Homegarden Agroforestry as a Tool for Sustainable Production Unit in Ethiopia

Homegarden is the chief center of production unit in Ethiopia, particularly for the poor smallholder families. Homegarden is an area of land in the household’s compounds and its surrounding’s where different annual crops, livestock’s and trees integrated and produced. In the rural part of Ethiopia, homegarden agroforestry has a paramount importance since ancient time. It has been providing different useful products and services to millions of rural households. On the top of these benefits, little attention was given to homegarden agroforestry rather than giving due attention on how to make it more productive unit of land. This review paper was initiated to draw attention of scholars and policy makers through elucidating the production potential and ecological importance of homegarden agroforestry (HGA). HGA encompasses multiple components (tree, crop, livestock’s and etc), and intensive management practice with multistory production system based on the good will of the land user’s, knowledge and skills. HGA provides different goods to the household families’ including food/fruit, fuelwood, fodder, timber and other tree products. It also functions as in-situ conservation of biodiversity. Therefore, inclusion of appropriate multipurpose tree and shrub species is recommended to maximize the production potential of this unit of land. Keywords: Multiple products, production and productivity, Livelihood mechanisms DOI: 10.7176/JRDM/67-02 Publication date:July 31st 2020

Determinants of Food Insecurity in Pastoral and Agro-Pastoral Households of Ethiopia

Food insecurity is one of the prime challenges of Sub-Sahara African countries in general and pastoral and semi-pastoral households of Ethiopia in particular. Many researches has been investigated on food insecurity, however the problem remains still continuing especially during unfavorable climatic season. Different research findings pointed out that pastoral areas mainly characterized by unpredictable and unstable climatic conditions, as well as ecologically fragile environment. Pastoral areas are also characterized by frequent draught, conflict, flood and food insecurity as well as inadequate facilities and infrastructure. Low human development features, manifested by very low primary & secondary schools gross enrollment rate.  The paper went ahead to discuss on the vulnerability of pastoral communities to food insecurity, the causes of food insecurity was reviewed from different literatures. Determinants of food insecurity in pastoral and agro-pastoral households of Ethiopia and finally indicted some policy implications. Keywords:   food insecurity, pastoral DOI: 10.7176/FSQM/85-06 Publication date:March 31st 201

The Role of Urban Agriculture in Economic, Social and Environmental Sustainability in Africa

The role of urban agriculture in socio-economic and environmental sustainability in Africa was reviewed in this seminar. The main objective of this paper was to reveal the role of urban agriculture in socio-economic and environmental sustainability in Africa. Different theoretical and empirical literatures conducted by most scholars were rectified that the benefits of urban agriculture is unarguable issue. Many scholars argue that urban agriculture played a paramount significant role in job creation, in access to balanced diet, in access to fresh milk, vegetables and fruit for urban dwellers. Urban agriculture is also part of the urban greenery that improves the urban micro-climate, increases biological diversity, as well as the aesthetics and recreational functions of urban areas. But there were still some other scholars that urban agriculture has negative externalities on metropolitan. According to theories and empirical studies, not easy access to land, lack of experience, lack of financial support, grazing of crops by animals and theft of farm products, low land productivity, lack of training, access to credit facilities and high interest rates were  identified as the potential challenges for the development of urban agriculture. As a result of the numerous importance of this sector government and other non-government should initiate programmes in support of urban agriculture in order to overcome the aforementioned problems. Keywords: urban agriculture DOI: 10.7176/JNSR/9-2-0

Survivor Success Story: Mezgebu Abiyu Tesfaye

Mezgebu Abiyu Tesfaye, an Ethiopian landmine survivor, was born in the East Gojjam zone, Amhara region, in 1967. Raised in a farming family, Mezgebu left school after the eighth grade to help his parents care for their cattle and do daily chores

Isolation and Characterization of Sesquiterpenes from Stem Bark of Warburgia ugandensis Sprague

Warburgia ugandensis Sprague is one of the medicinal plants traditionally used to treat a number of diseases like asthma, cough, diarrhea, common cold, stomachache and toothache in Ethiopia. However, there is still insufficient information on the isolation and evaluation of bioactive compounds from this plant species. Extraction, purification and isolation of the stem bark of this plant by dichloromethane and chloroform as solvents afforded two sesquiterpenes; namely, WU-1 (ugandensidial) and WU-2 (cinnamolide-3β-acetate) respectively. The structural elucidations of these bioactive compounds were accomplished by using a variety of spectroscopic methods (IR, UV and NMR). The spectroscopic results compared with the reported data in the literature

The Role of Giving Feedback for Academic Achievement, A Case of Bule Hora University, Ethiopia

Feedback is an essential component in all learning contexts and without feedback of any kind; we would end up doomed to repeat the same mistakes over and over again. This study was aimed to explore the importance of feedback for academic achievement at Bule Hora University, College of Agricultural Sciences and Natural Resources Management Department. Quantitative and qualitative research design was employed in the study. Qualitative research design was used to explore the perception of respondents toward their educational status and quantitative research design was used to quantify some numerical data that percent and frequency, which was collected in the study college. A total of 47 respondents were used for the study by using the formula recommended by Kather (1985). The study findings indicated that the majority of respondents reflected the importance of feedback 31(65.9%). According to the finding, requirement of feedback was essential on given assessment types even though vary based on types of assessment. Since feedback is highly correlated with time, instructors are enforced to give feedback on time and students should award more about the values and mechanisms to enforce their instructors. The big problem of feedback was in appropriate follow up time by concerned body in that the department conducts teachers’ efficiency at the end of each semester that need to be modified soon. Keywords: Feedback, Perception, Academic, Achievement DOI: 10.7176/JEP/11-16-01 Publication date:June 30th 202

Fabrication of solar cells from poly(3-hexylthiophene) and ZnO Nanostructures

Mestrado em Ciência dos MateriaisAs células fotovoltaicas à base de compostos orgânicos e de híbridos do tipo orgânico/inorgânico têm recebido bastante atenção devido à sua potencial aplicação como fonte de energia limpa e económica. A utilização de nanoestruturas neste tipo de dispositivos tem também recebido especial atenção já que o confinamento quântico a elas associado promove a percolação, facilitando a passagem dos portadores de carga o que aumenta a sua eficiência. Nesta tese foram preparados dispositivos fotovoltaicos “bulk heterojunction” através da mistura de poli(3-hexiltiofeno) com diferentes nanoestruturas de ZnO. As nanoestruturas de ZnO (nanopartículas, nanofios e naofibras) foram preparadas por diferentes técnicas e caracterizadas por XRD, espectroscopia no UV-Vis, SEM e TEM. As nanopartículas e os nanofios de ZnO foram preparadas por métodos químicos em solução e decomposição térmica de acetato de zinco dihidratado respectivamente. As naonofibras de ZnO foram preparadas por calcinação de nanofibras compostas por alcóol polivinílico e acetato de zinco preparadas por “electrospinning”. As nanoestruturas preparadas foram ainda funcionalizadas com o ácido pireno-1-carboxílico. As nanoestruturas preparadas, funcionalizadas ou não funcionalizadas, foram misturadas com soluções de P3HT de modo a preparar dispositivos fotovoltáticos em duas configurações distintas. Numa delas os eléctrodos consistem em ITO e o alumínio depositado por evaporação térmica, na outra, os eléctrodos consistem em ITO e tinta de prata. O primeiro tipo de configuração utilizou a seguinte sequência: vidro/ITO/PEDOT:PSS/camada fotoactiva/Al. Na segunda configuração a sequência utilizada foi: vidro/ITO/ZnO/ camada fotoactiva/ PEDOT:PSS/Ag. As camadas de PEDOT:PSS bem como as camadas fotoactivas foram depositadas por spin coating. A caracterização dos dispositivos foi feita através de medições da corrente-tensão sob condições simuladas de iluminação padrão. Os dispositivos preparados apresentaram actividade fotovoltaica mas a sua eficiência ainda precisa de ser melhorada. ABSTRACT: Organic and organic/inorganic hybrid solar cells have been receiving a significant amount of attention due to their potential to yield environmentally friendly and cheap source of energy. As a result they are being investigated widely. Making use of nanostructures in such devices has also received a great attention as they provide percolative pathways for charge carriers by quantum confinement, helping in the improvement of the efficiency of the devices. In this thesis bulk heterojunction photovoltaic devices have been produced by blending different ZnO nanostructures and surface functionalized ZnO nanostructures with poly- 3-hexylthiophene. ZnO nanostructures (nanoparticles, nanowires and nanofibers) have been produced by different techniques and characterized by XRD, UV-Visible spectroscopy and SEM. ZnO nanoparticles and ZnO nanowires were prepared by wet chemical synthesis and thermal decomposition of zinc acetate dihydrate respectively. ZnO nanofibers were prepared by calcination of polyvinyl alcohol/zinc acetate composite nanofiber, which had been produced by the electrospinning process. These nanostructures were also surface functionalized with pyrene-1-carboxylic acid and characterized. Subsequently, these nanostructures and their surface functionalized forms were used to fabricate photovoltaic devices by combining them with P3HT and its whiskers. The photovoltaic devices have been prepared in two different configurations. In some ITO and aluminium deposited by thermal evaporation were used as the electrodes, while in the others ITO and silver paste were used. The first set of devices had the order glass/ITO/PEDOT:PSS/photoactive layer/Al, while the latter had the order lass/ITO/ZnO/photoactive layer/ PEDOT:PSS/Ag paste. The PEDOT:PSS and the photoactive layers were deposited by spin coating of the suspension of PEDOT:PSS in water and the suspension of the ZnO nanostructures in the poly-3-hexylthiophene solution respectively. The photovoltaic cells were finally characterized by current-voltage characteristics measurement under simulated standard illumination conditions. The photovoltaic devices prepared have demonstrated photovoltaic properties, but their efficiencies need further improvement

Concept for Ecotourism Industry: Over View from out to in (Ethiopia). A Review Articles

Ecotourism is an important and rapidly growing “niche market” within the global tourism industry, which can contribute to environmental conservation, socio-economic and gives value to the maintenance of local traditions and culture. The evolution of the concept of ecotourism could be traced from the 1980s, which coincides with the grounding of the concept of sustainable development. Although it has been difficult to calculate the size and growth rate of ecotourism, a range of estimates indicate that it has become the fastest growing sub-sector of the tourism industry. The contribution of ecotourism to rural livelihoods and livelihood diversification has received significant research attention and taken as determinants of livelihood outcomes. Ethiopia is a country of land of multiple tourist attractions and a visitor friendly people who are conscious of its historical, cultural and natural heritages in its regions. Even though it possesses a plethora of tourist attractions, yet tourism infrastructure, tourist products and marketing are at its infancy. The sector has direct, indirect and induced impact on the country’s economy, environment and cultural resources. To sustain sustainable development for the long run from the sector, balancing those impacts and giving attention towards peace and security as well as infrastructure development is crucial as the ecotourism industry mainly depend on them. Keywords: Ecotourism, Community, Tourism, Impact DOI: 10.7176/JTHS/51-02 Publication date:October 31st 202

Produksjon av biodiesel fra Jatropha curcas L. frø fra forskjellige agro-klimatiske soner i Etiopia: frøbehandling, oljeekstraksjon og optimalisering av biodieselproduksjon ved bruk av heterogene katalysatorer

Energy is basic for development and its demand increases due to population growth, urbanization, and the improvement of living standards in most parts of the world. Nowadays, the energy sector faces dual challenges, the need to meet the ever increasing energy demand and at the same time the concern for environment, particularly, reducing the carbon emissions. Fossil fuels are the main sources of energy and they will continue to dominate the other energy sources although they have negative impacts on the global climate and are non-renewable. The negative effects on the global climate and the uncertainty of the petroleum reserves has increased interests to search for alternative sources of energy which are renewable and have less pollution potential and carbon emission. One of such alternative sources of energy is the biodiesel, which is ecofriendly, renewable, biodegradable and nontoxic. Biodiesel can be produced from vegetable oils, animal fats, waste oils and microalgae. Production of biodiesel from edible vegetable oils resulted in food vs fuel debate, and thus, nowadays production of biodiesel from the oil of non-edible crops such as jatropha seeds is preferred. Jatropha seed oil has been considered as a promising biodiesel feedstock as it is non-edible due to the presence of a toxic compound (the phorbol ester) in it and the oil content of the seed is high. The oil contents of jatropha seeds and seed kernel vary from 20-60% and 40-60%, respectively. The primary objective of the present thesis is to determine the oil contents of different jatropha seed collections and optimize biodiesel production using reusable and low cost heterogenous catalysts. For this purpose, the thesis attempted to identify the suitable conditions for jatropha seed drying for oil extraction in order to determine the oil contents of different jatropha seed collection. Some physco-chemical properties of the oils were also evaluated to determine whether the oils could be used for biodiesel production or not. Moreover, to search for low cost and more sustainable methods of biodiesel production, renewable alcohols and reusable and low cost heterogenous catalysts were used to produce biodiesel at different reaction conditions, and to optimize the reaction process. The present PhD thesis is based on six scientific papers that systematically presented interrelated research activities that included the investigation of different biodiesel feedstocks and various oil extraction methods, techniques of seed drying for oil extraction, extraction of oil from different jatropha seed collections and biodiesel production using renewable alcohols, and reusable and low cost heterogenous catalysts. The research activities in this thesis are interrelated and stepwise activities, and the results obtained from the preceding works were used as the bases and/or inputs for the next activities. Accordingly, the research work was started with the review of the state of art of relevant literature to evaluate the advantages and limitations of using different biodiesel feedstocks and oil extraction methods from different oil sources in general, and from plant seeds in particular (Paper I). From a thorough examination of the literature reports, it was understood that oils from non-edible crops such as jatropha was identified as a promising feedstock for biodiesel as using such oils does not compete with human consumption. Moreover, jatropha seeds have high oil content and the plant has great adaptation potential to various climates. Solvent extraction method was also selected for oil extraction from the seeds due to its efficiency in oil extraction and its simplicity and affordability. The experimental part of the study began with drying a selected jatropha seed collection at storage conditions for oil extraction as the moisture in a seed can affect the oil yield and the quality of the oil. The pretreated crushed seeds and non-pretreated whole seeds were dried at five different temperatures (40, 50, 60, 70 and 80 oC) to identify the temperature and the pretreatment that could reduce the seed moisture to its minimum (Paper II). From this experiment, it was concluded that drying the whole seeds of jatropha at 80 oC for 2880 minutes produced the dried seed with suitable residual moisture (0.34%) for oil extraction. The moisture ratios calculated from the systematically recorded moisture loss from the drying seeds indicated above were adjusted to four semi-theoretical drying mathematical models (Lewis, Henderson and Pabis, Page and Avhad and Marchetti models) to determine the model that best fitted to the experimental drying kinetics of the seeds (Paper III). Among the employed mathematical models, Avhad and Marchetti model showed the best fitting to the experimental data. In Paper IV, after drying the seeds using the previously determined techniques, thirteen different jatropha seed collections were extracted with a Soxhlet extractor using hexane as solvent and cotton or thimble as filter to determine the seed collection that could give the largest percentage of oil. The physco-chemical properties of the sample from mixed oil (a mixture formed from oils from thirteen jatropha seed collections) and oil of Chali seed collection were also determined in order to use these oils for biodiesel production. Moreover, the heat contents of the de-oiled seed residues were determined as using such residues as an energy source can contribute to a reduction of the biodiesel production costs. In the extraction with cotton, Dana seed collection gave the largest oil yield (48.29%) while in the extraction with thimble, the largest oil yield (45.79±0.54%) was obtained from Chali seed collection. The results from the physco-chemical analyses of both oil samples suggested that the oils can be used for biodiesel production. Furthermore, since the average gross calorific value of the de-oiled jatropha seed residues after oil extraction was found to be about 19.64 MJ kg-1, the residues can be used as the source of heat. Two transesterification reactions were performed to produce biodiesel using renewable alcohols and reusable heterogenous catalyst at different reaction conditions to optimize the reaction processes. In the first reaction, the mixed oil (mixture of oils extracted from thirteen different seed collections) was reacted with ethanol using Amberlyst A26 (OH), anion ion exchange resin, at various reaction temperature, ethanol: oil molar ratio and catalyst percent to optimize the oil conversion and biodiesel yield (Paper V). From this study, it was found that the reaction temperature highly affected the reaction process. The maximum oil conversion (38.12%) and ester yield (36.81%) were experimentally obtained at an optimum temperature of 55 oC, alcohol: molar ratio of 35:1 and catalyst amount of 15%. Based on results obtained from the first experiment, it was suggested that upscaling of the oil conversion and biodiesel yield by using an integrated reaction factors, as well as reducing the amount of alcohol employed is needed. In the second transesterification reaction, glycerol enriched non-calcined calcium oxide was employed to catalyze the reaction of the oil of the Chali seed collection (Chali oil) with butanol at different temperatures and butanol: oil molar ratio by employing a constant amount of catalyst (15%wt) and glycerol (15%wt of the catalyst) (Paper VI) to optimize the process. From this study, it was found that the reaction temperature significantly affected the reaction process (p ≤ 0.05). Moreover, the maximum oil conversion of 98.16% was predicted to be obtained at the optimum temperature of 87.35 oC and butanol: oil molar ratio of 9.13:1. The maximum butyl ester yield of 95.79 % was also estimated to be found at the optimum temperature of 90.48 oC and butanol: oil molar ratio of 13.24:1. Furthermore, the butyl ester yield of 95.64% was experimentally obtained at the predicted optimum conditions for the ester yield. From the results of the second reaction, it was suggested that glycerol enriched non-calcined commercial calcium oxide can be used as a good alternative catalyst for biodiesel production using butanol.Energi er grunnleggende for all utvikling og etterspørselen øker på grunn av befolkningsvekst, urbanisering og forbedring av levestandarden i de fleste deler av verden. I dag står energisektoren overfor doble utfordringer, behovet for å imøtekomme det stadig økende energibehovet og samtidig bekymringen for miljøet, spesielt for å redusere karbonutslippene. Fossilt brensel er de viktigste energikildene, og de vil fortsette å dominere over de andre energikildene, selv om de har en negativ innvirkning på det globale klimaet og ikke er fornybare. De negative effektene på det globale klimaet og usikkerhetene omkring petroleumsreservene har økt interessen for å søke etter alternative energikilder som er fornybare og har mindre forurensningspotensiale og karbonutslipp. Biodiesel er en slik alternativ kilde til energi; den er miljøvennlig, fornybar, biologisk nedbrytbar og ikke-giftig. Biodiesel kan produseres fra vegetabilske oljer, animalsk fett, avfallsoljer og mikroalger. Produksjon av biodiesel fra spiselige vegetabilske oljer resulterte i mat vs drivstoffdebatt, og i dag foretrekkes nå produksjon av biodiesel fra olje som kommer fra fra ikke-spiselige vekster, slik som jatrophafrø. Jatropha har blitt sett på som et lovende råstoff for biodiesel, ettersom oljen er ikke spiselig på grunn av tilstedeværelsen av en giftig forbindelse (phorbolesteren), og oljeinnholdet i frøet er høyt. Oljeinnholdet i jatropha frø og frøkjernen varierer fra henholdsvis 20-60% og 40-60%. Hovedmålet med den herværende oppgaven er å bestemme oljeinnholdet i forskjellige jatrophafrø innsamlet i Etiopia og optimalisere biodieselproduksjon ved å bruke gjenbrukbare og rimelige heterogene katalysatorer. Med dette formålet forsøker avhandlingen å identifisere egnede betingelser for tørking av jatrophafrø for å ekstrahere olje, for deretter å bestemme oljeinnholdet i de forskjellige jatrophafrøkildene. Noen fysisk-kjemiske egenskaper av oljene ble også evaluert for å bestemme om oljene kunne brukes til biodieselproduksjon. For å finne de laveste kostnadene og mer bærekraftige metoder for biodieselproduksjon, ble dessuten fornybare alkoholer og gjenbrukbare og rimelige heterogene katalysatorer brukt til å produsere biodiesel ved forskjellige reaksjonsbetingelser, og for å optimalisere reaksjonsprosessen. Den nåværende doktorgradsavhandlingen er basert på seks vitenskapelige artikler som systematisk presenterte sammenhengende forskningsaktiviteter som inkluderte utredning av forskjellige biodiesel råstoff og forskjellige oljeekstraksjonsmetoder, teknikker for frøtørking for oljeekstraksjon, ekstraksjon av olje fra forskjellige jatrophafrøsamlinger og biodieselproduksjon ved bruk av fornybare alkoholer, samt gjenbrukbare og rimelige heterogene katalysatorer. Forskningsaktivitetene i denne avhandlingen henger sammen og trinnvis, og resultatene oppnådd fra de foregående arbeidene ble brukt som baser og / eller innspill til de neste aktivitetene. Følgelig ble forskningsarbeidet startet med en gjennomgang av den aktuelle teknikk for relevant litteratur for å evaluere fordelene og begrensningene ved å bruke forskjellige biodieselråstoff og oljeekstraksjonsmetoder fra forskjellige oljekilder generelt, og fra plantefrø spesielt (Artikkel I). Fra den detaljerte gjennomgangen av litteraturen ble det antydet at oljer fra ikke-spiselige avlinger som jatropha er identifisert som et lovende råstoff for biodiesel ettersom bruk av slik olje ikke konkurrerer med matproduksjon direkte. Dessuten har jatrophafrø høyere oljeinnhold, og planten har stort tilpasningspotensial til forskjellige klima. Oppløsningsmiddelekstraksjonsmetode ble også valgt for oljeekstraksjon fra frøene på grunn av dens effektivitet i oljeekstraksjon og dens enkelhet og rimelig kostnad. Den eksperimentelle delen av studien ble startet med tørking av en valgt jatrophafrøsamling etter lagring. Lagringstilstand før oljeekstraksjon kan ha betydning for oljeutbyttet og kvaliteten på oljen, siden fuktigheten i et frø påvirker dette. De forbehandlede knuste frøene og ikke-forbehandlede hele frøene ble tørket ved fem forskjellige temperaturer (40, 50, 60, 70 and 80 oC) for å identifisere temperaturen og forbehandlingen som kunne redusere frøfuktigheten til sitt minimum (Artikkel II). Fra dette eksperimentet ble det konkludert med at tørking av hele frøene av jatropha ved 80 oC i 2880 minutter ga det tørkede frøet med passende restfuktighet (0,34%) for oljeekstraksjon. Fuktighetsforholdene beregnet ut fra det systematisk registrerte fuktighetstapet fra tørkefrøene som er angitt ovenfor, ble justert til fire semi-teoretiske tørkende matematiske modeller (Lewis, Henderson og Pabis, Page og Avhad og Marchettis modeller) for å bestemme hvilken modell som passet best til forsøket tørkingskinetikk av frøene (Artikkel III). Av de anvendte matematiske modellene viste Avhad og Marchetti-modellen seg best tilpasset til eksperimentelle data. I Artikkel IV ble tørrinnsamling av jatrophafrøekstrakt med Soxhlet-ekstraktor ved bruk av de tidligere optimale teknikker, og ved å anvende heksan som løsningsmiddel, og bomull eller fingerbøl som filter, for å finne den frøsamlingen som kunne gi den største prosentvise oljen. De fysisk-kjemiske egenskapene til prøven fra blandet olje (en blanding dannet av oljer fra tretten jatrophafrøsamlinger) og olje fra Chali-frøsamlingen ble også analysert for å bruke disse oljene til biodieselproduksjon. Videre ble varmeinnholdet i frørestene etter oljeutvinning bestemt fordi bruk av slike rester som energikilde kan bidra til med å redusere de totale investeringskostnadene for biodieselproduksjon. I ekstraksjonen med bomull ga Dana-frøsamlingen det største oljeutbyttet (48,29%), mens i ekstraksjonen med fingerbøl ble den største mengden olje (45,79 ± 0,54%) oppnådd fra Chali-frøsamlingen. Resultatene fra den fysisk-kjemiske analysen av begge oljeprøvene antydet at oljene kan brukes til biodieselproduksjon. Siden de gjennomsnittlige brutto brennverdiene av jatrophafrørestene etter oljeekstraksjon var ca. 19,64 MJ kg-1, kan restene brukes som varmekilde. To transesterifiseringsreaksjoner ble utført for å produsere biodiesel ved bruk av fornybare alkoholer og gjenbrukbar heterogen katalysator ved forskjellige reaksjonsbetingelser for å optimalisere reaksjonsprosessene. I den første reaksjonen ble den blandede oljen (blanding av oljer ekstrahert fra tretten forskjellige frøsamlinger) omsatt med etanol ved bruk av Amberlyst A26 (OH), anionionbytterharpiks, ved forskjellige reaksjonstemperaturer, etanol: olje-molforhold og katalysatorprosent for å optimalisere oljeomdannelse og biodieselutbytte (Artikkel V). Fra denne studien ble det funnet at reaksjonstemperaturen påvirket reaksjonsprosessen sterkt. Maksimal oljeomdannelse (38.12%) og esterutbytte (36.81%) ble eksperimentelt oppnådd ved en optimal temperatur på 55 oC, alkohol: molforhold på 35:1 og katalysatormengde på 15%. Basert på resultater oppnådd fra det første eksperimentet, ble det antydet at oppskalering av oljekonvertering og biodieselutbytte ved bruk av integrerte reaksjonsfaktorer, samt reduksjon av anvendt alkoholmengde er nødvendig. I den andre omesterifiseringsreaksjonen ble glyserolanriket ikke-kalsinert kalsiumoksyd anvendt for å katalysere reaksjonen fra oljen fra Chali frøsamlingen (Chali olje) med butanol ved forskjellige temperaturer og butanol: olje (i et molært forhold) ved å bruke en konstant mengde katalysator (15% vekt) og glyserol (15 vekt% av katalysatoren) (Artikkel VI) for å optimalisere prosessen. Av denne studien fant vi at reaksjonsprosessen ble betydelig påvirket av reaksjonstemperaturen (p ≤ 0,05). Videre ble den maksimale oljekonvertering på 98,16% forventet å være oppnådd ved en optimale temperatur på 87,35 oC og et butanol: olje-molforhold på 9,13:1. Det maksimale butylesterutbytte på 95,79% ble også beregnet til å bli oppnådd ved en optimal temperatur på 90,48 oC og butanol: olje-molforhold på 13,24:1. Vi viste eksperimentelt et butylesterutbyttet på 95,64% ved de forutsagte optimale betingelsene for esterutbyttet. Av resultatene fra den andre reaksjonen er det mulig at glyserolanriket ikke-kalsinert kommersielt kalsiumoksyd kan brukes som et god alternativ katalysator for biodieselproduksjon ved bruk av butanol.EnPe/Norad project entitled “Research and Capacity Building in Clean and Renewable Bioenergy in Ethiopia

Hall effect in printed Nanoparticulate Silicon Networks

Silicon nanoparticles for the application of printed electronics were successfully synthesised and characterised. High energy milling has been proven to yield uncontaminated powder of median particle size 150 nm satisfying a lognormal distribution. Single crystalline P- and N-type silicon wafers, and metallurgical grade silicon were used as starting materials. The structural characterisation of all milled powders using X-ray diffraction (XRD), Small Angle X-ray Scattering (SAXS) and electron diffraction proved that the silicon nanoparticles are polycrystalline with a crystallite size of about 40 nm. For the first time, we have formulated printable semiconducting inks from nanoparticulate silicon. Silicon nanoparticles were mixed with organic binders, such as linseed oil and acrylic, to produce printable inks. Similarly nanoparticulate silicon ink, doped with inorganic salts, which is a different procedure to conventional impurity doping of the silicon structure, was produced with linseed oil. A home-built Hall measurement system was used to characterise layers of doped ink, for which a complete carrier type reversal was observed. Based on the result of elemental mapping, two possible models were suggested to explain the doping effect. A state-of-the-art Hall measurement system was used to perform field dependent analysis of screen printed silicon inks in van der Pauw geometry. A magnetoconductivity tensor model was developed to extract the carrier properties. All the layers were demonstrated to have at least two carrier types. Inks produced from P-type silicon maintained their carrier type, but reversal was observed for the N-type layers. The mobility of the carriers is better or comparable to similar classes of semiconducting materials. 2 More information on the interparticle connections were obtained from IV and impedance spectroscopy measurements which demonstrated the capacitive effects present in the printed layers. The capacitors originate at the interfaces between the metal and the layers and between the particles