It takes 3 H2 for every one CO2 to make methanol. Why go to the air for co2 there are so many better places to get bulk co2. Seawater if you are close to the ocean would be hundreds of times better. Co2 is a bulk chemical traded ,shipped all over planet most of that comes from brewers, or ethanol fermenter plants at like $50 a tonne it’s ludicrous to spend $600+ to grab it from the air other than to greenwash and virtue signal.
It takes 55 kwh to make a Kg of hydrogen you need three for one vs co2 by the mol of co2 not co2 mass. Why three to one well normally methanol is made with carbon monoxide CO not CO2 and that is CO + 2H2 = Methanol that pesky extra O atom has to.go and that needs another H2 for CO2+H2= CO + H20 than two more H2 for the CO + 2H2 step.
Chemically to make one Kg of methanol you need 126 grams of hydrogen staring at the normal CO point having to turn CO2 into CO add half again as much so 63 more grams for a total of 189 grams per kg.
Methanol is sold by the metric tonne (1000Kg) so a unit of sale or a tonne needs 189Kg H2 per tonne. At 55kwh per kg thats 10395 kWh or 10.3 megawatt hours. Whole sale power at 0400 this morning can in Texas was selling for $17 per Mwh that’s that would be $175 per tonne in energy costs. Plus 1400kg of co2 per tonne at $50 per tonne wholesale co2 prices forget air capture that’s $70 in co2 liquid. So materials is $245 per tonne. The current methanol bulk price is $432 per tonne in the US.
Methanol is 6.63lb/gal...6.63lb is 3kg
So something like 333 gal per tonne of mass. Works out to about $1.29 a gallon at 432 per tonne mass.