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Biodiesel produced from waste cooking oil (WCO) is on the rise and inevitably leads to issues in managing glycerol waste. Due to the presence of colour, odour and other minor compounds, the refining costs for this type of glycerol are higher and uneconomical. The potential of biodiesel-derived glycerol waste (BDGW) obtained from WCO to produce the highly added product of docosahexaenoic acid (DHA), also known as omega-3 polyunsaturated fatty acid, via the marine microalga of Schizochytrium limacinum ATCC MYA-1381 under aerobic batch fermentation was investigated. Cell growth, as well as DHA production, were performed under various operating conditions, including aeration rates and BDGW concentrations. The effect of the substrate type on cell growth and DHA yield was evaluated. The optimum operating condition was obtained when the air flow of a 0.25 vvm and 50 g/L of the glycerol concentration was fed into the fermenter and maximum cell dry weight (11.40 g/L) and DHA yield (665.52 mg/g) were achieved. However, cell growth and DHA yield were not significantly different when S. limacinum was grown using various carbon sources. Successfully, it clearly demonstrates that the BDGW can be used as a cheap carbon source for DHA production via marine microalgae using aerobic batch fermentation.

Two different methods of production of bio-hydrogenated diesel (BHD), simply called green diesel from rice bran oil (RBO), were performed. In the first route, a direct hydrotreating reaction of RBO to BHD catalysed by Pd/Al2O3 was performed in a high-pressure batch reactor. Operating conditions were investigated as follows: catalyst loading (0.5 to 1.5% wt.), temperature (325 to 400 °C), initial hydrogen (H2) pressure (40 to 60 bar) and reaction time (30 to 90 min). The optimal condition was obtained at 1% wt catalyst loading, 350 °C, 40 bar H2 pressure and 60 min. Yields of crude/refined biofuels and BHD achieved were approximately 98%, 81.71% and 73.71%, respectively. In another route, transesterification together with hydrotreating reactions of rice bran methyl ester (RBME) to BHD was performed using the optimal conditions obtained from the first route. The amount of 98% crude biofuel was obtained and was equivalent to production yields of refined biofuel (85.71%) and BHD (68.51%). Furthermore, physical and chemical properties of both RBO/RBME green diesel were also considered following ASTM standard methods. In summary, both catalytic reactions were achieved in the range of a low-speed industrial diesel and were further recommended for BHD or green diesel production from RBO.

In this work, hydro-processing was used as an alternative route for producing bio-hydrogenated kerosene (BHK) from refined bleached deodorized palm oil (RPO) in the presence of a 0.5 wt% Pd/Al2O3 catalyst. The Box-Behnken Design was used to determine the effects of reaction temperature, H2 pressure, and reaction time in terms of liquid hourly space velocity (LHSV) on BHK production. The kerosene selectivity was used as the response for staticial interpretation. The results show that both temperature and LHSV produced significant effects, whereas H2 pressure did not. The optimal conditions were found to be 483 °C, 5.0 MPa, and 1.4 h−1 LHSV; these conditions provided approximately 57.30% kerosene selectivity and a 47.46% yield. The BHK product had a good heating value and flash point. However, the mass percentage of carbon and hydrogen was 99.1%, which is just below the minimum standard (99.5%), according to the carbon loss by the reaction pathway to form as CO and CO2. Water can be produced from the reaction induced by oxygen removal, which results in a high freezing point.