Browsing by Author "Menya, E."
Now showing 1 - 5 of 5
Results Per Page
Sort Options
Item Assessment of pollution levels resulting from biomass gasification(Journal of Environmental Chemical Engineering, 2014) Menya, E.; Olwa, J.; Hagstrom, P.; Okure, M.In biomass gasification process the producer gas generated can be cleaned by water scrubbing. Some of the organic compounds generated are entrained together with other flue gas dust particles in to the cooling stream. The treatment / disposal of this waste stream remains a challenge because some of the compounds are toxic to humans and the environment. The objective of this study was to assess pollution levels resulting from organic constituents of flue gas filtration in a downdraft gasifier. The study involved assessment of the con- centration of polycyclic aromatic hydrocarbons (PAHs) in the liquid effluence. The impacts on human health and environment are also discussed and recommendations on measures to minimize the pollution levels are provided. A downdraft gasifier fed with maize cobs was used and condensates were collected by cooling of producer gas. Samples were preserved in a cooler at about 2 ◦C for 24 h before analysis using a capillary gas chromatographer connected to a mass spectrometer (GC–MS). The results were that concentrations of: naphthalene was 204.3 mg / m 3 , benzene 17.92 mg / m 3 , toluene 182.94 mg / m 3 , ethylbenzene 202.43 mg / m 3 , 1,2-dimethyl benzene 359.28 mg / m 3 and 1,3 + 1,4-dimethyl benzene 1016.18 mg / m 3 . It was observed that the concentrations of naphthalene and xylene were considerably higher than the recommended permissible exposure limits (PELs) on both human health and the environment. On the other hand, the concentrations of benzene, toluene, and ethylbenzene were below the PEL. Generally this study indicated that the liquid effluent meets regulatory standards, but it would be interesting to carryout tests with different biomass fuel types which this study recommends.Item Biogas as an alternative to fuelwood for a household in Uleppi sub-county in Uganda(Agricultural Engineering International: CIGR Journal, 2013) 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 Design of waste stabilization ponds for dairy processing plants in Uganda(CIGR Journal, 2013) Menya, E.; Wangi, G. M.; Amanyire, F.; Ebangu, B.Waste stabilization ponds (WSP) were designed to treat 287.5 m3 day-1 of wastewater generated from processing of 100 m3 of milk per day. The design involved use of existing models including those developed by Mara to size the anaerobic, facultative and maturation ponds. The design temperature was 250C. The anaerobic pond was designed based on volumetric organic loading rate while facultative pond was designed based on surface loading rate. On the other hand, the maturation pond was designed based on the number of coliform bacteria removed per 100 mL of wastewater. The anaerobic pond was designed to remove 70% BOD, facultative pond-75% and maturation pond-25% BOD. In addition, the maturation pond was designed to have a coliform bacteria removal efficiency of at least 99%. The total land requirement for anaerobic pond was estimated at 945.19 m2, facultative pond-6361.54 m2 and three maturation ponds-2709.06 m2. To cater for pond operation and maintenance, an additional 25% land was incorporated resulting into 1.25 hectares as the total land area required for pond construction, operation and maintenance. Besides treatment of wastewater to reduce BOD, remove pathogens and other pollutants, the use of WSP can result into high economic benefits through recycling of wastewater for agriculture and aquaculture. As a result, the payback period for the investment cost may also be shortened.Item Experimental Evaluation Of Rice Husk Ash For Applications In Geopolymer Mortars(Journal of Bioresources and Bioproducts, 2021) Ogwang, G.; Olupot, P.W.; Kasedde, H.; Menya, E.; Storz, H.; Kiros, Y.Rice husks obtained from upland and lowland rice varieties were characterized for 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 formulation of geopolymer mortars. 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(Agric Eng Int: CIGR Journal, 2013) 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 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 average ambient temperature of 23.28 (±2.33)oC and 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 into an even roast with fair+ for body and flavour, while 5 and 10 kg m-2 loadings resulted into 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 best results due to case hardening of the outer surfaces of the coffee beans which compromised the body and flavour of the coffee.