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Current practice of landfill settlement modeling is predominantly empirical, thus most of the available techniques make no attempt to simulate the real mechanisms of waste settlement. Although a landfill is an interacting multiphase medium there is limited research on landfill gas generation and dissipation as an integral part of the landfill settlements. This research describes a model which couples settlements of a bioreactor landfill with the generation and dissipation of landfill gases. The major mechanisms of waste settlement were identified as mechanical compression and biodegradation-induced strain. Mechanical compression was modeled with the help of laboratory simulations. To model the biodegradation-induced settlements, it was assumed that waste degradation obeys the first order kinetic equation. The mass balance was used to link settlement with gas pressures. The mass balance of the landfill gas was used to link settlement with gas pressures and the Richard's equation was used to simulate the distribution of moisture. The proposed mathematical model was solved numerically to predict the settlements, and gas pressures in a bioreactor landfill using landfill geometry and waste properties. To test the mathematical formulations, a numerical exercise was performed using a hypothetical bioreactor landfill. The model predicted higher strains as expected. It was also found that the high gas pressure values made a higher contribution to the total settlement. The model was capable of predicting landfill density, and the density values predicted for 25 years matched with those reported in literature. [ABSTRACT FROM AUTHOR]

The sustainability concepts can be incorporated into the waste management practice to achieve 100% recycling and are able to fully implement in handling of solid waste in developing countries with low labor cost such as Egypt. These concepts can also be applied in land-filling the waste in developed nations, which can be called sustainable landfills. The sustainable landfill is a modification of a bioreactor landfill. The bioreactor landfills have become quite popular in USA as they are much economical to operate compared with traditional landfills. The modification of a bioreactor landfill will include enhanced biodegradation, mining, recycling, recovery and reuse waste materials. A leachate recirculation system would maintain optimum moisture content and accelerate biodegradation of waste. The biological activities in the bioreactor landfills would diminish after seven to ten years and gas production become insignificant. During that time, the next stage will be mining of the landfill for recovery and recycling of various products. Once all the waste is mined the landfill is ready to be used again and the above is repeated to avoid the creation of a new landfill. In the final stage, it is proposed that mined products such as cardboard containers for milk and juice boxes; and plastics can be converted into products or construction materials (El Hagger 2005). [ABSTRACT FROM AUTHOR]