|  Q. Zhang, J. Hu, D.J. Lee, Biogas from anaerobic digestion processes:research updates, Renew. Energy 98(2016) 108-119. F. Xu, Y. Li, Z.-W. Wang, Mathematical modeling of solid-state anaerobic digestion, Prog. Energy Combust. Sci. 51(2015) 49-66. R. Chandra, H. Takeuchi, T. Hasegawa, Methane production from lignocellulosic agricultural crop wastes:a review in context to second generation of biofuel production, Renew. Sust. Energ. Rev. 16(2012) 1462-1476. K. Xiao, C. Guo, Y. Zhou, Y. Maspolim, J. Wang, W.J. Ng, Acetic acid inhibition on methanogens in a two-phase anaerobic process, Biochem. Eng. J. 75(2013) 1-7. I.S. Kim, M.H. Hwang, N.J. Jang, S.H. Hyun, S. Lee, Effect of low pH on the activity of hydrogen utilizing methanogen in bio-hydrogen process, Int. J. Hydrog. Energy 29(2004) 1133-1140. I. Angelidaki, D. Karakashev, D.J. Batstone, et al., Biomethanation and its potential, Methods Enzymol. 494(2011) 327-351. J. Fierro, E.J. Martinez, A. Moran, X. Gomez, Valorisation of used cooking oil sludge by codigestion with swine manure, Waste Manag. 34(2014) 1537-1545. Y. Li, S.Y. Park, J. Zhu, Solid-state anaerobic digestion for methane production from organic waste, Renew. Sust. Energ. Rev. 15(2011) 821-826. W. Li, K.-C. Loh, J. Zhang, Y.W. Tong, Y. Dai, Two-stage anaerobic digestion of food waste and horticultural waste in high-solid system, Appl. Energy 209(1) (2018) 400-408. Q. Wang, L. Peng, H. Su, The effect of a buffer function on the semi-continuous anaerobic digestion, Bioresour. Technol. 139(2013) 43-49. W. Li, High-solid anaerobic codigestion of horse manure and grass in batch and semi-continuous system, Energy Fuel 30(8) (2016) 6419-6424. H. Li, E. Larsson, E. Thorin, et al., Feasibility study on combining anaerobic digestion and biomass gasification to increase the production of biomethane, Energy Convers. Manag. 100(2015) 212-219. Z. Yao, W. Li, X. Kan, Y. Dai, Y.W. Tong, C.-H. Wang, Anaerobic digestion and gasification hybrid system for potential energy recovery from yard waste and woody biomass, Energy 124(2017) 133-145. S. Kataki, S. Hazarika, D.C. Baruah, Assessment of by-products of bioenergy systems (anaerobic digestion and gasification) as potential crop nutrient, Waste Manag. 59(2017) 102-117. G. Allesina, S. Pedrazzi, L. Guidetti, P. Tartarini, Modeling of coupling gasification and anaerobic digestion processes for maize bioenergy conversion, Biomass Bioenergy 81(2015) 444-451. L.A. Hadidi, M.M. Omer, A financial feasibility model of gasification and anaerobic digestion waste-to-energy (WTE) plants in Saudi Arabia, Waste Manag. 59(2017) 90-101. J. Mata-Alvarez, J. Dosta, S. Mace, S. Astals, Codigestion of solid wastes:a review of its uses and perspectives including modeling, Crit. Rev. Biotechnol. 31(2) (2011) 99-111. Z. Yong, Y. Dong, X. Dong, T. Tan, Anaerobic co-digestion of food waste and straw for biogas production, Renew. Energy 78(2015) 527-530. APHA, Standard Methods for the Examination of Water and Wastewater, American Public Health Association, Washington, DC, 2005. P.J. Van Soest, J.B. Robertson, B.A. Lewis, Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition, J. Dairy Sci. 74(1991) 3583-3597. P. Sensai, A. Thangamani, C. Visvanathan, Thermophilic co-digestion feasibility of distillers grains and swine manure:effect of C/N ratio and organic loading rate during high solid anaerobic digestion (HSAD), Environ. Technol. 35(20) (2014) 2569-2574. L. Zhang, Y.W. Lee, D. Jahng, Anaerobic co-digestion of food waste and piggery wastewater:focusing on the role of trace elements, Bioresour. Technol. 102(2011) 5048-5059. J. Zhang, K.-C. Loh, W. Li, J.W. Lim, Y. Dai, Y.W. Tong, Three-stage anaerobic digester for food waste, Appl. Energy 194(2017) 287-295. J. Zhang, W. Li, J. Lee, K.-C. Loh, Y. Dai, Y.W. Tong, Enhancement of biogas production in anaerobic co-digestion of food waste and waste activated sludge by biological copretreatment, Energy 137(2017) 479-486. W. Zhang, L. Zhang, A. Li, Enhanced anaerobic digestion of food waste by trace metal elements supplementation and reduced metals dosage by green chelating agent[S, S]-EDDS via improving metals bioavailability, Water Res. 84(2015) 266-277. F. Pinto, R.N. Andre, C. Carolino, et al., Effects of experimental conditions and of addition of natural minerals on syngas production from lignin by oxy-gasification:comparison of bench-and pilot scale gasification, Fuel 140(2015) 62-72.