Modeling Circular Urban Metabolism in Santiago de Chile: Waste Tire Management

Abstract

Cities account for over 70% of greenhouse gas emissions and consume over two-thirds of the world’s energy. With the continued rise of urbanization, 68% by 2050 as projected by the UN, cities must be redesigned to ensure emissions, and the associated negative impacts of climate change, do not also increase proportionately. One framework through which a city’s sustainability can be analyzed is through the lens of urban metabolism; the inflows, use, and outflows of a city’s resources are viewed as analogous to the functions and processes of an organism. To truly become sustainable, city metabolisms must become “circular,” with high quality resources being recirculated and reused throughout the system, thus diminishing the rate of resource exploitation. Through better understanding of a city’s urban metabolism, governments can implement policies targeting the points of the system with the biggest impact and increase their city’s environmental resilience. Our research focus is on Santiago de Chile, Region Metropolitana, and future management of waste tires. Santiago, as a densely populated city experiencing economic growth paired with rising inequality and environmental sustainability challenges, is an ideal testing ground for innovative environmental policies that could be applied elsewhere in urban Latin America. This material flow is particularly topical as it is one of six products covered by the new Ley de Responsibilidad Extendida del Productor (REP), an extended producer liability law that shifts responsibility of a products’ end-of-life phase from the consumer to the producer. REP is a critical area of interest for the Chilean Ministry of the Environment as well as our client, the EARTH Institute at Universidad Adolfo Ibáñez. We conduct a Material Flow and Impact Analysis of future tire streams in Santiago. Using this analysis, we compare scenarios for managing end-of-life tires (ELTs) to understand which tire circularity strategies will have the greatest positive environmental, social, and economic impact. We find that promoting ELT management strategies that focus on energyrecovery will best promote environmental sustainability and human health while minimizing consumption of water and fossil fuels. There is a tradeoff as energy recovery is more expensive and has a minimal impact on material circularity compared to a baseline scenario and we discuss a potential impact score through the lens of Chilean environmental policy. We further recommend that both an Advanced Disposal Fee (ADF) and a Deposit Refund System (DRS) are considered as potential economic policy instruments to facilitate ELT collection.