By on September 1, 2012
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It’s not often publicly remarked upon, but the emphasis on biofuel capacity in the United States has a bit of an international political component to it. American farms exported well over 100,000 metric tons of corn and oilseed in 2010. Some major portion of that production was sent to oil-rich areas which are short on food. The E85 boondoggle can be viewed as a simple declaration to those nations: we can burn your food in our cars, but you can’t eat your oil.

America’s pretty good at producing another item besides food, however, and if early research is any indication, it could be used to run a significant portion of the nation’s car and truck fleet.

According to an article in Chemical & Engineering News, a new process developed by a team led by South Korean scientist Eilhann Kwon makes it easier to extract lipids from… well, you know:

Kwon and his colleagues found a cheaper feedstock for biodiesel production: sewage sludge, the semisolid material left over from wastewater treatment. This sludge is a rich source of lipids, the starting material for biodiesel. Most of sludge’s lipids come from bacteria living in it.

Kwon and his team used n-hexane to extract lipids from sludge pellets from a wastewater treatment plant in Suwon-City, South Korea. Compared to published yields of lipids from soybeans, the sludge produced 2,200 times more lipids per gram of feedstock. Sewage sludge is also a cheaper lipid source than soybeans, Kwon says. Each liter of lipids that the researchers extracted from sludge cost $0.03, while previously published data shows each liter from soybeans costs $0.80.

However, impurities including free fatty acids in the lipids extracted from sewage sludge would interfere with the conventional catalytic process for making biodiesel. So Kwon’s team developed a noncatalytic method that would work in the presence of free fatty acids and other impurities in the feedstock…

To test their idea, the team continuously fed methanol and the extracted sludge lipids into a reactor containing porous activated alumina and heated the reactor to 380 °C. Adding carbon dioxide to the reactor improved the reaction’s yield. The researchers’ method converted about 98% of the sludge lipids to biodiesel.

And there you have it. There’s nothing new about the idea of converting sewage sludge to energy: see this article for an early set of ideas on the topic. Furthermore, sewage sludge already has a cash value: you may be eating some of it right now. This new process maximizes the biofuel return, however, and makes it an attractive choice for future energy.

Will the day come when solar-powered home centrifuges generate biofuel from every toilet in the household? Well, it’s certainly no less likely to happen than, say, a national power infrastructure that would allow everyone in America to charge their Volt or Leaf on 220volt juice without browning-out the whole country every evening.

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19 Comments on “Biodiesel From Sewage Is Cheaper Than Ever...”

  • avatar

    Makes me want to go do my part and help out!

  • avatar

    This technology is exactly the right business strategy. Convert a waste stream into a revenue stream. Even if the cost to produce the fuel is the same as other sources, the costs saved by no longer needed to remove the waste makes it cheaper.

    “Will the day come when solar-powered home centrifuges generate biofuel from every toilet in the household? Well, it’s certainly no less likely to happen than, say, a national power infrastructure that would allow everyone in America to charge their Volt or Leaf on 220volt juice without browning-out the whole country every evening.”

    Yes, it is less likely. There is such a power disparity between the afternoon (peak loads) and the middle of the night that we have ample electric capacity so long as cars are charged in the middle of the night instead of the evening. Also, if we do move to wide-spread solar-powered homes, it removes load from the grid making charging EVs less of a burden.

    Individual waste treatment plants in each house ignores efficiencies of scale and unnecessarily duplicates costs. A single fuel production plant located at the waste treatment facility leverages existing infrastructure an minimizes new costs. It’s also much easier to maintain a single processor than thousands.

  • avatar

    I can see Washington DC becoming self sufficient with power.

  • avatar
    el scotto

    A really renewable resource.

  • avatar

    The. It about heating the reactor to 380 degrees and needing to ad C02 is a bit of a downer to an otherwise terrific idea. Both require energy inputs which may make scaling the process difficult. Reducing the among of energy to produce energy is what will win us away from traditional petroleum.

    Oh, and the bit about corn and E85… It’s an election year. A certain Canadian once said that an election was no time for the truth. What she meant was actually very subtle and a critique about election year rhetoric. As history shows, her party was obliterated in the polls that year. At least politically, really viable alternative energy sources like hydrocarbons from sludge will be off the agenda for a while.

    • 0 avatar

      To be clear…Biodiesel and E85(ethanol usually made from corn here) have absolutely nothing in common and are two completely different fuels burned by different engines.

      Ethanol, a poor quality substitute for gasoline, is a Rube Goldberg waste of time, money and diesel, supported only by midwestern corn producers, processors, misguided legislators and auto cos.

      Biodiesel, on the other hand, is a higher quality/cetane product than dinodiesel and can be used by ANY diesel, the engines that move the planet and can also be further refined into jet fuel.

    • 0 avatar
      dash riprock

      A certain Canadian once said that an election was no time for the truth. What she meant was actually very subtle and a critique about election year rhetoric. As history shows, her party was obliterated in the polls

      I believe that was Kim Campbell? My preferred statement came from Sheila Copps who in response to questions asking her if she was going to resign(in the campaign she promised to resign if her party did not repeal the GST 7% tax – which they did not). I paraphrase but she esentially said “you should not beleive anything said in a campaign so no I will not resign”. Truest words ever out of a politician.

      On the topic….corn ethanol is a boondoggle advantaging the few and costing the many including the poor whose food costs go up and consume more and more of their disposible income. C’mon Americans get your politicians to cut this crap

      • 0 avatar

        >I believe that was Kim Campbell?
        Bingo. Out of all of the hopefuls that haven’t made it in the past twenty years, she probably would a made a decent PM were it not for the baggage that she inherited.

        > C’mon Americans get your politicians to cut this crap

        In all fairness, ethanol is showing up in our (CDN) gasoline for no good reason as well. Somebody gets subsidies from corn. Nobody gets subsidies from sludge, because it’s basically the government’s (municipalities, really)

  • avatar

    If current biofuel smells like french fries, what does this stuff smell like?

  • avatar

    Great article Jack. I already can’t look at an E85 pump without thinking that I’m shitting where I eat if I use the stuff.

  • avatar

    Ricer boy fart can mufflers will be more logical with the exhaust from this fuel…..

  • avatar

    So now there’s a choice of what your vehicle’s exhaust will smell like. French Fries, or……….

  • avatar

    Lipids from sewage?

    It’s about time…and I know this is a cheap shot, but…fat s…!

    Come on, who here hasn’t thought the exact same thing, or don’t we know what lipids are?


  • avatar
    Andy D

    Nothing new under the sun. Look into thermal de-polymerization. They work , but get very smelly when turkey waste was used for “lipids” The process uses the heavier sludge to cook off the volatiles for a net gain. ZZ, you’re a Gloomy Gus.

  • avatar

    I don’t understand why all the methane and sulfides from sewer mains is not burned on the spot to generate some electricity, instead of complicated carbon filters that require maintenance and/or forced air systems that require maintenance and electricity. Just like recycling paper, aluminum, and plastics (post-consumer), the economics of using existing resources are quickly catching up to our disposal-centric methods. We should not be so arrogant, selfish or blind as to realize that we need to use what we have more efficiently so that it lasts longer. Our consumption-based society has become drunk on entitlement (left-leaners, government handouts; right-leaners, deferring problems for the next person/group).

    There is a huge project taking place close to me to remove the frequent sewer-stink with complicated systems and structures. Although quite necessary (located close to many houses and in a national park used by many people), none of the studies performed (over a 10 year period) looked at the operating costs of these systems nor addressed any sort of sustainability component (although they did address endangered species – like hydrogen sulfide is killing special rats trying to get into the sewer or something). We oughta be ashamed of ourselves for not looking at the lifetime cost – only addressing a 1 or at a maximum, 5 year budget, when we will have to deal with the consequences for decades.

  • avatar

    i love the classic “burning food” comment. do the tiniest amount of research and you’ll see that corn is used to produce EVERYTHING. and, for some reason, it’s politically/morally/whatever correct to use corn for all of these things – but it’s not OK to use it as a fuel. check out the percentages, ethanol isn’t the highest single non-food use of corn.

    “we can burn your food in our cars”
    BTW, we aren’t burning *their* food in our cars – we’re burning *our own* food that we sell to them for a profit.

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