coalbed methane in the energy economy of china
the peoples republic of china (china) produces and consumes the largest quantity of coal in the world(). in 1992, an estimated 12.5 to 19.4 billion cubic meters (8.4 – 13 teragrams) of methane were emitted to the atmosphere from coal mining activities in china, contributing onethird of the world’s total from this source (usepa, 1993). not only is china the largest coal producer in the world; it is unique in that underground mines produce over 95 percent of the nation’s coal. underground mines tend to have higher methane emissions. coal mines are located throughout china, with the greatest number of large mines located in the north and northeast.
methane is a major greenhouse gas, second in global impact only to carbon dioxide (co2). it tends to increase tropospheric ozone and smog formation, and may contribute to stratospheric ozone depletion. increasing methane emissions are associated with population growth and human activities that release methane to the atmosphere. major human-related sources of methane include rice cultivation, livestock, biomass burning, coal mining, oil and natural gas operations, and landfills. it is estimated that coal mining accounts for about 10 percent of the total human related methane emissions (kruger, 1993).
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the production and consumption of over one billion tons of hard coal annually in china has serious environmental impacts. the resulting emissions of methane and co2 are of global significance. china also suffers from severe local air pollution problems due to intense coal use, characterized by high levels of so2, nox and particulate emissions. in 1993, the total amount of so2 emitted was 17.95 million tons, of which coal combustion caused an estimated 90 percent (drccu, 1994). chinese cities, such as shenyang and chongqing, have some of the highest particulate and so2 concentrations in the world. acid rain is another serious environmental problem resulting from the intense coal use.
coalbed methane, a natural gas, is detrimental to the environment if vented to the atmosphere, but is a remarkably clean fuel when burned. natural gas combustion produces no so2 or particulates, and only half of the co2 associated with coal combustion. in many countries, methane produced by coal mines has historically been vented and become a wasted resource. china, on the other hand, has one of the longest histories of using coalbed methane recovered from its mines. recent experience in the us confirms that coalbed methane represents a low cost energy source and emission reduction opportunity(). methane can be recovered either before, during, or after coal mining and used as a fuel for power generation or consumed directly for industrial and residential energy needs.
in addition to its value as an energy source, drainage and use of methane from coal mines increases mine safety and productivity. methane released during underground mining is not only an environmental concern, but also is a serious safety hazard due to the explosive nature of methane in relatively low concentrations (5 – 15 percent in air). in the us and other coalproducing countries, mines install ventilation systems, supplemented in highly gassy mines by recovery systems to reduce methane concentration in the mines’ workways.
worldwide, several thousand fatalities have been recorded from underground coal mine explosions, where methane was a contributing factor. as coal mines deplete shallower coal reserves, there is a shift to mining deeper, gassier coal beds. in general, underground mines release more methane than surface mines because methane storage capacity increases with greater depth and pressure. in china, where underground mines produce over 95 percent of the coal, and half of the largest state-run mines are considered highly gassy or prone to outburst, mine ventilation and methane drainage is critical for mine safety. since the 1980’s, china’s coal mines have greatly improved their safety record. from 1980 to 1993, mines reduced the fatality rate from 8.2 to 4.6 people per 1 million tons of coal mined (drccu, 1994). the goal of the “mine safety law”, implemented in 1992, is to further increase safety in the coal mines, especially at township and village mines. the chinese government recognizes the importance of mine safety, and plans to increase drainage and recovery of coalbed methane associated with mineable reserves of coal as a major strategy for the industry.
this report focuses on the potential for expanding recovery and use of coalbed methane in china. it includes a review of china’s primary energy sources, current energy strategy, and an assessment of the potential role of coalbed methane in meeting china’s future energy needs. the report describes the magnitude and location of coalbed methane resources, and analyzes factors affecting recoverability of resources, use options, and profiles of specific regions with high potential for coalbed methane development. finally, the report identifies actions necessary to encourage development of coalbed methane in china and overcome existing barriers(). it also recommends follow-up technical assistance activities to help ensure efficient use of this resource.