239807518 ccs-report-for-print

A seminar Report on “CO2 Capture and Storage System”
Get Homework/Assignment
Done
Homeworkping.com
Homework Help
https://www.homeworkping.com/
Research Paper help
Online Tutoring
click here for freelancing tutoring sites
Abstract
Approximately one third of all CO2 emissions due to human activity come from
fossil fuels used for generating electricity, with each power plant capable of emitting
several million tones of CO2 annually. A variety of other industrial processes also emit
large amounts of CO2 from each plant, for example oil refineries, cement works, and iron
and steel production. These emissions could be reduced substantially, without major
changes to the basic process, by capturing and storing the CO2. Other sources of
emissions, such as transport and domestic buildings, cannot be tackled in the same way
because of the large number of small sources of CO2.
Carbon capture and storage (CCS) is an approach to minimize global warming
by capturing carbon dioxide (CO2) from large point sources such as fossil fuel power
plants and storing it instead of releasing it into the atmosphere CCS applied to a modern
conventional power plant could reduce CO2 emissions to the atmosphere by
approximately 80-90% compared to a plant without CCS.
7th
Semester Dept. of Mechanical Engineering BCET Balasore
1

1. INTRODUCTION
Carbon dioxide (CO2) is a greenhouse gas that occurs naturally in the atmosphere.
Human activities are increasing the concentration of CO2 in the atmosphere thus
contributing to Earth’s global warming. CO2 is emitted when fuel is burnt – be it in large
power plants, in car engines, or in heating systems. It can also be emitted by some other
industrial processes, for instance when resources are extracted and processed, or when
forests are burnt.Currently, 30 Gt per year of CO2 is emitted due to human activities.The
increase in concentration of carbon in the past two hundred years is shown in the Fig 1.1
7th
2

Fig 1.1 Increase in concentration of CO2 in past two centuries
Fig 1.2 Increase in global temperature in past 200 years.
One possible option for reducing CO2 is to store it underground. This technique is
called Carbon dioxide Capture and Storage (CCS).
In Carbon capture and storage (CCS), carbon dioxide (CO2) is capured from large
point sources (A point source of pollution is a single identifiable localized source of air,
water, thermal, noise or light pollution).such as fossil fuel power plants and storing it
instead of releasing it into the atmosphere. Although CO2 has been injected into
geological formations for various purposes, the long term storage of CO2 is a relatively
untried.
CCS applied to a modern conventional power plant could reduce CO2 emissions to
the atmosphere by approximately 80-90% compared to a plant without CCS.
7th
3

Fig 1.3 Power plants with and with out CCS.
The section2 presents the general framework for the assessment together with a brief
overview of CCS systems. Section 3 then describes the major sources of CO2, a step
needed to assess the feasibility of CCS on a global scale. Technological options for CO2
capture are then discussed in Section 4, while Section 5 focuses on methods of CO2
transport. Following this, each of the storage options is addressed on section 6. Section
6.1 focuses on geological storage, Section 6.2 on ocean storage, and Section 6.3 on
mineral carbonation of CO2 section 7 discus the risk of CO2 leakage, The overall costs
and economic potential of CCS are then discussed in Section 8, followed by the
conclusion in Section 9.
2. CARBON DIOXIDE CAPTURE AND STORAGE
One technique that could limit CO2 emissions from human activities into the
atmosphere is Carbon dioxide Capture and Storage (CCS). It involves collecting, at its
source, the CO2 that is produced by power plants or industrial facilities and storing it away
for a long time in underground layers, in the oceans, or in other materials
The process involves three main steps:
1. capturing CO2, at its source, by separating it from other gases produced by an
industrial process
2. transporting the captured CO2 to a suitable storage location (typically in
compressed form)
7th
4

3. storing the CO2 away from the atmosphere for a long period of time, for instance
in underground geological formations, in the deep ocean, or within certain mineral
compounds.
Fig 2.1 The three main components of the CCS process
Fig 2.2 The Esbjerg Power Station, a CO2 capture site in Denmark
3. THE CHARACTERISTICS OF CCS
Capture of CO2 can be applied to large point sources. The CO2 would then be
compressed and transported for storage in geological formations, in the ocean, in mineral
carbonates2, or for use in industrial processes. Large point sources of CO2 include large
fossil fuel or biomass energy facilities, major CO2-emitting industries, natural gas
production, synthetic fuel plants and fossil fuel-based hydrogen production plants (see
Table 3.1).
Potential technical storage methods are: geological storage (in geological formations,
such as oil and gas fields, unminable coal beds and deep saline formations3), ocean
storage (direct release into the ocean water column or onto the deep seafloor) and
7th
5

industrial fixation of CO2 into inorganic carbonates. This report also discusses industrial
uses of CO2, but this is not expected to contribute much to the reduction of
CO2emissions.
Table 3.1. Profile by process or industrial activity of worldwide large stationary CO2 sources with emissions of more
than 0.1 million tonnes of CO2 (MtCO2) per year.
4. SOURCES OF CO2 EMISSIONS SUITABLE FOR CAPTURE AND
STORAGE
Several factors determine whether carbon dioxide capture is a viable option for a
particular emission source:
• The size of the emission source,
• Whether it is stationary or mobile,
• How near it is to potential storage sites, and
• How concentrated its co2 emissions are.
Carbon dioxide could be captured from a large stationary emission sources such as
a power plants or industrial facilities that produce large amounts of carbon dioxide. If
7th
6

such facilities are located near potential storage sites, for example suitable geological
formations, they are possible candidates for the early implementation of CO2 capture and
storage (CCS).
Small or mobile emission sources in homes, businesses or transportation are not
being considered at this stage because they are not suitable for capture and storage.
Fig 4.1 The Gibson coal power plant, a good example of a large stationary source.
Process Number of sources Emissions (MtCO2 yr-1
)
Fossil fuels Power 4,942 10,539
Cement production 1,175 932
Refineries 638 798
Iron and steel industry 269 646
Petrochemical industry 470 379
Oil and gas processing N/A 50
Other sources 90 33
Biomass
Bioethanol and bioenergy 303 91
Total 7,887 13,466
Table 4.1 Profile by process or industrial activity of worldwide large stationary CO2 sources
with emissions of more than 0.1 MtCO2 per year.
In 2000, close to 60% of the CO2 emissions due to the use of fossil fuels were
produced by large stationary emission sources, such as power plants and oil and gas
extraction or processing industries (see Table 3.1).
Four major clusters of emissions from such stationary emission sources are: the
Midwest and eastern USA, the northwestern part of Europe, the eastern coast of China
and the Indian subcontinent (see Figure 4.2).
7th
7

Fig 4.2 Global Distribution of large CO2 sources
Many stationary emission sources lie either directly above, or within reasonable distance
(less than 300km) from areas with potential for geological storage (see Fig 4.2 & Fig 4.3)
Fig 4.3 Possible storage sites
5. CO2 CAPTURE
The purpose of CO2 capture is to produce a concentrated stream of CO2 at high
pressure that can readily be transported to a storage site. Although, in principle, the entire
gas stream containing low concentrations of CO2 could be transported and injected
underground, energy costs and other associated costs generally make this approach
7th
8

impractical. It is therefore necessary to produce a nearly pure CO2 stream for transport
and storage. Applications separating CO2 in large industrial plants, including natural gas
treatment plants and ammonia production facilities, are already in operation today.
Currently, CO2 is typically removed to purify other industrial gas streams. Removal has
been used for storage purposes in only a few cases; in most cases, the CO2 is emitted to
the atmosphere. Capture processes also have been used to obtain commercially useful
amounts of CO2 from flue gas streams generated by the combustion of coal or natural gas.
However, there have been no applications of CO2 capture at large (e.g., 500 MW) power
plants.
Three systems are available for power plants: post-combustion, pre-combustion, and
oxy fuel combustion systems. The captured CO2 must then be purified and compressed
for transport and storage.
Fig 5.1 CO2 capture process.
5.1 Post-Combustion Systems
This system separate CO2 from the flue gases produced by the combustion of the
primary fuel in air. These systems normally use a liquid solvent to capture the small
fraction of CO2 (typically 3–15% by volume) present in a flue gas stream in which the
main constituent is nitrogen (from air). For a modern pulverized coal (PC) power plant or
7th
9

a natural gas combined cycle (NGCC) power plant, current post-combustion capture
systems would typically employ an organic solvent such as monoethanolamine (MEA).
Fig 5.2 Gas turbine combine cycle with post-combustion
5.2 Pre-Combustion Systems
In this process the primary fuel in a reactor with steam and air or oxygen to produce a
mixture consisting mainly of carbon monoxide and hydrogen (“synthesis gas”).
Additional hydrogen, together with CO2, is produced by reacting the carbon monoxide
with steam in a second reactor (a “shift reactor”). The resulting mixture of hydrogen and
CO2 can then be separated into a CO2 gas stream, and a stream of hydrogen. If the CO2 is
stored, the hydrogen is a carbon-free energy carrier that can be combusted to generate
power and/or heat. Although it is costly than post-combustion systems, the high
concentrations of CO2 produced by the shift reactor (typically 15 to 60% by volume on a
dry basis) and the high pressures often encountered in these applications are more
favorable for CO2 separation.
7th
10

Fig 5.3 Pre-combustion capture of CO2
5.3 Oxyfuel Combustion Systems
This system use oxygen instead of air for combustion of the primary fuel to
produce a flue gas that is mainly water vapour and CO2. This results in a flue gas with
high CO2 concentrations (greater than 80% by volume). The water vapour is then
removed by cooling and compressing the gas stream. Oxyfuel combustion requires the
upstream separation of oxygen from air, with a purity of 95–99% oxygen assumed in
most current designs. Further treatment of the flue gas may be needed to remove air
pollutants and non- condensed gases (such as nitrogen) from the flue gas before the CO2
is sent to storage. As a method of CO2 capture in boilers, oxyfuel combustion systems are
in the demonstration phase. Oxyfuel systems are also being studied in gas turbine
Current post-combustion and pre-combustion systems for power plants could capture
85–95% of the CO2 that is produced. Higher capture efficiencies are possible, although
separation devices become considerably larger, more energy intensive and more costly.
Capture and compression need roughly 10–40% more energy than the equivalent plant
without capture, depending on the type of system. Due to the associated CO2 emissions,
the net amount of CO2 captured is approximately 80–90%. Oxyfuel combustion systems
are, in principle, able to capture nearly all of the CO2 produced. However, the need for
additional gas treatment systems to remove pollutants such as sulphur and nitrogen oxides
lowers the level of CO2 captured to slightly more than 90%.
7th
11

6. CO2 TRANSPORTATION
After capture, the CO2 must be transported to suitable storage sites. Today Pipelines
operate as a mature market technology and are the most common method for transporting
CO2. Gaseous CO2 is typically compressed to a pressure above 8 MPa in order to avoid
two-phase flow regimes and increase the density of the CO2, thereby making it easier and
less costly to transport. CO2 also can be transported as a liquid in ships, road or rail
tankers that carry CO2 in insulated tanks at a temperature well below ambient, and at
much lower pressures.
The first long-distance CO2 pipeline came into operation in the early 1970s. In the
United States, over 2,500 km of pipeline transports more than 40 MtCO2 per year from
natural and anthropogenic sources, and it is mainly used for EOR. These pipelines operate
in the ‘dense phase’ mode (in which there is a continuous progression from gas to liquid,
without a distinct phase change), and at ambient temperature and high pressure. In most
of these pipelines, the flow is driven by compressors at the upstream end, although some
pipelines have intermediate (booster) compressor stations.
In some situations or locations, transport of CO2 by ship may be economically more
attractive, particularly when the CO2 has to be moved over large distances or overseas.
Liquefied petroleum gases (LPG, principally propane and butane) are transported on a
large commercial scale by marine tankers. CO2 can be transported by ship in much the
same way (typically at 0.7 MPa pressure), but this currently takes place on a small scale
because of limited demand. The properties of liquefied CO2 are similar to those of LPG,
and the technology could be scaled up to large CO2 carriers if a demand for such systems
were to materialize.
Road and rail tankers also are technically feasible options. These systems transport
CO2 at a temperature of -20ºC and at 2 MPa pressure. However, they are uneconomical
compared to pipelines and ships, except on a very small scale, and are unlikely to be
relevant to large-scale CCS.
Fig 6.1 An LPG tanker-CO2 can be transported in the similar way.
7th
12

7. CO2 STORAGE (SEQUESTRATION)
Various forms have been conceived for permanent storage of CO2. These forms
include gaseous storage in various deep geological formations (including saline
formations and exhausted gas fields), liquid storage in the ocean, and solid storage by
reaction of CO2 with metal oxides to produce stable carbonates.
7.1 Geological Storage.
Also known as geo-sequestration, this method involves injecting carbon dioxide,
directly into underground geological formations. Geological formations are currently
considered the most promising sequestration sites, and these are estimated to have a
storage capacity of at least 2000 Gt CO2 (currently, 30 Gt per year of CO2 is emitted due
to human activities). Oil fields, gas fields, saline formations, unminable coal seams, and
saline-filled basalt formations have been suggested as storage sites. Various physical
(e.g., highly impermeable caprock) and geochemical trapping mechanisms would prevent
the CO2 from escaping to the surface. CO2 is sometimes injected into declining oil fields
to increase oil recovery (enhanced oil recovery).CO2 storage in hydrocarbon reservoirs or
deep saline formations is generally expected to take place at depths below 800 m, where
the ambient pressures and temperatures will usually result in CO2 being in a liquid or
supercritical state. Under these conditions, the density of CO2 will range from 50 to 80%
of the density of water. This is close to the density of some crude oils, resulting in
buoyant forces that tend to drive CO2 upwards. Fig7.1.1 shows some of the methods used
in geological storage.
This option is attractive because the storage costs may be partly offset by the sale of
additional oil that is recovered
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.
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 oil fields.
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.
7th
13

Fig 7.1.1 Geological storage options.
Reservoir type Lower estimate of
storage capacity (GtCO2)
Upper estimate of
storage capacity (GtCO2)
Oil and gas fields 675a
900a
Unminable coal
seams (ECBM)
3-15 200
Deep saline
formations
1,000 Uncertain, but
possibly 104
Table 7.1.1 Storage capacity for several geological storage options.
7th
14

8. METHODOLOGICAL FRAMEWORK FOR CO2 CAPTURE AND STORAGE
SYSTEMS
8.1 Greenhouse Gas Inventories
The two main options for including CCS in national greenhouse gas inventories have
been identified and analysed using the current methodological framework for total chain
from capture to storage (geological and ocean storage). These options are: • Source
reduction: To evaluate the CCS systems as mitigation options to reduce emissions to the
atmosphere;
Figure 8. 1 Simplified flow diagram of possible CO2 emission sources during CCS
Sink enhancement: To evaluate the CCS systems using an analogy with the treatment
made to CO2 removals by sinks in the sector Land Use, Land-Use Change and Forestry.
A balance is made of the CO2 emissions and removals to obtain the net emission or
removal. In this option, removals by sinks are related to CO2 storage. In both options,
estimation methodologies could be developed to cover most of the emissions in the CCS
system (see Figure 9.1), and reporting could use the current framework for preparation of
national greenhouse gas inventories. In the first option, reduced emissions could be
reported in the category where capture takes place. For instance, capture in power plants
could be reported using lower emission factors than for plants without CCS. But this
could reduce transparency of reporting and make review of the overall impact on
emissions more difficult, especially if the capture process and emissions from
transportation and storage are not linked. This would be emphasized where transportation
and storage includes captured CO2 from many sources, or when these take place across
national borders. An alternative would be to track CO2 flows through the entire capture
and storage system making transparent how much CO2 was produced, how much was
emitted to the atmosphere at each process stage, and how much CO2 was transferred to
storage.
7th
15

The second option is to report the impact of the CCS system as a sink. For instance,
reporting of capture in power plants would not alter the emissions from the combustion
process but the stored amount of CO2 would be reported as a removal in the inventory.
Application of the second option would require adoption of new definitions not available
in the UNFCCC or in the current methodological framework for the preparation of
inventories. UNFCCC (1992) defines a sink as ‘any process, activity or mechanism which
removes a greenhouse gas, an aerosol, or a precursor of a greenhouse gas from the
atmosphere’. Although ‘removal’ was not included explicitly in the UNFCCC definitions,
it appears associated with the ‘sink’ concept. CCS11 systems do not meet the UNFCCC
definition for a sink, but given that the definition was agreed without having CCS systems
in mind, it is likely that this obstacle could be solved (Torvanger et al., 200 ). General
issues of relevance to CCS systems include system boundaries (sectoral, spatial and
temporal) and these will vary in importance with the specific system and phases of the
system. The basic methodological approaches for system components, together with the
status of the methods and availability of data for these are discussed below. Mineral
carbonation and industrial use of CO2 are addressed separately.
8.2 Ocean Storage
A potential CO2 storage option is to inject captured CO2 directly into the
deep ocean (at depths greater than 1,000 m), where most of it would be isolated from the
atmosphere for centuries. This can be achieved by transporting CO2 via pipelines or ships
to an ocean storage site, where it is injected into the water column of the ocean or at the
sea floor. The dissolved and dispersed CO2 would subsequently become part of the global
carbon cycle. Fig 8.2 shows some of the main methods that could be employed. Ocean
storage has not yet been deployed or demonstrated at a pilot scale, and is still in the
research phase. However, there have been small- scale field experiments and 25 years of
theoretical, laboratory and modeling studies of intentional ocean storage of CO2.
7th
16

Fig 8.2 Ocean storage methods.
CO2 injection, however, can harm marine organisms near the injection point. It is
furthermore expected that injecting large amounts would gradually affect the whole
ocean. Because of its environmental implications, CO2 storage in oceans is generally no
longer considered as an acceptable option
8.3 Mineral Storage
Through chemical reactions with some naturally occurring minerals, CO2 is
converted into a solid form through a process called mineral carbonation and stored
virtually permanently. This is a process which occurs naturally, although very slowly.
These chemical reactions can be accelerated and used industrially to artificially store
CO2 in minerals. However, the large amounts of energy and mined minerals needed
makes this option less cost effective.
Earthen Oxide Percent of Crust Carbonate Enthalpy change
(kJ/mol)
SiO2 59.71
Al2O3 15.41
CaO 4.90 CaCO3 -179
MgO 4.36 MgCO3 -117
Na2O 3.55 Na2CO3
FeO 3.52 FeCO3
K2O 2.80 K2CO3
Fe2O3 2.63 FeCO3
21.76 All Carbonates
Table 8.1 Principal metal oxides of Earth's Crust. Theoretically up to 22% of this
mineral mass is able to form carbonates.
7th
17

9. RISK OF LEAKAGE
The risks due to leakage from storage of CO2 in geological reservoirs fall into two
broad categories: global risks and local risks. Global risks involve the release of CO2 that
may contribute significantly to climate change if some fraction leaks from the storage
formation to the atmosphere. In addition, if CO2 leaks out of a storage formation, local
hazards may exist for humans, ecosystems and groundwater. These are the local risks.
Fig 9.1 Geological leakage routes
10 THE CURRENT STATUS OF CCS TECHNOLOGY
There are different types of CO2 capture systems: postcombustion, pre-combustion
and oxyfuel combustion. The concentration of CO2 in the gas stream, the pressure of the
gas stream and the fuel type (solid or gas) are important factors in selecting the capture
system. Post-combustion capture of CO2 in power plants is economically feasible under
specific conditions5. It is used to capture CO2 from part of the flue gases from a number
of existing power plants. Separation of CO2 in the natural gas processing industry, which
uses similar technology, operates in a mature market6.
The technology required for pre-combustion capture is widely applied in fertilizer
manufacturing and in hydrogen production. Although the initial fuel conversion steps of
pre-combustion are more elaborate and costly, the higher concentrations of CO2 in the
7th
18

gas stream and the higher pressure make the separation easier. Oxyfuel combustion is in
the demonstration phase7 and uses high purity oxygen.
This results in high CO2 concentrations in the gas stream and, hence, in easier
separation of CO2 and in increased energy requirements in the separation of oxygen from
air.
Pipelines are preferred for transporting large amounts of CO2 for distances up to
around 1,000 km. For amounts smaller than a few million tones of CO2 per year or for
larger distances overseas, the use of ships, where applicable, could be economically more
attractive. Pipeline transport of CO2 operates as a mature market technology (in the USA,
over 2,500 km of pipelines transport more than 40 MtCO2 per year). In most gas
pipelines, compressors at the upstream end drive the flow, but some pipelines need
intermediate compressor stations.
Dry CO2 is not corrosive to pipelines, even if the CO2 contains contaminants. Where
the CO2 contains moisture, it is removed from the CO2 stream to prevent corrosion and
to avoid the costs of constructing pipelines of corrosion-
Figure 10.1 Schematic representations of capture systems.
7th
19

11. THE LOCAL HEALTH, SAFETY AND ENVIRONMENT RISKS OF CCS
The local risks24 associated with CO2 pipeline transport could be similar to or lower
than those posed by hydrocarbon pipelines already in operation. For existing CO2
pipelines, mostly in areas of low population density, accident numbers reported per
kilometre pipeline are very low and are comparable to those for hydrocarbon pipelines. A
sudden and large release of CO2 would pose immediate dangers to human life and health,
if there were exposure to concentrations of CO2 greater than 7–10% by volume in air.
Pipeline transport of CO2 through populated areas requires attention to route selection,
overpressure protection, leak detection and other design factors. No major obstacles to
pipeline design for CCS are foreseen.
With appropriate site selection based on available subsurface information, a
monitoring programme to detect problems, a regulatory system and the appropriate use of
remediation methods to stop or control CO2 releases if they arise, the local health, safety
and environment risks of geological storage would be comparable to the risks of current
activities such as natural gas storage, EOR and deep underground disposal of acid gas.
Natural CO2 reservoirs contribute to the understanding of the behaviour of CO2
underground. Features of storage sites with a low probability of leakage include highly
impermeable caprocks, geological stability, absence of leakage paths and effective
trapping mechanisms. There are two different types of leakage scenarios: (1) abrupt
leakage, through injection well failure or leakage up an abandoned well, and (2) gradual
leakage, through undetected faults, fractures or wells. Impacts of elevated CO2
concentrations in the shallow subsurface could include lethal effects on plants and subsoil
animals and the contamination of groundwater. High fluxes in conjunction with stable
atmospheric conditions could lead to local high CO2 concentrations in the air that could
harm animals or people. Pressure build-up caused by CO2 injection could trigger small
seismic events.
12. THE LEGAL AND REGULATORY ISSUES FOR IMPLEMENTING CO
STORAGE
1. Some regulations for operations in the subsurface do exist that may be relevant or,
in some cases, directly applicable to geological storage, but few countries have
specifically developed legal or regulatory frameworks for long-term CO2 storage.
Existing laws and regulations regarding inter alia mining, oil and gas operations, pollution
control, waste disposal, drinking water, treatment of high-pressure gases and subsurface
property rights may be relevant to geological CO2 storage. Long-term liability issues
associated with the leakage of CO2 to the atmosphere and local environmental impacts
are generally unresolved. Some States take on longterm responsibility in situations
comparable to CO2 storage, such as underground mining operations.
2. No formal interpretations so far have been agreed upon with respect to whether or
under what conditions CO2 injection into the geological sub-seabed or the ocean is
compatible. There are currently several treaties (notably the London26 and OSPAR27
7th
20

Conventions) that potentially apply to the injection of CO2 into the geological sub-seabed
or the ocean. All of these treaties have been drafted without specific consideration
of CO2 storage.
13. THE IMPLICATIONS OF CCS FOR EMISSION INVENTORIES AND
ACCOUNTING
The current IPCC Guidelines2 do not include methods specific to estimating
emissions associated with CCS. The general guidance provided by the IPCC can be
applied to CCS. A few countries currently do so, in combination with their national
methods for estimating emissions. The IPCC guidelines themselves do not yet provide
specific methods for estimating emissions associated with CCS. These are expected to be
provided in the 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Specific
methods may be required for the net capture and storage of CO2, physical leakage,
fugitive emissions and negative emissions associated with biomass applications of CCS
systems.
The few current CCS projects all involve geological storage, and there is therefore
limited experience with the monitoring, verification and reporting of actual physical
leakage rates and associated uncertainties. Several techniques are available or under
development for monitoring and verification of CO2 emissions from CCS, but these vary
in applicability, site specificity, detection limits and uncertainties.
CO2 might be captured in one country and stored in another with different
commitments. Issues associated with accounting for cross-border storage are not unique
to CCS. Rules and methods for accounting may have to be adjusted accordingly. Possible
physical leakage from a storage site in the future would have to be accounted.
14 THE GAPS IN KNOWLEDGE
There are gaps in currently available knowledge regarding some aspects of CCS.
Increasing knowledge and experience would reduce uncertainties and thus facilitate
decision-making with respect to the deployment of CCS for climate change mitigation.
15 APPROACHES AND TECHNOLOGIES FOR MONITORING
ENVIRONMENTAL EFFECTS
Techniques now being used for field experiments could be used to monitor some near
field consequences of direct CO2 injection. For example, researchers (Barry et al., 2004,
2005; Carman et al., 2004; Thistle et al., 2005) have been developing experimental means
for observing the consequences of elevated CO2 on organisms in the deep ocean.
However, such experiments and studies typically look for evidence of acute toxicity in a
narrow range of species (Sato, 2004; Caulfield et al., 1997; Adams et al., 1997; Tamburri
et al., 2000). Sub-lethal effects have been studied by Kurihara et al. (2004). Process
studies, surveys of biogeochemical tracers, and ocean bottom studies could be used to
evaluate changes in ecosystem structure and dynamics both before and after an injection.
It is less clear how best to monitor the health of broad reaches of the ocean interior
7th
21

Ongoing long-term surveys of biogeochemical tracers and deep-sea biota could help to
detect long-term changes in deep-sea ecology.
16 ENVIRONMENTAL IMPACTS, RISKS, AND RISK MANAGEMENT
Overall, there is limited knowledge of deep-sea population and community structure
and of deep-sea ecological interactions. Thus the sensitivities of deep ocean ecosystems
to intentional carbon storage and the effects on possibly unidentified goods and services
that they may provide remain largely unknown. Most ocean storage proposals seek to
minimize the volume of water with high CO2 concentrations either by diluting the CO2 in
a large volume of water or by isolating the CO2 in a small volume (e.g., in CO2 lakes).
Nevertheless, if deployed widely, CO2 injection strategies ultimately will produce large
volumes of water with somewhat elevated CO2 concentrations (Figure 6.15). Because
large amounts of relatively pure CO2 have never been introduced to the deep ocean in a
controlled experiment, conclusions about environmental risk must be based primarily on
laboratory and small-scale in-situ experiments and extrapolation from these experiments
using conceptual and mathematical models. Natural analogues (Box 6.5) can be relevant,
but differ significantly from proposed ocean engineering projects. Compared to the
surface, most of the deep sea is stable and varies little in its physiochemical factors over
time. The process of evolutionary selection has probably eliminated individuals apt to
endure environmental perturbation. As a result, deep-sea organisms may be more
sensitive to environmental disturbance than their shallow water cousins (Shirayama,
1997). Ocean storage would occur deep in the ocean where there is virtually no light and
photosynthesizing organisms are lacking, thus the following discussion primarily
addresses CO2 effects on heterotrophic organisms, mostly animals. The diverse fauna that
lives in the waters and sediments of the deep ocean can be affected by ocean CO2
storage, leading to change in ecosystem composition and functioning. Thus, the effects of
CO2 need to be identified at the level of both the individual (physiological) and the
ecosystem.
Introduction of CO2 into the ocean either directly into sea water or as a lake on the
sea floor would result in changes in dissolved CO2 near to and down current from a
discharge point. Dissolving CO2 in sea water increases the partial pressure of CO2
(pCO2, expressed as a ppm fraction of atmospheric pressure, equivalent to µatm), causes
decreased pH (more acidic) and decreased CO3 2– concentrations (less saturated). This
can lead to dissolution of CaCO3 in sediments or in shells of organisms. Bicarbonate
(HCO3 –) is then produced from carbonate (CO3 2–). The spatial extent of the waters
with increased CO2 content and decreased pH will depend on the amount of CO2
released and the technology and approach used to introduce that CO2 into the ocean.
Table shows the amount of sea water needed to dilute each tonne of CO2 to a specified
.pH reduction. Further dilution would reduce the fraction of ocean at one .pH
Photosynthesis produces organic matter in the ocean almost exclusively in the upper 200
m where there is both light and nutrients (e.g., PO4, NO3, NH4 +, Fe). Photosynthesis
forms the base of a marine food chain that recycles much of the carbon and nutrients in
the upper ocean. Some of this organic matter ultimately sinks to the deep ocean as
particles and some of it is mixed into the deep ocean as dissolved organic matter. The flux
of organic matter from the surface ocean provides most of the energy and nutrients to
support the heterotrophic ecosystems of the deep ocean (Gage and Tyler, 1991). With the
exception of the oxygen minimum zone and near volcanic CO2 vents, most organisms
living in the deep ocean live in low and more or less constant CO2 levels.
7th
22

table : Relationships between .pH, changes in pCO2, and dissolved inorganic carbon concentration calculated for mean
deep-sea conditions.
17. COST OF CO2 CAPTURE AND STOREGE OPERATIONS
CCS applied to a modern conventional power plant could reduce CO2 emissions to
the atmosphere by approximately 80-90% compared to a plant without CCS. Capturing
and compressing CO2 requires much energy and would increase the fuel needs of a coal-
fired plant with CCS by about 25%. These and other system costs are estimated to
increase the cost of energy from a new power plant with CCS by 21-91%.
Natural
gas combined
cycle
Pulve
rized 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
With capture
and Enhanced oil
recovery
0.04 - 0.07 0.05 -
0.08
0.04 - 0.08
Table 17.1 Costs of energy with and without CCS (2002 US$ per kWh)
7th
23

18 THE FUTURE OF CO2 CAPTURE AND STORAGE
• CO2 capture and storage is technologically feasible and could play a significant
role in reducing greenhouse gas emissions over the course of this century. But
many issues still need to be resolved before it can be deployed on a large scale.
• Full-scale projects in the electricity sector are needed to build knowledge and
experience. More studies are required to analyse and reduce the costs and to
evaluate the suitability of potential geological storage sites. Also, pilot scale
experiments on mineral carbonation are needed.
• An adequate legal and regulatory environment also needs to be created, and
barriers to deployment in developing countries need to be addressed.
• If knowledge gaps are filled and various conditions are met, CO2 capture and
storage systems could be deployed on a large scale within a few decades, as long
as policies substantially limiting greenhouse gas emissions are put into place.
• The scientific consensus views carbon capture and storage as one of the important
options for reducing CO2 emissions. If it were deployed, the cost of stabilizing the
concentration of greenhouse gases in the atmosphere would be reduced by 30% or
more.
7th
24

19 CONCLUSION
Large reductions in emissions of CO2 to the atmosphere are likely to be needed
to avoid major climate change. Capture and storage ofCO2, in combination with other
CO2 abatement techniques, could enable these large reductions to be achieved with least
impact on the global energy infrastructure and the economy. Capture and storage is
particularly well suited to use in central power generation and many energy-intensive
industrial processes. CO2 capture and storage technology also provides a means of
introducing hydrogen as an energy carrier for distributed and mobile energy users.
For power stations, the cost of capture and storage is about $50/t ofCO2 avoided.
This compares favorably with the cost of many other options considered for achieving
large reductions in emissions. Use of this technique would allow continued provision of
large-scale energy supplies using the established energy infrastructure. There is
considerable scope for new ideas to reduce energy consumption and costs of CO2 capture
and storage which would accelerate the development and introduction of this technology
7th
25

REFERENCES
1. Department of Trade and Industry (UK), Gasification of Solid and Liquid Fuels
for Power Generation, report TSR 008, Dec. 1998
2. Department of Trade and Industry (UK), Supercritical Steam Cycles for Power
Generation Applications, report TSR 009, Jan. 1999
3. Durie R, Paulson C, Smith A and Williams D, Proceedings of the 5thInternational
Conference on Greenhouse Gas Control Technologies, CSIRO(Australia)
publications, 2000
4. Eliasson B, Riemer P W F and Wokaun A (editors), Greenhouse Gas Control
Technologies, Proceedings of the 4th International Conference, Elsevier Science
Ltd., Oxford 1999
5. Herzog H, Eliasson B and Kaarstad O, Capturing Greenhouse Gases, Scientific
American, Feb. 2000, 54-61
6. Intergovernmental Panel on Climate Change (IPCC), Climate Change 1995 -The
Science of Climate Change, Cambridge University Press, 1996
7. International Energy Agency, Key World Energy Statistics, 1999 edition.IEA
Greenhouse Gas R&D Programme, Transport &Environmental Aspects of Carbon
Dioxide Sequestration, 1995, ISBN 1 898373 22 1
8. IEA Greenhouse Gas R&D Programme, Abatement of Methane Emissions,
June1998, ISBN 1 898 373 16 7
9. IEA Greenhouse Gas R&D Programme, Ocean Storage of CO2, Feb. 1999, ISBN
1 898 373 25 6
10. IEA Greenhouse Gas R&D Programme, The Reduction of Greenhouse Gas
Emissions from the Cement Industry, report PH3/7, May 1999
11. IEA Greenhouse Gas R&D Programme, The Reduction of Greenhouse Gas
Emissions from the Oil Refining and Petrochemical Industry, report PH3/8, June
1999
12. www.ipcc.ch
13. www.Greenfacts.org
14. www.ieagreen.org.uk
7th
26

239807518 ccs-report-for-print

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (6)

Similar to 239807518 ccs-report-for-print

Similar to 239807518 ccs-report-for-print (20)

More from homeworkping4

More from homeworkping4 (20)

Recently uploaded

Recently uploaded (20)

239807518 ccs-report-for-print