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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
Get PDFEnergy 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
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Relevance and safety of Chemistry laboratory experiments from students’ perspective: a case study at Jimma University, southwestern Ethiopia
No full textThe main objective of this study was to gather students’ opinion about the relevance and safety of Chemistry laboratory experiments. The study population of the study were undergraduate students majoring Chemistry, at Jimma University. The data were collected from randomly selected 123 students using structured questionnaires prepared in English. The result was analyzed (interpreted) using or based on calculated percentages. The results indicated that students in Chemistry laboratories are given opportunities to learn by doing i.e., self-practicing of experiments (62, 50.4%). Several advantages of Chemistry practical classes (experiments) were mentioned by the respondents. Some of the advantages were practical classes enable students in proper handling of chemicals and operating apparatus and instruments (42, 38.2%), data collection, interpretation and report writing skill (40, 32.5%) and developing attitude towards scientific research (36, 29.2%). Even though there are some complaints by students. Almost all the respondents (109, 88.6%) enjoyed laboratory classes offered by the Department. The group work currently employed in all chemistry laboratories are accepted by the majority (72, 58.5%) of the respondents. Organic Chemistry laboratory experiments were mentioned as potentially more dangerous than experiments in other Chemistry streams. Keywords: Chemistry laboratory, Jimma university, self-practicing, chemistry laboratory experiments, Community-based education (CBE)
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Survey on the usage of plastic bags, their disposal and adverse impacts on environment: A case study in Jimma City, Southwestern Ethiopia
No full textPlastic bag wastes pose serious environmental pollutions and health problems in humans and animals.
The situation is worsened in economically disadvantaged countries like Ethiopia. The objective of this
survey was to assess usage of plastic bags and their environmental impacts in Jimma City of Ethiopia.
A semi-structured questionnaire was used to collect data from 230 randomly selected respondents. The
results indicated that the larger proportion (176, 76.52%) of the respondents used plastic bags more
frequently than any other plastic products regardless of their age, occupation, and economic and
educational status. Low price (159, 69.13%) and easy availability (152, 66.08%) were the main reasons
for the widespread utilization of these products. Among the practices used for disposal of plastic bag
wastes, open dumping to surrounding areas (137, 59.56%) was a practice widely used by almost all the
residents of the city. Some of the major problems were animal death (167, 72.60%), blockage of sewage
lines (162, 70.43%), deterioration of natural beauty of an environment (144, 62.60%) and human health
problems (119, 51.73%). The findings of the present study also indicated that the trend of utilization of
plastic bags is increasing from time to time in spite of a good deal of awareness of the residents about
the adverse effects of these products. In order to reduce the problems associated with plastic bag
wastes, it is recommended to educate the public (1) not to use plastic bags, and (2) to use eco-friendly
alternative materials (bags) made from clothes, natural fibers and paper. City level legislation is also
highly recommended against indiscriminate use and disposal of plastic bag wastes as well as to end
free distribution of plastic bags by retailers
Evaluation of antileishmanial activities of triglycerides isolated from roots of Moringa stenopetala
No full textThe objective of this study was to evaluate antileishmanial activities of compounds isolated from the roots of Moringa stenopetala. Two compounds were isolated from the crude petroleum ether:ethyl acetate (50:50 %) extract of its roots employing column chromatographic technique using a mixture of petroleum ether and ethyl acetate mixture in different polarity (or proportions by volume). The isolated compounds were labeled as MS-1 and MS-2. Their structures were determined to be triglycerides based on the observed spectroscopic (1H-NMR, 13C-NMR, DEPT-135, and IR) data and reported data in literature. Thus, compound MS-1 and compound MS-2 were identified as 1,3-dilinoleoyl- 2-olein and 1,3-dioleoyl-2-linolein, respectively. Evaluation of antileishmanial activities (IC50 values) of the compounds against promatigote stage of Leishmania aethiopica indicated that compound MS-1 to show comparable activity with the reference compounds (amphotericin B and miltefosine) whereas compound MS-2 to be less active. The activity test results against the amastigote stage of the parasite indicated that the compounds have comparable activities when compared to each other, and relatively lower activities as compared to that of the reference compounds. The results suggested that the compounds have promising antileishmanial activities. However, further in vivo tests are recommended before drawing any conclusion about the potential of the compounds as a new antileishmanial drug candidate
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