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ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Sustainable Biofuels and Co-products Research » Research » Publications at this Location » Publication #426794
Research Project: Thermo-Catalytic Biorefining

Location: Sustainable Biofuels and Co-products Research

Title: Lignin conversion in thermochemical biorefining: A review of reactions, mechanisms, catalysts, and challenges

Author
item MANRIQUE, RAIZA - Oak Ridge Institute For Science And Education (ORISE)
item Mullen, Charles
item CHEJNE, FARID - National University Of Colombia
item OLARTE, MARIEFEL - Pacific Northwest National Laboratory
item GARCIA-PEREZ, MANUEL - Washington State University

Submitted to: Renewable & Sustainable Energy Reviews
Publication Type: Review Article
Publication Acceptance Date: 6/5/2026
Publication Date: 7/1/2026
Citation: Manrique, R., Mullen, C.A., Chejne, F., Olarte, M., Garcia-Perez, M. 2026. Lignin conversion in thermochemical biorefining: A review of reactions, mechanisms, catalysts, and challenges. Renewable & Sustainable Energy Reviews. https://doi.org/10.1016/j.fuel.2026.140268.
DOI: https://doi.org/10.1016/j.fuel.2026.140268

Interpretive Summary:

Technical Abstract: Lignin, a complex polyphenolic biopolymer, is a major component of lignocellulosic biomass, presenting both challenges and opportunities in biofuel and bio-based chemical production. Efficient conversion of lignin into valuable products requires a deep understanding of the reactions, mechanisms, and catalysts involved in thermochemical biorefining processes such as pyrolysis and hydrodeoxygenation (HDO). This review provides a comprehensive examination of the chemical reactions that occur during pyrolysis and HDO, including both homolytic and heterolytic pathways. Pyrolysis breaks down lignin into monomers and oligomeric compounds, while HDO upgrades these products by removing oxygenated functional groups through hydrogenation, producing hydrocarbons suitable for drop-in fuels. This review also highlights lignin composition before and after pyrolysis and HDO, the critical role of catalysts enhancing HDO efficiency, and the potential applications of upgraded pyrolytic lignin. Additionally, the challenges of selectively upgrading lignin-derived intermediates and the formation of undesirable products, such as o-quinone methide, are discussed. By examining the underlying mechanisms of lignin depolymerization and cracking, this review seeks to enhance control over the lignin conversion process and minimize the char formation.