The seemingly magical plant, 63 miles northwest of Portland and proposed by a startup called Next Renewable Fuels, is designed to produce “renewable diesel,” a clean-burning alternative to petroleum that can be made from discarded vegetable oil, wood waste and animal carcasses. It’s like biodiesel but refined differently, so it can be pumped into an 18-wheeler with no modifications. Using it cuts carbon emissions by 60%, and it doesn’t produce as much soot.