> how much would it cost to develop significant PV-powered electrolysis-and-Sabatier-process plant in any of the big coastal deserts, for exporting methane? Wh

> how much would it cost to develop significant PV-powered electrolysis-and-Sabatier-process plant in any of the big coastal deserts, for exporting methane? What are you thinking about as the carbon source? If coal, then this has been commercially viable for decades. In North Dakota there is a 1.5 gigawatt installation running since 1984. That one uses electricity from coal power IIUC, but today PV is cheaper than coal for electricity. If you are talking about CO2 from direct air capture, the optimistic cost estimates of your CO2 feedstock are around $600/tonne. 1 tonne of CO2 gives ~137 kg of methane at 100% reaction yield, due to the molar weight ratio of CO2 to CH4. So per tonne of methane produced, the CO2 cost alone is above $4000. For comparison a tonne of natural gas in the US today costs between $500 and $1000 for the end user. This means that CO2 capture from air needs to become two orders of magnitude cheaper than today before this scheme works out. I would say hydrogen electrolysis and then liquefaction for large scale distribution/export is way more realistic. This is what the EU seems to be going for together with Northern Africa.