Integrated environmental assessment of municipal solid waste management scenarios in the Guadalajara Metropolitan Area, Mexico

Abstract

Municipal Solid Waste (MSW)—more commonly known as trash or garbage—consists of everyday items we use and then throw away, such as product packaging, bottles, food scraps, and batteries among others. This comes from our homes, schools, hospitals, and businesses. Inadequate MSW management can significantly impact human and ecosystems health, particularly the most vulnerable population groups. Governments around the world have addressed this issue through the adoption of circular economy approaches. The Latin America and the Caribbean (LAC) region and Mexico have also taken their first steps toward this transition. Furthermore, the Mexican State of Jalisco, has decided to face the MSW mismanagement problems through the development of the ‘Jalisco Reduce’ policy with the introduction of Mechanical Biological Treatment (MBT) facilities in one of the most populated Mexican cities: the Guadalajara Metropolitan Area (GMA). The MBT is a solid waste treatment technology which combines the mechanical separation of the recoverable materials contained in MSW with the biological stabilization of organic matter via processes such as anaerobic digestion or composting. Therefore, this work aimed to assess the feasibility of MBT implementation in the GMA and LAC countries through two approaches: i) a comparative analysis of the MBT study cases reported for LAC region and developed European countries to compile the experiences and lessons learned to improve the implementation of MBT plants in lesser developed or developing countries. Furthermore, the main technological, sociocultural, economic, and political challenges that LAC countries must overcome to facilitate the transition of MSW management system to circular economy schemes were identified and discussed, and ii) an environmental performance evaluation of current MSW management model and two potential scenarios for the improvement of MSW management in a GMA subsystem, composed of four municipalities: Guadalajara, Tonala, Tlajomulco and El Salto, which currently dispose of their MSW at a closing sanitary landfill. The two potential scenarios include a mechanical treatment plant and a mechanical biological treatment plant, which are currently being considered as alternatives to transition towards a circular economy. Global warming potential (CO2-eq) and abiotic resources depletion (Sb-eq) were employed as environmental indicators for the evaluation. The comparative analysis was performed between the cases reporting the projection or an implementation of an MBT plant in developing countries in Latin America (Chile, Brazil, Argentina, Mexico) and developed countries in the Europe (Germany, Croatia, Spain, France, Poland, Slovenia, Greece and Italy). The comparison suggested that LAC region countries must initially characterize the MSW which will be the input to the MBT facilities to allow for the optimal design of the treatment plant in accordance with the treatment goals. Additionally, because the rates of source separation and material recovery are very low in these countries and the Organic Fraction of Municipal Solid Waste (OFMSW) is high in the countries of the LAC region (37.16%, 33.60% and 52.50% for Europe and Central Asia, North America and LAC regions, respectively) agreements must be made with the largest organic waste generators (food markets, municipals gardening and pruning departments, schools, among others), to obtain high purity streams of organic waste for the production of high-quality compost or biogas. Furthermore, other main challenges for the countries in the LAC region to transition to circular economy schemes for MSW management are the reinforcement of the monitoring and control of the disposal sites; the implementation of source-separation and selective collection mechanisms; the inclusion and formalization of the waste pickers activities in the MSW management system; the establishment of formal valorization markets; the implementation of policies of monetary responsibility for the waste generators; the promotion of intermunicipal cooperation schemes; and the development of technically skilled human resources who can conduct evaluations and provide advice for the decision making process were identified as the key challenges. Regarding the environmental evaluation, results indicate that the current MSW management system (baseline) contributes with 111.21 Gg CO2-eq/year to Jalisco State’s GHG emissions, while the two potential scenarios displayed net reductions of 24-34% of CO2-eq emissions, due to the avoided emissions resulting from the recovery of valuable materials and the potential partial substitution of petroleum coke by refuse-derived fuel in cement kilns, despite the increase in energy demand derived from the implementation of the treatment plants. Regarding the abiotic resource depletion, the rates of material recovery in the current scenario produce a reduction of 0.16 Gg Sb-eq/year, which constitutes a minimal fraction compared to the potential reduction in fossil fuels when considering the avoided coke extraction, which provides a reduction of 5.62 Gg Sb-eq/year. The sensitivity analysis revealed that some key parameters, such as the fraction of food and kitchen and plastic waste in the MSW, can alter the ranking order of scenarios (always being the current management model the less preferred option).