Thermochemical Conversion Technologies of Lignin

Driven by increasing energy vulnerability and severe climate changes, sustainable production of fuels, energy, materials, and chemicals from renewable or waste resources is urgently needed. Although lignin is an abundant biomass source, it is under-exploited and challenging to be valorized in the current biorefinery process. It has a naturally recalcitrant and complex structure, composing a cross-linked polymer of aromatic compounds, which accounts for 15-30% total weight and up to 40% total energy of lignocellulosic biomass. It is usually directly burned as a low-value solid fuel or even considered as waste. Effective depolymerization of lignin is regarded as one of the most significant challenges in lignin utilization. Thermochemical conversions, biological treatments, and chemical catalysis can be applied to break the linkages between lignin monomers to produce fuels, energy, materials, and chemicals. However, lignin has a complex chemical composition and is difficult to be effectively depolymerized. In addition, lignin upgrading to selectively produce targeted products remains a challenge. Therefore, novel and effective lignin depolymerization and conversion methods are urgently needed to fully realise lignin valorization. This Research Topic aims to bring the awareness of utilization and valorization of lignin in the concept of biorefinery, and highlight recent advances in thermochemical conversion methods as well as treatment, biological processes and combined approaches to produce value-added chemicals and fuels.

This Research Topic will provide a strategic vision of current state-of-the-art of lignin valorization, catalyze the transformative research within and between multiple disciplines, and accelerate the technology and engineering innovation of ‘Affordable and Clean Energy’ (UN’s Sustainable Goals 7). Manuscripts with an interdisciplinary perspective, addressing key challenges of energy, environment, and sustainability are welcomed. The collection aims to feature Original Research articles, Reviews and case studies.

The collection covers a range of topics:

• Lignin depolymerization methods, including thermochemical treatment, mechanical treatment, chemical depolymerization, and biological treatment.
• Lignin depolymerization mechanisms and chemical reaction kinetics
• Thermochemical conversion of lignin to produce fuels, chemicals, and functional materials
• Biological conversion of lignin to produce fuels and chemicals
• Process intensification strategies of lignin valorization
• Life cycle assessment and techno-economic analysis of lignin-derived products

Keywords: Renewable Energy, Sustainability, Circular Economy, Lignin Valorization, Thermochemical Conversion, Biological Conversion

Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.