A transport cost-based optimization for recycling of municipal sludge through application on arable lands

•GIS tools are effective in determining suitable lands for sludge application.•Optimization model was helpful in planning for sludge application.•Seventy five percent of the non-irrigated arable lands were not suitable for sludge application.•Sludge of ACWWTP can be recycled and managed through agricultural use. Agricultural use of sludge is a beneficial alternative for sludge handling and recycling which may improve soil fertility through providing organic matter and nutrients. This study focuses on sludge application scheduling for suitable arable lands. Ankara (Turkey) was the study site. A screening procedure and buffer zone application were conducted to eliminate the arable lands not suitable for sludge application. ArcGIS was used for spatial analysis. Then a transport cost-based optimization model was employed to determine the lands that would be receiving sludge in a management period of 2013 to 2022. The spatial analysis by ArcGIS indicated that 75% of the total non-irrigated arable lands in Ankara were not appropriate for sludge application. Optimization results showed that only 17% of the suitable lands could receive sludge application for the conditions considered in this study. Average costs for sludge transportation in the management period were $84,855/year, $77,299/year, and $62,349/year for truck capacities of 10, 16 and 24t, respectively. Total sludge transportation costs decreased for higher truck capacities. Sensitivity analysis indicated that transportation costs and the area of suitable lands receiving sludge were sensitive to sludge application dosage, application frequency, travel distance, and unit fuel cost escalation.