What do you think? Leave a respectful comment.

How one utility powers its entire plant from wastewater

Between flushing the toilet, bathing, and washing dishes, the average person in the United States generates almost 100 gallons of wastewater each day. But one utility in the suburbs of Chicago is using the waste it extracts from that sewage to generate the energy that powers its entire plant. NewsHour Weekend's Christopher Booker reports.

Read the Full Transcript

  • Megan Thompson:

    Between flushing the toilet, bathing, and washing dishes, the average person in the United States generates almost 100 gallons of wastewater each day. And dealing with that water requires a lot of resources. In fact, treating water, including sewage, accounts for 3 to 4% of all the energy used in the United States.

    But imagine if that water – even sewage – could itself be used to help generate energy. We're going to take you inside a utility plant in suburban Chicago that's doing just that. It's generating all the power it needs to run … just using the waste that it collects.

    It's a model that could dramatically reduce the amount of energy used to treat wastewater around the country. Christopher Booker has the story.

  • Joe Quinones:

    This is their grease trap from all the kitchen waste.

  • Christopher Booker:

    Outside a sports bar in the Chicago suburbs, Joe Quinones is taking me through his routine.

  • Joe Quinones:

    Everything that comes from the sinks and the floor drains, sometimes dishwashers, they all come in here. And then it separates the grease so it doesn't go into the city sewer.

  • Christopher Booker:

    He works for a company that specializes in collecting fats, oils, and greases, known collectively by the acronym FOG.

    On this brisk morning he starts by breaking up the grease, which hardens at the surface.

  • Joe Quinones:

    It's a dirty job, but it doesn't mean the restaurant is.

  • Christopher Booker:

    He then connects the hose to the truck and starts to suck up the FOG. On this visit, Quinones collects about 1,200 gallons of it.

    From the restaurant, it's about a 15 mile drive to a wastewater treatment facility in the western suburb of Downers Grove.

    Here, Quinones deposits the truck's contents into an underground tank, minus some solid waste that gets caught by the grates.

    Quinones's company pays 5 cents a gallon to dump this material here. But it's not just waste to downers grove. It's a key ingredient in making this plant net zero: meaning it generates all of the energy it needs to run.

    But to understand how this grease supercharges the energy production on site, we need to take a step back to see what this plant does and how it uses power.

    It's a process that starts 40 feet below the ground.

    Our guide is Nick Menninga, the general manager of the Downers Grove sanitary district.

  • Nick Menninga:

    All the sewage is flowing from town by gravity into a big box on the other side of this wall.

  • Christopher Booker:

    Gravity provides all the power necessary to get the sewage here, but to treat it, you need to get it back to the surface.

  • Nick Menninga:

    This is one of the big energy uses in the plant. And there's really no getting around having to pump this water.

  • Christopher Booker:

    Almost 50-year old pumps send an average of 11 million gallons of sewage each day up to the ground level.

    So this is where the water is actually coming up?

  • Nick Menninga:

    Yeah, it comes up here.

  • Christopher Booker:

    From here, the plant continues the process, separating the water from the semisolid waste, known as sludge.

  • Nick Menninga:

    The sewage simply flows in these tanks and anything that settles to the bottom we are able to remove is sludge.

  • Christopher Booker:

    But to fully remove the sludge from this water takes some more energy.

  • Nick Menninga:

    It gets less smelly the farther we go.

  • Christopher Booker:

    This is the aeration tank, where air is injected to help further clean the wastewater.

  • Nick Menninga:

    We're not making a drinking water. We're making a river water. But the water that we make it supports the aquatic community that we have in the local streams.

  • Christopher Booker:

    Over the last decade, the plant has reduced its energy use by about 30 percent. It's done this partly by investing in more efficient equipment.

  • Nick Menninga:

    These brand new technology, high speed turbo blowers are saving us quite a bit of energy compared to the old technology. But they still remain the largest energy user in the facility.

  • Christopher Booker:

    You keep the old blowers as a redundancy?

  • Nick Menninga:

    That's correct. We use this as backup. Obviously we have to have redundancy everywhere because people flush their toilets whether we're ready or not. We have to always be ready.

  • Christopher Booker:

    This plant is one of just a few in the country where all of the energy it uses is generated by the waste collected onsite.

    That starts with the sludge, the solid waste collected throughout the process. It's deposited in an oxygen free, or anaerobic, chamber called a digester. In this environment, microorganisms eat at the sludge and naturally emit biogas. It's a fuel that many wastewater plants capture for heating, usually burning off any excess.

    But here at Downers Grove, the digesters are also fed a special ingredient.

    Remember that FOG, or fat, oil, and grease that was deposited at the plant? It's instrumental in this plant generating enough energy to power itself.

    When it's added to the digester mix, the chemical reaction turbocharges the biogas production.

    How did the decision to take in this grease impact the amount of energy you're able to produce here?

  • Nick Menninga:

    We've actually been able to double our gas production. And as a result double our electricity production as well by taking FOG and co-digesting it with our sludge.

  • Christopher Booker:

    So by taking that grease from these restaurants you're able to double your output?

  • Nick Menninga:

    That's correct. Double the output.

  • Christopher Booker:

    Transforming that biogas into usable power required a significant investment: the utility purchased equipment to clean and purify the biogas. And it bought two generators – about $600,000 in total – which turns the gas into electricity that the plant can use.

  • Nick Menninga:

    The electricity is monitored continuously

  • Christopher Booker:

    At the plant's control center, Menninga showed us how energy usage fluctuates throughout the day. He says the investments to become net zero have dramatically reduced costs.

  • Nick Menninga:

    The energy cost used to be over half a million dollars a year. But now we're down to about $50,000 a year just to maintain that connectivity with the with the utility. And then by taking the high strength waste from the haulers we're actually able to generate about $300,000 a year in revenue. So this swing is pretty dramatic for us. It's over 10 percent of our operating costs.

  • Christopher Booker:

    Menninga says those savings haven't reduced the overall amount that customers pay, but that bills haven't gone up as much as they would have.

    While there have been months when equipment maintenance or heavy usage required more grid power, the plant has met or exceeded its goal of being energy neutral nine of the last 16 months.

  • Nick Menninga:

    So this is the digester control room.

  • Christopher Booker:

    Menninga says this model could significantly reduce the amount of energy used by water utilities around the country.

  • Nick Menninga:

    The water energy nexus is a pretty important piece of the energy puzzle. There's just no reason for for a community to, to use a bunch of energy to treat their waste water when they can be actually converting their wastewater treatment facility into a power generating station.

Listen to this Segment

The Latest