Improving the fermentation characteristics of corn through agronomic and processing practices
This study determined the influence of corn (Zea mays L.) hybrids, N availability, grain harvest moisture, and drying temperatures on dry-mill ethanol production. Six hybrids, ranging from 92 to 108 d in relative maturity (RM), were planted at two locations over 2 yr. One of four N fertilizer treatments were applied. Grain was hand-harvested at grain moistures of 20 and 25%. Grain was dried to about 15% moisture at either 25, 38, 52, or 60°C in 2003, and 38, 66, 75, or 93°C in 2004. Ethanol was measured after grain was subjected to a small-scale bench fermentation process. Grain yield increased at all four site-years as available N increased to the recommended N application rate. Relative ethanol concentration was generally not affected by normal N fertilizer rates. Significant reductions in relative ethanol concentration occurred at the both the highest and lowest N rates in one-of-four site years. Hybrids designated as high fermentable starch (HS) by the company did not necessarily yield more ethanol than other hybrids. Ethanol concentration was reduced by 0.3% at Brookings for grain that was subjected to a killing frost. Ethanol concentration generally did not differ between grain dried at 38 and 52°C in 2003. Ethanol from grain harvested at 25% moisture and dried at 25°C was 0.1 to 0.3% lower than when grain was dried at 38 or 52°C. Drying temperatures of 25 to 52°C had no influence on relative ethanol concentration when the grain was harvested at 20% moisture. However, ethanol concentration was lowered 0.1 to 0.4% when drying temperature increased to 93°C in 2004. These results suggest that producers should apply the recommended N rates for maximum economic yield, plant adapted hybrids, and dry corn grain between 38 and 52°C to maximize relative ethanol concentration.