Fall 2006

BIOREFINERIES DEVELOPED to produce ethanol from cellulose sources such as trees and fast-growing plants could get a significant economic boost from the sale of high-value chemicals – such as vanillin flavoring – that could be generated from the same feedstock. Revenue from these “side stream” chemicals could help make ethanol produced by biorefineries cost-competitive with traditional fossil fuels.

photo by Gary Meek Georgia Tech researchers are exploring the use of three environmentally friendly solvent and separation systems to produce specialty chemicals, pharmaceutical precursors and flavorings from a small portion of the ethanol feedstock. The green processes could produce chemicals worth up to $25 a pound.

“It seems unlikely that fuel from a biorefinery – at least in the beginning – is going to be as cost-effective as fuel from traditional fossil sources,” says Charles Eckert, a professor in the School of Chemical and Biomolecular Engineering at the Georgia Institute of Technology. “To make the biorefinery sustainable, we must therefore do everything we can to help the economics. If we can take a chemical stream worth only cents per pound and turn it into chemicals worth many dollars per pound, this could help make the biorefinery cost-effective.”

To help make that happen, Eckert and collaborators Charles Liotta, Arthur Ragauskas, Jason Hallett, Christopher Kitchens, Elizabeth Hill and Laura Draucker are exploring the use of three environmentally friendly solvent and separation systems – gas-expanded liquids, supercritical fluids and near-critical water – to produce specialty chemicals, pharmaceutical precursors and flavorings from a small portion of the ethanol feedstock. The green processes could produce chemicals worth up to $25 a pound.

“These are novel feedstocks for chemical production,” Eckert notes. “They are very different from what we’ve dealt with before. This gives us different challenges and provides a rich area for interdisciplinary research.”

Using near-critical water and gas-expanded liquids, Eckert and his colleagues have already demonstrated the production of vanillin, syringol and syringaldehyde from a paper mill black liquor side stream. They have also proposed a process that would generate levulinic acid, glucaric acid and other chemicals from the pre-pulping of wood chips. That process would use an alcohol-carbon dioxide mixture, followed by depolymerization and dehydration in near-critical water.

Research aimed at producing high-value products from cellulose feedstocks is being done through the “AtlantIC Alliance for BioPower, BioFuels and Biomaterials,” a coalition formed by Oak Ridge National Laboratory, Imperial College London and Georgia Tech.

The Alliance is taking a comprehensive approach to the biorefinery, conducting studies of how to maximize plant growth through genetic engineering, developing new microbial techniques for digesting cellulose, and applying environmentally friendly chemical processes for reactions and separations. The organizers decided to pursue only non-food sources as their feedstock.

Though many challenges remain before biorefineries can be designed and built, it is important to invest now in this renewable source of energy and chemicals, Eckert says.

“The biorefinery is one of several answers that we need to pursue as part of a national energy strategy,” he adds. “Our future economic well-being requires us to deal with the energy issue.”