What is coal seam gas (CSG)?

Coal Seam Gas (CSG), or coal bed methane (CBM)
as it’s sometimes known, is a form of natural gas,
typically extracted from coal seams at depths of
300‑1000 metres. It is a colourless, odourless, mixture
of a number of gases, but is mostly made up of methane
- it’s usually more than 95 per cent pure methane.
CSG was made over 200 million years ago when coal
was being formed, and has been held in the coal since
then by water pressure. To get at the gas you first need
to remove the water. This reduces the pressure in the
coal seam enabling the gas to flow.