ABSTRACT

Municipal waste deposited in non-hazardous landfills usually contains about 50% of organic matter, which is generally susceptible to microbial degradation. Commonly applied waste compaction which aims at the reduction of their volume, as well as the use of barriers insulating the mass of waste from the environment favor the creation of anaerobic conditions. In such conditions, consortia of fermenting microorganisms are developing. They use organic compounds or intermediate products of their decomposition, contained in waste, as electron acceptors in the process of energy production. This group includes the microorganisms that produce methane. A large group are also sulfur bacteria, sulfate-reducing bacteria and bacteria leading to nitrogen transformations (ammonification and denitrification). As a result of these changes, gaseous products or water-soluble compounds are formed. Gases and volatile liquids easily migrate to the environment. According to the Article 2 of Council Directive 1999/31/EC on the landfill of waste “all the gases generated from the landfilled waste” are called “landfill gas”. This gas is produced mainly by microbiological processes. However, also abiotic processes such as chemical reactions between components of waste and physical phenomena, such as evaporation or sublimation, also have little influence on its composition; especially with regard to trace gases (EPA, 2008).