116 3rd St SE
Cedar Rapids, Iowa 52401
A new facility in northwest Iowa that was built to create environmentally friendly fuel from cow manure polluted a creek this past 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 news 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 past 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 percent methane, 42 percent carbon dioxide and less than 1 percent 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 one and a half million gallons of manure, said Heather Manuel, a spokeswoman for Gevo.
“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 this past week 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.
The story was first published by the Iowa Capital Dispatch.