A simple high-school electrochemistry question for you smart ones: how do you make that excellent, but tricky, fuel for your car, hydrogen?
Simple. You start with plain old water; you dip two terminals from a battery at the ends of the tank and turn on the current. Something starts bubbling at the terminals, hydrogen at one, oxygen at the other. You can use the hydrogen to make your car go, sell the oxygen, perhaps, to the nearest hospital. It’s a great little system, the only problem being that it takes at least 1.23 volts to split the water molecule and electricity costs money.
Okay, forget the water. Let’s electrolyze a different chemical liquid, say urine.
Human urine takes only 0.37 volts to electrolyze. This cuts your power consumption down to not much more than a quarter, and the process is now economical. What makes the difference is that urine contains urea, and a molecule of urea contains four of the hydrogen atoms that constitute your electric current — twice as many as a molecule of water — and the bonds that hold the molecule together are weaker.
So, supposing you want to start building your plant for peepee power right now, where do you get your urine? You might think that that’s a silly question — nearly 7 billion humans alive on the Earth, and every one of them generating your new motor fuel for you every day — but you may have to go to some trouble to get what you need. No, you can’t just pipe your sewage into a tank and run a current through it. Sewage is contaminated with many other materials, and the worst of them for this purpose is plain old water. Any flush toilet dilutes the urine drastically, and thus also seriously dilutes the urea it contains, so much so that you might as well use plain water to begin .with.
There are various solutions to the problem of the urine collection. One was invented for us by the ancient Romans. They liked to wear white woolen garments, but those garments got dirty and couldn’t be laundered in water because they would shrink. Plain urine was fine to wash them in, though, so to provide their cleaning liquid, those old Roman dry cleaners put barrels out at street intersections, with ingratiating little signs urging those who had to go to use the barrels.
Of course, some neighborhoods might not care for that sort of public display. Fortunately, there are other options. The urine doesn’t have to come from human beings. Any large mammal will do. The particularly placid cow would be close to ideal. And how do you persuade your herd of cattle to pee in a barrel? You don’t.
There is a useful bit of minor surgery widely in use for elderly male humans whose prostate has grown so big it interferes with their urination. One end of a catheter is inserted directly through the skin into the gentleman’s bladder, the other end leads to a collection vessel of some sort. From then on the man never has to dash for a public urinal, and his own urine arrives at the electrolysis plant in a nearly pristine condition. (You save a bundle on water bills, too, since from then you never have to flush for pee.)
See how easy it is to solve some pretty big problems if you want to make the effort?
* * *All the Lives He Led — is set partly in Pompeii, and I’ve done a lot of writing about those Romans at other times as well.