Geological Sequestration of carbon dioxide
The geological storage of carbon dioxide is planned like one of the possible forms of Séquestration of carbon (or the Carbon dioxide) to limit its contribution to the acidification of the mediums and the climatic Modifications whereas the Forêt S, Tourbière S and oceanic wells of Carbone is not enough any more to absorb the human emissions of CO2, and that the Protocole of Kyōto did not make it possible to decrease the total of the emissions of Gaz to greenhouse effect.
He knows an increasing, theoretical interest starting from the end of the year 1990, then experimental as from the years 2005. He is the subject of a growing number of international projects, supported by the tankers and the States, with some experimental applications.
Principles of sequestration
The Carbon dioxide could theoretically be massively hidden in a protected way.
the rock geological substrate (for a capacity estimated of approximately 2000 gitatonnes of CO2, according to the GIEC which estimates that with technologies to be developed and validate, and an adapted monitoring, more than 99% of CO2 injected over 1.000 years could thus be imprisoned for several million years), by injection via of the wells in gas form Supercritique in permeable rocks or underground “cavities” considered to be sufficiently hermetic,
iojhuygiytfut' se" zqteaqrz" continuation of the exploitation of fossil carbon went.
Artificially to capture carbon dioxide in the air or at the exit of all the chimneys and mufflers is not technically possible today or economically profitable, also the promoters of geological storage project to take it at the exit of the industrial facilities which produce some more.
If the solutions geotechnics were validated, according to the GIEC (in 2005), this solution could potentially answer 10% to 55% of the total effort of reduction to consider for the century 2000-2100.
In layers: the oil and natural gas layers are the candidates most quoted to sequester there of CO2. Injection of CO2 in oil layers being already practiced besides since decades (especially with the Texas), at ends of assisted recovery: Powerful solvent, supercritical CO2 helps to recover part of residual oil of difficult layers or in production decrease. Nevertheless, the large majority of the projects of recovery assisted containing CO2 (CO2-EOR, for) undertaken until now use of CO2 resulting from natural sources.
However, the oil reservoirs are often far away from the great sources of carbon dioxide and the old oil-bearing fields are not very usable (one already injected there sea water, or gas, and the substrate could be clogged). It is an attractive option for the tankers which hope to be able to compensate for the economic costs and energy storage by the additional oil sale.
In coal veins? The Méthane of not exploited coal veins could be exploited and replaced by of CO2, the sale of methane financing the storage of CO2. To reinject gas in the pores of coal is theoretically possible if the layers were not packed after extraction. Experimental pilots test this solution, which could possibly be associated with the gasification with coal, so of the methods convincing and protected were developed. The use of underground coal basins already exploited is almost impossible because of mining depressions which followed the exploitation (Basin of the North of France or Lorraine for example). Problems involved in the acidification of the water of the going up tablecloths would arise too.
the saline Aquifère S are geologically to some extent comparable with the layers of hydrocarbons, but with a capacity much larger. There several mechanisms of trapping seem to be able to immobilize CO2, with less risk of escape than in the coal basins or certain sifted oil-bearing fields of well and sometimes victims of depressions. Their homogeneous distribution in the world would decrease the transport needs of CO2, but they are known little about and their brines do not seem to be able to be sold to make profitable the operation as one can do it in the gas and oil-bearing fields with gas or oil pushed by CO2 injected.
Other places? the solutions now considered always aim sedimentary basins. In volcanic areas, the Basalte presents sometimes an alternation of porous layers and layers tight, which could be also used to store of CO2.
Geological storage between schist layers would be also considered.
Limits and risks
Other limits: the most important sources of CO2 do not emit this gas in a state pure, but diluted, with less than 15%, in exhaust fumes, combustion being done in the Air. There exist nevertheless some industries which generate of concentrated CO2 (purification of the Natural gas).
Projects of “clean” powerplants able to sequester CO2 are being studied, for example via the extraction of exhaust fumes of the boiler; system which could be adapted to existing power stations. But that consumes much energy: approximately the quarter of the production of a coal station. This type of process is in addition accompanied by a local increase in air pollution (+ 11% of the Nox emissions and + 17,9% of SOx in the case of a coal center because especially of the increase associated with consumption with energy and thus with fuel. Desulphurization and deacidification will require a larger quantity of lime, and the treatment of Nox will consume more ammonia.
To burn the fuel with pure oxygen would make it possible to decrease the expensive phase of separation of gases downstream. The recovery of CO2 could be optimized thanks to a thinner (water or CO2) recirculated, but it would be necessary upstream, to produce Oxygène.
The decarbonizing of fuel is very studied; It would act by chemical reactions known as of Gasification for solid fuels, or Reformage for gas, to convert fuel into a mixture of CO (carbon monoxide) and hydrogen, mixes known like " gas of synthèse". CO can then provide hydrogen and of CO2 additional by reaction with steam.
Hydrogen and carbon dioxide separate easily, and hydrogen can then feed a powerplant (turbines or combustible batteries), be useful with petrochemistry, the oil refining, or the production of manure, with a better final energetic efficiency and a power station multiproductrice (cogeneration + production of hydrogen). The gas of synthesis could contribute to produce Benzène, Propylène or Méthanol, bases of other more complex chemical syntheses (of which plastic).
The projects are often pressed on coal and other inexpensive fuels (waste oil, of Bois, municipal or agroalimentary). Sequestration is associated thus more and more at the end of " coal propre". Certain projects use natural gas more expensive, but easier to transform.
In addition to being a Gas with greenhouse effect, CO2 is a gas pollutant, acid, poison gas and heavier than the air. A massive and brutal salting out of great quantity of CO2, in a valley or a residential area would have human and ecological consequences mortally serious. Unknown factors remain as for this risk, in particular in the event of Earthquake, of attack, war, or via or not located new faults, or via wells degraded after closing of storage, or in the event of accident during the injection.
Unknown factors also persist as for the behavior and with the effects chemical and geological in the long run of this acid gas and solvent in supercritical phase, in layers where the natural temperature of the basement can be high.
Risks of escapes
Natural examples let think that sequestration long life is possible, but not without risks: certain layers of Natural gas contain a significant proportion of CO2, preserved under pressure since million years. Nevertheless, of the natural escapes exist, sometimes mortally brutal as in the lake Monun (1984) or in the Lac Nyos where the brutal emission of enormous a " bulle" out of CO2 in 1986 killed 1700 people and of the million animals. There exist also layers of CO2 such as to Montmiral (Drome, France) for example.
The experts, the ecologists, ONGs and the ecologists are still divided on the geological sequestration of CO2, for example supported by organizations as the Fondation Bellona whereas Greenpeace is opposed to it. Among the arguments of the opponents , one can quote:
- risks difficult to quantify, but still unacceptable escapes or accidents (for the storage solutions in gas form or liquid).
- dubious solution, which already seems to serve as a pretext for the perpetuation of the large-scale use and crescent of fossil energies , and of an increased development of the consumer society, the more so as the technique “ CO2-EOR ” of often evoked sequestration, is associated with an increase in the production of oil of the layer where CO2 would be sequestered. The investments authorized for sequestration would be employed better in saving energy and the renewable energies add these detractors.
- solution not encouraging to reduce the fossil fuel wasting growing, without consideration of their carbochimic value for industry.
- solution not immediately operational with security guarantees, and expensive in resources/time/money, which would set up at the detriment of the alternatives to the polluting fossil fuels and sources of conflicts geostrategic, whereas important economies in the short and medium term would be made if the financial effort, human and of research was related to alternative sources; in term of Négawatt S and solar energy in particular (which could also produce Oxygène and Hydrogène by electrolysis of sea water, in littoral zone sub-Saharan in particular, which would be also a possible source of development in “poor” countries often or emerging but rich in solar resources and space likely to accommodate photovoltaic Panneaux (Senegal, Mauritania, Morocco, Algérie…).
- solution not regulating the problem of the emissions quickly increasing of transport (car and plane in particular) (except if there were decarbonizing upstream, solution which seems not very possible short-term and of which the écobilan total remainder to be produced).
- Half-solution, because the thermo plants (with coal especially) remain polluting upstream with the cycle of the extraction and the transport of fuel, under operation, and downstream even with atmospheric emissions to some extent cancelled (Ex: polluted ashes and blast-furnace slags, suffers, heavy metals or the Nox associated). Coal mines causing in addition degasification in the methane air (21 times more at greenhouse effect that CO2).
- solution consuming itself of energy (More 10 to 40%) a fraction of the production of the power station having to be diverted to separate, treat and compress then to hide CO2, reducing the energy efficiency of the process.
- Seuls at best 90% of emitted CO2 can be recovered, on the new or very recent power stations with best technologies available, but this imposes an energy corresponding according to the GIEC on 10 to 40% of that produced by the power station. Other systemic costs could change this figure to 30 60%. These costs calculated for coal centres about 2004, could be increased or balanced according to the prices of the fuel and/or the écotaxes.
With that, the partisans answer:
- That there does not exist credible scenario allowing a sufficient fall of the emissions of CO2 to stabilize the climate only containing renewable and of energy saving.
- That sequestration is not a miracle solution, but can fall under a more general action also including energy saving, the renewable ones, the reafforestation and, polemical subject, the development of the nuclear power.
- That the sites to be used can and must be carefully selected after expertise on the tanks.
- That the coal reserves are still abundant and can ensure the energy independence of country like the United States, China and India.
- Within the framework of the Protocol of Kyōto, the companies sequestering carbon would avoid taxes and could sell their rights of emission, while being able to profit from subsidies and research programs.
Legal aspectsIn particular in the inhabited areas, in the event of damage caused by CO2 hidden on the man or the fauna, who would be responsible? With which belongs hidden CO2? Is it with juridically regarding as a Toxic waste or a Dangerous waste?
The subject in particular was the subject of following work:
- a study of the General advice of the mines realized at the request of the French government
- work of the European Union
- the moratorium emitted by the Convention of London to authorize geological storage in underwater layers.
Actors of the research and the development
France and French-speaking people
- Club CO2
- French Petroleum Institute: IFP
- Carbon Sequestration Leadership Forum
- CCS Association, the U.K.
Operational sitesHere sites where the sequestration of CO2 with large scales is already in progress end 2007.
Sleipner, NorwayIn Sleipner at sea of North, the Statoil Company extracts CO2 from a Natural gas layer (which should not contain with the sale more than 9% of CO2) with amino solvents and since approximately 1996 a million tons of CO2 per annum in a formation saltworks reinjects it, thus saving million euro of tax-carbon.
Weyburn, Saskatchewan, CanadaWith Weyburn since 2000, one injects and stores in a discovered oil field in 1954 and partially exhausted in south-east of the Saskatchewan (Canada) the carbon dioxide produced by a unit of gasification of coal located at Beulah (North Dakota, the United States). This carbon dioxide at a rate of 1,5 million tons per annum makes it possible to increase the production of oil (and thus of carbon dioxide, indirectly). It is the first CO2-EOR project, having had a budget of approximately a billion dollar, associating public and deprived partners of several countries. This layer initially estimated at a billion barrels of petrol, including 350 approximately recoverable million according to the conventional techniques. The application of CO2-EOR technology should make it possible to extract 130 million barrels moreover, the layer remaining active until 2030. Of course, one should not deduce from this example which CO2-EOR technology makes it possible to increase by 35% the ultimate oil reserves in a total way: it can apply only in certain layers, and Weyburn was selected because it lent itself to it particularly well.
The carbon dioxide injection started in the year 2000 and reached since a rate/rhythm from approximately 1,8 million tons per annum. It is the company EnCana which is in charge of the operation.
Salah, AlgeriaOn this gas site of Algeria, they are 1,2 million tons of CO2 which as from 2006 are extracted from natural gas and reinjected in an aquifer underground each year. This site of sequestration forms integral part of a vast project of development of the gas layers of the area, whose production is exported towards Europe after transit by Hassi R' Mel.
Snohvit, Norwaythe project consists in reinjecting in an aquifer CO2 coproduit with gas of this layer, with the image of what is made in Sleipner and with In salah. The injection began in September 2007.
K12b, NetherlandsIt is a small layer about gas Offshore exhausted, into which of CO2 coming from close layers is injected. The operator is Gaz de France
Blue Lake, Colorado, the USAEntered in service at the end of 2007, a small gas pipeline transports a million tons of CO2 per annum since a treatment plant of natural gas towards the existing network of pipelines which forwards CO2 of the layer of sheep mountain to projects EOR of Texas.
ProjectsThey many in the world, are indexed by the International agency of energy and in France by BRGM.
European projectsOnly the projects of great width are quoted here. There also exists of many pilot projects, relating to only a few tens of thousands of tons per annum and for one rather short period, validating the stability of geological formations or technologies employed.
Miller, the United Kingdom: the project includes/understands the construction of a power station with decarbonizing using of natural gas, and the use of CO2dans the layer Miller at sea of North.
- Ketzin, Germany: near to Berlin, the site of this project of demonstration is an anticlinal formation in an aquifer which was used with seasonal storage as natural gas but is abandoned.
- Lindach, Austria: the sources would be here a pulp mill and a factory of manure, adding up 300.000 tonnes/an. The trap would be a small exhausted gas layer.
- Layer " Casablanca" , Spain: It is still about a project of sequestration in an old oil reservoir, but assisted recovery: the production of oil will be definitively stopped before the injection of CO2 starts. This small layer is located at broad Tarragone and 500.000 tonnes/an of CO2 per annum coming from the refinery of this city will be hidden there.
- Lacq, Aquitanian: The first French project, announced by Total in 2005, is a project aiming at the demonstration of all the chain of Oxycombustion, since the production of oxygen to the injection and storage of CO2 in a layer One-Shore of exhausted natural gas. An existing boiler on the site of Lacq will be converted with oxygen using a technology of oxycombustion Liquid air (technological partner). The smoke of oxycombustion, deprived of the ballast nitrogenizes air, are mainly made up of CO2 and water. After condensation of water, they compressed, will be dried and transported at the head well of Russet-red, or they will be recomprimées before being injected. An important study géosciences was started, including industrial partners and academic, aiming guaranteeing the integrity of the tank and at obtaining an invaluable experience feedback on this pilot.
The United States has an long experience of CO2-EOR technology. The main objective is now to build powerplants equipped with sequestration of CO2.
Western Canada: many gas layers of this area contain an appreciable share of H2S and CO2. Many operators inject its gases in exhausted aquifers or layers. These operations were undertaken with an aim of getting rid of H2S, gas very pollutant, but they sequester also small quantity of CO2.
- Rangely, Colorado: Active CO2-EOR since 1986 using part of CO2 produced while associating with natural gas and helium with LaBarge.
- Reservoirs oil of the Wyoming: CO2, also coming from the factory from traintement of LaBarge, is forwarded to several layers via a new pipeline. It feeds mainly the two large layers of Salt Creek (commercial project of Anadarko, aiming especially to the production of oil) and of Teapot Dome (project public, priviliégiant the sequestration of CO2. Several less layers will be connected
- Carson, California: the project includes/understands the construction of a power station with gasification transforming the oil residues produced by a hydrogen refinery, and the use of CO2 (4 million tons per annum during 10 years as from 2011, which does of them one of the more great projects of the world) in an oil reservoir.
- Central of Saskpower: this Canadian electric company envisages a coal station using the technology of oxycombustion, of a capacity of 300 MW, which would enter in service at the beginning of the next decade if the project is approved.
- Futuregen: headlight project of the Department off Energy in the United States. It is about a power station with precombustion of approximately 300 MW, whose localization is not decided yet.
- Kenai, Alaska: The project “Blue Sky” aims at converting an existing factory of manure to use the gasification of coal instead of the natural gas (product whose local resources become exhausted). CO2 would be used in the oil reservoirs of bay as Cook.
- New Haven, Virginia-Western: Announced by American Electric Power in March 2007, this project will apply sequestration post-combustion to part of exhaust fumes of a large coal station. Approximately 100.000 t/an of CO2 will be sequestered in an aquifer room, very deep. The project could be operational since 2008, and should give rise to a larger version, installed in Oklahoma, for 1,5 Mt/an in 2010.
- Gorgon, Australia: another project in aquifer, associated with the exploitation of a group of natural gas layers containing too much CO2.
- Stanwell, Australia: a coal station, cousin of American the Futuregen project, whose CO2 would be sent in an aquifer. If the project is concluded, it could be in operation since 2010.
- Sécunda, South Africa: Still at the stage of the first studies, this project would store of CO2 resulting from the production of synthetic fuels in coal veins.
FuturologyIn the projects carried out up to now, a source of CO2 is connected directly to a project of sequestration. It is not inevitably the best solution: this direct connection makes the two elements interdependent. The lifespan of a CO2-EOR project is typically of about fifteen year, whereas a powerplant is built for 40 years. In the long term, several sources and several sites of sequestrations will be probably connected, there is already a network of CO2 in the Permian Basin .
applications “upstream” to the transport sector, even of the heating are considered, by converting beforehand fossil energies into a form of “decarbonized” energy (completely: electricity, Hydrogen, or partially, like Methanol).
Another possible improvement would be the chemical combustion fuels on fluidized bed, possibly catalyzed is considered; oxygen gas but would not be adsorbed there on metal particles (oxides) reusable ( chemical loop combustion ). The emissions then primarily would consist of CO2 and steam which can be separated by condensation, after which the metal particles are reloaded out of oxygen in the air on another fluidized bed, with recovery of heat.
Systems of artificial photosynthesis or starting from marine or terrestrial plants doped, or starting from GMO are evoked or under study, which could be associated with a passive geological storage (sedimentation in the oceans) or credits, but all the cases with environmental cost high and/or risks, broad uncertainties and outputs much lower than those of the wells of carbon vegetable, planktonique or coral natural.
ConclusionThe sequestration of CO2 studied by GIEC, interests a growing number of researchers and decision makers, as well as the public, but does not seem to be a solution available in the short run nor operational to medium-term large scales. Experiments are in hand and ten industrial projects of scale could be operational in 2010, but they will remain unimportant per annum compared to the world emissions of approximately 25 billion tons of CO2. To sequester only 10% of these emissions, one would need approximately 1000 projects of great scale, and several hundreds of made safe sites, as well as thousands of kilometers of pipeline or thousands of special ships to transport liquefied or inerted CO2. A reduction in the emissions to the source (Factor 4 or 5) and the protection and restoration of the sand pipes of carbon thus seem to remain an urgent priority, still to implement. The government of the the United States approved the construction of the first power station of the CCS of the world (FutureGen), and BP envisages a factory of capture and storage of carbon of 350 MW in Scotland; separate CO2 of natural gas will be injected into the gas field of Miller (the North Sea). In Europe, the " project; CASTOR" is of " to define stratégies" in the long term allowing to sequester 10% of the emissions of CO2 European, that is to say 30% of those of the powerplants and other great fixed sources (refineries, heavy industry). This figure is fixed only for the study of scenarios and not like a real objective.
- Cycle of carbon
- Sequestration of carbon
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