Maize, a primary source of starch, is procured from farmers or suppliers. Quality control measures are taken to ensure the maize meets the required standards for ethanol production. Factors such as moisture content, cleanliness, and absence of contaminants are crucial.

After cooking, enzymes (such as alpha and beta amylase) are added to the mash. These enzymes catalyze the hydrolysis of starch molecules into fermentable sugars like glucose and maltose. The saccharification process is crucial for maximizing ethanol yield during fermentation.

After fermentation, the resulting mixture, known as beer, undergoes distillation to separate ethanol from water and other impurities. Distillation involves heating the beer to its boiling point and then condensing the vapor back into a liquid. Ethanol, having a lower boiling point than water, vaporizes first and is collected, while water and other compounds remain behind. This process produces crude ethanol with a higher alcohol content than the fermented beer.

Crude ethanol obtained from distillation typically contains water and impurities. Dehydration processes, such as molecular sieves or rectification columns, are employed to remove excess water and increase the ethanol concentration. These processes aim to achieve the desired ethanol purity suitable for various applications, including fuel blending.

Ethanol intended for fuel use is often denatured to render it unsuitable for consumption. Denaturants such as gasoline or other chemicals are added to the ethanol to make it unfit for human consumption. Denaturing helps prevent the diversion of ethanol meant for industrial or fuel purposes to the beverage market.

Throughout the ethanol production process, various waste streams are generated, including spent wash or stillage. Wastewater treatment processes are implemented to treat these by-products, removing pollutants and organic matter. Treated wastewater can be recycled for process water or discharged in compliance with environmental regulations. Additionally, the by-products of wastewater treatment, such as sludge or biogas, may have potential uses or be further processed for energy recovery.

Co-generation, also known as combined heat and power (CHP), involves the simultaneous generation of electricity and useful heat from a single energy source. In an ethanol production plant, co-generation units utilize by-products such as lignin or biogas from the production process to generate electricity. The generated electricity can be used to power various plant operations, including ethanol production and wastewater treatment. Excess electricity can be exported to the grid, contributing to renewable energy generation and potentially generating additional revenue for the plant.