Analysing Carbon Dioxide Sequestration Environmental Sciences Essay

Global warming the major concern for all the states in the universe.It is chiefly related to increase in the temperature of Earth due to the combustion of fossils fuels. Climatic alterations occur due to alterations in the C dioxide degrees in the atmosphere i.e. more C dioxide accretion in the ambiances. To extenuate planetary clime alteration, a portfolio of schemes will be needed to maintain the atmospheric CO2 concentration below a unsafe degree. In this paper we explore assorted C segregation schemes which are proposed for hive awaying captured CO2 like, the pumping of CO2 into deep ocean where CO2 may respond with H2O under the high force per unit area to organize methane hydrates or corsets in CO2 lakes, burying C indoors deep ocean deposits where conditions are even more stable than ocean underside and the technique that has been most earnestly considered, is to hive away captured CO2 in geological formations such as old mines and deep saline aquifers is besides spectrum of biospheric C segregation methods, such as heightening pelagic plankton productiveness by Fe fertilisation, re-afforestation or changing forestry direction patterns to maximise C stored in dirt and flora. The paper besides emphasizes on the advantages and the drawbacks of these procedures.

Atmospheric CO2 concentration has increased from 280 to 380 ppmv ( parts per million by volume ; a 35 % alteration ) since pre-industrial clip, mostly due to carbon emanations from anthropogenetic dodo fuel combustion and deforestation. The emanation rate of C from fossil fuel ( oil, coal and gas ) ingestion is presently about 8 GtC y-1 ( 1015 g of C per twelvemonth ) while the deforestation rate for the 1990s is estimated to be 1.6 ( 0.5-2.7 ) GtC y-1. The cumulative dodo fuel emanation since 1800 is 330 GtC, but merely about half of that remains in the ambiance ; the balance absorbed by C sinks in the ocean and on land. Fossil fuel emanations are projected to make 9-20 GtC y-1 by 2050 in the absence of clime alteration policies, harmonizing to a scope of emanations scenarios. Depending on how the current C sinks change in the hereafter, the atmospheric CO2 concentration for the Particular Report on Emissions Scenarios ( SRES ) A2 emanations scenario is between 450-600 ppmv by 2050, and 700-1000 ppmv by 2100, and planetary mean surface temperature may increase between 1.5-5.5A°C, with related alterations in sea-level, utmost events, and ecosystem displacements. Scientists have argued that terrible effects will happen one time atmospheric CO2 concentrations reach between 450 and 600 ppmv. Beyond this point, planetary clime alteration would be really hard and dearly-won to cover with. Keeping the atmospheric CO2 concentration below 450- 600 ppmv airss an unprecedented challenge to humanity. There are two chief attacks to undertake this issue:

( 1 ) To cut down emanations ;

( 2 ) To capture CO2 and shop it, i.e. , segregation.

Since our economic system depends to a great extent on fossil fuel, which comprises more than 80 % of primary energy usage, to cut down C emanations requires drastic alterations in energy usage efficiency and the usage of alternate energy beginnings that are by and large non economically competitory at present. Even if advanced engineerings such as H power and atomic merger go economical, the substructure switch will take many decennaries. It is therefore really likely that at least some C segregation will be needed in the close hereafter to maintain CO2 below a unsafe degree. There are chiefly at that place wide categories into which all the CO2 segregation types fall into they are as follows

Tellurian 2. Geological 3. Eastern malayo-polynesian

1. Tellurian segregation

There are chiefly 2 methods which are popular and widely used they are usage of micro beings like micro algae and other method is wood entombment.

( A ) Micro Algae

This procedure is chiefly used in industries like power workss.Here we use specially designed bioreactors to transport on the segregation procedure with aid of micro-organisms like micro algae and bacterium. The bioreactors contain specially selected species of microalgae, suspended in H2O and foods for optimum growing. Fresh, salt, artesian or recycled H2O can be used and hapless quality H2O works good. A watercourse of gas is drawn from the smokestack by a blower from the industry and passed through the bioreactor where the algae, bathed in sunshine, devour the CO2 constituent for photosynthesis. The below figure gives the flow chart of the procedure. They can besides interrupt down nitrogen oxide pollutants. A part of the media is drawn away and goes through a ‘dewatering ‘ procedure to concentrate the algae and eventually give a solid algal bar, suited for oil extraction and other processing. Most of the H2O ( 98 % ) is returned to the bioreactor and the full procedure has a low energy demand. Preliminary trials conducted in the United States by CK Environmental indicate that the algae achieve unprecedented growing rates, enhanced by the add-on of CO2, and are unusually efficient at scouring nursery gases from emanations. Over seven yearss, the bioreactors reduced nitrogen oxide emanations by 85 % and CO2 emanations by 82 % on cheery yearss. Decrease degrees were approximately 50 % for both gases on really nebulose yearss. Bing dependent on sunshine for photosynthesis, the algae work a 12-hour twenty-four hours and strike hard off at dark, although they absorb nitrogen oxides 24 hours a twenty-four hours. The chief advantage of this method is emanations from the industries can be reduced to really low degrees and it is besides less clip pickings and cost effectual. But more elaborate research has to be done in this field

( B ) . Methanogens

This procedure is under research and development. It is done by National thermic power corporation limited with the assistance of Govt. of India. This procedure is chiefly aimed at the production of methane by the usage of methanogenic bacteriums like Methanobacterium, Methanobrevibacter, Methanococcus, Methanocaldococcus jannaschii, Methanothermus sociabilis and Methanopyrus kandleri immobilized in a specially designed bioreactors.The CO2 to be sequestered is flown into this bioreactor in the for of a mixture of fuel gas, H and O.The micro beings in the reactor use these gases as substrate and change over them into methane. The chief advantage of this procedure is that the beings are anaerobiotic, Grow on limited C beginnings ( CO2, ethanoate, methyl alcohol, methylamines ) and Simple nitrogen beginning and we get methane which is a fuel. Presently this procedure is under R & A ; D and the paradigm surveies using this procedure will be finished by 2010.

( C ) Wood burial:

Globally, about 60 GtC y-1 are temporarily sequestered by land flora ( Net Primary Productivity or NPP ) . This C is continuously returned to the ambiance when flora dies and decomposes ( heterotrophic respiration, Rh ) .This is an attack in which we try to halt the CO2from returning to the ambiance In this technique, CO2 gaining control is done by the natural procedure of photosynthesis, and storage is low tech and distributed, therefore attractive in two of import facets: cost and safety. In this technique wood from old or dead trees in the universe ‘s woods is harvested and buried in trenches under a bed of dirt, where the anaerobiotic status slows the decomposition of the inhumed wood. This can be supplemented by selective film editing of other suited trees. Because of the low O status below dirt surface, the decomposition of inhumed wood is expected to be slow. Indeed, merely 0-3 % of the C from wood are of all time emitted as landfill gas after several decennaries, and considered the staying fraction locked off ‘indefinitely ‘ . On the storage side, high-quality wood can besides be stored in shelters for future usage. The chief disadvantage of this procedure is that it is a really slow and clip devouring procedure and involves immense capital. Besides aforestration i.e. , turning of the cut down trees is a procedure which may take old ages.

2. Geological storage

Besides known as geo-sequestration, this method involves shooting C dioxide straight into belowground geological formations like Oil, gas Fieldss, unminable coal mines and saline-filled basalt formations are the storage sites. Disadvantages of old oil Fieldss are their geographic distribution and their limited capacity, every bit good as that the subsequent combustion of the extra oil so recovered will countervail much or all of the decrease in CO2 emanations.

( A ) Mineral storage

In this procedure, CO2 is exothermically reacted with copiously available metal oxides which produce stable carbonates. This procedure occurs of course over many old ages and is responsible for much of the surface limestone. The reaction rate can be made faster, for illustration by responding at higher temperatures and/or force per unit areas, or by pre-treatment of the minerals, although this method can necessitate extra energy. “ Carbon segregation by responding of course happening Mg and Ca incorporating minerals with CO2 to organize carbonates has many alone advantages. Most notably is the fact that carbonates have a lower energy province than CO2, which is why mineral carbonation is thermodynamically favourable and occurs of course ( e.g. , the weathering of stone over geologic clip periods ) . Second, the natural stuffs such as Mg based minerals are abundant. Finally, the produced carbonates are undisputedly stable and therefore re-release of CO2 into the ambiance is non an issue. However, conventional carbonation tracts are slow under ambient temperatures and force per unit areas. The important challenge being addressed by this attempt is to place an industrially and environmentally feasible carbonation path that will let mineral segregation to be implemented with acceptable economic sciences

Mg-Olivine + Water + Carbon dioxide a†’ Serpentine + Magnesite + Silica

( Mg ) 2SiO4 + nH2O + CO2 a†’ Mg3 [ Si2O5 ( OH ) 4 ] + MgCO3 + SiO2 + H2O

( This is a non stoichiometric reaction merely to demo the rule ) .

Fe-Olivine + Water + Carbonic acid a†’ Serpentine + Magnetite + Magnesite + Silica

4 ( Fe, Mg ) 2SiO4 + nH2O + H2CO3 a†’ 2Mg3 [ Si2O5 ( OH ) 4 ] + 2Fe3O4 + 2MgCO3 + SiO2 + H2O

Serpentine + C dioxide a†’ Magnesite + silica + H2O

Mg3 [ Si2O5 ( OH ) 4 ] + 3CO2 a†’ 3MgCO3 + 2SiO2 + 2H2O

Mineral mines can hive away more C dioxide than can be burned by fossil fuel. They are safe, cost efficient, and the C is stored for good as solids. The biggest downside to them is that extended excavation, affecting unknown environmental impacts, would be necessary.

( B ) Abandoned coal Fieldss:

Fractured coal seams routinely contain methane absorbed on the coal surfaces. Removing H2O from the break webs in the coal allows some of the methane to absorb and it can be recovered by boring Wellss into the coal. About 6 per cent of the natural gas used in the US is now supplied by coal-bed methane. CO2 absorbs on coal, and it does so more strongly than methane. Hence, there is a thermodynamic boring force for replacing of methane by CO2. It may be possible to shoot CO2, sequester it, and retrieve methane. Coal Beds are a really good topographic point to hive away CO2. They are lasting, they are cheap, and they result in the recovery of natural gas. There is besides a big storage capacity, although non every bit big as some others. Coal beds are merely a feasible option for 100-200 old ages, so it should be used in concurrence with another engineering

( C ) Old Oil William claude dukenfields:

This method mail focal points on using old or exhausted oil Fieldss where sophisticated techniques are used to sequest C dioxide coupled with bettering the oil recovery.In general footings, C dioxide is flooded into an oil field through a figure of injection Wellss drilled around a bring forthing good. Injected at a force per unit area equal to or above the minimal miscibility force per unit area ( MMP ) , the CO2 and oil mix together and organize a liquid that more easy flows to the production good. Pumping can besides be enhanced by deluging CO2 at a force per unit area below the MMP, swelling the oil and cut downing its viscousness. CO2 EOR has been used by the oil and gas industry for over 40 old ages, but merely late has its possible as a C segregation method been realized and investigated. Presently, CO2 EOR comprises about 37 per centum of all EOR being performed in the United States. Maturing oil Fieldss and lifting oil monetary values have made this method of resource recovery progressively attractive to industry. The United States has been a leader in developing and utilizing engineerings for CO2 EOR by executing about 96 per centum of world-wide CO2 EOR. The chief back bead of this method is depleted Oil and Gas Reservoirs have the unity, but they do n’t hold the size. They merely do n’t hold the storage capacity to be the chief sequestering method. The engineering is besides expensive due to capturing, processing, and transit costs.

3. Ocean storage

Another proposed signifier of C storage is in the oceans. This procedure involves ‘dissolution ‘ injects CO2 by ship or grapevine into the H2O column at deepnesss of 1000 m or more, and the CO2 later dissolves. The denseness of liquid CO2 at this point ( about 0.92 g/cm3 ) is much less than saltwater ( about 1.028 g/cm3 ) , and the droplet will lift easy. However, the incompressibility of saltwater and the high squeezability of liquid CO2 are such that below about 2, 900 m, a denseness reversal occurs and a sinking plume of liquid CO2 can be formed. This has led to suggestions of formation of a `lake ‘ of liquid CO2 on the ocean floor this would detain disintegration of CO2 into the environment. Despite the Oceans have the largest storage capacity of CO2 the chief disadvantage is, big concentrations of CO2 putting to deaths ocean beings, and another job is that dissolved CO2 would finally equilibrate with the ambiance, so the storage would non be lasting. Besides, as portion of the CO2 reacts with the H2O to organize carbonaceous acid, H2CO3, the sourness of the ocean H2O additions. The ensuing environmental effects on benthal life signifiers of the bathypelagic, abyssopelagic and hadopelagic zones are ill understood. Even though life appears to be instead sparse in the deep ocean basins, energy and chemical effects in these deep basins could hold far making deductions. Although some scientists argue that the pH alteration and CO2 concentration alteration would non be important, public perceives “ dumping ” CO2 into the ocean to be a major menace. Public dissent has even hindered research and development of ocean segregation technology.Much more work is needed here to specify the extent of the possible jobs

Decision:

Type of storage

Advantages

Disadvantages

1.Micro algae

Less clip pickings, shop more CO2, cost effectual

Not to the full tested

2.Methanogens

Less clip pickings, methane is produced

Not to the full tested

3.Wood burial

Storage clip is high

Time taking & A ; capital

4.Mineral storage

safe, cost efficient, & A ; the C is stored for good as solids

unknown environmental impacts

5Abandoned coal Fieldss

Methane production

Less storage capacity

6.Old Oil and Gas Fields

Enhanced oil recovery

Less storage capacity

7.Ocean storage

Large storage capacity

Long term effects unknown

We have investigated each method of segregation, and nil leaps out as a unfailing manner to sequester CO2. Each method seems to hold some kind of defect. A Other than EOR, which has been a successful method of oil recovery and C dioxide segregation for over 30 old ages, no engineering is ready to be used on a big graduated table. There is no perfect manner to cover with the C dioxide job. Still, it is unreasonable to anticipate that we, as a planetary community, will be able to go independent of fossil fuels any clip in the close hereafter, and something has to be done with all that C dioxide. There surely are methods of segregation that are feasible storage sites for the disposal of C dioxide. There is no 1 best method for sequestering C dioxide ; each method has its advantages and disadvantages. There fore it would be unjust to wholly govern any method out before they have all been to the full tested.We foresee the hereafter of C dioxide segregation as a combination of all the different methods, with some more outstanding than others.

“ Each and every one of these methods is better than leting C dioxide emanations to go on at its current rate unbridled ” .

A