Energy security – ‘Clean Coal’ has potential to change the world from pariah to paragon of virtue in high oil price regime.

Energy security – ‘Clean Coal’ has potential to change the world from pariah to paragon of virtue in high oil price regime.

A. The thirst of populous emerging economies for energy and the industrial countries’ sustained need for energy will ensure a further rise in demand. However, it looks as if the supply of oil, and later also natural gas, will not keep pace with this demand. Only by leveraging every possible means will it be possible to compensate the imbalances emerging on the horizon. However, during the transition to the renewable sources of energy such as wind and solar age, an energy gap will have to be filled.

B. With oil currently trading at around USD 140/bbl, coal-to-liquid technology is already an interesting alternative from a purely commercial point of view. Coal offers great potential as a substitute for oil and natural gas in the medium term, but so far its versatility has been underestimated. Going forward, coal could attract more attention in all three major energy sectors – power generation, the heating market and transport – provided that the right technologies delivering higher efficiency and lower environmental burdens take root. Environmental risks emphasize need for “clean coal”. Global warming is one of the biggest dangers facing human existence on earth, and combating this danger is therefore one of the greatest challenges. Since coal causes 40% of global CO2 emissions, only advanced technology can pave the way to a better future. The required quantum leaps in technology could, however, open the doors to the global mass markets. The need for investment is very high not only in emerging economies like China and India but also in US and Europe. CO2-free coal-fired power plants could become a milestone on the way to a better energy future in spite of their additional fuel consumption.

C. Worldwide prospects for energy is actually quite good, but only if all possible levers are used. These include steps – apart from urgently needed conservation and efficiency-enhancing strategies – to diversify the range of energy carriers with an even greater drive to mobilize renewable energies and to continue developing potential alternative technologies. In public debate about our energy options after the petroleum age virtually no consideration is given to coal or else it gets very bad reviews. In the developed countries, coal is usually considered synonymous with a dangerous climate killer; in the developing countries, for inhuman labor conditions in the mining industry, the talk is of ‘blood coal’. At best, coal is given credit for its valuable contribution to energy security during the industrialization era.

D. Today, coal is used in the industrial countries above all as a source of fuel for generating electricity, for the heating market and for metal production. In some of the emerging economies, coal is still used in some places to fire steam engines. Going forward, coal could attract much more attention in all three major energy sectors – power generation, heating and transport – provided that the right technologies with higher efficiency levels and a low environmental impact take root. In this sense, the versatility of coal has been underestimated. As a substitute for the hydrocarbon fuels oil and natural gas, which will become increasingly scarce in the relatively near future, coal offers considerable potential for improving our energy structures in future. However, only advanced technologies and innovations will be able to pave the way for coal into a better future.

E. As mentioned above, environmental risk emphasizes need for “clean coal”. Global warming is one of the biggest dangers facing human existence on earth, and combating this danger is therefore one of the greatest challenges facing mankind. Fossil fuels, especially those that pose the greatest threat to the earth’s climate, will only have a future if they can be reinvented from an ecological standpoint. Coal accounts for 40% of global output of carbon dioxide (CO2). The ‘bridge to the future’ must therefore lead to ‘clean coal’, which if possible has to be climate neutral and thus acceptable to the public at large. If ‘King Coal’, the mythical figure of the coalmining saga, stops wearing a black robe in future and instead dons an environmentally-friendly white robe, his days will not be numbered and he may go on to prosper the second time round. Until renewable sources of energy are finally mature and established enough to shoulder the burden of the world energy supply largely on their own, the purified ‘clean coal’ may develop into one of the biggest sources of hope for a more secure energy supply.

F. One advantage of coal is that it offers the greatest range of global reserves among the fossil fuels. Plenty of coal reserve, up to about more than 200 years worth, is readily available, almost all over the world. By contrast, the ranges for oil (42 years) and natural gas (63 years) are much smaller.

G. The search for alternatives to conventional fuels did not seem to be an urgent task in late 1998 when a barrel of oil cost less than USD 10. Not quite 10 years later, with oil going for an annual average price of USD 65 in 2006. The most prominent participants in the contest for the fuels of the future are:

(i) First-generation bio-fuels are increasing in popularity in the most diverse countries of the world, such as Brazil, the US and Germany. In Brazil, they have long since become commercially competitive. Research on the second generation, the synthetic bio-fuels (biomass-to-liquids, or BTL), is continuing briskly.

(ii) Natural gas has been a common fuel in some countries for years. More appears to be possible if the catalytic conversion of natural gas proves able to secure the availability of a synthetic fuel, so called GTL (gas-to-liquids), on an industrial scale. GTL and BTL will mean fewer emissions and higher efficiency.

(iii) By means of liquefaction (coal-to-liquids, CTL), coal may directly replace oil even as a fuel. Thanks to higher reserve and resource ranges, coal as a substitute would clearly have an advantage over fuels based on natural gas.

(iv) Nuclear energy will be one of the major contributors to the world energy sources. Although, there is furious opposition against nuclear energy in some part of the world, the advantage of its potential of delivery of clean energy is the major plus point makes it better option.

H. A total of USD 10 trillion is expected to be invested in power generating plants around the globe up to 2030, with over USD 2 trillion being invested in China alone. The need for investment is very high all over the world. For investments, not only the direct costs but also the implications for the world climate will increasingly gain importance. This holds all the more so as over the past 30 years the share of CO2 emissions from coal has risen from 35% to 40% – with total emissions rising by 70% globally. One much more revolutionary project is a plan to develop emission-free coal-fired generating plants. Upstream and downstream CO2 sequestration, for which there are several different methods, aims for climate conservation. Thus, new power generation technology for fewer emissions will become the backbone of industrialization.

Energy security and reduction of greenhouse gases for cleaner environment – Most challenging issues of present day:

Energy security and reduction of greenhouse gases for cleaner environment – Most challenging issues of present day:

It has become essential to every nation to access to cheap energy for their smooth functioning and upliftment of their economies. However, the uneven distribution of energy supplies among all the nations and the critical need for energy has led to significant vulnerabilities. Global energy security has become synonym to political stability and good administration.

Political instability of several energy producing countries, the manipulation of energy supplies, the competition over energy sources, attacks on supply infrastructure and accidents and natural disasters are the threat to energy security of any nation. It is also the limited supplies of the most common forms of primary energy, i.e. Oil and Gas that changes perceptions on this topic.

Although plenty of coal, up to about more than 200 years worth, is readily available, almost all over the world, coal is not the fossil fuel of choice for many more advanced countries because of its highly polluting nature. The potential need to change our perception on primary energy sources in the foreseeable future and implementation of new technology, are the solution of the energy security question. Improper planning and ineffective strategies at macro level may lead to higher energy prices, more limited access to sources of energy, competitions and political troubles, which in turn make the threat even larger, as energy plays an important role in the national security of any given country.

One of the leading threats to energy security is the significant increase in energy prices all over the world. Long term measures to increase energy security lies on reducing dependence on any one source of imported energy, increasing the number of sources of energy and suppliers. Greater investment in native renewable energy technologies and energy conservation are envisaged in many of the developed nations. Certainly, every nation’s ultimate goal is to power their entire country with renewable green energy such as solar, wind, and other renewable sources. However, our current technology is not to the point where this would be affordable. Solar and wind do not currently have the energy density to supply us with all the power we need.

Therefore, under the above scenario, on broader sense, two technologies may be very useful and relevant, they are:

(i) Nuclear power, and

(ii) Green-coal power (Clean coal technology).

Nations of developed and emerging economies should think of energy mix of above two technologies in a big way to achieve fair amount of energy security. The raw materials for the above energy mix are present, almost, world over. The cost of power generated by above two technologies and energy mix is also reasonable and within reach of the general population and industries. After all, nuclear power is our one of the best option for clean energy today. In the above energy mix, Hydro-power may also be included, wherever available.

With the huge advances in technology in recent years, any shortcomings we face for the above two mix of energy, can be sorted out easily. Further, dependence on agricultural based biofuel can also be reduced, enhancing chances of availability of more food, thereby reducing poverty.

Coal is Essential for Energy Security for many – Strategies to enlarge supply base and reduce environmental impacts are the prerequisites:

Coal is Essential for Energy Security for many – Strategies to enlarge supply base and reduce environmental impacts are the prerequisites:

A. More and more frequent environmental problems and disasters – floods, forest fires, tornados, air pollution in big cities – cause growing concerns everywhere. Energy harvesting, conversion, production and use contribute to these environmental burdens.

Hence, improving the environmental performance of the energy sector is of paramount importance. Thus, wider application of cleaner fuels and conversion technologies is a key element in the strategy to improve the environmental performance of the energy sector. Further, the lower price of coal as compare to petroleum based fuels; the interest in coal is renewed because of the more even geopolitical distribution of coal reserves and of larger supply bases of coal allover the world.

In fact, the environmental concerns about coal are not associated with coal itself, but with its utilization in different stages of the energy chain. Novel and more environmentally friendly technologies for coal utilization, commonly known as “Clean Coal Technologies” (CCT), are believed to be able to bring coal back into the picture. Hence, CCT recently enjoy a growing interest almost all parts of the world. At present, this interest mostly focuses on cleaner coal conversion through increased efficiency and CO2 capture technologies, for which large R&D efforts are ongoing worldwide.

B. Market implementation of CCT is expected to cause an increase in coal use. Coal demand could also rise significantly because the recent sharp increase in oil prices has a lower impact on coal than on gas prices. This is explained by the more favorable geopolitical distribution of coal reserves compared to that of gas. As a result, coal has become cheaper in relative terms than oil and gas. All in all, in a scenario of soaring oil & gas prices, coal is predicted to be the energy source with the fastest growing demand. The expected increase in coal demand for power generation raises the question of its secure availability in the future. Thus, enlargement of the coal supply base is essential throughout the world, with adoption of cleaner technology.

C. The enlargement of the coal supply base can take place in four main directions:

(a) More powerful mapping techniques for coal reserves - Modern geophysics and seismic techniques, improve mine planning and exploitation by reducing geological uncertainties and increasing extraction efficiencies. At the same time, they can reduce environmental externalities and energy use for coal extraction.

(b) Improvement of existing under-ground mining technologies - Underground (deep) coal mining accounts for about 60% of world coal production. Current best coal recovery rates for underground mining are 50-60% for the “room-and-pillar” technology and about 75% for “longwall” mining. The implementation of modern automated and computerized mining technologies can increase these recovery rates.

(c) Research and development for underground coal gasification - Underground gasification of coal deposits which are not technically or economically exploitable (anymore) with conventional mining technologies, can add enormous coal supply potential in Europe and worldwide. At present underground coal gasification is at an experimental stage. Significant further efforts are necessary to make it technically and economically viable. In many of the countries like India etc., commercialization of underground gasification technologies may reduce the energy import dependence and enhance energy security scenario, apart from creating new employment.

(d) Utilization of coalmine methane (CMM) gas - Methane gas, released from coalmines, has always raised serious safety and environmental concerns. Methane is highly explosive when accumulated in confined areas. It is also a powerful greenhouse gas with 20- times stronger global warming potential than carbon dioxide. On the other hand, CMM, which consists mainly of natural gas, is a suitable clean fuel. The capture and useful utilization of CMM can bring important synergy benefits in terms of enhanced security of supply and better environmental and safety performance of coal mining.

D. Therefore, for realizing the full potential of CCT, coal is sufficiently

(a) Abundant… only if we keep working on the enhancement of coal reserves,

(b) Cheap… as long as the supply continues to match the demand,

(c) Reliable… as long as the supplies are diversified.

To reach market maturity, clean coal technologies, covering extraction, preparation and conversion, need a long term vision and investment security. In the present pre-commercial stage they need firm political commitment and further R&D support.

‘Carbon sequestration’ - Greatest challenge of clean coal technology (‘FutureGen’ project) to deliver "zero emissions" in reality:

‘Carbon sequestration’ - Greatest challenge of clean coal technology (‘FutureGen’ project) to deliver "zero emissions" in reality:

A present trend of clean coal technology is moving rapidly towards a very interesting phase, realizing efficiency improvements of coal. In fact, this clean coal technology together with the use of natural gas and renewables such as wind will not provide the deep cuts in greenhouse gas emissions necessary to meet future national targets. Naturally, a plant to produce hydrogen from coal and sequester emissions will be the world’s zero emission coal-fired plant – as envisaged for ‘FutureGen’ project.

As discussed earlier, the clean coal technology field is moving in the direction of coal gasification with a second stage so as to produce a concentrated and pressurized carbon dioxide stream followed by its separation and geological storage. This technology has the potential to provide what may be called "zero emissions" - in reality, extremely low emissions of the conventional coal pollutants, and as low-as-engineered carbon dioxide emissions.

A. The greatest challenge now is to sequester emissions by carbon capture and geological storage technology. The technology, known as carbon sequestration, has attracted global attention from industries and governments that are eager to capture and bottle up the gas that can linger in the atmosphere for decades.

B. Carbon capture and sequestration begins with the separation and capture of CO₂ from power plant flue gas and other stationary CO₂ sources. At present, this process is costly and energy intensive, accounting for the majority of the cost of sequestration. However, analysis shows the potential for cost reductions of 30–45 percent for CO₂ capture. Post-combustion, pre-combustion, and oxy-combustion capture systems being developed are expected to be capable of capturing more than 90 percent of flue gas CO₂.

C. The primary function of carbon sequestration research and development (R&D) objectives are:

(1) Lowering the cost and energy penalty associated with CO₂ capture from large point sources; and

(2) Improving the understanding of factors affecting CO₂ storage permanence, capacity, and safety in geologic formations and terrestrial ecosystems.

D. After capturing of carbon the next step is to sequester (store) the CO_2; which has mainly two processes - (i) The primary means for carbon storage are injecting CO₂ into geologic formations or (ii) using terrestrial applications.

(i) Geologic sequestration involves taking the CO₂ that has been captured from power plants and other stationary sources and storing it in deep underground geologic formations in such a way that CO₂ will remain permanently stored. Geologic formations such as oil and gas reservoirs, unmineable coal seams, and underground saline formations are potential options for storing CO₂. Storage in basalt formations and organic rich shales is also being investigated.

(ii) Another form of sequestration is ‘terrestrial sequestration’, which involves the net removal of CO₂ from the atmosphere by plants and microorganisms that use CO₂ in their natural cycles. Terrestrial sequestration requires the development of technologies to quantify with a high degree of precision and reliability the amount of carbon stored in a given ecosystem.

E. Any carbon sequestration program should involve (a) Core R&D, and (b) Demonstration & Deployment.

(a) Core R&D – Core R&D accomplished through laboratory and pilot-scale research, develops new technologies and systems for reducing greenhouse gas emissions from industrial sources. Core R&D integrates basic research and computational sciences to study advanced materials and energy systems. It focuses on few major areas for technology development: (i) CO₂ Capture, (ii) Carbon Storage, (iii) Monitoring, Mitigation, and Verification, (iv) Non-CO₂ Greenhouse Gas Control, and (v) Breakthrough Concepts.

(b) Demonstration & Deployment – It speeds the development of new technologies through commercial opportunities and collaboration with Govt. departments. Core R&D scientists also learn practical lessons from these demonstration projects and are helpful to develop further technology solutions and innovations.

As mentioned above, this system along with use of natural gas and renewable energy sources such as wind, solar etc., will be advantageous in order to mitigate to a great extent in greenhouse gas emissions necessary to meet future national targets. Many countries see "zero emissions" coal technology as a core element of its future energy supply in a carbon-constrained world. They have program to develop and demonstrate the technology and have commercial designs for plants with an electricity cost of only 10% greater than conventional coal plants available by 2012. Australia is very well endowed with carbon dioxide storage sites near major carbon dioxide sources, but as elsewhere, demonstration plants will be needed to gain public acceptance and show that the storage is permanent. In general, "zero emissions" technology seems to have the potential for low avoided cost for greenhouse gas emissions.

‘FutureGen’ project - to design, build and operate a nearly emission-free coal-based electricity and hydrogen:

‘FutureGen’ project - to design, build and operate a nearly emission-free coal-based electricity and hydrogen:

The clean coal technology field is moving very rapidly in the direction of coal gasification with a second stage so as to produce a concentrated and pressurised carbon dioxide stream followed by its separation and geological storage. At present the high cost of carbon capture and storage renders the option uneconomic. But a lot of work is being done by many of the research institutes, to improve the economic viability of this system.

More recently department of energy (DOE) of Federal Govt. of the USA has announced ‘FutureGen’ project to design, build and operate a nearly emission-free coal-based electricity and hydrogen production plant. It will use cutting-edge technologies to generate electricity while capturing and permanently storing carbon dioxide deep beneath the earth. The integration of these technologies is what makes FutureGen unique. Researchers and industry have made great progress advancing technologies for coal gasification, electricity generation, emissions control, carbon dioxide capture and storage, and hydrogen production. But these technologies have yet to be put together and tested at a single plant - an essential step for technical and commercial viability.

Therefore, the FutureGen initiative would have comprised a coal gasification plant with additional water-shift reactor, to produce hydrogen and carbon dioxide. About one million tones of CO₂ would then be separated by membrane technology and sequestered geologically. The hydrogen would have been be burned in a power generating plant and in fuel cells. The project was designed to validate the technical feasibility and economic viability of near-zero emission coal-based generation. Construction of FutureGen was due to start in 2009, for operation in 2012.

Coal gasification processes –

(a) In conventional plants coal, often pulverised, is burned with excess air (to give complete combustion), resulting in very dilute carbon dioxide at the rate of 800 to 1200 g/kWh.

(b) Gasification converts the coal to burnable gas with the maximum amount of potential energy from the coal being in the gas.

(c) In Integrated Gasification Combined Cycle (IGCC) the first gasification step is pyrolysis, from 400°C up, where the coal in the absence of oxygen rapidly gives carbon-rich char and hydrogen-rich volatiles.

(d) In the second step the char is gasified from 700°C up to yield gas, leaving ash. With oxygen feed, the gas is not diluted with nitrogen.

(e) The key reactions today are C + O₂ to CO, and the water gas reaction: C + H₂O (steam) to CO & H₂ - syngas, which reaction is endothermic.

(f) In gasification, including that using oxygen, the O₂ supply is much less than required for full combustion, so as to yield CO and H₂.

(g) The hydrogen has a heat value of 121 MJ/kg - about five times that of the coal, so it is a very energy-dense fuel.

(h) However, the air separation plant to produce oxygen consumes up to 20% of the gross power of the whole IGCC plant system.

(i) This syngas can then be burned in a gas turbine, the exhaust gas from which can then be used to raise steam for a steam turbine, hence the "combined cycle" in IGCC.

(j) To achieve a much fuller clean coal technology in the future, the water-shift reaction will become a key part of the process so that:

(i) C + O₂ gives CO, and

(ii) C + H₂O gives CO & H₂, then the

(iii) CO + H₂O gives CO₂ & H₂ (the water-shift reaction).

(k) The products are then concentrated CO₂ which can be captured, and hydrogen. (There is also some hydrogen from the coal pyrolysis), which is the final fuel for the gas turbine.

(k) Overall thermal efficiency for oxygen-blown coal gasification, including carbon dioxide capture and sequestration, is about 73%.

(l) Using the hydrogen in a gas turbine for electricity generation is efficient, so the overall system has long-term potential to achieve an efficiency of up to 60%.

‘Clean Coal Technology (CCT)’ – methods to remove pollutants from coal.

‘Clean Coal Technology (CCT)’ – methods to remove pollutants from coal.

Carbon dioxide from burning coal is the main focus of attention today, since it is implicated in global warming, and the Kyoto Protocol requires that emissions decline, notwithstanding increasing energy demand.

A. Capture & separation of Carbon dioxide - A number of means exist to capture carbon dioxide from gas streams, but they have not yet been optimised for the scale required in coal-burning power plants. The focus has often been on obtaining pure CO₂ for industrial purposes rather than reducing CO₂ levels in power plant emissions. Capture of carbon dioxide from flue gas streams following combustion in air is expensive as the carbon dioxide concentration is only about 14% at best. This treats carbon dioxide like any other pollutant and as flue gases are passed through an amine solution the CO₂ is absorbed. It can later be released by heating the solution. This amine scrubbing process is also used for taking CO₂ out of natural gas. There is an energy cost involved. Captured carbon dioxide gas can be put to good use, even on a commercial basis, for enhanced oil recovery. Injecting carbon dioxide into deep, unmineable coal seams where it is adsorbed to displace methane (effectively: natural gas) is another potential use or disposal strategy.

B. Coal arriving at a power plant contains mineral content that needs to be removed, in order to make it clean, before it is burnt. A number of processes are available to remove unwanted matter and make the coal burn more efficiently.

(a) Coal cleaning by washing - Coal washing involves grinding the coal into smaller pieces and passing it through a process called gravity separation. One technique involves feeding the coal into barrels containing a fluid that has a density which causes the coal to float, while unwanted material sinks and is removed from the fuel mix. The coal is then pulverised and prepared for burning.

(b) Gasification of coal – The Integrated Gasification Combined Cycle (IGCC) plant is a means of using coal and steam to produce hydrogen and carbon monoxide (CO) which are then burned in a gas turbine with secondary steam turbine (ie combined cycle) to produce electricity.

Coal gasification plants are favoured by some because they are flexible and have high levels of efficiency. The gas can be used to power electricity generators, or it can be used elsewhere, i.e. in transportation or the chemical industry. In Integrated Gasification Combined Cycle (IGCC) systems, coal is not combusted directly but reacts with oxygen and steam to form a "syngas" (primarily hydrogen). After being cleaned, it is burned in a gas turbine to generate electricity and to produce steam to power a steam turbine. Coal gasification plants are seen as a primary component of a zero-emissions system. However, the technology remains unproven on a widespread commercial scale.

(c) Removing pollutants from coal - Burning coal produces a range of pollutants that harm the environment: Sulphur dioxide (acid rain); nitrogen oxides (ground-level ozone) and particulates (affects people's respiratory systems). There are a number of options to reduce these emissions:

(i) Sulphur dioxide (SO2) - Flue gas desulphursation (FGD) systems are used to remove sulphur dioxide. "Wet scrubbers" are the most widespread method and can be up to 99% effective. A mixture of limestone and water is sprayed over the flue gas and this mixture reacts with the SO2 to form gypsum (a calcium sulphate), which is removed and used in the construction industry.

(ii) Nitrogen oxides (NOx) - NOx reduction methods include the use of "low NOx burners". These specially designed burners restrict the amount of oxygen available in the hottest part of the combustion chamber where the coal is burned. This minimises the formation of the gas and requires less post-combustion treatment.

(iii) Particulates emissions - Electrostatic precipitators can remove more than 99% of particulates from the flue gas. The system works by creating an electrical field to create a charge on particles which are then attracted by collection plates. Other removal methods include fabric filters and wet particulate scrubbers.

Clean coal technology (CCT) – To mitigate Global warming and climate change - A discussion

Clean coal technology (CCT) – To mitigate Global warming and climate change - A discussion

Coal when burned is the dirtiest of all fossil fuels. A range of technologies are being used and developed to reduce the environmental impact of coal-fired power stations. Thus, clean coal technology (CCT) is the name attributed to coal chemically washed of minerals and impurities, sometimes gasified, burned and the resulting flue gases treated with steam with the purpose of removing sulfur dioxide, and reburned so as to make the carbon dioxide in the flue gas economically recoverable.

A. It is a known fact that, the burning of coal, a fossil fuel, is the principal causes of anthropogenic climate change and global warming. In fact, the byproducts of coal combustion are very hazardous to the environment if not properly contained. This is seen to be the technology's largest challenge, both from the practical and public relations perspectives. While it is possible to remove most of the sulfur dioxide (SO2), nitrogen oxides (NOx) and particulate (PM) emissions from the coal-burning process, carbon dioxide (CO2) emissions will be more difficult to address. Therefore, fact regarding the coal remains:

(a) Coal is a vital fuel in most parts of the world.

(b) Burning coal without adding to global carbon dioxide levels is a major technological challenge which is being addressed.

(c) The most promising "clean coal" technology involves using the coal to make hydrogen from water, then burying the resultant carbon dioxide by-product and burning the hydrogen.

(d) The greatest challenge is bringing the cost of this down sufficiently for "clean coal" to compete with nuclear power on the basis of near-zero emissions for base-load power.

B. In relation to clean coal technology, a terminology ‘carbon capture and storage’ (CCS) is being discussed. CCS is nothing but method of capturing the carbon dioxide, preventing the greenhouse gas entering the atmosphere, and storing it deep underground by various ways, such as

(a) CO2 pumped into disused coal fields displaces methane which can be used as fuel,

(b) CO2 may be pumped into and stored safely in saline aquifers, or

(c) CO2 pumped into oil fields helps maintain pressure, making extraction easier.

A range of approaches of CCS have been developed and have proved to be technically feasible. They have yet to be made available on a large-scale commercial basis because of the costs involved.

C. Clean coal technologies are continually developing. Today, efficiencies of 46% can be achieved by implementing the best available technology. With further research into techniques such as Ultra-supercritical combustion, efficiencies above 50% are envisaged in the near future. Work is underway to exploit the opportunities of capturing and storing CO2, which is an inevitable by-product of the thermal use of all fossil fuels. Coupled with integrated gasification, coal could in this way provide a source of low-carbon hydrogen for fuelling transport without producing local emissions. There will be challenges in bringing these technologies to market, but with the right mix of research investment and market incentives, coal may stake a place in a sustainable and secure energy future.

D. To summarise, burning coal, such as for power generation, gives rise to a variety of wastes which must be controlled or at least accounted for. So-called "clean coal" technologies are a variety of evolving responses to late 20th century environmental concerns, including that of global warming due to carbon dioxide releases to the atmosphere. However, many of the elements have in fact been applied for many years, and they will be only briefly mentioned here:

(i) Coal cleaning by 'washing' has been standard practice in developed countries for some time. It reduces emissions of ash and sulfur dioxide when the coal is burned.

(ii) Electrostatic precipitators and fabric filters can remove 99% of the fly ash from the flue gases - these technologies are in widespread use.

(iii) Flue gas desulfurisation reduces the output of sulfur dioxide to the atmosphere by up to 97%, the task depending on the level of sulfur in the coal and the extent of the reduction. It is widely used where needed in developed countries.

(iv) Low-NOx burners allow coal-fired plants to reduce nitrogen oxide emissions by up to 40%. Coupled with re-burning techniques NOx can be reduced 70% and selective catalytic reduction can clean up 90% of NOx emissions.

(v) Increased efficiency of plant - up to 45% thermal efficiency now (and 50% expected in future) means that newer plants create less emissions per kWh than older ones.

(vi) Advanced technologies such as Integrated Gasification Combined Cycle (IGCC) and Pressurised Fluidised Bed Combustion (PFBC) will enable higher thermal efficiencies still - up to 50% in the future.

(vii) Ultra-clean coal from new processing technologies which reduce ash below 0.25% and sulfur to very low levels mean that pulverised coal might be fed directly into gas turbines with combined cycle and burned at high thermal efficiency.

(viii) Gasification, including underground gasification in situ, uses steam and oxygen to turn the coal into carbon monoxide and hydrogen.

(ix) Sequestration refers to disposal of liquid carbon dioxide, once captured, into deep geological strata.

E. Discussion - Many experts think, the concept of clean coal is said to be a solution to climate change and global warming. Whereas, environmental groups believe it is nothing but another way of making everybody fool, in other words, it is ‘green-wash’. Environmentalists say, with this technology emission and wastes are not avoided, but are transferred from one waste stream to another. They opine that, coal can never be clean. Critics of the planned power plants assert that there is no such thing as "clean coal" and that the plant will still release large amounts of pollutants compared to renewable energy sources such as wind power and solar power. A good deal of investment in research and development and also in implementation of pollutant free renewable energy (such as wind power and solar power) has to augmented, to make the world very clean, to make the required electricity generation fully green.