Because a range of tools may be used for system simulation and sustainability characterization, data organization and transfer between these tools can be challenging due to the heterogeneity in data requirements (e.g., file format), despite the fact that the same system inventory is used. For example, for a wastewater-based microalgal cultivation system that recirculates water internally, Aspen Plus ® was used for system simulation, after which the system inventory was exported for TEA in a spreadsheet and LCA using SimaPro. The analysis of other systems has followed a similar workflow, transferring data among multiple tools used for different steps of QSD. Although programming languages can be used to facilitate data formatting and transfer, this nonetheless presents challenges in QSD execution when system simulation and sustainability characterization need to be repeated thousands of times or more to consider uncertainty (Section 5.2). Alternatively, there are ongoing efforts in tool development to integrate system simulation and sustainability characterization on a single, opensource platform (e.g., for sanitation and resource recovery systems, 230 biorefineries 215 ). Though still at the early stage, these tools offer the opportunity for streamlined QSD execution with much greater flexibility, better consistency, and higher computational efficiency, all of which are critical to QSD and its application.