Organic waste-amended soil as biocover for landfills-impact on greenhouse gas emissions/ Siti Suaidah binti Rahim.

Submitted in PHD fulfilment of the requirements for the degree of Doctor of Philosophy.

Abstract
Municipal solid waste decomposition in landfills generates harmful landfill gases, notably methane, as a byproduct. This study demonstrates the use of various organic waste materials as biocover to mitigate these emissions. Given the limited research on the geotechnical and geoenvironmental aspects of biocovers, this study seeks to address this gap by evaluating different mixtures of biocover materials. Organic waste materials, including rice husk, crushed coconut coir, and compost, are mixed with 5% aerobic wastewater sludge and natural clay to create biocovers and tested to assess their geotechnical and geoenvironmental characteristics. Results indicate that the biocover materials outperform traditional clay covers in terms of organic content, liquid limit, compaction, permeability, and resistance to desiccation cracking. The most promising biocovers, such as 75CR (crushed coconut coir: wastewater sludge: clay in a ratio of 70:5:25), exhibit superior impermeability and meet ideal criteria for landfill cover performance. Geoenvironmental studies utilised four 30 cm×30 cm×86.5 cm bioreactors with varied biocover mixtures, conducted in simulated landfill conditions at the Petroleum and Chemical Engineering department, Universiti Teknologi Brunei. The study shows that biocovers enriched with methanotrophic bacteria effectively reduce greenhouse gas emissions. Comparative analysis with control (NCS) samples reveals significant reductions in methane production and cumulative CO2 equivalents emissions, particularly with the 75CR biocover, with its lowest cumulative CH4 production (28.9% less than NCS) and lowest cumulative CO2e emissions (24.7% less than NCS). However, potential limitations, such as the lack of analysis on the presence and activity of methanotrophic bacteria within the biocover-soil mixtures, were identified. Future studies should explore microbial kinetics to better understand the microbial dynamics within these biocovers. In conclusion, this study underscores the potential of biocovers in gas control and waste containment, with 75CR emerging as a promising option for mitigating methane emissions in landfills.

Includes bibliographical references and index.