Biodiesel Production From Candlenut And Calodendrum Capense Seeds: Process Design And Technological Assessment

Abstract

This project was based on biodiesel production from candlenut and calodendrum capense seeds using conventional and biotechnological technique and determination of the oil yields and biodiesel quality. The driving force for large-scale use of biodiesel has been the need to reduce the harmful emissions that result from the burning of petroleum oil as well as our dependence on diminishing reserves of petroleum oil. The aim of the study was to extract oil from Candlenut tree and Calodendrum capense seeds using conventional techniques and determine conditions for optimum oil yields. The oil from the two non-edible plant feedstocks was obtained using soxhlet solvent extraction and mechanical screw pressing machine at Kenya Industrial Research Institute (KIRDI). The preliminary tests like the acid value, viscosity, density, iodine value and calorific value were done to ascertain the quality of the oil. Transesterification was done using methanol and potassium hydroxide as a catalyst. The use of enzyme as a catalyst in transesterification was done using lipase enzyme cultured from Lake Bogoria water. Lipase-catalyzed transesterification of candlenut oil and calodendrum capense oil using methanol for biodiesel production in amyl alcohol and t-butanol alcohol was investigated. The optimum conditions for transesterification were investigated. Infrared spectroscopy was used to ascertain the efficiency of the acid catalyzed transesterification process. Thin Layer Chromatography was also used in the case of enzymatic transesterification. The engine performance tests of B5 and B20 for both candlenut and calodendrum capense were also investigated. The engine tests parameters investigated; brake specific fuel consumption, thermal efficiency, brake horse power and exhaust temperature were compared to commercial diesel. The oil yield for candlenut seeds varied from 32.3% to 35.4% and for calodendrum capense seeds, the oil content was 35.2%. Factors which govern transesterification process such as the quantity of the catalyst, reaction time, speed, temperature and amount of methanol used were investigated and optimum conditions determined (temperature of 65˚C, one hour reaction time, rotation speed of 1100rpm, 6:1 molar ratio of methanol to oil and optimum potassium hydroxide catalyst). For lipase enzymes catalyzed transesterification, it was observed that 6 ml of t-butanol alcohol, 6:1 molar ratio of methanol to oil, 2ml of lipase catalyst, temperature 45˚C, 150 rpm and 24hrs yielded the highest biodiesel conversion of 92.6%. Overall, the lipase catalyzed transesterification method yielded higher conversion in comparison to acid catalyzed transesterification (64.8 to 72.1%) diesel to obtain B5, B10, B20 and B100. The Infrared spectrum for the methyl esters gave a significant peak at 1720 cm-1 and it was also similar to that obtained for fossil diesel. The physical properties studied for biodiesel and the blends for both candlenut and calodendrum capense were similar to those of diesel fuel. The neat candlenut oil was found to have a high iodine value of 136.5g I2/g oil but the methyl esters were within the allowed limits of 115g I2/100g oil and 120g I2/100g oil as per ASTM D6751 and EN 14214 respectively. The kinematic velocities for B100 biodiesel for both candlenut and calodendrum capense were comparable to those of the blends (B5, B10, B20) and the diesel fuel. The kinematic velocities decreased with increase in temperature from 15 to 60˚C. The acid value for neat biodiesel (B100) and the blends for both candlenut and calodendrum capense were found to be within the allowed maximum limit of 0.8mgKOH/g as per ASTM D664. The calorific values increased with the decrease in the biodiesel percentage in the blends. The calorific value for B5 calodendrum capense (42.2MJ/Kg) and candlenut (41.5MJ/Kg) were the highest and close to the value obtained for diesel fuel (43.4MJ/Kg). The flash point decreased with the decrease in the biodiesel percentage in the blends with the B5 for both candlenut and calodendrum capense being close to that of diesel fuel. The specific engine consumptions of the biodiesel blends as well as diesel oil decreased with increasing load from 5.593 to 33.570 KW and tended to increase with further increase in brake horse power. The thermal efficiency for B5 candlenut blend increased from 12.64% at BHP 5.59 KW to maximum 32.27% at BHP 27.96 KW and started decreasing. There was an increase in the thermal efficiency for both B5 and B20 calodendrum capense blends. For both B5 and B20 candlenut and calodendrum capense blends the exhaust temperature increased with brake horse power. The amount of oil that was obtained from mechanical extraction of both the plant seeds promotes planting more hence obtaining alternative fuel and conserving the environment. The results on physical properties of the biodiesel for both the candlenut and calodendrum capense and those of the fossil diesel showed similarities. The lipase catalyzed transesterification gave a high yield of methyl esters which promotes the green chemistry and reduction of environmental pollution resulting on use of alkali catalysts. The engine tests results for B5 and B20 blends for candlenut and calodendrum capense showed that biodiesel obtained from these two plants can be used in a diesel engine without any modification hence serve as alternative fuel.