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Biogas-fuelled aqua-ammonia absorption refrigeration as a means of reducing post-harvest losses in rural Sub-Saharan Africa
Thesis (MEng)--Stellenbosch University, 2022.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2022
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| _version_ | 1867613848756813824 |
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| access_status_str | Open Access |
| author | Wentzel, Louis Frans Jacobus |
| author2 | Van Rensburg, Eugene |
| author_browse | Van Rensburg, Eugene Wentzel, Louis Frans Jacobus |
| author_facet | Van Rensburg, Eugene Wentzel, Louis Frans Jacobus |
| author_sort | Wentzel, Louis Frans Jacobus |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2022. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/124875 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:42:40.195Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/124875 Biogas-fuelled aqua-ammonia absorption refrigeration as a means of reducing post-harvest losses in rural Sub-Saharan Africa Wentzel, Louis Frans Jacobus Van Rensburg, Eugene Görgens, Johann Ferdinand Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Process Engineering. Sewage -- Purification -- Anaerobic treatment Aqua-ammonia absorption refrigeration Biogas Silage UCTD Thesis (MEng)--Stellenbosch University, 2022. ENGLISH SUMMARY: Post-harvest losses are particularly prevalent in the food value chains of Sub-Saharan Africa (SSA), characterised by poverty, food insecurity and poor infrastructure. This project combined anaerobic digestion (AD) and absorption refrigeration (AR) to provide off-grid cold storage in SSA and focussed on the artisanal fisheries of Lake Victoria as an example of the utility of this technology. The main objective of this study was to prototype a biogas-fuelled aqua-ammonia absorption refrigerator to determine its biogas consumption rate and thermodynamic performance. A pipe injection burner was designed to convert a 42 L aqua-ammonia absorption refrigerator to run on a mixture of 59.2% methane and 40.8% carbon dioxide, which simulated a standard biogas mixture. This prototype was used as proof of concept and achieved cold storage temperatures that decreased from 6.4 to -19 ˚C as the normalised biogas flowrate increased from 0.51 to 0.74 m3 day-1. The thermodynamic performance of this prototype informed a novel empirical model that determines the biogas consumption rates of larger aqua-ammonia absorption refrigerators at various temperatures. This model found that a 250 L aqua-ammonia absorption refrigerator operating at sub-zero temperatures consumes 11 to 13 times the amount of biogas consumed by an electric 254 L vapour compression refrigerator connected to a biogas-fuelled combined heat and power (CHP) system. Therefore, whereas vapour compression refrigeration is more energy efficient, AR is more practical in the context of rural SSA, because it has no moving parts and does not require access to electricity. Two biochemical methane potential (BMP) assays with two objectives were performed to determine the potential biogas production rates of biomass available in the Lake Victoria region. The first BMP assay considered the co-digestion of fish effluent, blended with cow manure, maize stover, water hyacinth and reeds, respectively, to investigate whether co-digestion achieves statistically significant synergetic effects that increase the combined BMP and/or digestion rate of the combined biomass due to an improved nutrient balance. It was found that co-digestion did not achieve statistically significant synergetic effects at a 95% confidence level for any of the biomass co-digested with fish effluent. The second BMP assay considered the ensilage of maize stover, water hyacinth and reeds as a biological pre-treatment method that may increase the BMP and/or digestion rate of these lignocellulose because hydrolysis takes place during ensilage. There were discrepancies in literature where some workers reported significant increases in the BMP of ensilaged lignocellulose, while others reported significant decreases. An alternative protocol was developed to correct these overestimations, which showed that silage BMPs were overestimated when the standard BMP protocol was used. The final objective of this study was to combine the results from the biogas-fuelled aqua-ammonia absorption refrigerator and the BMP assays to model large-scale AD-AR dual systems, which demonstrated the potential of this dual system as a robust off-grid cold preservation technology at the nexus of water, energy and food in the context of small holder farming in rural SSA. AFRIKAANS OPSOMMING: Na-oesverlieste is veral algemeen in die voedselwaardekettings van Sub-Sahara Afrika (SSA) wat gekenmerk is deur armoede, voedselonsekerheid en swak infrastruktuur. Hierdie projek het anaërobiese vertering (AnV) en absorpsieverkoeling (AbV) gekombineer vir verkoeling in afgeleë plekke in SSA en het gefokus op Victoriameer se visserye as voorbeeld van die nut van hierdie tegnologie. Die hoofdoelwit was om ‘n prototipe van ‘n biogas-aangedrewe akwa-ammoniak absorpsie-yskas te bou en te gebruik om die biogasverbruikstempo en termodienamiese werkverrigting te bepaal. ‘n Pypinspuitbrander is ontwerp om ‘n 42 L akwa-ammoniak absorpsie-yskas op ‘n gasmengsel wat bestaan uit 59.2% metaan en 40.8% koolstofdioksied, wat ‘n standaard biogasmengsel gesimuleer het, te laat hardloop. Hierdie prototipe is as bewys van konsep gebruik en het temperature van 6.4 tot 19 ˚C behaal soos die genormaliseerde biogasvloeitempo van 0.51 tot 0.74 m3 dag-1 toegeneem het. Die termodinamiese werkverrigting van hierdie prototipe was gebruik om ‘n nuwe empiriese model van die biogasverbruikstempo van groter akwa-ammoniak absorpsie yskaste by verskillende temperature te formuleer. Hierdie model het gewys dat ‘n 250 L akwa-ammoniak absorpsie-yskas 11 tot 13 keer die hoeveelheid biogas gebruik wat deur ‘n elektriese 254 L dampkompressie-yskas wat aan ‘n biogas-aangedrewe gekombineerde hitte en krag stelsel gekoppel is, gebruik word. Alhoewel dampkompressie-yskaste dus meer energiedoeltreffend is, is AbV meer prakties in die konteks van afgeleë SSA omdat dit geen bewegende dele het nie en omdat dit nie toegang tot elektrisiteit kort nie. Twee biochemiese metaanpotentiaal (BMP)-toetse met twee verskillende doelwitte is uitgevoer om die biogasproduksietempo potensiaal van biomassa wat in die Victoriameer-streek beskikbaar is te bepaal. Die eerste BMP-toets het die vertering van visafloopwater wat onderskeidelik gemeng is met beesmis, mielies, waterhiasint en riete om te sien of medevertering statities betekenisvolle sinergetiese effekte bereik wat die BMP van die gekombineerde biomassa en/of verteringstempo verhoog as gevolg van ‘n verbeterde voedingstofbalans. Daar is gevind dat medevertering nie statisties betekenisvolle sinergetiese effekte teen ‘n 95% vertrouensvlak bereik het vir enige van die biomassa wat met visafloopwater verteer is nie. Die tweede BMP-toets het die inkuiling van mielies, waterhiasint en riete as ‘n biologiese voorbehandelingsmetode beskou wat die BMP en/of verteringstempo van hierdie lignosellulose kan verhoog omdat hidrolise tydens inkuiling plaasvind. Daar was teenstrydighede in literatuur waar sommige navorsers statisties betekenisvolle toenames in die BMPs van ingekuilde lignosellulose gerapporteer het, terwyl ander beduidende afnames gerapporteer het. ‘n Alternatiewe metode is ontwikkel om hierdie oorskattings reg te stel, wat getoon het dat kuilvoer BMPs oorskat word wanneer die standaard BMP protokol gevolg word. Die finale doel van hierdie studie was om die resultate van die biogas-aangedrewe akwa-ammoniak absorpsie-yskas en die BMP-toetse te kombineer om grootskaalse AnV-AbV-stelsels te modelleer, wat die potensiaal van hierdie robuuste tegnologie as ‘n verkoelingstegnologie in afgeleë plekke demonstreer. Hierdie tegnologie verbind water, energie en voedsel in die konteks van klein boerderye in SSA. Masters 2022-03-10T08:12:55Z 2022-04-29T09:38:43Z 2022-03-10T08:12:55Z 2022-04-29T09:38:43Z 2022-04 Thesis http://hdl.handle.net/10019.1/124875 en_ZA Stellenbosch University 232 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Sewage -- Purification -- Anaerobic treatment Aqua-ammonia absorption refrigeration Biogas Silage UCTD Wentzel, Louis Frans Jacobus Biogas-fuelled aqua-ammonia absorption refrigeration as a means of reducing post-harvest losses in rural Sub-Saharan Africa |
| title | Biogas-fuelled aqua-ammonia absorption refrigeration as a means of reducing post-harvest losses in rural Sub-Saharan Africa |
| title_full | Biogas-fuelled aqua-ammonia absorption refrigeration as a means of reducing post-harvest losses in rural Sub-Saharan Africa |
| title_fullStr | Biogas-fuelled aqua-ammonia absorption refrigeration as a means of reducing post-harvest losses in rural Sub-Saharan Africa |
| title_full_unstemmed | Biogas-fuelled aqua-ammonia absorption refrigeration as a means of reducing post-harvest losses in rural Sub-Saharan Africa |
| title_short | Biogas-fuelled aqua-ammonia absorption refrigeration as a means of reducing post-harvest losses in rural Sub-Saharan Africa |
| title_sort | biogas fuelled aqua ammonia absorption refrigeration as a means of reducing post harvest losses in rural sub saharan africa |
| topic | Sewage -- Purification -- Anaerobic treatment Aqua-ammonia absorption refrigeration Biogas Silage UCTD |
| url | http://hdl.handle.net/10019.1/124875 |
| work_keys_str_mv | AT wentzellouisfransjacobus biogasfuelledaquaammoniaabsorptionrefrigerationasameansofreducingpostharvestlossesinruralsubsaharanafrica |