1 Solid waste and solid waste management: Due to urbanization and population explosion, solid waste management is a serious problem worldwide . Each urban resident generates 0.35-1.0 kg per day [Ramzan.et. al, 2010].Currently, the global generation of municipal solid waste is approximately two billion tons per year, which is expected to increase to 3 billion tons by 2025 [Shersingh et.al, 2014].There are several available conventional treatment methods for dealing 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 because of the leachate flow from the discharged waste.3.2 Anaerobic Digestion: Anaerobic digestion is the complex process in which the organic compounds are mineralized into biogas. It consists of four main steps known as hydrolysis, acidogenesis, acetogenesis and methanogenesis, which is processed with the help of different groups of microorganisms [Geregor et.al, 2010]. Basically, anaerobic digestion degrades organic material in the absence of oxygen with the presence of microorganisms 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 the lipid, protein and carbohydrate content which produces 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 the total methane production is acquired from the conversion of acetic acid or the fermentation of alcohols, while 3...... half of the paper...... gas.3.8 Hydraulic retention time [HRT] HRT is the time the incoming feed spends inside the digester before it exits. The hydraulic retention time is directly inversely proportional to the temperature, i.e. when the temperature increases, the HRT decreases and vice versa. Therefore, since a shorter retention time carries the risk of leaching of the active bacterial population from the reactor while, in case of a longer retention time, it requires a large digester volume which leads to higher capital costs. Since for solid waste substrates it is necessary to reduce the HRT for domestic systems. 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 cattle dung treatment can contribute to the improvement of organic matter by increasing hormone replacement therapy [Sanchez et al., 1992].