A patent that opens the door for the creation of biofuels from abundantly available plant fiber has been issued to researchers at the Wisconsin Institute for Sustainable Technology (WIST) at the University of Wisconsin-Stevens Point.
WIST’s first patent is for a process that makes biofuels and other products from cellulosic plant material, including agricultural residues such as corn stover or plants grown specifically for fuel production, such as hardwood and softwood trees. The process is also a key step in making other high-value bioproducts.
“This gives us an economically viable way to use grass, trees or wood waste to make renewable fuels and chemicals,” said Eric Singsaas, associate professor of biology at UW-Stevens Point and co-inventor of the process, along with Don Guay, associate professor of paper science and engineering. “It also gives us a method to commercialize some of the work we’ve done at the university.”
With its focus on interdisciplinary, collaborative work on creating sustainability solutions for business and industry, WIST is working with the UW’s WiSys Technology Foundation to license the intellectual property to private industry for development.
The patent protects a method that uses an aqueous solvent to separate biomass into pure cellulose and lignin, the substance that gives woody biomass its rigidity. The lignin-solvent mixture can then be separated from the water to form a high-energy-density fuel that can be used independently or combined with biodiesel.
The pure cellulose can be used conventionally, such as in paper making, or it can be converted to fermentable sugars. The sugars can be used to make biofuels but can also be used to make other renewable chemicals for industry including isoprene, currently derived largely from petroleum and used in the making of rubber, plastics and pharmaceuticals.
“We’re not just making fuel,” Singsaas said. “We’re making value-added products.”
Other techniques exist to separate lignin from cellulose and have long been used in the paper industry. However, these traditional processes result in cellulose that contains inhibitors that make it more difficult to convert it to sugars. Similarly, the lignin produced contains additional chemicals not easily or economically separated.
WIST’s lignin-solvent process results in a purified lignin and pure cellulose. Besides being easier to convert to biofuels, the pure materials are more readily useable to produce other renewable chemicals. In conventional paper plants, the lignin typically is burned to recover the inorganic chemicals from the pulping process and for energy. But Guay says there may be higher-value applications for the pure lignin recovered in the WIST process.
“Down the road there are potential uses for that lignin,” Guay said. “It may be used to make carbon fiber, for example. As an added bonus, the new lignin-solvent process can regenerate the solvent to make the overall process self-sustaining.”
The lignin-solvent process is just one aspect of the WIST biofuels project. The goal is to develop a biorefinery that could be fitted to existing paper mills or give new life to idled mills.
“We designed this specifically so you could do this by minimally modifying paper mill infrastructure,” Singsaas said. Mills would gain additional revenue sources, add jobs and help grow the regional economy.
“We’ve done this process in the lab,” Singsaas said. “We’ve done it at a small pilot scale. The next step is to seek partners to develop this into a demonstration-scale plant.”