In anaerobic digestion and biomethanization, fermentation process in the absence of oxygen, biodegradable organic matter is decomposed by bacteria producing biogas (methane and carbon dioxide). Sources of organic matter are often dumpsites, purifiers, organic fraction of municipal waste, agro-industrial organic waste, or energy crops.
Due to the high energy power biogas has, it becomes an appreciated renewable fuel. Biomethane, biogas subjected to a cleaning and concentration (upgrading) treatment, has similar usage characteristics and possibilities to those from natural gas from fossils.
Moreover, the digestate (residual liquid matter) is generated in large volumes and has high humidity besides a considerable concentration of nitrogen and phosphorus. Therefore it is considered as a fertilizer of zero or low cost that can be applied directly or in “fractions”.
Energy recovery from microalgae helps reduce CO2 emissions from biomethanization even more, as it is used in the cultivation of microalgae.