Analysis of Urban Sustainability of Araranguá-SC-Brazil Applying Thermodynamic Concepts to Municipal Solid Waste Indexes

Abstract

Each day, humankind adds more and more products into the earth’ life cycle, mostly made out of virgin materials and not accounting how much out there can be reused and reinserted in the chain. The world produces over 2 billion tons of Municipal Solid Waste (MSW) every year and Brazil contributes with 80 million tons to this amount, of which only 3% is recycled. Strategies like Reducing/Reusing/Recycling/Recover (4R’s) must be attached to our thoughts and actions. Also, maximizing exergetic efficiency and minimizing entropy generation can lead to more powerful solutions to this global problem, once the world can be seen as a living organism, where matter and energy are consumed as well as waste, heat and entropy are rejected. In this work, the MSW management system of Araranguá – Santa Catarina State, Brazil is evaluated in terms of exergy and a control volume around the city’s urban center was defined. Streams of fuels such as gasoline, natural gas, liquefied petroleum gas, diesel oil, ethanol and also electricity into the city’s control volume were considered as exergetic inflow. The outlet solid mass flow was calculated by the passage of solid waste across the control volume boundary, on its way to the landfill. Two scenarios were considered: (i) the current one with no solid waste segregation, inconsiderable recycling rate and transportation by trucks; (ii) the ideal one, but feasible scenario, which considers a proper waste separation with the highest material recycling and waste-to-energy generation. The analysis has shown that a correct waste separation can lead to an increase of 1.4% in the exergetic efficiency, which represents 47,137 GJ of exergy potentially recovered and around US $ 300,000 saved in a year, related to less diesel oil consumption and to MSW management system enhancement. The results show that waste-to-energy solutions can be very powerful and effective regarding the world’s solid waste treatment, for cities like Araranguá.