At least three U.S. coal shipments on their way to China may end up casualties of the escalating trade dispute after Beijing said it would impose steep tariffs that may kick in before the ships reach their destinations.

Mark Gath’s farmhouse in Luverne, Minnesota, sits 30 miles down country roads from Sioux Falls, South Dakota. From that base in the heartland, Gath, a sturdy man in boots and a blue shirt, farms more than 10,000 acres of corn and soybeans with the help of his wife, Leah, and sons Dalton and Stetson. Though his farm is larger than average, he feels squeezed by low commodity prices and the rising costs of seeds, pesticides and equipment. “Everyone is scared out here,” he says.

The Trump administration’s China tariffs spared some finished goods like smartphones and washing machines, while charges on parts and components could drive up costs in the U.S. supply chain.

A chemical compound commonly used to boost crop yields could be the answer to helping the world increase its consumption of renewable energy.