Waste Characterization

To ensure stability of a construction, the physical properties of its components have to be known so that relevant analysis and design can be carried out. In a landfill, waste presents the largest structural element and influences stability and integrity of the lining system (Jones and Dixon, 2003) and operation of leachate and gas extraction systems. However, in spite of this critical role there is still a dearth of knowledge on behaviour of municipal solid waste (MSW) as an engineering material. To aid development of methodologies for measuring and reporting mechanical properties of waste materials, and to formalise analysis and design procedures, a universally accepted waste characterization framework is required. Waste characterization must provide sufficient information to enable designers and operators of waste containment facilities to appreciate the type and engineering properties of the waste mass and hence to anticipate likely behaviour and potential problems. A waste characterization framework should have two elements, a classification system for waste components, and description of the structure/fabric of the waste mass. Classification of components can be related to material characteristics and parameters. Description of waste body structure can be related to mass characteristics and state parameters. Knowledge of both is required to understand mechanical behaviour of waste bodies (e.g. compressibility, shear strength and hydraulic properties), to group wastes with similar mechanical properties and to facilitate the exchange and interpretation of measured properties by both researchers and practitioners. Although there are several waste classification systems in current use world-wide, none of these relate specifically to mechanical behaviour. Therefore, there is a need to both develop a waste characterization framework and to disseminate it to encourage use world-wide. This section summarises the state-of-the-art of waste characterization as reported at the Waste Mechanics Workshop, New Orleans, March 2008, and outlines a framework that was presented and discussed. Application of a component classification is demonstrated using data from the literature. The workshop defined the uses of a waste characterization procedure, it identified the key factors that should be included in a characterization system, and considered the methods that should be used to obtain measurements and the best approach to present characterization information. Consensus was achieved on the form of the characterization framework and it was agreed that it should be disseminated to those actively involved in waste mechanics research and practice, with the aim of promoting it's use and to stimulate further development.