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Lignin Valorization in Biorefineries

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Green Chemistry".

Deadline for manuscript submissions: 31 May 2026 | Viewed by 1563

Special Issue Editors


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Guest Editor
Laboratory of Alternative Energy and Transport Phenomena (LEAFT), Chemical Engineering Department, Federal University of Rio Grande Do Norte (UFRN), Natal, RN, Brazil
Interests: lignin valorization; biorefinery; lignocellulosic biomass; catalyst; process intensification; mathematical modeling

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Guest Editor
Laboratory of Biochemical Engineering, Chemical Engineering Department, Federal University of Rio Grande Do Norte (UFRN), Natal, RN, Brazil
Interests: biorefinery; biomass pretreatment; second-generation ethanol; downstream processing

E-Mail Website
Guest Editor
Laboratory of Alternative Energy and Transport Phenomena (LEAFT), Chemical Engineering Department, Federal University of Rio Grande Do Norte (UFRN), Natal, RN, Brazil
Interests: biofuels; process intensification; mathematical modeling; biorefinery

Special Issue Information

Dear Colleagues,

Sustainable technologies are essential to mitigate the environmental damage caused by human activity. Several advances have been made over the years in utilizing plant-based biomass to produce high-value-added products, particularly cellulose and starch. However, lignin, a structural component of lignocellulose, remains underutilized to this day. Due to its high calorific value, lignin is primarily burned to produce heat and electricity in pulp and paper industries, with only a small portion used for low-return applications, such as dispersants and binders. Despite this, recent insights in the literature highlight that lignin is a natural and biocompatible macromolecule that offers various useful properties, including UV-blocking, antimicrobial, antiviral, and antioxidant effects. It can also be depolymerized into phenolic compounds, which can serve as platform molecules for further applications. There is a plethora of applications in which lignins could completely replace fossil-based materials, particularly in food, pharmaceutical, and biomedical sectors. More research efforts are needed to expand the use of lignin-based products and increase the income from production chains involving lignocellulosic biomass.

In this Special Issue, we seek papers that present original data on lignin valorization in a biorefinery context and review articles that provide a critical analysis of this field of research. We additionally welcome studies on the mathematical modeling, techno-economic assessment, and lifecycle assessment (LCA) of lignins. Papers that cover analytical methods employing lignins may be accepted as long as the valorization of the macromolecule is emphasized.

Dr. Carlos Eduardo De Araújo Padilha
Dr. Everaldo Silvino Dos Santos
Dr. Domingos Fabiano de Santana Souza
Guest Editors

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Keywords

  • pretreatment
  • bioactive compounds
  • antioxidant properties
  • kraft lignin
  • extraction
  • thermochemical processes

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Published Papers (2 papers)

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Research

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15 pages, 2602 KB  
Article
Insights into Real Lignin Refining: Impacts of Multiple Ether Bonds on the Cracking of β-O-4 Linkages and Selectivity of Products
by Yuancai Lv, Xuepeng Lin, Kai Yang, Yifan Liu, Xiaoxia Ye, Liang Song, Chunxiang Lin, Guifang Yang and Minghua Liu
Molecules 2026, 31(1), 133; https://doi.org/10.3390/molecules31010133 - 30 Dec 2025
Cited by 1 | Viewed by 459
Abstract
Depolymerizing lignin to produce high-value chemicals has garnered increasing attention. Given the complex structure of real lignin, the cracking efficiency of β-O-4 linkages and the selectivity of depolymerization products are significantly lower than those of lignin model compounds. Meanwhile, the relationship between [...] Read more.
Depolymerizing lignin to produce high-value chemicals has garnered increasing attention. Given the complex structure of real lignin, the cracking efficiency of β-O-4 linkages and the selectivity of depolymerization products are significantly lower than those of lignin model compounds. Meanwhile, the relationship between the structure of lignin and the β-O-4 linkage cracking was ignored. In this work, to well address the issue, three real lignins (corncob lignin (CL), pinus massoniana lignin (PML), and eucalyptus lignin (EL)) were employed to discuss the impacts of special ether bonds in lignin on the β-O-4 linkage cracking in the no-additional-hydrogen catalytic system mediated by a CoNi2@BTC catalyst. The lignin depolymerization results showed that the ether bonding structure in the lignin significantly impacted the cracking of β-O-4 linkages and selectivity of the final products, resulting in a great difference among their intermediates. Notably, the methoxy groups in the real lignin greatly inhibited the further hydrogenation of phenolic compounds, resulting in the accumulation of abundant methoxy-substituted phenolic compounds and a low yield of cycloalkanes (12.37% to 14.06%). To deeply discuss the β-O-4 linkage cracking in the lignin depolymerization, degradation experiments with coexisting ether bond compounds were performed, and the activation energy was employed to quantitatively evaluate the impacts of other ether bonds on the β-O-4 linkage cracking. The results revealed that multiple ether bonds (α-O-4, 4-O-5, and methoxy group) significantly increased the activation energy (from 236% to 373%) of β-O-4 linkages, resulting in the evident decline in the β-O-4 model compound. In addition, the degradation of the methoxy-substituted β-O-4 model compound (GG) demonstrated that the methoxy-substituted aromatic ring products were resistant to further hydrogenation, resulting in the accumulation of methoxy-substituted aromatic ring products in the depolymerization of real lignin. All the findings will provide a novel perspective for the targeted high-value utilization of real lignin in chemical production. Full article
(This article belongs to the Special Issue Lignin Valorization in Biorefineries)
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Review

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22 pages, 1209 KB  
Review
Advances in Integrated Lignin Valorization Pathways for Sustainable Biorefineries
by Mbuyu Germain Ntunka and Shadana Thakor Vallabh
Molecules 2026, 31(2), 380; https://doi.org/10.3390/molecules31020380 - 21 Jan 2026
Viewed by 642
Abstract
Lignin, the most abundant renewable source of aromatic compounds, plays a pivotal role in advancing sustainable biorefineries and reducing dependence on fossil resources. Recent progress in integrated lignin valorization pathways has unlocked opportunities to convert this complex biopolymer into high-value chemicals, materials, and [...] Read more.
Lignin, the most abundant renewable source of aromatic compounds, plays a pivotal role in advancing sustainable biorefineries and reducing dependence on fossil resources. Recent progress in integrated lignin valorization pathways has unlocked opportunities to convert this complex biopolymer into high-value chemicals, materials, and energy carriers, despite its structural heterogeneity and recalcitrance posing major challenges. This review highlights the significant advancements in depolymerization strategies, including catalytic, oxidative, and biological approaches, which are reinforced by innovations in catalyst design and reaction engineering that enhance selectivity and efficiency. It also discusses emerging technologies, such as hybrid chemo-enzymatic systems, solvent fractionation, and continuous-flow reactors, for their potential to improve scalability and sustainability. Furthermore, this review examines the integration of lignin valorization with upstream pretreatment and downstream recovery, emphasizing process intensification, co-product synergy, and techno-economic optimization to achieve commercial viability. Despite these developments, critical gaps remain in understanding the molecular complexity of lignin, developing universally applicable catalytic systems, and optimizing economic and environmental performance. To guide future research, it poses two key questions: how to design catalysts for selective depolymerization across diverse lignin sources, and how to configure biorefineries for maximum lignin utilization while ensuring sustainability? Addressing these challenges will be essential for lignin’s role in next-generation biorefineries and a circular bioeconomy. Full article
(This article belongs to the Special Issue Lignin Valorization in Biorefineries)
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