They use a lot of corn.
Corn is indeed a low-fat food, containing about 1 gram per ear until you slather it with all that butter.
But it is by far the biggest crop in the United States, grown in 42 states to the tune of more than 9 billion bushels per year. Nine billion bushels of corn contain some 3 billion gallons of oil, and that’s enough to deep-fry Delaware.
The oil resides in the germ of the grain, where Mother Nature stores it as a concentrated form of energy, 9 calories per gram, to fuel the everyday miracle of creating whole new plants from seeds. In corn, the germ makes up only about 8 percent of the kernel and only about half of that is oil, so an ear of corn isn’t exactly a gusher.
As you can imagine, it takes some doing to get the oil out. At the mill, the kernels are steeped in hot water for a day or two, then coarsely ground to break the germ loose.
The germ is then separated by a floating or spinning process, after which it is dried and crushed to press out the oil.