Tuesday, December 6, 2016

Pee Power: The Dream Is Dead

Many times in the energy investing racket you have to face reality and in the words of Edward M. Kennedy upon losing the Democrat Party nomination in 1980, say:
"...For all those whose cares have been our concern,
the work goes on, the cause endures,
the hope still lives, and the dream shall never die."*

-Ted Kennedy
Other times, you just say "Doesn't work" and move on.

From Daily Tech, Oct. 19, 2015:

Debunked: Beneath the Lies, Nigerian "Pee Generator" Is Still Pissing Into the Wind
Hydrogen doesn't grow on trees... well not free hydrogen gas, at least 
One of my friends on Facebook, Inc. (FB) shared second hand a piece of amazing news. According to his friend's post a group of Nigerian girls has invented a "pee generator" which takes a couple cups worth of urine, filters out the contaminates and turns the water into pure hydrogen gas which is then dried/stored in borax, before being piped to a small portable combustion generator.

Hmm, if true this is the best thing since urine harvested stems cells were used to regrow neurons and more! What can't urine do? Sort of gives a whole new meaning to "thy cup runneth over", right?

The only problem, as I pointed out to my friend, is that it's unfortunately malarkey (for the most part). Yes, it's certainly an entertaining science faire (or faire?) experiment, given that it potentially should work. And yes, there's perhaps a small amount of useful purpose amidst the misrepresentations. But when it comes to the solution to the world's small scale power needs, pee is not some some magical panacea.

I. Pee Power: The Golden Years 
It's somewhat amazing that this story is still making the rounds.
The probable inspiration behind this pee pandemonia likely lies in a 2010 presentation delivered at Proceedings of the 12th International Conference on the Synthesis and Simulation of Living Systems (aka Artificial LIFE XII or A-LIFE XII (2010)). Given by Professor Ioannis Ieropoulos of the University of the West of England's (UWE) Bristol Bioenergy Center (a sub-lab of the Bristol Robotics Laboratory (BRL)) the talk discussed using a microbial fuel cell (MFC) to produce hydrogen to power a robot [pg. 749 PDF].

A little over a year later in Oct. 2011 Prof. Ieropoulos published a followup paper [PDF] on the MFC which carried an unexpected twist. In terms of unexpected, yet novel turns in science few can claim rival that which the UWE professor's work took -- suddenly his research hatched a brand new field: "urine-tricity". The premise was (and is) both sensational and simple -- push pee into a colony of bacteria in a fancy jar (of sorts) and let them digest it, building up a low level current in the process which is stored in a battery. 
Urine -- fuel for the future?
Urine -- fuel for the future? Urine --fuel for the future, or pissing into the wind? [Image Source: RSC] 
In the perfect world this would be an epic win. While the amount of power produced by a urine fed stack is minute -- roughly 2 to 2.5 milliwatts in more recent iterations -- that's enough to trickle charge (no pun intended) a microelectronic device in a remote setting. Typically that would require a noisy, wasteful, smelly, and worst of all expensive fossil fuel generator. 
MFC The pee microbial fuel cell (MFC) (well, urine MFC, formally speaking) is a good idea, but it's not all there commercially speaking. [Image Source: Phys. Chem. Chem. Phys.] 
But, the devil, of course, is in the details. While the cell itself was cheap to construct (being comprised in part of a clay vessel), the hard part would be getting and keeping alive the bacteria colony. A recent publication describes the process as follows
"Both types of MFC were inoculated from anaerobic sludge, provided by the Wessex Water Scientific Laboratory (Cam Valley, Saltford, UK), which was supplemented with acetate (as the source of carbon energy) and yeast-extract (as the source of minerals/nutrients). The acetate–yeast extract was added into 1 L of anaerobic sludge and consisted of 25 mM sodium acetate (Fisher Scientific, UK) and 0.1% w/v yeast extract (Oxoid, UK) with no added buffers and a pH of 6.7.

Initially and for approximately 1 week, the ceramic MFCs were maintained under batch mode conditions, after which they were switched to continuous flow, using a Watson Marlow 205U peristaltic pump (Watson Marlow, UK). The flow rate used was 250 mL min1 (hydraulic retention time – HRT = 3 hours, 48 minutes) and the same flow rate was subsequently employed for urine. The EcoBot MFCs were also maintained in fed-batch mode with 3 mL of either acetate–yeast extract or urine fed twice a day, resulting in an HRT E 24 hours." doi: 10.1039/C3CP52889H; Physical Chemistry Chemical Physics (PCCP); Jul. 2013
At the risk of playing contrarian I would point out that there's one thing glaringly absent from most of these publications: the lifespan of the bacteria. Most bacteria are short-lived and seek to live in a specific sort of environment. In this case it's clear that the bacteria colony can last at least a week and only requires yeast (not super expensive), water, and acetate (which can be made frugally from baking soda (sodium bicarbonate) and vinegar). 
robots to pee
From robots to pee research funded by Bill Gates, Professor Ioannis Ieropoulos has seen his career at UWE take an unexpected and somewhat sensational diversion. [Image Source: UWE/Bristol]
The issue is not so much in the media (which certainly is doable in a remote setting and not overly rigorous, but in the tolerance to changes in the cell, particularly in terms of temperatures and pH. Remember, these remote regions don't have air conditioning in the summer or central heat in the winter. So keeping your pet bacteria alive is challenging.

And then there's the real kicker -- the pump. The bacteria, after all, don't like to live in stagnant water. They like a nice gentle flow and continuous twice daily injection of nutrients. Those luxuries are provided via Watson Marlow 205U peristaltic pump [brochure; PDF]. Such pumps typically have motors that start at a minimum of 5 watts.

So your bacteria colony, which outputs 2 to 2.5 milliwatts of power needs something on the order of two thousand times that much power to continuously circulate its media.

"Uh oh."...

Additionally the four-year, EU financed multidisciplinary ValueFromUrine Project wrapped up August 31.

*That address to the Democratic National Convention was ranked as number 74 of the top 100 American speeches of the 20th century.