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Report 2 of 5: Managing
Methane - China
Introduction
Methane is a greenhouse gas that is between twenty to sixty times more reactive than carbon dioxide. Due to human activities, atmospheric concentrations of methane are rising, creating adverse impacts on the ozone and contributing to increased smog formation and global warming. Fortunately, methane can also be a useful energy source if it is captured and used effectively.
A principal source of methane is from its release during coal mining operations. As plant material is converted into coal, large quantities of methane rich gas are generated and stored within the coal. The presence of this gas can cause explosions during underground coal mining. Coal deposits store large quantities of methane through the physical process of absorption and it is the absorbed methane that is liberated as coal is mined. The escaping gas must either be captured in methane recovery systems, or ventilated to the atmosphere in order to prevent hazardous explosions.
Coal mining in China
China is the largest producer of coal in the world, generating about 1.1 billion tons of coal every year. It is rich in coal bed methane and its deposits account for an estimated one third of the world’s total methane, mainly from underground mines which have high emission levels. However, only 110 of 600 state run coal mines have systems in place to recover methane and only forty of these actually use the recovered methane.
Widespread use of coal in China has created severe local air pollution. Coal bed methane is a remarkably clean fuel when burned and resources are distributed throughout the country. There are an estimated 30-35 trillion cubic metres of methane reserves in China. 500,000,000 cubic metres of methane can power a 20 MW power plant for one year. A 20 MW power plant produces enough power to meet the needs of a small city with a population of 20,000 people. The increased use of methane as a fuel would decrease the use of fossil fuels and associated environmental problems.
The Global Environmental Facility
The Global Environmental Facility (GEF) is a joint venture of the United Nations Development Programme (UNDP), the United Nations Environment Programme (UNEP) and the World Bank. GEF is a financial mechanism that provides grants and concessional funds to developing countries for projects and activities designed to protect the global environment. GEF resources address climate change, biological diversity, international waters and depletion of the ozone layer.
The development of methane energy in China began to take substantial steps when UNDP provided technical assistance to the Chinese Government in the 1990s. GEF and China’s Ministry of Coal set up a project to reduce atmospheric methane emissions and recover clean burning methane as a fuel.
Development of coal bed methane resources in China
The program was designed to:
- improve the efficiency of the coal mine methane recovery systems
- utilise the recovered methane for beneficial purposes that would prevent it from escaping into the atmosphere
- improve productivity and safety of China’s coal mines
- develop a community of technologists that could advance the industry into full national proportions
The project succeeded in developing the capabilities in China for sustained coal bed methane development by providing:
- Advanced technologies and techniques to assess the coal bed methane resources and to more efficiently and effectively extract and capture the gas than had been common practice in China
- Training of technical personnel in the proper utilisation of the technologies
- Exposure of technical and government personnel to developments abroad
- Exchange of technical ideas through technical conferences
The recovery method
It is essential to extract methane before mining because of the danger to miners. Secondary precautions, such as venting fresh air into the mining shaft to ensure that methane levels remain below 1% and that it is safe for humans to move about in, are taken when the actual mining is being done. The methane is removed from the mines by vertical drilling. There are large pockets in the coal bed where the methane is trapped. After the pockets have been located, the methane is extracted before any mining takes place in that area.
Water is used to create pressure and make a fissure in the coal bed. Once the water has been removed, the methane naturally collects in the fissure and can be pumped through pipes to the surface where it is stored in cylindrical storage tanks. This type of drilling collects the methane efficiently and practically eliminates release of the gas into the atmosphere. It makes the recovery of coal safer and can ultimately increase the volume of methane captured.
Benefits of the project
Coal bed methane can be a valuable energy resource that is important to economic development and, if properly captured and utilised, can result in significant environmental benefits. The production and sale of coal bed methane can be a source of significant new revenues as well as a means of reducing coal mining costs.
Coal bed methane has been commercialised in a few cities in China. Pipelines have been installed to connect the fuel to the residential districts and enterprises, which generates considerable revenue to the coal companies. As a result of the increased use of coal bed methane at Teifa City for home cooking in 20,000 homes in place of coal, there have been significant reductions in sulphur dioxide, nitrogen oxides, particulate matter, carbon dioxide and carcinogens in the atmosphere.
In addition to the extra profits received by selling the gas, considerable cost savings in the coal mining operations have resulted from coal bed methane recovery. For example, the utilisation of the gas substituted coal to be burned. Savings were also made from the reduced electric power needs of the mines for ventilating the methane, for safety considerations, by approximately 20%. As a result of reduced electricity requirements for methane ventilation, emissions from the power plant servicing the coal bed methane have been reduced as well.
Since coal bed methane production began under the UNDP project, no coal mine explosions have occurred because of the significantly reduced gas levels in the mine. The recovery of methane has substantially reduced the greenhouse gas emissions while improving coal mine production and safety, and local and global air quality.
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Intermediate Technology Development Group would like to acknowledge UNDP for providing the original material on the development of coalbed methane resources in China.
This document is an output from a project funded by the UK Department for International Development (DFID) for the benefit of developing countries. The views expressed are not necessarily those of the DFID.
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