Biogas projects at wastewater plants serving Columbus and Cincinnati will offset roughly 50,000 metric tons of greenhouse gas annually, according to city officials.
The Columbus Department of Public Utilities estimates biogas cogeneration projects for its Southerly and Jackson Pike plants will reduce greenhouse gas emissions by about 34,000 and 13,000 metric tons of carbon dioxide equivalents, respectively. That’s the equivalent of taking 10,100 passenger vehicles off the road, said Robert Priestas, administrator for the department’s division of sewers and drains.
The utilities also can get back millions under the Inflation Reduction Act if they meet conditions by the end of this year.
“Climate change is upon us, right? And so we have an opportunity to actually make a difference,” said Stacia Eckenwiler, who serves as assistant administrator for the division. She spoke at the Ohio State Bar Association’s Environmental Law Institute in April.
Columbus’s wastewater utility accounts for a significant chunk of the city’s greenhouse gas emissions, she noted. A 2019 inventory report shows water and wastewater accounted for about 9% of nearly 11 million metric tons of carbon dioxide equivalents from community-wide emissions that year.
The Metropolitan Sewer District of Greater Cincinnati is also planning to use biogas to make electricity and provide heating for its Little Miami Wastewater Treatment Plant. The facility still needs to add equipment to generate and capture the biogas to shift some greenhouse gas emissions away from where wastes are now landfilled, and offset some fossil fuel emissions from energy otherwise used at the plant.
Sewage treatment plants remove solids and harmful pollutants from wastewater. Most often, the cleaned-up water goes into a river, lake or other water body near the treatment plant, generally pursuant to permits issued under the Clean Water Act. Leftover sludge containing biosolids has generally ended up in incinerators or at landfills.
Burning of biosolids releases carbon dioxide to the air, and landfilling biosolids likewise releases greenhouse gas emissions. Both options cost sewer plants money to dispose of the wastes.
Anaerobic digestion is another option. Basically, it composts the biosolids to speed up their chemical breakdown. Solids left at the end can generally be added to soil or used in other ways. The process also produces biogas, which is primarily a mix of flammable methane and carbon dioxide. Burning the methane can power an electric generator and also provide heat energy.
In contrast to methane from natural gas, which is a fossil fuel that contributes to human-caused climate change, the methane from wastewater sludge is generally considered clean energy when it’s used for electricity and heating.
The gas is generated anyway, explained Karine Rougé, CEO of Veolia North America’s Municipal Water services. So, using it works as “a perfect substitute” for fossil fuels, she said. Veolia is not involved in the Cincinnati or Columbus projects.
Beyond that offset, “the methane in natural gas is extracted from subsurface rock formations from a depleting source that cannot be replenished,” said Diana Christy, the director of the Metropolitan Sewer District of Greater Cincinnati. In contrast, biogas is renewable, “in the sense that humans always will produce waste.”
Putting waste to work
Columbus already has a composting program, which began several years ago after stricter regulations meant it could no longer use old incinerators. Now, “all of the biosolids that are produced by our facilities go back to the earth and get used again,” Eckenwiler said. Uses include compost and fertilizer for tree farms.
So far, however, the city has just burned the biogas with a flare. “It’s a wasted resource overall,” she says. That’s set to change.
Biogas projects at the Southerly and Jackson Pike wastewater treatment plants will provide “about half the energy that is necessary at each of our facilities, so it’s a pretty significant amount,” Eckenwiler said. “And that will take that reliance off the grid,” which can help at times of peak demand.
Besides advancing sustainability and the cities’ decarbonization goals, sewer utilities for Columbus and Cincinnati see the projects as a way to reduce costs and respond to shifts in regulatory requirements.
The technology for anaerobic digestion has been around for years, but it has improved recently, Christy said. “Most simply for us, the ‘why now’ is it was an economic decision and the changes in requirements for incineration that we were facing previously.”
Eckenwiler estimated Columbus’s biogas projects will save the city roughly $1 million for the two plants’ energy costs — about half of what they currently spend while biogas is otherwise vented to the air.
She also noted the federal government’s efforts to reduce emissions from the oil and gas industry. “It’s only a matter of time before wastewater utilities are going to be part of that as well,” she said.
Added incentive
The Inflation Reduction Act provides an added economic incentive through its changes to the federal Investment Tax Credit. Previously the credit benefited only people and organizations that paid taxes. The changes now let government units and nonprofits get money back as a reimbursement when projects are finished.
The 2022 law also expanded the Investment Tax Credit to more types of energy projects, including biogas. To qualify, biogas projects must begin construction by the end of this year. The law also provides a “safe harbor” if there’s a commitment to buy at least 5% of the necessary equipment and it is in significant fabrication by or before December 31, Eckenwiler said.
The Jackson Pike project is already under construction and should finish up by sometime next year, Eckenwiler said. The Southerly project is on track to start construction this year and should be complete by 2028.
Cincinnati plans to start construction at the Little Miami plant this year under a design-build contract that lets construction begin while various details are finalized, Christy said. The district is also evaluating the safe harbor provision and considering a purchase of equipment for $11 million before the end of this year, with expected delivery before April of 2024.
The Jackson Pike project for Columbus is estimated to cost about $30 million, Eckenwiler said. “The project at Southerly is part of a much larger project, but the cogeneration portion is about $79 million.” The Investment Tax Credit could provide rebates up to 50%. That includes bonuses for paying prevailing wages and using domestic content, as well as a bonus for projects in or next to an “energy community.”
Parts of Cincinnati’s project that qualify for the Investment Tax Credit could provide up to $50 million in reimbursements, Christy said. Whatever the amount is, “the impact of a direct cash payment from the federal government will serve to reduce the cost burden on local ratepayers as the sewer district reinvests in infrastructure to maintain levels of service and to improve the sewer system in order to better serve the community and to comply with the Clean Water Act.”
Rougé sees a broader trend towards wastewater plants using biogas for energy. In Europe, a prolonged drought and the war in Ukraine have ramped up interest in local energy production, she said. And energy costs have been a major driver in the United States, she said. A desire to boost resilience also weighs in favor of adding biogas or other onsite generation, particularly in states where grid issues already present problems, she added.
Onsite biogas projects may not be cost-effective for some smaller sewer utilities. Yet the Inflation Reduction Act’s deadline is sparking lots of conversations with Veolia’s clients, Rougé said. And even if a wastewater authority doesn’t begin a project yet, other funding support could be available, such as state revolving funds under the Clean Water Act, she said.
Wastewater treatment plants are “complex and technical places,” Eckenwiler said. “They’re also very, very cool resource recovery facilities.”