استفاده از تحلیل سناریوی مبتنی بر TOPSIS فازی برای ارتقا طراحی و پیش بینی ضایعات جامد شهری: مورد مطالعاتی در مجمع الجزایر قناری Using a fuzzy TOPSIS-based scenario analysis to improve municipal solid waste planning and forecasting: A case study of Canary archipelago (1999-2030)

1. Introduction An increase in the population, rapid urbanisation and a rise in community living standards have significantly accelerated municipal solid waste (MSW) generation (Song et al., 2015), and so a sustainable and efficient waste management strategy is needed to balance the need for development, the quality of human life and the environment (Tan et al., 2014). The management of this growing and complex problem requires approaches that deliver more consistent and robust results for decision-making. This study has two objectives: 1. To select the best MSW treatment methods to be applied for the amount of waste generated in a specific territory. It should be based on the interests and wishes of the main local stakeholders, mainly citizens and their political representatives, academic experts and environmental decision-makers. 2. To estimate and forecast the evolution of the MSW generation under different assumptions and scenarios for a future period, using a mathematical model developed on the basis of the historical official data for a given territory such as the Canaries was applied. This help to disentangle how the different factors affect MSW generation and to determine when the current landfill capacity would be overcome in that territory. To achieve those objectives, a decision model based on Delphi, fuzzy TOPSIS, system dynamics (SD) and scenario analysis that supports decision-making for the comparison of different potential alternative MSW treatments was developed. Changes and incentives in public policies and consumption habits may increase the uncertainty and variability of the forecasts regarding the future amount of different waste fractions. Some of the relationships between those factors are dynamic, so the feedback mechanism may provoke non intuitive responses. Many longterm decision-making processes are dynamic, and critical decisions often require multiple and interrelated decision within extremely uncertain and complex scenarios. Therefore, scenarios analysis is a strategic planning method that can help decision makers make more flexible long-term planning (Salmeron et al., 2012). The Canary Islands are an interesting case study because they are among the most important tourist islands in the European Union (EU). The tourist industry contribution to the total gross domestic product (GDP) of Spain reaches 31.4% and the population working in this industry reaches 33.1%, and to improve the MSW management is a key issue for the sustainable tourism development of that territory. In the study area, the topic of MSW management planning has been investigated very little, e.g. Garcia-Falcon and Medina-Munoz ~ (1999) studied the sustainable tourism development in the main island of the Canary archipelago and Santamarta et al. (2014) identified some weaknesses of the MSW Canary management system for the period 2005e2011 and proposed recommendations to improve it but without neither calculations nor modelling. This paper helps by responding to this gap in the Canaries and the tourist islands, because, this study area which can be considered as a closed system and it was nominated as biosphere reserve by UNESCO, no research has been conducted to determine the key factors that directly affect the generation of waste and the impact they may have in the long term. As well no mathematical models or fuzzy or hybrid approaches have been applied as prospective aid to improve solid waste planning. At the same time, this case study is very useful to study the influence of the variations of the tourism on the MSW generation in touristic island, where the contribution of the tourist industry to the GDP is very high (e.g. 31.9% in Canary island in 2015). The main contribution of this paper is the development of a prognostic tool to improve the consistency of decision-making and the forecasts of the future MSW generation in any territory. It is needed because this European territory has to comply with what was established by the European Directive 2008/98/EC, where the countries have to develop waste prevention plans and programmes (articles 28 and 29).