Landfilling – the most used waste management technology

Project summary

Abstract:

Landfilling is the most used waste management technology in most parts of the world and Ghana is not an exception. Usually, the landfilled waste have high organic composition. The organic content under anaerobic conditions in the landfill, produce landfill gas; predominantly methane and carbon dioxide. The methane in the LFG is a greenhouse gas that has a high potency of causing global warming; leading to climate change. In an attempt to reduce the effect of landfill methane in Ghana, the microbial oxidation of methane on landfills is studied and the possibility of implementing the technological biocover solutions in Ghana is analyzed focusing on the Ohwim landfill as a study site. The Ohwim landfill was screened for methane concentrations using the TVA-1000B FID and the biogas (IR) detector. Methane concentrations of above 1867 ppmv were reported for the hot spots on the landfill such as the vents and sloped edges. The landfill surface however showed low methane concentrations. The variation in concentrations on the landfill surface and at the edges could be as a result of blockage of vertical transport and or high horizontal transport velocity. It could also be as a result of the generation of a natural biocover on the surface. The methane generation the Ohwim landfill was estimated using the first order degradation model, LandGEM, to give 300Mg/yr and 800 Mg/yr for default k value of 0.05y-1 and estimated k value of 0.3y-1 respectively. From the methane generation for the default k value, a methane load of 35g/m2/day was estimated. Finally, the oxidation model, LandGEM was employed to simulate methane oxidation efficiencies using the methane load estimated from LandGEM. The load was assumed to be constant and uniformly distributed in a baseline biocover model of 0.2m thickness as well as a 1m thick conceptual model with varying Vmax values of 150, 300,500,700 and 1000 nmol/s/g. From the baseline biocover simulation, oxidation efficiencies of 12% and 22% were obtained for Vmax of 150 and 300 respectively. This oxidation efficiencies did not account for the methane flux through the vents and edges of the landfill. Taking into consideration these weak areas of the landfill, the conceptual model reported methane oxidation efficiencies of 32%, 52%, 68%, 77% and 85% for Vmax values of 150,300,500,700 and 1000 nmol/s/g. Relating Vmax to the organic matter content of the biocover and the capacity of methanotrophs in oxidizing methane, the trend could mean that with the right amount of organic rich material, under suitable conditions, the biocover technology could be implemented in Ghana.