Design and operation of landfills for optimum stabilization and biogas production

Abstract

Most municipal landfills are constructed and operated with exposure to intermittent rainfall. Infiltration of rainfall, together with the inherent moisture content of landfilled wastes, promotes leachate production and accelerates rates of conversion of waste constituents. As these conversion processes proceed, waste stabilization occurs, leachate quality changes, and biogas is released in correspondence with the prevailing phase of stabilization. The intensities and temporal and spatial dimensions of these phases are waste-specific, a function of landfill design and operational strategy employed, and characterized by changes in physical, chemical and biological indicator parameters. Recognizing that most landfills exist as microbially mediated anaerobic waste conversion processes, with the sequential phases of acid formation and methane fermentation accounting for the majority of waste stabilization being accomplished, a fundamental understanding of these two principal phases of landfill stabilization is provided and used as a basis for developing guidance for controlled landfill design and operation. This guidance emphasizes optimization of stabilization efficiency, establishes cost-effective procedures for leachate management, and promotes regulated biogas production and utilization. To accommodate these objectives, the benefits of converting landfills into controlled bioreactor systems through regulated leachate generation, containment, collection, and in situ recirculation for accelerated waste stabilization and integrated biogas management are described, and opportunities for ultimate leachate disposal, biogas utilization and landfill reclamation are illustrated and compared to relative costs of other management options.