Lignin extraction from waste biomass with deep eutectic solvents: Molecular weight and heating value

Abstract

Abstract Separating lignin from cellulose in biomass is a necessary pretreatment step prior to converting them to biofuels or bioproducts. If byproducts from food production can be separated in an ecofriendly solvent at low pressures, biomass specifically grown for biorefining will not need to be shipped long distances. Using deep eutectic solvents (DES) can separate out lignin from the non-food components remaining after agricultural production. This work investigated the efficacy of three DES on four food processing residues on lignin separation, characterizing the molecular weight and fuel value of the extracted lignins. DES pretreatments reduced molecular weight and increased the molecular weight distribution range (PDI) compared to the control black liquor derived lignin. The DES acetic acid: choline chloride (AACC) was most effective for reducing molecular weight and increasing PDI for rice husks and sugarcane bagasse, but a lactic acid: choline chloride DES improved these properties for coffee chaff, and formic acid: choline chloride DES improved them for corn stover. Higher heating values that were higher than the control black liquor derived lignin were found for lignins extracted from rice husks, sugarcane bagasse, and corn stover with AACC.