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How MSD plans to turn sewage into renewable energy

Artist rendering of a planned anaerobic digestion facility next to the existing Little Miami Wastewater Treatment Plant.
Metropolitan Sewer District
Artist rendering of a planned anaerobic digestion facility next to the existing Little Miami Wastewater Treatment Plant.

A planned anaerobic digestion facility in Cincinnati will turn sewage into renewable energy.

The Metropolitan Sewer District plans to build the facility next to the existing Little Miami Wastewater Treatment Plant near Lunken Airport.

Anaerobic digestion is a process where bacteria breaks down organic matter — in this case, the sewage that gets processed at the plant. Normally that solid waste gets transported to the landfill.

"This project is something that will reduce MSD's carbon footprint and improve energy efficiency of our operations," said MSD Director Diana Christy. "We'll also be diverting waste from the landfill for beneficial reuse."

Christy presented the plan to Cincinnati City Council's Climate, Environment and Infrastructure Committee Tuesday morning.

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According to the Environmental Protection Agency, anaerobic digestion is a process where bacteria breaks down organic matter. It happens naturally in wetlands, marshes and landfills; it can be replicated on a small or large scale with many types of liquid or solid waste.

Environmental Protection Agency

Anaerobic digestion produces two products: biogas and biosolids.

Biogas is primarily methane. MSD plans to capture the biogas and use it to help power the treatment facility.

Biosolids can be used in many different ways, including animal bedding, fertilizer, compost and a foundational material for bioplastics.

Christy says they're still evaluating the best way to reuse the biosolids.

"The technology that we are constructing and we'll be utilizing in this project will be creating what is currently categorized as a Class A fertilizer," Christy said.

The facility is expected to cost $150 million and Christy says Hamilton County commissioners have already approved the funds as part of the current capital improvement plan.

"With this project we are able to utilize a very very favorable tax credit that is part of the Inflation Reduction Act because of the renewable energy generation," Christy said. "So we're talking somewhere along the lines of $40 to $50 million we could get reimbursement for through that act."

Construction would have to start by the end of 2024 to be eligible for that tax credit.

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The facility will process solid waste from three wastewater treatment plants that, combined, process about 39 million gallons every day:

  • Little Miami (27 million gallons per day)
  • Polk Run (4 million gallons per day)
  • Sycamore Creek (8 million gallons per day)

MSD started hauling solid waste from these plants to the landfill in 2016. Before that, it was incinerated at Little Miami. New federal emissions regulations meant either a costly equipment upgrade or a different disposal plan.
"We do still incinerate solids on the West Side, and we do that according to the [new] regulatory requirements," Christy said.

The West Side incinerator is at the Mill Creek treatment plant, which treats about 100 million gallons of wastewater a day. Christy says they considered hauling the East Side waste solids to Mill Creek to incinerate there, but decided against it.

"Consolidating all of the waste from our process in one community was really looked at as too much of a burden on a community that already has a lot of impact from not only our operations, but other industrial operations," Christy said.

Council Member Mark Jeffreys asked if the Mill Creek plant could be converted to anaerobic digestion as well, given the environmental benefits.

Christy says the incinerators at Mill Creek will reach the end of their lifespan in about 10 years.

"So we will either need to invest significantly, again, in the current incineration or consider other alternatives," she said. "So I think this will be very informative of what we do next, on the West Side."

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The property next to Little Miami that will house the anaerobic digestion facility is owned by the city. It borders the Ohio River Trail, and Christy says not disrupting that trail is a top priority.

"The new facilities will not obstruct the trail or come too close to the trail. We're working with DOTE [Dept. of Transportation and Engineering] to really maximize the amount of buffer we can leave in place," Christy said. "But we do recognize that some of that area will be impacted by our project. We really want to minimize the change that is observed from the bike trail."

The minimum buffer between the trail and the plant grounds will be 25 feet.

How to learn more

MSD plans to update City Council, Hamilton County commissioners, and the community councils of East End and Columbia-Tusculum as the project moves forward.

You can contact MSD directly with questions:

  • 513-244-1300 (option 4)

A web page will be updated throughout the process:

See the full presentation slides below:

Local Government Reporter with a particular focus on Cincinnati; experienced journalist in public radio and television throughout the Midwest. Enthusiastic about: civic engagement, public libraries, and urban planning.