A Shocking Ethanol Enhancer

Squeezing more ethanol from a bushel of corn is one way for an ethanol producer to stay on top of his game. California-based OptiSwitch Technology has developed a process that could increase ethanol production by 5 percent or more, using high-power silicon switches to apply voltage to the cell walls of the corn kernel.
By Anna Austin | February 04, 2009
How does a company that makes high-performance semiconductor switches make an ethanol plant more efficient? OptiSwitch Technology Corp. developed a reliable, solid-state switch (a component that can break an electrical circuit) for critical military applications with the help of some internal funding and a $10 million contract from the U.S. Department of Defense. OptiSwitch's specialty is producing high-power, short-duration electrical systems, or "pulsed power," which use high voltages—10,000 to more than 100,000 volts—and high currents—10,000 to more than 100,000 amperes—for durations of hundreds of microseconds or less.

On the surface, the company's connection to biofuels isn't obvious, but its budding technology has the potential to fit comfortably into the industry.

Interest in Ethanol
OptiSwitch became interested in ethanol about two years ago, according to David Giorgi, chief technology officer and president of OptiSwitch. The technology the company has developed is based on electroporation, or electropermeabilization, a process that is more familiar to those in the medical industry or cancer patients who have received chemotherapy treatments than to ethanol producers.

During electroporation, high electrical pulses are briefly applied to the cell plasma membrane, or cell wall, which permeate or poke holes in the cell. In the medical field, this is done to introduce effective amounts of medicine into a cell or specific area. The holes serve a different purpose in ethanol production. Rather than introducing a substance into the cell, the holes poked into corn kernels allow starch to effectively come out of the cell and to gain more accessibility to enzymes.

Pictured is an artist's rendering of an electroporation system for a 25 MMgy ethanol plant. A 100 MMgy plant would require four of these systems.

The company's ethanol research process involved a visit to an institute in Karlsruhe, Germany, which was using electroporation to increase the sugar yields in sugar beets, Giorgi says. "The problem they had is that they were using a switch called a spark gap, which consists of two electrodes that you over-volt and develop a spark between to close the switch," he explains. "The process of forming the spark causes erosion of the electrodes, which limits the life and reliability of the system. They weren't able to get the system to operate for the duration of the sugar beet harvest—or three months."

After seeing that process, OptiSwitch decided to use a semiconductor instead of a spark gap, Giorgi says. "These are everywhere—in your cell phone or camcorder—and they are very reliable," he says. "The problem with these types of switches is that they are low power, and we needed high power." To remedy the situation, the company took silicon semiconductor switches and engineered them for high-power, high-current applications.

During the company's experiments, which were conducted and evaluated at the National Corn-to-Ethanol Research Center on the Southern Illinois University campus in Edwardsville, OptiSwitch ran corn mash, which would normally be processed at an ethanol plant, through its system and found that a significantly high amount of fermentable sugars were released, when measured and compared with control samples.

"On another project in which some of our team members were involved, a commercial-scale pulsed electric field unit—very similar to the electroporation unit—was built and used in the food industry to replace heat pasteurization," says Tajchai Navapanich, director of operations at OptiSwitch. "Pulsed electric fields are effective in killing bacteria. We are currently involved with one of the largest ethanol producers in the nation to determine the effectiveness and scalability of a system which could increase ethanol yield and at the same time eliminate the use of antibiotics."

Despite all the research that's been conducted on this technology, no one was able to scale the electroporation to work in something as large as an ethanol plant without constant repairs and maintenance to the machinery, Navapanich says. "[But] that's exactly what we've done," he says. "Existing solid-state switches, although highly reliable, are not capable of extremely high-power applications."

Installation Logistics
The high-power silicon switches can handle 100,000 amperes and volts to perform the electroporation process on a large scale, Navapanich says. Installing the technology in an ethanol plant would not be difficult, he adds.

As in every case where the technology seems too good to be true, the question of economic viability must be asked. Would it put out more energy than it uses? "We have calculated that it will only cost a few pennies more per gallon to generate 5 [percent] to 10 percent more ethanol," Navapanich says. "At this point, we haven't built a full-scale system but, based on the parameters from lab trials, the modular unit would be able to process roughly 25 MMgy. If you had a 100 MMgy plant, you would need four units."

This artist's rendering shows the electroporation cell retrofitted in line with the existing 8-inch pipe in an ethanol plant.

The units would have the footprint of a compact car and could easily be retrofitted into any existing ethanol plant. "With that kind of footprint and some pipe rerouting, it could be done in a week," Navapanich says. Taking into account maintenance, equipment, cost and electricity, the estimated pay-back period would be 12 to 18 months—and would increase ethanol output by 3 percent to 5 percent a year, he says.

OptiSwitch is currently finalizing a research scale-up agreement with one of the largest ethanol producers in the U.S., a project which could be completed before the summer of 2009.

Cellulosic Ethanol and Biodiesel
OptiSwitch is also looking into the use of electroporation as a pretreatment method for cellulosic ethanol feedstocks. "The advantage is that the process doesn't involve the use of steam explosion or acid hydrolysis, which produces inhibitor compounds that render a portion of the cellulose-derived sugars unusable for fermentation into ethanol," he says.

This is an important development as ethanol producers are leaning towards using cellulosic feedstocks in the future to lower their carbon footprints.

"We are looking at applying our technology as a pretreatment process to eliminate steam expulsions or acid hydrolysis. That's something we're looking into doing, hopefully later this year."

Another area that looks promising using the same principle is algae-based biodiesel production, Navapanich tells EPM. "Two hurdles that must be cleared are algae dewatering and lipids extraction," he says. "The current solvent extraction method uses hexane to extract lipids. This process, however, is expensive, costing upwards of $1 or more per gallon of algal oil."

OptiSwitch recently presented the results of its experiments at the Algae Biomass Summit in Seattle, Wash. "This work was a collaborative research effort between OptiSwitch and an Arizona State University team," Navapanich says. "It showed that electroporated samples required one-third the amount of solvents for lipid extraction and was achieved in one-third the time."

Navapanich says OptiSwitch is beginning collaborative research with Washington State University on the dewatering of algae using direct-current and sacrificial metal electrodes in a process called electroflocculation (EF), or electrocoagulation (EC). "Test results performed at WSU have shown that greater than 99.9 percent of the algae was removed from test samples in about 20 minutes, and research indicates that removing algae from solution using EF/EC could cost as little as fractions of a penny per gallon of treated water, again significantly bringing down the cost of using algae as a biofuels feedstock," he says.

Soon, OptiSwitch will venture into a joint collaborative research effort with a large algae company to optimize and scale-up the technology. "We anticipate that we can bring down the cost of dewatering and lipid extraction to around 30 cents per gallon of algal oil within two years or less," Navapanich says.

OptiSwitch's technology is yet another example of an older, commonly used process revamped, further developed and uniquely applied to a completely different process.

Seemingly well on its way to a smooth transition from military applications into the ethanol and biodiesel industries, OptiSwitch may have the potential to make significant impact on the advancement of renewable fuel technologies.

Anna Austin is an Ethanol Producer Magazine staff writer. Reach her at [email protected] or (701) 738-4968.