Of course, one drawback is that coal-based methanol ends up with something like twice the net CO2 emissions per vehicle mile as gasoline. Ethanol can be worse too if you fuel steps in the processing (much more energy intensive than refining petroleum) with electricity from coal, or coal directly. That's a pretty huge drawback.

Zubrin is also more positive here on the toxicity/fire danger of methanol than many other analysts. In doing some quick googling, I found a BMW report that they decided against promioting methanol engines due to the fact that they'd only be servicable with specialized equipment and protective suits due to the toxicity of methanol fumes. That's certainly consistent with what I was reading when I was doing energy research for a consulting firm back in the mid-90s.

Ethanol is much more attractive as a fuel, but as Zubrin acknowledges, you quickly run into limits on arable land domestically. Even with coal, massively increasing consumption will require opening new mines and building a LOT more rail lines (the system is at full capacity now moving coal), which might push up the cost of coal significantly.