looks like shale gas is ready to fly, page-12

No its not dirtier than coal.

Some experts go on about it maybe be dirter than coal but what they are saying is the raw Methane if leaked into the atmosphere is worse than coal re greenhouse gas. Methane can come from the fracking process and escape.
These experts mostly talk about it in term of USA fracking which is shallower.

This really doesnt apply to BPT copper shale as its way to deep to come up from other sources.

Methane in its raw unburned form is around 5 times worse as a greenhouse gas. Thats why cows and camels are on the Hit list.

Once burned Natural gas methane has less than half the Co2 emmisions as coal.

Natural gas is also more heat efficent than coal. (You need relatively less to produce the same heat )

Summary

GAS IS GOOD.