The samples were characterized with scanning electron and optical microscopy (SEM, OM) and particle distribution analysis (PDA). The ultrasonic amplitude was varied from 52.8 µmpp to 160 µmpp and the sonication time was varied from 10 to 50s! It was found that with solid/liquid suspensions (DDGS, solids), there was a significant decrease in particle size, increasing the surface area to volume ratio, to possibly enhance biogas yield during anaerobic digestion of these materials. This study evaluates the change in particle size of dry-milling corn ethanol co-products by using ultrasonic energy to increase the production of the biogas from the anaerobic digestion of ethanol dry-milling co-products, namely: dried distiller grain with solubles (DDGS), solids, thin stillage, and corn-syrup. In the case of thin stillage and corn syrup, the results were surprising in... The co-product samples were treated with various ultrasonic conditions and compared to non-treated samples (control sample).