Bioenergy Science and Technology

Permanent URI for this collectionhttps://etd.hu.edu.et/handle/123456789/49

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Start date: 2020

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    Investigating the Biogas Production Potential of Grass Hay Co-digested with Cattle Dung
    (Hawassa University College of Agriculture, 2022) Zerihun Desalegn Dana
    An alternative source of renewable energy can be offered from anaerobic digestion of organic materials since bio-methane has a potential in replacing fossil fuels in both heat and power generation, thus contributing to mitigate the emissions of greenhouse gases. For the reasonsjustified as easy availability, smooth digestibility, and easy technology acquisition, the anaerobic digesters in developing world mostly rely on cattle dung as feedstock. However, the declining trend of the cattle size holding at household levelcoupled with wastage of energy rich fodder (grass silage) when feeding out call for a bio-digester systems co-digestingcattle dung with grass silage. In this regard, co-digestion of the cattle dung with wastage of fodder could be an interesting remedy for meeting both the availability of sufficient biogas and waste management. In this study, biogas and methane yields of cattle dung alone, 50% cattle dung with 50% grass hay, and 75% cattle dung with 25% grass hay were measured and compared using in anaerobic batch digesters.The experiment was carried out in a laboratory scale batch assay at mesophilic temperature (37±2 o C) for 38 days, samples were characterized in terms of total solid (TS), volatile solid (VS), power of hydrogen (pH), total nitrogen and carbon to nitrogen ratio (C:N) as per the existing standards and biogas produced was characterized using biogas analyzer. From the dry matter of the substrate, specific biogas yields of 273.3, 318.6 and 296.4 mLN/g oDMwas obtained from cattle dung alone, 50% cattle dung with 50% grass hay, and 75% cattle dung with 25% grass hay respectively while specific methane yields were 165, 211 and 170.8 mLNCH4/goDMrespectively. Moreover, methane concentrations of 60, 66 and 58% were recorded for the above treatments.Therefore, optimum co-digestion of cattle dung with grass hay resulted inmore biogas and methane yields than mono digestion of cattle dung in terms of dry matter substrateand cattle dung can be co-digested with grass hay at dry matter ratio of 1:1 for yielding the highest biogas yields of 318.6mLN/goDM.
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    CHARACTERIZATION AND EVALUATION OF BANANA PSEUDO-STEMS FOR BIOETHANOL PRODUCTION
    (Hawassa University College of Agriculture, 2022) TEMESGEN AYELE ADE
    Bio-fuels like bioethanol originated from lignocellulosic biomasses are being investigated as potential substitutes for current high pollutant fuels obtained from conventional sources. Banana pseudo-stem is one of lignocellulosic biomass, which is generated from banana cultivation. This study was carried out to Characterize and Evaluate Banana Pseudo-stems for Bioethanol Production. For this study, Giant Cavendishii (M. acuminata), Dwarf Cavendishii (M. acuminata), and William-1 (M. ‘Williams hybrid’) banana pseudo-stems were used for investigation. In this study, chemical compositions of pseudo-stems (extractives, cellulose, hemicellulose, lignin, and ash) were determined through National Renewable Energy Laboratory (NREL) protocol. Bioethanol was also produced from each pseudo-stem through biochemical conversion method. The production method had four major processes; pseudo-stem pretreatment, hydrolysis, fermentation, and distillation. Some of the physicochemical properties of produced bioethanol (Viscosity, Density, Flash point, Alcohol concentration, and Calorific value) were tested. The functional group of the produced bioethanol was analyzed using Fourier Transform Infrared (FTIR) spectroscopy. And finally, bioethanol yield of each variety was determined depending on the concentration of produced bioethanol. Each laboratory experiments were conducted for triplicate. The data analysis of experimental result was done by using statistical analysis of variance (one way ANOVA), through statistical analysis software (SAS). The laboratory result of extractives, cellulose, hemicellulose, lignin, and ash content of the pseudo-stems were 27.25% - 31.15%, 30.11% - 36.14%, 19.32% - 23.83%, 8.81% - 9.30%, and 7.99% - 9.30%, respectively. And bioethanol yield of Giant Cavendishii, Dwarf Cavendishii, and William-1 pseudo-stem were 6.31%, 5.20%, and 4.00%, respectively. The statistical analysis software (SAS) output implied that the pseudo-stems of the three varieties have significantly different cellulose composition and bioethanol yield. As the result implied, pseudo-stem of giant cavendishii (M. acuminate) has the largest cellulose content and bioethanol yield followed by dwarf cavendishii (M. acuminata). Thus, giant cavendishii (M. acuminate) has relatively higher bioethanol potential. Therefore, giant cavendishii banana pseudo-stem is recommended to use as feedstock for bioethanol production.
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    INVESTIGATING THE BIOGAS PRODUCTION POTENTIAL OF COFFEE CHERRY PROCESSING WASTES CO-DIGESTED WITH ANIMAL MANURE
    (Hawassa University College of Agriculture, 2021) WOLDE MATHEWOS DELKERO
    As the human population is increasing from time to time, the energy demand also increasing in a similar fashion. To meet this energy demand, there is high dependence on traditional biomass and fossil fuel, which are major source of environmental degradation. On the other hand, agricultural and industrial wastes are becoming the sources of air and water pollution due to improper management in which otherwise can be used as a renewable energy sources. Biogas is a renewable alternative energy sources made from bio-wastes and has a huge potential for future energy security and environmental sustainability. In the present investigation a “batch feeding digester” was developed to evaluate the potential use of coffee cherries processing wastes: coffee husk, coffee pulp and their co-digestion with cow dung for biogas production at mesophilic conditions and to analyze the nutrient content of the bioslurry to be used as a bio-fertilizer. In advance of biogas production, feedstock quality parameters such as moisture content, total solid, Volatile solid and carbon to nitrogen ratio was determined using standard methods in order to check biodegradability of substrate and balance of nutrients in the substrate. The biogas production was conducted using laboratory digesters having a capacity of five liter with working volume of four liter, operated for about 35 days in incubator at a temperature of 37 0 C. One way analysis of variance (ANOVA) was performed to compare variations among treatments. The result showed that the values of feedstock quality parameters were within the acceptable range for biogas production. The amount of biogas produced from 1:1 coffee pulp with cow dung, coffee pulp, 1:1 coffee husk with cow dung, cow dung and 1:1 of coffee husk with cow dung and coffee husk with was 372.33 ± 5.0, 349.88 ± 2.65, 320.07 ± 3.54, 291.43 ± 5.07 and 268.55 ± 4.16 ml/g VS, respectively. The result indicates that 1:1 ratio of coffee pulp with cow dung produced higher amount of biogas than coffee pulp alone. Significant differences were observed in biogas production potentials between mono-digested and co-digested treatments at (P<0.05). The quality of biogas in terms of methane content was 60.0, 59.2, 58.4, 57.1, 52% respectively, for cow dung, coffee pulp with cow dung, coffee husk with cow dung, coffee pulp and coffee husk. This shows co-digestion improves biogas yield. Generally, the results encouraged the feasibility of the coffee husk, coffee pulp and their co-digestion with cow dung for biogas production in the study areas. Nitrogen, Phosphorous and potassium of bio-slurry were in the range of 1.8 - 2.25, 0.2-1.7 and 0.49-1.3% respectively. This showed that bio-slurry from all treatments had enough amounts of macronutrients that needed in bio- fertilizer.
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    EVALUATION OF SEDGE GRASS (S. tabernaemotani) FOR BIOETHANOL PRODUCTION
    (Hawassa University College of Agriculture, 2021) FREWEYNI HAILU
    Biofuel production from first generation biomasses, basically human food, might lead to problem of food crisis. Non-edible lignocellulosic biomass which is abundant with low production cost would be considered as an appropriate feedstock for ethanol production. Sedge grass (Schoenoplectus tabernaemontani) is one of environmental friendly non-edible lignocellulosic grasses.However; there are no reports on the use of sedge grass for bioethanol production. Therefore, this study was conducted to investigate the yield of total reducing sugar from sedge grass for ethanol production, with three levels of hydrolysis time (40, 60 and 80 min), three levels of H2SO4 concentration (1.5, 2.5 and 3.5%) and three levels of temperature (115, 125 and 135oC) designed in Complete Randomized Design (CRD) with three replications. The chemical compositions (extractives, cellulose, hemicellulose and lignin) of the plant were also determined by using National Renewable Energy Laboratory (NREL) protocol. The reducing sugar yield was determined by Benedict’s solution using spectrophotometer. Simple distillation was carried out to separate ethanol from water and the functional group of the produced ethanol was analyzed using Fourier Transform Infrared (FTIR).To estimate the ethanol yield, potassium dichromate method was used. As the result indicated, the content of hemicellulose, cellulose, lignin and extractives were 42%, 39.87%, 13.07% and 5.06%, respectively. The two-way interaction of treatments exhibited significant differences on total reducing sugar yield. Concerning the three-way interaction, highest total reducing sugar was produced when the feedstock was hydrolyzed at a temperature of 1250C for 60 min by 2.5% dilute H2SO4 solution. However, the lower percent of total reducing sugar yield (38.29%) was recorded from hydrolyzed sample at a temperature of 1350c for 80min using 3.5% dilute H2SO4 solution. Eventually, the highest ethanol yield (51.02%) was recorded from 49.83% of hydrolyzed sample reducing sugar fermented by F. oxysporum for 7 days fermentation. Therefore, sedge grass biomass is recommended as raw materials for bioethanol production, which is a promising alternative energy source against the depleting petroleum.