Anaerobic digestion or biodigestion, is a natural process by which bacteria -under the absense of oxygen- decompose organic waste to produce biogas and a mud with biofertilizer properties called digestate. The biogas generated has a high calorific value and can be used as a source of energy production, while the digestate generated is a sanitized sludge that can be used as a high-quality fertilizer or soil improver.
It is the treatment of biodegradable organic waste (vegetable, lignocellulosic waste, waste of animal origin, among others) in the absence of oxygen.
Product of this process is obtained biogas, which is a gas rich in methane (CH4) in a concentration of 30% to 50% in volume and traces of nitrogen (N2), hydrogen (H2), hydrogen sulfide (H2S), water vapor and ammonia (NH3), and other sulfur compounds may also exist.
The composition of the biogas is highly variable and will depend on multiple factors. Methane is the useful energy component in biogas, having a variable calorific value. In this way, it can be used as a replacement for different energy sources, for example, 1 m3 of biogas can replace approximately 0.58 liters of kerosene, 0.5 to 1.5 kg of firewood, 0.61 liters of gasoline and 0,74 kg of charcoal.
Depending on the climatic conditions, there may be various applications to take advantage of the biogas, such as, for example: cooking of food, lighting, fuel, refrigeration, heating and electricity generation. In comparison with domestic Liquefied Petroleum Gas (LPG), a 10 kg gas cylinder is equivalent to 20 m3 of biogas, due to LPG has a calorific value of 11,739 (kcal / kg), while that of biogas is of 6,000 (kcal / m3).