School of Chemical and Bio Engineering

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    Adaptive Control Design for a MIMO Chemical Reactor
    (Addis Ababa University, 2004-07) Yimam, Abubeker; Venkatanarasaiah, D. (PhD)
    The major disadvantage of non-adaptive control systems is that these control systems cannot cope with fluctuation in the parameters of the process. One solution to this problem is to use high levels of feedback gain to decrease the sensitivity of the control system. However high gain controllers have two major problems: large signal magnitude and closed loop instability. The solution to this problem is to develop a control system that adapts to changes in the process. This paper presents the design of adaptive controller to a MIMO chemical reactor. The proposed adaptive controller is tested by using Math lab Simulink program and its performance is compared to a conventional controller for a different situation. The paper demonstrated that while the adaptive controller exhibits superior performance in the presence of noise the convergence time is typically large and there is a large overshoot. To resolve these problems of adaptive controller, the proposed controller is redesigned by modifying the adaptation law. And the results show a significant improvement in the performance of the adaptive controller without excessive increase in the adaptation rate. life of the low and middle income inner-city residents of Addis Ababa. Financial, institutional and legal problems are also seen as the major problems that hinder the implementation of LDPs in Addis Ababa
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    The Utilization of Indigenous Coal as Energy Substitute in Cement Industry
    (Addis Ababa University, 2004-08) Dejene, Yoseph; Kaba, Tassisa (PhD)
    Ethiopia spends million of dollars to meet its energy requirement, it is estimated around 20-30 million dollars is spent for the purchase of furnace oil for cement sectors only. In order to change the country’s economic situation and to come-out of poverty it is necessary to develop and utilize the country’s energy potential. For the reason of fuel economy cement plants all over the world are switching over from fuel oil or gas to coal for their kiln operation. Ethiopia has discovered large potential low grade coals at different areas. The development and the utilization of this indigenous coal as an energy source for all energy consuming sectors will be a major issue in this country in near future. The study aims to determine the potential use of one of the indigenous coal as a substitute in place of furnace oil in cement industry. Results from the analysis and comparisons of Yayu coal quality revealed the possibility of using Indigenous coal in place of furnace oil up to a certain percent. Based on the results the study attempts to select the equipments required if Yayu coal is replaced in place of fuel oil in Mugher Cement Enterprise. Substantial investment for additional facilities and equipments are required, and as a consequent considerable saving in production cost in addition to the reduction of foreign currency can be achieved through the switch over to indigenous coal. Additionally the study revealed air pollution, spontaneous coal fires and coal dust explosion are the major concerns of cement plant if this indigenous coal is used in place of furnace oil. In view of this the study recommended cement plants to see this alternative source of energy and to identify their concerns as soon as possible.
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    Cleaner Production Options for Solid Waste Management in the Leather Industry
    (Addis Ababa University, 2005-01) Ayalew, Andualem; W/yes, Belay (PhD)
    The leather industry is characterized as an industry that uses moderately large types and quantities of chemicals and water. The wastes generated in tannery processes include wastewater effluent, solid waste, and hazardous waste. These wastes create pollution problems in the environment. Most leather industries in Ethiopia discharge wastes into the environment prior to any proper treatment. An alternative approach to this is to eliminate or reduce the problem at the source using Cleaner Production (CP) approach. In this paper, a study is performed at Addis Ababa Tannery Sh.Co.(AAT) by implementing CP Methodologies. The solid waste inventory of the factory has been carried out. The major problems have been identified. The possible CP options for the existing problems are also suggested. Technical and economic aspects of the best three CP options have been evaluated. Result of the study indicates that the implementation of the suggested CP options gives significant benefit for the factory.
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    Modeling Chemical Engineering Processes Using Artificial Neural Networks
    (Addis Ababa University, 2005-01) Ambaw, Alemayehu; Assefa, Berhanu (PhD); Tefera, Nurelegne (PhD)
    In this thesis the application of feed forward type artificial neural networks to model chemical engineering processes are demonstrated with reference to five different problems. Neural network models are constructed and employed to predict vapor-liquid equilibrium (VLE) data of twelve different binary systems having different chemical structures and solution types (azeotrope-nonazeotrope) in various conditions (isothermal or isobaric). It is observed that the data found by neural network model gives an excellent agreement with the experimental data. In fact the neural network model can be treated as a powerful means for VLE data prediction in a fast and reliable way. This study has confirmed the feasibility of using a neural network to capture the nonlinear and interacting relationships between the moisture content and different drying conditions of potato. Simulating time series temperature profiles of adiabatic batch reactor has also investigated. Neural network trained with a limited number of experimental data were capable of predicting fresh data that were not used to train the network. The results obtained in using the developed models are physically sound as expected from experience. Simulating a human operator controlling a chemical plant is also a good instance where the advantage of using artificial neural networks is demonstrated in the thesis. This thesis also describes the use of multilayer feed forward neural networks as a CO2 analyzer. It was proved that MLP-type network of a relatively simple structure made it possible to predict the CO2 effluent from a furnace. Taking in to account the difficulties in experimental conditions, complicated measurements and unavoidable errors of devices used, limit the precision of laboratory measurement results. The accuracy of the results generated by the developed neural network models may be considered satisfactory for engineering calculations.
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    Intrusion Detection System Using Visualization and Integration Technique
    (Addis Ababa University, 2006-08) Denboba, Sisay; Raimond, Kumudha (PhD)
    Intrusion detection is an area of ever increasing importance. Currently existing Intrusion Detection Systems (IDS) lack visualization and false alarms detection capabilities. Researchers have proposed integrated systems which may reduce the percentage of false alarms. This work addresses the above stated problems by integrating Self-Organized Map (SOM) with Genetic Algorithm (GA) so as to minimize the false alarms and also to provide visualization capability to the new IDS. SOM is an unsupervised Artificial Neural Network (ANN) learning algorithm that attempts to visualize a large dataset in compact representation. GA is an evolutionary computing type of artificial intelligence algorithm, which is better for optimization, feature selection and clustering problems. The performance of the model is measured using Knowledge Discovery and Data Mining (KDD) Cup 99 dataset, which was prepared for The Third International Knowledge Discovery and Data Mining (DM) Tools Competition for researchers who work on intrusion detection. The work also includes GA based feature selection to further improve the performance of the model. The result shows 94.3 % of intrusion detection rate with 2.93% of false alarm rate.
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    Selection of Clay Adsorbents and Determination of The Optimum Condition for Defluoridation of Ground Water in Rift Valley Region
    (Addis Ababa University, 2007-01) Hassen, Ahmedin; Assefa, Berhanu (PhD); Tefera, Nurelegne (PhD)
    People in several regions of the Rift Valley of Ethiopia are suffering from skeletal and non-skeletal fluorosis as result of consuming water containing excessive fluoride. Defluoridation of drinking water using variety of material has been suggested by different researchers. This study assesses the fluoride adsorption characteristics of clays collected from different areas in Ethiopia. Bombawoha clay, Combolcha clay and Muger clay 2 were found to have the better potential as fluoride adsorbents. The effect of contact time, amount of adsorbent dose, pH, particle size, heat treatment of adsorbent and initial concentration of fluoride was investigated. The adsorption was rapid during the first one hour. The adsorption efficiency of fluoride was increased with adsorbent dosage. The defluoridation capacity was appreciable with in acidic pH range. Clay adsorbents treated in the range between 400 to 600oC gave better fluoride removal. The fluoride adsorption efficiency depends directly with initial fluoride concentration. The adsorption data were well fitted to the Langmuir isotherm model with adsorption capacity of 0.136, 0.168, and 0.191 for Bombawoha clay, Combolcha clay and Muger clay 2 respectively. Laboratory scale column were conducted and showed good removal of fluoride. At breakthrough the three clay samples Bombawoha clay, Combolcha clay and Muger clay 2 showed 0.1248, 0.235, 0.239 mg/g of adsorption capacity, 1.64, 1.1, 1.02 mg/L of residual fluoride and 300, 500, 500 mL of breakthrough volume respectively.
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    Effect of Low Temperature Preservation on The Physicochemical and Microbiological Qualitieis of Selected Fish Species of Lake Ziway
    (Addis Ababa University, 2007-06) Melaku, Mekonnen; Admassu, Shimelis(PhD)
    With the purpose of determining the effect of frozen storage on quality of fish fillet and evaluating the existing low temperature preservation technique in the case of Fish Production and Marketing Enterprise, samples from the same lot of commercially harvested and processed tilapia fish (Oreochromis niloticus) fillets were frozen at -18 ± 2oc. The physicochemical and microbiological analyses were carried out at regular 15 days interval on tilapia fish fillets stored for up to 90 days. The fresh fish fillets were found to contain 18.52±0.08% protein, 0.37 ± 0.01% fat, 79.87 ± 0.01% moisture and 0.98 ± 0.01% ash contents. During the entire period of storage, the protein, moisture and ash contents were significantly (p < 0.05) decreased to 17.25 ± 0.088%, 78.50 ± 0.71%, and 0.88 ± 0.02% respectively. However, the fat content of the fish fillets increased significantly (p < 0.05) to 0.56 ± 0.01 after 90 days of frozen storage. The TVB-N and pH values were also increased significantly (p < 0.05) from 12.04 ± 0.48 mg N/100g and 6.43 ± 0.01 to 21.75 ± 0.35 mg N/100g and 6.61 ± 0.01 respectively. The total bacterial load in fresh fish fillets was reduced from 2.57x106 to 8.2x105 CFU/g after 90 days of frozen storage. The total coliforms and faecal coliforms were also decreased from 460 MPN/g and 23 MPN/g to 23 MPN/g and undetectable level, respectively. From these results it was concluded that freezing, if not properly used, has a negative effect on reduction of nutritional value of fish products. The storage of tilapia fish fillets under frozen condition showed a significantly (p < 0.05) higher deterioration of product quality. The nutritional quality, as estimated by the proximate composition analysis, underwent a gradual loss of nutrients until day 90, in agreement with loss of freshness of the fish fillets observed for the TVB-N. Furthermore, the results revealed that gradual biochemical changes reduce the quality of frozen fish fillets as the duration of storage increases. Under frozen condition, the overall nutritional quality of tilapia fish fillets was found to depend on duration of frozen storage.
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    Characterization of Physicochemical Parameters for Tap Water and Removal of Hardness Using Moringa Stenopetala seed as Natural Absorbent The Case of Mekelle Town, Tigray Ethiopia
    (Addis Ababa University, 2007-06) Mesfin, Amhagiyorgis; Assefa, Berhanu (PhD)
    The physicochemical examination of tap water used for domestic purposes in Mekelle town was carried out to ascertain their suitability for consumption. Water softening experiments were also conducted to observe the changes in total hardness, with varying dosages of a natural coagulant. The natural coagulant was extracted from Moringa stenopetala seed A total of twenty (20) water samples were collected from various parts of the town tap water used for domestic purposes and characterized for their physicochemical parameters, arising public interest. The physicochemical implications render Mekelle’s tap water unfit for human consumption, though it can be used for other purposes. Tap water samples containing high concentration of hardness from Mekelle town, Enda Mariam and Enda Giyorgis areas were used for hardness removal mechanism part of this study. The optimum hardness removal efficiency for Mekelle tap water sample produced from ground water source was approximately 58 % (from initial total hardness of 523.25 to final hardness result of 220.3 which is within Ethiopian and WHO standard, i.e. below 300 mg/l as CaCO3) which was attained at M.Stenopetala dosage of 200 mg/l. The optimum hardness removal efficiency for synthetic hard water analysis done by taking two factors, coagulant dose concentration and PH as independent factors was approximately 49 % (from 500 to 256.6 mg/l as CaCO3) which was attained at M.Stenopetala dosage of 200 mg/l and 6.5 PH value. The mechanism for hardness removal in hard water seems to be precipitation of insoluble products of the reaction between M.Stenopetala extract and the hardness causing ions. Even at a relatively higher dosage of the M.Stenopetala coagulant compared to the chemical softening, natural coagulant is preferred for economic use, health and environmental safety. Key words: Water Hardness, coagulant protein, Moringa Stenopetala, physicochemical parameters, Tap water
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    Technical Assessment on Viability of Integrated Fruits Processing in Ethiopia
    (Addis Ababa University, 2007-07) Abebe, Elias; Admassu, Shimelis(PhD)
    The feasibility study of small scale processing of pineapple jam, mango jam and dried pineapple was studied. The methodology used for the feasibility study incorporates the three environments proposed by Lecup and Nicholson (2000) namely, market, technical (scientific and technological environment) and financial and economic environments. Pineapple cultivars (Ananas Comosus L,) Smooth cayenne and Red spanish at full ripening stage were collected from Teso in Sidama Zone. Mango samples were collected from Shebedino Woreda in Sidama Zone. Physico-chemical characteristics (pH, titerable acidity and soluble solid content) of the pulp, product yield (pulp and jam yield) and organoleptic attributes (color, aroma, flavor, degree of spreadability and acceptability) of the jam formulated from the crops were evaluated to assess the suitability of the local mango and pineapple varieties for jam production and consumer acceptability. It was observed that the pulp extracted from Smooth cayenne cultivar contain higher total soluble solids (16.23° Brix) and lower titrable acidity (0.7%) compared to the Red spanish cultivar. The total soluble solid and titerable acidity of the pulp from the local mango was 15.5° Brix and 0.36% respectively. The pH values of the pulp from both crops were found to be higher than 3.6 which is the maximum limit for formation of optimum gel for High Methoxy Pectin. The pulp yield (60%) and jam yield (95.5%) were higher for Smooth cayenne cultivar as compared to the Red spanish. Jam formulated from Smooth cayenne cultivar has scored the highest mean sensory scores in all quality attributes except in taste. However, panelists have found no significant difference (p<0.05) between the jam formulated form Smooth cayenne cultivar and imported pineapple jam except for flavor. Panelists showed less preference in taste of the jam formulated from Red spanish cultivar. Drying air temperature had an important effect on thin layer drying rate of pineapple slices. Drying at higher temperature, 70°C reduces the drying time by 46.2%, 33.3% and 33.3% for 4 mm, 6 mm and 8 mm slice thickness respectively. vii Slice thickness affected the drying time at all drying temperatures. Drying time was considerably elongated (> 11 hr) for 8 mm slice thickness at all drying air temperatures. The local demand for fruit jam jellies and marmalade is growing rapidly. Between 2003 and 2005, fruit jam, jelly and marmalade import to Ethiopia increase by 257% and 276% in terms of volume and value respectively. The import volume and value for these products reached 268,897 kg and 2,361,745 Birr respectively in 2005. Based on the projected feasible market share of the project the production scale of the processing plant was set at 33 tones per annum with production mix of 26 tones of pineapple and mango jam and 7 tones of dried pineapple. The production system was integrated to process pineapple and mango products to make all year round processing and diversification of products by utilizing availability of pineapple and mango at different times of the year. Most equipments and machineries required for this processing plant are available in local market at reasonable price, special equipments like pulper, peeler/corer, slicer and dryer could be manufactured by local workshop with support from research institutes and universities. The total investment cost of the processing plant including working capital is estimated as Birr 379,750. The project is feasible with IRR (30.1%), NPV (Birr 601,360) and the payback period of (3.3 years) at 15 % profit margin. The project can create employment opportunity for 16 people Moreover the project could contribute to: development of fruit agri-business through improved farm gate price, availability of consumer goods, reduce post harvest loss and lay background for innovations and technology adaptation
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    Evaluation of Imported and Local Wax for Cheese Processing
    (Addis Ababa University, 2007-07) Getachew, Solomon; Admassu, Shimelis (PhD)
    Despite large production and exportation of beeswax, the dairy processors import significant amount of wax for hard cheese coating. The drawback of the local beeswax which is being used for hard cheese processing is the cracking nature of the product, which in turn has an influence in the quality of cheese. The rationale of this study is to evaluate the locally available beeswax for hard cheese coating instead of imported wax. This study was conducted at Dairy Development Enterprise. Three samples were used for this study. Two locally available beeswax produced from honeycomb and from ’tej sefef’ and one imported wax as a control. The production method, which are very important for a good quality of beeswax are described in view of obtaining maximum quality. The physico-chemical characteristics of beeswax and imported wax are discussed. The mean value of the different parameters of the wax from ‘tej sefef’ and from honeycomb indeed, within the intervals commonly accepted by different countries specification. Saponification value (102.8500), specific gravity (0.9619), total volatile matter (0.4500) and melting point (64.3333) are slightly higher in wax from ‘tej sefef’ than wax from honeycomb; 99.7333, 0.9497, 0.3400, 64.1333 respectively. Whereas acid value and ash content are some what higher in wax produced from honeycomb. There was no significant difference between wax from honeycomb and wax from ‘tej sefef’ .The mean value of the different parameters of imported wax used for cheese coating was not within the interval of commonly accepted by different countries except total volatile matter and ash content. Moreover, there were significant difference between the two beeswax and imported wax. In the case of wax for cheese coating, beeswax produced from ‘tej sefef’ was cracked. There was significance difference between imported wax and beeswax produced from ‘tej sefef’ .However, there was no significant difference between imported wax and beeswax produced from honeycomb. The result of the data analysis revealed that beeswax produced from honeycomb gives the most promising result in this study, if the iv optimum processing conditions are maintained to obtain pure beeswax which can meet the standard.
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    Cleaner Production Assessment in The Ethiopian Alcohol Industries A Case Study in The Sebata Alcohol & Liquor Factory
    (Addis Ababa University, 2007-07) Belay Teffera; Berehanu Assefa (PhD)
    Sebeta Alcohol and Liquor Factory (SALF) is a sister company of National Alcohol and Liquor Enterprise (NALE). The factory was established in 1914 in Sebeta town and uses molasses as raw material for the production of potable and technical alcohols. It consists of a distillery and filling plants. Its installed daily production capacity is 2500 liters of potable alcohol and about 5000 liters of various liquors. The current production capacity was found to be on average 2100 liters of 95.7oGL potable (fine) and 250 liters of 93oGL technical alcohols per day when the factory was running normally. Water balance, material balance and energy balance were drawn only for the distillery plant for the filling section was under maintenance during sampling. The molasses, water and energy consumption were found to be 6.3 kg, 168 liters and 22.12 MJ liters per liter of 96oGL alcohol. The average BOD, COD and TDS in the wastewater were 20,866, 53,514 and 19000 mg/l respectively. The total alcohol loss from the fermentation, decantation and distillation process units was significant with the value of 13.22 %. The stillage from mash column is found a severe source of water pollution. The fermentation efficiency (78.02%), alcohol recovery at distillation unit (83.3%) and overall alcohol conversion efficiency (65.0%) were found to be low compared to values of similar technologies in India, South Africa and Brazil. The steam generation and distribution systems were studied and the boiler combustion efficiency was found extremely low (29%) resulting from excess air supply. Similarly, other sources of heat loss were identified and carefully examined The cleaner production options were generated, selected and evaluated for the distillery plant. CO2 Recovery, Cooling water recycling, lost heat recovery in the stillage and spent lee, indirect heating, generation of methane and fertilizer from stillage were considered for improving resource utilization and reducing pollution loads. Other GHK practices were recommended to bring overall efficiency in the plant.
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    Evaluation of Hydrogenation Process, Trans Fatty Acid Level and Some Qualities of Selected Hydrogenated Food Products in The Markets of Addis Ababa
    (Addis Ababa University, 2007-08) Gizaw, Eshetu; Asfaw, Nigist(PhD)
    Mass production of foods and extremely large variety of food products make the quantification of their nutrient composition a difficult task. Regulations on mandatory product labeling vary from country to country, but rarely include details of fatty acid composition. Ethiopia imports several tons of food items composed of entirely fatty acids and considerable amount of fat. However, there is no regulatory basis for control of fatty acid composition. Therefore, the present study has been initiated to evaluate the hydrogenation process and determine the TFA level and some physicochemical characteristics of hydrogenated food products in the markets of Addis Ababa. Samples in triplicate from each of the selected commercial margarines (MO1, MO2, MO3), vegetable ghee (GO1, GO2, GO3) and shortenings (SO1, SO2, SO3) were analyzed for their physicochemical characteristics and fatty acid composition. Physicochemical characteristics were determined following standard methods. The total composition of fatty acids of the isolated fat was determined by gas chromatography (GC). Characterization of the fatty acids was done using commercial standard reference material of fatty acid methyl esters (FAME). The process conditions of hydrogenation at Addis Modjo Edible Oil Complex (AMEOC) were evaluated to see their effects on TFA level. The data obtained from the laboratory analysis were subjected to ANOVA using SPSS software. TFA level of 3% was used as a reference mean (control). All the TFA means were then compared and significance was set at 5% level. The results showed that all the samples contained a considerable amount of TFA ranging from 18.9 to 52.6%, and significant mean differences were observed at p< 0.05. The physicochemical characteristics and other fatty acid values were found to be within the recommended range. Investigation of the hydrogenation process at AMEOC revealed that the high TFA is partly related to the hydrogenation method currently employed in the complex. The present study clearly indicated that the hydrogenated food products in Addis Ababa’s markets contain higher TFA levels compared to the same products studied in Europe and America. In this situation, continuous consumption of both local and imported hydrogenated food products may expose to greater risk of cardiovascular diseases. Reducing trans fatty acids through process optimization and introduction of enzymatic interesterification is unquestionably essential.
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    Evaluation of Ethanol Production from Intermediate Cane Molasses by Yeast (Saccharomyces Cerevisiae )
    (Addis Ababa University, 2007-12) Abebe, Fekadu; Admassu, Shimelis(PhD)
    The present study analyzes the influence of modification of sugar crystallization from three to two stages and tried to optimize both sugar and ethanol production from sugar cane source. The efficiency of sugar crystallization process was determined by simulation at Wonji Shoa Sugar Factory (WSSF). Economical advantages in optimizing the sugar and ethanol productions were compared with the factory’s existing working norms. Batch fermentation of molasses samples using saccharomyces cerevisiae was carried out at fermentation temperature of 30 (+1) o C, pH of 5.5 (+ 0.1) and ammonia supplement of 2 g/L in Erlenmeyer flask of 250 mL. The parameters varied were total sugar as invert (TSAI) in the fermentation broth of prepared molasses from both two and three crystallization stages and the amount of dry yeast in the inoculums (1,3,5 g/L). The measured values were concentration of the produced alcohol and the residual sugar. From the obtained data of alcohol concentration and residual sugar; the ethanol yield was calculated. All results obtained were subjected to SPSS and significance was set at 5% level. Alcohol concentration was found to vary from highest of 83 g/L to lowest of 36 g /L for molasses B (mB) and from highest of 53 g/L to lowest of 30 g/L for molasses final (mF), while residual sugar concentration varied from lowest of 26 to highest of 73 g/L for mB and 34 to 78 for mF. The calculated ethanol yield varied from highest of 0.47 g/g to 0.19 g/g and from 0.31 g/g to 0.16 g/g for mB and mF respectively. The variation was statistically significant (p 0.05).unfermentable sugar (%w/w) of 4.64 and 5.55 was obtained fro mB and mF respectively. Microorganisms’ results as total viable count were found as 378 CFU per 10 g of sample for mB and 428 CFU per 10 g of sample for mF. The net sugar produced was 12.61 % and 11.76 % cane from three and two crystallization system, whereas final molasses of 3.73 % and 4.79 % cane in three and two stage respectively were obtained. In the modification (from three to two stages), about 6.7% decreases in sugar product, an increase in molasses production quantity by about 28.4% and an increase in molasses TSAI content by about 28.8% respectively were obtained . The overall economic return by modification of the crystallization system indicates that there was additional income of 19.83 Eth. birr per ton of cane through optimum production of sugar and ethanol. The obtained results reveal that the modification in sugar crystallization system can bring over all improvement in both sugar and distillery plants and found economically feasible in the studied cases. Besides the economic return, the modification system tends to reduce the high recirculation of material, the energy utilization and the crystallization area capacity than the existing three crystallization system, with out affecting the product quality.
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    Studies on The Development of Baker’s Yeast Using Cane Molasses
    (Addis Ababa University, 2008-01) Damtew, Wondimagegen; Admassu, Shimelis(PhD)
    Three yeast strains were used for biomass production of baker’s yeast using wine, brewer and baker’s yeast strains. The effect of growing yeast saccharomayces cerevisiae on cane molasses with respect to baker’s yeast production was assayed. All yeast strains were cultured in YPD microbiological media and cane molasses media; their growth properties and biomass yield were examined using different substrate concentration of cane molasses and different nitrogen source chemical compounds. The studies on the feasibility of different types of yeast growth on cane molasses has been analyzed here. As a result of the kinetics study of growth of three yeast strains shows that baker’s yeast strain gives the best results to know a generation time reduced high growth rate and a high quantity of biomass. The maximum biomass yield and protein concentration was obtained with the 5 %(w/v) cane molasses of bakers` yeast; the effect of different concentration of cane molasses (5%, 10% and 15% sugar concentration) on biomass yield and protein concentration of bakers, wine and brewery yeast strains were studied. Biomass and protein formation was affected by the type of nitrogen present in the medium; high yield of protein being achieved in fermentation medium containing 2 % (w/v) (NH4)2SO4. Conversely medium, containing potassium nitrate had suppressive effect of protein production. Baker’s yeast production was industrialized using baker’s yeast strain in 5%(w/v) cane molasses with addition of ammonium sulphate.The results obtained on industrial scale feasibility study shows that the unit costs for the baker’s yeast production are $2.4 per kilogram, while the local market price for the baker’s yeast is $7.00/kg. It has good market demand and profitability analysis also provides positive results. Keywords: Baker’s yeast (saccharomayces cerevisiae), Biomass, molasses and Single protein.
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    Analysis of Fillers for Production of Alternative Building Materials Using Magnesia Cement
    (Addis Ababa University, 2008-01) Tadele, Tamrat; Assefa, Berhanu (PhD)
    Fillers, which are available in the country, are essential for the production of magnesia cement boards. These include pumice and lignocellulostic fillers such as bagasse, sawdust and coffee husk. While applying these fillers to produce the boards, their nature and performance should be studied. Magnesia cement was used as binding materials; varying boards were produced for different proportion fillers with fixed ratio of magnesium oxide and magnesium chloride. For the board produced, density, water absorption, and setting time as well as mechanical properties such as the compressive strength and the bending strength determined. In addition, the effects of different fillers on the properties of the board and production cost were examined. When the saw dust and coffee husk filler substituted the current used bagasse filler, the water absorption and setting time of the boards reduced. While the density, bending strength and compressive strength of the board increased. The mix ratio of fillers and pumice powder had also influence on the physical and mechanical property of the boards. The test results showed as the proportion of the pumice increased, the mechanical strength of the boards increased and the setting time of the cement paste reduced. The cost analysis showed that the saw dust board production cost was lower than coffee husk and bagasse board cost. While the production cost of the coffee husk board was slightly higher than others. viii In aim of production of filler boards as alternative building materials are, the cost comparison showed in the possibility of producing relatively low price than the hollow concrete blocks included finishing work cost.
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    Impact Assessment on Solid Health-Care Waste Management in Addis Ababa, And Identification of Energy Recovery Possibility
    (Addis Ababa University, 2008-05) Temesgen, Tatek; Gessesse, Nebiyeleul(PhD)
    In recent world the best way of protecting community health mainly depends on preventive methods rather than curative means. Due to this reason, having good solid health-care waste management and disposal in every health-care center is inevitable. The present study is conducted in five systematically selected sample hospitals in Addis Ababa. The main objective of the study was to assess the impacts arose from the current health-care solid waste management, predict proper treatment and disposal mechanism and check the possibility of heat recovery during treatment of waste. The sampling method used is two-stage cluster sampling with 90 % confidence level. In these sample hospitals, solid waste was collected for one week from 84 randomly selected beds of the total occupied 505 beds. The mean waste generation rate for the city was estimated to be 1.227± 0.253 Kg/ day. bed, like wise the generation rate for the private and governmental hospitals were estimated applying the same data. To achieve these results different statistical estimation methods are used. On top of this, proper on site sorting was done in order to perform proximate analysis to seven waste categories. Based on this analysis the maximum infected hospital waste in the city was estimated to be 662 Kg/day. Additionally, an attempt is done to address the overall solid waste management trend all over the routes to disposal. Possible Environmental, health and social impacts are identified for every waste management route. Analyzing the data found, health, environmental and social impact has 37.7, 35.6, and 26.7% impact contribution respectively. To identify the energy recovery of the treatment plant, secondary data from WHO that gives the minimum calorific value for infectious waste and estimated total generation rate of infectious waste in the city was used to determine the energy generation to be 104 Kg/hr, which is less than the capacity of medium sized steam generator. Since the capacity of the energy is less, possible ways of utilizing this small energy was suggested. Finally, based on the results and findings of the present study, certain solid waste management, treatment and disposal recommendations are forwarded to improve the management and minimize the impact of solid health-care waste in Addis Ababa.
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    Composting of Khat and Related Materials as Solid Waste Management Option in Awaday Town
    (Addis Ababa University, 2008-06) Yusuf, Mahabub; kifle, Zebene (PhD)
    The huge hip of solid waste has reduced the beauty of the town and became a breeding place of some rodents and vectors. Moreover; the waste encourages some people to dispose more and therefore exacerbates the poor sanitation of the town. The total daily average quantity of solid waste is determined to be approximately 13 tones according to the data obtained for April, 2008 from disposers (i.e. Khat shops or markets) and municipal waste collection department. The waste consists of leaves different plants such as khat, eucalyptus tree, small shrubs and grasses. And since the waste is dumped in an open air it is exposed to the chemical reaction facilitating conditions or factors such as temprature, air and moisture. The process of composting was started by preparing four sites each with 1m3 dimensions at Haramaya town. A track of Khat and related materials waste, which weighs 4 tones, was taken as sample from market center of Awaday. The compostible materials are separate from the waste stream and then shredded to an optimal size. The composing matter is segregate between two groups each with two piles and expose to two different sets of conditions. The piles in the first group are enclosing so as to prevent entry of rodents and exposure to sunlight. The other piles in the second group are left with no enclosure. However, the latter used to be covered with plastic sheets during rainy hours. Moreover, additional conditions and/or factors such as Aeration, moisture, particle size had been maintained and in a pile from each group, manure as facilitator has been used. Besides, temprature measurements have been taken daily till the end. The temperature of the piles was found to pick up to a maximum of 64°c. Then the temperature starts to decline to a daily average of 25°c as the compost in the center of pile is cool or reaches it’s maturity. The analytical results of the Nutrients contents of eight samples of composts taken give values 0.9-1.40 % for nitrogen, 532.00-803.00 ppm for available phosphorus and 6775.72-12445.24 ppm for available potassium. Above all the volume of waste piles have reduced from 1m3 to 0.40 m3 (i.e.60%). x The result of the study indicates that composting has effectively reduced the volume of the waste and can serve as means of removal. Besides, the widely varying nutrients content is significant enough to use the resulting compost as alternative fertilizer.
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    Effect of extrusion cooking on some quality attributes of full-fat soy flour and soy protein concentrate from locally grown Soybean (Glycine Max L.) varieties
    (Addis Ababa University, 2009-01) Muhsin, Fouzia; Zegeye, Adamu
    Soybean (Glycine max L.) varieties, Clark 63K and SCS1 were obtained from Jimma Agricultural Research Center. Their seed color and shape, seed density; hundred seed mass, hydration and swelling capacities, hydration and swelling indices, hydration and swelling coefficients were studied according to the standard procedures. The seeds were processed and converted into full fat soy flour (FFSF) and soy protein concentrate (FF-SPC) to study the effect of extrusion. The flours and concentrates from each variety were extruded at a barrel temperature of 140 0C, screw speed of 120rpm, and feed moisture of 30%. The effect on extrudates expansion ratio, specific length, proximate composition, flour and extrudate bulk density (BD), water absorption index (WAI), water solubility index (WSI), oil absorption capacity (OAC), emulsion activity (EA) and stability (ES), foaming capacity (FC) and stability (FS) was studied in triplicate samples. The result of the seed analysis of both varieties showed no statistical significant difference except in swelling coefficient. The bulk density of FFSF is significantly higher than that of FF-SPC flour, while FFSF extrudates have lower bulk density than that of the unprocessed flour. WAI of FF-SPC flour and extrudates of both varieties were found to be significantly higher than that of FFSF. WSI of FFSF flour and extrudates of both varieties are significantly higher than that of FF-SPC flour and extrudates. The OAC of FF-SPC flour is significantly higher than that of FFSF in both varieties, while that of the extrudates is significantly lower than that of their corresponding flours. EA and ES of extrudates of clark 63K and SCS1showed significantly higher values than the corresponding unprocessed flours. In general, the EA of SCS1 products are lower than that of Clark 63K, and the ES of Clark 63K and SCS1 is closer. The FC of FFSF is significantly higher than that of all products of both varieties. The FS of FFSF has been significantly higher than that of FF-SPC while the extrudates of SCS1 showed higher values of FS than that of Clark 63K. Generally, the present study showed that both varieties are suitable for extrusion cooking, with SCS1 slightly better performance. Based on the outcome of the study, the technology for developing an extruded product of soybean varieties has been suggested. Key words: Concentrate; extrusion cooking; flour; soybean
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    Production of Spirulina (Arthrospira) Using Trona As A Major Ingredient of Culture Medium
    (Addis Ababa University, 2009-02) Endrie, Muhiye; Kifle, Zebene(PhD)
    The impressive protein content and rapid growth of Spirulina in entirely alkaline medium have attracted the attention of both researchers and business men. Spirulina is one of the best solutions for the simple production of proteinuous food supplement. The protein content of Spirulina varies between 50 % and 70%. The present study was conducted to investigate the possibility of producing Spirulina in outdoor cultivation technology using a local product (Trona) as a substitute for the three major ingredients (NaHCO3, Na2CO3 & NaCl) in the Zarrouk’s standard culture medium. The standard medium (SM) was prepared from analytical grade chemicals and used as a control. Accordingly, a modified culture medium (MM) was formulated by incorporating Trona (Na2CO3.NaHCO3.2H2O). 400 ml brine sample was taken from Lake Chitu. The sample was filtered, and the SM & MM media, were inoculated in triplicate with the Spirulia contained in the brine. The growth of Spirulina continued for ten days with every 48 h monitoring. The data on Spirulina biomass interms of yield and chlorophyll content were collected. Chemical and microbiogical analyses were done. During the growth cycle, the exponential growth phase was mathematically analyzed. In the scaling-up trial, a plastic dish with a diameter of 60 cm was used in the place of a pond for 7 days. Accordingly, biomass determination, phyico- chmical analysis and sensory evaluation were conducted. The doubling time in the analysis of the exponential growth phase gave close values for both media (SM = 53 h, MM = 51 h). The rest of the data were analyzed and means compared by t-Test using SPSS software at 5% significance level. At the end of the experiment (10th day) the mean value of biomass yield was 823.743 mg/l and 832.498 mg/l for the MM and SM respectively. Cell productivity was 83.221 mg l-1day-1 for the SM and 82.374 mg mgl-1day-1 for the MM. The crude protein content of biomass was 50.53% and to 51.93 % in the MM and SM respectively. The odour of Spirulina in SM was rated 6.333 and that of the MM was rated 5.666, while the taste of the SM was 5.888 and the MM was 5.666. Comparison of the two mean values of yield, proximate analysis and sensory analysis showed that there was no statistically significant difference between the products in the SM and MM. This justifies that Trona can be used in the culture medium to cultivate Spirulina for human consumption. Finally, Spirulina production and processing technology has been outlined. Key words: Culture medium, production, Spirulina, Trona.
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    Neural Network predictive process modeling: Application to food processing
    (Addis Ababa University, 2009-03) Agide, Mesfin; Assefa, Berhanu (PhD)
    Currently, food processing industry is driven by several requirements. This requirement includes ensuring safety, meeting quality standard and customer expectation and reducing production cost to be competent in market. To achieve this requirement they have to operate at optimum process conditions all the time. In food processing, due to the nature of the process, it is difficult to find and operate at the best conditions solely by experience. The Ethiopia food industry is no coping up with such requirement due cost of optimization and low level of education of works operating in the production system. Thus, it is necessary modeling of the process or part of the process to capture the relation of between important process parameters and use the model to control and improve the process better. In addition, it is found necessary to make the model accessible for the operators working in Ethiopian industry. Using artificial neural network method is found to be very good modeling to tool to solve food engineering problems. In this thesis, therefore, artificial neural network method is used to model and tested for selected food industry engineering problems, specifically, water activity prediction, predictive food microbiology and control chart pattern recognition. The model is enclosed in interactive software so that it could also be used by people that do not have sophisticated mathematical and technical skills. The result obtained for all problems shows that neural network modeling can be used to model food process and to predict food process parameters with sufficient accuracy.