Browsing by Author "Menya, E."
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Item Biogas as an alternative to fuelwood for a household in Uleppi sub-county in Uganda(Agric Eng Int: CIGR Journal, 2013-01-24) Menya, E.; Alokore, Y.; Ebangu, B. O.Over 93% of Uganda’s population relys on wood fuel in form of either charcoal or fuelwood for cooking. Uleppi sub-county in Arua district is a typical example of such areas in Uganda where households entirely use fuelwood to meet their energy demand for cooking. The use of fuelwood is however associated with the use of inefficient stoves that accelerate deforestation thus increasing carbon dioxide (CO2) emissions. The use of fuelwood is also associated with a smoky environment that has adverse health impacts on women and children who spend long hours in the kitchen. In addition, women and children spend long hours gathering fuelwood which significantly reduces farm productivity. This project was therefore aimed at design and construction of a biogas plant ideal for a household in Uleppi sub-county as an alternative to fuel wood. The research involved sizing of the floating drum biogas digester and gasholder, economic analysis as well as estimating CO2 emission reduction. For a household with an average of three heads of cattle managed in a free range system, the biogas digester and gasholder were sized as 1.4 m3 and 0.29 m3 respectively with 0.48 m3 of biogas produced per day. At this capacity, it was found that biogas utilization can reduce individual household consumption of wood fuel by 66.32% for a household size of five persons. The carbon emission reduction for all households was estimated at 432 tons of CO2 per year. The benefit-cost ratio was found to be 3.26, hence worthy to invest in the biogas technology. The capital recovery period for 459 USD of the biogas plant installation with an economic life of 15 years at 23 % interest rate was found to be two years.Item Experimental evaluation of rice husk ash for applications in geopolymer mortars(Keai publishing, 2021-02-26) Ogwanga, G.; Olupot, P.W.; Kasedde, H.; Menya, E.; Storz, H.; Kiros, Y.Rice husks obtained from upland and lowland rice varieties were characterized by the composition and content of ash. Each of the rice husk varieties was fired at temperatures of 600, 800, and 900 °C for a soaking period of 3 h. The resultant rice husk ash was analyzed for oxide composition and crystallinity using X-ray fluorescence and diffraction techniques, respectively. The generated amorphous ash with the highest silica content, together with metakaolin, aggregate, water, and an alkaline activator was employed to formulate geo-polymer mortar prisms according to the standard EN 196–1. Results showed that the content of ash in the varieties ranged from 18.3% to 28.6% dry basis. Out of this, 89 wt%–96 wt% was silica, with amorphous and crystalline forms of silica obtained at 600 °C and 900 °C, respectively, regardless of the rice variety. However, at 800 °C, the silica in the generated ash exhibited both amorphous and crystalline forms. The amorphous ash generated at 600 °C was used in the formulation of geopolymer mortars. The compressive and flexural strength of the formulated mortar after 7 days of curing was 1.5 and 1.3 MPa, respectively. These results reveal the firing protocol to form pozzolanic ash, with potential applications in mortar production.Item Investigating the effect of different loading densities on selected properties of dried coffee using a GHE dryer(CIGR Journal, 2023-09) Menya, E.; Komakech, A. J.Despite coffee being one of the leading cash crops in Uganda contributing 20%-30% of the total export earnings, it is mainly dried on bare earth surfaces hence its drastic decline in quality. A possible alternative solution is the utilization of the greenhouse effect (GHE) solar dryer. This research was aimed at investigating the effect of different loading densities on selected properties of dried coffee using a GHE dryer that was designed and constructed at Makerere University Agricultural Research Institute Kabanyolo (MUARIK). The research involved determining the drying time for the loading densities of 5, 10 and 20 kg m-2 as well as analyzing the coffee quality at the end of the drying period. Three experimental runs were set up in the months of June and July which experienced an average ambient temperature of 23.28 (±2.33)oC and an average dryer temperature of 35.68 (±13.85)oC. The average drying time for the freshly harvested Robusta coffee at 61.3 (±1.36)% wb was 10 days for 5 kg m-2, 11 days for 10 kg m-2 and 12 days for 20 kg m-2. The loading of 20 kg m-2 resulted in an even roast with fair+ for body and flavour, while 5 and 10 kg m-2 loadings resulted in a silver skin roast with fair body and flavour. For this particular research, the loading density of 20 kg m-2 yielded the best results from the coffee quality analysis. The loading densities of 5 kg m-2 and 10 kg m-2 could not yield the best results due to case hardening of the outer surfaces of the coffee beans which compromised the body and flavour of the coffee.Item Optimization of pyrolysis conditions for char production from rice husks and its characterization as a precursor for production of activated carbon(Springer, 2019-03-13) Menya, E.; Olupot, P. W.; Storz, H.; Lubwama, M.; Kiros, Y.; John, M. J.Response surface methodology was employed to optimize pyrolysis conditions for the production of char with maximum yield, fixed carbon content, and minimum ash content from Uganda’s New Rice for Africa (NERICA) 1 rice husk variety. The aim was to obtain rice husk char with more suitable properties as an activated carbon precursor. Mathematical models were developed to explain the relationships between the experimental responses and the pyrolysis parameters of temperature (400–600 °C), heating rate (10–25 °C min−1), and heating period (60–120 min). The optimized rice husk char was further characterized for elemental and proximate compositions, thermal behaviour, specific surface area, as well as surface functional groups. Results from the analysis of variance (ANOVA) revealed that the quadratic model best fits each of the responses. Pyrolysis temperature had the greatest influence on each of the responses, followed by heating period, and lastly heating rate. Optimum pyrolysis conditions were found to be temperature (406 °C), heating rate (10 °C min−1), and heating period (60 min), resulting in char yield, fixed carbon, and ash contents of 35.26, 55.39, and 35.01% dry basis, respectively. Compared to raw rice husk, the resulting rice husk char was found more suited as activated carbon precursor, due to its enriched carbon content (60.35%) and specific surface area (123.9 m2g−1). Thermogravimetric analysis of the rice husk char revealed that thermal activation temperatures were higher than 400 °C may be required to considerably devolatilize the char, forming a more porous activated carbon.Item Optimization of pyrolysis conditions for char production from rice husks and its characterization as a precursor for production of activated carbon(Springer, 2019-03-13) Menya, E.; Olupot, P. W.; Storz, H.; Lubwama, M.; Kiros, Y.; John, M. J.Response surface methodology was employed to optimize pyrolysis conditions for production of char with maximum yield, fixed carbon content, and with minimum ash content from Uganda’s New Rice for Africa (NERICA) 1 rice husk variety. The aim was to obtain rice husk char with more suitable properties as an activated carbon precursor. Mathematical models were developed to explain the relationships between the experimental responses and the pyrolysis parameters of temperature (400–600 °C), heating rate (10–25 °C min−1), and heating period (60–120 min). The optimized rice husk char was further characterized for elemental and proximate compositions, thermal behavior, specific surface area, as well as surface functional groups. Results from the analysis of variance (ANOVA) revealed that the quadratic model best fits each of the responses. Pyrolysis temperature had the greatest influence on each of the responses, followed by heating period, and lastly heating rate. Optimum pyrolysis conditions were found to be temperature (406 °C), heating rate (10 °C min−1), and heating period (60 min), resulting in char yield, fixed carbon, and ash contents of 35.26, 55.39, and 35.01% dry basis, respectively. Compared to raw rice husk, the resulting rice husk char was found more suited as activated carbon precursor, due to its enriched carbon content (60.35%) and specific surface area (123.9 m2 g−1). Thermogravimetric analysis of the rice husk char revealed that thermal activation temperatures higher than 400 °C may be required to considerably devolatilize the char, forming a more porous activated carbon.Item Production and performance of activated carbon from rice husks for removal of natural organic matter from water:(Elsevier, 2017-11-02) Menya, E.; Olupot, P.W.; Storz, H.; Lubwama, M.; Kiros, Y.Adsorption by activated carbon has great potential to improve natural organic matter (NOM) removal from water. However, the high production and regeneration costs limit its wide scale application. To address these limitations, research efforts have been focused on finding low-cost materials that can be transformed into activated carbon. Rice husk is one of such material of research focus, especially in developing countries, where over 96% of rice husks are generated globally. Although numerous investigations have been made concerning the production of activated carbon from rice husks, the existing scientific information still remains widely scattered in the literature. Furthermore, the scientific information regarding the performance of rice husk-activated carbon during NOM removal from water still remains poorly documented. This review article, therefore, provides ample information on efforts made by various researchers concerning the production of activated carbon from rice husks and its adsorption performance in relation to NOM removal from water. The properties and pretreatment of rice husks in relation to the production of activated carbon are discussed. Activation of rice husks by physical and chemical methods under numerous conditions is reviewed. Factors affecting NOM adsorption by activated carbon are briefly discussed. The adsorption performance of rice husk activated carbon is also reviewed with respect to NOM removal from water, and where possible compared with other source-derived activated carbons. The data from the literature revealed that NOM removal by rice husk activated carbon can be as effective as commercial activated carbon. Consequently, rice husk-activated carbon has the potential to serve as an alternative to commercial-activated carbon.Item Synthesis and evaluation of activated carbon from rice husks for removal of humic acid from water(Springer, 2020-11-26) Menya, E.; Olupot, P. W.; Storz, H.; Lubwama, M.; Kiros, Y.Activated carbon was synthesized from the New Rice for Africa (NERICA) rice husk variety, followed by its evaluation for removal of humic acid from water. Product values of carbon yield, C and total specific surface area, as,BET were employed as the performance criterion. The best physically activated carbon resulted from char activation at 800 °C for 10 min, leading to as,BET and C×as,BET values of 756.8 and 402.7 m2 g−1, respectively. The best chemically activated carbon resulted from 30 wt% H3PO4 activation of rice husk at 400 °C for 30 min, leading to as,BET and C×as,BET values of 2258.4 and 1058.7 m2 g−1, respectively. Despite the higher as,BET value, the maximum adsorption capacity of the best chemically activated carbon (5.3 mg g−1) was found lower than 8.9 and 27.2 mg g−1 exhibited by the chemically activated carbons prepared at 500 and 600 °C, respectively. The best adsorption conditions included carbon dose of 0.5 g, solution pH of 2, and contact time of 60 min. The adsorption capacity of the prepared activated carbons (27.2 mg g−1) was comparable to that of the commercial activated carbon (30.40 mg g−1). The analyses of the adsorption isotherms and kinetics revealed that the experimental data fits well the Langmuir isotherm model, as well as the pseudo-second-order kinetic model. The latter suggests that the adsorption of humic acid onto the activated carbon was controlled by the chemisorption process. Overall, the study revealed that the NERICA rice husk variety has good prospects for preparation of activated carbons for humic acid adsorption.