Glycerin: Research Turns Up New Uses

Researchers worldwide are stepping up efforts to develop new uses for crude glycerin. Once commercialized, these technologies have the potential to improve the economics of biodiesel production.
By Erin Voegele | February 10, 2009
One-tenth of every gallon of biodiesel that is produced is crude glycerin. The biodiesel byproduct is a colorless, odorless, viscous liquid that has traditionally been used in the manufacturing of a wide variety of products in the food, cosmetic and pharmaceutical industries. The supply of crude glycerin entering the U.S. marketplace remained relatively stable until 2003, when biodiesel production began to increase. Since then, the supply of crude glycerin has nearly doubled, while demand for the product has remained largely unchanged. This excess supply and limited demand has caused glycerin prices to remain depressed.

These market conditions have made it difficult for most biodiesel producers to realize economic benefits through the sale of their main byproduct. However, businesses and researchers from around the globe are currently engaged in research and development projects, with the primary goal of developing economically viable technologies capable of utilizing this overabundant resource. Once commercialized, these technologies, including the use of glycerin as a fuel to power generators, as a feedstock for plastics and as a carbon source for the production of omega-3 fatty acids, should increase the profits of biodiesel producers by creating a new revenue stream.

Omega-3 Fatty Acids
Zhiyou Wen, an assistant professor of biological systems engineering with Virginia Tech's College of Agriculture and Life Sciences, is developing a technology that will use glycerin to aid in the production of algae that produce omega-3 fatty acids. The project originated about four years ago at Washington State University, where Wen worked with Shulin Chen, a professor with Washington State University's Biological Systems Engineering Department, to produce an omega-3 fatty acid known as docosahexaenoic acid (DHA). Wen has since moved to Virginia Tech, and begun to focus his work on another omega-3 fatty acid, known as eicosapentaenoic acid (EPA).

Wen's technology focuses on glycerin as a carbon source, which is used to grow a microalgae species that produces omega-3 fatty acids. Although many people associate fish oil with omega-3 fatty acids, fish don't actually synthesize it-they accumulate it by eating the algae that produce it. According to Wen, the technology currently available to produce EPA from algae is cost prohibitive. "Our hypothesis is that once we optimize this process the cost will be reduced," Wen says. That's because his technology uses glycerin, which is a relatively low-cost waste stream, rather than a more expensive carbon source such as glucose.

The omega-3 fatty acid containing biomass produced through Wen's technology could be used as animal feed, and research has proven that this concept will work, Wen says. When animals are fed the omega-3 fatty acid containing algae, they also become a source of the substance. They could potentially extract the omega-3 fatty acids from the biomass for inclusion in other food products, such as cheese or yogurt, however, the extraction process is relatively expensive.

Although Wen's technology doesn't require the use of refined pharmaceutical-grade glycerin, the soap and methanol present in crude glycerin must be removed before it can be used to aid in the algae growth. According to Wen, the technology's production process automatically removes these impurities. "The pH of the crude glycerol is pretty high," he says. "It's about 12 to 13, around that range. In order to grow the algae, we have to adjust the pH. When you adjust the pH of this medium containing crude glycerol, the soap contained in the glycerol will be precipitated out of the medium." In other words, the process used to adjust the pH of the solution causes the soap to solidify and settle out of the glycerin.

Before it can be used to cultivate algae, the glycerin must be sterilized. To accomplish this, the solution is heated. The boiling point of methanol is quite low, approximately 60 degrees Celsius (140 degrees Fahrenheit), Wen says. The technology requires the glycerin solution be heated to 120 degrees Celsius (248 degrees F), which causes the methanol to evaporate. "The soap and the methanol are relatively easy to remove," Wen says. "So, we think this process shouldn't be that complex in terms of impurity removal."

The technology yields approximately 0.2 to 0.3 units of biomass for each unit of glycerol it consumes. Omega-3 fatty acids account for approximately 10 percent to 15 percent of that biomass. "I think right now we have proven the concept," Wen says. A patent for the technology to produce DHA was filed in conjunction with Chen at Washington State University. Research on the production of EPA is not as far along, however, Wen has also filed a patent for that technology.

Glycerin as a Fuel
A newly developed technology in the U.K. allows glycerin to be burned in off-the-shelf diesel generators that are used in combined-heat-and-power applications. The technology was developed by U.K.-based Aquafuel Research Ltd. According to Paul Day, Aquafuel's chief executive officer, the technology is now commercially available.

The process uses standard diesel generators, which are altered slightly to run on a new combustion cycle, which is referred to as the McNeil cycle. "The basics of the engine, the fuel injection, the pistons and cylinder are not changed at all," Day says.

Only minor alterations need to be made to the crude glycerin before it is used to fuel the generators. "Crude glycerin contains 3 [percent] to 8 percent catalyst salts, and these salts need to be removed," Day says. However, the glycerin does not need to be fully refined. The technology is tolerant to water, methanol and nonglycerin organic compounds.

Although existing distillation technology used to remove these salts is available, Aquafuel is also working to develop a low-cost alternative. This alternative chemical-based method would use membranes to separate the salts from the glycerin. According to Day, the new technology would use approximately one-fifth of the energy used by traditional purification methods. While the company's distillation technology has been proven on a lab scale, it is not yet commercially available.

Day estimates that 1 ton of glycerin will produce approximately 1.7 megawatt hours of electricity and approximately 2 megawatts of heat. In addition, the process creates few emissions.

There are many advantages to using glycerin as a fuel. "It is nontoxic, biodegradable, and has a high flash point," Day says. In addition to being used at biodiesel refineries, the technology may be applied to other entities that use combined-heat-and-power systems, such as schools, hospitals and apartment buildings.

The technology was developed through a two-year research and development program that Aquafuel completed with Greenergy, a U.K.-based biodiesel producer. According to Day, the technology is expected to be installed at a biodiesel refinery by the second half of 2009. "Overall, the technology offers producers a chance to unlock revenue from glycerin streams, and at the same time improve its environmental performance," Day says. "That is a rare and welcome combination."

Glycerin in Plastics
Another European company is working on a technology that would use glycerin as a feedstock to produce plastics. Ireland-based Biobode Ltd. is developing this technology.

According to Scott O'Connor, Biobode's chief executive officer, the process his company is developing would produce commodity plastics that contain 20 percent to 38 percent glycerin. The remainder of the plastic material would consist of low-cost commodity chemicals.

Lab-scale research is currently being completed that can produce 1 kilogram batches of the glycerin-based plastic. The next step will be scaling up to producing 5 kilogram batches. "We are going to build a 5 kilogram reactor within the next six months," O'Connor says, at which point the technology will be proven. Once the technology is proven, the next step will be to license it to third parties who will build pilot facilities, he says.

O'Connor says it has historically been difficulty to use glycerin to make plastics because the process created a cross-linked polymer with no significant commercial value. "This has been a persistent limitation with glycerol since the 1930s," O'Connor says. The company has been able to overcome this problem and produce a high molecular-weight polymer.
While traditional plastic materials are 100 percent petroleum-based, 44 percent of Biobode's plastic could be sourced from nonfossil, nonpetroleum feedstocks, O'Connor says. The technology has been tested using both refined and crude glycerin, which was sourced directly from biodiesel producers. The only difference that results from the use of crude glycerin is some discoloring of the plastic material.

Biobode has been working to develop the technology for more than two years, and has successfully injection-molded test components with the material to prove the concept. The technology also uses a traditional reaction process. "We envision it could be applied within the existing infrastructure," O'Connor says.

O'Connor says biodiesel producers need to become more proactive in investing in glycerin technologies. "It's all about the opportunity that glycerol offers to increase the competitiveness of the biodiesel business model," O'Connor says. "I think that when a biodiesel producer finds a higher value for glycerol, it will affect his bottom line. Thus the effect on his competitiveness will be tremendous."

Erin Voegele is a Biodiesel Magazine staff writer. Reach her at [email protected] or (701) 738-8040.
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