The words "Hydrogen Economy" have been banted around for years now by journalists enjoying the idea of replacing existing fuels with hydrogen gas, because the product of burning it is water. Perfectly clean water. No carbon dioxide. No noxious smoke. Just water.
Okay, but the planet earth doesn't have hydrogen spewing out of the ground. All our hydrogen is locked up in more complicated molecules, which are more stable than the gas itself. Rending them apart would cost energy, not release it. So hydrogen is more a store of energy than a source. Energy journalists sulk for a bit before looking again at solar panels and sighing wistfully.
Then, a week ago, a scientist found a more efficient, if infinitely grosser source. Pee. Human urine's urea and other dissolved acids produce hydrogen with a quarter the voltage required to break down pure water, if a nickel electrode is used. The waste products of this are nitrogen gas and potassium carbonate (aka "Pearl Ash"), both harmless to the environment and other humans.
This is not only useful as an energy source. Raw sewage is a major threat to the health of everything in its vicinity. Bacterial breakdown often includes toxic amounts of ammonia, poisonous nitrogen-based compounds, and horrible horrible smells. Anyone or anything breathing this becomes terribly sick. In addition, the waste products of this are industrially useful. Especially the phosphorus, whose deposits in nature are becoming rarer and more scattered as industry and agriculture demand more and more tons of it.
Of course, this leaves me with the silly thought of driving about, noticing I'm low on fuel, and stopping in for a big gulp and a curtain to fill up. Or a drunken frat boy peeing in my gas tank as revenge for a perceived slight, and me appreciating the free fuel instead. And the most ridiculous part would be soap and glass companies sweeping the streets of pearl ash, which falls out of the exhaust pipe of these cars.
Actually the inevitable jokes are probably worse than any of the real consequences. At least trucker bombs are a thing of the past.