Gas emissions from landfills and their contributions to global warming

The contribution of methane from UK landfills is described in relation to total gas emissions to the atmosphere and how these have been shown to contribute to global warming. The known effects that methane has on the atmosphere are reviewed and the relationship to those effects caused by other greenhouse gases is described. A methodology utilized in assessing the quantity of landfill gas emitted from landfill sites is described, as are the main principles used in a gas generation model. Results of a survey, field trials and categorisation of the many types of site condition and waste mixtures are explainted, including the techniques incorporated into the model to allow a potential gas yield to be predicted. The factors that limit this potential yield of methane such as the oxidizing capacity of soil are identified and assessed. The potential effect of landfill-gas utilisation on the total emission and the economic viability of such schemes is reviewed in relation to reduced carbon dioxide and methane emissions. Combustion of landfill gas is shown to make a small net contribution to the potential equivalent CO2 reductions. The economics of energy recovery from landfill gas associated with CO2 reductions are shown to be significantly better than other alternative energy forms.