Water Bacteria create renewable energy from wastewater.

Published on September 18th, 2013 | by Tina Casey


Self-Destructing Microbial Robots Turn Wastewater Into Gold Mine

September 18th, 2013 by  

Since we’ve been on something of a wastewater tear this week, let’s keep the ball rolling with a look at another form of new technology for harvesting renewable energy from the stuff. This one is from a company called Pilus Energy. The company has tweaked bacteria to come up with proprietary energy-harvesting organisms it calls BactoBots™, leading to a new generation of high efficiency microbial fuel cells.

A Next-Generation Microbial Fuel Cell

While other wastewater-to-energy systems involving organisms have exploited the digestive or fermentation pathways, Pilus Energy has focused on the metabolic pathway.

Bacteria create renewable energy from wastewater.

Courtesy of Pilus Energy.

So far, Pilus has released two products, RemdiBot and GalvaniBot. We’re especially interested in GalvaniBot, which forms the heart of what the company calls a next-generation microbial fuel cell. Here’s the connection, as explained by Pilus:

Most bacteria can gain energy by transferring electrons from a low-potential substrate, such as glucose, to a high-potential electron acceptor, such as, for example, molecular oxygen, a process commonly referred to as respiration. In humans, the mitochondria represent the metabolic “furnaces” that perform the same function…Essentially, our organism possesses nearly identical energetic properties of the human mitochondrion. In fact, many scientists believe that human mitochondria have evolved from bacteria [more details here].

In addition to generating electricity, GalvaniBot reduces hundreds of organic pollutants in wastewater into high value products, namely renewable hydrogen and methane.

That helps to resolve a problem we noted earlier, which is that the energy density of wastewater is quite low compared to other renewable feedstocks. By extracting more high-value products from wastewater, the BactoBot system has the potential to be cost-effective.

The Go-Anywhere Self Destructing Robot

Pilus has come up with a couple of other interesting tweaks to the microbial fuel cell concept. It has protected its proprietary bacteria with a “key” in the form of a non-toxic additive. Without the additive, the BactoBots quickly die off or self-destruct. In addition to forestalling theft of the genetic code, the key helps to prevent the engineered bacteria from drifting into other environments.

Another aspect of the system is its scalability and portability. In addition to use at large, centralized municipal wastewater facilities, the system could prove cost-effective at residential, commercial, and industrial sites of various sizes, as well as schools and other institutions, and public facilities.

Depending on its mobility, scaled-down versions of the system could also be used at temporary camps (including temporary military bases) and construction work sites.

The system could also serve as an on-board wastewater-to-energy reclamation system on ships, which would open up a boatload of possibilities including cruise ships and military vessels. In that regard, the US Navy is already quite interested in microbial fuel cells.

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

  • mk1313

    And bacteria aren’t known for mutation or gene swapping. Thinking the “additive” will keep this organism from escaping control is shear stupidity!

    • anderlan

      Of course, you mean, bacteria *are* known for gene swapping.

      • mk1313

        sarcasm, as in are you guys doing this really that stupid as to think this will really keep things safe.

        • anderlan

          I know.

    • Ian Cody Harrison

      Hey, once again Pilus Energy representative here! Our strain of bacteria is found almost everywhere as it is, in fact I would be willing to bet it is living on your computer keyboard right now! We have done our best to eliminate the viral capabilities of our strain, but even if they do swap genes we’re not putting selective pressure on them with antibiotics or anything so the chance of some sort of superbug evolving is very slim.

      • mk1313

        Then it isn’t proprietary is it if it is found almost everywhere as is. Which indicates there is either something screwed up in the story or in your statement!

        • Ian Cody Harrison

          Excuse me, I used poor phrasing. The wild type bacteria is found almost everywhere. We genetically enhanced our version, but in very different ways than Monsanto, for instance, changes its corn (we didn’t add any genes to produce toxic chemicals 🙂 )

          Here are links to the patents, feel free to check out the genetic changes we made as well as which aspects are proprietary and which aren’t.



          • mk1313

            Interesting reading. I still think that it is likely the bacteria will find a way around the need for your “additive” in time and “escape into the wild”. It’s “reduced virulence” is a good thing. Not saying the organism is a hazard just that in time it will escape “control”.

          • Ian Cody Harrison

            Absolutely, I think you are likely right.

            However, given that the selective pressure is different than if we were applying antibiotics to kill the bacteria I think the evolution will be slightly different and *hopefully* easier to monitor. If the additive isn’t there the DNA and RNA begin to break down almost immediately. Now if we can make sure that break down is 100% I think it will be very difficult for the Bots to somehow evolve resistance to this method, because their DNA will be mush. That being said, my point was simply that even if they do escape they are a significantly dumbed down version of the wild type that exists all over the place. They can’t move, reduced virulence etc. so they would have to re-evolve (or gene swap with wild types once they got out) to regain these abilities and even then they can pretty much only infect immunocompromised individuals with AIDS or other such diseases.

            All I can say though is, my goal is to clean water thus improving ecosystem function and human health. I will do my absolute best to make sure that these BactoBots and additives are developed to the highest standards, not just as some gimmick to appease the public. We really want to set ourselves apart from companies that have worked with GMOs in the past that have given synthetic biology a bad reputation.

          • mk1313

            To set yourselves apart lets see an honest analysis of best to worst case scenario’s given the bots escape. What are the ecological/health/biosphere results. Don’t assume it won’t happen but that it will happen.

          • Ian Cody Harrison

            That’s a great idea 🙂

            I’m going to do exactly that. Actually, I’m going to contract a 3rd party to do exactly that

          • mk1313

            That means looking at the loss of control, not just escape and they die! Given that premise I look forward to the result.

  • Marion Meads

    Well, good luck to them. Such approach has never worked. These bacteria, with or without the additive will not survive in all situations anyway. Engineers tend to think everything should be simplistic controlled variables. The real microbial world is chaotic and complex. There are several million different kinds of microbes in sewage, it will always get contaminated with other microbes. Pure cultures do not work in real life, it will be super expensive to insist on it. Rather, think like an ecologist, that you are able to produce electricity from a microbial community rather than single strain. Single strains are highly unreliable and unstable and they will immediately collapse after a short while unless you spend inordinate amount of energy to maintain them.

    • agelbert

      I agree. Duckweed is much easier to grow and manage for wastewater cleansing and biofuel feedstock because duckweed uses wastewater as fertilizer.

      Duckweed, the plant that may save mankind by enabling our species to live symbiotically, instead of parasitically, with the biosphere

      How superior is duckweed to corn for ethanol production?

      SNIPPET 1

      **Biosystems Engineering **
      Volume 110, Issue 2, October 2011, Pages 67–72

      Growing high-starch duckweed for its conversion to bioethanol was investigated as a novel technology to supplement maize-based ethanol production. Under the fall (autumn) climate conditions of North Carolina, the biomass accumulation rate of Spirodela polyrrhiza grown in a pilot-scale culture pond using diluted pig effluent was 12.4 g dry weight m−2 day−1.

      Through simple transfer of duckweed plants into well water for 10 days, the duckweed starch content increased by 64.9%, resulting in a high annual starch yield of 9.42 × 103 kg ha−1.

      After enzymatic hydrolysis and yeast fermentation of high-starch duckweed biomass in a 14-l fermentor, 94.7% of the theoretical starch conversion was achieved.

      The ethanol yield of duckweed reached 6.42 × 103 l ha−1, about 50% higher than that of maize-based ethanol production, which makes duckweed a competitive starch source for fuel ethanol production.

      Christodoulos A. Floudas, Xin Xiao and colleagues explain that duckweed, an aquatic plant that floats on or near the surface of still or slow-moving freshwater, is ideal as a raw material for biofuel production. It grows fast, thrives in wastewater that has no other use, does not impact the food supply and can be harvested more easily than algae and other aquatic plants. However, few studies have been done on the use of duckweed as a raw material for biofuel production.

      They describe four scenarios for duckweed refineries that use proven existing technology to produce gasoline, diesel and kerosene. Those technologies include conversion of biomass to a gas; conversion of the gas to methanol, or wood alcohol; and conversion of methanol to gasoline and other fuels. The results show that small-scale duckweed refineries could produce cost-competitive fuel when the price of oil reaches $100 per barrel. Oil would have to cost only about $72 per barrel for larger duckweed refiners to be cost-competitive.

      The article is titled “Thermochemical Conversion of Duckweed Biomass to Gasoline, Diesel, and Jet Fuel: Process Synthesis and Global Optimization.”

      Read more at: http://phys.org/news/2013-03-duckweed-cost-competitive-raw-material-biofuel.html#jCp

      • Ian Cody Harrison

        This is awesome, thanks for sharing and for the detailed info!

        • agelbert

          You are welcome. Part 1 of a two part article (I’m still working on part 2 – I should have part 2 up in a couple of days) here.


          Please scroll down for the duckweed article.
          Pass it on if you like it.

          • V4V

            Nice website. I glanced at it quickly because I am short on time, but looks like it’s worth a revisit for sure- Kudos~!!!

          • agelbert

            Thanks! It looks like it’s going be a kind of scrolling exercise for anybody reading it because I don’t know how to set up an archive or make columns with clickable subject areas but I’ll take it one day at a time. :>)

          • V4V

            My buddy, Kerry (kokanee), set up a website (http://www.byebyedemocracy.org) and he has it do a lot of cool things. He is a pretty cool guy and I am pretty sure he could answer some technical questions if you asked him. I can try to put you in contact with him if you like.

          • agelbert

            Thank you. I put the web site in favorites. I will contact him with questions when I get to that stage of development and will mention that you (V4V) recommended him.

            I just got an e-mail from a renewable energy web site I post a lot on mentioning that my comments are getting flagged as spam (LOL!) because they are “too long” and I should start a blog on their site so I will do that shortly as well.

            Here’s the e-mail body. I bring it to your attention because you might get a good laugh out of it. I suspect the fossil fuelers I was giving a lot of heartburn to(they troll renewable energy sites to bad mouth anything that is clean energy and threatens to destroy their precious dirty oil profits) had a lot more to do with the “spam” complaints than the length of the posts. I was always taking apart their propaganda with in depth sources and studies. They didn’t like that.

            Hello Mr. Gelbert,

            Might I suggest that you take advantage of free blogging available to you as a user on http://www.RenewableEnergyWorld.com? Your comments are frequently flagged as spam by other users, most likely because they are far too long to be in our “comments” section. They’re more like a blog, which I have given you permission to do on our site. Simply log in to http://www.RenewableEnergyWorld.com, and in your account dashboard you will see a link for “Blog Posts.” Click on that link and you will be able to follow the prompts and directions to post a blog.

            This might be a way for you to reach out to the renewables community without having your comments flagged as spam all the time. If you have any questions or you need assistance, please feel free to contact me.

            Best regards,


            I’m off to the renewable energy blogging races!

    • Ian Cody Harrison

      Hey, I actually work for Pilus and one of the things that we were pleasantly surprised to find out in our early tests of the technology was that our BactoBots seem to be outcompeting everything else in the wastewater. I know that getting the bacteria to survive in consortium with native bacteria has been one of the biggest problems in getting this technology past the stage of scientific novelty and we may have solved it!

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