Comparing the Agronomic and Economic Aspects of Sewage Sludge Composting and Vermicomposting

In recent decades, the urban population of Ecuador has grown, increasing the need for wastewater sanitation in cities. Wastewater treatment in this country generates sewage sludge (SS), which is mainly deposited on land near wastewater treatment plants or in sanitary landfills, generating significant environmental impacts. In view of this, composting or vermicomposting of SS can be suitable treatments for this waste, and the final materials obtained can be used as or-ganic amendments. The objective of this study was to compare the agronomic and economic aspects of composting and vermicomposting using the same SS mixtures with different plant residues. For this purpose, the evolution of various physicochemical and biological parameters of both processes, the quality of the materials obtained, and the costs of their production were evaluated. The results revealed that all the amendments presented organic matter with an ade-quate degree of maturity and levels of heavy metals and pathogenic microorganisms suitable for safe agricultural use. The vermicomposts had significantly lower levels of salts and higher levels of most macro- and micronutrients than the composts, thus increasing their economic value. However, the average production cost of composts was lower than that of vermicomposts. Thus, the choice of the most advisable method of SS treatment (composting/vermicomposting) should consider the agronomic and economic value of the nutrients in the compost and vermicompost, as well as the operating costs.