Dakota Ethanol optimizes liquefaction

April 02 2008 / Fuel ethanol

Dakota Ethanol optimizes liquefaction with Liquozyme® SC

Seeking to reach a higher level of starch hydrolysis, Dakota Ethanol looked to Novozymes to help optimize their liquefaction. They found the solution
they were looking for with Novozymes’ Liquozyme SC.

Dakota Ethanol, LLC located in Wentworth, South Dakota, 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 as well as production & technology enhancements, the plant continues to operate well above nameplate capacity. Partnering with Novozymes has helped them continue on this path.

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.”

Liquozyme SC is an alpha-amylase that is optimized to reduce dextrin chain length and mash viscosity prior to saccharification and fermentation with yeast. It is used during the liquefaction stage of ethanol production, where it is added to the thick liquid mash. It breaks down complex starches into smaller dextrin chains and in the process thins the liquid so it is ready for further processing.

Fulfilling 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 dosage.

He comments: “I wanted to provide Leon Gerry with enough information to determine whether Liquozyme SC was right for his plant. Quickly, it became clear that Liquozyme SC performed well. It generated extremely high DE at the original
dosage.”

	Scott Whitworth (right), Novozymes Customer Solutions Scientist, worked together with Leon Gerry, Operations Manager at Dakota Ethanol, to increase the plant’s DE levels and optimize the enzyme dosage during the trial.

Independent monitoring reveals further benefits
While Scott Whitworth from Novozymes was monitoring the DE levels, Dakota Ethanol was taking their own measurements throughout the trial. They found that besides achieving a sufficiently high DE, they gained several other side benefits too.

“We were monitoring the viscosity of the mash,” says Leon Gerry. “It’s very important that the mash is pumpable. We discovered that with Liquozyme SC, 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.”

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

“After we switched to Liquozyme SC, 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 entire process, lighter-colored distillers dried grains with solubles (DDGS) were observed. When ethanol plants make ethanol, they convert only the starchy part of the grain. The remaining nutrients - protein, fiber, and oil – are by-products and can be used to create livestock feed – DDGS. This DDGS coproduct is a significant source of revenue for an ethanol plant.

“Lighter-colored DDGS are preferred by 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, Dakota Ethanol has completely switched over to Liquozyme SC.
“We’re very pleased to say that Liquozyme SC is working just as well now as it did in the trial, and we’re just about to order another truckload,” says Leon Gerry.