Spatial multicriteria analysis to select suitable sites for sewage sludge use in agriculture: a case study in southeast Brazil

If adequately treated, sewage sludge can be a safe and sustainable source of nutrients and organic matter for soil enhancement, improving agriculture productivity. To close loops in the sewage treatment-agriculture nexus, it is crucial to compare sludge generation (quantity and location of treatment plants) and possible sites for sludge application on a regional level. This study used spatial multicriteria analysis to assess land suitability for sludge application based on several criteria related to soil, land use characteristics, and environmental legal constraints. The study area comprised two large watersheds (a total area of 52,870 km(2)) in Minas Gerais state, southeast Brazil. Results indicated a total sludge production of 21,778 t dry solids.year(-1), which is currently mainly disposed of in landfills (76%). Even though approximately 52% of the study area presented constraints to sludge application in agricultural fields, suitable areas can receive the total amount of sludge generated. In some cases, the most suitable areas would afford for a capacity 20-fold bigger than the sludge produced. Although other factors should be addressed for effectively applying sludge to agriculture (e.g. social acceptance), this work shows the usefulness of the spatial multicriteria analysis tool to select suitable sites.

Automated summary

If properly treated, sewage sludge can be used as a sustainable source of nutrients and organic matter for enhancing soil quality and increasing agricultural productivity. This study used spatial multicriteria analysis to identify suitable areas for sludge application based on various criteria related to soil, land use characteristics, and environmental regulations. The results showed that, although there are some constraints, there are enough suitable areas in the study region to accommodate the total amount of sludge generated. The findings highlight the potential of spatial multicriteria analysis as a tool for selecting appropriate sites for sludge application.