College of Engineering

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    Enhancing Biogas Recovery from Anaerobic Co-digestion of Human Excreta and Food Waste using Response Surface Method and Biochar Additives
    (KNUST, 2023-09) 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.
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    Towards Improved Quality and Performance of Cold-Mix Asphalts for Bituminous Pavement Maintenance in Ghana
    (KNUST, 2023-02) Boateng, Kwadwo Appiah
    Premature failure and poor performance of cold-mix asphalts (CMAs) used in pothole patching and sectional repairs on bituminous roads are very common in Ghana, and yet, for a long time, the problem has remained unaddressed while the material continues to be used. There is, therefore, the need to improve the quality of cold-mix asphalts used in the country in order to achieve a more successful and durable product in road maintenance. To this end, Ghana’s Ministry of Transportation (MOT) Standard Specification for Road and Bridge Works (2007) was reviewed alongside three foreign specifications on CMAs, namely, Asphalt Institute MS 19 (1997), Chevron USA Incorporated Procedure and Nikolaides Specification (1994), to establish possible commonalities and areas of deviations that could impact the field performance of the material. Also, samples from ready-to-use CMA stockpiles at six contractor sites across the country, and failed road patches were investigated. Further, a series of dense-graded cold-mix asphalts, with simplified material proportioning ratios, were proposed and investigated for adoption and use. Lastly, potential improvement in CMA properties, using montmorillonite nanoclay filler, was explored. It was established that Ghana’s MOT Specification lacked specificity and clarity on the subject of CMAs. In the case of the other Specifications, though variations in mixture design and testing protocols existed, there appeared to be a general consensus on the use of different aggregate gradation structures that lead to high field performance. The asphalt contents of the cold-mix asphalt samples taken from the field tended to range between 3% and 6%, with emulsion mixes having the lower values. In addition, the aggregate structures of the mixes were poor, consisted essentially of single-size aggregates with uniformity coefficient values that ranged between 1 and 4. Some specimens compacted in the laboratory disintegrated during conditioning for stability and flow test, suggesting a lack of stickiness and cohesion within the compacted matrix. It, therefore, appears that the early failures characterizing cold-mix asphalts used in maintenance works in the country could be due principally to inadequate aggregate structure and low binder content of the mixes. For improved cold-mix quality, five aggregate gradation blends that meet GHA dense grading requirements, together with the corresponding emulsionto- aggregate ratio, for easy material batching in the field, have been proposed. Montmorillonite nanoclay used as filler increased the optimum bitumen content and improved the stability of the cold-mixes but resulted in significantly high flows. This suggests that their use in cold-mix asphalts has the potential to induce plastic behaviour and render the mixes more rut-susceptible, especially at high temperatures.
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    Impact of climate change and land use/land cover change on soil fertility in the cotton Basins of Côte d’Ivoire
    (KNUST, 2023-07) Kone, Ismail
    The study assessed the impact of alterations in land use and land cover, as well as fluctuations in climate patterns, on soil fertility within the cotton-producing area of Côte d'Ivoire. The study entails evaluating how farmers perceive and cope with climate change, determining the current state of soil fertility, evaluating land suitability and management options for cotton production, and simulating the way the land in the region will be utilized and the vegetation that will cover it in the future. To evaluate smallholder farmers' perceptions of climate change adaptation options, a structured questionnaire with closed questions was used to collect data from 355 farmers located in the cotton basin of Côte d'Ivoire. The findings revealed that most respondents acknowledged the existence of climate change in the area and its detrimental impact on farmers' livelihoods, leading them to adopt coping mechanisms. To determine the status of soil fertility, the study analyzed 64 soil samples collected in 2013 and 2021 in the same fields where cotton was grown. Specifically, the analysis focused on the physical and chemical properties of the topsoil layer, ranging from 0 to 20 centimeters in depth. Between 2013 and 2021, the chemical properties of the soil (concentrations of Ca2+, Mg2+, K+, and Base Saturation (BS)) saw only a slight improvement, leaving soil fertility as a significant constraint on cotton production. Targeted, site-specific soil management is necessary to address this issue. The study evaluated soil suitability for cotton cultivation in eight villages in the Côte d'Ivoire cotton basin by characterizing two representative soil profiles (0-100 cm) per village which were described in terms of their soil chemical and physical properties. The soils were "moderately suitable" (S2) or "marginally suitable" (S3) due to poor chemical properties, such as the Sum of Basic Cations (SBC) and organic carbon (OC). The study also used Landsat images to track changes in land use and land cover (LULC) between 1998 and 2020 and predicted future LULC for 2035 and 2063 using the TerrSet software and the CA-Markov chain. From 1998 to 2020, there was a reduction in the share of forestland and Savannah with each zone decreased by -11.09 % and -21.56 % respectively at Korhogo, -14.09 % and -1.78 % respectively at Ferkessedougou, -0.33 %, and -14.8 % respectively at Boundiali, and -6.9 % and -31.33 % respectively at Mankono, while water body, cropland, and settlement/bare land increased. From 1998 to 2035, the results revealed that the share of cropland and, settlement/bare land within the department continue to increase in the study area by 4.54 % and 28.2 %, respectively at Korhogo, 5.34 %, and 10.45 % at Ferkessedougou, 14.95 %, and 0.01 % at Boundiali, and 1.12 %, and 37.04 % in the zone at Mankono. From 1998 to 2063, the results revealed that the share of cropland and, settlement/bear with the department's land could continue to increase. The findings of this study could aid in improving and optimizing soil management practices within the cotton-producing region of Côte d'Ivoire.
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    Crops-Livestock Integration as a Resilience Strategy to Climate Change in Burkina Faso
    (2023-07) Sanou, Charles Lamoussa
    This study titled addressed a topical issue of climate change and its impacts on farmers' livelihoods and the role that an integrated crop-livestock system can play in building resilient farmers and agricultural systems. The research first of all analysed historical climate (rainfall, minimum and maximum temperature) trends across three climatic zones Sudan (Dano), Sudan-Sahel (Niou) and Sahel (Dori)) at annual, seasonal and decadal scales. Climates indices computation was done using the package ClimPACT2 GUI in R software. Annual and seasonal climate were compared using the independent t-test. Decadal climate indices were subjected to a Principal Component Analysis (PCA). The research also analysed the susceptibility or sensibility of crop production and livestock health to climate change. Thirdly, the research developed and/or updated measurement tool known as Crop-Livestock Integration (CLI) indicators for a holistic characterisation of integrated croplivestock system. These indicators were developed based on the information from 589 farmers’ households and secondary data. Above ground, data were collected from 4,733 trees over a total land area of 243.2 ha (80.1 ha, 78.8 ha and 84.3 ha in Sudan, Sudan-Sahel and Sahel zones, respectively). Due to the Sahel zone's insecurity, soil data could be collected only within Sudan and Sudan-Sahel zones. In total, 120 composite soil samples were collected for this purpose and 240 other samples for soil bulk density determination. Results revealed changes in climate conditions, more pronounced in temperature variations than in rainfall. In the Sudan-Sahel and Sahel zones, a re-wetting trends was observed over the last decade supporting the re-greening hypothesis of the Sahel. Despite some positive effects of the climate indices, crop failure was the major impact of climate pejoration across iv zones. Similarly, livestock health was majorly negatively affected by climate deterioration though the resurgence of diseases due to climate change. Climate indices could explain 23.0 - 50.2 % of the variations in crop yield and an increased cases of livestock diseases occurrence by 1-9.4 units due to the deterioration in climate conditions across climatic zones. Changes in climatic conditions may also induce microbial proliferation and host susceptibility to result in the emergence, redistribution, and changes in the incidence and intensity of pest infestations. The study concluded that crop-livestock integration is underperforming in Burkina Faso and can be improved. Majority farmers (91.6 %) in the Sudan-Sahel zone are practising full crop-livestock integration, unlike the Sahel (62.3%) and Sudan (48.2%) zones. However, only 14.8%, 10.5% and 5.1 % showed the effectiveness of integration in the Sudan-Sahel, Sahel and Sudan zones, respectively. CLI was comparatively more effective in Sudan-Sahel (65.9±32.0 %) than Sahel (44.9±29.5 %) and Sudan zones (35.6±35.0 %). Integration indicators were significantly associated with farm emissions, productivity, biodiversity and soils nutrients. CLI is also a tree-based system with high sequestration potential that could significantly counterbalance the whole system emissions. However, the coverage of fodder needs is negatively associated with soils nutrients content indicating field nutrient mining if an appropriate scheme of nutrient return to the soils as manure is not set. An adequate combination of CLI components offers an opportunity to build resilient farming systems in Burkina Faso to adapt to the changing climate.
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    Adoption and Effects of Climate Change Adaptation, and Land Use Decision of Smallholders Farmers in the Saline Area of Sine-Saloum, Fimela Senegal
    (2023-07) Thiam, Habibatou Ibrahima
    Soil salinity expansion is one of the most severe land degradation issues confronting farmers in Senegal, particularly in coastal areas such as Fimela. With sea level rise, temperature rise, and rainfall decrease, soil salinity is increasing significantly. It has a negative impact on crop yields and farmers' livelihoods. Farmers developed land use adaptation strategies to deal with soil salinity. Nonetheless, despite adaptations, some farmers continue to complain about the negative impact of soil salinity on their outcomes. Then, this study investigates farmers' adaptation, the different factors that influence it, its implications for smallholder farmers' livelihoods, and farmers' perception of soil salinity and its impact. Data from face-to-face interviews of 288 households using the Krejci and Morgan’s formula and GPS coordinates of households and each of their farms was collected. An agent-based model was used to understand land use adaptation to soil salinity expansion by considering farmers' perceptions of soil salinity expansion under climate change for simulation. A sub-model of household decisions, crop yield, and perception of soil salinity was developed and incorporated into the model. Three scenarios were considered to simulate the interaction between household agents and landscape agents over 25 years. Farmers' adoption is influenced by their assets and sociopsychological factors like threat assessment, coping assessment, and subjective norms. Farmers in Fimela do not have maladaptation thinking that may break their willingness to adopt strategies to cope with soil salinity. The ESR model shows that farmers' adoption of strategies to cope with soil salinity has a positive impact on groundnut yields and a negative influence on food security but has no significant effect on their millet yields. These findings have been validated by the simulation results, which show that the yield difference between farmers who perceive soil salinity expansion and those who do not is significant for groundnut but not millet over 25 years. As a result, it is critical to base policies in combating soil salinity effects on providing better methods of soil salinity adaptation strategies through scientific research. Policies should support a few pilot farmers in these precise and effective strategies to trigger other farmers to follow through the village and social influence by the farmer-to-farmer approach to enable farmers access and appropriation of these new methods.