The study uses ammonium sulfite-based alkali salts to convert corn stover - the leftover stalks, husks, and plant material from corn harvesting - into low-cost sugar for biofuel and bioproduct production, thereby enhancing the economic viability of the process.
Yang and colleagues from the University of Connecticut, the National Renewable Energy Laboratory (NREL), the USDA Forest Products Lab in Madison, and Washington University in St. Louis aimed to find a cost-effective way to convert cellulosic biomass, such as corn stover, into sugar.
Although biomass is abundant and inexpensive, processing it remains costly due to the difficulty of breaking down structural components like cellulose and lignin. Overcoming this challenge requires improved pretreatment technologies that can efficiently release fermentable sugars.
In this study, the team developed a method using potassium hydroxide and ammonium sulfite at moderate temperatures to pretreat corn stover. This pretreatment step helps enzymes break down cellulosic polymers into sugar, which can then be fermented into biofuels and other bioproducts, without the need for chemical recovery.
Their economic analysis showed that, when byproducts are used or sold to offset production costs, the resulting sugar could be produced for as little as 28 cents per pound, comparable to low-cost imported sugar.
“This patent-pending process produces high-quality fermentable sugar for the biorefinery - the industrial process turning plant matter into fuel - as well as fertilizer that can replenish soil nutrients for farmers. There’s no waste stream,” theorized Yang.
The study received funding from the U.S. Department of Energy’s Bioenergy Technologies Office.
In the next phase, we will be advancing our pretreatment technology at a pilot scale.
Xiaowen Chen, Scientist and Study Principal Investigator, NREL
Journal Reference:
Ma, S., et al. (2025) A chemical-recovery-free ammonium sulfite-based alkali pretreatment of corn stover for low-cost sugar production via fertilizer use of waste liquor. Bioresource Technology. doi.org/10.1016/j.biortech.2025.132402