Mechanical fragmentation of wheat and rice straw at different scales: Energy requirement in relation to microstructure properties and enzymatic hydrolysis

Abstract

Mechanical fragmentation is an important pretreatment step in lignocellulosic biorefinery. In this study, we explored the energy requirement (ER) for mechanical fragmentation of wheat and rice straw at different scales in relation to modifications of microstructure properties and enzymatic hydrolysis. The ER showed a reciprocal relationship with mean particle size (MPZ), but a negative linear relationship with cellulose crystallinity (CrI). An exponential relationship was observed between the ER with a specific surface area (SSA) and the oxygen-to-carbon surface ratio (O/C). The results showed that modification of the cellulose crystallinity required the most energy consumption, whereas reduction of particle size consumed the lowest energy. The order of importance of modifications of different microstructure parameters on the ER was: CrI > O/C > pore volume (PV) > SSA > MPZ. Sugar yield showed a clear, positive linear relationship with ER, indicating that grinding patterns with a high ER could significantly enhance the enzymatic hydrolysis yield owing to the plant cell wall deconstruction. The energy efficiency declined with an increasing ER because of the markedly lower increase in sugar yield compared with the corresponding increase in ER.