In current landfill practice, the site operator first installs a lining to seal the base of the landfill. Waste is then tipped into the landfill over a period of many years. When it is full the site is capped with an impermeable cover. The waste is then fully enclosed and sealed from the environment. It remains in place in the state in which it was landfilled. The disadvantage of this system is that these landfill sites have to be perpetually maintained and monitored, and all the safety measures put in place must continue to work properly. Also, the impermeable cover must be periodically replaced, which is a major operation because everything that has been placed on top of the landfill first has to be removed. This makes it difficult to restore sites for new uses. Moreover, such sites remain a burden and a source of uncertainty for future generations.
Sustainable landfill practice
Sustainable landfill practice makes use of natural processes. When different types of wastes come into contact they may react with each other, water being an important medium for setting such reactions in motion or for stopping them. The type of wastes and the proportions in which they are mixed also make a difference. These differences can be used to speed up the rate of biological degradation, control leaching and immobilise contaminants.
Sustainable landfill delivers better results than current landfill practices. The critical processes within the landfill are known and emissions remain within the required limits. Sustainable landfill techniques can be used for almost every type of waste, but the right mix of wastes is essential for getting the best results. Crucially, sustainable landfills do not need an impermeable cover to prevent water coming into contact with the waste; an equilibrium is reached between the materials in the landfill and the surrounding environment.
Research by the Sustainable Landfill Foundation, completed in 2006, demonstrated that sustainable landfilling is a realistic and feasible technique for future landfill sites. Follow-up research (2006–2010) has shown that the technique can also be used in a modified form on existing landfill sites.