Regional sustainability of food–energy–water nexus considering water stress using multi-objective modeling and optimization

In this work, a regional optimization model is developed to achieve energy–water nexus sustainability in the context of lignocellulosic biofuels. The regional water availability is determined as a function of precipitation. Detailed water balance at the district level accounts for groundwater recharge and surface water availability. Water left over from the previous season can be used in the next season. The water withdrawal for crops providing agricultural residue to produce ethanol is limited by a seasonal water stress factor. The key decision variables are land allocation for selected crops and choice of residues for ethanol production, all while ensuring state-level ethanol production targets are met. The primary goals are to maximize farmers’ profit, minimize ethanol cost, and minimize water withdrawals while meeting the ethanol production targets. The resulting multi-objective mixed-integer linear programming problem is applied to a case study of 33 districts in Maharashtra, India. Results compare optimized land practices from the model with current practices, where current land use causes 78.5% water stress. Upon further reducing water consumption by 38.5% compared to the current land use practices and for an ethanol blending rate of 15%, profits reduced by 27.6%, from USD 388.06/ha to USD 288.88/ha. The ethanol water footprint decreased 1.7-fold from 937 to 528 liters per liter of ethanol, and irrigation water use dropped 14.8-fold from 3878 to 262 m${}^3$/ha.