Particle size characterization of ultrasonic treatment of dry milling coproducts for enhanced biofuel production

This study characterized the use of ultrasonic energy to increase the production of the methane as a biogas from the anaerobic digestion of coproducts of dry milling. Dried distillers grain with solubles (DDGs), solids, thin stillage, and corn syrup were treated with various ultrasonic conditions and compared to untreated (control) samples. The amplitude ranged from 52.8 ympp to 160 ympp and the time was varied from 10 to 50 s. The resulting samples were characterized using scanning electron and optical microscopy (SEM, OM) and particle size analysis. Samples consisting of solid/liquid suspensions (DDGs, solids) showed a significant decrease in particle size (44.5% decrease in DDGS and 42.9% decrease in solids) and an associated increase in the surface area to volume ratio, thus promoting anaerobic digestion for enhanced biochemical methane production (BMP). In addition, thin stillage and corn syrup exhibited a slight increase in the peak particle size. It should be noted that the overall mean particle size decreased (65.73% decrease in syrup, and 74.57% in thin stillage) despite that the peak particle size increased. This observation is counter intuitive to ultrasonic treatment and is believed to be the result of oil agglomeration after being released from lipid bio-layers