I have just finished building a simple LPE, but have no means to power it. I live on a farm and have access to a small air compressor, would that work?
Since the compressor produces compressed air, it would certainly work, given you build adequate fittings and take precautions against overpressurization.
LEGO pneumatics have been tested to withstand as much as 8 bars or 120 psi, but you definitely should plan with safety margins. If your compressor can produce higher pressures, I'd suggest building in some kind of release or auto-shutoff valve to prevent damaging the LEGO parts.