Utilization of coconut meal, a waste product of milk processing, as a novel substrate for biodiesel and bioethanol production

Coconut meal, a waste product left after coconut milk processing, was collected and utilized as raw substrate for biofuel production. Biofuel production was produced via two steps. Biodiesel was first produced from coconut meal’s oil. Afterward, bioethanol was produced by Saccharomyces cerevisiae, using coconut waste after oil extraction as the sole carbon source. In this study, oil extraction methods, including chill and centrifugation, fermentation, and dry processing, were determined. The highest yield was obtained from dry processing (42.2%). The moisture and free fatty acid content of waste coconut oil (WCO) was 0.1% and 0.3–0.5%, respectively. Therefore, WCO was favourable to use as a substrate for biodiesel production. The highest biodiesel yield (98.1%) was observed from an alkali catalyst. Fuel properties of biodiesel from WCO met the biodiesel standard of the USA (ASTM D6751-07) and Europe (EN 14214). Thereafter, solid coconut waste (SCW) after oil extraction was collected and pre-treated using 50% NaOH. Cellulose content (62.1%) significantly increased after alkali pre-treatment. Thereafter, pre-treated SCW was hydrolysed with cellulase derived from Trichoderma viride and Aspergillus niger. Glucose (20.3 g/L) was a major end product in enzymatic hydrolysate. SCW hydrolysate was utilized as fermentation medium without nutritional supplementation. The production of ethanol constantly increased and reached 8.5 g/L (equivalent to 82.4% of theoretical yield) after 60 h.