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  (Source: Warner Bros Pictures)
We won't ask where the inspiration for this idea came to the research team

Sewage sludge is a major issue for the massive metropolitan areas that are increasingly permeating our globe.  Sludge, the leftovers of wastewater processing, is largely the remains of human fecal matter.  

But some researchers are devising creative uses for the bowl movement brew.  There's a researcher in Japan who's supposedly working to turn sewer sludge into protein burgers.  And now a team of researchers in South Korea has suggested that producing biodiesel from sewage sludge may be cheaper than making it from spent food oil.

The study was led by Eilhann Kwon of the Research Institute of Industrial Science and Technology.  He reasoned that sewage sludge was rich in lipid content, so why not try to turn it into biodiesel -- whose starting component is more typically the lipids found in various waste oils (think used french fry oil).

Sewage sludge lipids are produced when aerobic bacteria in sewer drainage convert pockets ("moieties") of methane (CH4) and carbon dioxide (CO2) into lipids, which are then converted to energy.  Some of the lipids accumulate in the bacterial bodies which litter the drainage, hence the drainage can become relatively lipid rich.

Using n-hexane Professor Kwon extracted these lipids from dried sewage pellets.  The team found that sewage has 2,200 times more lipid per gram than soybeans -- which are considered a fairly "oily" crop.  And extracting those lipids cost a mere $0.03 USD per liter, versus $0.80 per liter of soy oil.

Soybean Oil
Sewage often has thousands of times the amount of lipids per gram as soybean oil and can be produced at a fraction of the cost. [Image Source: ThinkSoy]

So why hasn't this been done before?  Well it turns out fatty acid impurities also lurk in sewage, and foul the biodiesel catalytic conversion process, which involves combining the lipids with methanol.

To solve that problem the team came up with a non-catalytic process that uses heat, rather than a catalyst, to drive the reaction to completion.  The new process also increases the surface area involved in the reaction to further accelerate the reaction.  To do this it traps the reaction ingredients in a porous material -- activated alumina.

In a test, with a reactor heated to 380 °C, with excess carbon dioxide present, a 98 percent conversion rate was achieved.

Sewage to diesel
In lab tests, 98 percent of sewage lipids were converted to biodiesel using the new process.
[Image Source: ACS]

Professor Kwon hopes to move aggressively to offer the new waste salvage technology to sewage processing plants.  To do that a desiccation (drying) area would be needed, and extraction facilities would need to be added.  But Professor Kwon believes these additions could be paid off in a matter of years, yielding both a profit and environmental gains.  He comments, "Waste is not simply waste—it can be converted into useful resources like biodiesel."

The new method has been published [abstract] in the peer-reviewed journal Environmental Science Technology.  Rafael Hernandez of Mississippi State University praised the work in an interview with Chemical Engineering News, commenting that the results were "very encouraging" while cautioning that quality of waste varies from location to location and amongs given batches at a particular location.

Sources: Sewage, Chemical Engineering News

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Sorry, I can't resist
By DiscoWade on 8/31/2012 6:44:42 PM , Rating: 5
If UPS uses this technology in their trucks, it will give new meaning to their slogan "What can brown do for you?"

If the highway patrol uses this technology in their cars, they can be called Pooper Troopers.

If this technology is used in a scooter instead of put-put engine it will have a poot-poot engine.

RE: Sorry, I can't resist
By amanojaku on 8/31/2012 7:39:19 PM , Rating: 4
It's time has finally come. Behold! The Poo Choo Train!

RE: Sorry, I can't resist
By StevoLincolnite on 9/1/2012 12:29:48 AM , Rating: 3
It's going to be a shitty job for whoever has to gather up all the human waste to turn it into fuel.

RE: Sorry, I can't resist
By jeffkro on 9/1/2012 1:50:28 AM , Rating: 2
Pretty sure a lot of plants already turn the methane output by the waste into electricity.

By Dr. Kenneth Noisewater on 9/1/2012 5:54:34 PM , Rating: 2
RE: Sorry, I can't resist
By wordsworm on 9/2/2012 1:02:31 AM , Rating: 3
It makes me wonder: how many miles could an average dump achieve? Does anyone know what the bi-product would be after the process has been completed?

Sh!tters Full
By btc909 on 8/31/2012 6:31:02 PM , Rating: 3
Ellen: What are you looking at?
Clark: Oh, the silent majesty of a winter's morn... the clean, cool chill of the holiday air... an a$$hole in his bathrobe, emptying a chemical toilet into my sewer...
[Eddie, in the driveway, is draining the RV's toilet]
Eddie: Sh!tter was full.
Clark: Ah, yeah. You checked our sh!tters, honey?
Ellen: Clark, please. He doesn't know any better.
Clark: He oughta know it's illegal. That's a storm sewer. If it fills with gas, I pity the person who lights a match within ten yards of it.

RE: Sh!tters Full
By Mitch101 on 8/31/2012 8:57:06 PM , Rating: 2
Man I wish Randy Quaid didnt go bonkers.

Star Whackers
Film actor Randy Quaid and his wife Evi's detailed account of how Hollywood assassins have been out to kill them for over a decade.

Get better Randy I miss you as a comedic actor.

The Smell
By Hellfire27 on 8/31/12, Rating: 0
RE: The Smell
By Gondor on 9/2/2012 3:50:17 PM , Rating: 2
A fact: exhaust of a vehicle running on processed cooking oil smells like a huge fryer (think: fries or donuts). Older diesel cars (such as VW Golf from the 80s/90s with their atmospheric diesel engines that came before the introduction of TDI engines) run on that stuff and it doesn't take much in the way of chemical processing to make it work, no matter how foul the oil you're starting with.

A question: what does the exhaust of a vehicle running on human poop smell like ?

RE: The Smell
By Captain Orgazmo on 9/2/2012 5:47:39 PM , Rating: 2
Why don't you pinch one off into a toaster, and tell us all!

Cool idea
By Ammohunt on 8/31/2012 6:43:42 PM , Rating: 2
Finally a good biodiesel creation idea! just curious about what they would do with all the non-lipid by-products like heavy metals and lord knows what else landfill i suppose.

RE: Cool idea
By kattanna on 9/4/2012 11:55:11 AM , Rating: 2
if the concentrations are right of a useful resource, no reason the "waste" could also not undergo a further process to separate out the useful materials.

Car Repairs
By chagrinnin on 9/1/2012 1:23:09 AM , Rating: 3
Mechanic: "Yeah, see here, got corn in your fuel filter."

Ancient news
By DennisB on 9/1/2012 1:49:31 PM , Rating: 2
Well, using poop as energy source is an ancient practice in asia like india or vietnam. We have been using methan from it for decades. This is just a more modern approach to solid waste.
Dailytech's other article was more interesting, though.

Finally !
By Beenthere on 9/2/2012 12:08:31 AM , Rating: 2
...a proper way to dispose of Bama.

Too late!
By ARoyalF on 9/3/2012 10:16:41 PM , Rating: 2
I'm pretty sure Arco has been doing this crap for years.

By faizyab on 8/31/12, Rating: -1
"Google fired a shot heard 'round the world, and now a second American company has answered the call to defend the rights of the Chinese people." -- Rep. Christopher H. Smith (R-N.J.)

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