Production of 2G and 3G biodiesel, yeast oil, and sulfonated carbon catalyst from waste coconut meal: An integrated cascade biorefinery approach

Abstract

Waste coconut meal (CM) is rich in lignocelluloses and oils. For biorefinery of lignocelluloses, the successfully of the process is based on efficient use of feedstock. In this study, a novel integrated biorefinery concept was applied for efficient utilization of CM as feedstock to produce yeast oil, sulfonated carbon catalyst, and biodiesels. CM was subjected to dilute acid hydrolysis to obtain xylose-rich CM hydrolysate (XCMH) and post-hydrolysis CM solid residue (CMS). Rhodotorula mucilaginosa KKUSY14 fermented XCMH into yeast oil, achieving the oil yield of 0.21 g/g sugar (33.9 wt% oil content) and 40.1 g oil/kilogram CM. Effective sulfonated catalyst, derived from CMS via direct sulfonation, was successfully used in direct transesterification to convert oil-rich wet yeast and oil-rich CM into yeast-based (3G) FAME and CM-based (2G) FAME, reaching the FAME yield of 92.5% and 96.8%, respectively. Lauric, myristic, palmitic and oleic acids were primarily found in FAME. The predicted fuel properties of FAME based on fatty acid profiles showed good cold flow properties. This novel approach could open the gate towards a new route for sustainable production of multiple products through the waste-to-energy strategy.