Effects of discharge characteristics and evaluation of pressure of shock wave on underwater discharge as pretreatment for enzymatic saccharification

Abstract

Abstract Cellulosic bioethanol produced from wood is a candidate for alternative fuel to fossil fuels. In the cellulosic ethanol production process, pretreatment before enzymatic saccharification should be introduced for acceleration of the process. We proposed a new pretreatment technique for the cleavage of inter-cellulose hydrogen bonds by underwater discharge shock waves. In this study, we quantitatively analyzed the relationship among discharge conditions, shock wave properties, and treatment efficiency to estimate the optimal treatment conditions. The shock wave pressure was measured at several MPa, and optical microscopy results suggested wood flour fragmentation. The relationship between the discharge characteristics and the treatment effect was investigated by measuring the water retention value as an indicator of hydrogen bond cleavage and the amount of glucose as bioethanol intermediate products. The discharge energy of 0.85–1.16 J/pulse did not affect the treatment effect, while an increased discharge frequency in the range of 3.3–7.3 Hz did. The independence of treatment effect on the discharge energy was investigated to arise from the saturation in the discharge-current rising rate and shock-wave pressure.