Seasonal variability in ethanol concentrations from a dry grind fermentation operation associated with incoming corn variability

• This is the very first study to quantify variation in dry grind ethanol production due to incoming corn variability at an ethanol plant over a year.
• Ethanol concentrations for commodity and control corn were low in the beginning after approximate harvest (October–December, 2012), peaked during the month of January and thereafter decreased again. Rates of change in ethanol concentrations for commodity and control corn were statistically similar.
• Enzyme treatments with advanced amylases and protease resulted in the highest mean ethanol concentration over a year which can improve plant profitability.

Corn from an ethanol plant (commodity corn) and an identity preserved corn hybrid from a seed company (control corn stored at 4 °C) were used to study the effects of incoming corn on dry grind ethanol concentrations. Ethanol concentrations were determined every 2 weeks for 1 year using conventional dry grind procedure. Variations in ethanol concentrations were significant and variability patterns for commodity and control corn followed the same trend. Highest ethanol concentrations were seen in the month of January. Variation with control corn suggested that storage time is a significant factor affecting ethanol concentrations. Effects of different enzyme treatments on mean ethanol concentration over a year were evaluated. Two liquefaction enzymes (optimum pH – 5.8 and 5.1, respectively), two saccharification enzymes (optimum pH – 5.0) and one protease were used in five enzyme treatments (I–V). Final ethanol concentration with enzyme treatment V was (17.5 ± 0.486)%v/v. This was 0.6% higher than enzyme treatment I resulting in an additional ethanol production of 600,000 gallons/year in a 100 million gallon/year ethanol plant. Using more effective enzymes increases overall dry grind ethanol production and ethanol plant profitability.