India, due to its northbound requirement of energy coupled with constantly depleting conventional sources of energy, is forced to hunt alternatives to stay abreast with its energy requirement. Since the inception of 21st century, in India intense importance has been given for finding out more and more energy resources; specifically non-conventional ones like CBM, shale gas and gas hydrates, as gas is less polluting compared to oil or coal. Among all of these alternatives, CBM evolves as the most definitive alternate to the conventional gas amidst depleting resources and increasing prices.
Coal bed methane is generated during coalification process which gets adsorbed on coal at higher pressure. However, it is a mining hazard. Presence of CBM in underground mine not only makes mining works difficult and risky, but also makes it costly. Even, its ventilation to atmosphere adds green house gas causing global warming. However, CBM is a remarkably clean fuel if utilised efficiently. CBM is a clean gas having heating value of approximately 8500 kCal/kg compared to 9000 kCal/kg of natural gas obtained from other sources. It is of pipe line quality; hence can be fed directly to national pipeline grid without much treatment. Production of methane gas from coal bed would lead to de-methanation of coal beds and avoidance of methane emissions into the atmosphere, thus turning an environmental hazard into a clean energy resource and thus having good prospects for commercial production of coal bed methane. Methane may be a possible alternative to compressed natural gas (CNG) and its use as automotive fuel will certainly help reducing pollution levels.
India is one of the select countries which have undertaken steps through a transparent policy to harness domestic CBM resources. The Government of India has received overwhelming responses from prospective producers with several big players starting operations on exploration and development of CBM in India and set to become the fourth after US, Australia and China in terms of exploration and production of coal bed methane. The major milestones of CBM development in India is depicted in Exhibit 01
Exhibit 01 : Major Milestones for CBM Development in India
CBM development in India
CBM holds good prospects in India. The coal-bearing formations of India occur in two distinct geological horizons in the Lower Gondwana (Permian) belts of India and the Tertiary sediments (Eocene–Oliocene) of north-eastern India, Rajasthan, Gujarat, and Jammu and Kashmir. Methane gas is entrapped within these formations at a wide range of sub-surface depths. Indian coal has gas content values ranging from 1 to 23 m3(cubic metres)/tonne. The coal-bed methane occurrence is predicted in Damodar Valley basin, a potential source presently under consideration. Also, Amlabad, Jharkhand, is expected to give higher specific gas yield compared to Raniganj field, West Bengal. Amlabad is well known as a potential source of coal-bed methane. Giving highest priority to the efficient use of energy resources and long-term sustainability of energy supplies, the Government of India requested international assistance in coal-bed methane recovery and its commercial utilisation. The country is one of the chief producers of coal from underground mines in the world. One of the major fields in Jharia is on fire as can be seen from satellites in space. Two of the mines in this coalfield are particularly ‘gassy’, and have been selected as demonstration sites for a GEF (Global Environment Facility)project.
The chronological development of CBM which marked the importance of unconventional gas in Indian pretext is depicted in Exhibit 02.
Exhibit 02: Chronological development of CBM
The recoverable reserve of about 800 BCM and gas production potential of about 105 million cubic metres per day over a period of 20 years have been estimated. Coal-bed methane potential is thus about 1.5 times the present natural gas production in India, which is capable of generating about 19,000MW of electricity. The potential of CBM production in India as per basin and area is depicted in Exhibit 03
Exhibit 03: CBM Potential in India ( Factoring Major and Other Basins for CBM
Exhibit 04: Energy Equivalent of CBM Potential in India
Post the formulation of CBM policy in 1997, for the first time CBM blocks were allocated in 2002 under CBM Round I for development. With 6 blocks awarded and 3 blocks on nomination basis, CBM Round I saw a total of 9 blocks on offer for development with area of 1930 sq. km for the exploits. From 2002 till date a total of four CBM block allocation rounds have taken place with a total of 33 blocks on offer and 17, 426 sq. km of area under exploits. State wise number blocks offered till date with total area coverage is depicted in Exhibit 05
Exhibit 05: State Wise CBM Blocks Offered (Till CBM IV Round)
CBM as an alternative to CNG
The coal-bed-methane mainly contains methane which is a clean fuel and interchangeable with other sources of natural gas. As the demand for natural gas in India is high, it is now economically viable to recover the coal-bed methane and to transport the gas to other cities where natural gas is in short supply.
This can help to meet the demand for gas, especially in the peak shaving periods. Moreover, purified CBM can be used as a clean automotive fuel in the form of liquefied natural gas (LNG) or compressed natural gas (CNG) for public transport and fixed route trucks. Liquefaction of CBM might become one of the most cost effective methods to transport reasonable quantities of the gas to remote customers in India.
Storage and Loading of LCBM
LCBM is stored in double layer tanks with very good insulation at the bottom and the layer gap. It is stored at ambient pressure and -162oC. The LCBM is commonly transported by road tankers at about 40 cu.m per tanker to distant cities where natural gas is needed. Each full loaded LCBM road tanker can supply 30,000 families for one day domestic gas usage.
When the LCBM toad tankers reach the destination, LCBM will be unloaded to the storage tank in the vaporization plant. Then, LCBM is vaporized back to CBM and supplied to the customers as natural gas for domestic gas uses or automotive fuel as CNG public transportation.
CBM can be utilized effectively as a supplemental gas source to meet the high gas demands in the cities of India, especially for peak shaving to ensure uninterrupted supply of gas. The liquefaction process of CBM is used to purify and reduce the volume 600 times to form LCBM, which becomes economically viable for wide scale distribution to down stream markets. This innovative use of CBM aims to make the best use of resources and to help reducing greenhouse gas emissions as well as improving mine safely. The R&D opportunities associated with CBM can be highlighted as under:
- About 0.8 BCM of methane is annually released into atmosphere by Indian Coal mines during its operations. These are not being systematically recovered and put back to use. This calls for new technologies to capture this methane in a cost effective manner.
- New methods to extract Pre-mining methane, Coal mine methane and Post mine methane.
- Gas to Liquid (GTL) to convert the CBM from stranded mines into liquid fuels for easier transportation as well as consumption.
- Enhanced usage of CBM as automotive fuel via CNG, LCNG etc.
- New infrastructure to transport CBM economically.
- New technologies to make the optimum use of this mining hazard into a potential energy source for power generation, industries, Steel plants; manufacture of methanol etc.
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