The Quest for Maximum Yield: Factoring Out pH

By Holly Jessen | August 15, 2011

In another presentation about enzymes, Kulinda Davis, Verenium Corp.’s director, grain processing enzymes, shared results from the use of its new alpha-amylase enzyme at several ethanol plants. Fuelzyme offers plants multiple benefits, including a 1 to 4 percent increase in ethanol yield. “At an ethanol plant size of 50 million gallons or 100 MMgy that translates into a significant amount of revenue that goes directly to the bottom line,” Davis tells EPM.

The enzyme’s “unique mode of action” introduces a substrate into the fermentation process that is particularly suitable for saccharification, the second step in ethanol production. That means using Fuelzyme as the plant’s alpha-amylase enzyme reduces the amount of glucoamylase enzyme needed, she says. It also allows plants the freedom to stop adjusting pH levels at different points in the process. With other enzymes, pH levels are adjusted upward to 5.7 or 5.8 in the mix tank, using ammonia and other chemicals. After liquefaction pH is adjusted down using sulfuric acid. Fuelzyme, however, works in a broad range, from 5 to 5.8 pH, meaning chemicals needed to change pH levels are reduced or eliminated, she says.

Western Plains Energy LLC, a 55 MMgy plant in Oakley, Kan., started using Fuelzyme at 5.15 pH and increased its yield by 1 percent. In addition, the company reduced residual starch in its DDGS by 33 percent. The plant also noticed greatly reduced Maillard reactions in its slurry, which leaves behind a sticky brown goo on vessels. The benefit comes about because ammonia, a nitrogen source required for Maillard reactions, was eliminated, she says.

Hankinson Renewable Energy LLC, a 120 MMgy ethanol plant in Hankinson, N.D., picked Fuelzyme because of its focus on high quality distillers grains with low sulfur content. The company had been using the enzyme about six months as of FEW and had eliminated a truck load per week of sulfuric acid deliveries, saving the company an estimated $1.2 million yearly. In addition, the company’s distillers grains show a 25 percent reduction in residual sulfur.

The final example given was of AE Advanced Fuels Keyes Inc., a 55 MMgy ethanol plant in Keyes, Calif., that selected Fuelzyme due to concerns about harsh chemicals used in ethanol production. Thanks to Verenium, the plant, which is located across the street from a school, received the necessary approvals to restart. “It’s a very environmentally friendly process,” Davis says.

—Holly Jessen