This post is based on my article from the January 2008 issue of Ethanol Producer Magazine. The information in this article may no longer reflect the current state of the research projects described or current thinking about any scientific issues discussed.
Ethanol isn’t made from corn. It’s made from starch. While a good-sized chunk of a corn kernel is made up of starch, there’s a lot of other stuff in there as well. Stuff that can be even more valuable than the ethanol made from the starch. In a conventional dry-mill ethanol plant all of the potentially valuable fiber, oil and proteins in corn get tossed into the fermentation tank with the starch. It comes out of the process as distillers grains. Fiber and oil can be extracted from the distillers grains, but almost all of it is used for animal feed. Wet mills separate the fractions of the kernel so a pure starch stream can be used for food or as a feedstock for ethanol production. The coproducts are separated in the process and can be marketed as well. But wet mills are expensive to build and operate and require chemicals such as sulfur dioxide which are regulated as pollutants.
Purdue University researcher Li Fu Chen and his graduate student Qin Xu have developed a process which, if successfully implemented on a commercial scale, would combine the advantages of both milling systems. It has the potential to lower the cost of fractionation without the use of harsh chemicals and produce slightly more ethanol per bushel of corn. The Purdue Research Foundation licensed the patent for what has become the Chen-Xu process to Bio Processing Technology Inc., which has in turn reached an agreement with Reed-Three Rivers Bio-Grain Inc. of San Jose, Ill., to implement the system in the latter’s proposed ethanol plants. Reed-Three Rivers Bio-Grain is proposing to build nine 240 MMgy ethanol plants in Illinois, Indiana, Kentucky and Arizona. Construction on the plants will begin in early 2008, says Dale Elder, vice president and chief financial officer of Reed-Three Rivers Bio-Grain.
The Big Squeeze
The Chen-Xu process differs from wet milling in the number of steps it requires to fractionate the corn kernel. According to Chen, wet milling can take up to 13 steps to remove valuable products from the corn, starting with a two-day soak in a dilute sulfur dioxide solution to soften the kernels and release nutrients. The Chen-Xu process, on the other hand, takes just two to five steps, depending on which components of the grain are extracted, and requires no preprocessing. “The process I developed doesn’t require soaking,” Chen says. “In wet milling, to remove the oil they separate the germ first. What I did was remove the oil, [the protein] zein, gluten and fiber to obtain some syrup. Then this syrup can go to fermentation. Compared with wet milling we get the same kinds of products and byproducts. Because we don’t go through the soaking, these products can be food or pharmaceutical grade.”
According to the patent for the process, corn is fed into a high-shear processor with water or steam. If the starch is to be used for ethanol production or corn syrup, thermostable amylase enzymes can be added during this step to start breaking down the starch into simple sugar. The heat and pressure inside the high-shear processor partially gelatinizes the starch, making it more soluble in water and promoting liquefaction. The oil and protein in the corn combine in the processing, which also improves the action of enzymes on the starch.
The result is extruded as a paste, which is combined with an alcohol to extract corn oil and zein. After extraction, water is added to the remainder to dissolve the starch and sugars. Insoluble bran fiber and protein (gluten) are filtered out of the solution. The purified starch stream can then be used for ethanol production or other products.
Chen has been working on the system for decades, having been granted the first patent related to the system in 1989. While the Chen-Xu process differs from existing milling methods, it’s just a new way to use existing technology, he says. “If you look at the procedure, it is different,” he adds. “But technology wise there is nothing new in the world. You just put different technology together, that’s it.”
Inventions and processes developed at Purdue University are commercialized through the Purdue Research Foundation. The foundation licensed the Chen-Xu process to Bio Processing Technology, which is headed by Purdue emeritus professor John Tse. “This company was formed to bring the Chen-Xu process to commercial production,” he says. “It takes a lot of effort and we have now gotten to that point.”
Tse is excited by the potential for the new process to increase ethanol production while reducing pollution. “This is a new process that has no problems in the manufacturing process like the traditional dry-grind and wet-milling methods,” he says. “With this method, we don’t produce distillers grains. The problem with manufacturing distillers grains is that it comes after the fermentation process and distillation and is not environmentally friendly. A Minnesota plant was fined in 2002 for violations of the Clean Air Act. They were forced to install control devices. We don’t have this problem because we don’t manufacture distillers grains.” The emissions from the plant will be much lower than traditional plants, Elder says. “We don’t have lower pollution problems, we essentially have no pollution problems,” he says. “We don’t even need thermal oxidizers.”
Water consumption will also be lower than traditional plants because the corn doesn’t need to be soaked in water to dissolve the starch. “We will probably use a third less water than a traditional ethanol plant,” Elder says. “For one thing, we will recycle everything. We don’t have any wastewater that will run outside of the plant.”
The coproducts of the Chen-Xu process are corn oil, gluten, fiber and zein. “Our coproducts are extracted before fermentation,” Tse says. “All these are food- and pharmaceutical-grade. They are not like distillers grains, which is just animal feed for cows. Therefore our coproducts will bring in much more in sales than distillers grains. It will make the sales of our coproducts that much higher than a dry-grind ethanol plant can get from distillers grain.”
The process extracts starch completely from the corn kernel which means more ethanol can be made from a bushel of corn. In dry-grind plants, a small amount of starch remains unconverted in the distillers grains. According to Chen, plants should be able to make 2.85 gallons of ethanol from a bushel of corn, which is slightly higher than the current industry average. Elder thinks production could even exceed 3 gallons per bushel. Another advantage of the process is the projected lower cost of the system, which Tse estimates is 40 percent less than a dry-grind ethanol plant.
Operating costs should be lower as well, Tse says, because of the inherent efficiency of the process. Because the starch is already partially hydrolyzed before it enters the fermentation tank, the throughput time of the process is much quicker. “From the time we feed the corn in, to the time the ethanol comes out, the total is less than 24 hours,” he says. “It’s a more efficient way of manufacturing ethanol so the processing cost is cheaper than the traditional dry-grind method.”
Bio Processing Technology signed a sublicense agreement with Reed-Three Rivers Bio-Grain in September 2007 to use the Chen-Xu technology in its ethanol plants. The agreement is unusual in that Reed-Three Rivers Bio-Grain is taking the process from the bench scale to full production without testing it first in a pilot or engineering-scale demonstration plant. “We are skipping the pilot plant that many people think we would need,” Tse says. “We have experts working on this. We will be able to get a turnkey construction contract from one of the largest chemical and pharmaceutical contractors in the world. So there’s a guarantee for the output.” Elder says they don’t need to build a pilot plant because they know what they’re doing and they have confidence in the technology. “We wouldn’t be messing with this if we weren’t absolutely certain of the technology,” he adds.
The company turned to builders from the pharmaceutical industry because Elder thought they were more suited to design these plants than the major design/build companies in the ethanol business. “We’ve got to be very careful with the people we bring in to do the building on this,” says Elder, who declined to name the company. “They understand what has to go in to maintain the quality in these things.” Most of the information about how the company plans to implement the process is proprietary, Elder says. “This is a brand new technology,” he says. “We’re taking it from test tubes and beakers through to commercialization.” Reed-Three Rivers Bio-Grain plans to break ground on the new plant shortly after New Years in Danville, Havana or Greenville, Ill. The company is also looking at sites in Henry, Ill., Paducah, Ky., Gila Bend, Ariz., and three sites in Indiana for future plant development. The nine proposed plants will each have a capacity of 240 MMgy, more than double the capacity of a typical large-scale ethanol plant. “It’s an economy of scale matter,” Elder says. “With the Chen-Xu method and the byproducts that are put out besides ethanol, it became obvious that the economy of scale worked better at the 240-million-gallon range than any other. In fact, some of these plants may expand beyond that.”
The plants will also use drier technology owned by the Reed Klondike Group so they can take in corn harvested at 38 percent moisture. Elder says corn harvested at that moisture level contains more starch. “Therefore we will be able to get more ethanol production out of a bushel of corn than other plants simply because we get more starch up front,” he says. “It’s going to be nice for farmers. We’re going take the corn after about 90 days, and I think south of the St. Louis area there are going to be many farmers who will be able to double crop their land in a year.”
Because these facilities will be working with high-quality products they will need to employ about 205 people, which is more than a typical ethanol plant. “These products are all food- or pharmaceutical-grade materials,” Elder says. “There are no automatic functions here. In most dry-mill plants, the only byproduct is [distillers grains] and you can handle that about any way you want. But with pharmaceutical-grade materials, it has to be handled carefully and monitored all the time.”
Building a new technology from scratch has its challenges. “Finding and redesigning equipment to meet our needs has been a challenge,” Elder says. “But fortunately we have run into many manufacturers who are willing to work with us on this and do what’s necessary to get their equipment to do what we need it to do. Another challenge is to get anyone to take you seriously with the number of plants that get announced and don’t get built. But we are up to the challenge and our plants are going to get built. Our funding is all in place.”
Elder says his group was planning to build a traditional dry-grind ethanol plant about 18 months ago before learning about the Chen-Xu process. He believes the process will permanently change the ethanol industry. “This is a paradigm shift in the way ethanol is produced,” he says. “It’s a far better process than anyone has seen before. I think it will make ethanol a far more viable product in the U.S. and the world market. It is a much more elegant method and is certainly the cleanest process I’ve ever seen. I think a lot of people are going to look at it and be amazed at how well it works, how efficient it works and how profitable it is.”