Effective suspension layer in ultrasonic treatment of plant bioresources

The task of finding the rational parameters of plant raw material processing to increase the production of biofuel efficiency does not lose its importance. Experimental studies on ultrasonic cavitation treatment of plant raw materials in the technology of obtaining a promising second-generation biofuel (biobutanol) were conducted. Rapeseed straw was used as a characteristic crop. The study used an ultrasonic cavitation unit with a capacity of 4.93 litres and emitters with a total power of 720 W and an ultrasonic frequency of 28 kHz. The ultrasound intensity was 2.2 W·cm. The weighted average particle size of rapeseed straw was 0.78 mm. The dry matter content in the aqueous suspension was 10%. As a result of the study, it is established that the layer of suspension in the working chamber of the ultrasonic cavitator has a significant impact on the efficiency of biobutanol production. The effectiveness of this factor increases with increasing the duration of ultrasonic treatment. Compared with the control, the specific content of biobutanol was 1.22 ± 0.04 g·l and 1.24 ± 0.03 g·l for the treated layer of 0.03 and 0.12 m, respectively. Fermentation of the untreated material allowed to obtain 0.73 ± 0.04 g·l of butanol. However, for the duration of processing at the level of 25 minutes, there was a significant increase in the amount of the obtained biobutanol for the effective layer of suspension in the cavitation chamber at the level of 0.03 m (up to 1.57 ± 0.09 g·l) at almost unchanged values for the layer of 0.12 m. These trends were confirmed in the treatment of the suspension with 5% dry matter content, where for the effective layer of the suspension of 0.12 m butanol yield was 1.63 ± 0.06 g·l increasing to 2.44 ± 0.09 g·l for the layer of 0.03 m. The yield of butanol after fermentation of untreated rapeseed straw biomass with 5% dry matter content was 0.24 ± 0.02 g·l.