(572b) How Green Is My Lignin? Critically Benchmarking Lignin Biorefining Processes Via Green Chemistry Metrics

Lignin, constituting 15-30 wt% of terrestrial biomass, is the planet's most abundant biogenic resource for aromatic chemicals. Despite its potential, lignin's heterogeneous macromolecular structure poses challenges for selective chemical modification and valorization. Various lignin biorefining technologies, such as organosolv, reductive catalytic fractionation (RCF), pyrolysis, and oxidation, have been developed to deconstruct lignin into value-added aromatics, thereby supporting the advancement of bio-economies. However, the sustainability of these technologies is often overlooked.

This presentation critically benchmarks these prominent lignin biorefining technologies by evaluating their process performance and greenness using mass-based green chemistry metrics. Aromatic monomer yields serve as a benchmark for comparing the relative energy and material footprints of competing technologies in deconstructing lignin into small aromatics. Liquid-phase processes exhibit high material footprints due to significant solvent consumption, underscoring the need for integrated solvent recycling steps. Conversely, conventional thermal processes like pyrolysis reduce solvent consumption and operate with relatively fast process times, demonstrating lower material footprints and favorable energy economies compared to emerging technologies. Overall, this study provides insights into the trade-offs between process productivity and sustainability in biorefining technologies and identifies challenges impeding sustainable biorefining through a quantitative, mass-based assessment.