In a transition towards a sustainable petrochemical industry, its systemic structure and functions must be considered degrees-of-freedom in the search for and the specification of development options that reach beyond traditional research and development (R&D) and beyond the optimization of proven technology, proven system concepts and established process networks. Functional modelling allows technology-free specification of systems, generalization of system concepts, and recalibration of the use or value of substances in a petrochemical network. It facilitates moving up or down the ladder of system aggregation levels, which allows one to 'step out of the box' to the plant or chemical complex level, or alternatively to connect to the unit-operation level. Application to the aromatics industry serves to illustrate that thereby the abstraction from present system content and from proven technology is achieved, which allows the specification of the desired content of technological inventions that enable or rely upon changes in system structure: process system innovations. The realization of trigenerate functions through the petrochemical industry involves a paradigm-shift. Rather than considering the industry a threatening source of pollution, safety and health risks, it is an enabler of global CO2 emission reduction.