Browsing by Author "Assefa, Mekonnen"

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    Biodiesel from Microalgae Based on Co2 Released from Cement Industries (Case Study: - Dangote Cement Plant)
    (Addis Ababa University, 2016-06) Assefa, Mekonnen; Yimam, Abubeker (PhD)
    Fossil fuels which are recognised as common sources of energy are continuously decreasing in quantity due to increasing demand, Moreover, the increase in atmospheric carbondioxide from chemical industries like cement plants is resulting in global climate change. In order to achieve environmental and economic sustainability, 3rd generation biofuel derived from microalgae are considered to be the best alternative energy resource compared to 1st and 2nd generation biofuels. Mixed species of microalgae was sourced locally from Kilole Lake at Bishoftu district and found suitable feed stock to produce algal biodiesel in the laboratory. Experiments were carried out using PVC jars of 3.5 litre capacity using 0.1 to 4% carbondioxide concentration, air bubbling rate of 0.1 to 7.0 litre per minute and pH ranged between 5 -7. The maximum biomass was obtained 0.44 gm/lt at pH 7, bubbling rate 3.5 lt/min and 2% carbondioxide feed. Oil was extracted from the algal biomass and analysed for water content, acid value, and fatty acid composition and saponification value. Algal oil fatty acid composition was very low and as a result of this no pre-treatment of algal oil was needed. Biodiesel produced by transesterfication of algal oil performed by using sodium methoxide as catalyst, and it was analysed for kinematic viscosity, specific gravity, acid value and sulphated ash. The properties of biodiesel tested were within limits of ASTM standard. Scale up of biodiesel plant in integration with the cement industry facility was studied as a way to mitigate the carbondioxide released from the plant flue gas as well as to address the shortage of fossil fuel in our country. Using the preliminary design of the biodiesel plant, a production capacity of 5,860 ton/year biodiesel was obtained and it was possible to capture 22,893.3 ton per year carbondioxide released from the cement industry. The net energy ratio of the proposed plant is 1.03; meaning 3% of energy can be produced more than required by the process. Key words: - Algal biomass, carbon dioxide, lipid oil, Biodiesel, Raceway pond
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    Survival and morbidity of breastfeeding versus formula feeding infants and young children of HIV-infected women who are on PMTCT follow up on selected hospitals in Addis Ababa, Ethiopia, 2013: a retrospective cohort study.
    (Addis Abeba University, 2013-08) Assefa, Mekonnen; Worku, Alemayehu (PhD)
    BACKGROUND: Nearly 90% of the almost half a million children who yearly become infected with HIV through their mothers live in sub-Saharan Africa. Infant feeding in the context of HIV is complex because of the major influence that feeding practices and nutrition have on child survival. HIV-infected mothers face a dilemma regarding how to feed their newborn infants due to the competing risk of HIV transmission associated with breast-feeding and the risk of increased morbidity and mortality associated with formula feeding. OBJECTIVE: To compare the survival and health benefits of breast feeding and formula feeding infants and young children of HIV infected women followed the PMTCT programs. Method: A retrospective cohort study design was employed to compare the HIV free survival of exposed infants and young children who were on breast fed and formula fed. Data was extracted from PMTCT registration book and exposed infants follow up card. Data were entered in Epi info (version 3.5.3 software) and exported into SPSS version 16 and STATA version11 statistical software for analysis. Infants and young children morbidity and HIV infection (i.e., the complement of HIV-free survival) were compared by using Kaplan- Meier time-to-event method and long rank test was used to compare HIV free survival between the two groups. Cox regression analysis was used to assess the determinant factors. RESULTS: Overall probability of HIV free survival in formula fed infants and young children was significantly higher than breast fed infants and young children (log rank test statistics =6.13, df=1, p=0.013). Breast fed infants and young children had four (adjusted HR =3.8, 95%CI 1.311.1) times higher risks to acquire HIV infection as compared to formula fed infants and young children. Mothers who didn’t use any PMTCT intervention had five fold risk to transmit HIV infection to their infants (Adjusted HR=4.8, 95%CI; 1.1-22.5). There was no statistical significant different risk of developing any types of morbidity between the two groups (log rank statistics =0.92, df=1, p=0.34). There were totally seven deaths of infants in both cohorts. Conclusion and recommendations: the 18 month cumulative probability of HIV free survival was significantly lower in the breast feeding infants and young children as compared to formula fed infants and young children. Using formula feeding or Breastfeeding and receiving ARVs prophylaxis should be the one that will most likely give infants the greatest chance of HIV-free survival.