METHANE FROM COAL

Methane (CH4) is a gas formed as part of the process of coal formation. When coal is mined this gas is released from the coal seam and the surrounding disturbed strata. It is also the major component of natural gas.

Methane is highly combustible – its release can therefore have serious implications for the safety of mine operations.

Methane is also a potent greenhouse gas – 21 times more harmful than carbon dioxide.

Utilising Methane
Methane is a valuable product – it can be used for power generation or domestic cooking and heating. Utilising the gas can have significant benefits – safety, environmental and economic.

There are two ways that the methane can be recovered:
• Coal Mine Methane (CMM)
• Coal Bed Methane (CBM)
CBM and CMM operations are taking place all over the world - including Australia, China, Ukraine and the USA.

Coal Mine Methane
CMM captures the methane that is released or will be released during coal mining activities.

CMM is recovered using gas drainage systems, which were originally developed for safety reasons. Depending on the characteristics of the mine, vertical wells and/or horizontal boreholes in advance of mining can be employed to recover CMM. With advanced drainage practices, mines can achieve larger quantities and higher concentrations of recovered coal mine methane.

Currently only a fraction of the CMM resource is recovered in a suitable form to be used for heat or power production - and only about one fifth of this is actually utilised. However, many mine operators are starting to realise that CMM can be profitably utilised or sold to different users, instead of being released to the atmosphere.

Coal Bed Methane
CBM captures the same gas but from deep unmined coal seams rather than in conjunction with mining activities.

CBM gas can be extracted by injecting CO2 into the coal seam displacing the methane - this is known as enhanced coal be methane (ECBM). ECBM is a method for storing the CO2 from power production or industry, thereby reducing GHG emissions.



Hydrogen from Coal


The production of hydrogen from coal and integrated gasification fuels cell are both possible routes to a low carbon future.

Hydrogen is produced from coal by first gasifying the coal into syngas – a combination of hydrogen and carbon monoxide. The syngas is then ‘shifted’ with the addition of steam, to produce additional hydrogen and to convert the carbon monoxide into carbon dioxide (CO2). The carbon dioxide can then be separated, leaving a pure stream of hydrogen.

Hydrogen can be used to produce electricity from gas turbines and eventually from fuel cells. Hydrogen is also a possible alternative to conventional transport fuels.

A key uncertainty surrounding the widespread uptake of fuel cells relates to the availability of hydrogen, which does not occur naturally in usable quantities. It will have to be manufactured and fossil fuels are a likely source.

Coal, with the largest and most widespread reserves of any fossil fuel, is a prime candidate to provide the quantities of hydrogen that will be required.

A number of global developments are ongoing in the application of hydrogen technology, in particular for transportation. All of the major vehicle manufacturers now have prototype hydrogen vehicles. Some countries including the USA, Japan and in Europe already have public vehicles operating on hydrogen today. Iceland is leading the way with hydrogen development and plan to operate a hydrogen economy in the coming decade.

Integrated Gasification Fuel Cells
Another option showing promise in the longer term is the integration of coal gasification with a fuel cell. Fuel cells are capable of converting the chemical energy in hydrogen directly into electricity at high rates of efficiency (at least 60%) and with almost no emissions.

Very high temperature exhaust gas can be used directly to drive a gas turbine or combined cycle (gas + steam turbines).



The versatility of coal means it can be transformed into other forms of energy:
• Gases
• Liquids
• Hydrogen
Gasified coal has been traditionally used for lighting and heating both domestically and at a community level. Today gasified coal is used to generate high efficiency clean electricity, produce chemicals as well as form the basis for synthetic oil production.

Coal liquids can be produced directly or indirectly by first gasifying the coal. Coal-derived fuels are sulphur-free, low in particulates and nitrogen oxides and with carbon capture and storage can reduce life cycle CO2 emissions relative to conventional oil production.

Coal could also play an important role in a move towards a hydrogen-based energy system, in which hydrogen is used to produce clean electricity from gas turbines and, ultimately, fuel cells.