1 Solid waste and solid waste management: Due to urbanization and population explosion, solid waste management is a serious problem in the whole world. Each city dweller generates 0.35 to 1.0 kg per day [Ramzan.et. al, 2010].At present, the global production of municipal solid waste is approximately two billion tonnes per year, and is expected to reach 3 billion tonnes by 2025 [Shersingh et.al, 2014]. There are several conventional treatment methods to deal with solid waste, such as incineration, landfilling, composting and gasification [Shersingh et.al, 2014, Geregor et.al, 2010]. But these methods are associated with several problems such as air pollution, water pollution and fresh water contamination due to leachate from dumped waste.3.2 Anaerobic Digestion: Anaerobic digestion is the complex process in which organic compounds are mineralized into biogas. It involves four main stages known as hydrolysis, acidogenesis, acetogenesis and methanogenesis, which are treated using different groups. of microorganism [Geregor et.al, 2010]. Basically, anaerobic digestion degrades organic matter in the absence of oxygen with the presence of microorganism to form biogas [Shersingh et.al, 2014]. Microorganisms are classified into two communities: acidogenic bacteria and methanogenic archaea [Jia line et.al, 2012]. Acidogenic bacteria hydrolyze lipid, protein and carbohydrate content to produce simple sugar, amino acids, fatty acids and water. Finally, methanogenic bacteria will use acetate, methanol, hydrogen and CO2 and produce methane [Geregor et.al, 2010]. About 70% of total methane production comes from acetic acid conversion or fermentation of alcohols, while 3...... middle of paper ...... gas.3.8 Retention time hydraulic [HRT]HRT is the time spent by the food entering inside the digester before its exit. Hydraulic retention time is directly inversely proportional to temperature, i.e. as temperature increases, HRT decreases and vice versa. Therefore, as a shorter residence time carries a risk of eliminating the active bacterial population from the reactor, while a longer residence time requires a larger volume of digester, resulting in a higher investment cost. pupil. Since, for solid waste substrates, it is necessary to reduce the THS for domestic plants. It is easy to carry out methanogenic fermentation at low HRT at mesophilic and thermophilic temperatures [Zennaki et al., 1996]. However, many researchers have found that treating cattle feces can help improve organic matter by increasing HRT [Sanchez et al.., 1992].