Study: Iowa State researchers look at using ag waste to plug orphan wells, sequester carbon

In what they are calling a “two-birds-one-stone” approach, researchers at Iowa State University have been exploring whether filling abandoned fossil fuel wells with a “bio-oil” produced from organic material could remove carbon dioxide from the atmosphere.

Mark Mba-Wright, professor of mechanical engineering at ISU, said filling old oil and gas wells with oil produced from plant residue like cornstalks and forest debris can help remove carbon from the atmosphere by returning the leftover plants — which contain carbon — to the deep, underground shafts of the wells.

“On the one hand, you have these underutilized waste products. On the other hand, you have abandoned oil wells that need to be plugged,” Mba-Wright said. “It’s an abundant resource meeting an urgent demand.”

Mba-Wright said he has been researching ways that agricultural waste can be used to aid carbon sequestration for more than a decade. About two years ago, his team at ISU was approached by the San Francisco-based company Charm Industrial — which has been taking a similar approach to carbon sequestration — about combining their research.

We’re “specifically looking at how can we use Iowa's agricultural resources, primarily agricultural waste,” he said.

How it works

Mba-Wright said this method can sequester carbon back into the orphan wells by creating a byproduct that looks like crude oil and could be pumped into underground wells for sequestration.

He said the process is called “pyrolysis.” It involves placing organic material in an oxygen-free environment and exposing it to very high temperatures — topping 1,000 degrees Fahrenheit — for a few seconds.

Pyrolysis creates three byproducts: solid biochar, which is used by farmers as a soil amendment; a gas that Mba-Wright said could be captured and used as fuel to generate the high temperatures; and bio-oil, a carbon-rich fluid.

Pyrolysis does not take carbon out of the atmosphere but instead stabilizes and removes carbon from the organic material being processed.

The research indicates a network of 200 mobile bio-oil production facilities could be feasible. Units would cost about $1.3 million to build, and the bio-oil would need to sell for $175 per ton.

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Mba-Wright said the partnership between ISU and Charm Industrial has been able remove the carbon from the plants and sequester it in the well, solving two problems at once.

According to the study, there are more than 120,000 abandoned wells in the U.S., but other estimates indicate there could be 300,000 to 800,000 undocumented orphaned wells in the country.

Researchers estimate the proposed system could sequester carbon for about $152 per ton, which would be competitive with other carbon dioxide removal practices but with “far less up front investment.”

"Iowa State’s experts showed that bio-oil sequestration using corn stover can deliver a high-value, durable carbon removal product that outcompetes other technologies, while providing new markets for crop residues and delivering new economic value to the rural economy,” Charm Industrial said in a statement. “As the carbon-removal sector grows, Charm is grateful to work with farm and forest communities to grow this opportunity."

Looking forward

Mba-Wright said the long-term vision of his team’s work is to develop a combine-sized pyrolysis unit that farmers could run on the back of their existing combine to collect the organic waste instead of letting it sit on fields.

He said Iowa farmers could immediately turn the stover into bio-oil that would then be transported to wells that need to be plugged.

Mba-Wright said carbon removal doesn’t have to be an “either/or” solution and that there are many opportunities to remove carbon dioxide from the atmosphere.

“There's been a strong, long-term need to reduce carbon levels, and so this technology could, in principle, alleviate or provide revenue for farmers while removing carbon,” Mba-Wright said. “And for oil wells, these are oil wells that need to be plugged because they are emitting CO2 and other gases. So, it's a win-win, both on the farmer side, but also on producer side.”

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Olivia Cohen covers energy and environment for The Gazette and is a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues. She is also a contributing writer for the Ag and Water Desk, an independent journalism collaborative focusing on the Mississippi River Basin.

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Comments: olivia.cohen@thegazette.com