Pretreatment of milled and unchopped sugarcane bagasse with vortex based hydrodynamic cavitation for enhanced biogas production

Anaerobic digestion can potentially valorise sugarcane bagasse to biogas and fertiliser. Pretreatment is however required to overcome recalcitrance and enhance the biogas yields. Literature reporting the investigation of various biomass pretreatments often use milled biomass as substrate rather than as-received fibrous biomass. This does not establish the true influence of the pretreatment type on biogas generation. Additionally, milling energy is also ignored when calculating net energy gains from enhanced biogas yields and are thus misleading. In this work, a vortex-based hydrodynamic cavitation device was used to enhance the biomethane yields from fibrous as-received biomass for the first time. Clear justification on why milled biomass must not be used as substrates for demonstrating the effect of pretreatment on biogas production is also discussed. The net energy gain from milled hydrodynamic cavitation pre-treated bagasse can be similar to as-received bagasse only when the specific milling energy is <= 700 kWh/ton.

Automated summary

Anaerobic digestion has the potential to convert sugarcane bagasse into biogas and fertiliser. However, pretreatment is necessary to enhance biogas yields. Previous studies often use milled biomass as substrate, which cannot demonstrate the true effect of pretreatment on biogas production. This study introduces the use of a vortex-based hydrodynamic cavitation device to enhance biomethane yields from fibrous as-received biomass, and provides clear justification for not using milled biomass as substrates to evaluate the effects of pretreatment on biogas production.