Ultrasonic pretreatment on biogas production from wood-dust mahogany (swietenia mahagoni) with solid-state anaerobic digestion method: effect of time and pretreatment temperature

Abstract

The availability of fossil energy as the main energy source makes its availability running low. One alternative energy source is biomass and it can be converted into biogas through a solid-state anaerobic digestion process. One of the many biomass types found in Indonesia is the wood-dust mahogany. The content of lignin contained in wood-dust mahogany makes the process of hydrolysis runs slowly. This causes the biogas production rate to be slow. This study examined the effects of temperature and duration of ultrasonic pretreatment on the characteristics of wood-dust mahogany and the rate of biogas formation along with kinetic study. This research was conducted in three stages, beginning with characterization stage to know the character of wood-dust mahogany, followed by ultrasonic pretreatment stage with time variation (10,20,30) minutes without heating and with heating temperature 70°C. The last stage was fermentation by using bioreactor for 60 days. The biogas produced was measured volume in every two days and the data obtained were used to create a biogas production kinetics simulation by using Gompertz and Richards modification models. The results of the evaluation indicated that the ultrasonic pretreatment process leaded to changes in surface morphology and wood-dust mahogany structure has a positive impact on increasing the rate of biogas formation. The longer the time and the higher the temperature of the ultrasonic pretreatment leaded to an increase in the rate of biogas production. The kinetic model of Richards modification equation gave the result of R2 0.999-0.985 value better than Gompertz modification equation model which is only 0.998-0.968.