Quantification of the potential for biogas and biogas manure from the selected fruit wastes in Addis Ababa city, Ethiopia

In this paper, the overall potential of biogas and biogas manure from the selected fruit wastes in the city of Addis Ababa was estimated (quantified). The prediction is based on the characterization and biogas yield results in a related study, using structured questionnaire and checklists during field survey. This study has shown a survey of the major sources of the fruit wastes and compiled the number of registered service providers in this particular sector by category. Consequently, this study has shown that the wasted biogas potential of the city from the selected 164.51 tons of daily fruit wastes alone was 20896 m3 per day. This wasted energy material is equivalent to 9000 L of diesel fuel that currently would cost 9389 US dollars. Further, soil nutrients that could be obtained from use of anaerobic digestion of the selected fruit wastes are 366 kg/day of total phosphorus, 798 kg/day of total nitrogen and 565 kg/day of potassium, which are also lost in vain. Therefore, the study shows the importance of proper organic waste management for the recovery of clean energy and nutrients, while at the same time avoiding expenses to buy fossil fuel as source of energy and reduce the associated stress on our environment and more.Key words: Biogas potential, fruit waste, quantification, prediction, biogas manure

Removing carbon dioxide from a stationary source through co-generation of carbonate/bicarbonate: The case of Mugher cement factory

The cement industries alone emit 5% of the world’s total green house gases. In Ethiopia, the current CO2 emission from this sector is about five fold of the countries overall CO2 emission in 2002. Mugher cement factory (MCF), a case study plant in this paper, alone emits 463,844 tons of CO2/year on average based on emission test and mass balance performed. Yet it accounts for less than 3% of the current CO2 emission from this particular industry in the country. Of those technical approaches, separation of CO2 before it joins the immediate atmosphere is getting wide spread interest. In relation to this, experiment on absorption of CO2 is conducted to determine the effect of flow rate of the gas sample, concentration of the sodium hydroxide, flow rate of solvent and temperature of absorbent on absorption of CO2 using the “Armfield” gas absorption column followed by the titrimetric analysis. Except temperature of solvent, all study variables showed strong relation with the amount of carbon dioxide absorbed (with a P-value < 0.05). Uniquely, this study has evaluated the potential for sodium bicarbonate production from the CO2 absorbed using gravimetric analysis. It is also possible to recover over 28% crystal sodium bicarbonate.Key words: Green house gas, CO2, absorption, caustic soda, sodium bicarbonate

Thermophilic versus Mesophilic Anaerobic Digestion of Sewage Sludge: A Comparative Review

During advanced biological wastewater treatment, a huge amount of sludge is produced as a by-product of the treatment process. Hence, reuse and recovery of resources and energy from the sludge is a big technological challenge. The processing of sludge produced by Wastewater Treatment Plants (WWTPs) is massive, which takes up a big part of the overall operational costs. In this regard, anaerobic digestion (AD) of sewage sludge continues to be an attractive option to produce biogas that could contribute to the wastewater management cost reduction and foster the sustainability of those WWTPs. At the same time, AD reduces sludge amounts and that again contributes to the reduction of the sludge disposal costs. However, sludge volume minimization remains, a challenge thus improvement of dewatering efficiency is an inevitable part of WWTP operation. As a result, AD parameters could have significant impact on sludge properties. One of the most important operational parameters influencing the AD process is temperature. Consequently, the thermophilic and the mesophilic modes of sludge AD are compared for their pros and cons by many researchers. However, most comparisons are more focused on biogas yield, process speed and stability. Regarding the biogas yield, thermophilic sludge AD is preferred over the mesophilic one because of its faster biochemical reaction rate. Equally important but not studied sufficiently until now was the influence of temperature on the digestate quality, which is expressed mainly by the sludge dewateringability, and the reject water quality (chemical oxygen demand, ammonia nitrogen, and pH). In the field of comparison of thermophilic and mesophilic digestion process, few and often inconclusive research, unfortunately, has been published so far. Hence, recommendations for optimized technologies have not yet been done. The review presented provides a comparison of existing sludge AD technologies and the gaps that need to be filled so as to optimize the connection between the two systems. In addition, many other relevant AD process parameters, including sludge rheology, which need to be addressed, are also reviewed and presented

Knowledge, Attitude, and Practice on Hygiene and Morbidity Status among Tertiary Students: The Case of Kotebe Metropolitan University, Addis Ababa, Ethiopia

Considerable fractions of the world’s diseases are communicable, of which over 60% are infectious. Knowledge, attitude, and practice of hygiene are very important to decrease these disease burdens especially in places like higher education institutions. This study is aimed at revealing the status and gaps on knowledge, attitude, and practice of hygiene among Kotebe Metropolitan University students. Alongside, morbidity records of the students’ clinic are reviewed. Sampled regular students who are boarding and who serve the students’ canteen are studied. The investigation applied a cross-sectional study design. A structured questionnaire is administered following a pretest, and the data collected are analyzed using “SPSS v.20.” The review on morbidity record showed that the leading infections so far are respiratory (47%), gastrointestinal (amoebiasis, giardiasis, and typhoid) (34%), and eye and skin infections (16%). Regarding the responses to the knowledge questions, 1451 (60.8%) were correct while 934 (39.2%) were incorrect. Concerning handwashing as knowledge question, significant difference (p≈0.00) existed between genders. Over 50% of the respondents do think parasitic infections typically amoeba is acquired not due to the contaminated vegetables, but rather they assume that such vegetables trigger those parasites already lodging in their gut. Above 60% of the respondents agreed that sharing drinking cups as a sign of affection as unfavorable attitude. In relation to that, the students’ attitude highly varies by gender. However, the responses on hygiene practice enquiries appear to be promising. Further, the students do some practice while not having the desired level of knowledge on hygiene. Generally, there is a considerable gap in the knowledge, attitude, and practice of hygiene among students