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The use of non-oil Jatropha biomass in the energy mix as a solid fuel offers the most effective ways of utilising such resource. However, available information indicates that biomass has negative inherent properties which lower its fuel value. This negative effect can be improved by slow pyrolysis process called torrefaction where the biomass is heated in the range of 200 °C to 300 °C. In the present investigation the effects of torrefaction temperature on the solid fuel value of different Jatropha biomass materials were determined. Consequently, three types of Jatropha biomass namely; seed cake, stem and fruit cover were considered under five temperature levels (200 °C, 225 °C, 250 °C, 275 °C, 300 °C). Analysis of Variance (ANOVA) revealed that there were significant differences (P > 0.05) in bulk density, hygroscopicity, energy content and ultimate etc. The statistical analysis results indicated that there was biomass type and torrefaction temperature interaction effects on the ultimate analysis, bulk density, hygroscopicity, energy content and energy yield. The interaction effects of the factors under investigation were not observed in mass yield. Increase in torrefaction temperature generally reduced the equilibrium moisture content and volatile matters across the biomass types. However fixed carbon, carbon content, ash content and energy density were increased across the biomass types as the temperature was increased from 200 °C to 300 °C. The torrefied Jatropha seed cake biomass showed relatively enhanced fuel characteristics than the torrefied stem and the torrefied fruit husk when considering the properties under investigation., (© 2020 Published by Elsevier Ltd.)

The quality of a feedstock in biodiesel production is of paramount importance, and Jatropha seed oil is no exception. This study investigates the influence of the fruit maturity stage on the physicochemical properties of Jatropha seed oil and the derived biodiesel. Free fatty acid content, peroxide value, moisture content, density, and kinematic viscosity are some of the important quality parameters of oil and biodiesel. Results from this investigation have revealed that free fatty acid content and peroxide value of seed oil varies as Jatropha fruits mature from green to brown dry. The free fatty acid content in Jatropha seed oil increases continuously with seed maturity following the three-order polynomial trend. The free fatty acid content in Jatropha seed oil from the investigated geographical locations in Botswana ranges from 0.2 to 0.7% for the four different fruit maturity stages. Similarly, the peroxide value of Jatropha seed oil increases gradually and linearly with fruit maturity. The peroxide value of Jatropha seed oil ranges from 1.2 to 3.7 mEq/kg oil, while that of derived biodiesel ranges from 2.1 to 4.4 mEq/kg oil during the four different fruit maturity stages. However, the variation of density and kinematic viscosity of both Jatropha seed oil and derived biodiesel with fruit maturity is insignificant. Moisture content in Jatropha seeds varies as fruits mature from green to brown dry., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

Seed oil production in Jatropha seeds through different maturity stages have been investigated. In order to meet the high demand of oil (feedstock) for large scale biodiesel production, increasing oil content or output in Jatropha seeds is required. Jatropha fruits were harvested at four different maturity stages and the seeds were analysed for oil content. The seed oil was analysed for fatty acid profile. Results from four different geographical locations investigated namely; Mmadinare, Thamaga, Maun and Shashe, have shown a similar trend in lipid accumulation in Jatropha seeds as the fruits mature from green to brown dry. However, maximum oil content in seeds varies with geographical location. Accumulation of oil in Jatropha seeds during maturation follows a parabolic trend and reaches its peak when fruits are yellow. Oil yield in Jatropha seed kernels ranges from 38.7% to 45.8% for the four maturity stages investigated. Overall results have revealed that harvesting Jatropha fruits when they are yellow increases seed oil output by 6-9% when compared to harvesting the fruits when they are brown dry. There is a relationship between the trend in fatty acid composition in Jatropha seed oil and seed oil content trend during fruit maturation. Based on the trend of unsaturated fatty acids in Jatropha seed oil, particularly linoleic and oleic acids, it can be deduced that reduction of seed oil content from yellow brown to brown dry stage is a result of breakdown of some of the unsaturated fatty acids., (© 2020 The Authors.)