Conventional sources of energy: Coal, petroleum, natural gas, fissionable materials like uranium.
Non-conventional sources of energy: Wind, Hydro Power, the Sun, Ocean-Tidal Energy, Interior of the Earth, Biogas, Plants, Vegetable waste etc.
Biomass: Slurry of animal dung or other types of bio-waste and water is made in the mixing tank and then fed into the digester. The digester is usually a closed underground tank. In digester, the action of micro-organisms decomposes the complex compounds of the biomass in the slurry. Anaerobic micro-organisms, the presence of water, degrade the biomass in the digester. As anaerobic micro-organisms do not require oxygen, the digester is designed like a sealed chamber. The complete degradation process takes few days, during which biogases are produced. Now the biogas can be supplied to consumers through pipes. Periodically the slurry that is left behind in the digester is removed and it serves as excellent manure.