Water hyacinth, E. crassipes, an invasive water weed thrives in fresh water bodies causing serious environmental problems. In Kenya the weed has invaded Lake Victoria and poses great socioeconomic and environmental challenges. Currently the weed is harvested from the Lake and left in the open to rot and decay leading to loss of aesthetics, land and air pollution. There is therefore need for development of value addition and economic exploitation strategies. The aim of the study is to assess the potential for utilization of the weed as a renewable energy resource for biogas production. Samples were collected from Lake Victoria, pulped and blend with cow dung at a ratio of 3:1 as inoculum. The resultant mixture was mixed with water at a ratio of 1:1 and fed into a 6 m 3 tubular digester. The digester was recharged with 20 kg after every three days. The temperature, pH variations, gas compositions, upgrading and gas yields were studied. The temperature ranged between 22.8˚C-36.6˚C and pH 7.4-8.5. Biogas was found to contain 49%-53% methane (CH4), 30%-33% carbon dioxide (CO2), 5%-6% nitrogen (N2) and traces of hydrogen sulphide (H2S). The biogas was upgraded using solid adsorbents and wet scrubbers increasing the methane content by up to 70%-76%. The upgraded gas was used to power internal combustion engines coupled with an electricity generator and direct heat applications. The study concludes that E. crassipes is a potential feedstock for biogas production especially in areas where it is abundant.

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Abstract:The rapid increase in population in Thika has led to increase in municipal solid waste generation, which has posed challenges in the waste disposal and management. This study was carried out to quantify and characterize the waste generated within Thika municipality. Six months data (between March 2014 and August 2014) of waste stream at the dumpsite was reviewed and analyzed. The survey indicated that 66.95% ± 0.34% of the total waste dumped originated from the municipal council of Thika (MCT). It constitutes of domestic, commercial and institutional waste. 33.05% is industrial waste. Sixty eight percent (68%) of the waste consisted primarily of four components: paper, plastic, organics and food. Food accounted for 15.51% ± 0.95%, paper 18.31% ± 1.7%, plastics 17.89% ± 0.81% and organics other than food 16.51% ± 1.01%, respectively obtained at 95% confidence level. Each of the components has some level of recovery. Some of the reusable and recyclable materials were being recovered, food waste had the highest recovery rate of 23% ± 1.7% and was used as animal feed, while plastic (soft plastic) 17% ± 0.93% was sold to recyclers. Recovery of materials for recycling and composting was estimated at 10.21 tonnes or 11.35% of daily generation, leaving 76.44 tonnes per day that can be converted into useful energy. The study shows waste in this dumpsite can be exploited to by converting it to energy thus a good solution for waste management.

Wind turbine rotors capture energy from moving wind, their capacity to perform this function depends on the coefficient of power (Cp) of the rotor. Through proper aerodynamic design, a rotor's performance can be optimized to take advantage of the smallest available wind speed at any time to produce energy. In this research a computational fluid dynamics simulation was performed to model the best optimum dimensions of an inversely tapered rotor blade using Clark Y airfoil type rotor of 0.6 m diameter. The optimal design values obtained include; tip speed ratio (TSR) of 2.5, lift coefficient to drag coefficient ratio of 1.1 and pitch angle of 8 degrees Using blade element momentum (BEM), the wing profile of each section of the blade was calculated and designed. The unique inverse tapering was done to achieve a better efficiency at the low wind speed range. This was used to fabricate a three blade rotor using carbon composites which was tested in the wind tunnel for Cp. Results showed very good performance of the inverse tapered type as compared with the tapered rotors. The maximum coefficient of power for the inversely tapered was found to be 0.313 at 8 m/s. Visualization test and particle image velocimetry (P.I.V). analysis showed that the inversely tapered rotor is more effective in converting wind power into shaft power than the tapered.