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Determining the effect of micro-aeration on the anaerobic digestion of lignocellulosic biomass
Thesis (MEng)--Stellenbosch University, 2025.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613800771878912 |
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| access_status_str | Open Access |
| author | Kuyler, Judi |
| author2 | Van Rensburg, Eugene |
| author_browse | Kuyler, Judi Van Rensburg, Eugene |
| author_facet | Van Rensburg, Eugene Kuyler, Judi |
| author_sort | Kuyler, Judi |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132229 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:41:54.752Z |
| 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:10019.1/132229 Determining the effect of micro-aeration on the anaerobic digestion of lignocellulosic biomass Kuyler, Judi Van Rensburg, Eugene Gorgens, Johann Ferdinand Mamphweli, Ntshengedzeni Sampson Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Lignocellulose as feed Sewage -- Purification -- Anaerobic treatment Agricultural wastes -- Biodegradation Biomass chemicals UCTD Thesis (MEng)--Stellenbosch University, 2025. Kuyler, J. 2025. Determining the effect of micro-aeration on the anaerobic digestion of lignocellulosic biomass. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/2d54b804-fbe4-4b52-9a5d-9c25879de36b ENGLISH ABSTRACT: Anaerobic digestion (AD) is a mature technology that converts various organic feedstocks into biogas, capturing methane to reduce greenhouse gas emissions. The products from AD, biogas and digestate, can serve as an energy source and organic fertiliser, respectively. Despite the advantages of AD, the process has several drawbacks, such as a slow hydrolysis rate for lignocellulosic feedstocks, instability at high organic loading rates, and hydrogen sulphide production in the biogas. These issues can potentially be overcome through micro-aeration by exposing facultative anaerobic bacteria to low oxygen levels, enhancing their growth rate, activity, diversity, and the associated production of hydrolytic enzymes. In turn, this increases the hydrolysis rates, biogas and methane yields, improves hydrogen sulphide scavenging from the biogas, and improves volatile fatty acid (VFA) production while simultaneously allowing for a more stable process through the rapid consumption of VFAs. The project aims to determine the role of micro-aeration in enhancing the AD of lignocellulosic biomass (LCB) such as corn stover (CS). This was achieved by developing an effective micro-aeration experimental setup, establishing a foundational understanding of the AD profile of CS, and assessing the effect of various micro-aeration flow rates that will enhance hydrolysis performance, evident from the methane production while not resulting in inhibition of obligate anaerobic methanogens. To develop a functional pilot scale micro-aeration system, 50 L digesters (continuously stirred tank reactors (CSTR)) with a built-in gas measuring system were modified by including a flow sensor, pressure regulator, control valve, and a sparger. Eight micro-aeration flow rates ranging from 0.0002 to 0.86 L O2/L reactor.day were assessed on a continuous aeration basis. The biogas and methane yields, VFA profile, pH, and degradation of the substrate were compared to the non-aerated AD of milled untreated CS. Results indicated that micro-aeration rates lower than 0.035 L O2/L reactor.day improved the AD of CS, specifically the methane yield, with improvements of up to 45.7% using an aeration rate of 0.002 L O2/L reactor.day. In contrast, 0.10 L O2/L reactor.day was identified as a threshold aeration rate, and aeration at this rate or higher negatively affected the methane yield. A significant increase in VFA production for all oxygen flow rates was observed with no inhibition from an acid crash: This indicates that the system’s robustness and capability to handle elevated levels of VFAs were improved. The increase in VFA production was supported by an increase in substrate degradation. Although this implied that hydrolysis and acidification were improved, the higher micro-aeration flow rates, showing the greatest increase in VFA production, resulted in a decreased methane yield due to high carbon dioxide production. Furthermore, the study showed that the outcome of the AD process can be controlled by the micro-aeration flow rate as low flow rates (0.0002 to 0.035 L O2/L reactor.day) favoured methane production, while higher flow rates (0.10 to 0.86 L O2/L reactor.day) favoured VFA production. The study successfully showed that micro-aeration can improve the AD of CS and further enhance the appeal of AD as an approach to waste diversion and renewable energy production. AFRIKAANSE OPSOMMING: Anaërobiese vertering (AD) is 'n erkende tegnologie wat verskeie organiese voerstowwe omskakel in biogas, wat metaan vasvang om kweekhuisgasvrystellings te verminder. Die produkte van AD, biogas en verteerde materiaal, kan onderskeidelik dien as 'n energiebron en organiese kunsmis. Ten spyte van die voordele van AD, het die proses verskeie nadele, soos ‘n stadige hidrolise-tempo vir lignosellulose voerstowwe, onstabiliteit by ‘n hoë organiese ladingstempo, en die produksie van waterstofsulfied in die biogas. Hierdie nadele kan potensieel oorkom word deur mikro-oksidasie deur fakultatiewe anaërobiese bakterieë bloot te stel aan lae suurstofvlakke, wat hul groeikoers, aktiwiteit, diversiteit en die gepaardgaande produksie van hidrolitiese ensieme verhoog. Dit verhoog op sy beurt die hidrolise-tempo's, biogas- en metaanopbrengste, verbeter die verwydering van waterstofsulfied uit die biogas, en verhoog die produksie van vlugtige vetsure (VFA), terwyl dit terselfdertyd 'n meer stabiele proses toelaat deur die vinnige verbruik van VFAs. Die projek het ten doel om die rol van mikro-oksidasie in die verbetering van die AD van lignosellulose biomassa (LCB) soos mieliereste (CS) te bepaal. Dit is bereik deur die ontwikkeling van 'n effektiewe mikro-oksidasiestelsel, die vestiging van 'n fundamentele begrip van die AD-profiel van CS, en die assessering van die effek van verskeie mikro-oksidasie vloeitempo's wat die hidrolise prestasie sal verbeter, blykend uit die metaanproduksie, terwyl dit nie lei tot inhibisie van verpligte anaërobiese metanogene nie. Om ‘n funksionele kleinskaalse mikro-oksidasiestelsel te ontwikkel, is 50 L reaktore (voortdurend geroerde tenkreaktors (CSTR)) met 'n ingeboude gasmeetstelsel aangepas deur 'n vloeisensor, drukreguleerder, beheerklep en 'n gasverspreider in te sluit. Agt mikro-oksidasie vloeitempo's wat wissel van 0.0002 tot 0.86 L O₂/L reaktor.dag is op 'n deurlopende oksidasie basis geëvalueer. Die biogas- en metaanopbrengste, VFA-profiel, pH en afbreking van die substraat is vergelyk met die AD sonder mikro-oksidasie van gemaalde, onbehandelde CS. Resultate het aangedui dat mikro-oksidasie tempo's laer as 0.035 L O₂/L reaktor.dag die AD van CS verbeter het, spesifiek die metaanopbrengs, met verbeterings van tot 45.7% deur gebruik te maak van ’n oksidasie tempo van 0.002 L O₂/L reaktor.dag. In teenstelling hiermee is 0.10 L O₂/L reaktor.dag geïdentifiseer as 'n drempel oksiedasie tempo, en oksidasie teen hierdie tempo of hoër het die metaanopbrengs negatief beïnvloed. 'n Beduidende toename in VFA-produksie vir alle suurstofvloeitempo's is waargeneem met geen inhibisie as gevolg van versuring. Dit dui daarop dat die stelsel se robuustheid en vermoë om verhoogde vlakke van VFAs te hanteer, verbeter is. Die toename in VFA-produksie is ondersteun deur 'n groter afbreking van die substraat. Alhoewel dit impliseer dat die hidrolise en asidogenese fases verbeter is, het die hoër mikro-oksidasie tempo's wat die grootste toename in VFA-produksie getoon het, gelei tot 'n verminderde metaanopbrengs as gevolg van hoë koolstofdioksied produksie. Verder het die studie getoon dat die uitkoms van die AD-proses beheer kan word deur die mikro-oksidasie tempo, aangesien lae vloeitempo's (0.0002 tot 0.035 L O₂/L reaktor.dag) metaanproduksie bevoordeel het, terwyl hoër vloeitempo's (0.10 tot 0.86 L O₂/L reaktor.dag) VFA-produksie bevoordeel het. Die studie het suksesvol getoon dat mikro-oksidasie die AD van CS kan verbeter en verder die belangstelling in AD kan versterk as 'n benadering vir die verwerking van afvalmateriaal en hernubare energie produksie. Masters 2025-05-30T09:48:58Z 2025-05-30T09:48:58Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132229 en Stellenbosch University xxix, 235 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Lignocellulose as feed Sewage -- Purification -- Anaerobic treatment Agricultural wastes -- Biodegradation Biomass chemicals UCTD Kuyler, Judi Determining the effect of micro-aeration on the anaerobic digestion of lignocellulosic biomass |
| title | Determining the effect of micro-aeration on the anaerobic digestion of lignocellulosic biomass |
| title_full | Determining the effect of micro-aeration on the anaerobic digestion of lignocellulosic biomass |
| title_fullStr | Determining the effect of micro-aeration on the anaerobic digestion of lignocellulosic biomass |
| title_full_unstemmed | Determining the effect of micro-aeration on the anaerobic digestion of lignocellulosic biomass |
| title_short | Determining the effect of micro-aeration on the anaerobic digestion of lignocellulosic biomass |
| title_sort | determining the effect of micro aeration on the anaerobic digestion of lignocellulosic biomass |
| topic | Lignocellulose as feed Sewage -- Purification -- Anaerobic treatment Agricultural wastes -- Biodegradation Biomass chemicals UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132229 |
| work_keys_str_mv | AT kuylerjudi determiningtheeffectofmicroaerationontheanaerobicdigestionoflignocellulosicbiomass |