Landfills and their effect on the Environment.....Scarier than we thought ?

Handling garbage in urban areas had long become a hot issue in the recent past , due to the inadequate space available and the lack of systematic recycling processes. Landfills have been long considered one of the few effective methods to solve the garbage problem, and as the landfills are closing rapidly all around the congested areas of Sri Lanka, It's time we all pay attention to the frightening facts concerning landfills.

 

Ranasinghe, R.H.K, a research student of Department of Civil Engineering Research community , explores in depth about Effect of compaction and moisture content on gas transport and water retention in landfill cover soil ,taking Maharagama landfill as a case study.

Engineered landfills are a rarity and only a very few controlled sites are available.The usual procedure is to cover the waste with a good cover soil which minimises gas venting facilities.Maharagama dump site can be given as an example.

Hazardous gaseous and liquid landfill emissions are few of the major environmental problems connected to landfills.Since Gas venting facilities are prohibited, pressure inside the waste increases rapidly, compared to the atmosphere. Once the solid waste is covered with soil these gases are released to the atmosphere with high pressure, through the cover soil. Therefore studying the cover soil parameters are of paramount importance in evaluating and predicting its future gas emission. 

The Main objectives of the research study has been to study about the gas transport parameters of landfill cover soil and to understand effect of compaction and moisture content of the soil on the gas diffusivity (Dp/Do) and air permeability (ka). 

In this research, measurements were done in 100cm3 repacked soil samples at different compaction levels and methane concentration in the research area was measured and a methane concentration contour map was produced. It has been observed that the increase of dry density and reduction of water content in the cover soil increases the amount of soil air content and thereby increases the soil gas transport parameters. At the fully dry condition and the with the maximum soil air content , the gas diffusion is around 9% of the gas diffusion coefficient in free air. However, with dry conditions the changes of soil structure properties also affects the soil gas transport, especially for the soil air permeability. According to the methane concentration contour map the methane concentration has been observed to be quite similar  to the atmospheric methane concentration all around the ground area except at few hot spots.

The research findings provide valuable details about suitable landfill cover soil parameters and how environment hazards caused by improper wastage dumping can be minimised and avoided altogether, by using proper engineered techniques to manage waste.

However, although the research certifies Maharagama waste disposal site final cover soil to be  a very less gas exchangeable material ,it also reveals the fact that the landfill could cause high levels of methane emission in the future.  Due to the low gas exchange through cover soil due to its high capping capabilities , the green house gas (methane) production is further enhanced. Loose compacted points in the cover layers could act as vulnerable gas leakage points in future and formation of cracks around the ground area would also be possible with elapsed time.

It’s time we all become alert about the current waste management treatments in the country and consider recycling instead of composting waste matter in landfills.Biodegradable goods take much longer (up to 30 years for a newspaper) to decompose when buried in landfills, as the necessary amount of Oxygen is lacking. Also, next time you go shopping or buy groceries, try to purchase goods that are not heavily packaged. Every little gesture helps and contributes to a healthier planet and a greener life for all.

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