An optimal bioenergy system design framework based on the water-energy-agriculture nexus

Scaling biomass-to-ethanol systems in water-stressed regions is challenging, particularly considering the impacts of climate change. This study presents an optimization model that incorporates agricultural cropping patterns as a decision variable alongside the design of lignocellulosic biorefinery systems. The model aims to identify configurations that prevent overexploitation of regional water resources. Building on a basic optimization framework previously developed for India, this work refines and extends the formulation. Key decision variables include district-level cropping patterns for selected crops, as well as the location, size, and biomass collection strategies of biorefineries to produce ethanol. Four different objectives capture the environmental and socio-economic dimensions of the problem. Regional precipitation is taken as the input, and surface and groundwater availability are modeled as a function of precipitation. A novel aspect of this work is the introduction of simplified linear relationships between groundwater recharge and precipitation, as well as between surface runoff and precipitation, considering regional variations in soil type, slope, and crop type. The model is applied to a case study of Maharashtra, India. The minimum ethanol production cost is ₹47/L ($ 0.56/L), and the maximum farmers' profit is approximately ₹33 550/ha ($ 400.11/ha). A 40% reduction in precipitation due to climate change can double the total irrigation water requirements. The Central Maharashtra Plateau is identified as the most important agroclimatic zone in the state. An increased ethanol blending target increases ethanol costs and reduces farmers' profits. The model can be used as a decision support tool to design the bioenergy system while staying within regional water resource sustainability constraints.