FTIR Offers Push-Button Fermentation Control

By Richard Mills | November 03, 2008
While clouds of misinformed accusations swirl around the emerging ethanol industry, in the eye of the storm, producers are quietly getting on with the essential job of making sustainable fuel. What's more, they're improving the process all the time.

Advances in efficiency are being made across the board. The ability to predict yield and segregate corn at intake is just one example. Further into the process, fermentation is another area under development. While arguably the most critical part of making fuel ethanol, it is also the most vulnerable as infection with unwanted microbial activity can literally eat away at millions of dollars of production.

Although current methods based on high-performance liquid chromatography (HPLC) analysis provide a wealth of information, time-to-result, cost-per-sample and the need for trained laboratory personnel remain barriers to gaining the level of information needed for effective fermentation control. Room exists for something faster, cheaper and easier, especially for those that don't happen to have a premier laboratory on site.

Near infrared (NIR), so well known for applications such as testing grain, has been investigated by many. However, questions remain about its ability to detect infection indicators typically only present at low levels. The field of infrared analysis technology is not finished there. Another related technology has just the right credentials to fill the gap: Fourier transform infrared (FTIR).

FTIR is worth remembering for its proven benefits, including speed, low cost and simplicity. Results for several parameters are delivered in no more than two minutes. Unlimited analyses can be conducted at no extra cost, and anyone can perform the test. FTIR also appears to be particularly well-suited to picking up infection indicator parameters.

A prototype application of the technology has been tested at ethanol plants in the United States and the concept is attracting significant interest as a push-button solution for routine monitoring and control.

Unlimited Testing
For Brian Wrenn, research director at the National Corn-to-Ethanol Research Center in Edwardsville, Ill., the speed of the new monitoring option is especially interesting. He describes that with conventional testing there can be an eight- to 10-hour gap between tests and the actual test takes approximately an hour to deliver results: around 20 minutes for the test, plus the additional time for pulling the sample and setting up. "A lot can happen within an hour and it can be maddening to wait," Wrenn says.

Antibiotics provide a solution, but operators want to avoid using more than absolutely necessary, both with respect to cost and the possibility of residues contaminating distillers grains. Rapid testing can improve monitoring and allow a more proactive approach to fermentation control where the use of antibiotics is minimized.

The ability to test as much as needed at no extra cost is another aspect of the FTIR option, says Mitchell Feldman, laboratory manager at Abengoa Bioenergy of Nebraska LLC, an 88 MMgy in Ravenna, Neb. Since February, the plant has been testing a prototype FTIR unit called the BioFoss developed by Foss. "With HPLC, the filters are at least a dollar per sample and the vials are at least 10 cents, so you are saving $1.10 with every sample you run," Feldman says.

On a typical day, the laboratory at the 88 MMgy plant runs between 50 and 60 samples. However, if issues arise, they will run 100 or more tests depending on what needs to be measured. Although only occasionally required, the need to replace columns for HPLC systems also contributes to costs. "When you run as many samples as we do, it all adds up," Feldman says.

FTIR analysis technology is available in an easy-to-use form and the test model used at Abengoa Bioenergy of Nebraska is a compact, simple-to-use instrument that is no more complicated than a vending machine. "Anyone can use it," Feldman says.

The usability associated with FTIR analysis is also noted by NCERC Director John Caupert. "Training is a huge issue in the industry," Caupert says. "Someone like me can use it and I am not a chemist or an engineer.

Caupert has testified to the U.S. House of Representatives on the need for improved training in what he sees as one of the few growth areas for the present U.S. economy.

Milk, Wine, Fuel Ethanol
FTIR technology may be new to the ethanol industry, but it's common to other industries where the need to monitor fermentation is by no means unique.

Winemakers can get just as many gray hairs as ethanol producers waiting for the outcome of fermentation. But in contrast, many have given themselves an edge in the form of analytical technology that can deliver results for key measurements whenever needed, effectively providing an early warning system for potential problems.

In simple terms, the FTIR method works by shining infrared light through the sample. This picks up the vibrational activity of chemical functional groups. The information is then decoded using a well known mathematical function (the Fourier transform). The technique has been in use for decades to test milk and was first used in 1999 in the wine
industry.

FTIR measures all the regular parameters involved in fermentation control, sugars (maltose and glucose) and ethanol. FTIR technology provides the sensitivity required to pick up parameters often discernable in low concentrations, such as acetic and lactic acids. In this way it offers a more powerful alternative to the better known NIR analysis method.

A common term in connection with FTIR is the "signature" left by a chemical component that can be picked up at specific areas of the infrared light wavelength. Corn mash provides many different signatures and the FTIR technology is ideal for sniffing out acetic and lactic acid among the mass of data. At the same time, studies indicate that it is also better at measuring the more prominent components. "NIR seems to work, but with FTIR it is more specific," Wrenn says.

Feldman shares the interest in the ability to track infection indicators. "In measuring lactic and acetic acids the technology really shines in giving reproducible results," he says. "They are very low level, so they are hard to measure with NIR, but we found that the FTIR instrument actually does a very good job of measuring these low level parameters."

Same Procedure, More Information
Infection control is especially important at facilities such as the Abengoa Bioenergy Nebraska plant where a continuous fermentation process involving eight tanks is used. "A small infection in early fermentation translates into a big problem by the time you get to the end of fermentation," Feldman says.

He explains how, if they see a problem coming, they will take more samples to check that everything is heading in the right direction. At approximately 1 million gallons per tank, a big investment is involved given that 1 million gallons of corn mash is not cheap in today's market. Millions of dollars in grain are in the process.

"We don't lose a whole tank, but you do lose yield," explains Feldman with reference to the fact that an infection either consumes sugar or alcohol. Bacteria in the tank convert sugar and ethanol to something else: either lactic or acetic acid.

FTIR analysis simply makes getting the required control data quicker and more cost effective. "It would be the same with HPLC, but the biggest benefit with FTIR is the time and the cost, which are both excellent," Feldman says.

At press time, the BioFoss unit is still being tested at Abengoa Bioenergy of Nebraska, where it is showing great promise. It has also been tested at the NCERC and at four producing U.S. fuel ethanol plants with positive results.

While the field tests add the finishing touches to the new fermentation monitoring solution, the potential of FTIR is already clear. As an accessible and rapid method, FTIR can help to reduce the use of antibiotics, ensure maximum yield and avoid nasty surprises during fermentation. Above all, it makes testing by anyone in the plant routine. "Why not do tests every hour?" Wrenn says.

Richard Mills is with Foss. Reach him at rim@foss.dk.