Landfill gas is a complex mix of different gases created by the action of microorganisms within a landfill. Landfill gas is approximately 40% to 60% percent methane, with the remainder being mostly carbon dioxide. Trace amounts of other volatile organic compounds (VOCs) comprise the remainder (<1%). These trace gases include a large array of species, mainly simple hydrocarbons.
Methane % 45-70
Carbondioxide % 30-55
Nitrogen % 2-5
Oxygen % 0,1-1
Ammonia % 0,1-1
Sulphur % 0-1
Water Vapor % 1-3
The characteristic feature of this phase is the presence of O2 from the atmosphere at the time the waste is stored. Aerobic bacteria survive until oxygen is depleted. The product of this phase is carbon dioxide and water vapor.
Duration can be expressed in several weeks or hours.
With the start of the formation of organic acids from the compounds produced in the aerobic phase, more significant amounts of CO2 are produced. The anaerobic decomposition phase begins. The storage area is highly acidic in this phase. Acids dissolve nutrients with moisture.
Duration 1 to 6 months.
Some of the anaerobic bacteria consume organic acids in this phase. The storage area becomes more neutral thus methane-producing bacteria begin to form themselves. CO2 and N2 amounts are reduced while H2 is completely exhausted.
Duration 3 months to 3 years.
Decomposition begins when LFG production becomes stable. In this phase, LFG contains
45% - 60% CH4
2-9% other gases
This production can last 20 years.
Duration 1 year to 40 years.
The typical LFG collection system consists of the following three main components.
In addition, many LFGs are equipped with a Flare unit for use in the combustion of excess gas or downtime in energy recovery plants
Average channel depth 4 m
Maximum channel depth 10 m
Average channel length 120 m
Maximum well depth -45 m
Diameter of well impact -50 m