Ethanol production is a delicate and complex process that requires state-of-the-art machinery to maintain efficiency and high standards. The process revolves around the dry milling of various grains such as corn, wheat, barley, and rye. During this complex process, starch (essentially sugar) is fermented to produce ethanol, while also producing a byproduct called distillers grains + solubles (DDGS).
DDGS Industry Insights
To improve their profits, many ethanol manufacturers have diversified their products to include biofuels, plastics, fertilizers, CO2, disinfectants, and animal feed.
DDGS, or dried distillers grains with solubles, are the main byproduct of the brewing industry, with 98% of its production coming from ethanol plants and the remaining 2% coming from the alcoholic beverage industry. The main sources of DDGS are corn, wheat and rice, and its production has increased significantly since 2000, reaching a total of 35 million tons in 2011, while exports have also increased significantly.
DDGS Production Process
During the milling process, grains often contain unwanted debris such as dirt, straw and stalks, so they need to be thoroughly cleaned before storage or further processing. Advanced equipment such as pre-cleaners, de-stoners and magnetic separators can effectively remove impurities. After washing, the grains are finely ground using various methods such as hammer mills or drum mills. The resulting powder is then mixed with water and enzymes and cooked at a specific temperature, usually between 40-60°C. The mixture then undergoes a jet cooking process at 110-120°C and is finished in a liquefaction tank at 90°C. In this final stage, the starch molecules are broken down into smaller chains, which increases the sugar content and reduces viscosity.
Key Steps
To start fermentation, the slurry must first be cooled to 32°C. Once the ideal temperature is reached, fermentation begins. Inside the fermenter, the slurry is mixed with water and active yeast to initiate the process of converting corn sugars into ethanol and carbon dioxide. The fermentation process typically takes about two days, with slight variations depending on the desired alcohol concentration.
The resulting fermentation mixture undergoes separation in a distillation column to extract ethanol that is approximately 95% pure, as the alcohol is separated from water and other impurities. Simultaneously, a decanter centrifuge is used to dehydrate the solid-liquid mixture produced during fermentation. The solid phase then moves to the drying stage for further dehydration.
As the liquid phase evaporates and the wet cake is reintroduced, it forms a dense mixture during the drying process. This mixture is then fed into the tube bundle dryer to a final moisture content of 10%-14%.
The dehydration process plays a key role in minimizing the risk of grain burning, changing its appearance, maintaining its nutritional integrity and slowing its rate of decay. When used for cattle feed, the solids output from the decanter can be used directly without drying. However, for sheep and fish feeds, drying is essential to ensure optimal quality and suitability for consumption.