Optimization of biogas production in Indonesian region by liquid anaerobic digestion (L-AD) method from rice husk using response surface methodology (RSM)

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Abstract
Rice husk is one of agricultural waste that is potentially converted to biogas. In this research, rice husk is used as the material to produce biogas by liquid anaerobic digestion (L-AD) with TS concentration below 15/5. The purposes of this research are finding the optimum value of total solid (TS), C/N ratio, and microbial consortium (MC) for biogas production and then analyzing the optimum biogas production rate from rice husk. Because of the high lignin content, rice husk must be through the pretreatment stage using NaOH 3%. The variations of the observed factor are 5%, 10%, 15% for TS concentration; 20, 35, 50 for C/N ratio; and 3%, 6%, 9% for MC concentration. There are 16 reactors in which the variation for each reactor was determined by Central Composite Design. Data obtained from the research will be optimized using Response Surface Methodology (RSM) in Statistica 10. The result shows that the optimum condition of biogas production from rice husk is TS in between 1%-2.5%, C/N ration 33.45, and MC in between 5.5%-7%. Reactor having a combination of value factors that close to the optimum value will be analyzed using Polymath 6.0, which is reactor 10. The kinetics constant of biogas production rate (u) is 3.625 ml/grTS.day, the maximum biogas production (A) is 277.374 ml/gr TS, and the minimum time needed to produce biogas (λ) is 3.878 days.