Abstract

Corn, wheat and rapeseed are three crops from which notable quantities of residual biomass are obtained worldwide every year, e.g., corn stover is the most plentiful source of lignocellulosic biomass in the U.S., with only a portion removed from the field. These residues are a potential unexploited biomass resource, and contain cellulose, hemicellulose, and lignin as major components, but also contain wax compounds, and bioactive compounds such as vitamin E, phenolics, and carotenoids. However, since the composition of these residues is complex, the separation and fractionation are key issues for the efficient use of these materials. For this purpose, we propose using green techniques such as Supercritical Fluid Extraction (SFE) for extraction of valuable compounds; hydrothermal treatment (i.e. the organosolv process) to obtain Lactic Acid (LA), and separate fractionations of cellulose, hemicellulose and lignin; Deep Eutectic Solvents (DES) to selectively separate lignin form cellulose; and Hydrothermal Carbonisation (HTC) of lignin fractions to produce a polyaromatic/phenolic carbonaceous products. In this work different genotypes of corn, rapeseed, and wheat were evaluated. There were significant differences (p-value <0.05) among genotypes for biomass dry weight, cellulose, hemicellulose and lignin yields. The best genotypes for further processing showed cellulose and hemicellulose yields of 2.4 ton/ha for corn stover, and 5.9 ton/ha for wheat, and low lignin yields of 0.43 ton/ha for corn, and 1.4 ton/ha for wheat. Optimal parameters for the SFE of wheat straw and germ, corn stover and rapeseed cake were determined. In all cases, it was possible to extract >88% of the extractable material. Through the organosolv process and DES it was possible to obtain separated fractions of sugars, cellulose and lignin. Further fermentation of the sugars fraction (83% xylose) showed high yield of lactic acid (90%). Strength properties of fibrillated Acid-DES-treated corn stover were measured and best results were obtained for LA-base DES treated samples with tensile strengths in the range of 92.0–99.2 MPa. The HTC at 240 ºC of the lignin fraction from the organosolv process yielded 65% of solid material.