Realising Biorefineries Using Hydrodynamic Cavitation Based Biomass Pre-treatment

Biorefineries are critical to achieving net zero emissions. To realise the true potential of biorefineries, biomass pre-treatment is important as it helps in maximising biomass conversion to high value products. Current biomass pre-treatment strategies use conventional methodologies that are either expensive, energy intensive or use harsh environmentally unfavourable chemicals. Hydrodynamic cavitation (HC) is a promising physico-chemical method that can pre-treat a variety of biomasses and can overcome these limitations. HC has been proven to enhance the biomethane potential, biohydrogen potential, saccharification and bioethanol yields as well as enhanced yield of value-added fermentative products such as lactic acid.

HC can be realised in a flowing liquid (or slurries) by lowering its local pressure to attain (or fall below) the vapour pressure. The generated microbubbles in these low-pressure regions grow and finally implode upon pressure recovery. The implosion of bubbles give rise to high-speed jets leading to intense shear and cleavage of water molecules leading to the production of highly oxidising radicals. Such conditions pre-treat the biomass physico-chemically. The extent of pre-treatment is dependent on the operating conditions and it has been proven that HC is energy efficient and is scalable for biomass pre-treatment. With individual process such as biofuel production and high value product production explored in the past, there is still a gap in utilising HC for integrated biorefinery applications. With the recent publication from Nagarajan and Ranade (2022) establishing that as received fibrous biomass can be pre-treated by HC, the scope of exploiting HC for biorefineries seems plausible than ever before. This work therefore brings together the possibilities and discusses the potential avenues where HC can be harnessed for biorefinery applications thereby contributing towards net zero emissions.