Approximate cost functions for solid waste treatment facilities.

Cost estimation is a basic requirement for planning municipal solid waste management systems. The variety of organizational, financial and management schemes and the continuously developing technological advancements render the economic analysis a complex task, made more complex by the scarcity of real cost data. The objectives of this paper were: (1) to explore the problems arising in getting cost estimates from scattered and limited published data; (2) to suggest a procedure for generating cost functions relating initial set-up cost and operating cost with facility size; and (3) to present such cost functions, relevant to European states, for selected types of solid waste treatment and disposal facilities. Regarding the problems of available scarce data, one needs to deal with cost figures which correspond to facilities with variations in size, technology, year of construction, working conditions, level of technological automation, environmental impacts, social acceptance, capacity utilization rate, composition of inflowing waste, waste management policies, degree of compliance with quality standards, etc. The paper addresses this issue and discusses the proper use of statistical analyses in such cases of fragmented data; moreover, it points out some usual misuses of statistics by analysts and the danger of getting erroneous results. The suggested process for generating cost functions acceptable to the decision-makers is pivoted around the question of acceptable approximation level. Finally, approximate cost curves are suggested for waste-to-energy facilities, landfilling facilities, anaerobic digestion facilities and composting facilities.

A knowledge acquisition process to analyse operational problems in solid waste management facilities.

The available expertise on managing and operating solid waste management (SWM) facilities varies among countries and among types of facilities. Few experts are willing to record their experience, while few researchers systematically investigate the chains of events that could trigger operational failures in a facility; expertise acquisition and dissemination, in SWM, is neither popular nor easy, despite the great need for it. This paper presents a knowledge acquisition process aimed at capturing, codifying and expanding reliable expertise and propagating it to non-experts. The knowledge engineer (KE), the person performing the acquisition, must identify the events (or causes) that could trigger a failure, determine whether a specific event could trigger more than one failure, and establish how various events are related among themselves and how they are linked to specific operational problems. The proposed process, which utilizes logic diagrams (fault trees) widely used in system safety and reliability analyses, was used for the analysis of 24 common landfill operational problems. The acquired knowledge led to the development of a web-based expert system (Landfill Operation Management Advisor, http://loma.civil.duth.gr), which estimates the occurrence possibility of operational problems, provides advice and suggests solutions.

Functional relationships of landfill and landraise capacity with design and operation parameters.

Solid waste management presses for effective landfill design and operation. While planning and operating a landfill (LF) or a landraise (LR), choices need to be made regarding: (1) LF-LR morphology (base shape, side slopes, final cover thickness, LR/LF height/depth); (2) cell geometry (height, length, slopes); and (3) operation parameters (waste density, working face length, cover thicknesses). These parameters affect LF/LR capacity, operation lifespan and construction/ operation costs. In this paper, relationships are generated between capacity (C, space available for waste) and the above parameters. Incorporating real data into simulation kgamma A1.38, runs, two types of functions are developed: first, C = where A is the LF/LR base area size and kgamma a base shape-dependent coefficient; and second, C = alpha(p,gamma,A) + delta(p,gamma,A)Xp for every parameter p, where Xp is the value of p and alpha(p,gamma,A) and delta(p,gamma,A) are parameter- and base (shape/size)-specific coefficients. Moreover, the relationship between LF depth and LR height that balances excavation volume with cover material, is identified. Another result is that, for a symmetrical combination of LF/LR, with base surface area shape between square and 1:2 orthogonal, and final density between 500 and 800 kg m(-3), waste quantity placed ranges from 1.76A1.38 to 2.55A1.38 tons. The significance of such functions is obvious, as they allow the analyst to investigate alternative LF/LR schemes and make trade-off analyses.