A Review: Biodigesters and their use for the generation of clean energy

Abstract

Biogas is composed mostly of methane (CH4) and other type of gases, but its composition generally depends on the type of organic matter (biomass) used and the decomposition conditions inside the biodigester, being of great importance the methane gas, which is what gives biogas its fuel properties for use in industry.Depending on the presence of oxygen during this process inside the biodigester, this can be of 2 types: anaerobic and aerobic.A biodigester in its operation is very similar to the digestive system of an animal: organic matter enters, which is digested by bacteria, producing gases (biogas) and also producing a high value fertilizer (biofertilizer).The types of biodigesters most used in the agricultural industry are also called continuous, they are called like this because their feeding is constant, and they also use a daily production of biomass, the retention time of the waste in this biodigester is much less. For this reason, it can be said that the influent is equal to the effluent or digester discharge, and it is expected that for this reason the biogas production will be uniform over time. Normally these biodigesters have a large capacity, so it is necessary to use pumps to feed them and other equipment to provide heat and agitation.Biogas contains high concentrations of pollutants, they mainly are: Carbon Dioxide (CO2), Hydrogen Sulfide (H2S) and also traces of Siloxanes. This gas can be used directly for power generation, but the large amount of CO2 and H2S reduces its calorific power, but the purification makes it possible to diversify the use of biogas, using it to generate heat, electricity or as a fuel for vehicles.When the biogas in its chemical composition contains mostly CH4, it can be used in the generation of electrical energy in the following ways: using a Biogas/Otto engine, using microturbines or with fuel cells.