Bio-diesel production of sunflower through sulphur management in a semi-arid subtropical environment.

Energy security is a prime focus of policy makers to support agriculture, industrialisation, and transportation. Due to limited conventional energy sources, there is a need to harness non-conventional energy sources. In this regard, one of the proposed approaches is using biomass (e.g. energy crops) to produce biofuel-a renewable source of energy. Sunflower has several agronomic features to be exploited for a renewable, non-conventional, and environment-friendly source of bioenergy. Sulphur (S) fertilisation holds key for realising sunflower potential for seed and oil yield. In response to variable S supply rates, here we compared and quantified sunflower yield (seed, oil, and biodiesel) and biodiesel quality according to the ASTM international standards. We used a combined approach of field experimentation and rigorous lab analysis. Firstly, in a field experiment laid out in randomised complete block design with split-plot arrangement, response of two local sunflower hybrids (FH-331 and FH-689) to four S supply rates (0, 25, 50, 75 kg S ha-1) was evaluated in terms of agronomic traits. Experimental data showed that fertilisation of S significantly influenced growth and yield (seed, oil) traits; the response was different between two hybrids which also interacted with S supply rate. FH-331 recorded the highest achene yield at S fertilisation of 75 kg S ha-1, whereas FH-689 recorded the highest achene yield at 50 kg ha-1; achene yield of FH-331 was 13.6% higher than FH-689. Compared to control, S at 75 kg S ha-1 increased oil yield of FH-331 by 22% whereas S at 50 kg ha-1 increased oil yield by 23% of FH-689. Seed samples were analysed for different biodiesel quality parameters. The ranges of all quality parameters of sunflower biodiesel such as viscosity, calorific values, acid value, iodine value, saponification value, cetane number, and pour point were in ASTM standard range. We conclude that sunflower is a promising and sustainable option for producing biodiesel, the potential of which can be increased by optimal S management under field conditions.