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Process development for ethanol production from cellulose-rich bagasse residues after furfural production
Bunga, G. E. 2025. Process Development for Ethanol Production from Cellulose-Rich Bagasse Residues after Furfural Production. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/6fbfddf3-9bf1-4612-bec0-20b4e4edb985
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613915920203776 |
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| access_status_str | Open Access |
| author | Bunga, Godrick Emmanuel |
| author2 | Van Rensburg, Eugene |
| author_browse | Bunga, Godrick Emmanuel Van Rensburg, Eugene |
| author_facet | Van Rensburg, Eugene Bunga, Godrick Emmanuel |
| author_sort | Bunga, Godrick Emmanuel |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Bunga, G. E. 2025. Process Development for Ethanol Production from Cellulose-Rich Bagasse Residues after Furfural Production. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/6fbfddf3-9bf1-4612-bec0-20b4e4edb985 |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132092 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:43:44.261Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132092 Process development for ethanol production from cellulose-rich bagasse residues after furfural production Bunga, Godrick Emmanuel Van Rensburg, Eugene Gorgens, Johann F. Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Cellulosic ethanol Sugar -- Manufacture and refining -- By-products Furfural Bagasse Ethanol UCTD Bunga, G. E. 2025. Process Development for Ethanol Production from Cellulose-Rich Bagasse Residues after Furfural Production. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/6fbfddf3-9bf1-4612-bec0-20b4e4edb985 Thesis (MEng)--Stellenbosch University, 2025. ENGLISH ABSTRACT: Cellulosic ethanol production is often costly, where the pretreatment process and enzymatic hydrolysis contribute to high capital and operational costs. In this study, cellulose-rich furfural residues (FRs) from a South African sugar mill were used as feedstock for cellulosic ethanol production. The FRs used are the by-product of the furfural production process, which uses sugarcane bagasse as raw material. Furfural is produced industrially by treating bagasse at 184 °C and 10 bar for 80-90 minutes, using the by-products, acetic and formic acids to catalyse the process. After removal of furfural by steam-stripping, the resulting cellulose-rich FRs have the potential to be converted into ethanol, and provide process energy. The FRs can eliminate the need for a pretreatment process, provided that the residues exhibit excellent enzymatic digestibility. Conversion of FRs can add value to the sugar industry, which is under increasing pressure from economic forces in the sugar markets. This study investigated critical aspects of FRs to 2G ethanol process, aiming to achieve acceptable process performance, while minimising the operational costs of enzymes and yeasts for the process. The latter was essential since the hydrolytic enzymes that digest the cellulose into fermentable sugars are by far the greatest operational cost, which, if left unchecked, would render this process economically infeasible. To achieve this target, four commercial enzyme cocktails, namely, Cellic® CTec3, SacchariSEB C6L Plus, Viscamyl™ Flow, and Cellic® CTec3 HS, were screened to identify the most efficient and least costly options, together with seven Saccharomyces cerevisiae strains, of which two strains, namely Cellusec® 2.0 and Cellusec® 3.3 secreted cellulase enzymes. The latter two strains were essential to minimise commercial enzyme dosages, while achieving attractive ethanol yields, concentration and productivity to minimise operational costs. To maximise performance and productivity, fermentations were done in fed-batch simultaneous saccharification and fermentation (SSF) to maximise the solids loading and maintain an ethanol titre of > 30g/L. Whereas ethanol concentrations of 36 g/L at 89% yield could be achieved at a high enzyme dosage of 5 FPU/g DS and a solid loading of 15% (w/w), which served as a benchmark, the enzyme-producing yeast S. cerevisiae strain Cellusec® 3.3 could reduce the exogenous enzyme dosage to 2 FPU/g DS, albeit at a decreased ethanol concentration of 24.9 g/L (60% yield) at a solid loading of 15% (w/w). Further decrease of exogenous enzyme dosage to 1.5 FPU/g DS was achieved at a high solid loading of 25% (w/w), but this was associated with accumulation of fermentation inhibitors, thus limiting the final ethanol concentration to 19 g/L at 21% yield, with residual glucose of 45 g/L remaining at the end of fermentation. Whereas research is ongoing on further process development to circumvent the issue of residual glucose accumulation, an ethanol titre of 41 g/L was theoretically possible should all the residual glucose at the end of fermentation be converted into ethanol. The study successfully lowered commercial enzyme dosage, which could lead to reduced operational costs associated with exogenous enzymes. Consolidated bioprocessing (CBP) yeasts that secrete cellulase enzymes should be engineered to withstand inhibitors, to maintain viable yeast cells and increase ethanol production. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Masters 2025-05-23T07:38:15Z 2025-05-23T07:38:15Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132092 Stellenbosch University xv, 153 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Cellulosic ethanol Sugar -- Manufacture and refining -- By-products Furfural Bagasse Ethanol UCTD Bunga, Godrick Emmanuel Process development for ethanol production from cellulose-rich bagasse residues after furfural production |
| title | Process development for ethanol production from cellulose-rich bagasse residues after furfural production |
| title_full | Process development for ethanol production from cellulose-rich bagasse residues after furfural production |
| title_fullStr | Process development for ethanol production from cellulose-rich bagasse residues after furfural production |
| title_full_unstemmed | Process development for ethanol production from cellulose-rich bagasse residues after furfural production |
| title_short | Process development for ethanol production from cellulose-rich bagasse residues after furfural production |
| title_sort | process development for ethanol production from cellulose rich bagasse residues after furfural production |
| topic | Cellulosic ethanol Sugar -- Manufacture and refining -- By-products Furfural Bagasse Ethanol UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132092 |
| work_keys_str_mv | AT bungagodrickemmanuel processdevelopmentforethanolproductionfromcelluloserichbagasseresiduesafterfurfuralproduction |