Invisible Green Guardians: A long-term study on informal waste pickers' contributions to recycling and the mitigation of greenhouse gas emissions

Recycling plays a crucial role in the circular economy by reintroducing materials into the supply chain. However, certain aspects of the recycling chain, such as the role of informal waste pickers remain underappreciated, despite their significant impact on energy savings and CO 2 recovery. This study investigates the contribution of informal waste pickers to the recovery of recyclable solid waste in Salvador, one of the largest cities in South America, over a 13-year period. Using data from pre-recycling centers that exclusively handle materials collected by waste pickers, we tracked the temporal impact of their activities in diverting solid waste from landfills. From 2010–2022, waste pickers recovered approximately 5700 tonnes of recyclable solid waste, preventing an estimated 27,100 tonnes of CO 2 emissions through material substitution and landfill diversion. The most recovered materials were PET, aluminum, and paper/cardboard, with a notable shift toward increased aluminum recovery. Aluminum and PET contributed most to avoided emissions, with aluminum surpassing PET in recent years. This study underscores the critical yet often undervalued role of informal waste pickers in municipal solid waste management (MSWM) and their contribution to greenhouse gas emission reductions. Given the global prevalence of waste pickers, particularly in low- and middle-income countries, further research on this topic could significantly enhance awareness of the benefits derived from their labor. Recognizing and integrating informal waste pickers into formal waste management systems could strengthen sustainability initiatives in cities and enhance climate change mitigation strategies under dynamic needs of urban populations. • Informal waste pickers had a pivotal role in recyclables recovery and GHG emission reduction in a large urban center. • Temporal analysis reveals a dynamic shift in material recovery and annual CO 2 mitigation. • Recognizing and integrating informal waste pickers is therefore essential for sustainable urban waste management.