A few days ago, we published a about data from physicist and author Joseph Romm stating that hydrogen actually causes more total greenhouse gases than gasoline.
Under Romm's calculations, a regular gas car that gets 40 miles a gallon will spew about 485 pounds of carbon dioxide on a 1,000 mile drive. A hydrogen car will only release water, but making enough hydrogen for a 1,000 mile drive can generate 2,100 pounds of CO2. That's the amount of CO2 that a coal-burning power plant will generate to run the chemical factory.
But one reader pointed out it's an unfair comparison. How much CO2 gets produced in making the gas? That's not included in the above comparison.
"The upstream CO2 from gasoline adds another 20 percent or so about 100 pounds," he wrote. So, in his calculations, the car generates about 600 pounds of CO2, less than a third for a worst case scenario for hydrogen. (Side note: Romm is actually a prominent advocate for alternative energy, but skeptical of hydrogen.)
Of course, the hypothetical can be tweaked. Only about half of the electricity in the U.S. gets generated by coal. Factoring that in brings the comparison closer, although hydrogen still loses out.
Cleaner techniques for producing hydrogen--with microbes, chemical reactions or solar power--can further reduce the delta, or even reverse the results. But these are all in the embryonic and/or experimental stage. At this point it time, it's hard to say if any of them will be commercially viable or better than, let's say, good lithium ion batteries for electric cars.
So the hydrogen debate will continue. The hydrogen trials being conducted by cities will be a great Petri dish to observe the results.