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Conversion of sugar cane A-molasses and lignocellulosic biomass to value-added products: techno-economics and greenhouse gas emissions
Thesis (PhD)--Stellenbosch University, 2025.
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Stellenbosch : Stellenbosch University
2026
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| access_status_str | Open Access |
| author | Phasha, Motshamonyane Jacob |
| author2 | Görgens, Johann |
| author_browse | Görgens, Johann Phasha, Motshamonyane Jacob |
| author_facet | Görgens, Johann Phasha, Motshamonyane Jacob |
| author_sort | Phasha, Motshamonyane Jacob |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/134770 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:44:49.127Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/134770 Conversion of sugar cane A-molasses and lignocellulosic biomass to value-added products: techno-economics and greenhouse gas emissions Phasha, Motshamonyane Jacob Görgens, Johann Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Sugarcane -- By-products Biomass conversion Greenhouse gas mitigation Lignocellulose -- Biotechnology Molasses industry -- Economic aspects Thesis (PhD)--Stellenbosch University, 2025. Phasha, M. J. 2025. Conversion of sugar cane A-molasses and lignocellulosic biomass to value-added products: Techno-economics and greenhouse gas emissions. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/a2287532-dfd6-4ab5-873d-b30600ce5003 ENGLISH ABSTRACT: South Africa has the largest sugarcane production on the African continent, at approximately 18 million tons annually. Currently, biomass generated from sugarcane processing is used to meet the internal energy demands of the sugar mills, even though it can be repurposed for high-value biochemicals and fuel production. Using residues from sugar production, i.e., lignocellulose and molasses, as feedstocks can assist in diversifying sugarcane industries' product portfolios by incorporating desired biorefineries to improve resilience against market fluctuations and other related process inputs. Furthermore, the shift towards biochemicals and fuels may help alleviate greenhouse gas emissions, contributing to the achievement of the Sustainable Development Goals (SDGs), particularly SDGs 8, 9, 12, 13, and 17. This study aimed to determine the most technically feasible, economically viable, and low-GHG-emission process configurations for producing bio-based chemicals from a selected shortlist of products that compete for the limited sugarcane feedstocks within the energy self-sufficient biorefinery concept. Ethyl lactate, muconic acid, ethyl acetate, and butyric acid were selected as potential products due to their high market demand, relatively high market prices, and a wide range of industrial applications. The first objective was to find the best process configuration for producing ethyl lactate (EL) in a sugarcane biorefinery that is energy self-sufficient, based on the lactic acid (LA) and ethanol (EtOH) production as precursors using 1G and 1G2G feedstocks. The study evaluated the fermentation chemistry of LA, separation methods, neutralization agents, and the recovery of by-products to optimize EL production while minimizing costs and greenhouse gas (GHG) emissions. It found that using Mg(OH)2 based on the Corbion ™ process with reactive esterification distillation (RED) reduced operational costs by 38% and energy demands by 15%, achieving a competitive minimum selling price (MSP) of $1664/t compared to fossil-based derivatives at $1850/t. The process configuration generated 14 t/h of EL with specific energy demands of 21.25 kWh/kg and GHG emissions of 1.36 kg CO2 eq/kg, resulting in a 72% reduction in emissions compared to fossil fuels. However, the 1G2G configurations were deemed technically infeasible due to high energy demands, so their economic viability and GHG emissions were not assessed. The second objective was to design and develop conceptual bio-refinery process flowsheets for the production of muconic acid (ccMA) and butyric acid (BA) using 1G (molasses-only) and mixed 1G & 2G sugarcane feedstocks in biorefineries annexed to an existing sugarcane mill. Following the technical infeasibility of 1G2G EL processes/biorefineries in Objective One, where economics and GHG emission evaluations were omitted, the extent of possible gains from 1G2G feedstock integration is evaluated in the ccMA and BA scenarios. Since the muconic acid-producing microbe, P. pudita, can break down solubilized lignin, which makes up over 20% of the 2G sugarcane feedstock, the potential of using solubilized lignin for ccMA production was evaluated in a scenario involving only 1G2G ccMA. Additionally, the co-production of ccMA from solubilised lignin and BA from 1G2G sugars was considered a multi-component process. The recovery of hydrogen as a by-product was evaluated to determine its impact on the MSP. Following the results of using alternative regenerable fermentation neutralisation agents in the first objective, the BA scenarios also investigated the use of alternative neutralisation agents. This resulted in the BA production scenarios being generally more profitable than the ccMA scenarios, with the best scenario achieving a minimum selling price (MSP) of $1400/t against a market selling price of ca. $1700/t. In contrast, the ccMA scenario achieved an MSP of $2364/t despite muconic acid being the least energy-intensive scenario (6.4 kWh/kg), but this was not market competitive as the MSP was about 40% above the market prices. In the 1G2G ccMA scenario, solubilized lignin enabled maximum biomass utilization, improving profitability but increasing GHG emissions (1.61 kg CO2 eq/kg). Using alternative neutralisation agents improved the viability of the 1G BA scenarios. The third objective was to produce ethyl acetate (EA) through catalytic dehydrogenation (CDH) of EtOH, as well as via Fischer esterification (FE) of EtOH with acetic acid (AA), which was investigated. Pressure swing distillation (PSD) and extractive distillation (ED) methods were also investigated for the recovery and purification of EA. The biorefineries were annexed to an existing sugarcane mill and utilised 1G-only or 1G2G sugarcane feedstocks. Following the results of using regenerable neutralisation agents in the previous chapters, the concept was also applied to EA. The impact of selling by-products (such as hydrogen and butyric acid) on the MSP was evaluated. Based on data reported in the literature, the simulations were conducted using Aspen Plus®. The best 1G scenario produced EA at 9 t/h, and the respective specific energy demands of 7.60 kWh/kg_EA and GHG emission reduction of 1.07 kg CO2 eq/kg were achieved. The fourth objective was to benchmark the biochemicals against one another and select biochemicals investigated previously to determine the best chemical(s) for recommendation as the preferred to be produced from the limited sugarcane feedstocks. The comparison was based on MSPs, market size, energy efficiency, and GHG emissions as primary key performance indicators (KPIs). It was found that producing butyric acid from limited feedstock was best, owing to its relatively high energy efficiency, high GHG emission reduction, and competitive MSP. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Doctoral 2026-01-07T09:15:15Z 2026-01-07T09:15:15Z 2025-12 Thesis https://scholar.sun.ac.za/handle/10019.1/134770 Stellenbosch University xiv, 250 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Sugarcane -- By-products Biomass conversion Greenhouse gas mitigation Lignocellulose -- Biotechnology Molasses industry -- Economic aspects Phasha, Motshamonyane Jacob Conversion of sugar cane A-molasses and lignocellulosic biomass to value-added products: techno-economics and greenhouse gas emissions |
| title | Conversion of sugar cane A-molasses and lignocellulosic biomass to value-added products: techno-economics and greenhouse gas emissions |
| title_full | Conversion of sugar cane A-molasses and lignocellulosic biomass to value-added products: techno-economics and greenhouse gas emissions |
| title_fullStr | Conversion of sugar cane A-molasses and lignocellulosic biomass to value-added products: techno-economics and greenhouse gas emissions |
| title_full_unstemmed | Conversion of sugar cane A-molasses and lignocellulosic biomass to value-added products: techno-economics and greenhouse gas emissions |
| title_short | Conversion of sugar cane A-molasses and lignocellulosic biomass to value-added products: techno-economics and greenhouse gas emissions |
| title_sort | conversion of sugar cane a molasses and lignocellulosic biomass to value added products techno economics and greenhouse gas emissions |
| topic | Sugarcane -- By-products Biomass conversion Greenhouse gas mitigation Lignocellulose -- Biotechnology Molasses industry -- Economic aspects |
| url | https://scholar.sun.ac.za/handle/10019.1/134770 |
| work_keys_str_mv | AT phashamotshamonyanejacob conversionofsugarcaneamolassesandlignocellulosicbiomasstovalueaddedproductstechnoeconomicsandgreenhousegasemissions |