Circularity Assessment of Water and Waste in Cities : A Proposed Framework for Sustainable Performance Evaluation using LCA and LCC
Abstract: Urbanization is a global phenomenon, happening on a massive scale and at a rapid rate, with 68% of the planet’s population predicted to be living in cities by 2050 (UN-DESA, 2018). The sustainability of a city (Goal 11 of UN SDGs) undergoing rapid urbanization depends on its ability to maintain a low consumption of resources and materials at any given time (referred to as the urban metabolic rate), whilst simultaneously providing essential municipal services to its inhabitants, such as a water supply, wastewater treatment and solid waste management. The latter must comply with circular economy principles, meaning recovery of byproducts, prevention of discharge of toxic pollutants, and avoidance of landfill usage. The appended papers in the thesis (Papers I–V) describe sustainable assessments of wastewater and waste services to increase their degree of circularity, using tools such as Life Cycle Assessment (LCA) and Life Cycle Costing (LCC). Paper I describes the environmental performance of using the biogas from a Wastewater Treatment Plant (WWTP) and converting it to Liquefied Biomethane (LBM), which can used as fuel in Tractor-Trailers (TT). Overall, the study suggests that changing from diesel to LBM fuel improves the environmental performance of TT. However, the magnitude of environmental benefit depends on an alternate source of electricity required for operation of the WWTP. Paper II evaluates the Social Cost-Benefit Analysis (SCBA) of Compressed Biomethane (CBM) obtained from a food waste digestion plant in Mumbai, India for use as a fuel in transit buses. SCBA results indicate that the food waste-based CBM model can save 6.86 billion Indian rupees (99.4 million USD) annually for Mumbai. Paper III describes the Sustainable Return on Investment (SROI) of lightweight Advanced High Strength Steel (AHSS) and Carbon Fiber Reinforced Polymer (CFRP) intensive multi-material Body in White (BIW) for automobiles. The SROI of CFRP BIWs is maximized when carbon fiber production uses energy from a low carbon-intensity electric grid or decentralized sources such as waste-to-energy incineration plants. Paper IV assesses the ecoefficiency of a thermal insulation panel that consists of a Polyurethane (PU) foam core sandwiched between two epoxy composite skins, prepared by reinforcing Glass Fibers (GF) and SFA (Silanized Fly Ash) in epoxy resin. The results revealed that the ecoefficiency of the composite panels is positive (47%) and superior to that of market incumbent alternatives with PU foam or rockwool cores and steel skins. Paper V quantifies the Total Cost to Society (TCS) (sum of private cost and environmental externalities cost) of a centralized urban WWTP, including the operation as well as byproduct utilization stream. The environmental performance and circular compliance are both factored in, when determining the TCS of a WWTP. The results revealed savings of 1.064 million USD, which include direct and indirect revenues to the plant, as well as avoidance costs attributed to environmental externalities. Based on the studies described in4these papers, a five-stage assessment framework for determining the overall sustainability performance of essential treatment services in a city is proposed in this thesis. The framework considers the combined effect of urban metabolic features and initiatives aimed at improving circular compliance of essential services.
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