I always thought burning garbage is really bad for the environment. Aren't there dangerous chemicals that are released if the garbage is not incinerated?
That said, providing heat is the best use for this since even low grade heat (100 - 150 degrees C) is usable for heating buildings and water for washing etc. But you can't pull a lot of electricity out of it with steam turbines.
It’s still worse for the air than putting the garbage in landfills, but landfills have their problems too.
If you don't turn your waste into heat, presumably, you would dig up oil, refine it, transport it to where you need it and burn that oil. Chances are that produces more CO2 than the collection and burning of waste fairly close to where it is produced (transporting waste from Italy to Norway would probably be a different matter)
Also, the controlled burning of waste (typically at high temperatures) can break down molecules that, if dropped in a landfill, may make it into the atmosphere or ground water.
More arguments fore/against at http://en.wikipedia.org/wiki/Incineration#Debate. I find it telling that quite a few of the 'against' arguments compare incineration not with landfills, but with other technologies/solutions.