Geotechnical and Geoenvironmental Characteristics and Behaviour of Landfill Biocovers

Abstract

Landfill gas (LFG) which mainly consists of methane (CH4) and carbon dioxide (CO2); is produced by the biodegradation of organic waste in landfills. CH4 is a greenhouse gas with a global warming potential (GWP) 23 to 25 times that of CO2. Landfills are one of the significant sources of anthropogenic CH4 emissions and thereby urgent control of CH4 emissions from landfills is necessary. One of the most promising approaches for reducing the environmental impacts of landfill emissions is to passively vent LFG through a biological cover soil or biocover in order to oxidize CH4 into CO2 through a natural biological process. It is well known that stabilized compost and peat based materials have high porosity and water holding capacity (WHC), as well as appropriate nutrient levels, and therefore can be a suitable medium for CH4 oxidation. The geotechnical and geoenvironmental properties of biocovers are of prime importance for the design, construction and maintenance of any type of biocover. Moreover, the performance of biocovers is strongly influenced by the simultaneous evolution of thermal (T), hydraulic (H), mechanical (M), and chemo-biological (C-B) processes, and also interactions between them during the lifetime of a biocover. The geotechnical and geoenvironmental characteristics, evolution of the T, H, M, and C-B processes, and their interactions have been mainly ignored in previous studies, and thus minimally understood. Therefore, the objective of the present thesis is to address the aforementioned knowledge gaps. This research is categorized into two main parts. In the first part, the geotechnical properties of compost and peat based biocovers are evaluated in order to assess the feasibility of the application of compost and peat based materials as biocover material from a geotechnical viewpoint. In the second part, the simultaneous evolution of T, H, M, and C-B processes and their interactions in compost, compost-sand (with a mix ratio of 3:1 (w/w)), and peat biocovers are studied through laboratory column experiments. The derived results showed performance of the compost-sand biocover with a mix ratio of 3:1 is steadier over time and no significant decline in CH4 oxidation rate occurred during the period of operation.