Production of bioethanol from sugar beet molasses
In recent years, the use of renewable energy sources, particularly bioethanol as a component of motor fuels, has become increasingly widespread worldwide. The most commonly used raw materials are corn grain and beet molasses. Beet molasses, as a raw material for bioethanol, offers several economic and environmental advantages over corn, wheat, and other products. Firstly, the production cost of biofuel from molasses is 15-20% lower than that of its closest competitor, corn.
Beet molasses is a by-product of beet sugar production, which is used as a raw material for the production of fuel bioethanol, alcohol, food acids, baker’s and fodder yeast, and as an additive to feed for farm animals. It is a thick, viscous, opaque liquid with a dark brown color and a characteristic sweet taste with a bitter aftertaste. The main component of molasses is sucrose. It contains small amounts of invert sugar (0.5-2.0%) and raffinose (0.5-3.0%). Molasses also contains organic compounds such as melanoidins, organic acids, nitrogenous substances, and sucrose breakdown products. Additionally, molasses has a high content of salts including potassium, sodium, magnesium, iron, carbonic, sulfuric, hydrochloric, and nitric acids.
Abroad, it is produced from sugar cane, sugar beet, sweet sorghum, and citrus residues. In Ukraine, molasses is produced only in beet sugar production. The qualitative indicators of molasses are as follows:
Molasses is deficient in some micronutrients and key vitamins and minerals needed for yeast growth and metabolism.
At distilleries that process molasses, the following methods of wort fermentation are used:
• Two-stream fermentation: This method is used to obtain a single product, which is ethyl alcohol (single-product production).
• Single-stream fermentation: This method is used to obtain two products: ethyl alcohol and baker’s yeast (two-product production).
Molasses intended for bioethanol production undergoes acceptance, including express analysis of quality indicators, and is then sent to storage. Prior to processing, molasses may undergo thermal treatment if necessary. It is then acidified, sterilized, and diluted with water, with the concentration depending on whether a single-stream or two-stream scheme is employed. The treated molasses is then used for yeast generation and pumped into fermenters for alcoholic fermentation. During this process, the biosynthesis of ethyl alcohol occurs according to the following equation:
C6H12O6 => 2C2H5OH + 2CO2↑ + E
After fermentation is complete, the matured wort is either sent for separation or directly to the rectification department.
The next steps its distillation, rectification, and dehydration processes . The resulting bioethanol must meet the specifications mentioned in the previous news or reference.