Gas permeability and retention study on Ämmässuo temporary landfill cover structures made with Municipal Solid Waste Incineration Bottom Ash

This thesis was focused on the gas permeability and retention study of the temporary landfill
test cover structures made with Municipal Solid Waste Incineration Bottom Ash (MSWI
BA). This study was done for Helsinki Region Environmental Services Authority to
incorporate MSWI BA in the impermeable layer of the landfill cover structure. Accordingly,
gas permeability studies were done in the Ämmässuo landfill on two different landfill test
cover structures made with MSWI BA. Literature review was done for acquiring the
knowledge on landfill cover construction, gas flow mechanism and the factors affecting the
gas emission through the landfill cover structures. Impermeable layer of one of the test
structures was made with 0-5mm MSWI BA and the other structures was made with 0-2mm
MSWI BA and 3% polymer modified sodium bentonite. There was a considerable
difference in the measured gas emission above the impermeable layer between these two
test structures. This research study also explored the factors affecting the gas emissions
through the impermeable layer of the landfill test structures. In addition to the gas
permeability study of the two different landfill test cover structures, an experimental study
was done on the MSWI BA-clay mixture to use it as an improved construction material for
the impermeable layer of the landfill cover structure.

The analysis on the gas measurements of the two test cover structures revealed that the test
structure which was made with MSWI BA (0-2mm) and 3% polymer modified sodium
bentonite was more effective in reducing the landfill gas emission than the other one.
Experimental study results on MSWI BA-clay mixtures exhibited that the requirements of
impermeable layer could not be completely satisfied with mixtures used for the tests.
Outcome of this thesis aided Ämmässuo landfill in constructing a new temporary test
landfill cover structure in autumn 2018.