Applying a Sustainability Metric in Energy, Water and Food Nexus Applications; A Biomass Utilization Case Study to Improve Investment Decisions

The demand for energy, water and food (EWF) resources will continue to increase, especially as the population is expected to reach 9 billion by 2050. The consequences of this include resource exhaustion and environmental degradation. Global pressures, such as climate change and resources depletion have encouraged the deployment of alternative energy systems and integration of carbon capture and sequestration processes. Currently, most chemicals and energy carriers are derived from finite fossil fuels which are susceptible to price fluctuation. Biomass, a renewable carbon-based fuel can be considered a promising substitute that can reduce environmental footprints in various applications. Gasification is a preferred route for handling biomass, in which the gas mixture (syngas) product is utilised to drive gas turbines and produce clean energy. Moreover, it can also be used to substitute natural gas in the petrochemical plants for methanol and ammonia production. Analysing the utilisation strategy of diverse biomass feedstocks represents a fertile research problem that can be addressed from a EWF Nexus perspective, which enables the quantification of impacts of biomass utilization strategies on the EWF systems. In this study, the utilisation strategy of biomass gasification feedstock for the poly-generation of different products is evaluated from an economic perspective. The Aspen Plus simulation models an oxygen-steam gasification technology to generate the optimal characteristics for each utilisation technique. Moreover, a sustainability metric was utilised to quantify the effect of each technique on EWF resources and to extend the investment decision making. Preliminary results generated from the simulation are integrated into a linear programming optimisation model that identifies the optimum biomass utilisation techniques that consider environmental and economic performances. The framework developed enables the selection of the optimal mix of biomass techniques that maximises sustainability indices for EWF resource systems, whilst ensuring a positive generation of the three corresponding resources. The results demonstrate that urea production and power generation are the most viable biomass utilisation techniques.