Microbiological Processes in Landfills

Large landfills in the Soviet Union cover more than 140 thousand hectares. The gas emission intensities are extremely disproportional over the surface of these landfills. According to our data the rates of streams of the biogas components vary from 0 till 20, 46, 1.2 and 0.75 (×10−4m3 × hour −1/m2) for CH4, CO2, H2, CO, respectively. The stable carbon isotope composition of methane and carbon dioxide in the biogas of deep landfills layers is typical for methanogenesis from organic wastes, but it depends on the concentration of organic substance in the landfill ground and on the age of these landfills. In the upper layer methane becomes heavier and carbon dioxide lighter due to the microbiological oxidation processes. The most intensive methanogenesis is usually observed in the upper part of the anaerobic zone where the organic substance concentration is relatively high. The methanogenic microflora is represented by mesophilic methanobacteria, species of Methanosarcina and Methanobacterium genera are prevalent forms. At the depth of 10-100 cm from the surface intensive oxidation of methane, hydrogen and carbon monoxide is observed. The number of gas oxidizing bacteria is up to 10 cells per gram of soil. 14 species of methane oxidizing bacteria, which belong to 5 genera were iden tified. Hydrogen oxidizing bacteria belong to Alcaligenes, Pseudomonas, Paracoccus, Mycobacteriun genera. Between them psychrotrophic forms were found. It has been shown that in small landfills methane, produced in anaerobic zone, can be oxidized completely in the upper ground layer. The biogas extraction from landfills is important not only as an additional fuel source, but as a means of preventing pollution of the Earth's atmosphere.