Improvements in the stability of biodiesel fuels: recent progress and challenges

Fewer fossil fuel deposits, price volatility, and environmental concerns have intensified biofuel-based studies. Saccharification, gasification, and pyrolysis are some of the potential methods of producing carbohydrate-based fuels, while lipid extraction is the preferred method of producing biodiesel and green diesel. Over the years, multiple studies have attempted to identify an ideal catalyst as well as optimize the abovementioned methods to produce higher yields at a lower cost. Therefore, this present study comprehensively examined the factors affecting biodiesel stability. Firstly, isomerization, which is typically used to reduce unsaturated fatty acid content, was found to improve oxidative stability as well as maintain and improve cold flow properties. Meanwhile, polymers, surfactants, or small molecules with low melting points were found to improve the cold flow properties of biodiesel. Meanwhile, transesterification with an enzyme could be used to remove monoacylglycerols from oil feedstock. Furthermore, combining two natural antioxidants could potentially slow lipid oxidation if stainless steel, carbon steel, or aluminum are used as biodiesel storage materials. This present review also recommends combining green diesel and biodiesel to improve stability. Furthermore, green diesel can be co-produced at oil refineries that are more selective and have a limited supply of hydrogen. Lastly, next-generation farming should be examined to avoid competing interests in food and energy as well as to improve agricultural efficiency.

Effect of Mixed Commercial Cold Flow Improvers on Flow Properties of Biodiesel from Waste Cooking Oil

The uniform design method was used to screen the solidifying point depressing effects of 18 traditional diesel cold flow improvers on biodiesel derived from waste cooking oil. The cold flow improvers with good effects were selected for orthogonal optimization. Finally, the mixed cold flow improver (CFI) with the best depressing effect was selected to explore its depressing mechanism for biodiesel. The results show that the typical CFIs such as A132, A146, 10-320, 10-330, A-4, CS-1, AH-BSFH, Haote, T1804D, and HL21 all have a certain solidifying point depressing effect on biodiesel, while other cold flow improvers had no obvious effect. Amongst them, 10-330 (PMA polymer) and AH-BSFH (EVA polymer) had better solidifying point depressing effects over others, both of which reduced the solidifying point (SP) of biodiesel by 4 °C and the cold filter plugging point (CFPP) by 2 °C and 3 °C, respectively. From the orthogonal mixing experiment, it can be seen that the combination of 10-330 and AH-BSFH at a mass ratio of 1:8 had the best depressing effect, reducing the solidifying point and cold filter plugging point of biodiesel by 5 °C and 3 °C, respectively. Orthogonal analysis showed that when used in combination, AH-BSFH had a greater impact on the solidifying point, while the ratio of the combination had a greater impact on the cold filter plugging point.

Microbial biodiesel production from oil palm biomass hydrolysate using marine Rhodococcus sp. YHY01

The effect of various biomass derived inhibitors (i.e. furfural, hydroxymethylfurfural (HMF), vanillin, 4-hydroxy benzaldehyde (4-HB) and acetate) was investigated for fatty acid accumulation in Rhodococcus sp. YHY 01. Rhodococcus sp. YHY01 was able to utilize acetate, vanillin, and 4-HB for biomass production and fatty acid accumulation. The IC₅₀ value for furfural (3.1mM), HMF (3.2mM), vanillin (2.0mM), 4-HB (2.7mM) and acetate (3.7mM) was calculated. HMF and vanillin affect fatty acid composition and increase saturated fatty acid content. Rhodococcus sp. YHY 01 cultured with empty fruit bunch hydrolysate (EFBH) as the main carbon source resulted in enhanced biomass (20%) and fatty acid productivity (37%), in compression to glucose as a carbon source. Overall, this study showed the beneficial effects of inhibitory molecules on growth and fatty acid production, and support the idea of biomass hydrolysate utilization for biodiesel production by avoiding complex efforts to remove inhibitory compounds.