Biogas is a form of clean cooking mechanism, an eco-friendly sustainable source of renewable energy, economically and environmentally compatible to use. It is produced out of organic waste and can be used for multiple purposes i.e. thermal, electric etc. The slurry that the biogas system produces is a convenient source of organic fertilizer which is a key factor on multiplying the agro-productions maintaining the environmental sustainability. The Biogas technology has a key role on generating green jobs in a large numbers (at around 13000) in Nepal. Most of the villages (more than 2800, out of the total: 3915) of all 75 districts of Nepal have biogas installed. Studies have shown that, along with the biogas installation, the situation of health and sanitation is being gradually enhanced; deforestation (for the cause of firewood) is being curbed in Nepal. The technology is being concerned on caste and ethnicity, gender etc. issues to make the sector more inclusive, participative, decentralized and balanced.
Waste to Energy (W2E) as a form of biogas system is an large energy project newly adopted in Nepal. This system is based on the large amount of organic waste produced out of private as well as public organizations, business complexes etc. Primarily, this project is affixed with an aim of other thermal usage of biogas and electrification.
Biogas is produced by anaerobic digestion or fermentation or decomposition of organic wastes by the action of methanogenic bacteria. It is composed of 50-70% methane, 30-45% carbon dioxide, 1% H2S, 0.1%N2, 0.1% O2, 0.1% H2 and some other gases. During digestion about 25-30 % of the dry matter of waste is converted into a combustible gas and residue of 70-75 % of the total solids content comes out as sludge which is known as slurry. The energy content of biogas is 6-6.5 KWh/m3, and the ignition temperature is 650-750 o C.
This energy allows biogas to be used as a fuel for any heating purpose, such as cooking. It can also be used in a gas engine to convert the energy in the gas into electricity. Biogas can be compressed, much like natural gas and used to power motor vehicles. This gas is about 20 percent lighter than the air which is odorless and burns with clear blue flame similar to that of Liquefied Petroleum Gas (LPG).