Fermentable sugars production from peach tree prunings: Response surface model optimization of NaOH alkaline pretreatment

Abstract

Among lignocellulosic residues, peach tree prunings are widely abundant in Italy, due to an extensive production and a high yield of prunings per cultivated hectare; thus, it represents an interesting feedstock for no food derived ethanol.In the whole production process, the pretreatment is the most critical step from technical and economic point of view. In this work peach tree residues were submitted to alkaline pretreatment, in order to maximize the fermentable sugar recovery and thus to maximize the theoretical etOH yield evaluating the best operative conditions in terms of NaOH concentration, temperature, and reaction time.The analysis is carried out by means of Response Surface Methodology approach, in order to optimize the pretreatment step. The optimal predicted conditions to perform the process were NaOH concentration = 0.200 mol dm-3, temperature = 125 °C and reaction time = 35 min, that allowed to obtain a theoretical ethanol yield of 223 L t-1 of dry peach tree pruning.This theoretical yield can be judged satisfactory in the context of forest and pruning biomass and it could be further increased by a future scale up from laboratory to pilot scale.