Eco-friendly dry chemo-mechanical pretreatments of lignocellulosic biomass: Impact on energy and yield of the enzymatic hydrolysis

Abstract

In this study, we developed an eco-friendly dry alkaline chemomechanical pretreatment of wheat straw without production of waste and liquid fractions with objective to save energy input, to decrease the environmental impact and to increase enzymatic hydrolysis.Wheat straw was pretreated with NH3, NaOHH2O2, NH3H2O2 and NaOH at high materials concentration (5kg/L) equivalent to biomass/liquid ratio of 1/5 (dry chemomechanical) and at low materials concentration (0.2kg/L) equivalent to biomass/liquid ratio of 5/1 (dilute chemomechanical). Untreated and chemical treated wheat straw samples were subjected to grinding and milling following by enzymatic hydrolysis with commercial cellulases.NaOH and NaOHH2O2 dry chemomechanical pretreatments were found to be more effective in decreasing the particle size and energy consumption and increasing the surface area. However, alkaline dilute-chemomechanical treatments consumed higher amounts of water (5L water/1kg biomass) and energy compared to dry-chemomechanical treatments. In point of fact, the lowest energy efficiency obtained was 0.417kg glucose kWh-1 for dilute-chemomechanical treatments compared to 0.888kg glucose kWh-1 glucose kWh-1 for dry-chemomechanical treatments.Alkaline dry-chemomechanical pretreatments approach appears more attractive and efficient in terms of glucose, energy efficiency and environmental impact, compared to conventional alkaline chemomechanical pretreatments. © 2013 Elsevier Ltd.