UC student explores ways to extract biofuels from trees

The Environmental Protection Agency’s Renewable Fuel Standard mandates that the U.S. produce 36 billion gallons of biofuels annually by 2022, with 16 billion of those gallons coming from cellulosic biomass – or nonedible plants, like trees and bushes. Harvesting biofuels from trees can be a way to reduce dependence on foreign oil while investing in a renewable resource.

Currently, engineers use harsh acids or bases to make ethanol from trees at a 40 percent conversion rate. University of Cincinnati student Bryan Keller (chemical engineering ’21) hopes to find an efficient, inexpensive and environmentally friendly alternative to the ethanol production process from wood chips.

Keller has spent the last two summers researching ways to release sugars from trees to create biofuels. He originally became involved in the research through UC’s Protégé Program, a program that gives outstanding first-year students in the College of Engineering and Applied Science (CEAS) the opportunity to work with faculty in their labs over the summer.

UC Associate Professor of Environmental Engineering Maobing Tu, Ph.D., assigned Keller the project concerning advanced biofuel development from renewable biomass.

Ethanol is created through the fermentation of sugars within plants, which requires bacteria to reach the sugars to start the fermentation process. The problem with releasing these sugars from trees is getting to the sugars in the first place. Lignin structures, which are a plant’s defense against chemical attacks in nature, tightly bind themselves to tree’s sugars.

“Think of the sugars inside a tree as a baseball and the lignin as a hand holding the baseball. The lignin covers the sugars, and the bacteria and enzymes can’t really get to it,” says Keller.

The only way to get to these sugars, therefore, is by breaking up the lignin with acid or enzymes. Tu assigned Keller to experiment with and test safer alternative to some of the harsher acids currently used in the ethanol conversion process: Urea.

Urea is a common and, therefore, inexpensive compound derived from urine. Mixing urea with water creates a substance that is neither acidic nor alkaline. “The project was a guess that we hoped would work,” says Keller. However, after running multiple tests, Keller found that the urea operated at a 24 percent conversion rate, 16 percentage points less than the current chemical process.