Benson B. Gathitu

Due to increased environmental pollution as a result of high emission rates from agro-processing industries, the effluents must be cleaned up before being released into the environment. This study outlines the use of green algae for nutrient removal from agro-processing effluents discharged from three agro-industries (namely coffee, dairy, and tannery) in Kenya and how they can be used for the propagation of microalgae for biofuel production. Green algae were grown inside a photobioreactor containing the three agro-industrial effluents as nutrient media for 21 days. Thereafter, the algae were harvested and evaluated for biofuel production. The effectiveness of green algae (chlorella ssp) to extract the cations from the various agro-processing effluents was used to gauge how well they performed. Additionally, the algae growth rate, quantity of lipids, and biomass generated were used to evaluate the strains' effectiveness in producing biofuel. The results indicate that the highest maximum algae growth rate of 14.528 mg/mL occurred in the dairy effluent. The corresponding values for the coffee and tannery effluents were 13.016 mg/mL and 10.866 mg/mL, respectively. Biochemical analysis was done to establish the amount of biomass in the algae. The results showed that there was higher biomass productivity per day of 293.944, 124.849, and 91.997 μg/mL for the dairy, coffee, and tannery effluents, respectively. The contents of linolenic acid in the chlorella strain in the dairy, coffee, and tannery effluents were 13.21, 12.86, and 15.98%, respectively. The values obtained were slightly above the recommended lower limit value of 12% (EN 14214, 2004) for the production of quality biofuels. The results further show that high chemical oxygen demand removal (maximum of 47.7–67.8%) and total phosphorus removal (maximum of 95%) were achieved in all three effluents. Finally, the fatty acid methyl ester profiles produced indicated that the lipid content of the cultivated green algae was appropriate for the production of biofuel.

The growing need for energy and the emphasis on reducing emissions have brought attention to the importance of developing renewable energy sources, specifically biofuels. However, using vegetable oils directly in diesel engines is hindered by their high viscosity, low ability to evaporate, and high content of polyunsaturated fats. Nanoemulsions, which are created without traditional surfactants, have demonstrated remarkable thermodynamic stability. This offers a potential solution to the challenges encountered with biofuels. This paper aimed to study the system of rapeseed oil-ethanol and 1-heptanol to understand the effects these nanoemulsions have on the calorific value and flash point. Ternary fuel blends with varying amounts of ethanol, rapeseed oil, and 1-heptanol were studied at constant weight percentages of 20% 1-heptanol and 30% rapeseed oil. The calorific value was determined by using a bomb calorimeter, and the results show that increasing the amount of 1-heptanol and rapeseed oil was able to increase the calorific value of the blend and maintain it close to that of diesel fuel. The flash point was determined using the Pensky Martens Closed Cup Method according to the American Society for Testing and Materials D93 standard (ASTM Standard D93-02a, 2002), and results show that only blends at 20% and 30% 1-heptanol at a constant of 30% rapeseed oil complied with the flash point requirement for diesel. This finding highlights the potential of the tricomponent fuel being used in an internal combustion engine without modification to the engine. The improved calorific value and flash point of the blends could be attributed to the co-solvent behaviour of 1-heptanol on rapeseed oil and ethanol.

A Flash geothermal-solar hybrid cycle is analyzed numerically when it is operated using different workings. The studied working fluids (n-butane, n-pentane, Cyclopentane, Hexamethyldisiloxane, and Toluene) have a low global warming potential and zero ozone depletion potential. These working fluids were investigated to determine the net power output and pump power when heated using low quality geothermal brine from the separator at Olkaria II power plant in Kenya. The brine was heated from a temperature of 158.9 o C to a higher temperature of 400 o C using a parabolic trough solar collector. In addition, analysis was done to determine how Therminol VP1 fluid pressure and flow rate affected the power output of the Organic Rankine Cycle. Furthermore the pressure and mass flow rate of the brine were adjusted to determine how these affected the net power output of the system. In comparison to other working fluids such as n-pentane, Cyclopentane, Hexamethyldisiloxane (MM), and Toluene, nbutane (R600) demonstrated the highest results in net power output for this hybrid system. As a result, it was chosen as the suitable working fluid for this hybrid system. The impact of Therminol VP1 fluid flow rate and pressure on organic working fluid performance revealed that for this system to generate more power, flow rates should be kept low, around 0.2 kg/s, and pressures should be kept slightly below or equal to 11 bar. As compared to Therminol VP1, the brine pressure and flow rate exhibits opposite behavior.