Combined use of GIS and mixed-integer linear programming for identifying optimal agricultural areas for sewage sludge amendment: A case study of Catalonia

This work proposes a systematic decision-making tool for identifying the best geographical areas for sewage sludge (SS) amendment in terms of economic and environmental criteria. Our approach integrates GIS and multi-objective mixed-integer linear programming (MILP) within a unified framework that allows exploring in a rigorous and systematic manner a large number of alternatives for sewage sludge amendment from which the best ones (according to the decision-makers' preferences) are finally identified. The capabilities of our methodology are illustrated through its application to a case study based on Catalonia (NE of Spain). The tool presented provides as output a set of optimal alternatives for sewage sludge distribution, each one achieving a unique combination of economic and environmental performance. Our ultimate goal is to guide decision-makers toward the adoption of more sustainable patterns for sewage sludge amendment.