Gaspotentialen i en deponi, idag och i en framtid

Abstract: Deposited waste material degrades within a short period in anaerobic environments. The methane gas that is formed provides a harmful contribute to the greenhouse effect, 23 times larger impact than carbon dioxide. It is therefore desirable to minimize the emissions of methane gas from landfills. This may be achieved by drain the landfill of gas. In this thesis the amount of produced methane gas at the landfill at Örebro has been calculated. Estimations have also been made of the amount of methane gas that might be produced in the landfill in the future. The investigation was performed with a model from the Intergovernmental Panel on Climate Change (IPCC). The fraction of extracted gas until year 2007 has been about 30-40 volume-percent of produced methane gas. The amount of gas extracted at present may only be possible to obtain until the year of 2008. After that, the efficiency of the gas extraction system is exceeded. The production of methane gas in the landfill of Örebro has probably already reached the point of culmination and will thereby decrease within the years to come. At present, about 15 000 MWh is extracted every year at the landfill in Örebro. A potential gas extraction in 20 years is assumed to be about 1-4 GWh. The methane gas that emit to the atmosphere is assumed to be about 50-60 volume-percent of the produced methane. The extraction of methane gas may be profitable about 30-50 years further. A judgment whether a geological barrier exists under the landfill of Atleverket is under process at the Court of Environment. If the court decides that the geological barrier is insufficient the landfill has to be closed and covered with an impermeable top layer. A final top layer decreases the possibility to maintain an efficient gas extraction system; therefore the efficiency of the system may decrease to 20 volume-percent within some decades. The methane gas emissions will probably decrease with a final top layer since a more favourable climate methane oxidation will be created at the surface of the landfill.