You have to input a fixed amount of work through the compressor shaft to compress a known amount of gas from a defined suction pressure and temperature to a known discharge pressure and temperature. I can generate that work with an internal combustion engine, an electric motor, a steam turbine, or a water wheel. In every case the amount of work input is fixed. The cost of that input is quite variable.
If I am running a gas turbine to generate electricity and I'm willing to spend the capital to recover the waste heat, then using steam is very inexpensive while using the electricity directly to run the compressor has a high opportunity cost (the power can be sold if not used). If I have to burn fuel to generate steam then steam turbines can be quite expensive to operate.
There are situations where I can use gas that would otherwise be vented to run an internal combustion engine, in countries with a carbon tax, the government is paying me to use that fuel instead of venting it, very cheap indeed.
Bottom line of the above discussion is that choice of driver for a particular compression operation in a particular location at a particular time is a complex economic analysis that does not lend itself to rules of thumb. You have to do the analysis honestly, without bias to decide what makes the most economic sense. Once you have that number it is quite appropriate to apply personal, corporate, or regulatory biases to add the consideration of intangibles--with an honest cost breakdown you can determine the cost of indulging in the biases to decide if pandering to them is justified. For example, if the NPV of your electric driven compressor is 80% of the NPV of a gas turbine driven compressor, but adding the turbine would increase the emissions output enough to force the entire plant into a non-attainment status (with accompanying potential for fines, capital expenditure required for other equipment, and bad press) then the lower NPV could easily be justified. In the same example, if the NPV of the electric was 10% of the gas turbine even considering fines and required capital expenditures then accepting the bad press might just be a cost of doing business as you install the turbine.
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"