In David Hodge’s lab at Montana State University (MSU), one can find fragments of olive pits, tubes filled with chipped-up poplar wood and bales of corn stover, which includes the plant’s stalks, leaves and cobs. What all these have in common is lignin — a plant compound that’s one of the most abundant organic molecules on Earth.
In plants, lignin is like the marshmallow goo holding together a Rice Krispies treat, explains Hodge, an associate professor in the Department of Chemical and Biological Engineering in MSU’s Norm Asbjornson College of Engineering. It’s the reason trees, which are made mostly of complex sugars, can stand upright, resist pathogens and not collapse into mush when the wood absorbs water, he said.
In other words, nature makes ready use of lignin. But in human industry, and especially in the production of biofuels such as ethanol, lignin is primarily a waste product, something that’s left over at the end of the process and burned, Hodge says.
“We’re interested in getting more value from lignin,” he says.
And so are the U.S. departments of energy and agriculture, which have funded multiple grants for Hodge and his collaborators. The latest, a $1.8 million Department of Energy grant awarded in March, is supporting a project with Clemson University and Michigan State University to develop new approaches for extracting and purifying lignin found in corn stover and poplar wood to make renewable, bio-based materials such as the spongy foam found in mattresses.
That project and others involve a basic process: cooking ground-up plant matter under controlled conditions in a mix of water and various chemicals that break the material down.
“There are a lot of similarities with making paper,” Hodge says.
Besides foams, lignin has the potential to be made into adhesives, carbon fibers and the plastic widely used in beverage bottles, a material normally made from petroleum. It can even be made into artificial vanilla. And those are just some of the known applications, Hodge said.
According to Jeff Heys, chemical and biological engineering department head, the research is particularly relevant for Montana, where agriculture supplies an abundance of discarded plant material that could become useful for its lignin, including wheat, barley and potatoes.
“The potential to grow our own raw materials could have a transformative impact,” says Heys, who grew up on a farm in the Gallatin Valley. “We increasingly need alternative sources of raw materials for our fuels, plastics and other products.”
Another upshot, according to Hodge, is that producing ethanol could become more economical and less reliant on the sugar-rich parts of plants that could otherwise be used as food for people or animals. Most of the ethanol added to gasoline in the U.S. is made from the starch in corn kernels. By making it from stover or other non-food plant material and then processing the lignin into a feedstock for other products, the whole process becomes more commercially viable.
One reason for a new wave of interest in biofuels is their potential to support rural economies while reducing greenhouse gas emissions, Hodge notes. When fossil fuels are burned, new heat-trapping carbon dioxide is released into the atmosphere. With plant-derived biofuels like ethanol, a comparable amount of carbon dioxide is absorbed by the new crop.
“One way of looking at all this is from the angle of sustainability,” Hodge says. “Chemistry is what makes the products and fuels that we use every day. If you can find better ways to do chemistry, you can have an impact.”
Source: Montana State University
