Optimizing for More Oil

With corn oil extraction widely implemented, the ethanol industry turns to improving yields and efficiency.
By Susanne Retka Schill | April 11, 2014

Spinning corn oil from syrup has become the norm in the ethanol industry. Not long after the first mechanical extraction technologies were introduced just five to seven years ago, ethanol producers were asking chemical suppliers if there was something that would boost extraction rates—if nothing else, to get the yields up to meet the necessary return on investment. The results were impressive, with some producers tripling their corn oil yields from pure mechanical means with the use of chemical additives. As a result, robust competition among the providers of additives has emerged in the ethanol industry and in the short time since the first additives were introduced, much has been learned.

“When you think about where ethanol plants are today and where they were 20 years ago, they continue to find new technologies to achieve better ethanol yield,” says Jason Van’t Hul, senior industry technical consultant with Nalco. He points to the advancements made in enzymes that boosted ethanol yields as one example. “We’re kind of in the 1980s days of corn oil extraction,” he says. Nalco provides chemistry and services to help producers optimize their systems.

There is a high percentage of plants pairing mechanical oil separation technologies with chemical extraction aids, says McCord Pankonen, applications and product development manager at Ashland Inc. The company has developed oil extraction aids for the ethanol industry since 2008, he says. “A producer came to us and said, ‘We aren’t getting the oil we’re supposed to, do you have a chemistry that can help?’”  The company now has five products available to meet varying situations, plus kosher options for feed bound for kosher-certified animals.

“Plants were getting 0.3, 0.4 or even 0.5 pounds of oil per bushel of corn processed with pure mechanical means,” says Todd Emslander, director of sales in the ethanol process technology group at U.S. Water Services. “They were doing pretty well, but looking to increase those yields.” He points out that a 100 MMgy ethanol plant processing 125,000 bushels per day would realize more than $1 million per year if it could increase corn oil yields by just 0.1 pound per bushel of corn. “That gave rise to a lot of companies getting into the market to provide surfactant-based chemistries to enhance those yields.”

Site-Specific Complexity
The different service providers have learned, through experience, that it isn’t as simple as just throwing a surfactant into the syrup stream. The best place to add the chemistry differs widely, and is virtually plant specific, plus getting consistent results has been a challenge for all.

“Each plant can differ in many ways, depending on design, engineering and operations,” Pankonen explains. “There’s different operational philosophies. For instance, it is important to profile evaporator operations to determine where to best draw from to extract oil, which has an astounding effect on the efficacy of a corn oil chemistry.”

“There are dozens of variables that impact oil recovery,” agrees Emslander. “There are a few factors that affect recovery more than others. But when you have each plant running different recipes and in different geographical areas—plants running different separation technologies and different plants having different designs, it gets convoluted really fast. You have to identify those factors for each plant.” In addition, what works in one plant doesn’t necessarily work in another, he says. “We’ve seen plants where high process pH has worked significantly better than low pH and vice versa. It’s really dynamic. There are some generalities, but every plant is different.”

Every crop is different as well. Experience is showing that recoverable oil differs from year to year, and even within a crop year. “We didn’t see it in 2012, but in 2011 and 2013, we saw early in the season that it was a little bit of a struggle to capture the corn oil. But as the crop was allowed to age, things got better,” Van’t Hul says.

The differences in corn from year to year are outside an ethanol producer’s control. For those factors that can be controlled, however, the service providers are finding the interrelationships among parameters are complex and all report the learning curve has been steep. Grind size can have an impact as well as the enzyme package used on the front end. The solids loading in the front end has a big impact, as do pH and temperature. Finding the best location to introduce the chemistry for adequate mixing and consistent results is important, and differs from plant to plant. The length of piping between pumps and tanks can have an effect, for example. All of those nuances impacting the efficacy of the chemistry are in addition to probably the biggest one—the design of the centrifuge technology itself. 

As a result, dosages of additives can vary widely, says Van’t Hul, explaining that which evaporator the syrup stream is taken from to run through the oil extraction process has a big impact. “A service company can help you understand that. Sometimes it’s counterintuitive,” he says. “One thing I’ve learned is you don’t go in with preconceived notions. We tell our customers, we’re going to try it in different locations.”

The return on additive investment can vary widely as well, he says. “If they had a very inefficient system before we started, we can really impact operations and get $10 more oil for $1 additive. In really efficient systems where you just need a little extra help to get that extra oil, you may have to spend $1 to get $2 back. But at the end of the day, there is a return.”

Besides improving extraction rate, chemical aids have other benefits. “Less mechanical energy is needed to separate the oil,” Pankonen says, plus the oil is much cleaner. “The solids level depends upon the marketer and the final use,” he says, explaining typical specifications can range from 5 to 15 percent allowable solids. Most corn oil is destined for either the animal feed or biodiesel markets.
Another big factor that impacts oil extraction aids is the overall plant design. Greg Smith, sales director of industrial chemicals for Croda Inc., explains that Croda’s demulsifier/emulsifier works best in plants that have a stillage syrups storage tank before centrifugation, although it also performs well in continuous feed systems. As a commodity chemical company, Croda has a slightly different role in the oil recovery enhancement field, he adds, being less involved in providing services. “Ethanol plants are welcome to purchase our product and manage their own hook ups and feed rates. We also supply surfactant to service providers who use it in their chemistry blends.”

Smith explains Croda’s research indicates time, temperature and pH are the primary parameters to consider in fine-tuning oil extraction. The chemistry works best at 180 to 200 degrees Fahrenheit, and temperature can be a tool to adjust extraction rates. “You find the right feed rate, then as much residence time as you want, then you get it hotter. The last thing you do is drop the pH below 4,” he adds. “Some [syrup] is coming off at 4.8 or 5, so if you can trickle in sulfuric acid and it’s cost effective, people do it.”

The amount of oil ultimately extracted depends on getting the multiple factors in a particular plant right. As the industry learns more about how to get consistent results and tweaks the chemistry blends to meet varying situations, ethanol producers are increasing extraction rates, achieving around 1 pound per bushel of corn in some systems. Producers are also getting better at fine-tuning extraction to leave just the amount of oil needed for the end distillers grains market, and no more. 

Enzymatic Approach
This past year, several ethanol plants have been examining a newly introduced enzymatic approach developed by Novozymes to enhance corn oil yields even further. The company introduced a new enzyme trademarked Olexa at the International Fuel Ethanol Workshop last year, says Jack Rogers, biofuel global marketing manager for Novozymes. “We’re seeing great results—an average of 15 percent increased corn oil and 2 percent increased ethanol yield. There’s an energy reduction of around 3 percent, depending on the plant, and we’re seeing a significant urea reduction.”

The enzyme works by breaking down the protein outer layer of oleosomes, which bind oil within the corn kernel. “We’re releasing a pool of oil that chemicals aren’t able to access,” Rogers says.  “It is a novel way to improve oil extraction.” The enzyme is added directly into fermentation and no process or equipment changes are needed. In addition, a boost in ethanol production comes from another action of the enzyme in releasing amino nitrogen from the corn that is favored by yeast over other nitrogen sources such as urea. That has resulted in urea reductions as much as 70 percent, Rogers says.

There’s a lot of competition among the suppliers of corn oil extractions aids, admit those contacted for this story. That, in turn, has increased the number of trials conducted at plants as products are compared and new ideas for improvements examined. Getting a proper baseline for comparisons is important, as is collecting the right metrics and controlling all the variables but the one being tested. As a result, the ethanol industry as a whole is improving its sophistication in trialing new technologies.

“You’re seeing a lot of innovation, mechanically, chemically and enzymatically, and you’re going to continue to see that. It’s good for the industry, and I don’t see it slowing down any time soon,” Pankonen says.  “What we’ll continue to see is a lot of plants generating new ideas and asking vendors to look at ways they can implement them.”

Author: Susanne Retka Schill
Senior Editor, Ethanol Producer Magazine