Vol.:(0123456789) 1 3 International Journal of Environmental Science and Technology https://doi.org/10.1007/s13762-018-1928-z ORIGINAL PAPER Glycerine supplementation as a recovery strategy of long‑chain fatty acids inhibition on anaerobic digestion N. Rasit 1  · A. Idris 2  · W. A. Wan Ab. Karim Ghani 2  · S. Hamzah 1 Received: 17 April 2017 / Revised: 25 June 2018 / Accepted: 18 July 2018 © Islamic Azad University (IAU) 2018 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 efects 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 infuence 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 (R GS ), measured as lag phase, can be shortened to 4 days during the start-up as compared to the control reactor (R control ). With the reduction in lag-phase occurrence, the performance of R GS reactor afected the overall methane production. At standard temperature and pressure, R GS reactor performance of methane composition was 67%, with methane production rate of 0.376 LCH 4 /L day and methane yield of 0.19 LCH 4 /gCOD removed . 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. Keywords Grease trap waste · Anaerobic · Glycerine · Supplementation · Start-up · Semicontinuous feeding Introduction Anaerobic digestion is one of the potential processes of waste lipid recovery for benefcial use to produce biogas. However, despite its likelihood in increasing biogas yield, lipid hydrolysis may be inhibited by the formation of long-chain fatty acids (LCFA) and the destabilization that occur during the methanogenesis phase, hence reducing its biodegradability potential (Angelidaki and Ahring 1992; Pereira et al. 2005). During the hydrolysis stage, the lipid is essentially degraded by hydrolytic bacteria which degrade the triglyc- erides in lipid to produce fatty acids (long-chain fatty acids, LCFA) and volatile fatty acids (Alves et al. 2009). Due to the degradation, the accumulation of LCFA became a rate- limiting factor in the anaerobic system. This is because the transport limitation for cell wall absorption will reduce its solubility thus causing several operational problems dur- ing the methanogenesis stage. Oleate and palmitate are the culprits since their accumulation is identifed as the main cause of inhibition. It was reported that their accumulation in low level over 100 mg/L included the inhibited anaerobic digestion of sewage sludge (Martínez et al. 2012) and cattle manure (Angelidaki and Ahring 1992; Palatsi et al. 2009). The destabilization is detected when there is a presence of lag phase during methane formation and the formation of biomass foatation (Hwu et al. 1998; Long et al. 2011; Palatsi et al. 2010). As a result, the methane production is Editorial responsibility: Gobinath Ravibdran. * N. Rasit nazaitulshila@umt.edu.my 1 School of Ocean Engineering, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu Darul Iman, Malaysia 2 Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor Darul Ehsan, Malaysia