How Corn is Processed to Make Ethanol

The process of making corn into ethanol is a multistep process. The first step is milling the corn. It can be done by dry milling or wet milling. Figures 7.10a and 7.10b show the process steps for each wet and dry milling. For wet milling, the corn kernels are broken down into starch, fiber, corn germ, and protein by heating in sulfurous acid solution for 2 days. The starch is separated and can produce ethanol, corn syrup, or food grade starch. As is noted in Figure 7.10a, the wet milling process also produces additional products including feed, corn oil, gluten meal and gluten feed. Dry milling is a simpler process than wet milling, but it also produces fewer products. The main products of dry milling are ethanol, CO₂, and dried distiller grain with solubles (DDGS). Let’s go through each of the steps in the dry grind process. The five steps are: 1) grinding, 2) cooking and liquefaction, 3) saccharification, 4) fermentation, and 5) distillation.