Well I have heard a lot about coal seam gas in the news lately and around the rural traps but don't actually know anything about it.
After a little bit of research, here is what I have found:
What is coal seam gas? - it is a methane that is associated with coal. The gas is released from the coal seam when the pressure is reduced, usually through the extraction of the water associated with these coal seams.
Why is it important? - it is an energy source, similar to natural gas (only difference is where gas is stored naturally, apparently natural gas is associated with sandstone or similar rock).
Some of the reported potential environmental impact? - water with undesirable concentrations of dissolved substances (not sure what the substances are though), depression of aquifers.