Enhancing urban waste sustainability through community-driven composting in São Paulo megacity

Abstract

This study addresses the challenge of municipal solid waste management in urban environments, focusing on the case of São Paulo, Brazil. It introduces a community-based, decentralized composting initiative taking place in this city. The initiative began in 2018 by local residents in the city's western region. Community composting took place in public squares using the "Universidade Federal de Santa Catarina method," involving thermophilic decomposition through passive static aeration. Weekly meetings attracted an average of 31 participants from 2018 to 2021. Participants were requested to bring food residues and garden prunings. To construct the compost pile, a layer of straw and thin branches or grass clippings was added to the outer perimeter to create a wall, with weekly feedings during community gatherings for this purpose. This process was repeated weekly until the piles reached a height of around 1.5 m. The compost maturation process was monitored periodically by observing the visual aspect, absence of odors, and temperature. The temperature decreased from approximately 60 °C for a fresh pile to 30 °C when mature, typically after five months. Physico-chemical properties of six piles containing mature compost were analyzed. In the period 2018–2021 over 20 tons of organic waste were composted, resulting in a reduction of approximately 27,662 pounds of CO2 emissions. The compost produced conforms to agricultural standards, with desirable physical and chemical properties, including an acceptable C/N ratio, pH levels, organic matter content, and nutrient concentrations. Heavy metal analyses indicated that the compost's elemental concentrations were well below established limits, ensuring its safety for agricultural use. During the period from 2018 to 2021, more than 20 tons of organic waste underwent composting, leading to a decrease of approximately 27,662 pounds of CO2 emissions. The resulting compost meets agricultural standards, exhibiting favorable physical and chemical characteristics, such as an acceptable C/N ratio, pH levels, organic matter content, and nutrient concentrations. Heavy metals analysis revealed that the elemental concentrations in the compost were significantly below established limits, guaranteeing its safety for agricultural applications. This urban community-driven composting model exemplifies an innovative approach to local waste management, emphasizing citizen engagement, sustainability, and the creation of shared spaces, thereby presenting a viable solution to urban organic waste challenges in São Paulo and beyond.