Pretreatment of Lignocellulosic Biomass Using Vortex-Based Devices for Cavitation: Influence on Biomethane Potential

Abstract

Lignocellulosic biomass (LCB) is an abundant renewable resource that can be used to produce fuels and chemicals. Valorization of LCB is, however, a challenge due to its recalcitrant nature posed by the strongly interlinked cellulose–lignin–hemicellulose structures. A range of physicochemical and biological LCB pretreatment methods has been reported in the literature for enhancing its bioutilization. In this work, we used hydrodynamic cavitation (HC) based on vortex devices as a chemical-free, environmentally friendly LCB pretreatment method to enhance biomethane production. A bench scale pretreatment setup using a vortex-based cavitation device was established for the pretreatment of two common LCBs: grass silage (GS) and sugar cane bagasse (SCB). Dried and powdered feedstocks were used in all the experiments. HC was carried out by operating the cavitation device at a flow rate of ∼1.5 m3/h. The feedstocks before and after pretreatment were characterized for morphological and compositional differences using a range of analytical techniques. Liquid phase products produced upon cavitation were also analyzed using an HPLC-RI. Biomethane potential (BMP) was measured for GS and SCB with and without pretreatment, and a first order model was used to describe the kinetics. Up to 40% enhancement was observed in BMP after cavitation pretreatment using vortex-based devices. A brief discussion on preliminary cost considerations based on the experimentally observed enhancement in BMP is included. The results indicate significant promise of harnessing hydrodynamic cavitation-based pretreatment using vortex-based devices for enhancing biomethane production from LCB.