That purification is much easier to do at a stationary source than in each and every vehicle.

That CO is not going to come out the exhaust. In an IC engine, it will get combusted. The big advantage to H2 is the fuel cell engine's efficiency (~50% instead of 28-30 for an IC engine). Unfortunately, the fuel cell is intolerant of H2 below 99.999% purity. Hydrogen purification was what I specialized in.

The problem with (liquid) hydrogen is not engineering, it's straight physics. Liquid hydrogen has about three times less energy per gallon than gasoline. So if you get 30 miles/gallon in a gasoline car, you'll get only 10 miles/gallon of liquid hydrogen (or 2.5 to 5 miles per gallon of compressed hydrogen). Who wants to be driving a hydrogen tank with wheels. The hydrogen tank also has to be heavier, because hydrogen has to be kept under pressure. That puts also a limitation, because you can make a car lighter to get more miles per gallon, buy necessarily cars have to be heavier than if they had just a regular gas tank.

Another issue is that hydrogen is not a source of energy, it is only a means of transporting energy. It has to be made using electricity or another source. If made from methane, the process creates CO, which is burned to CO2. The processes that generate hydrogen are not carbon neutral. You might as well get more energy and less pollution (if you think of CO2 as that) by burning the fuel directly.

From the chemical reaction listed above, carbon monoxide is produced. How much, and how does this figure stand up compared to existing internal combustion engines?

Electrolysis is more energy intensive and about 2.5 times more expensive than using gasoline. Astronauts use electrolysis and capture the oxygen gas for breathing, so your last statement is certainly plausible, Robbie. It just isn't economical.

There is. It's called a fuel cell engine, but to do use it, the H2 must
be VERY pure. This is possible, but kind of expensive.

You should be skeptical. There are several levels of possible tradeoffs between environmental friendliness and cost in this problem. The technical issues are solved. The economic ones are solved about as much as they will be, but not quite to most people's satisfaction. One of the questions I ask my students is how much on a percentage basis are you willing to pay for a completely environmentally friendly fuel. The vast majority say that they wouldn't pay any more. A few would pay up to 30%. I'll gladly absolve them of their guilt if they pay me enough for it - and have done so in the past.

It's not distilled from natural gas. The reaction is steam reforming of methane (the major component of natural gas).
CH4 + H2O --> CO + 3 H2
followed by several other reactions and purifications.

The key player in Honda's group that started Honda's H2 efforts is Cory Phillips.
When I was a grad student, one other grad student and I trained Cory
while he was an undergrad at Michigan. He's not John Galt, but you could
tell he was going to be quite outstanding. I certainly put him at least at my level.

Gasoline powered vehicles make more sense in the short term. If we have to make our own Atlantis, this is a viable option that will get us to where we need to go. I've got it covered.

Cool. Do you know if they have a scalable, carbon-neutral way to generate the hydrogen in the first place? Even if they don't, I'm happy even to see one piece of the puzzle.

Plant waste to energy is scalable and carbon neutral. I had a company doing that until we sold it when Obama was the pied piper that took our customers toward solar energy instead. So we shrugged. Don't worry. Atlantis will have plenty of energy. See my other comments in this thread.

Hydrogen fueled fleets of large vehicles (buses, trucks) have been as economical as running off of diesel since 1998. I worked in the hydrogen industry from 1997-1998 and did hydrogen research and development projects from 1997 to 2006. The economics of automobiles have always been limited by the weight and cost of both the fuel cell (twice as efficient as the internal combustion engine) and the hydrogen storage system. If you are willing to pay about 30% more for both the vehicle and the fuel, hydrogen fueled vehicles are a reasonable option. I can make hydrogen from just about any sort of hydrocarbon fuel or from electricity. You do not need to worry about energy supply for the Gulch, when it gets to that point. A competitor will probably come up with a cheaper option, but this will be part of my Gulch solution when the time comes.

That SF "blanket of brown disfiguring smog" is not from the cars but rather from the residents' political leanings :-)

Wow...costs less than gasoline, no emmissions....it mus be a plot of those evil Koch brothers and the Bushies that is why we don't have this already...!!!

Once again we are asked to totally suspend belief and common sense to believe another pie in the sky story. The only thing positive about this technology is that we could create hydrogen generation plants at these ridiculous windmill and solar farms and use up the surplus energy which is produced due to the lack of control as to when the power is produced. Also these wind farms tend to be in the middle of frigging nowhere so you have at least a 10% transmission loss in getting the power to somewhere it is actually needed. Hydrogen thus produced could be thus be trucked where it is needed.

The most cost-effective method of distilling H2 is directly from natural gas. Honda has created a unit that can produce H2 in your home.

more GOVERNMENT involvement in what should be private investments. as we know GOVERNMENT involvement means WASTING taxpayer dollars. IF there is ever going to be a market for these types of vehicles the car buyers will see the benefits and want them which in turn will cause some investor to see the potential and build fueling stations. the future is GASOLINE powered cars.

Burning hydrocarbons, in an ideal world w/o incomplete burning, turns H[x]C[y] --> CO[2] + H[2]O + energy. You get H[2]O either way.