Francisco Contreras

The University of Tokyo, Tokyo, Tokyo-to, Japan

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Publications (3)1.1 Total impact

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    ABSTRACT: The recycling of anthropogenic nutrients derived from the wastewater management systems is often characterized by a complex and uncertain scenario, due not only to the nature of the process but also to the involvement of different stakeholder groups. Over the past 10 years in Switzerland, policies regarding the use of sewage sludge as fertilizer have gradually shifted to a ban on use in agriculture. As a result, alternative methods for the recycling of anthropogenic nutrients may play a relevant role in the near future. This paper uses the analytic hierarchy process (AHP) to examine more closely the nutrient-recycling dilemma by analysing the preferences of a group of German-speaking residents in the city of Zurich for various management scenarios. Nutrient recycling by the use of urine separation toilets and the BioCon treatment process are presented as possible management alternatives in addition to current practice. The study shows that AHP can incorporate the respondents' preferences and multiple objectives when evaluating alternatives with different attributes.
    Water Science & Technology 01/2013; 68(12):2645-53. · 1.10 Impact Factor
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    ABSTRACT: Despite some progress, municipal solid waste (MSW) still poses pressure on cities and remains one of the major challenges in environmental management. There is no single solution to the problem since the drivers behind MSW systems may vary significantly from city to city. In this context, the development of a common strategy to attain a sustainable management has been increasingly difficult. This paper presents an issue-driven analytical framework to evaluate the past, present and future MSW management strategy for the cities of Yokohama and Boston considering four driver categories while evaluating if the relevance of these drivers has changed over time. These categories represent: (i) legal drivers (e.g. laws and regulations); (ii) technology development and institutional drivers (e.g. available technologies); (iii) regional and international drivers (e.g. solid waste flow as recyclable resources); and (iv) socio-economic drivers (e.g. population trends and public awareness). The analysis indicated that solid waste management capacity for both cases was under stress due to different reasons. In the case of Boston, the moratorium for disposal facilities played an important role while increasing population was a key driver for the city of Yokohama. The future management scenario suggests that various waste-to-energy alternatives and strong solid waste reduction policies will play a key role for Boston. In Yokohama, a shift on waste composition and generation triggered by a demographic change may open the path for new technologies while also considering the international demand of solid waste as a recyclable resource.
    Waste management & research : the journal of the International Solid Wastes and Public Cleansing Association, ISWA. 11/2009; 28(1):76-93.
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    ABSTRACT: This paper presents analytical hierarchical process (AHP) in combination with life cycle assessment (LCA) as a decision support tool for municipal solid waste (MSW) management. A proposed set of treatment plans and an array of impacts create a complex decision environment for MSW management in the city of Boston. AHP is utilized to incorporate the relative importance of the different impact categories and treatment plans into the decision scheme regarding stakeholder group's preferences. The use of biogasification and refuse derived fuel (RDF) technologies into different management plans is presented as an alternative to the actual management of household solid waste. The results of the AHP application show that between the impact categories presented, green house gas emissions and landfill capacity constrains are ranked higher rather than the cost associated to the operation of the plan and health damage associated to the treatment plans presented among the stakeholder groups. In a broader context, the use of a hierarchical approach on AHP to structure the decision problem allows the development of four different scenarios according to the contribution of each stakeholder group to the decision scheme. In this analysis, the use of biogasification was considered as the most suitable plan to follow.
    Resources, Conservation and Recycling. 01/2008;