CHARACTERIZATION OF ILLEGAL DUMPSITE WASTES AND THEIR GREENHOUSE GAS EMISSIONS IN IBADAN SOUTHWEST LOCAL GOVERNMENT AREA, OYO STATE, NIGERIA

Abstract

Most cities in Nigeria are notable for their unauthorised dumpsites which are one of the significant contributors to Greenhouse Gas Emissions (GHGE). These Greenhouse Gases (GHG) are known to cause climate change effects such as floods, proliferation of disease vectors, spread of infectious diseases and increased heat-related mortality. Information on the contribution of these illegal dumpsites to GHGE is inadequate in developing countries. Therefore, this study was designed to characterise wastes and assess their GHGE particularly carbon-dioxide (CO₂) and methane (CH₄) from illegal dumpsites in Ibadan Southwest Local Government Area (IBSWLGA), Oyo-state. Thirty dumpsites were identified by snowballing with 15, 10 and 5 dumpsites in the high-, medium- and low-density areas of IBSWLGA respectively. Three dumpsites in each of the areas were selected using simple random sampling technique. A composite fraction of the wastes from each site was collected and characterised into physical components such as plastics, nylon, metals, paper and other wastes using the American Society for Testing and Materials Standard. The percentage weight of the wastes was determined. A CO₂ meter was used to measure the concentration of CO₂ emissions (ppm) at the dumpsites thrice weekly at specific periods of the day (8-10am, 12-2pm and 4-6pm), for 12 consecutive weeks. The values of CO₂ were compared with the United States Environmental Protection Agency (USEPA) limit (300-450ppm). The 2006 Intergovernmental Panel on Climate Change waste model was used to estimate the CH₄ emitted from each dumpsite per year using the weight of the wastes and population of the areas. Descriptive statistics and ANOVA were used for data analysis. Composition of characterised wastes for the high-, medium. and low-density areas were: 21.7%, 35.2% and 50.0% for organics; 8.3%, 10.2% and 3.3% for plastics; 51.3%, 31.1% and 25.0% for nylon; 8.0%, 5.6% and 5.0% for metals; 5.3%, 10.6% and 13.3% for paper and 5.3%, 7.0% and 3.3% for other wastes respectively. The overall mean CO₂ emission in the high-, medium- and low-density areas were: 372.5±92.1pm, 385.6±114.5ppm and 380.8±82.4ppm respectively. Mean CO₂ emissions at different periods of measurement for the three areas were: 420.1±98.5ppm, 433.5±148.3ppm and 417.5±71.4ppm at 8.10am; 375.4±83.6ppm, 391.3±89.9ppm and 387.6±86.4ppm at 12-2pm and 321.9±65.4ppm, 331.9±68.1ppm and 337.3±69.4ppm at 4.6pm respectively (p<0.05). The highest (1157ppm) CO₂ emission was recorded at the medium-density area between 8-10am. The percentage composition of methane gas in the total potential gas emissions from the dumpsites in the high-, medium- and low-density areas was; 0.000158 Gg/yr., 0.000026 Gg/yr and 0.000012 Gg/yr. respectively. Levels of carbon-dioxide from illegal dumpsites were within acceptable limits, while methane emission quite small. Evacuation of wastes from illegal dumpsites to authorised locations for recovery of greenhouse gases and material recycling should be promoted.