than one percent in 5,000 years.
CO2 re-use
A potentially useful way of dealing with industrial sources of CO
2 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. Currently, biofuels represent the other potentially carbon-neutral
jet fuelJet fuel is a type of aviation fuel designed for use in aircraft powered by gas-turbine engines. It is clear to straw colored. The most common fuels are Jet A and Jet A-1 which are produced to an internationally standardized set of specifications...
available.
Carbon dioxide scrubbing variants exist based on
potassium carbonatePotassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...
which can be used to create liquid fuels. Although the creation of fuel from atmospheric CO
2 is not a
geoengineeringThe modern concept of geoengineering is usually taken to mean proposals to deliberately manipulate the Earth's climate to counteract the effects of global warming from greenhouse gas emissions...
technique, nor does it actually function as
greenhouse gas remediationGreenhouse gas remediation projects are a type of geoengineering and seek to remove greenhouse gases from the atmosphere, and thus tackle the root cause of climate change. These techniques either directly remove greenhouse gases, or alternatively seek to influence natural processes to remove...
, it nevertheless is potentially very useful in the creation of a low carbon economy, as transport fuels, especially
aviation fuelAviation fuel is a specialized type of petroleum-based fuel used to power aircraft. It is generally of a higher quality than fuels used in less critical applications such as heating or road transport, and often contains additives to reduce the risk of icing or explosion due to high temperatures,...
, are currently hard to make other than by using
fossil fuelFossil fuels or mineral fuels are fuels formed by natural resources such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...
s. Whilst
electric carAn electric car is an alternative fuel automobile that uses electric motors and motor controllers for propulsion, in place of more common propulsion methods such as the internal combustion engine . Electric cars are a specifically a variety of electric vehicle intended for use as a road-going...
technology is widely available, and can be used with
renewable energyRenewable energy is energy generated from natural resources—such as sunlight, wind, rain, tides, and geothermal heat—which are renewable . In 2006, about 18% of global final energy consumption came from renewables, with 13% coming from traditional biomass, such as wood-burning...
for
carbon neutralBeing carbon neutral, or having a net zero carbon footprint, refers to achieving net zero carbon emissions by balancing a measured amount of carbon released with an equivalent amount sequestered or offset...
driving, there are no electric jet airliners available, nor are there likely to be in the foreseeable future.
Single step methods: CO2 + H2 → methanol
A proven process to produce a hydrocarbon is to make
methanolMethanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with formula CH3OH . It is toxic: drinking 10 ml will cause blindness, and as little as 100 ml will cause death...
. Methanol is rather easily synthesised from CO
2 and H
2 (See
Green Methanol SynthesisGreen-Methanol Synthesis or Green-Methanol is entirely developed from renewable sources of energy. Methanol made from this process would predominately synthesize from the following reaction:
How this differs from traditional methanol synthesis processes is what makes this process green. ...
). Based on this fact the idea of a
methanol economyThe methanol economy is a suggested future economy in which methanol replaces fossil fuels as a means of energy storage, fuel and raw material for synthetic hydrocarbons and their products. It offers an alternative to the proposed hydrogen economy or ethanol economy.In 2005 Nobel prize winner...
was born.
Single step methods: CO2 → 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 CO
2 to create hydrocarbons.
2 Step methods: CO2 → CO → Hydrocarbons
If CO
2 is heated to 2400°C, it splits into carbon monoxide and oxygen. The
Fischer-Tropsch processThe Fischer–Tropsch process is a catalyzed chemical reaction in which synthesis gas, a mixture of carbon monoxide and hydrogen, is converted into liquid hydrocarbons of various forms. The most common catalysts are based on iron and cobalt, although nickel and ruthenium have also been used...
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 LaboratoriesSandia National Laboratories, which is managed and operated by the Sandia Corporation , is a major United States Department of Energy research and development national laboratory with two locations, one in Albuquerque, New Mexico and the other in Livermore, California...
, 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 MayJames Daniel May is a British television presenter and award-winning journalist.May is best known as co-presenter of the motoring programme Top Gear alongside Jeremy Clarkson and Richard Hammond. He also writes a weekly column for The Daily Telegraph's motoring section...
, the British TV presenter, visited a demonstration plant in a recent programme in his 'Big Ideas' series.
Example CCS projects
As of 2007, four industrial-scale storage projects are in operation.
SleipnerThe Sleipner gas field is a natural gas field in the North Sea, about 250 km west of Stavanger, Norway. Two parts of the field are in production, Sleipner West , and Sleipner East . The field produces natural gas and light oil condensates from sandstone structures about 2500 m below sea level...
http://www.iku.sintef.no/projects/IK23430000/ is the oldest project (1996) and is located in the North Sea where Norway's
StatoilHydroStatoilHydro ASA is a Norwegian energy company, formed by the 2007 merger of Statoil with the oil and gas division of Norsk Hydro. StatoilHydro is the biggest offshore oil and gas company in the world and the largest company by revenue in the Nordic Region...
strips carbon dioxide from natural gas with amine solvents and disposes of this carbon dioxide in a deep saline
aquiferAn aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
. The carbon dioxide is a waste product of the field's natural gas production and the gas contains more (9% CO
2) 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 taxA carbon tax is an environmental tax on emissions of carbon dioxide. Carbon dioxide is a heat-trapping "greenhouse" gas. The purpose of a carbon tax is to protect the environment by reducing emissions of carbon dioxide, helping to mitigate climate change...
es. Since 1996, Sleipner has stored about one million
tonneA tonne or metric ton , also referred to as a metric tonne, is a measurement of mass equal to , or approximately the mass of one cubic metre of water. It is not an SI unit but is accepted for use with the SI...
s CO
2 a year. A second project in the
SnøhvitSnøhvit is the name of a natural gas field in the Barents Sea, situated 140 km northwest of Hammerfest, Norway. Snøhvit is also the name of a development of Snøhvit and the two neighbouring natural gas fields Albatross and Askeladden...
gas field in the
Barents SeaThe Barents Sea is a part of the Arctic Ocean located north of Norway and Russia. It is a rather deep shelf sea , bordered by the shelf edge towards the Norwegian Sea in the west, the island of Svalbard in the northwest, and the islands of Franz Josef Land and Novaya Zemlya in the northeast and...
stores 700,000 tonnes per year.
The Weyburn-Midale CO2 Project is currently the world's largest carbon capture and storage project. Started in 2000, Weyburn is located on an oil reservoir discovered in 1954 in
Weyburn, southeastern SaskatchewanWeyburn is a city in southeastern Saskatchewan, Canada. It is located on the Souris River southeast of the provincial capital of Regina and is north of the border with the United States. The name is reputedly a corruption of the Scottish "wee burn," referring to a small creek...
, Canada. The CO
2 for this project is captured at the
Dakota Gasification CompanyThe Dakota Gasification Company started in 1984 in Beulah, North Dakota with the Great Plains Synfuels Plant. The plant uses lignite coal to make synthetic natural gas. The synthetic natural gas is piped to the Northern Border Pipeline which supplies homes and businesses in the eastern part of the...
plant in
Beulah, North DakotaBeulah is a city in Mercer County, North Dakota, in the United States. The population was 3,152 at the 2000 census. Beulah was founded in 1913....
which has produced methane from coal for more than 30 years. At Weyburn, the CO
2 will also be 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 CO
2 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.
The fourth site is
In Salah, which like Sleipner and Snøhvit is a natural gas reservoir located in
In Salah, AlgeriaIn Salah is an oasis town in central Algeria. It was once an important trade link of the trans-Saharan caravan route. Population 43,680 . The area around In Salah is home to some of Algeria's largest oil and gas reserves and production facilities. The village is located in the heart of the Sahara...
. The CO
2 will be separated from the natural gas and re-injected into the subsurface at a rate of about 1.2 million tonnes per year.
In July 2008, the Government of Alberta announced a $2 billion investment in three to five large-scale carbon capture and storage projects. On June 30, 2009, Government announced three projects it will pursue letters of intent with and work to have the letters signed in the fall. If discussions with these proponents are not successful, Government will evaluate its options and may proceed to discussions with other proponents
http://www.energy.alberta.ca/Initiatives/1438.asp.
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.
Another Canadian initiative called the
Integrated CO2 Network (ICO2N) is a proposed system for the capture, transport and storage of carbon dioxide (CO
2). ICO2N members represent a group of industry participants providing a framework for carbon capture and storage development in Canada.
Based in Wallula, Washington,
Wallula Energy Resource Center is proposing a coal plant that incorporates the use of technology and carbon sequestration in order to create electricity in a clean and environmentally friendly manner. The Wallula Energy Resource Center plans to use Integrated Gasification Combined Cycle (IGCC) to gasify the coal therefore capturing 65% of the coals CO2 and sequestering the CO2 into basalt formations underground. This proposed plant would be able to generate approximately 914 megawatts of electricity, an amount equal to half of Seattle's total power requirements. IGCC, coupled with sequestration, will enable WERC to fully comply with the CO2 emission performance standards recently adopted by Washington State.
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 CO
2 for underground storage. 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 CO
2 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 CO
2 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 CO
2 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, MississippiNatchez is the county seat of, and the largest and only incorporated city within, Adams County, Mississippi, United States. As of the 2000 census, the city had a total population of 18,464. One of Mississippi's oldest cities, it was founded by French colonists in 1716, antedating the current...
. Experimental equipment will measure the ability of the subsurface to accept and retain CO
2.
Currently, the United States government has approved the construction of what is touted as the world's first CCS power plant,
FutureGenFutureGen is a US government project announced by President George W. Bush in 2003; its initial plan involved the construction of a near zero-emissions coal-fueled power plant to produce hydrogen and electricity while using carbon capture and storage....
. 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..
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 CO
2 by storing baking soda in mines, landfills, or simply to be sold as industrial or food grade baking soda.
GreenFuel Technologies Corp. is piloting and implementing algae based carbon capture, circumventing storage issues by then converting algae into fuel or feed.
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.
In the Netherlands, a 68 MW oxyfuel plant ("Zero Emission Power Plant") was being planned to be operational in 2009. However, this project was later cancelled.
In the United States, four different
synthetic fuelSynthetic fuel or synfuel is a liquid fuel obtained from coal, natural gas, or biomass. It may also refer to fuels derived from other solids such as plastics or rubber waste, or from the fermentation of biomatter. It may also refer to gaseous fuels produced in a similar way...
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 CO
2 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.)
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 CO
2 for Enhanced Oil Recovery.
Rentech is developing a
29,600 barrel per day coal and biomass to liquids plant in Natchez Mississippi which will market the plant’s CO
2 for enhanced oil recovery. The first phase of the project is expected in 2011.
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 CO
2 for enhanced oil recovery. The project is expected to begin operation in 2013.
The
Basin Electric Power CooperativeBasin Electric Power Cooperative is a wholesale electric generation and transmission cooperative based in North Dakota that provides electricity to 2 million customers in nine U.S. states. The roots of the cooperative go back to 1960 when Leland Olds and ten power suppliers created Giant Power...
in North Dakota captures half of it's CO2.
http://cnettv.cnet.com/60-minutes-powered-coal/9742-1_53-50070761.html?tag=untagged
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).
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 . 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 . BP have subsequently withdrawn from the competition claiming it could not find a power generator partner and RWE
npowerNpower is a UK based electricity and natural gas supply company, formerly known as Innogy plc. As Innogy plc it was listed on the London Stock Exchange and was a constituent of the FTSE 100 Index but it is now owned by RWE of Germany.- History :The Company was established as Innogy plc from the UK...
is seeking a judicial review of the process after it did not qualify .
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).
Germany
The German industrial area of Schwarze Pumpe, about 4 km south of the city of
SprembergSpremberg is a city in the Spree-Neiße district of Brandenburg, Germany. The town was first mentioned in 1301 and has about 25,000 inhabitants.-Geography:...
, is home to the world's first CCS coal plant. The mini pilot plant is run by an
AlstomAlstom is a large French multinational conglomerate which holds interests in the power generation and transport markets. According to the company website, in the years 2007-'08 Alstom had annual sales of over €16.9 billion, and employed more than 81,500 people in 70 countries. Alstom's...
-built
oxy-fuelOxy-fuel refers to technology that burns oxygen with gaseous fuel. As compared to air, which contains 20.95% oxygen, higher temperatures can be reached using pure oxygen. Approximately the same total energy is produced when burning a fuel with oxygen as compared to with air; the difference is the...
boiler and is also equipped with a flue gas cleaning facility to remove
fly ashFly ash is one of the residues generated in the combustion of coal. Fly ash is generally captured from the chimneys of coal-fired power plants, and is one of two types of ash that jointly are known as coal ash; the other, bottom ash, is removed from the bottom of coal furnaces...
and sulphur dioxide. The Swedish company Vattenfall AB invested some 70 million
EuroThe euro is the official currency of 16 of the 27 Member States of the European Union . The states, known collectively as the Eurozone, are Austria, Belgium, Cyprus, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Malta, the Netherlands, Portugal, Slovakia, Slovenia and Spain...
s 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. 240 tonnes a day of CO
2 are being trucked 350 kilometres (210 miles) where it will be injected into an empty gas field. Germany's
BUND groupBund für Umwelt und Naturschutz Deutschland is the German Branch of Friends of the Earth .- General Facts :...
called it a "
fig leafA fig leaf is the covering up of an act or an object that is embarrassing or disagreeable. The term is a metaphorical reference to the Biblical Book of Genesis, in which Adam and Eve used fig leaves to cover "their nakedness" after eating the fruit from the Tree of Knowledge of Good and...
". For each tonne of coal burned, 3.6 tonnes of carbon dioxide is produced.
German utility
RWERWE AG , is a German electric power and natural gas public utility company based in Essen. Through its various subsidiaries, the energy company contributes electricity and gas to more than 20 million electricity customers and 10 million gas customers, principally in Europe...
operates a pilot-scale CO
2 scrubber at the lignite-fired Niederaußem power station built in cooperation with
BASFBASF SE is a German chemical company and the largest chemical company in the world. BASF originally stood for Badische Anilin- und Soda-Fabrik . Today, the four letters are a registered trademark and the company is listed on the Frankfurt Stock Exchange, London Stock Exchange, and Zurich Stock...
(supplier of detergent) and
LindeThe Linde Group, registered as Linde AG is an international industrial gases and engineering company founded in 1879. Linde shares are traded on all the German stock exchanges and also in Zürich, and the Linde share price is included in the DAX 30 index...
(engineering).
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). It is funded jointly by government and industry. It aims to store up to 100,000 tonnes of carbon dioxide extracted from a gas well. Carbon dioxide-rich gas is extracted from a reservoir via a well, compressed and piped 2.25 km to a new well. There the gas is injected into a depleted natural gas reservoir approximately two kilometres below the surface. The Otway Project is a research and demonstration project, focussed on comprehensive monitoring and verification .
This plant does not propose to capture CO
2 from coal fired power generation. There is no project anywhere in the world storing CO
2 stripped from the products of combustion of coal burnt for electricity generation at coal fired power stations 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. 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 CO
2 abatement remain high, at approximately 80-90% compared to a plant without CCS. 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.
A second concern regards the permanence of storage schemes. It is claimed that safe and permanent storage of CO
2 cannot be guaranteed and that even very low leakage rates could undermine any climate mitigation effect. However, the IPCC conclude that the proportion of CO
2 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.
Finally there is the issue of cost.
GreenpeaceGreenpeace is a non-governmental organization for the protection and conservation of the environment. Greenpeace uses direct action, lobbying and research to achieve its goals. Greenpeace has a worldwide presence with national and regional offices in 46 countries, which are affiliated to the...
claim that CCS could lead to a doubling of plant costs. However CCS may still be economically attractive in comparison to other forms of low carbon electricity generation. It is also claimed by opponents to CCS that money spent on CCS will divert investments away from other solutions to climate change.
Cost of CCS
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$60 per US-ton is required to make capture and storage competitive, corresponding to an increase in electricity prices of about US 6c per kWh (based on typical coal fired power plant emissions of 2.13 pounds CO
2 per kWh). This would double the typical US industrial electricity price (now at around 6c per kWh) and increase the typical retail residential electricity price by about 50% (assuming 100% of power is from coal, which may not neccesarily be the case, as this varies from state to state). However similar (approximate) price increases would likely be expected in coal dependent countries such as Australia, because the capture technology and chemistry, transport and injection costs from such power plants would not, in an overall sense, vary significantly from country to country.
The reasons that CCS is expected to cause such power price increases are several. Firstly, the increased energy requirements of capturing and compressing CO
2 significantly raises the operating costs of CCS-equipped power plants. In addition there are added investment or capital costs. The process would increase the fuel requirement of a plant with CCS by about 25% for a coal-fired plant and about 15% for a gas-fired plant. The cost of this extra fuel, as well as storage and other system costs are estimated to increase the costs of energy from a power plant with CCS by 30-60%, depending on the specific circumstances. Pre-commercial CCS demonstration projects are likely to be more expensive than mature CCS technology, the total additional costs of an early large scale CCS demonstration project are estimated to be €0.5-1.1bn per project over the project lifetime.
An estimate of costs of energy with and without CCS (2002 US$ per kWh)
| |
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 Enhanced Oil Recovery is a generic term for techniques for increasing the amount of crude oil that can be extracted from an oil field...
|
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 The lower heating value of a fuel is defined as the amount of heat released by combusting a specified quantity and returning the temperature of the combustion products to 150 °C.Which means that, LHV assumes all the water component is in vapor state at the end of combustion...
based). Energy costs for PC and IGCC are based on bituminous coalBituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen. It is of higher quality than lignite coal but of poorer quality than anthracite coal....
costs of US$1.00–1.50 per GJ LHVThe lower heating value of a fuel is defined as the amount of heat released by combusting a specified quantity and returning the temperature of the combustion products to 150 °C.Which means that, LHV assumes all the water component is in vapor state at the end of combustion...
. 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]. |
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 CO
2 injected, plus an additional US$0.10–0.30 for monitoring costs. However, when storage is combined with
enhanced oil recoveryEnhanced Oil Recovery is a generic term for techniques for increasing the amount of crude oil that can be extracted from an oil field...
to extract extra oil from an oil field, the storage could yield net benefits of US$10–16 per tonne of CO
2 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 plantsThe economics of new nuclear power plants is a controversial subject, since multi-billion dollar investments ride on the choice of an energy source. Nuclear power plants typically have high capital costs for building the plant, but low fuel costs...
.
Environmental effects
The theoretical merit of CCS systems is the reduction of CO
2 emissions by up to 90%, depending on plant type. Generally, environmental effects from use of CCS arise during power production, CO
2 capture, transport and storage. Issues relating to storage are discussed in those sections.
Additional energy is required for CO
2 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 desulfurizationFlue gas desulfurization is commonly known as FGD and is the technology used for removing sulfur dioxide from the exhaust flue gases in power plants that burn coal or oil to produce steam for the steam turbines that drive their electricity generators.Sulfur dioxide is responsible for acid rain...
(FGD) systems for
SO2Sulfur dioxide is the chemical compound with the formula SO
2. It is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide...
control require proportionally greater amounts of limestone and systems equipped with
SCRSelective catalytic reduction is a means of converting nitrogen oxides, also referred to as with the aid of a catalyst into diatomic nitrogen, , and water, . A gaseous reductant, typically anhydrous ammonia, aqueous ammonia or urea, is added to a stream of flue or exhaust gas and is absorbed...
systems for
NOXNox may refer to:* Nox , the Roman translation of Nyx, the primordial goddess of the night in Greek mythology* Nox , a video game developed by Westwood Studios* Nox , a pop band from HungaryIn fiction...
require proportionally greater amounts of
ammoniaAmmonia is a compound of nitrogen and hydrogen with the formula NH
3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers...
.
IPCC has provided estimates of air emissions from various CCS plant designs (see table below). While CO
2 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. |
See also
- Biochar
Biochar is charcoal created by pyrolysis of biomass. The resulting charcoal-like material is a form of biosequestration or atmospheric carbon capture and storage. Charcoal is a stable solid and rich in carbon content, and thus, can be used to lock carbon in the soil...
- Carbon cycle re-balancing
The carbon cycle is the process by which carbon is exchanged between the four reservoirs of carbon: the biosphere, the earth, the air and water. Exchanges take place in several ways, including respiration, transpiration, combustion and decay...
- Carbon sink
- Chemical looping combustion
Chemical looping combustion typically employs a dual fluidized bed system where a metal oxide is employed as a bed material providing the oxygen for combustion in the fuel reactor...
- CO2 sequestration
Carbon sequestration is a geoengineering technique for the long-term storage of carbon dioxide or other forms of carbon, for the mitigation of global warming. Carbon dioxide is usually captured from the atmosphere through biological, chemical or physical processes...
- FutureGen
FutureGen is a US government project announced by President George W. Bush in 2003; its initial plan involved the construction of a near zero-emissions coal-fueled power plant to produce hydrogen and electricity while using carbon capture and storage....
- Limnic eruption
A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which carbon dioxide suddenly erupts from deep lake water, suffocating wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising CO2 displaces water...
A possible hazard resulting from a large scale release of CO2
- Low-carbon economy
A Low-Carbon Economy or Low-Fossil-Fuel Economy is a concept that refers to an economy which has a minimal output of greenhouse gas emissions into the biosphere, but specifically refers to the greenhouse gas carbon dioxide...
- Mitigation of global warming
Mitigation of global warming involves taking actions to reduce greenhouse gas emissions and to enhance sinks aimed at reducing the extent of global warming. This is in distinction to adaptation to global warming which involves taking action to minimize the effects of global warming. Mitigation is...
- Post combustion capture
Post combustion capture refers to the removal of CO2 from power station flue gas prior to its compression, transportation and storage in suitable geological formations, as part of carbon capture and storage. A number of different techniques are applicable, almost all of which are...
- Quaternary recovery
- Solvay process
The Solvay process, also referred to as the ammonia-soda process, is the major industrial process for the production of soda ash . The ammonia-soda process was developed into its modern form by Ernest Solvay during the 1860s...
industrial process used in the production of soda ash (sodium carbonate)
- Terra preta
Terra preta refers to expanses of very dark, fertile anthropogenic soils found in the Amazon Basin. Terra preta owes its name to its very high charcoal content, and was indeed made by adding a mixture of charcoal, bone, and manure to the otherwise relatively infertile Amazonian soil over many years...
- IEA Greenhouse Gas R&D Programme
The IEA Greenhouse Gas R&D Programme is an Implementing Agreement of the International Energy Agency, and was founded in 1991. IEA GHG is an international collaborative research programme focusing its efforts on studying technologies to reduce greenhouse gas emissions...
External links
- 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.
- 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
Scientific American is a popular science magazine published since August 28, 1845, which according to the magazine makes it the oldest continuously published magazine in the United States...
, September 22, 2009.