Bioconversion approach for the valorization of Jatropha curcas seed cake into biodiesel using black soldier fly (Hermetia illucens) larvae

The aim of this study was to assess the biodiesel potential of black soldier fly larvae (BSFL)-fed Jatropha curcas seed cake (JCSC). The larvae were fed with JCSC that had undergone three different treatments (biological, thermal, and thermobiological) and an untreated control group. Every 4 days for 15 days, the larvae were fed treated and untreated JCSC at a rate of 90 g of JCSC per 550 larvae. The highest survival rate (98.42 ± 1.21%) was obtained with untreated JCSC. The oil content of larvae from each treatment was 32.86 ± 0.42% for untreated JCSC and 31.84 ± 0.67%, 32.16 ± 0.17%, and 31.43 ± 0.19% for biologically, thermally, and thermobiologically treated JCSC, respectively. The oil extracted from larvae from untreated JCSC (with the highest fat content) was converted to biodiesel by a two-step transesterification process. Fatty acid methyl esters were identified using gas chromatography/mass spectrometry (GC/MS) analyses. Furthermore, the nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FT-IR) analyses of BSBL oil showed the presence of carboxylic acids and ester carbonyl functional groups. In addition, the physicochemical properties of biodiesel from BSFLO were analyzed, and properties such as density (875.5 kg/m³), flash point (154 °C), iodine value (94.48 gI₂/100 g oil), calorific value (39.87 MJ/kg), cetane number (52.53), and induction time (14.57 h) were all within the standards set by ASTMD6751.