Anaerobic digestion of corn silage on a commercial scale: Differential utilization of its chemical constituents and characterization of the solid digestate

The utilization of different chemical constituents of corn silage during industrial-scale anaerobic digestion was determined. Corn silage together with the resulting solid digestate generated during biogas production were collected from an industrial plant during a regular operating period. Moisture, water and ethanol extractives, ash, total nitrogen, starch, cellulose, the monomeric composition of hemicellulose, acid soluble and acid insoluble lignin were measured in both corn silage and corn silage solid digestate. The relative consumption of each component of corn silage during its anaerobic digestion was estimated with reference to acid insoluble lignin. It was assumed that lignin was not digested throughout the process. Starch and large fractions of extractives and acid soluble lignin were digested. In contrast, the digestion of cellulose and particularly hemicellulose were limited (40% and 29% respectively). Of the hemicellulose monomers, xylose was the least digested (20%). The present work shows that the digestate produced by commercial corn-silage anaerobic digestion contains a notable quantity of cell wall polymers. These could potentially be used in biorefinery processes, e.g. ethanol and xylooligosaccharide production.