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The Abstract

A Safer Way to Deal With Raw Sewage in the Developing World

Tate Rogers (in rear, with white mask) works with a local pit-emptying team in South Africa to field test the Excrevator. Photo courtesy of Tate Rogers.

In 2011, an engineering student came up with an idea to help people in the developing world deal with raw sewage. His goal was to use technology to help save lives by limiting people’s exposure to the pathogens in human waste. Four years and several countries later, he’s still working on it – and the technology is beginning to come into focus.

Here’s the basic problem: in many parts of the developing world, people don’t use toilets. Instead, they use pit latrines, which quickly fill up with raw sewage and have to be emptied by hand. Emptying those pit latrines means coming into contact with human waste – and whoever has to empty those pits runs the risk of contracting a disease.

Rogers, (in rear, holding the equipment) field-tested the Excrevator with collaborators in Malawi. Photo courtesy of Tate Rogers.
Rogers, (in rear, holding the equipment) field-tested the Excrevator with collaborators in Malawi. Photo courtesy of Tate Rogers.

NC State engineering professor Bob Borden presented an undergraduate class with this problem in 2011, and a student named Tate Rogers had a possible solution. Rogers proposed the development of a hand-held tool that used a gasoline-powered auger (like a giant corkscrew) to pump the waste out of the pits into portable containers. The twisting of the auger would act like an Archimedes’ screw to move the waste.

A lot has happened since Rogers brought his idea to Borden. The two of them brought together a larger team of researchers, including Francis de los Reyes (who has given a TED Talk on sanitation as a human right) and Tarek Aziz, to work on the project. In 2012, they received a $100,000 grant from the Gates Foundation to work on the prototype and test it in South Africa. In 2013 they got a second grant from the Gates Foundation to work on the technology that they now called the “Excrevator.”

That second grant allowed Rogers to do additional field testing in India, South Africa and Malawi. And he learned a lot.

“The Excrevator works well with waste,” Rogers says. “But there is an issue when it comes to dealing with garbage.”

The problem is that human waste isn’t the only thing that ends up in pit latrines. As Rogers puts it, “If you can imagine it being in a pit latrine, we’ve found it.”

Pit latrines can be filled with solid trash (like this one in South Africa), which can clog the Excrevator. Photo courtesy of Tate Rogers.
Pit latrines can be filled with solid trash (like this one in South Africa), which can clog the Excrevator. Photo courtesy of Tate Rogers.

Stones and solid objects don’t pose much of a problem. But plastic bags and clothing can get pulled into the auger, clogging it completely. To address this problem, Rogers and the rest of the Excrevator team have had to develop a variety of solutions.

“One way to deal with the debris is to fish it out, so we’ve developed tools to make that safer and easier,” Rogers says. For example, they developed a strong, retractable claw at the end of a pole that can be used to snag and pull out Excrevator-clogging fabric or plastic.

They’re also developing a powered “macerator” that can grind or chop up any debris, so that it can pass through the auger. Tracey Sisco, a civil engineering master’s student at NC State, has been completing laboratory testing on different mechanisms for handling trash.

“Every pit latrine is different, so we are developing a suite of tools that can be used to deal with whatever obstacles you run into at any given pit,” Rogers says. “And all of the tools – the Excrevator, the macerator, and a related vacuum system – can be run by one power source, called a Powercube.”

Rogers is now a research associate at NC State, and works part-time on waste management research at RTI International, but he’s still working on the Excrevator – and he has high hopes that it can make a meaningful difference in the near future.

The Excrevator team is now applying for a new grant, which would allow them to continue testing and fine-tuning the technology.

“Based on our fieldwork, we have a really good understanding of the challenges surrounding waste handling in the developing world,” Rogers says. “And we’re optimistic that we’ll have reached a point in the next couple of years where we can move from prototype development to begin scaling up manufacturing for widespread use.”

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  1. Great work team. I think this Excrevator when completed will go a long way to solve the problem of latrine owners having to dig new pits when their latrine pits are full. In Ghana, what I see are graveyards of abandoned latrines because when the latrine pits are full, owners are not able to dig new pits hence they go back to Open Defecation. With the Excrevator, these pits can easily to be emptied and owners can continue to use their latrines.
    One thing we have to look at is how the fecal matter can be managed on a broader perspective in such a way that it does not become a health hazard.

  2. Recently in India, Defence Research and Development Organization, A premium Defence Research Institute Works under Ministry of Defence Govt. of India, has developed a Bio Digester Tank which is capable of destroying all pathogenic bacteria and produce water with Methane. Human Faecal matter is digested and all pathogenic bacteria are destroyed. Waste produced is safe for Farming. If the size of Digester is more than 5000 Liters Methane can also be collected to be used in Power generation. Low amount of methane generated can be used for lighting Bio Gas lamps.

  3. Another approach would be raise the outhouse up 5 feet so that a trailer with plastic drum could sit under the floor where the toilet is ( only gravity needed ). Build stair up to the toilet floor. Maybe the plastic drum could have wheels fitted directly to save materials and cost. The trailer could either be pulled like a hand cart or by moped / tractor and taken to be emptied into a waste treatment plant or anaerobic digestor to utilize the methane and compost the waste to be safe for use as agricultural fertilizer. Perhaps two trailers would be needed so there was always one in situ to collect waste from toilet.

  4. Stop….stop right there!…so now tge waste is out in bags….just assuming….and assuming i will…that pit latrines are emptied by hand….where do you dispose the bags?

  5. I cant really imagine making a complex solution to a very simple problem. Just make TOILETS and TEACH the people to USE IT. Problem solve. 100,000 US Dollars could have made a lot of toilets and support volunteers to educate the people.

  6. I would utilize a screen of some sort over the entire Latrine , keep hard solid objects out , shovel off , allow poop to solidify ?

  7. The problem is similar to the problem developed countries have with their human waste. The waste is mixed with non-human waste materials (water, in our case) and much money and resources are spent separating them again. Would think that preventing the mixing in the first place would make the collection and transport task easier to solve. It would adding trash containers close to pits and a strong public awareness campaign to change old habits. Possible driver might be the value of trash to recyclers and repurposing, both of which should be more interested in that waste stream if it were not mixed with human excrement. Sometimes the better solution to a problem necessitates looking backwards up the process flow. Many thanks to the students for being willing to use their talents for the betterment of the human condition.

  8. I’ve high hopes for the Excrevator team. Thanks for really giving your great contribution to make our world a nice place to live… You really, really, really , really deserve a

  9. This kind of technology urgently needed in India for the Sanitation Departments in different towns and cities. A demonstration of the machine to the Government would deliver good benefits to many people. Solid waste would not be an issue to my information. That is another story.

  10. This technology would be very useful for our sanitation project. Finally, an answer to our dilemma on how to collect raw sewage/septage from island barangays where our vacuum truck could not travel to.

  11. Maybe you’re solving the wrong problem.
    Rather than pooping in a pit and pumping it out into containers, have people poop into the containers.

      1. Once a pit is cleaned manually or any other way, get a screen installed inside to catch solid waste. That screen will act as second line of protection even of an awareness campaign fails. That would definitely be cheaper than any other method and will not require further research spending on this issue.

  12. Gracias por preocuparse por evitar los focos de contaminación, todo lo que se pueda hacer para bien es digno de aplausos y gracias a la Fundación Gates por apoyar este tipo de proyectos. Esta Fundación está muy preocupada por la salud humana, por eso mis infinitos agradecimientos a Melinda y Will Gates

  13. The title is so misleading… It is not about raw sewage, it is about fecal sludge! OK, but lay people wouldn’t know what fecal sludge is so therefore “raw sewage” is easier to understand (even if it’s wrong).

    If you want to know more about this R&D work or would like to ask questions to Tate and Francis, then do follow this thread on the SuSanA discussion forum which was started two years ago:

  14. It’s fascinating to see how modern technology can be used in handling and disposing of waste products.

  15. Thank you for that great job. Please come and show us how to do the same. I know mr.Gates is helping us in Liberia, But he can not spoon feel us all the time. He need to develop our mind with the sewage project.Doing Mary Broh time things were good, our city was very,very clean but now with this bad Ebola virus things are very bad.

  16. What about the use of a screen at the bottom of a pit that can be mechanically hoisted out of the pit to remove the solids. Just a thought.

  17. Great job and kudos to both Gates Foundation and to the students who work on this. By only looking at the pit, you would see how desperate they are..

  18. Who is the teacher whom tells to the people the difference between solid trash & waste(They’ve already known that, right)?! The differences of the place that they need to notice or prepare for them…but still has a problem, right?!

  19. I’have Bsc degree in Hydraulic and water resource engineering from Axum university Ethiopia
    I, need you please tell me about your project

  20. a great idea..
    Hats off to you tate rogers..
    Can we use filters at the head of auger, by which we can separate out different types and different sizes of matter present in waste material…
    Or We can also use chemicals like acid to disintegrate plastics in a soft wet mass..?
    I’m a novice, bt leaving my response…
    Thanx brother…

  21. Pretty cool and hope it ends up working out! Have you thought about how you’re going to deliver these to the people who need it most though?
    How to distribute it in the most efficient manner?
    In many communities and cultures, those who do this work are regarded as worthless to society, in India, literally untouchables. Distributing to them may be hard as you have to convince communities they need or deserve to do this.
    That’s in some communities. In others though, what are your distribution channels? Have you thought of microfranchising or other for-profit but bottom up approaches to get these out to where they’re neded to?
    I guess you have to further prove the concept first. But if that succeeds, it would be interesting to see how it gets to the ground! Be sure to contact consulting groups like CGAP to maximise your impact!

  22. What if we change the pit toilet build design to allow for catching garbage? Will it not help?

    1. This presents a new problem of its own, coz now this team will have to move to building toilets, which is no cheap venture. So this might not be a solution in the short-run

  23. Great job folks…wish your research be helpful for mankind. Kudos to Gates foundation, hope they will stand inspiration for many others ! Thanks to their presence I see the best of generosity on the earth – “REAL TIME “