Characterization and potential uses of municipal solid waste incineration remnants in San Andrés Islands – Colombia

Abstract

The incineration of municipal solid waste (MSW) has become a widely adopted option in various countries for waste management. The incineration process generates by-products such as fly ash, calcium salts, and bottom ash. These remnants exhibit a variable chemical and mineralogical composition depending on their origin and operational parameters, and they also have potential environmental impacts that restrict their final disposal or potential uses. In this study, we performed physical characterization, including particle size distribution (PSD) and bulk density measurements, alongside chemical and mineralogical analyses such as X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The material studied comprised incineration residues from municipal solid waste generated on San Andrés Island, Colombia. As the first municipal solid waste incineration plant in the country, the objective of this study was to gather relevant information necessary for its management and potential applications of their by-products. This study establishes the scientific basis for transforming these residues into valuable resources. Findings highlight their high potential for reuse in the manufacture of construction materials, facilitated by simple pretreatment processes such as size separation and grinding. Such applications could deliver significant environmental, social, and economic benefits by promoting sustainability and reducing waste. The results indicate that fly ash, predominantly composed of chlorine and Na₂O (∼70 wt%) mainly in form of non-diffracting phases, halite and sylvite, showing a potential use as a flux material. Calcium salts, containing 25.3 wt% CaO and 22.6 wt% chlorine, can serve either as a calcium-based raw material or as a flux. Meanwhile, bottom ash, with a high content of SiO₂, CaO, and Al₂O₃ (∼78.5 wt%), could be used as a partial replacement for aggregates in concrete or mortar after grinding and sieving. The quantification of amorphous content by Rietveld refinement was of great relevance in the research in order to evaluate the reactivity of the different incineration remnants. The presence of heavy metals, including lead, cadmium, and copper, underscores the necessity of implementing appropriate safety measures to mitigate potential risks to human health and the environment. This research not only provides critical insights into the management of incineration residues but also delivers valuable information to inform decision-making based on technical criteria for their reuse.