Manure leaks into creek from new ‘green’ facility

By: - February 14, 2022 6:11 am
A manure digester near Rock Valley lies mostly underground and can hold up to 1.5 million gallons of manure. (Photo by Jacob Simonsen/Iowa DNR)

A manure digester near Rock Valley lies mostly underground and can hold up to 1.5 million gallons of manure. (Photo by Jacob Simonsen/Iowa DNR)

A new facility in northwest Iowa that was built to create environmentally friendly fuel from cow manure polluted a creek this week when it leaked an estimated 376,000 gallons of manure water, according to the Iowa Department of Natural Resources.

The manure digester near Rock Valley is among three in Lyon and Sioux counties being built by Gevo, a Colorado company that plans to capture methane from dairy cattle manure and process it into renewable natural gas to fuel low-emissions vehicles in California, according to the company’s website. It began construction last year and plans to have the system operational early this year.

“We’re excited to get NW Iowa RNG online, right on schedule,” said Chris Ryan, the company’s president, in a press release less than two weeks ago. “Our team here has done a terrific job, creating a facility that will become an example of how renewable energy can work for years to come, and we’re excited to bring our partnership with area farmers to the next stage.”

But when the company recently filled the Rock Valley digester with manure, it began to leak into the ground. The leak was discovered early this week when someone noticed contaminated water leaving an underground tile line, said Jacob Simonsen, an environmental specialist for the DNR.

“They don’t know what’s caused the leak,” he said. “It’s kind of puzzling for them.”

The digester is a large, mostly subterranean container that captures biogas produced by microorganisms that feed on the manure. That gas — estimated to be about 58% methane, 42% carbon dioxide and less than 1% hydrogen sulfide — is compressed and sent through a few miles of pipe to another facility that refines it and sends it to an existing, interstate natural gas pipeline, according to documents Gevo filed with the Iowa Utilities Board in 2020.

The Rock Valley digester is the smallest of the three but can hold 1.5 million gallons of manure, said Heather Manuel, a spokesperson for Gevo. She said workers are still attempting to find the source of the leak.

“We will be inspecting all the other digesters as we move forward — just extra precautions,” Manuel said. “This will not delay any timelines at this point.”


Simonsen said it was unclear how long the digester was leaking. The watery manure seeped into the ground and into tiling that is meant to drain stormwater from the area. The contaminated water flowed to a crop field and into Lizard Creek, which feeds the Rock River. It’s unclear how much of the water reached the creek.

The effects of the contamination were not immediately clear, in part because sections of the creek were covered in ice that concealed what lay beneath, Simonsen said. No fish kill was apparent.

Iowa Capital Dispatch is part of States Newsroom, a network of news bureaus supported by grants and a coalition of donors as a 501c(3) public charity. Iowa Capital Dispatch maintains editorial independence. Contact Editor Kathie Obradovich for questions: [email protected]. Follow Iowa Capital Dispatch on Facebook and Twitter.

Our stories may be republished online or in print under Creative Commons license CC BY-NC-ND 4.0. We ask that you edit only for style or to shorten, provide proper attribution and link to our web site. Please see our republishing guidelines for use of photos and graphics.

Jared Strong
Jared Strong

Senior reporter Jared Strong has written about Iowans and the important issues that affect them for more than 15 years, previously for the Carroll Times Herald and the Des Moines Register. His investigative work exposing police misconduct has notched several state and national awards. He is a longtime trustee of the Iowa Freedom of Information Council, which fights for open records and open government. He is a lifelong Iowan and has lived mostly in rural western parts of the state.