Lignin, the tough organic material that binds the cells and fibers of plants, is the most widely occurring renewable source of carbon after cellulose. But its general unpopularity among industrial processes results in the disposal of approximately 40 to 50 million tons of lignin annually, according to the International Lignin Institute in Switzerland.
But researchers at the University of Wisconsin-Madison (UWM) want to make the biomaterial an alternative to petroleum-based fuels and chemicals. "Lignin is the only large volume renewable feedstock that contains aromatics,” said Shannon Stahl, a UWM chemistry professor and senior author of a related paper, in a press release. Derived primarily from petroleum, today's aromatics are used in the fabrication of products such as plastic bottles, Kevlar, and pharmaceuticals. The aromatics that make up lignin, however, can be broken down allowing it to be used as a base material in sustainable chemicals.
Stahl and his team recently unveiled a conversion process to do just that. They first expose lignin to oxygen and then treat it with a weak acid to loosen its tough chemical bonds. The procedure is complicated because too much or the wrong kind of acid will destroy lignin's desirable aromatic compounds. Additionally, the team determined that metal-free acids were most effective, increasing the opportunity for developing an affordable industrial method because processing metal-based acids is typically more expensive.
Stahl envisions a future in which biorefineries actively transform biomass, such as lignin, into usable fuels and materials, in lieu of today’s petroleum-based methods. "Most of the focus in this field has been on cellulose, but I don't think there will be sufficient value to compete with petroleum unless we can generate value from lignin, too,” Stahl said.
Blaine Brownell, AIA, is a regularly featured columnist whose stories appear on this website each week. His views and conclusions are not necessarily those of ARCHITECT magazine nor of the American Institute of Architects.