Firstly, livestock resources in Iran were analyzed and amounts of animal manure produced in each province were estimated using different methods. Secondly, calculations were made using volume of biogas produced and fractions of methane gas from computed livestock resources. According to annual volumes of natural gas consumption and calculated volumes of biogas production from livestock waste in each province, evaluations were made for the portion of natural gas consumption that could potentially be replaced by biogas from livestock waste.
Application and utilization of biogas in Iran has a long history. Sheikh Bahai (1530–1622) was the first to use biogas in a bathhouse in Esfahan. In recent years, the first biogas production digester was built in 1975, Niazabad village, Lorestan western Iran. This digester has a volume of 5 m3 that used the livestock waste of the village to produce biogas for providing hot water for bath [1]. The livestock waste resources are under the attention of industrialized countries to produce biogas. The produced biogas can be used as an energy carrier after performing some refinement processes matching with global and environmental standards such as ISO: TC 255. Using biogas in industry can make a big saving in consumption of valuable fossil resources (Oil and Natural gas) [2].
This gas can be directly applied to a wide range of industries and existing heating systems, which can save natural gas and oil consumption as an exportable and valuable fossil fuel resource which reduces the environmental air pollutions. In most countries, general use of this gas is for cooking and lighting [3]. There are different types of reactors for the production of biogas and two types are most commonly used in Iran, Chinese and Indian models without any major modification in structures and digestion method. Comparisons of these two conventional biogas reactors are presented in Table 2[4] and also shown in Fig. 1.