Comparative analysis of the variability of the concentration and vertical profile of methane emission from dumpsites and rice plantations using a bespoke low-cost unit in Ile-Ife, Nigeria

Compared to carbon dioxide (CO2), methane (CH4) is a more potent greenhouse gas, trapping more heat than CO2 ¬on a per molecule basis. With increasing levels of activities in prominent sources of methane such as livestock farming, rice farming and waste management, especially in developing economies like Nigeria, the need for a comprehensive and reliable CH4 inventory cannot be over-emphasized. Using a bespoke low-cost measuring unit, this study investigated the vertical profile and variability of methane around rice farms and waste dumpsites. Findings shows that ambient levels of methane around the rice farms ranged between 26 ppm and 698 ppm and were highest at temperatures >30°C while lower concentrations were measured at lower temperatures. High methane concentrations were observed at a height of around 15 m and gradually decreased with increasing altitude. For waste dumpsites, methane levels measured around the waste dumpsites ranged between 45 ppm and 1220 ppm aligning with variation in the amount of waste. These higher concentrations are however often found at low altitudes below 20 m over both dump sites. At temperatures above 30°C, methane concentrations are found at its highest across both dumpsites. This study concluded that the bespoke measuring unit performed relatively well, and air temperature has a positive influence on methane concentration at all study sites. Also, while waste dumpsites seem to emit more methane than rice farm, all study sites emit appreciable amounts of methane which could accumulate and contribute significantly to regional climatic variations and enhance levels of tropospheric ozone.