Scientists convert biodiesel byproduct glycerin into ethanol

Recently, a way to connect the ethanol and biodiesel industries was revealed when it was determined that biodiesel could be a value-added product for ethanol plants through corn oil extraction technology (previous post). But now the link is reversed: researchers at Rice University in Houston have developed a way to convert glycerin (glycerol), a byproduct of biodiesel production, into ethanol. Both sectors are now linked and could create synergies that make both more efficient.

The glycerin-to-ethanol pathway is seen as promising, which is why the scientists behind it formed Glycos Biotechnologies to commercialise it. Once considered a valuable co-product, crude glycerol is rapidly becoming a 'waste product' with a disposal cost attributed to it - a result of the biodiesel boom.

Ramon Gonzalez and Syed Shams Yazdani have identified the metabolic processes and conditions that allow a known strain of Escherichia coli to convert glycerin into ethanol through an anaerobic fermentation process. Gonzalez is currently the William Akers assistant professor in chemical and biomolecular engineering at Rice University, and Yazdani is a postdoctoral research associate. They publish their findings in Current Opinion in Biotechnology.

In a comparison of feedstock and operating costs, Gonzalez found that ethanol from glycerol is 39 cents cheaper to produce than ethanol from corn. Feedstock costs per gallon were 53 cents for corn, versus 30 cents for glycerol. Per gallon operating costs were 52 cents for corn and just 36 cents for glycerol. The main reason for the difference in costs is that there is no preprocessing. In feedstock operations, the corn must be ground and cooked, and the sugar extracted. It is a process that is both capital and process intensive: one needs to work all the way from the corn grain to arrive at the sugars, and then start the fermentation. Meanwhile, glycerin doesn't require those steps because it comes preprocessed. This means no enzymes to buy and less equipment.

The implications of this research are so promising that the process may be commercialized before cellulosic ethanol. Gonzalez partnered with Paul Campbell, who researches, develops and markets blends of microbes for industrial, agricultural and environmental markets, to form Glycos Biotechnologies Inc. The company, which was funded by Houston-based venture capital fund DFJ Mercury, expects to complete its pilot plant in early 2008:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: ethanol :: biodiesel :: glycerin :: anaerobic fermentation ::

"Once we have the pilot running and working properly, [commercialization] is a matter of months," Gonzalez says, noting that the pilot plant is being designed to be one step away from a commercial-scale plant. Gonzalez couldn't say how big the pilot plant will be, but he says it would be capable of fermenting at least 10,000 liters.

Glycos Biotechnologies will not develop and sell the technology, Gonzalez says. Instead, the company plans to form partnerships with those already in the biodiesel, glycerin and ethanol industries, he says. The company's Houston location lends itself well to working with biodiesel producers, as there are several in the region.

Gonzalez says this process could be collocated with either an ethanol or biodiesel facility, and there are advantages to each. If collocated with a biodiesel plant, costs to transport glycerin would be saved. At least initially, this will be the most likely deployment of the company’s technology.

Glycerol is the principal component of glycerin, a clear, odorless, viscous liquid. It is found in animal fats, vegetable oils or petrochemical feedstocks, and is derived through soap production and the transesterification process, in which fatty acids and alcohol are mixed. Although glycerin has more than 1,000 uses, including many applications as an ingredient or processing aid in cosmetics, toiletries, personal care, drugs and food products, it is typically used in a highly refined and purified form. Refined glycerin is mostly pure glycerol, with the salt, methanol and free fatty acids removed.

The rapid growth of the biodiesel industry changed the glycerin market. In fact, it was cited as the reason that Dow Chemical Co., which produced synthetic glycerin, exited the glycerin production business in North America in 2006. "The increased supply of glycerin in North America due to biodiesel production, which caused prices to drop, was a factor in that decision," says Catherine Maxey, business public affairs director for Dow Chemical. "However, we continue to produce synthetic glycerin in Europe for sales into specialized markets such as pharmaceutical, personal care and food applications, among others, where high quality is the major requirement. The high purity at constant quality levels of Dow's synthetic glycerin presents distinct advantages over natural glycerin in these specialized end applications."

Maxey's point about glycerin quality is important when considering the market for the biodiesel by product. Biodiesel production yields unrefined glycerin. Biodiesel producers will usually then boil the glycerin to recover the methanol. This results in what is called crude glycerin, which is the form of glycerin most biodiesel producers sell. "[In most commercial applications], the quality of the glycerin must be high," says Gonzalez. "It can't be the nasty thing that comes out of biodiesel plants. If you use a feedstock that is not pure oil in biodiesel production, the glycerin is not very nice." Glycos's technology, however, can use the "nasty" glycerin—both unrefined and crude.

The Process
Gonzalez became interested in glycerol while he was an associate professor at Iowa State University. His initial research philosophy was to develop a microbial fermentation process for converting a low-cost, high-carbon feedstock into something with a higher value—not necessarily ethanol. Glycerol was targeted as the carbon source because it is the byproduct of an established and growing industry.

According to a report by Gonzalez and Yazdani, glycerol is competitive with sugar used in the production of chemicals and fuels via microbial fermentation at its current price, which is about 2.5 cents per pound. Additionally, glycerol has yield advantages over sugar due to the highly reduced nature of carbon atoms. "A pound of sugar won't contain enough energy to produce a pound of ethanol, because it also makes carbon dioxide," Gonzalez explains. "With a half-pound of glycerol, you still get a half-pound of ethanol."

Once glycerin's advantages as a feedstock were established, Gonzalez set forth to find the product. "Once we decided on glycerol, we had to see what we could do with it," Gonzalez says. He knew it could be fermented, and indeed, that it could be fermented into ethanol. This is not the first time that glycerin has been successfully fermented into ethanol. It was first done in 1877, using fungi as the agent. In his report, Gonzalez says many microorganisms are able to metabolize glycerol in the presence of external electron acceptors, but few are able to do so fermentatively. Gonzalez discovered one microorganism that could — E. coli. In previous studies, researchers had been unable to successfully convert glycerol to ethanol with the bacteria. "The major find is that we found conditions that enable a native, nonpathogenic strain of E. coli to [ferment glycerol to ethanol] without oxygen," Gonzalez says. "We don't need to do much genetic engineering to have ethanol as the main product."

Initially, the researchers didn't engineer the genetics at all, and focused instead on finding the appropriate environment that would allow a wild-type, common, nonpathogenic strain of E. coli ferment glycerol. "The key is not the type of strain, but rather the fact that we were able to create an appropriate environment," Gonzalez says. The environmental conditions include an acidic pH, avoiding accumulation of fermentation gas hydrogen and appropriate medium composition. With the right environment, ethanol is the primary product from glycerol fermentation with E. coli.

"Since we have that fermentation already going, now we can tweak or engineer the E. coli to produce items beyond ethanol," Gonzalez says. Currently, Glycos is focusing on commercializing the technology to produce ethanol, with the coproducts being formic acid and hydrogen.

"The value of formic acid is higher than ethanol," Gonzalez says. It can make hydrogen, and it's also being researched for use in fuel cells. Glycos Biotechnologies is also developing microbial platforms which will convert glycerin into other high-value chemicals.

Eventually, Gonzalez says he would like to produce succinic acid, a four-carbon molecule that can be converted into a variety of high-value biobased chemicals or materials. "If you take all the glycerin and turn it into succinic acid, you make much more money than with ethanol," he says. However, the market is still right for ethanol. "What I have found is that producing ethanol from glycerin is appealing for a lot of people in the biodiesel industry because there is a market for ethanol," Gonzalez says. "There might be a product of higher value, but that product may not have an established market and there's a lot of risk in that."

Even if this technology takes off, it's limited by the growth of the biodiesel industry, an industry that is struggling under the weight of high feedstock prices. There is certainly an oversupply of crude glycerin with respect to today's market, but not enough to satisfy the demand for ethanol on its own. The production of 1 million gallons of biodiesel generates about 100,000 gallons of crude glycerin. The biodiesel industry has built the capacity to produce 1.68 billion gallons of biodiesel, and thus 168 million gallons of crude glycerin. Since the conversion rate of glycerol to ethanol is about 1 to 1, approximately 168 million gallons of ethanol would be produced in a year if all available crude glycerin from biodiesel production were converted into ethanol.

More significant than the amount of ethanol produced is where it would be produced. This technology could bring ethanol to regions that were previously less accessible. Biodiesel production facilities, which are not as dependent on being close to feedstock sources as ethanol facilities, are disbursed throughout North America along coasts and in major port locations—usually close to population centers. For example, neither Texas nor New Jersey have any ethanol facilities in operation, but they do have 150 MMgy and 74 MMgy of biodiesel production capacity, respectively. Converting crude glycerin to ethanol could supply locally produced ethanol to markets like Houston, San Francisco and Las Vegas.


Other researchers have found cost-effective ways to use crude glycerin as feedstock for new types of biopolymers, bioplastic films, and green specialty chemicals such as propylene glycol. Others found glycerin makes for a suitable cattle and poultry feed or for the production of biogas.


Image: Because of its ubiquity, E. coli is frequently studied in microbiology and is the current "workhorse" in molecular biology. Its is widely used in genetic engineering and enzymes extracted from it are used industrial fermentation processes.

References:
Yazdani SS, Gonzalez R, "Anaerobic fermentation of glycerol: a path to economic viability for the biofuels industry", Current Opinion in Biotechnology, Vol. 18, Issue 3, June 2007, Pages 213-219. doi:10.1016/j.copbio.2007.05.002

Biopact: GS CleanTech to produce biodiesel from corn ethanol co-product - October 23, 2007

Biopact: The bioeconomy at work: Dow develops propylene glycol from biodiesel residue - March 19, 2007

Biopact: Students patent biopolymer made from biodiesel and wine byproducts - June 20, 2007

Biopact: Researchers make biodegradable films from biofuel and dairy byproducts - June 11, 2007

Biopact: Researchers study effectiveness of glycerin as cattle feed - May 25, 2007

Biopact: Biodiesel byproduct glycerine makes excellent chicken food - August 04, 2006

Biopact: Glycerin as a biogas feedstock - December 27, 2006