Process-driven optimisation of an integrated lignin-first biorefinery

Biomass is a promising feedstock for sourcing renewable carbon to produce biobased chemicals and materials. However, conventional extraction processes often lead to low utilization efficiencies of biogenic atoms due to the irreversible degradation of lignin. Aldehyde assisted fractionation (AAF) addresses this challenge by protecting the native β-O-4 linkage of lignin with an aldehyde. This biorefining process simultaneously produces aromatic monomers at near-theoretical yields, functionalized hemicellulosic sugars with applications in the plastic industry, and highly crystalline cellulose (Manker et al., 2022). We conduct techno-economic and life cycle assessments based on process simulation results to identify cost drivers and major environmental burden of the AAF biorefinery. 25% of CO2 emissions are linked to energy demands for concentrating the hemicellulose liquor after lignin precipitation and filtration. At lab- and pilot-scale, excess of water is indeed introduced to prevent lignin agglomeration. Process modeling revealed the high heat duty, and associated equipment costs (10% of total production costs), for evaporating this water, necessary for plastic monomer production. By reducing the water-to-biomass ratio from 5.5 to 2.5 and implementing a mechanical vapor recompression system to replace steam with electricity, we foresee a 37% decrease in the minimum selling price of lignin monomers and a 97% cut in global warming potential, assuming unchanged lignin monomer yields. We experimentally validate the simulation results and further investigate the trade-off between water reduction and high productivity. Overall, this study integrates lab work with process modeling to inform experiments with plant-level considerations, accelerating the scale-up of novel biorefineries.