CIGR-AgEng conference Jun. 26–29, 2016, Aarhus, Denmark 1 Methane enhancement through AFEX pretreatment from wheat straw with waste activated sludge Muhammad Hassan a , Weimin Ding a* Esmaeil Mehryar a,b Zahir Talha a Li Xuhui a a College of Engineering, Nanjing Agricultural University, Nanjing, Jiangsu 210031, China. b Department of Bio-system Engineering, College of Agriculture, Isfahan University of Technology Isfahan 84156, Iran * Corresponding author. Tel +86-25 5860 6502, E-mail address: wmding@njau.edu.cn Abstract Wheat straw is an abundant agricultural biomass resource found worldwide. Different physical, chemical and biological pre-treatments were used to enhance the ethane production from wheat straw. Ammonia fiber explosion (AFEX) pretreatment was carried out in the present study with four levels and all levels were found significant (P< 0.05) to enhance the methane production (50.44-74.50) % as compared with the untreated wheat straw. Lignocellulosic biomass like wheat straw was considered having complex plant tissue structure. High lignin and hemicelluloses content present in the wheat straw make it very difficult for the microorganism to digest during anaerobic digestion and enzymatic hydrolysis. After the pretreatment, chemical composition of the wheat straw were determined and significant morphological changes in its structure were predominant. Lignin removal of (24.52- 42.04) % was recorded along with the (25.73-48.75) % hemicelluloses solubilization that favored its enhanced anaerobic digestibility. Pretreated wheat straw was co-digested with anaerobic waste activated sludge to increase the process stability performance. During the digestion period, the process parameter like volatile fatty acids, alcohol production, pH, CODs, percent VS and CODs removal were strongly monitored at each four days interval. Key words: AFEX pretreatment for WS, enhanced anaerobic digestibility, methane enhancement, lignin removal and hemicelluloses solubilization. 1. Introduction Energy production and its availability is becoming challenging day by day in the rural sector of the developing countries. Energy utilization measurement of the society determines its prosperity level. Whereby, the developing countries have the lowest average per capita energy consumption rate of 1 tons of oil equivalent (TOE) per year as compared with the energy per capita consumption rate of 4 tons of oil equivalent per year for the developed countries. Some of the developing countries like India, Nepal, Ghana and Kenya have the lowest energy consumption rate of 0.54 TOE /year, 0.34 TOE/year, 0.41 TOE /year and 0.47 TOE /year respectively which was about half of the average energy consumption per capita per year for the developing countries (IEA, 2010). Lignocellulosic biomasses are considered a promoting approach in the rural sectors to supply biogas to the community as well as the onsite organic fertilizer production. As the rural areas have abundant supply of agricultural residues and livestock manures, that’s why, the onsite biogas production from the lignocellulosic waste is most suitable option to treat all types of organic waste. China is considered as the largest agricultural producer as well as the largest biomass producer in the world and has an average production of 109 million metric tons of wheat straw annually (Yang et al., 2010). Anaerobic digestion is the well developed technology known from decades to treat the bulk quantity of agricultural wastes. The anaerobic treatment of the organic waste not only results in production of methane but it also reduced the risk of greenhouse emissions to a greater extent (Fu et al., 2014). It consisted of four stages: hydrolysis, acidogenesis, acetogenesis and methanogenesis with methane and carbon dioxide as the final product (Wang et al., 2012). In case of lignocellulosic biomasses, hydrolysis is considered as the rate determining step (Appels et al., 2008). The lignocellulosic biomasses were considered complex for anaerobic digestion process and mostly reluctance were reported to adopt them on industrial scale due to their high lignin contents. Different physical, chemical, thermochemical and biological pretreatment were cited in the literature with almost same objective of decreasing lignin contents and cellulosic crystallinity in the crop residues which can possibly enhance methane production and enzymatic conversion (Hassan et al., 2016a; Li et al., 2015). Hence, a novel pretreatment process