Abstract
The ISA, based on system theory, is the best way to organize knowledge and exchange it. It depends on defining every system through its boundary, main processes within this boundary, and exchange with the environment through this boundary. It relies upon thermodynamics and information theory and is, therefore, applicable to all kinds of systems, which makes it most suitable for cross-disciplinary investigations and innovation. SD is complex and cross-disciplinary by its very nature and, therefore, the ISA is the best way to investigate its different subsystems. Among the most important subsystems of SD are integrated bio-refineries and bio-fuels, both of which are investigated in this article.