Abstract:
This research studied a biogas production from fats and oil anaerobic digestion with food waste. Experiments were performed in lab scale batch reactors, using 0.50 liters Duran bottles with 0.3 liters water. Sludge from Boon Rawd Brewery Co., Ltd. was added at a concentration of 20,000 mg/L with 2,000 mg/L palm oil and rice or soybean waste to represent carbon or nitrogen sources, respectively. Rice or soy waste were tested at concentrations of 0 1,000 2,000 and 4,000 mg/L. The biogas productions of oil, rice with oil, and soybean with oil were 0.23 0.42 and 0.72 m³/Kg-VS, respectively. Result showed that higher biogas productions were obtained with higher soybean concentrations. The biogas production rates followed the first order reaction with waste concentration. The first order constant (k1) of palm oil with rice and with soybean were 0.390 and 0.364 1/day, respectively. Addition of soy beans produced more biogas than addition of rice, their biogas production rates were 0.280 and 0.157 m³/Kg-VS/day, respectively. Addition of surfactant, Sodium dodecyl sulfate (SDS) at a concentration of 2,000 mg/L to completely dissolved oil into water, resulted in much longer period for biogas production. Lag phase were increased from 2-3 days to 30-50 days with similar biogas volume. This might be results from the inhibition of high soluble oil concentrations in water. Sludge wastage at 10%, 20%, 50%, and 90% volume were calculated to solids retention times (SRT) of 150, 75, 30, and 16.7 days, respectively. SRT of 16.7 days had the highest k₁ (0.56 1/d) with a similar biogas production rate (0.35 m³/Kg-VS), but had the longest lag period of 5 days, instead of 2 days for other SRT.