Methods & Concepts

The suite of existing South African decarbonization modelling studies were assessed to determine whether they: 

• Are well-regarded and relevant to the South African policy discourse.
• Include the Secunda and Sasolburg facilities and some of the linked activities.
• Have results in the public domain and/or assumptions and inputs could be readily accessed through engagement with the modellers.
• Are aligned with, at a minimum, the goals of the Paris Agreement.
• Assess implications for socio-economic development, with a broad definition being allowed for how this is determined.

The projects of the University of Cape Town Energy Systems Research Group (ESRG) and that developed by BCG for the National Business Initiative (NBI) pathways for a just transition study stood out. Both of these modelling exercises have directly informed the South African mitigation policy discourse (see for example the PCC’s recommendations for updating the First NDC).

Other modelling exercises were explored, but not considered suitable for inclusion. For example, the Analytica model developed by The Green House had not yet been adapted to model 1.5ºC aligned pathways and was not available for independent use by the project team. Various international studies have been conducted but the data was not available to the required resolution.

The two selected studies outline discrete futures for the facilities and trajectories for their linked activities. The futures represented by these models are determined by: 

• Data inputs, assumptions and constraints, and
• Types of models used:
• The ESRG model is an optimisation model developed in specialised software.
• The BCG model is largely a simulation model developed in Excel.

Given the differences between the models, and the fact that all models only represent a potential stylised view of the future, it was not considered valuable to distinguish explicitly between the model outputs further in this study. 

Rather, the study draws on aspects of the modelling outputs to describe the implications of Paris-Aligned decarbonisation for the facilities and linked activities, along with the implications thereof.

It is recognised that energy and economic modelling associated with analysing national decarbonisation trajectories is a highly complex exercise, necessarily abstracting from detail in order to cover the breadth of the national economic and energy systems involved.  As such, it’s not always possible to accurately glean from reports the myriad of assumptions utilised in the modelling process. 

Where possible, the project team analysed the underlying data, and engaged with the modelling teams in order to better understand how the models have treated the petrochemical and chemical assets and their related activities.  However, it is to be anticipated that certain aspects have been missed or incorrectly interpreted, highlighting  a fundamental challenge with relying on highly technically complex and abstract models to support policymaking.