“The cane price could become a function of not only the sugar content, but also of the value of its other components used in the biorefinery processes. We might even choose to grow cane not for its sugar, but maybe for hemicellulose or cellulose: after all, sugarcane is one of the most efficient plants able to convert sunlight and carbon dioxide to chemical bonds storing energy.” Professor Annegret Stark, SMRI/NRF SARChI Research Chair in Sugarcane Biorefining at the University of KwaZulu-Natal

Biorefining is an international trend which perhaps sooner rather than later is going to take off in South Africa and award-winning chemical engineer, Prelene Naidoo (25) says she wants to be at the forefront of its development in the country.

Naidoo is this year’s winner for the South African Sugar Technologists’ Association’s (SASTA) Robin Renton Memorial Award.

The award, which is donated by PGBI Engineers and Constructors, is for an engineer younger than 35 years of age who shows leadership and management potential and delivers an outstanding technical paper at the SASTA’s annual congress. The recipient receives a cash prize and a medal.

Naidoo was first introduced to the sugar industry in 2016, when she and a partner selected the topic “Optimization of the production of sugarcane bagasse briquettes” as their 4th year laboratory project. This was under the supervision of Professor Annegret Stark, and Dr Kitty Foxon and Dr Richard Loubser of the Sugar Milling Research Institute NPC (SMRI).

As an undergraduate, Naidoo then presented the work as a poster and a presentation at the 2016 South African Institute of Chemical Engineer’s Research Day hosted at the university. “I was up against postgraduate students and I came out first – I won – and that’s when I thought, I want to be a part of the sugarcane industry” Naidoo said.

But it is her work on cost estimations on sugarcane biorefineries that attracted much attention of the judges at the SASTA Congress.

“Professor Stark offered the subject to me for my master’s degree. In my opinion, doing research and developing solutions for biorefining in South Africa is much better than working in the petroleum industry for example. I feel better about it for the sake of the environment. I believe I can make a real difference,” she said.

“Also, what was very important to me is that I didn’t want to create a masters that would end up sitting on a shelf and no-one would see it again. I wanted the outcome to be relevant and something the industry could use.”

As a result, Naidoo – who has been fully employed at the SMRI since February 2018 – structured the work as an Excel workbook. This workbook is able to extend the research institute’s existing New Product Greenhouse (NPG) toolbox developed by SMRI researcher Dr Kim Booysen, by including CAPEX and OPEX. Furthermore, it features a cost estimation and economic analysis tool, which allows for the selection of the most economically attractive products or processes for biorefining, at a preliminary design stage.

“I had limited coding experience, so I taught myself advanced Microsoft Excel coding with textbooks, Excel workbooks and YouTube videos. Certain examples involving user forms spoke to me and I realised that the cost estimations methodology could become a really cool program which is user-friendly and intuitive.” After some investigations, and trial and error programming, Naidoo has come up with a simple workbook-styled solution which she has called the Sugarcane Biorefinery Economic Analysis Toolbox, or S-BEAT for short.

To demonstrate the potential of the toolbox, the young engineer used the production of bio-polyethylene (HDPE) and polylactic acid (PLA) from clear juice as a case study of the biorefining options. The resulting economic analysis was then able to highlight the commercial attractiveness of the processes as assessed by the tool. A future case study will compare the economics of using A-molasses as a feedstock, in place of clear juice.

And it was for this work that Naidoo won the Robin Renton award.

Professor Stark said the spreadsheet-based S-BEAT, which could be used for quick decision making and built on the existing NPG Toolbox, not only allowed for an understanding of how the choice of the sugar mill stream would affect the overall process economics, but it could also be used to compare different product and process alternatives for millers wanting to diversify their production streams.

“In principle, there is a tremendous number of industrially interesting products that processors could make through various processes from sugarcane. For any company wanting to expand their product portfolio, the question arises, which one would be the most economically viable?”

And while she agreed that sugar millers would also base a diversification decision on their existing product portfolio, market access, location, production capacity, feedstock availability and available investment capital for example, S-BEAT would intelligently inform the decision-making process.

“We are populating this toolbox with further products and processes for which industrial data is already available. This is the platform which will be provided to our industrial partners to help in their decision making. After narrowing down the number of processes and product alternatives, more detailed process modelling and costing exercises will be carried out. At this stage, company-specific data can be implemented,” Stark said.

Naidoo’s work has linked a number of recent research outputs of the SMRI and Stark’s Biorefinery Research Chair, including Dr Booysen’s NPG toolbox, the Generic Sugarmill ASPEN® Model by Kylan Guest, as well as market studies and economic analysis of the bio-based polymer industry in South Africa by Warwick Thomson. This will facilitate the implementation of further processes and potential products made from sugarcane in the future. The above-mentioned projects fall within the scope of the “Sugarcane Technology Enabling Programme for Bioenergy” (STEP-Bio), a public: private partnership between the South African sugarcane processing industry and the national Department of Science and Technology’s Sector Innovation Fund.

Stark said biorefining offered a unique opportunity for the agricultural and chemical sectors in South Africa. “Bagasse, for example, can be turned into a number of industrially interesting products by separating the biomass into its lignin, hemicellulose and cellulose fractions, which can then be reacted to various products by either chemical reactions or fermentations. We investigate the market potential and prices of these products in South Africa and abroad. This is where S-BEAT comes in. It is obvious that once a few specific products have been identified, the market-pull will impact directly on the agricultural activities,” she said.