Abstract:
Carbon dioxide and certain other trace gases, including methane (CH4), nitrous oxide
(N2O) chlorofluorocarbons (CFCs), and tropospheric ozone (O3), are accumulating in
the atmosphere as a result of human activities. Global warming occurs because these
gases retain infrared radiation, which normally would dissipate into space from Earth
in the atmosphere, thus the atmosphere warms up. Some of the heat from the
atmosphere is transferred to the oceans and raises their temperature as well. As the
atmosphere and oceans warm, the overall temperature of the Earth rises. Because
carbon dioxide and other gases trap the sun’s radiation in much the same way as the
glass does in a greenhouse. Global warming produced in this manner is known as the
greenhouse effect.
This study will be used to develop plans for rehabilitating and mining of dumpsites in
the Colombo District. Most of the disposal sites were small scale and suffered by
operation problems such as the lack of man power and heavy machines and from the
environmental impacts such as ground water contamination and odor problem.
The methane emissions have been determined by the Intergovemmental Panel on
Climate Change (IPCC) using a method on the basis of mass balance approach
incorporates no time factor and can be applied to the total waste emanating from the
area. The calculation based on the amount of waste generation and open dumpsites,
the fraction of Degradable Organic Carbon (DOC) that actually degraded into biogas
and the fraction of biogas that actually released as methane.
Therefore, secondary data and information were gathered on disposal of wastes in the
Colombo District and three dumpsites, namely at Buthgamuwa, Karadiyana and
Maharagama were monitored for a period of seven days and a closed flux chamber
method was used to determine the rate of gas emissions and the composition of the
gas was analyzed.
As expected the new dumpsite generated higher rate of Landfill Gases (LFG) than the
old ones. Thus, an average gas generation was obtairied for the three sites and when
compared with the reported value was much higher than IPCC method for Sri Lanka.
The experimental value may be an over estimation and verification is needed and
further studies are recommended. Interestingly considerable oxidation of methane
takes place, perhaps in the cover soil. However, this oxidation is limited when
methane generation levels exceed threshold levels. Also depending on the partial
pressures, only moisture is given out while curtailing gas emissions. AlI of these
aspects needs in depth studies.
