Characterization and structural analysis of alcohol-fractionated lignin biofuels processed at ambient temperature

This study introduces Cold-processed Lignin in (M)ethanol Oil (CLEO/CLiMO), a novel biofuel technology derived from the alcohol-fractionation of lignin at ambient temperatures, offering a sustainable alternative to conventional marine fuels. The production process achieved solid loadings of up to 60 wt% lignin and a volumetric energy density 39 % higher than pure alcohols. Lignin concentrations above 30 wt% promoted colloidal stability through the proposed formation of a spanning network of lignin aggregates, associated with a 100-fold increase of viscosity. Additionally, we observed a decrease in the radius of gyration of lignin particles from 2.5 to 2.7 nm at 30 wt% to 1.1–1.3 nm at 60 wt% following a transition from globular to elongated random coil shaped particles. This was accompanied by a twofold increase in the partial specific volume of lignin, suggesting a reduction in packing efficiency. The study highlights CLEO's potential as a sustainable shipping fuel alternative, combining favorable fuel properties with a simple and scalable production method.