Midwest lawmakers are making a legislative push to force the Environmental Protection Agency (EPA) to be transparent and predictable in the process of granting waivers that allow refineries to skirt the requirements of the Renewable Fuel Standard.

There were also press reports last week that President Donald Trump had asked the EPA and the U.S. Department of Agriculture to re­­vise its plan for granting the waivers.

A re­cently in­­troduced measure, sponsored by Iowa Sens. Joni Ernst and Charles Grassley along with senators from other Midwestern states, would...