Andrew C. Eloka-Eboka

Hybridization of feedstocks—A new approach in biodiesel development: A case of Moringa and Jatropha seed oils

ABSTRACT In this study, two selected feedstocks, Moringa oleifera and Jatropha curcas seed oils, and their methyl esters (biodiesel) were subjected to two new different hybridization processes at varying proportions experimentally. The hybrid compositions were J50M50, J40M10, J30M20, J20M30, and J10M40 from crude oil samples (in situ) and BM50J50, BM40J10, BM30J20, BM20J30, and BM10J40 from produced biodiesel by transesterification (ex situ) using production variables and optimization sequences. The hybrids were evaluated for chemo-physical and thermal properties using American Society for Testing and Materials and South African National Standards standards for each specific test(s). Results obtained revealed the efficacy of hybridization in improving the specific biodiesel properties as fuels. Specific tests include viscosity, specific gravity, refractive index, cetane index, fatty acid composition, free and total glycerine (TG), free fatty acid (FFA) composition, flash point, pour and cloud points, and calorific values. These were all higher and better than the single-stock biodiesel fuels. Moringa oleifera biodiesel, which was proved an excellent biodiesel fuel in the previous studies of the authors having high oleic acid content (>70%), impacted positively on Jatropha in enhancing its potential, with positive correlation at a 95% confidence level (α > 0.05) and on analysis of variation (ANOVA). This is a new approach in biodiesel development as studies of this nature are scarce in the literature.

Fuel properties comparison of species of microalgae and selected second-generation oil feedstocks

Comparative investigation and assessment of microalgal technology as a biodiesel production option was studied alongside other second generation feedstocks. This was carried out by comparing fuel properties of species of Chlorella vulgaris, Duneliella spp., Synechococus spp. and Senedesmus spp. with the feedstock of Jatropha (ex-basirika variety), Hura crepitans, rubber and Natal mahogany seed oils. The microalgae were cultivated using a photo-bioreactor (New Brunsink set-up model BF-115 Bioflo/CelliGen made in the USA) with operating parameters: 14 l capacity, working volume of 7.5 l media, including 10% inoculum, at optical density of 3.144 @ 540 nm and light intensity of 200 lux, for 23 and 16 days respectively. Various produced/accumulated biomasses were harvested by draining, flocculation, centrifugation and drying, and then subjected to lipid extraction processes. The oils extracted from the algae and feedstocks were characterised and used to produce biodiesel fuels, by the transesterification method, using a modified optimisation protocol. The fuel properties of the final biodiesel products were evaluated for chemo-physical and fuel properties. Results revealed Chlorella vulgaris as the best strain for biomass cultivation, having the highest lipid productivity (5.2 mgl−1h−1), the highest rate of CO2 absorption (17.85 mgl−1min−1) and the average carbon sequestration in the form of CO2 was 76.6%. The highest biomass productivity was 35.1 mgl−1h−1 (Chlorella), while Senedesmus had the least output (3.75 mgl−1h−1, 11.73 mgl−1min−1). All species had good pH value adaptation, ranging from 6.5 to 8.5. The fuel properties of the microalgal biodiesel in comparison with Jatropha, rubber, Hura and Natal mahogany were within ASTM specification and AGO used as control. Fuel cultivation from microalgae is feasible and will revolutionise the biodiesel industry.

Investigation into the Electrical Conductivity of Carbon Nanosphere-Based Green Nanofluids

Electrical conductivity measurements of green nanofluids prepared from carbon nanospheres dispersed in 60:40 ethylene glycol and water (60:40 EG/W) based nanofluids have been studied. In order to investigate the effect of temperature and volume concentration on the electrical conductivity of the nanofluids, the temperature was varied from 15 to 60 °C and volume fractions of 0.04, 0.1, 0.12, and 0.2 vol% were used. The results show that the electrical conductivity is greatly enhanced with an increase in temperature and volume fraction. The highest enhancement is seen at 0.2 vol% with 1470% increase in electrical conductivity. The high conductivity enhancement indicates a potential for cooling applications.

Fabrication of Affordable and Sustainable Solar Cells Using NiO/TiO2 P-N Heterojunction

The need for affordable, clean, efficient, and sustainable solar cells informed this study. Metal oxide TiO2/NiO heterojunction solar cells were fabricated using the spray pyrolysis technique. The optoelectronic properties of the heterojunction were determined. The fabricated solar cells exhibit a short-circuit current of 16.8 mA, open-circuit voltage of 350 mV, fill factor of 0.39, and conversion efficiency of 2.30% under 100 mW/cm2 illumination. This study will help advance the course for the development of low-cost, environmentally friendly, and sustainable solar cell materials from metal oxides.

Performance and Emission Profile of Micro-Algal Biodiesel in Compression Ignition Engine

Micro-algae are a large and diverse group of simple typically autotrophic organisms which have the potential to produce greater amounts of non-polar lipids and biomass than most terrestrial biodiesel feedstocks. Having emerged as one of the most promising sources for biodiesel production, they are gaining research interests in the current energy scenario due to their phenomenal growth potential (< 21 days log phase) in addition to relatively high lipids production which are also excellent source of biodiesel. In this study, engine performance and emission profile was performed using biodiesel fuels and blends from micro-algal technology in a compression ignition engine. The technology of micro-algae involved open pond cultivation and the use of photo-bioreactor model BF-115 Bioflo/celli Gen made in the US of 14 litre capacity (200 Lux light intensity) and flowrate of 2.5L/min. The micro-algal species used were Chlorella vulgaris and Scenedesmus spp. The biodiesel produced were blended with conventional diesel (AGO) at different proportions. The performance parameters evaluated include: engine power, torque, brake specific fuel consumption (BSFC), smoke opacity, thermal gravimetry, thermal efficiency, exhaust gas temperatures and lubricity while the varying effects of emission pollutants during combustion were also studied. Results showed that viscosity, density and lubricity have significant effects on engine output power and torque than when throttled with AGO which was used as control. Combustion efficiency and emission profile were better than the AGO due to the oxygenated nature of the micro-algal biodiesel which brought about complete combustion. A striking deduction arrived is that oxygen content of the algal biodiesel had direct influence on smoke opacity and emissions in the engine and also thermo-gravimetrically stable for other thermal applications. The engine tests (BSFC, BTE, ThE, MechE, EGT) and overall emissions (CO2, CO, VOCs, HC, SOx, NOx) were within acceptable limits and comparable with AGO. The implication of the study is that Micro-algal technology is feasible and can revolutionise development in biodiesel industry.

Thermal energy conservation strategy: A case of a modified local charcoal stove utilisation

The proliferation and use of charcoal stoves is on the increase even in urban locations in Africa despite the environmental hazard associated with charcoal production. The rising cost of fossil fuel, the smokeless nature of charcoal combustion and probably inexistent or ineffective legislation against deforestation could be the reasons for this. This study aims at more efficient use of the energy available from the use of common charcoal stoves. A common slightly improved charcoal stove was placed in an enclosure with openings for air inflow and heating of the pot, and linked to a heat receiver through a duct all made of burnt brick. The stove enclosure, heat receiver inlet and outlet, and the ambient temperatures were measured during the boiling of water for 3 periods/stages of 22 minutes per day for 6 days. The quantity of heat generated in the enclosure, the percentage reaching the heat receiver and the total heat losses from the system were computed under steady state conditions. A mean value of 93.85 kJ/kg of heated air was generated in the enclosure with about 34.33% reaching the heat receiver. The mean temperature within the heat receiver was 70.4 °C and the mean total heat loss from the system was about 6.4 kJ/kg of air. There was a significant difference between the thermal energy lost and trapped within and amongst the three stages; (p ≤ 0.05) and significant also with time for the three stages and within the stages of operation (p ≤ 0.05) with positive correlation of total heat lost and the heat trapped for conservation. This significantly indicates great potentials for utilising part of the thermal energy generated from the use of charcoal stoves for cooking as losses for other alternative uses such as drying and other forms of preservation of foodstuff thereby improving their utilisation efficiency and probably compensating in part for the adverse effect on the environment as a result of sustained charcoal production. This is an eye-opener situation in the quest for total energy conservation and conversion in any energy system.