ONTARIO, Ore. — Drip irrigation helped onion growers in the Treasure Valley cut water use, reduce fertilizer losses and improve yields.
It also left the region with a stubborn byproduct: about 2 million pounds of used drip tape each year.
“Drip irrigation has been a win for growers and a win for the environment. The hitch is what to do with the tape when you’re done with it.”
Oregon State University researchers and partners are moving closer to a local solution that could keep that agricultural plastic out of piles and turn it into fuel.
In late 2025, a student-based team supervised by Stuart Reitz, director of the OSU Malheur Experiment Station, and Skip Rochefort, an Oregon State chemical engineering professor, completed a full run of a larger “Onionator” pyrolysis unit designed to convert used drip tape into diesel.
The team plans to move the unit to the experiment station in May for continued testing and demonstrations, while also working with partners to understand what it would take for growers to adopt the technology.
“We grow about 25,000 acres of onions a year, and that supplies about 30% of the nation’s onion supply,” Reitz said. “Drip irrigation has been a win for growers and a win for the environment. The hitch is what to do with the tape when you’re done with it.”
Drip irrigation’s hidden byproduct
Drip tape runs just below the soil surface and delivers water directly to the root zone. Reitz said it can reduce water use compared with traditional furrow irrigation while helping limit runoff, erosion and nutrient loss.
But the plastic is typically used for one season to reduce the spread of pathogens. Reitz said each acre of onions can require more than 2 miles of tape, and the material is hard to recycle because it comes out of fields coated with mud from earthen canal systems.
“Landfills won’t accept it,” Reitz said. “And we’re a long way from other major growing regions, so hauling it somewhere else means more fuel burned just to move the problem.”
Turning tape into diesel
Rochefort’s group is using pyrolysis, a process that heats materials to high temperatures without oxygen, to break plastic into smaller molecules that can be condensed into liquid fuel.
“We don’t burn it,” Rochefort said. “It doesn’t combust. We break it apart because there’s no oxygen, and we condense it. Right out of the system we get diesel fuel.”
The Onionator heats plastic to about 460 degrees Celsius. Rochefort said about 1 kilogram of plastic can yield about 600 to 700 milliliters of fuel, and the process can tolerate dirt because of the high temperatures.
In tests, the team found no significant difference in fuel-related carbon distribution between washed tape and unwashed tape, which produced about 60% to 70% yield.
The current Onionator can process about 24 kilograms of plastic at a time — a scale-up from earlier 1-kilogram prototypes. Rochefort said the team completed its first full Onionator run on Nov. 18 and is continuing to fine-tune the system ahead of on-site testing in Malheur County.
Growers want clearer answers
As the technology scales up, the project’s next phase is as much about people as it is about engineering.
Leanne Giordono, director of evaluation and reporting for the Oregon State University Extension Service, oversaw a team of OSU students who conducted interviews with 12 onion growers and industry partners in May 2025 to better understand how growers handle plastic now and what would influence adoption of a new option.
Growers reported a range of disposal strategies, including shipping through intermediaries and storing used tape on-farm. Out-of-pocket costs ranged from $0 to $40 an acre, Giordono said.
Growers were generally supportive of the concept but not yet ready to invest without clearer information.
“They have trust in the experiment station and trust in Extension as a resource,” Giordono said. “They’re willing to pay for a service. But they want to know more about what it will cost, what the benefits will be, and what models could make this viable.”
The interviews also surfaced concerns that go beyond the balance sheet. Some growers said they worry about how piles of plastic affect public perceptions of agriculture, Giordono said, and several raised questions about regulatory context and where a future system should be located.
What comes next for scale
Rochefort said the current unit is a bridge between laboratory work and a future full-scale system. The team’s longer-term goal is a 500-kilogram reactor that could process far more plastic, paired with a workable approach for siting, operations and cost sharing.
“We’re still fine-tuning,” Rochefort said. “But we’ve shown we can do it. The next challenge is building something that fits how growers operate and what the community will support.”
Reitz said that combination — practical research, trusted local relationships and an eye toward adoption — reflects the land-grant mission in action.
“Drip irrigation made onion production more efficient,” he said. “Now we’re trying to close the loop.”
