Sustainability assessment framework for chemical production pathway: Uncertainty analysis

The sustainability level of a chemical production pathway is an important element that requires to be assessed when developing a new process. Note that the typical sustainability assessment is normally emphasised on economic and technological development. In order to ensure more comprehensive level of sustainability, the protection on human health and preservation of the environment should be considered. This paper presents a systematic framework for assessment of chemical production pathway based on multi-sustainability criteria, i.e., inherent safety, health and environment (SHE) and economic performance (EP). In order to generate an optimal design solution, uncertainty analysis is also incorporated in this framework. Two optimisation approaches are adapted into this framework, i.e. fuzzy optimisation is used for multi-objective analysis, while multi-period optimisation is applied to address the multiple operational periods with presence of uncertainty. To illustrate the proposed framework, assessment on biodiesel production pathway based on enzymatic transesterification using waste oil is conducted. In the case study, three periods (low, medium and high demand period) of demand for biodiesel are considered, whereby each period is subjected to uncertainties, i.e. waste oil flow rate, waste oil price and enzyme price. To accommodate the uncertainties, sensitivity analysis is performed to determine the feasible operating condition, i.e. tert-butanol concentration and reactor residence time, as well as the appropriate sizing of the process modules (or known as unit operations).