A flood of used cooking oil from China and elsewhere is prompting U.S. senators to question whether some of the shipments meant to supply the biofuel market may be fraudulent. 

Six senators, including Republican Joni Ernst of Iowa and Democrat Sherrod Brown of Ohio, sent the Biden administration a letter asking what steps were being taken to ensure that imports of the oil, known as UCO, do not contain virgin vegetable oil. Imports have surged from less than 200 million pounds a year in 2020 to more than 3 billion pounds in 2023, according to the June 20 letter.

“There is concern by some in the renewable fuels industry that large amounts of imported UCO may be a blend of UCO with virgin vegetable oils such as palm oil, which is directly linked to deforestation in Southeast Asia,” the lawmakers wrote to Environmental Protection Agency Administrator Michael Regan and top Biden administration officials overseeing trade and agriculture. 

If true, it would amount to “fraudulent value distortion” of the commodity meant to take advantage of U.S. tax incentives, as well as fraud under a U.S. biofuel law, according to the senators. It also would severely undermine domestically produced agricultural products that already face “onerous verification and reporting requirements required of farmers to validate carbon-friendly practices,” according to the letter.

The senators asked for a response within 30 days.