In Sweden, large amounts of household waste have been land-filled and are now waiting for final covering. At the same time, more and more organic waste is incinerated, resulting in growing amounts of fly ash. International Wastenews, Waste Centre Denmark no. 1, 2005 reports that tests have been made with suspension of fly ash in water and in-jection in landfills with a view to stabilising the landfill body.

The hypothesis is that the CO2 generated in the decomposition of the landfilled waste reacts with the fly ash. This should result in a tempering process (carbonatisation) that should continuously sta-bilise the landfill. At the same time, the sulphate contents may also reduce methane generation. To test the hypothesis, pilot scale tests have been carried out in Södertälje, and laboratory scale tests have been carried out at the Technical University of Luleå.

The conclusion from the pilot test is that it is highly feasible to mix the ash with water to a pumpable suspension that can be injected without a risk of tempering in the pumps. More tests are planned with larger amounts of ash compared to this one in order to establish whether the stability is affected.

Source: RVF Utveckling 2004:16: "Injektering av flygaska i hushållsavfallde-poni" (Injection of fly ash in household waste landfills). The report, in Swedish, is available at Waste Centre Denmark