Environmental Engineering Reference
In-Depth Information
The main objective is to define suitable strategies that can allow proper material recovery and
energy production programs. The first step for the formalization of Decision Support Systems
for solid waste management is the choice of the decision variables. In the following, the
decision variables necessary for MSW are reported (for further details, see Fiorucci et al.
(2003)). After that, in the following sections, a discussion is reported concerning the
formalization of objectives and constraints for multi-objective decision models.
3.1. Introduction
The complexity of planning a Municipal Solid Waste (MSW) management system
depends on the necessity of taking simultaneously into account conflicting objectives. It is
really difficult for planners to develop a sustainable approach to waste management and to
integrate strategies aiming at producing the best practicable and environmentally sustainable
option. To formalize these strategies, in the last two decades, considerable research efforts
have been directed towards the development of optimization models for MSW flow
allocation. Several examples of mathematical programming models have been developed for
MSW management planning, such as, for example, in Chang and Chang [1998], Fiorucci et
al. [2003], Costi et al. [2003]. The necessity of taking into account economic, technical, and
normative aspects, paying particular attention to environmental problems (which usually
cannot be dealt with by economic quantifications only) is more and more felt. Such a reason
has led several authors to propose multi-criteria decision approaches.
The nature of the MSW management problem is a multi-criteria one, and should be
treated by a suitable technique, depending on the specific case study. Multi-criteria problems
(MCDM-Multi-Criteria Decision Making) are classified as follows (J. Malczewski, GIS and
Multicriteria Decision Analysis):
•
Multiobjective decision problems
•
Multi-attribute decision problems.
The attributes are proprieties of the entities of the real world; measurable quantity or
quality of a certain entity (decision objects). The objective is an indication regarding the
system state that wants to be achieved (it indicates the directions of improvements of the
attributes). Often the decisions are taken not by a single individual but from many decision
makers. When there are many decision makers or decision groups it is necessary to
distinguish between a team and a coalition. The first one has consistent preferences, while, for
the second, this may not be true. Besides, there might be two types of decisions: competitive
and independent. Decision problems can be referred or to easily predictable situations
(deterministic, certainty situation: all information are known and there is a deterministic
connection between decision and effect) or situations that are predictable in a very difficult
way (uncertainty decision problem). There are two causes of uncertainty for a decision
process: the validity of information, and future events that can affect the preference of
different alternatives. When uncertainty is related to information only for the decisional
situation, they are probabilistic or stochastic decision problems. They are fuzzy decision
problems when uncertainty is related to the description of the meaning of the events,
phenomena.
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