[Carlhole]

Autopia

“Urea is the same stuff we use to fertilize our flower beds. It’s a solid that dissolves in water and is therefore easy to move,” Botte told Wired.com. “An electrolyzer built into a car would eliminate the need for a hydrogen storage tank, and with the right partnership, I believe we could have pee-powered cars capable of 60 miles per gallon on the road within a year.”

Well, I don't know about that... I suppose I'd like to see a pee-powered Honda 50 endurance race between competing teams, done in a reality-show style. That would be entertaining - "I want Martha off the team; her pee is too clean, and she don't make that much of it!"

Using renewables to create ammonia is one of Matt Simmons favorite ideas. But he wasn't talking about using piss. Pee Power MUST be possible to some degree which could be calculated but it's silly to suggest the notion of powering CARS with it.

Still, a hypothetical Doom community would probably utilize everyone's collective contributions of urea. The article should have included some chemistry.

[smallpoxgirl]

And you thought car exhaust smells bad now.

[Gerben]

I like it and there's bound to be some application for it (powering your laptop while camping in the wild). But

Her electrolyzer uses a nickel-based electrode to extract hydrogen from urea (NH2)2CO, the main component in urine.

The main component in urine is ... water. 1 liter contains approx. 20 grams of urea. So that's approximately 2% by weight.

Urea has a molar weight of 60. With 4 hydrogen atoms, the weight of the hydrogen in urea is ~7% (asuming you can extract all of it).
So for 1 kg hydrogen (a hydrogen car often contains about 5 kg) you need about 700 liters of urine. A full tank would contain 3.700 liters of urine (~1,000 gallons).

You'll need to concentrate the pee if you want to carry it around. Or even produce the hydrogen in a central facility and sell it to the public. All the pee of a big city is enough for one refueling station.

What you might see is factories using natural gas to make urea, store that in cars and then ehm. "The electrolyzer would have to pull energy from a power source like a battery in order to produce hydrogen for a fuel cell."
I'd like to know the power ratio here: how much of the power you can obtain from hydrogen is wasted extracting it from urea?
Anyway: the advantage of urea is that it has a 15,000 times higher density than hydrogen. The energy density however is still less than that of gasoline.

Ureum can be produced using (lots of) sustainable energy. As long as we are using natural gas to make ureum it's cheaper and more efficient to power the car using a battery or CNG. (A thing that can also be said for hydrogen btw.)

[templar]

It puts a smile on my face to think I could drink a lot of beer at night and fill my car up in the morning.

[Keith_McClary]