Glycerine supplementation as a recovery strategy of long-chain fatty acids inhibition on anaerobic digestion

Abstract

In anaerobic digestion, less attention has been focused on the digestion of grease trap waste as a single substrate may be due to high lipid content that may cause inhibition effects resulted from long-chain fatty acids accumulation during the degradation of lipid. The inhibition results in the low and slow production of methane. This study investigates the influence of glycerine supplementation on the continuous stir tank reactor anaerobic treatment of grease trap waste. The operating procedures began with a start-up process and continued with a semicontinuous feeding process in an increasing organic loading rate of 1.3–3.6 gCOD/L day. The results showed that the resistance toward grease trap waste inhibition in a glycerine-supplemented reactor (RGS), measured as lag phase, can be shortened to 4 days during the start-up as compared to the control reactor (Rcontrol). With the reduction in lag-phase occurrence, the performance of RGS reactor affected the overall methane production. At standard temperature and pressure, RGS reactor performance of methane composition was 67%, with methane production rate of 0.376 LCH4/L day and methane yield of 0.19 LCH4/gCODremoved. These results were observed at an organic loading rate of 2.2 gCOD/L day. The overall methane production enhancement from the glycerine-supplemented reactor was 25%. Palmitate accumulation indicated the possible main inhibitor during the lag-phase experience. Furthermore, the system was able to recover methane production performance during semicontinuous feeding stage. The use of glycerine supplementation is a reliable strategy to induce the start-up of anaerobic digestion process of high-lipid substrate.