Maximizing RDF recovery potential through the integration of electrical resistivity tomography and frequency-domain electromagnetic surveys for waste characterization in open dump mining.

Open dumping is a widespread waste management technique used in developing countries. This approach is simple and economical but has numerous environmental and health impacts. Open dump mining (ODM) can reduce waste in both open and controlled dumpsites by converting waste into refuse-derived fuel (RDF) for energy generation; however, before ODM implementation, the waste's characteristics and composition must be assessed. Geophysical surveys are widely used to characterize waste. The electrical resistivity tomography (ERT) method is a particularly common technique for determining waste composition, but it has several limitations. Therefore, a frequency-domain electromagnetic (FDEM) survey was used in this study as a pre-screening tool to evaluate the waste composition and overcome the limitations of ERT surveys. This study aimed to determine the relationship between geophysical data types (i.e., ERT and FDEM) and the optimal waste composition for RDF production and assess the ability of FDEM surveys to identify areas with RDF recovery potential. This study combined ERT and FDEM surveys with waste sample analysis in old/new controlled dumpsites in Thailand. The quantitative and qualitative correlations between the geophysical data (i.e., resistivity, conductivity, waste composition, and moisture content (MC)) were then assessed using linear and multiple linear regression analysis. Integrating geophysical surveys was found to have the potential to locate optimal RDF recovery areas, with low conductivity (0-100 mS/m) and high resistivity (>55 Ω·m) characteristics associated with areas of high RDF content (>40 % by weight). An unexpected finding was that increased waste age resulted in increased resistivity and decreased conductivity. Additionally, the MC depended on factors affecting spatial variability (e.g., precipitation and biodegradation). Overall, this study demonstrates that integrating ERT and FDEM surveys is a suitable pre-screening tool to evaluate waste characteristics and composition, mitigate ERT survey limitations, and improve waste investigation before ODM.

Investigating the effect of waste age and soil covering on waste characteristics prior to landfill mining using an electrical resistivity tomography technique.

This study analyzed the potential of landfill mining for refuse-derived fuel (RDF) production based on waste electrical resistivity, including the influence of waste age and soil cover. Electrical resistivity tomography (ERT) was used to determine the resistivity value of landfilled waste in four active and inactive zones, with two to four ERT survey lines collected per zone. Waste samples were collected for composition analysis. Linear and multivariate regression analyses were used to constrain the data correlation based on the waste's physical characteristics. An unexpected finding was that soil cover, rather than the waste's age, influenced the characteristics of the waste. To evaluate the RDF recovery potential, multivariate regression analysis showed a significant correlation between electrical resistivity, conductive materials, and moisture content. However, the obtained correlation between electrical resistivity and RDF fraction using linear regression analysis can be more conveniently used to evaluate RDF production potential in practice.

Optimization of multi-frequency electromagnetic surveying for investigating waste characteristics in an open dumpsite.

Implications: Open dump mining (ODM) is now applied as a sustainable approach to combat improper waste disposal and reduce municipal solid waste (MSW) in the open dumpsite. To implement ODM for producing RDF, business developers must know the amount and composition of waste that can be converted into RDF before mining. This study used multi-frequency EM surveys with frequencies of 5,000, 11,000, and 15,000 Hz. This multi-frequency method effectively determined the waste composition and identified potential excavation points in the open dumpsite prior to ODM. This method can mitigate the limitations of traditional surveying, due to its improved mobility, lower time consumption, and reduced labor needs.