Waste not, want not: Discarded plant material could replace petroleum in chemicals

An engineer at Washington University in St. Louis is looking at ways to use part of a plant’s cell wall to create chemicals and other materials to shift dependence on petroleum toward renewable resources.

Marcus Foston, assistant professor of energy, environmental & chemical engineering in the School of Engineering & Applied Science, has received a three-year, $224,970 grant from the National Science Foundation to find catalysts that will break down lignin, a tough part of the cell walls of woody and grassy plants, into chemicals that can be used as building blocks for materials. He will collaborate with Susannah Scott, professor of chemical engineering and of chemistry and biochemistry at University of California, Santa Barbara, who also received $225,000, bringing the total grant amount to $449,970.

Foston, who specializes in using lignin characterization and conversion, said plants developed lignin as a protective mechanism from microbes and fungi, so it is difficult to break down and is often discarded or burned for power or heat. Instead of wasting this material leftover from papermaking or bioethanol production, Foston is looking to pull it out of the cell wall to use its chemical structure for products.

“We are looking to develop catalysts and to understand the structures of catalysts that allow us to pull out the aromatic building blocks from lignin in a very selective way,” Foston says.

There are some methods to do this, but they require a lot of energy, and therefore are not selective, Foston says.

“These methods are similar to using a sledgehammer,” he says. “Because of that, you get secondary and tertiary reactions and a broad distribution of products. We want to use a scalpel and cut out specific components of the lignin, so ultimately we have a narrow distribution of products with higher yields of any one compound that we want. Maintaining the aromatic structure is key.”

Specifically, Foston and Scott will target the production of aromatic compounds such as benzene, toluene and xylene, which are petrochemicals commonly used in solvents or are the precursors for other types of chemicals and materials, such as Kevlar or polystyrene.

“My lab is focused on sustainability and the replacement or displacement of petroleum as feedstock for fuels, chemicals and materials,” Foston says. “The reality is that oil is a nonrenewable resource whose current rate of utilization will, at some point, have an irrevocable effect on our environment. Part of what we’re trying to do is specifically target nonfuel-type applications and to de-risk the biofuel industry to not only add value to the types of products we’re producing from plant biomass, but the diversity of the products as well.”

As part of the work, Foston will host “Researcher for a Day” events in his lab with local middle school students from groups underrepresented in the STEM fields, allowing them to do an experiment with biomass and learn about the conversion of biomass to useful products.

The School of Engineering & Applied Science at Washington University in St. Louis focuses intellectual efforts through a new convergence paradigm and builds on strengths, particularly as applied to medicine and health, energy and environment, entrepreneurship and security. With 90 tenured/tenure-track and 40 additional full-time faculty, 1,300 undergraduate students, more than 900 graduate students and more than 23,000 alumni, we are working to leverage our partnerships with academic and industry partners — across disciplines and across the world — to contribute to solving the greatest global challenges of the 21st century.