Urine as an energy source?
Maybe one day we’ll be able to use urine as an energy source for Gabriola. The Toronto Sun reports that Urine could be energy source of the future.
Discovery.com has more: Urine: A ‘Clean’ Energy Source.
Using a nickel-based electrode, the scientists can create large amounts of cheap hydrogen from urine that could be burned or used in fuel cells.
One cow can provide enough energy to supply hot water for 19 houses,said Gerardine Botte, a professor at Ohio University developing the technology. [continue]
Who would have guessed? Until the technology comes our way, consider these blog posts from our archives:
Filed in environment 6 Comments so far
6 Responses to “Urine as an energy source?”
Nick on 30 Aug 2010 at 12:31 pm #
I’m not sure I get the whole story from all the newspaper hype. If you think first about water, the idea is that you use electrical energy to make hydrogen and then you burn the hydrogen to provide mechanical power. Since the input and output of this process are both water, all the energy for this must be coming from the electrical supply. The hydrogen is just a storage medium. What the researchers seems to be saying is that if you use electrical energy to make hydrogen from urea and then you burn the hydrogen to provide power, you get more energy out than you would with water. This makes sense because what you are in effect doing is burning urea. What I can’t find out though is how much of the mechanical power is being derived from burning urea and how much is being derived from the electrical supply needed to generate the hydrogen. It may be less than is needed for water but it can’t be zero. Help!
specialk on 30 Aug 2010 at 6:24 pm #
Hey Nick…
“What I can’t find out though is how much of the mechanical power is being derived from burning urea and how much is being derived from the electrical supply needed to generate the hydrogen.”
Sounds like an experiment you could easily conduct in your basement, no?
Nick on 30 Aug 2010 at 8:20 pm #
OK, I think I’ve answered my own question – I often talk to myself. Since the electrolytic cell potential of the urea solution is 0.23V (or whatever) compared to 1.23V, the energy input for the same amount of hydrogen (same number of electrons, hence current) as water is presumably 80% less. Which raises the question, where does the excess energy go when you use water?
The answer is in the chemical equations. The output from a urea cell (NH2)2=CO is nitrogen, carbon dioxide (greenhouse gas alert), and hydrogen, while from the water cell it’s just oxygen and hydrogen. So in principle, you can use the oxygen from the water cell to oxidize carbon, with a release of yet more energy, but there’s nothing you can do (easily) with the output of the urea cell. The urea cell just appears to require less energy than water because it produces some by itself by oxidizing carbon (actually carbon monoxide), which the water cell does not. Some reports suggest you don’t need to worry about the CO2 as a greenhouse gas as it is absorbed by the potassium hydroxide used in the cell. This is a disingenuous suggestion because it ignores the fact that potassium hydroxide is largely produced by electrolysis and so requires electrical energy to produce. I’m not saying the idea is…er…uhm….wet, but I won’t be planning to go into the village by taking a diuretic anytime soon. A good technical resource is http://etd.ohiolink.edu/send-pdf.cgi/Singh%20Deepika.pdf?ohiou1258349080 .
Nick on 31 Aug 2010 at 10:28 am #
Just to add to this monologue, with the honourable exception of specialk, one could argue that the greenhouse gas worry is unwarranted because urea is an organically produced carbon compound and thus part of a natural carbon cycle not involving fossil fuel. Left to be disposed of in the usual way, urine would produce CO2 anyway. A footnote however is that urea is produced synthetically and widely used in agriculture as a fertilizer. Synthetic urea is made from ammonia and carbon dioxide, and ammonia is made from natural gas, so the chances are good that the carbon in synthetic urea is ultimately from a fossil fuel and it will therefore in a urea cell generate a greenhouse gas. I’m having a hard time deciding if the legs this story has is because it’s about pee, or because we’re all looking for a quick, simple fix to save the world.
Andrea on 31 Aug 2010 at 1:34 pm #
Nick, I suspect your chemistry is a bit less rusty than mine (no pun intended) so I’ll ask this question – when I read your comment I had to wonder what would happen to the N? I assume it won’t just stay as N, but will combine with something. Would it turn into NH-something (ammonia/um) or maybe oxidize into NO-something? I wouldn’t expect either of those to be particularly environment-friendly options – in air they are components of smog, and in water they may be excess nutrients that lead to plankton blooms etc. On the other hand, how stable is urea? If left to itself in the environment would it react and turn into these other N-compounds in any case? In which case there may be no environmental down side to harvesting the energy released by the conversion?
Nick on 31 Aug 2010 at 10:16 pm #
Hi Andrea. You really need to ask a microbe as to what happens to urea in the natural world—urea contains lots of energy and there are always microbes and other “organic things” around to exploit sources of energy. The common breakdown products in the natural world of urea (NH2)2CO are, as you might guess, the gases ammonia NH3 (phew! the smell) and carbon dioxide CO2. Some microbes will push this even further and get energy by converting ammonia to nitrite NO2, and still others will go on to squeeze out the last bit of energy by converting nitrite to nitrate. Plants readily absorb ammonia and nitrate, so it all goes to a good cause; however, excesses of these in waterways from fertilized fields is a major source of agricultural pollution. Ammonium nitrate is also a source of nitrous oxide, which is a very effective greenhouse gas. The urea cell appears to produce nitrogen, and nobody but microbes can complain about that.