Optimización del ciclo de vida para el diseño sostenible de sistemas circulares de gestión de residuos municipales
- Autores: Selene Cobo Gutiérrez
- Directores de la Tesis: Ángel Irabien Gulías (dir. tes.), Antonio Domínguez Ramos (codir. tes.)
- Lectura: En la Universidad de Cantabria ( España ) en 2019
- Idioma: español
- Títulos paralelos:
- A life cycle optimization framework for the sustainable design of circular municipal solid waste management systems
- Tribunal Calificador de la Tesis: Inmaculada Ortiz Uribe (presid.), Laureano Jiménez Esteller (secret.), Gonzalo Guillén Gosálbez (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería Química, de la Energía y de Procesos por la Universidad de Cantabria
- Materias:
- Enlaces
- Resumen
- español
Los objetivos de esta tesis son desarrollar un marco metodológico para determinar la configuración óptima de los sistemas integrados de gestión de residuos bajo una perspectiva del ciclo de vida, e investigar si la economía circular contribuye a la reducción del consumo de recursos y los impactos ambientales y al crecimiento económico.
El marco metodológico propuesto se aplicó a la gestión de residuos municipales orgánicos en la Comunidad Autónoma de Cantabria. El modelo del sistema se construyó combinando análisis de flujo de materiales y análisis de ciclo de vida (ambiental y económico). Se formuló un problema de optimización multi-objetivo para maximizar la circularidad de los nutrientes y minimizar el uso de recursos, los impactos ambientales y los costes de gestión de residuos.
Los resultados sugieren que mejorar la circularidad de los recursos no implica necesariamente una reducción de costes, del consumo de recursos o de la emisión de cargas ambientales.
- English
The concept of the circular economy arose in response to the pollution and the depletion of natural resources related to our production and consumption model. In the context of a circular economy, waste is viewed as a resource that must be upgraded before being reintroduced back into the production cycles, thereby minimizing resource extraction and waste disposal. As a consequence of the European policies that prioritize waste valorization over disposal, the average fraction of municipal solid waste disposed of in landfills within the European Union has steadily decreased in recent years, as the incineration, recycling and composting rates have risen. Nonetheless, these statistics vary widely among Member States; only 30% of the municipal solid waste generated in Spain was recycled or composted in 2016, which constitutes a significant deviation from the 50% recycling target set by the European Union for year 2020.
Process systems engineering tools can contribute to the design of optimal waste management strategies that fulfill circular economy criteria. However, it has not been demonstrated yet that the implementation of a circular economy will decrease resource consumption and environmental impacts, or that it will not hamper economic growth. Therefore, the objectives of this dissertation are twofold: to develop a methodological framework capable of selecting the optimal configuration of integrated waste and resource management systems under a life cycle perspective, and to investigate whether adopting a circular economy is an effective measure to attain increased economic benefits and a reduction in resource consumption and environmental impacts.
The developed framework – presented in the first paper compiled in this thesis – is based on the expansion of the boundaries of integrated waste management systems to include the upstream and midstream subsystems involved in the previous life cycle stages of the waste components, from resource extraction to waste generation. These systems, categorized as Circular Integrated Waste Management Systems (CIWMSs) in the dissertation, enable assessing the consequences of the recirculation of the recovered waste components into the upstream subsystems. To quantify the circularity of these substances within CIWMSs, a new circularity indicator was proposed and described in the third publication comprised in the dissertation. In the second paper included in this thesis, the developed framework was tested on a case study: the management of municipal organic waste and nutrients in the Spanish region of Cantabria. The system boundaries were defined and a superstructure containing alternative unit processes that could be integrated into the system was designed. The system model describes how industrial fertilizers and the products that could be recovered from municipal organic waste (compost, bio-stabilized material, digestate, struvite and ammonium sulfate) are applied to the soil to grow corn – the main fodder crop in Cantabria – according to different strategies depending on their nutrient composition. Finally, the economic analysis of the studied system is carried out in the fourth publication.
The bottom-up mechanistic model was developed combining different pieces of software to perform the material flow analysis, life cycle assessment and life cycle costing of the unit processes, and to model the distribution of nutrients within the system. A mixed integer linear programming multi-objective optimization problem was formulated based on the equations of the model. The problem is subject to the restrictions of the case study and those imposed by the European waste legislation. The identified objective functions are classified as: - Objective functions that measure the progress toward the achievement of a circular economy: the circularity indicators of carbon, nitrogen and phosphorus.
- Objective functions that quantify different aspects of sustainability: i) resource use: the consumption of non-renewable raw materials and the landfill area, ii) environmental impacts: global warming, marine eutrophication and freshwater eutrophication, iii) economics: the total annual costs of the waste management subsystem.
The results of the optimization indicate the selected unit processes and the material flows that must enter each of them; the solutions to the multi-objective optimization problems were based on the integration of multiple unit processes. The findings of the research – subject to the formulated hypotheses – suggest that improving resource circularity does not necessarily entail a decrease in the overall consumption of natural resources or the emission of environmental burdens. Likewise, it can lead to increased waste management costs, which could be minimized through the cooperation of the different actors involved in the circular system. Thus, the successful implementation of a circular economy must rely on a proper balance between resource circularity and its sustainability implications; the consequences of enhancing resource circularity should be analyzed on a case-by-case basis.
- español
