Lignocellulosic ethanol production from the recovery of stranded driftwood residues

This paper builds upon an on-going research project funded by the Italian Ministry of Environment, and aiming at recovering stranded driftwood biomass, in order to transform a potential pollution and safety issue into valuable bio-resources. In particular, one of the experiments consisted in the bioethanol production from lignocellulosic residues. The stranded driftwood was gathered from the Italian coast (Abruzzo) after an intense storm. The biomass recalcitrance, due to its lignocellulosic structure, was reduced by steam explosion pretreatment process. Four different pretreatment severity factors (R0) were tested (LogR0 3.65, 4.05, 4.24 and 4.64) in order to evaluate the pretreated material accessibility to enzymatic attack and the holocellulose recovery. A first enzymatic hydrolysis was performed on the pretreated materials by employing a solid/liquid ratio of 1% (w/w) and an enzyme dosage of 30% (g enzyme/g cellulose), in order to estimate the maximum enzymatically accessible cellulose content. Since the primary goal of pretreatment and hydrolysis is to convert as much cellulose as possible into monomeric glucose, the two pretreated materials, showing the highest percentage of cellulose conversion were selected for bioethanol production process. The pretreated materials underwent a semi-simultaneous saccharification and fermentation (SSSF). The SSSF process was performed into two lab-scale bioreactors (5 L) with solid/liquid ratio of 15% and enzyme dosage of 15% for five days. The efficiency of the whole bioethanol production process was assessed as ethanol overall yields (g ethanol/100 g raw material).