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Enhancing Biogas Recovery from Anaerobic Co-digestion of Human Excreta and Food Waste using Response Surface Method and Biochar Additives
Ghana shares similar challenges with other developing nations regarding waste management and access to clean energy. Fortunately,these two challenges are connected. A better waste management strategy would involve converting the organic waste fractions into biogas. Nevertheless, a thorough study of...
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| Format: | Thesis |
| Language: | en_US |
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KNUST
2024
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| _version_ | 1869483608020877312 |
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| access_status_str | Open Access |
| author | Peprah, Blissbern Owusu |
| author_browse | Peprah, Blissbern Owusu |
| author_facet | Peprah, Blissbern Owusu |
| author_sort | Peprah, Blissbern Owusu |
| collection | Thesis |
| description | Ghana shares similar challenges with other developing nations regarding waste management and access to clean energy. Fortunately,these two challenges are connected. A better waste management strategy would involve converting the organic waste fractions into biogas. Nevertheless, a thorough study of the physico-chemical characteristics of the feed stocks used in the anaerobic digestion process is essential to maximize the energy potential. Consequently, the first phase of this study examined the physical
chemical properties of some selected feedstocks, namely, human excrement (HE), food leftovers (FLO), kitchen residues (KR), and cowdung (CD) of Ghanaian origin using APHA standards and equipment. Results of volatile-to-total solid ratios (VS/TS), 0.97±0.001, 0.89±0.001, and 0.85±0.001 for HE, FLO,KR and CD, respectively, showed that all feed stocks had high biodegradable content.
though thecarbon-to-nitrogen(C/N)ratiosforFLO(22.14±0.26),KR(23.34±0.25)
and CD(26.19±0.47)werewithintheoptimalrange,thatofHE(8.29±0.09)was
significantly low.Withameanalkalinityof1219.67±1.53,630.00±0.58,590.00±
2.08 and15,730.00±6.00mgCaCO3 eq./L forHE,FLO,KRandCDrespectively,
it wasobservedthatonlyCDhastheoptimalalkalinityvalueforanaerobicdiges-
tion. Thisbroughtintoperspectivetheneedforco-digestion.Thesecondphaseof
the study,therefore,soughttoprovethehypothesisthatanaerobicco-digestionofHE,
FLO andKRcouldgeneratemorebiogaswhileremainingstableifpositivesynergis-
tic effectsareachieved.Arandomizedternarymixturedesignandaresponsesurface
approach wereusedtoascertaintherelationshipbetweensubstratemixture,biogas
yield, methaneyield,andsynergy.ThefindingsrevealedthatR9(78.8%HE:11.8%
FLO:9.4 %KR)hadthehighestmethaneyieldof764.79mLCH4/gVS andasyner-
gistic indexof3.26.Additionally,the3Dresponsesurfaceplotsshowedimportant
and sharedinteractionsbetweenHE,FLO,andKRwherebythepredictedresponses
increased withincreasingHEandKRfractionsanddecreasedwithincreasingFLO
fractions inthesubstratemixtures.Inthethirdphaseofthestudy,theexperimental
cumulativemethaneyieldfromtheoptimumanaerobicco-digestionratio,R9,wasfit-
ted tofivekineticmodelsandtheconemodelhadthebestfitrecordingan R2 value
of 0.9909.Finally,theeffectsofcoconutshell(CCN)andpalmkernelshell(PKN)
biochar dosages(3g,6gand10g)ontheanaerobicco-digestionofHE,FLOand
KR wereinvestigatedusingbatchmesophilicexperiments.Theresultsshoweddif-
ferences inthepeakoccurrencetimesandmethaneyieldswiththebiochar-amended
treatments peakingearlierthanthecontroltreatment.Further,methaneyield(456.25
mLCH4/gVS) increasedwhen3gofCCNbiocharwasused,depictinga23.31%in-
crease comparedtothecontrol(SM=370.03mLCH4/gVS). However,toohighCCN
biochar dosagesof6gand10grestrictedmethaneproductionduetoapotentialstress
on theanaerobicdigestionprocessbroughtonbytheaccumulationof H2 competitors
of methanogensthatmighthaveclonedontoexcessbiocharandweakeneditsDIET
benefit formethanogenesis.Furthermore,themethaneyieldwas368.69mLCH4/gVS,
similar tothatofthecontrol(SM)when3gofPKNshellbiocharwasaddedtothe
mixture offeedstocks.Nonetheless,methaneyieldincreasedby10.83%whenthe
dosage ofPKNshellbiocharusedwasincreasedto6g.Conversely,PKN10gobserved
a decreaseincumulativemethaneyield.Theobservedresultsindicatethatmicrobial
activityandkineticscouldpossiblyberestrictedbyexcessivedosageofbiochar.This
could beattributedtothepossibleadsorptionofvolatilefattyacids(VFAs)sincethe
adsorption mechanismofbiocharisnotselective.Hence,higheramountsofadded
biochar maynotnecessarilycorrespondtohigherdigestionefficiency. |
| format | Thesis |
| id | oai:ir.knust.edu.gh:123456789/15690 |
| institution | KNUST (Ghana) |
| language | en_US |
| last_indexed | 2026-07-01T04:01:41.912Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from KNUSTSpace — Kwame Nkrumah University of Science & Technology (Ghana) |
| publishDate | 2024 |
| publishDateRange | 2024 |
| publishDateSort | 2024 |
| publisher | KNUST |
| publisherStr | KNUST |
| record_format | dspace |
| source_str | KNUSTSpace — Kwame Nkrumah University of Science & Technology (Ghana) |
| spelling | oai:ir.knust.edu.gh:123456789/15690 Enhancing Biogas Recovery from Anaerobic Co-digestion of Human Excreta and Food Waste using Response Surface Method and Biochar Additives Peprah, Blissbern Owusu Ghana shares similar challenges with other developing nations regarding waste management and access to clean energy. Fortunately,these two challenges are connected. A better waste management strategy would involve converting the organic waste fractions into biogas. Nevertheless, a thorough study of the physico-chemical characteristics of the feed stocks used in the anaerobic digestion process is essential to maximize the energy potential. Consequently, the first phase of this study examined the physical chemical properties of some selected feedstocks, namely, human excrement (HE), food leftovers (FLO), kitchen residues (KR), and cowdung (CD) of Ghanaian origin using APHA standards and equipment. Results of volatile-to-total solid ratios (VS/TS), 0.97±0.001, 0.89±0.001, and 0.85±0.001 for HE, FLO,KR and CD, respectively, showed that all feed stocks had high biodegradable content. though thecarbon-to-nitrogen(C/N)ratiosforFLO(22.14±0.26),KR(23.34±0.25) and CD(26.19±0.47)werewithintheoptimalrange,thatofHE(8.29±0.09)was significantly low.Withameanalkalinityof1219.67±1.53,630.00±0.58,590.00± 2.08 and15,730.00±6.00mgCaCO3 eq./L forHE,FLO,KRandCDrespectively, it wasobservedthatonlyCDhastheoptimalalkalinityvalueforanaerobicdiges- tion. Thisbroughtintoperspectivetheneedforco-digestion.Thesecondphaseof the study,therefore,soughttoprovethehypothesisthatanaerobicco-digestionofHE, FLO andKRcouldgeneratemorebiogaswhileremainingstableifpositivesynergis- tic effectsareachieved.Arandomizedternarymixturedesignandaresponsesurface approach wereusedtoascertaintherelationshipbetweensubstratemixture,biogas yield, methaneyield,andsynergy.ThefindingsrevealedthatR9(78.8%HE:11.8% FLO:9.4 %KR)hadthehighestmethaneyieldof764.79mLCH4/gVS andasyner- gistic indexof3.26.Additionally,the3Dresponsesurfaceplotsshowedimportant and sharedinteractionsbetweenHE,FLO,andKRwherebythepredictedresponses increased withincreasingHEandKRfractionsanddecreasedwithincreasingFLO fractions inthesubstratemixtures.Inthethirdphaseofthestudy,theexperimental cumulativemethaneyieldfromtheoptimumanaerobicco-digestionratio,R9,wasfit- ted tofivekineticmodelsandtheconemodelhadthebestfitrecordingan R2 value of 0.9909.Finally,theeffectsofcoconutshell(CCN)andpalmkernelshell(PKN) biochar dosages(3g,6gand10g)ontheanaerobicco-digestionofHE,FLOand KR wereinvestigatedusingbatchmesophilicexperiments.Theresultsshoweddif- ferences inthepeakoccurrencetimesandmethaneyieldswiththebiochar-amended treatments peakingearlierthanthecontroltreatment.Further,methaneyield(456.25 mLCH4/gVS) increasedwhen3gofCCNbiocharwasused,depictinga23.31%in- crease comparedtothecontrol(SM=370.03mLCH4/gVS). However,toohighCCN biochar dosagesof6gand10grestrictedmethaneproductionduetoapotentialstress on theanaerobicdigestionprocessbroughtonbytheaccumulationof H2 competitors of methanogensthatmighthaveclonedontoexcessbiocharandweakeneditsDIET benefit formethanogenesis.Furthermore,themethaneyieldwas368.69mLCH4/gVS, similar tothatofthecontrol(SM)when3gofPKNshellbiocharwasaddedtothe mixture offeedstocks.Nonetheless,methaneyieldincreasedby10.83%whenthe dosage ofPKNshellbiocharusedwasincreasedto6g.Conversely,PKN10gobserved a decreaseincumulativemethaneyield.Theobservedresultsindicatethatmicrobial activityandkineticscouldpossiblyberestrictedbyexcessivedosageofbiochar.This could beattributedtothepossibleadsorptionofvolatilefattyacids(VFAs)sincethe adsorption mechanismofbiocharisnotselective.Hence,higheramountsofadded biochar maynotnecessarilycorrespondtohigherdigestionefficiency. 2024-04-17T14:15:13Z 2024-04-17T14:15:13Z 2023-09 Thesis https://ir.knust.edu.gh/handle/123456789/15690 en_US application/pdf KNUST |
| spellingShingle | Peprah, Blissbern Owusu Enhancing Biogas Recovery from Anaerobic Co-digestion of Human Excreta and Food Waste using Response Surface Method and Biochar Additives |
| title | Enhancing Biogas Recovery from Anaerobic Co-digestion of Human Excreta and Food Waste using Response Surface Method and Biochar Additives |
| title_full | Enhancing Biogas Recovery from Anaerobic Co-digestion of Human Excreta and Food Waste using Response Surface Method and Biochar Additives |
| title_fullStr | Enhancing Biogas Recovery from Anaerobic Co-digestion of Human Excreta and Food Waste using Response Surface Method and Biochar Additives |
| title_full_unstemmed | Enhancing Biogas Recovery from Anaerobic Co-digestion of Human Excreta and Food Waste using Response Surface Method and Biochar Additives |
| title_short | Enhancing Biogas Recovery from Anaerobic Co-digestion of Human Excreta and Food Waste using Response Surface Method and Biochar Additives |
| title_sort | enhancing biogas recovery from anaerobic co digestion of human excreta and food waste using response surface method and biochar additives |
| url | https://ir.knust.edu.gh/handle/123456789/15690 |
| work_keys_str_mv | AT peprahblissbernowusu enhancingbiogasrecoveryfromanaerobiccodigestionofhumanexcretaandfoodwasteusingresponsesurfacemethodandbiocharadditives |