Characterization of Fermentation Residues from the Production of Bio-Ethanol from Lignocellulosic Feedstocks

Solid residues from the conversion of four lignocellulosic biomass feedstocks, Miscanthus, Switchgrass, hybrid poplar and red maple, to bioethanol in a pilot plant have been characterized for their lignin and carbohydrate content, heating value, ash content and inorganic elements profile. These residues have also been analyzed with solid-state C-13 NMR spectroscopy to understand their bulk chemical composition. The hemicellulose contents of residues from all four feedstocks are significantly lower than the untreated biomass, indicating utilization or degradation during the steam autohydrolysis pretreatment and bioconversion. Residues from red maple show the highest lignin content and heating value. All the residues have high ash content which includes very high proportions of Ca, P, K and S. The presence of these elements in these biofuel residues may challenge their use for combustion and will need to be addressed.