Municipal waste and mixed waste landfills
The Swiss contaminated sites symposium in September 2023 in Solothurn was very well attended (https://www.bafu.admin.ch/bafu/de/home/themen/altlasten/fachinformationen/symposium-altlasten-schweiz.html). The main topic of the symposium was dealing with old municipal waste and mixed waste landfills.
Example picture; landfill «Hinterm Chestel» 4253 Liesberg, © KELSAG, 2023
In Switzerland, a ban on dumping untreated garbage or municipal waste came into force in 1996 and has been fully implemented since 2001; – All municipal waste in Switzerland is sent to the waste incineration plants (WIP) and used for heat energy production. All landfills are also listed as disposal sites (i.e. contaminated sites containing waste materials) in the cantonal ‘Registry for Contaminated Sites’ (RCS). Closed landfills are subject to an aftercare that guarantees the safety of these landfill sites for people and the environment. Finally, the aftercare must be able to demonstrate by means of a risk analysis that the disposal site can ultimately be left to its own. From that point onwards (final phase) only passive measures to secure the site contaminated with waste materials are permitted.
In Switzerland, only treated waste (inert and residual materials as well as slags) can be disposed of in landfills in a controlled manner, although it is becoming increasingly difficult to create new landfill space. Usable space in Switzerland is a scarce commodity and the economical, sustainable use of our land is a high priority. A safe interim use or reutilization of old landfill sites would therefore be desirable. However, certain reutilizations are unlikely to be feasible, as interventions in the subsoil could immediately trigger remedial actions with exorbitant costs. For example, solutions are conceivable that enable natural areas on landfill surfaces for the augmenting biodiversity and/or to produce renewable energy. In the distant future, landfill sites may also serve as material storage for secondary resources, which could be recovered and reintroduced into the economic cycle as raw materials.
How can the profitability of such solutions be increased? In the case of municipal waste landfills with a significantly high proportion of organic waste, for example, active aerobization of the landfill body with atmospheric oxygen is an interesting technique for obtaining biogas from the induced degradation of organic waste. Thinking one step further, hydrogen could be produced with the help of installed photovoltaic power on the surface of the landfill (see example picture) and - together with the harvested biogas and CO2 obtained from the air - synthesized into renewable liquid fuel (keyword SAF). Such solutions could pay off, but only if framework conditions are created for market-based environmental instruments, such as the Swiss CO2 law introduced for reducing CO2 emissions.