ASSIGNMENT

GEO-SEQUESTRATION

M.Sc.(tech.) Environmental Science & Technology (CEST)

RAJIV GANDHI SOUTH CAMPUS BARKACHHA MIRZAPUR

BANARAS HINDU UNIVERSITY

SUPERVISED BY: SUBMITTED BY:

VIJAYKRISHNA SIR KAUSHIK KUMAR

M.Sc.(tech.) 3rd SEM.

CONTENT:

1. Introduction

2. Need for Geo-sequestration

3. CO2 Capture Methods

3.1 Post combustion process

3.2 Pre combustion process

3.3 Oxy-Fuel method

4. CO2 transport

5. CO2 storage

5.1 Geological storage

5.2 Ocean Storage

5.3 Mineral storage

6. Storage capacity of Different reservoirs

7.Types of Geo-sequestration process

8. Advantages and Disadvantages

9. Conclusion

10. Reference

INTRODUCTION :

Carbon dioxide is a chemical compound composed of one carbon and two

oxygen atoms. It is often referred to by its formula CO2. It is present in the Earth's atmosphere at a low concentration (0.03%) and acts as a greenhouse gas. The initial carbon dioxide in the atmosphere of the young Earth was produced by volcanic activity; this was essential for a warm and stable climate conducive to life. Now, a days volcanic releases are about 1% only of the amount of CO2, which is released by human activities.

Since the start of the Industrial Revolution, the atmospheric CO2

concentration has increased by approximately 110 µL/L or about 40%, most

of it released since 1945. Burning fossil fuels such as coal and petroleum is the

leading cause of increased man-made CO2; deforestation is the second major

cause. Around 24,000 million tons of CO2 are released per year worldwide,

equivalent to about 6,500 million tons of carbon. Various techniques have been

proposed for removing excess carbon dioxide from the atmosphere in carbon

dioxide sinks. A carbon dioxide sink is a carbon reservoir that is increasing in size,

and is the opposite of a carbon "source". This concept of CO2 sinks has become

more widely known because the Kyoto Protocol allows the use of carbon dioxide

sinks as a form of carbon offset. Carbon sequestration is the term describing

processes that remove carbon from the atmosphere. To help mitigate global

warming, a variety of means of artificially capturing and storing carbon – as well as

of enhancing natural sequestration processes – are being explored.

The Global Warming Theory (GWT) predicts that increased amounts of

CO2 in the atmosphere tend to enhance the greenhouse effect and thus

contribute to global warming. The effect of combustion-produced carbon dioxide

on climate is called the Callendar effect.

DEFINITION :

Geosequestration is the deep geological storage of carbon dioxide from major industrial sources such as: fossil fuel-fired power stations, oil and natural gas processing, cement manufacture, iron and steel manufacture and the petrochemical industries instead of allowing it to disperse in air. Geosequestration represents perhaps the only option for decreasing greenhouse gas emissions while using fossil fuels and retaining our existing energy- distribution infrastructure.

General Process Description:

In a typical CO2 Capture package,

1. hot flue gas passes through the scrubber tower, where it is cooled with cooling water

2. before being fed to the absorber tower. The gas enters near the bottom of the absorber tower and flows upwards through the internal packing

3.coming into contact with the solvent, which enters near the top of the tower, as the solvent cascades down through the tower. As the flue gas rises through the tower the carbon dioxide level is progressively reduced as it is absorbed by the solvent meaning the treated gas vented from the absorber is virtually free of CO2.

4.From the bottom of the absorber tower the CO2-rich solvent is pumped through the lean-rich exchanger.

5. to pre-heat the solvent before it enters the regenerator tower. In the regenerator the solvent is heated via the reboiler

6. to reverse the absorption reaction. As the solvent cascades down through the tower, CO2 is gradually desorbed from the solvent

7. By the time the solvent reaches the bottom of the tower virtually all the absorbed CO2 has been released and the CO2-lean solvent is cooled and pumped back to the top of the absorber tower to repeat the process .

8.The desorbed CO2 exits the regenerator tower as a pure, water saturated gas from where it is cooled

9.and then passes through the reflux accumulator to remove excess water . The pure carbon dioxide product gas is then ready for direct use or further processing.

CO2 capture methods: Capturing CO2 can be applied to large point sources, such as large fossil fuel or biomass energy facilities, major CO2 emitting industries, natural gas production, synthetic fuel plants and fossil fuel-based hydrogen production plants. Broadly, three different types of technologies exist:

1.Post-combustion: In post-combustion, 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 gases at power stations (in the case of coal, this is sometimes known as "clean coal"). The technology is well understood and is currently used in niche markets.

2.Pre-combustion:

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 gasified and the resulting CO2 can be captured from a relatively pure exhaust stream.

3.Chemical looping combustion(oxyfuel combustion):

An alternate method, which is under development, is the chemical looping combustion (also called “oxyfuel combustion” or simply “oxy-combustion”). Chemical looping uses a metal oxide as a solid oxygen carrier. Metal oxide particles react with a solid, liquid or gaseous fuel in a fluidized bed combustor, producing solid metal particles and a mixture of carbon dioxide and water vapor. The water vapor is condensed, leaving pure carbon dioxide, which can be sequestered. The solid metal particles are circulated to another fluidized bed where they react with air, producing heat and regenerating metal oxide particles that are recirculated to the fluidized bed combustor.

CO2 transport: After capture, the CO2 must be transported to suitable storage sites. Those storage sites are not necessarily located in the same area as the CO2 emitting plants. Hence, transportation remains issue and pipelines, which are generally the cheapest form of transport, or ships (when no pipelines are available) are required for CO2 transportation. Note that both methods are currently used for transporting CO2 for other applications. In order for CO2 transportation to be economically viable, especially for the huge volumes produced by emitting plants, CO2 would need to be compressed and liquefied. According to the Fraunhofer Institute, the liquefaction of CO2 from atmospheric pressure to 110 bar would require 0,12 kWh per tonne of CO2.

CO2 storage: Various forms of more or less permanent storage of CO2 isolated from the atmosphere have been conceived. These are storage in various deep geological formations (including saline formations and exhausted gas fields), ocean storage, and reaction of CO2 with metal oxides to produce stable carbonates. As of 2005, it is estimated that saline formations would offer storage capacities for approx. 50-100 years. However, tectonic movements may have significant impacts on the usability and durability of those storage sites. Also, the geographical location of some saline formations may make transportation of CO2 difficult – or even impossible.

I. Geological storage: Also known as geo-sequestration, this method involves injecting carbon dioxide

directly into underground geological formations (usually in depths of approx. 1,000–2,500 meters). Oil fields, gas fields, saline formations, and unminable coal seams have been suggested as storage sites. Here, various physical (e.g., highly impermeable cap rock) and geochemical trapping mechanisms would prevent the CO2 from escaping to the surface. CO2 is sometimes injected into declining oil fields to increase oil recovery. This option is attractive because the storage costs are offset by the sale of additional oil that is recovered. Disadvantages of old oil fields are their geographic distribution and their limited capacity. Unminable coal seams can be used to store CO2, because CO2 adsorbs to the coal surface, but the technical feasibility depends on the permeability of the coal bed. In the process it releases methane, that was previously adsorbed to the coal surface, and that may be recovered. Again the sale of the methane can be used to offset the cost of the CO2 storage. 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. This will reduce the distances over which CO2 has to be transported. The major disadvantage of saline aquifers is that relatively little is known about them, compared to oilfields. To keep the cost of storage acceptable the geophysical exploration may be limited, resulting in larger uncertainty about the aquifer structure. Unlike storage in oil fields or coal beds no side product will offset the storage cost. Leakage of CO2 back into the atmosphere may be a problem in saline aquifer storage. However,

current research shows that several trapping mechanisms immobilize the CO2 underground, reducing the risk of leakage. For well-selected, designed and managed geological storage sites, IPCC estimates that CO2 could be trapped for millions of years, and the sites are likely to retain over 99% of the injected CO2 over 1,000 years.

II. Ocean storage:

Another proposed form of carbon storage is in the oceans. The following two

main concepts exist:

• The dissolution type injects CO2 by ship or pipeline into the water column at depths of 1,000 meters or more, and the CO2 subsequently dissolves.

• The lake type deposits CO2 directly onto the sea floor at depths greater

than 3,000 meters, where CO2 is denser than water and is expected to form a 'lake' that would delay dissolution of CO2 into the environment. A third concept is to convert the CO2 to bicarbonates (using limestone) or hydrates.

The environmental effects of ocean storage are generally negative. Large concentrations of CO2 kill ocean organisms, but another problem is that dissolved CO2 would eventually equilibrate with the atmosphere, so the storage would not be permanent. Also, as part of the CO2 reacts with the water to form carbonic acid, H2CO3, the acidity of the ocean water increases. The resulting environmental effects on benthic life forms of the bathypelagic, abyssopelagic and hadopelagic zones are poorly understood. Even though life appears to be rather sparse in the deep ocean basins, energy and chemical effects in these deep basins could have far reaching implications. Much more work is needed here to define the extent of the potential problems.

The time it takes water in the deeper oceans to circulate to the surface has been estimated to be on the order of 1,600 years, varying upon currents and other changing conditions. Costs for deep ocean disposal of liquid CO2 are estimated at $40-80 per ton. This figure covers the cost of sequestration at the power plant and naval transport to the disposal site. The bicarbonate approach would reduce the pH effects and enhance the retention of CO2 in the ocean, but this would also increase the costs and other environmental impacts. An additional method of long-term ocean-based sequestration is to gather crop residue such as corn stalks or excess hay into large weighted bales of biomass and deposit it in the alluvial fan areas of the deep ocean basin. Dropping these residues in alluvial fans would cause the residues to be quickly buried in silt on the sea floor, sequestering the biomass for very long time spans. Alluvial fans exist in all of the world's oceans and seas where river deltas fall off the edge of the continental shelf such as the Mississippi alluvial fan in the Gulf of Mexico and the Nile alluvial fan in the Mediterranean Sea.

III. Mineral storage:

Mineral storage aims to trap carbon in stable minerals, and CO2 would be

forever trapped. In this process, CO2 is reacted with (abundantly available)

metal oxides, which produces stable carbonates. This process occurs naturally

and is responsible for much of the surface limestone. However, the natural

reaction is very slow and has to be enhanced by pre-treatment of the

minerals, which is very energy intensive. The IPCC estimates that a power

plant equipped with CCS using mineral storage will need 60-180% more energy

than a power plant without CCS. Mineral sequestration

Mineral sequestration aims to trap carbon in the form of solid carbonate salts. This process occurs slowly in nature and is responsible for the deposition and accumulation of limestone (calcium carbonate) over geologic time. Carbonic acid in groundwater slowly reacts with complex silicates to dissolve calcium, magnesium, alkalis and silica and leave a residue of clay minerals. The dissolved calcium and magnesium react with bicarbonate to precipitate calcium and magnesium carbonates, a process that organisms use to make shells. When the organisms die, their shells are deposited as sediment and eventually turn into limestone. Limestones have accumulated over billions of years of geologic time and contain much of Earth's carbon. Ongoing research aims to speed up similar reactions involving alkali carbonates

One proposed reaction is that of the olivine-rich rock dunite, or its hydrated equivalent serpentinite with carbon dioxide to form the carbonate mineral magnesite, plus silica and iron oxide (magnetite).

Serpentinite sequestration is favored because of the non-toxic and stable nature of magnesium carbonate. The ideal reactions involve the magnesium endmember components of the olivine (reaction 1) or serpentine (reaction 2), the latter derived from earlier olivine by hydration and silicification (reaction 3). The presence of iron in the olivine or serpentine reduces the efficiency of sequestration, since the iron components of these minerals break down to iron oxide and silica (reaction 4).

Serpentinite reactions

Reaction 1 Mg-Olivine + Carbon dioxide → Magnesite + Silica

Mg2SiO4 + 2CO2 → 2MgCO3 + SiO2 + H2O

Reaction 2 Serpentine + carbon dioxide → Magnesite + silica + water

Mg3[Si2O5(OH)4] + 3CO2 → 3MgCO3 + 2SiO2 + 2H2O

Reaction 3 Mg-Olivine + Water + Silica → Serpentine

3Mg2SiO4 + 2SiO2 + 4H2O → 2Mg3[Si2O5(OH)4

Reaction 4 Fe-Olivine + Water → Magnetite + Silica + Hydrogen

3Fe2SiO4 + 2H2O → 2Fe3O4 + 3SiO2 + 2H2

CO2 re-use:

Making Jet fuel by scrubbing CO2 from the air would allow aviation to continue in a

low carbon economy

A potentially useful way of dealing with industrial sources of CO2 is to convert it into hydrocarbons where it can be stored or reused as fuel or to make plastics. There are a number of projects investigating this possibility. Currently, biofuels represent the other potentially carbon-neutral jet fuel available.

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

Single step methods: CO2 + H2 → methanol

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

2 Step methods: CO2 → CO → Hydrocarbons

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

The worldwide capacity of potential CO2 storage reservoirs:

Ocean and land-based sites together contain an enormous capacity for storage of CO2. The world’s oceans have by far the largest capacity for carbon storage.

Sequestration option Worldwide capacity

Ocean 1000s GtC

Deep saline formations 100s–1000s GtC

Depleted oil and gas reservoirs 100s GtC

Coal seams 10s–100s GtC

Terrestrial 10s GtC

Utilization <1 GtC/yr

Note: Worldwide total anthropogenic carbon emissions are ~7 GtC per year (1 GtC = 1 billion metric tons of carbon equivalent).

Types of Geosequestration Process: 1. Pre-combustion solvent absorption

Advanced power generation technologies are under development that can make much cleaner and more efficient use of fossil fuels such as coal. Integrated Gasification Combined Cycle (IGCC) is one such technique, converting coal to a combustible gas known as syngas (containing hydrogen, carbon monoxide and carbon dioxide) at high temperature and pressure. IGCC uses a gas turbine followed by a steam turbine to generate electricity. Solvent absorption is the current industry method for removing carbon dioxide (CO2) from syngas. Liquid chemicals are used to absorb the CO2 and then release it at an elevated temperature in another vessel.

After the gasification of the coal and various gas cleaning steps, the gas enters the absorption column. There it comes into contact with the solvent which absorbs the CO2. The other gases leave the absorption column, and the “rich” solvent containing the CO2 is then pumped to another column called a stripping column. The “rich” solvent is then heated to about 120°C, causing the CO2 to be released from the solvent. The CO2 emerges at the top of the stripper column where it is cooled, allowing the removal of water and traces of solvents. The liquid is returned to the top of the stripper column and the “lean” solvent is pumped from the bottom back to the absorber.

On the way, the hot, lean solvent passes through a heat exchanger, along with the rich solvent leaving the absorber column. This cools the lean solvent, ready for more CO2 absorption, and heats the rich solvent on its way to the stripper column. The solvent can be used over and over again to perform the separation of CO2.

2. Post Cumbustion Process

Membrane technologies:

Membranes, generally made of polymers or ceramics, can be used to effectively sieve out carbon dioxide (CO2) from gas streams. The membrane material is specifically designed to preferentiallys eparate the molecules in the mixture. The process has not yet been applied on a large scale and there are challenges related to the composition and temperature of the flue gases. Membranes are used to separate CO2 from other gases (gas separation membranes) and to allow CO2 to be absorbed from a gas stream into a solvent (membrane gas absorption). There are a range of membrane types for these processes.

Membrane Gas Absorption:

A membrane can be used with a solvent to capture the CO2. The CO2 diffuses between the pores in the membrane and is then absorbed by the solvent. The membrane maintains the surface area between gas and liquid phases. This type of membrane is useful when the CO2 has a low partial pressure, such as in flue gases, because the driving force for gas separation is small.

In the diagram above, the porous membrane allows gases to come into contact with the solvent. Only CO2 is absorbed because of the selectivity of the solvent. The membrane itself does not separate the CO2 from other gases, but rather maintains a barrier between the liquid and gas with permeability through the pores. In a traditional solvent absorption process, the liquid and the gas are together, which leads to flow problems such as foaming and channelling. The physical separation of the gas flow from the liquid flow in a membrane absorber eliminates these problems. Using a compact membrane can reduce the size of the equipment required to absorb the CO2. Research is focused on developing appropriate materials that ensure that solvent does not penetrate the membrane pores.

Solvent absorption:

Solvent absorption is currently the preferred option for removing carbon dioxide (CO2) from industrial waste gas and for purifying natural gas. It is the method involves passing the flue gas through liquid chemicals that absorb CO2 and then

release it at an elevated temperature in another vessel. The same chemical can be used over and over again to separate CO2. In post-combustion capture from power stations, the flue gas is at atmospheric pressure and contains mainly nitrogen, CO2, oxygen and water. The cooled flue gas comes into contact with the solvent in the absorber and the CO2 is absorbed into the solvent at a temperature of between 40-60°C. The other gases leave the absorber column and the “rich” solvent containing the CO2 is then pumped to another column (called a stripper or desorber) via a heat exchanger. The “rich” solvent is then heated to about 120°C, causing the CO2 to be released from the solvent. The CO2 emerges at the top of the desorber where it is cooled to remove water. The water is returned to the desorber and the “lean” solvent pumped back to the absorber. On the way, the hot, lean solvent passes through a heat exchanger, where it exchanges heat with the rich solvent leaving the absorber column.

Note: Solvents used in carbon dioxide capture are either chemical solvents or physical solvents:

Chemical solvents: With chemical solvents, the absorption primarily depends on chemical reactions between the solvent and CO2 . Post capture, heat is required to release the CO2 and regenerate the solvent.

Physical solvents: Absorption in a physical solvent relies on the solubility of CO2 in the solvent rather than a chemical reaction with the solvent. The solvent is regenerated by changing pressure or temperature. Examples: methanol, dimethyl ethers of polyethylene glycol and N - methyl - 2 - pyrrolidone (NMP).

Advantages and Disadvantages:

Advantages:

1. CO2 Storage & Enhanced Oil Recovery:

CO2 is sometimes injected into declining oil fields to increased oil recovery.

Approximately 30 to 50 million metric tonnes of CO2 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 CO2 emissions.

2. Enhanced Coal Bed Methane:

Unminable coal seams can be used to store CO2 because CO2 adsorbs to the

surface of coal. However, the technical feasibility depends on the permeability of

the coal bed. In the process of absorption the coal releases previously absorbed

methane, and the methane can be recovered (enhanced coal bed methane

recovery). The sale of the methane can be used to offset a portion of the cost of

the CO2 storage. However, burning the resultant methane would produce CO2,

which would negate some of the benefit of sequestering the original CO2.

3. Cold/Soft Drinks:

In manufacturing of soft drinks this CO2 is used.

4. CO2 Reduction:

About 80-90% CO2 emission can be cut from large CO2 emitter plants and

thus reduce the risk of Global Warming/ Cimate change.

Disadvantages:

Acidity of Ocean water:

The environmental effects of oceanic storage are generally negative, but poorly

understood. Large concentrations of CO2 kills ocean organisms, but another

problem is that dissolved CO2 would eventually equilibrate with the atmosphere, so

the storage would not be permanent. Also, as part of the CO2 reacts with the

water to form carbonic acid, H2CO3, the acidity of the ocean water increases.

1. Increased Energy consumption and Economy:

About 10%-40% more energy consumption in industry with ccs than industry

without ccs and thus also increase in economy loss. Additional energy is required for

CO2 capture, and this means that substantially more fuel has to be used, depending on the

plant type. For new supercritical pulverized coal (PC) plants using current technology, the

extra energy requirements range from 24-40%, while for natural gas combined cycle

(NGCC) plants the range is 11-22% and for coal-based gasification combined cycle (IGCC)

systems it is 14-25% [IPCC, 2005

2. Leakage problem:

Generally, the chances are rare if, occurs:

CO2 in ground water: pollution of fresh water,loss of water for drinking or

irrigational purposes.

CO2 in soil: die-off of vegetated areas,root anoxia ,microbes in soils are affected.

CO2 in atmosphere: animals, humans are affected.

(In 1986 a large leakage of naturally sequestered carbon dioxide rose from Lake Nyos in Cameroon

and asphyxiated 1,700 people. While the carbon had been sequestered naturally, some point to the

event as evidence for the potentially catastrophic effects of sequestering carbon.)

3. Unsuitable of Small sources:

This ccs method can’t be used to trap CO2 emitted from small sources such as vehicles and domestic which accounts for 24% of total emissions.

Summery:

The major merit of CCS systems is the reduction of CO2 emissions, which is

typically on the order of 90%, depending on plant type. The substantial extra

amounts of energy required for CO2 capture means that more fuel has to be

used, how much depends on the plant type. For new supercritical pulverized coal 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%, according to IPCC. Obviously, fuel use and environmental problems arising from mining and extraction of coal or gas increase accordingly. IPCC has provided estimates of air emissions from various CCS plant designs (see table here under). While CO2 is drastically reduced (though never completely captured), emissions of air pollutants increase significantly, generally due to the energy penalty of capture. Hence, the use of CCS entails some sacrifice of air quality.

Emissions to air

from plants with

or without CCS

(kg/MWh)

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.

THE REPORTS

Australia on a project to bury carbon dioxide Thursday, Apr 03, 2008— AP THE HINDU CANBERRA: Australia began pumping carbon dioxide underground on Wednesday using an experimental technology that aims to reduce greenhouse gas emissions by locking dangerous gases deep in the earth. Australia is one of only a handful of places trying the technology, and environmentalists immediately criticised the project as a token gesture that distracts from the bigger goal of getting industry to slash emissions. Officials opened a plant in southern Victoria state on Wednesday, which they said would capture and compress 1,00,000 tonne of carbon dioxide and then inject it two km underground into a depleted natural gas reservoir. The process is known a geosequestration. “The project has a very important role in demonstrating the technical and environmental feasibility of geosequestration to Australia and the world and preparing the way for its widespread application,” Peter Cook, the project’s chief executive, said in a statement. The Australian scheme was developed with federal and state government support and is much smaller than similar systems overseas. Since 1996, about one million tonne of carbon dioxide a year has been injected under the North Sea and about the same amount trapped under Algeria’s In Salah gas

fields for the past two years. The process uses technology similar to that used at about 144 sites in the U.S. where carbon dioxide is injected underground to help recover oil reserves.

Carbon Capture Has A Sparkling Future, New Findings Show ScienceDaily (Apr. 2, 2009) : New research shows that for millions of years carbon dioxide has been stored safely and naturally in underground water in gas fields saturated with the greenhouse gas. The findings – published in Nature April 1 – bring carbon capture and storage a step closer.

Politicians are committed to cutting levels of atmospheric carbon dioxide to slow climate change. Carbon capture and storage is one approach to cut levels of the gas until cleaner energy sources are developed. But the risks around the long-term storage of millions of cubic metres of carbon dioxide in depleted gas and oil fields has met with some concern, not least because of the possibility of some of the gas escaping and being released back to the atmosphere. Until now, researchers couldn't be sure how the gas would be securely trapped underground. Naturally-occurring carbon dioxide can be trapped in two ways. The gas can dissolve in underground water – like bottled sparkling water. It can also react with minerals in rock to form new carbonate minerals, essentially locking away the carbon dioxide underground. Previous research in this area used computer models to simulate the injection of carbon dioxide into underground reservoirs in gas or oil fields to work out where the gas is likely to be stored. Some models predict that the carbon dioxide would react with rock minerals to form new carbonate minerals, while others suggest that the gas dissolves into the water. Real studies to support either of these predictions have, until now, been missing.

To find out exactly how the carbon dioxide is stored in natural gas fields, an international team of researchers - led by the University of Manchester - uniquely combined two specialised techniques. They measured the ratios of the stable isotopes of carbon dioxide and noble gases like helium and neon in nine gas fields in North America, China and Europe. These gas fields were naturally filled with carbon dioxide thousands or millions of years ago. They found that underground water is the major carbon dioxide sink in these gas fields and has been for millions of years. Dr. Stuart Gilfillan, the lead researcher who completed the project at the University of Edinburgh said: "We've turned the old technique of using computer models on its head and looked at natural carbon dioxide gas fields which have trapped carbon dioxide for a very long time." "By combining two techniques, we've been able to identify exactly where the carbon dioxide is being stored for the first time. We already know that oil and gas have been stored safely in oil and gas fields over millions of years. Our study clearly shows that the carbon dioxide has been stored naturally and safely in underground water in these fields." Professor Chris Ballentine of the University of Manchester, the project director, said: "The universities of Manchester and Toronto are international leaders in different aspects of gas tracing. By combining our expertise we have been able to invent a new way of looking at carbon dioxide fields. This new approach will also be essential for monitoring and tracing where carbon dioxide captured from coal-fired power stations goes when we inject it underground – this is critical for future safety verification." Professor Barbara Sherwood Lollar of the University of Toronto and co-author of the study hopes the new data can be fed into future computer models to make modelling underground carbon capture and storage more accurate. The work was funded by the Natural Environment Research Council and the Natural Sciences and Engineering Research Council of Canada.

ENERGY DAILY -the power of earth and beyond

CO2 Burial Could Help Extract Methane From

Old Coal Mines by Staff Writers Pittsburgh PA (SPX) Jun 27, 2007

Deep coal seams that are not commercially viable for coal production could be used for permanent underground storage of carbon dioxide (CO2) generated by human activities, thus avoiding atmospheric release, according to two studies published in Inderscience's International Journal of Environment and Pollution. An added benefit of storing CO2 in this way is that additional useful methane will be displaced from the coal beds.

Finding ways to store (sequester) the greenhouse gas CO2, indefinitely, is one approach being investigated in efforts to reduce atmospheric CO2 levels and so help combat climate change. CO2 might be pumped into oil wells to extract the last few drops of oil or be placed deep underground in brine aquifers or unmineable coal seams.

Researchers at the U.S. Department of Energy's National Energy Technology Laboratory have carried out initial investigations into the potential environmental impacts of CO2 sequestration in unmineable coal seams. The research team collected 2000 coal samples from 250 coal beds across 17 states. Some sources of coal harbor vast quantities of methane, or natural gas. Low-volatile rank coals, for instance, average the highest methane content, 13 cubic meters per tonne of coal.

The researchers found that the depth from which a coal sample is taken reflects the average methane content, with much deeper seams containing less methane.

However, the study provides only a preliminary assessment of the possibilities. The key question is whether methane can be tapped from the unmineable coal seams

The research team has also investigated some of the possible side-effects of sequestering CO2 in coal mines. They tested a high volatility bituminous coal with produced water and gaseous carbon dioxide at 40 Celsius and 50 times atmospheric pressure. They used microscopes and X-ray diffraction to analyze the coal after the reaction was complete. They found that some toxic metals originally trapped in the coal were released by the process, contaminating the water used in the reaction.

and replaced permanently with huge quantities of carbon dioxide; if so, such coal seams could represent a vast sink for CO2 produced by industry. The researchers point out that worldwide, there are almost 3 trillions tonnes of storage capacity for CO2 in such deep coal seams.

To replicate actual geological conditions, NETL has built a Geological Sequestration Core Flow Laboratory (GSCFL). A wide variety of CO2 injection experiments in coal and other rock cores (e.g., sandstone) are being performed under in situ conditions of triaxial stress, pore pressure, and temperature.

Preliminary results obtained from Pittsburgh No. 8 coal indicate that the permeability decreases (from micro-darcies to nano-darcies or extremely low flow properties) with increasing CO2 pressure, with an increase in strain associated with the triaxial confining pressures restricting the ability of the coal to swell.

The already existing low pore volume of the coal is decreased, reducing the flow of CO2, measured as permeability. This is a potential problem that will have to be overcome if coal seam sequestration is to be widely used.

The research team has also investigated some of the possible side-effects of sequestering CO2 in coal mines. They tested a high volatility bituminous coal with produced water and gaseous carbon dioxide at 40 Celsius and 50 times atmospheric pressure. They used microscopes and X-ray diffraction to analyze the coal after the reaction was complete. They found that some toxic metals originally trapped in the coal were released by the process, contaminating the water used in the reaction.

"Changes in water chemistry and the potential for mobilizing toxic trace elements from coal beds are potentially important factors to be considered when evaluating deep, unmineable coal seams for CO2 sequestration, though it is also possible that, considering the depth of the injection, that such effects might be harmless" the researchers say.

"The concentrations of beryllium, cadmium, mercury, and zinc increased significantly, though both beryllium and mercury remained below drinking water standards." However, toxic arsenic, molybdenum, lead, antimony, selenium, titanium, thallium, vanadium, and iodine were not detected in the water, although they were present in the original coal samples.

Conclusions:

No doubt, the CO2 Geo-sequestration is very efficient technology to reduce the

risk of CO2 emission by large power plants and industries which is major

contributory gas in Global Warming. Its enviromental backlashes is negligible than

its utilisation such as in enhanced oil recovey, methane adsorption, manufacturing

of soft drinks etc. About 80-90% CO2 emmision is reduced however, the

consumption of electricity increased by 10-40% and thus the cost increased by 20-

30% which should be neglected taking the environmental problem as global warming

in point of view.

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