Development of the sugarcane biorefinery economic analysis toolbox (S-BEAT) as a product and process selection support for South African sugar mills.
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In recent years, key stakeholders within the South African Sugar Industry have realised the necessity to diversify their product portfolios further and move from only sugar-based products to the production of chemicals, materials, and fuels. Numerous value-added products can potentially be generated from the available streams in a sugar mill. In theory, these products can supply numerous markets of various sizes and hence generate new revenue streams for the sugar mill. A toolbox, the Sugarcane Biorefinery Economic Analysis Toolbox (S-BEAT) which uses a preliminary cost estimation method, was developed to serve this purpose. S-BEAT provides both a cost estimation and economic analysis at a preliminary process design stage for preselected product and process alternatives in the South African context. S-BEAT makes use of the order of magnitude approach, which is based on data from existing plants. It accepts historical data and escalates the capital investment to the current year, whilst making adjustments for differing product capacities and plant locations. It is estimated that this method has an accuracy of about ±30% to ±50%, which is considered satisfactory for a preliminary cost estimate. The cost estimates then undergo an economic analysis to determine product profitability (Net Present Value (NPV), Internal Rate of Return (IRR) and Discounted Payback Period). S-BEAT allows for a comparison between process and product alternatives, as well as between raw material type (clear juice, mixed juice, syrup, A-sugar, or A-molasses) and quantity (effects of economies of scale) of a sugar mill stream diverted from sugar production to the biorefinery operation. Furthermore, it comprises a sensitivity analysis option which is used to identify those process variables that exhibit the largest effect on the overall economics, serving as pointers for specific process optimisation. With this toolbox, a techno-economic analysis of several products, including high-density polyethylene (HDPE), polylactic acid (PLA), monoethylene glycol, lysine, succinic acid, 1,4- butanediol and 2,5-furandicarboxyllic acid, was conducted. The economics, in the form of the NPV, IRR and Discounted Payback Period, from the aforementioned raw material streams were assessed. Additionally, the Minimum Selling Price that is required to ensure a plant is feasible is included for a range of feedstock costs and numerous plant capacities. The results of this assessment are presented comparatively and provide a basis for decision making for the local sugar industry on which processes and products should be further investigated at a more rigorous techno-economic modelling level. The S-BEAT toolbox is available to the South African Sugar Industry to assess products using in-house specific data. Further products and feedstock streams can be added, to support decision making at this early stage of the industry’s transformation to a diversified industry.