Generation of greenhouse effect gases by different landfill types and methane gas control

Methane gas generated from waste landfill sites has been becoming public concern in respect with global warming. In Japan, a semi-aerobic landfill type is widely adopted as a typical landfill type. The amount of methane gas (CH4) from semi-aerobic landfill type was less than that from conventional landfill type (anaerobic landfill type), although the amount ol carbon dioxide (CO2) from semi-aerobic landfill type was more than that from anaerobic one (Hanashima, 1985; Matsufuji, 1993). These facts can be ascribed to enlargement of aerobic zone within landfill layer of semi-aerobic landfill type. However, the relative heat absorption of CH4 is about 30 times that of CO2 (Minami, 1991). These results indicate that the amount of greenhouse effect gases from landfill sites might depend on landfill type. This paper is aiming at estimating the amount of greenhouse effect gases by different landfill types and proposing countermeasures for their reduction. The main results obtained are as follows: 1) Prediction model formulas of the amount of gases generated from each landfill type can be expressed by the regression curve of cumulative gasification rate, related to easily degradable organic matters; 2) Based on the formulas, the amount of greenhouse effect gases generated from landfill sites in Japa is 206,800t-C/year of CO2 and 35,700t-C/year of CH4 at the beginning of 21st century, respectively; 3) The influence on grobal warming by greenhouse effect gases generated from the conventional (anaerobic) landfill sites is estimated to be 5 times in Malaysia as much as that in Japan, 7 times in the Philippines, 12 times in Korea and Thailand, 38 times in Indonesia, 250 times in China, respectively; 4) The conversion of landfill type to semi-aerobic from anaerobic can reduce the effect by approximately 45 percent.