U.S. firm mulls building geothermal power plant from Sidoarjo mudflow

By the time the mud hits the surface it has flashed off most of it's energy - thus that great plume of steam that you see when you pass Porong. You need to get it at pressure , and the easiesy way to do that is to tap it a depth - you have a couple of alternatives, create the superheated steam underground or take the mud somewhere to recover it's entropy. The first option is much easier, you certainly don't want to be messing around with mud at high temperature.

You're looking at something like 25000 tonnes of steam, which of course means 25000 tonnes of water per hour for the output they are looking at.