3 ms·

6.4 trillion liters of urine may become viable biofuel

31 points by ukdm 15y ago

ars 15y ago
I can't read the actual paper, so I don't know what the bacteria is eating - pretty much the only thing in any quantity in urine is urea (and urea is more valuable as fertilizer). But I will point out that if you have sugar in your urine that is a severe health problem called Diabetes mellitus. Mellitus means sweet, specifically sweet urine which was how Diabetes was originally diagnosed.
- deleted 15y ago
  [deleted]
- hugh3 15y ago
  Reading the actual paper now. Important bits: The composition of excreted normal human urine, is:4 urea 6–18 g day−1, uric acid 1.8 g day−1, creatinine 0.5–0.8 g day−1, amino acids 0.12 g day−1 and peptides 0.5 g day−1. Variable amounts of lactic acid, citric acid, bilirubin and porphyrins, ketone bodies (aceto-acetic acid; β-hydroxybutyrate; acetone), and small amounts of hexose (glucose) and pentose (arabinose) sugars may also be present in normal urine. When considering the bio-available organic content of excreted urine, compounds such as urea and uric acid are not included, since they cannot be utilised as carbon-energy (C/E) sources by the microbial community inside an MFC. In total, the dry weight content of metabolisable organic substrates, within excreted urine, was estimated to be 0.78 g/human/day.4 Due to the insignificant amount of lipid in urine, this has also been ignored. Therefore, the mean calorific value of 1 g of carbohydrates, peptides, proteins or amino-acids (as metabolisable substrates within urine) has been estimated to be 2.08 kcal Which, if I'm reading it correctly, means you can extract 1.62 kCal of energy per day from your urine (assuming 100% efficiency). This is not a lot. Even if you collected all the urine from a city of one million people, it would be roughly 80 kilowatts.
  - ars 15y ago
    Thanks for reading it! It would take a lot more than 80 kilowatts to even collect that much urine, much less actually do anything with it. This is such a non starter I wonder why they even thought about it for longer than it took to lookup the composition of urine.
Tloewald 15y ago
The url craps out on my iPad so... Meh. And what the other poster said ... It's hard to imagine urine being a better fuel than it is fertilizer.
tryitnow 15y ago
It just seems like there wasn't much critical thinking in this article. It doesn't give us an idea of the real magnitude of the potential energy that could be produced this way. For example, "6.4 trillion liters" is just a headline grabber (and an effective one), but if it only produces a trivial amount of energy, who cares? It also doesn't mention that there are useful alternatives that may be more economically worthwhile for waste (see the other comments here).

31 points by ukdm 15y ago

ars 15y ago

I can't read the actual paper, so I don't know what the bacteria is eating - pretty much the only thing in any quantity in urine is urea (and urea is more valuable as fertilizer). But I will point out that if you have sugar in your urine that is a severe health problem called Diabetes mellitus. Mellitus means sweet, specifically sweet urine which was how Diabetes was originally diagnosed.

deleted 15y ago
[deleted]
hugh3 15y ago
Reading the actual paper now. Important bits: The composition of excreted normal human urine, is:4 urea 6–18 g day−1, uric acid 1.8 g day−1, creatinine 0.5–0.8 g day−1, amino acids 0.12 g day−1 and peptides 0.5 g day−1. Variable amounts of lactic acid, citric acid, bilirubin and porphyrins, ketone bodies (aceto-acetic acid; β-hydroxybutyrate; acetone), and small amounts of hexose (glucose) and pentose (arabinose) sugars may also be present in normal urine. When considering the bio-available organic content of excreted urine, compounds such as urea and uric acid are not included, since they cannot be utilised as carbon-energy (C/E) sources by the microbial community inside an MFC. In total, the dry weight content of metabolisable organic substrates, within excreted urine, was estimated to be 0.78 g/human/day.4 Due to the insignificant amount of lipid in urine, this has also been ignored. Therefore, the mean calorific value of 1 g of carbohydrates, peptides, proteins or amino-acids (as metabolisable substrates within urine) has been estimated to be 2.08 kcal Which, if I'm reading it correctly, means you can extract 1.62 kCal of energy per day from your urine (assuming 100% efficiency). This is not a lot. Even if you collected all the urine from a city of one million people, it would be roughly 80 kilowatts.
- ars 15y ago
  Thanks for reading it! It would take a lot more than 80 kilowatts to even collect that much urine, much less actually do anything with it. This is such a non starter I wonder why they even thought about it for longer than it took to lookup the composition of urine.

Tloewald 15y ago

The url craps out on my iPad so... Meh. And what the other poster said ... It's hard to imagine urine being a better fuel than it is fertilizer.

tryitnow 15y ago

It just seems like there wasn't much critical thinking in this article. It doesn't give us an idea of the real magnitude of the potential energy that could be produced this way. For example, "6.4 trillion liters" is just a headline grabber (and an effective one), but if it only produces a trivial amount of energy, who cares? It also doesn't mention that there are useful alternatives that may be more economically worthwhile for waste (see the other comments here).