Ending Biodiesel’s Glycerin Glut

By Jade Boyd

Call it an alternative fuel’s alternative fuel.

U.S. biodiesel production is at an all-time high, and a record number of new biodiesel plants are under construction, but the industry is facing an impending crisis over waste glycerin, the major byproduct of biodiesel production.

“The biodiesel business has tight margins, and until recently, glycerin was a valuable commodity — one that producers counted on selling to ensure profitability,” said Ramon Gonzalez, the William W. Akers Assistant Professor in Chemical and Biomolecular Engineering.

But that dynamic has changed. “One pound of glycerin is produced for every 10 pounds of biodiesel,” he said, “and that has caused a glycerin glut.” Many manufacturers not only are unable to sell glycerin, but also must pay to dispose of it.

Researchers across the globe are racing to find ways to turn waste glycerin into profit. Some are looking at traditional chemical processing, such as using catalytic reactions that break glycerin into other chemicals, while others are focusing on biological conversion, in which a microorganism is engineered to eat a specific chemical feedstock and excrete something useful. Many drugs are made this way, and the chemical processing industry is increasingly finding bioprocessing to be a “greener,” and sometimes cheaper, alternative to chemical processing.

Gonzalez and his colleagues might have found such a solution to the glycerin glut. “We identified the metabolic processes and conditions that allow a strain of the bacterium E. coli to convert glycerin into ethanol,” Gonzalez said. “It’s also very efficient. We estimate the operational costs to be about 40 percent less that those of producing ethanol from corn, and the process will show higher yields and lower cost than can be obtained using common sugar-based feedstocks like glucose and xylose.”

Gonzalez’s report on the research, co-authored by postdoctoral research associate Syed Shams Yazdani, appears in Current Opinion in Biotechnology. Graduate students Yandi Dharmadi and Abhishek Murarka assisted with the research, which is funded by the U.S. Department of Agriculture and the National Science Foundation.