Abstract
Structural and compositional characteristics of substrate in anaerobic digestion are known to limit the hydrolysis step. This can be countered by the use of pretreatment prior to the commencement of anaerobic digestion process. In this instance pretreatment step assists in the increase of the degradability of the substrate. Thus accelerating hydrolysis and improving methane yields Ultrasonic pretreatment is a type of mechanical treatment mainly employed for surface area increase through solid particles disintegration. This is achieved by the use of grinding methods. In this work, the main objective was to investigate how ultrasonic pretreatment affects the biogas yield. Three sonication times of (10, 20, 45 min), operated at 20 MHz and an amplitude of 8 µm were used on fruit and vegetable waste inoculated with sludge.BMP tests were performed on ultrasonic pre-treated substrate, with total solids (%TS) of 17.9%, volatile solids (%VS) of 82.1 % ,moisture content of 82.1 % and C/N of 26%. The tests were performed in batch reactors, at mesophilic temperature of 35 °C. In this work, the batch time of 13 days was sufficient to complete the process of digestion. The highest cumulative methane production was 238 ±7.64 mL/g VS, which occurred at 45 min sonication time. This yield is 43 % higher than the untreated sample. 20 minutes for pretreatment sonication time, resulted in the cumulative methane production of 210.4 ±3.82 mL/g VS. Finally, sonication time of 10 minutes resulted in the least methane yield of 173 ±3.18 mL/g VS, with only 22 % increase in the yield. These results led to the conclusion that in this instance, an increase in ultrasonic pretreatment time, resulted in an increased the methane yield.
