Dakota Ethanol, LLC located in Wentworth, SD, produces approximately 48 million gallons of ethanol annually. Ethanol production at Dakota Ethanol consumes about 17 million bushels of corn from the region and provides not only an environmentally friendly fuel, but also a valuable high-quality livestock feed for local, regional and national markets. Through plant efficiencies and production & technology enhancements, the plant continues to operate well above nameplate capacity. Fortunately, it looks like Novozymes can help them continue on this path.

Earlier in 2007, Dakota Ethanol approached Novozymes Account Manager, Chris Streckfuss, with an interesting proposition - did Novozymes have a liquefaction product that could help them solve some of their efficiency issues during processing?

Chris Streckfuss was happy to take up the challenge. He comments: "I knew we had the perfect enzyme for the job. So I immediately suggested our premium liquefaction enzyme, Liquozyme SC, for a trial."

Hopes for a higher DE
The main objective Dakota Ethanol had with the trial was to see if Liquozyme SC could generate higher Dextrose Equivalent (DE) values and reduce residual starch at equivalent or lower use-cost compared to the product they were currently using. DE value indicates the degree of starch hydrolysis; a higher value represents greater conversion. And importantly, even a small increase in starch conversion can lead to higher ethanol output and therefore increased profit.

"Liquozyme SC is used in the liquefaction process to break down the starch so the mash can be further processed to fermentable sugars," says Leon Gerry, Operations Manager at Dakota Ethanol. "Due to our particular plant design a DE of 14+ is optimal, but it was impossible to generate such a high DE with the enzyme we were using".

Scott Whitworth, Novozymes Customer Solutions Scientist, was at Dakota Ethanol's plant in South Dakota during the trial. He spent much of his time there monitoring the DE levels and optimizing the dose.

He comments: "I wanted to provide Leon Gerry with enough information to determine whether Liquozyme SC was right for his plant. Liquozyme SC performed very well. It generated extremely high DE at the original dosage and later, when the dosage had been optimized, it still generated the 14+ DE value that Dakota Ethanol was striving for. We were actually able to reduce the dose significantly."

Independent monitoring revealed more
While Scott Whitworth from Novozymes was monitoring the DE levels, Dakota Ethanol was taking its own measurements throughout the trial. They found that besides achieving a sufficiently high DE with a significant cost reduction, they gained several other side-benefits too.

"We were monitoring the viscosity of the mash, particularly when we started decreasing the enzyme dose", says Leon Gerry. "It is very important that even when reducing the dose of the enzyme that the mash is still pumpable. We discovered that even after we reduced the Liquozyme SC dose, we had no problem with viscosity."

Scott Whitworth comments: "Liquozyme SC makes it possible for plants to run at higher solids levels than with competing enzyme products, making significant gains in ethanol production possible through increased plant throughput and a lower overall cost of production."

The level of energy used in the dryer was also reduced during the trial.

"During the trial we observed that our dryer used about 2.7 mmBTU per hour less gas than normal. This adds up to considerable savings on a yearly basis," says Leon Gerry.

Finally, at the end of the process lighter-colored distillers dried grains with solubles (DDGS) were observed. The DDGS co-product is a significant source of revenue for an ethanol plant.

"Lighter-colored DDGS are preferable to our customers as they indicate a higher nutritional value due to less burnt residual starch", says Scott Whitworth.

Ready for some more
Since the trial earlier this year, Dakota Ethanol has completely switched over to Liquozyme SC.

"We are very pleased to say that Liquozyme SC is working just as well now as it did in the trial; we have even been able to lower the dosage a little bit more. And, we are just about to order our second truckload," says Leon Gerry.