The way plant matter is prepared before it reaches a biorefinery can determine how much of its energy and chemical value is ultimately recovered. In new work led by Vijay Singh at the University of Illinois at Urbana-Champaign, researchers report a revised pretreatment strategy that targets one of the most persistent obstacles in biofuel production: the inefficient handling of lignin. The study, carried out within the Center for Advanced Bioenergy and Bioproducts Innovation, shows that a milder chemical approach can separate lignin from biomass while preserving its native structure, improving the prospects for producing both fuels and higher-value bioproducts.
Raj, T., Sharma, P., Thompson, S., Dien, B. S., & Singh, V. (2026). Green pretreatment strategies for enhanced microbial lipid fermentation and synergistic high-quality lignin recovery for next-generation integrated biorefineries. Chemical Engineering Journal Advances, 25, 101031. https://doi.org/10.1016/j.ceja.2025.101031
Biofuels derived from plants rely on the conversion of lignocellulosic biomass, which is mainly composed of cellulose, hemicellulose, and lignin. Cellulose and hemicellulose can be broken down into sugars and fermented using established processes. Lignin, however, is far more resistant. Its complex, cross-linked polymer structure gives plants mechanical strength and water resistance, but that same structure makes lignin difficult to process without damaging it. As a result, much of lignin’s potential chemical energy is lost during conventional treatment.
Vijay Singh at the University of Illinois at Urbana-Champaign stated,
“Other BRCs are taking this native lignin and catalytically breaking it down and feeding it to other microorganisms to produce other chemical products … our NADES pretreatment is able to preserve that lignin, which can then go for these other high-value products. This is CABBI’s contribution to the shared research objective.”
Standard industrial pretreatment methods typically use high-temperature, high-pressure water-based processes to open up plant fibers. While effective at releasing fermentable sugars, these methods also alter lignin’s chemical makeup. Once degraded, lignin fragments tend to recombine into dense, less reactive materials that are difficult to convert into useful chemicals. This not only reduces the overall efficiency of the process but also increases energy demand and operating costs.
Singh and his colleagues explored an alternative based on natural deep eutectic solvents, a class of liquids formed by combining naturally derived compounds that interact to create effective solvents at relatively low temperatures. When applied to harvested biomass, these solvents were able to loosen and separate lignin without causing the extensive breakdown seen in hydrothermal treatments. Detailed chemical analysis confirmed that the lignin recovered through this method retained much of its original bonding and molecular architecture.
Preserving lignin’s native structure has important implications for downstream processing. Intact lignin is more suitable for conversion into aromatic and aliphatic compounds that can serve as precursors for fuels, polymers, and specialty chemicals. At the same time, the cellulose-rich fraction left behind is cleaner and more accessible for microbial fermentation into ethanol, biodiesel components, or other renewable fuels. The solvent-based process also requires less energy overall and relies on materials that can be recovered and reused multiple times, improving its practicality for large-scale use.
The researchers demonstrated the approach using Miscanthus, a perennial grass commonly studied as a bioenergy crop, but the method is not limited to a single feedstock. According to the team, the same principles can be applied to agricultural residues, woody biomass, and other plant materials. The gentler conditions also help preserve naturally occurring oils or engineered compounds within plants, allowing additional product streams to be recovered during processing.
While the study does not eliminate all of the technical and economic challenges facing advanced biofuels, it highlights how targeted improvements at early processing stages can have wide-ranging effects. By treating lignin as a resource rather than a byproduct, and by reducing the energy penalty associated with pretreatment, the work contributes to broader efforts to make integrated biorefineries more flexible, efficient, and commercially viable.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
