This article is adapted and reproduced from GE Energy’s Cogen Magazine, Issue 5, 2011, p 31
In the search for new energy sources and low-cost alternatives to natural gas, a previously little-used gas has moved into the spotlight. With major reserves found all over the world, coal bed methane (CBM), also called coal seam methane (CSM) is already being used as an energy source in the United States, Canada and Australia. In addition, Russia is beginning to take an interest in this subterranean treasure. In fact, the first CSM-powered Jenbacher gas engine supplied to Russia recently went online in Kusbass/Siberia, and it is already clear that this will by no means be the last…
(Almost) Pure Methane
As opposed to the mines gas that is extracted from active and closed pits, CBM can be obtained directly by drilling into unused coal deposits (beds). CBM is a free gas that exists in cracks, fissures and powers and as an absorbed gas on the inner, upper surface of the coal and surrounding Brock. Above all, it can be obtained from coal beds that, due to their location or characteristics are unsuitable for mining.
Apart from the possibilities for its efficient exploitation in many parts of the world, the prime reason CBM is a suitable alternative to natural gas is its high methane content of over 95 percent, which makes it an excellent fuel.
CBM (CSM) – Coal Bed Methane (Coal Seam Methane) – Gas from unexploited coal deposits (>90% methane content)
CMM – Coal Mine Methane – Gas from active collieries (25-60% methane content)
AMM – Abandoned Mine Methane – Gas from closed collieries (60-80% methane content)
Global Coal Bed Methane Reserves
Large reserves of CBM can be found all over the world. These are already being exploited successfully and employed as an energy source, especially in the U.S. Canada and Australia.
An outstanding example of the use of CBM for decentralised energy supply is the Australian state of Queensland, which with Clarke Energy in recent years has installed a gas-fired electricity generating plants with a capacity of over 150MW and has thus covered a considerable part of its local power needs from this new energy source.
Coal Bed Methane Safety
The extraction of CBM in the vicinity of active collieries not only offers the potential of a local energy source, but also the advantage of pre-degassing of the methane in the coal. As a result, safety is increased during subsequent mining operations.
Double Climatic Benefits
In such cases, the use of CBM also demonstrates its value through a two-pronged reducing in greenhouse gases. First, with CBM, the highly active greenhouse gas methane, is transformed into less harmful CO2 even prior to its release during coal mining (methane released into the atmosphere has 21-fold greater climate relevance than does CO2. Second, CO2 emissions per kWh can be reduced markedly by substituting fossil fuels. In addition to the ecological benefits, this also results in an economic advantage, since related project qualify for carbon credits.
Global CBM Gas Engine Applications
At present, Jenbacher gas engines with a capacity in excess of 400MW are being operated with mines gas and CBM. These provide an annual production capacity of over 3 million MWh of electricity, thus saving 830 million cubic metres of natural gas equivalents and preventing methane emissions equating to over 8 million tonnes of CO2. Once again, these figures provide confirmation of the environmental advantages of the Jenbacher gas engine from GE, which demonstrate great flexibility with regard to fuel and – apart from natural gas – can also be operated with a large number of biological and special gases.
Clarke Energy has installed and maintains a large fleet of coal seam gas powered generation equipment in Australia, the UK and China.