Bubbles break down biofuel biomass

CHEMICAL engineers at Tohoku University, Japan, have developed a new technique which uses bubbles to pre-treat lignocellulosic biomass for more efficient biofuel and chemical production.

Lignocellulosic biomass like wood chips, corn stover and wheat straw must be pre-treated before it can be used to produce biofuels and bio-based chemicals. Conventional pre-treatments are generally time-consuming and relatively inefficient, such as enzymatic processes, or else use harsh reagents and conditions. Kazunori Nakashima and his team say that their treatment is “promising” for use in industry.

The team first crushes dried maize leaves and stalks and mixes the powder into a solution of sodium percarbonate (SP). This mixture is passed through a 'hydrodynamic cavitation system', consisting of a circular flow system and a Venturi tube. Cavitation is the formation, growth and collapse of bubbles. As the mixture is forced through the Venturi tube, which narrows in the middle, bubbles form under pressure. As the mixture then passes through into the wider part of the tube again, the bubbles collapse, disintegrating the cellulose fibres.

Nakashima and the team have previously used sodium percarbonate and ultrasound to break down cellulosic fibres, however, they found that the hydrodynamic cavitation system is more effective at producing fermentable sugars like glucose and xylose. In addition, the researchers did not detect any furfural, which inhibits the growth of yeast, in the products, further proving the technique’s suitability as a pre-treatment for biofuel production. They say the system could be easily scaled up for use in industry.

The next stage of the research will be a more detailed look at SP concentration and pre-treatment temperature, and fine-tuning the process.

Industrial & Engineering Chemistry Research DOI: 10.1021/acs.iecr.5b04375