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.

Automated summary

This study comprehensively examines the factors affecting biodiesel stability. The results show that isomerization can improve the oxidative stability and cold flow properties of biodiesel. Polymers, surfactants, or small molecules with low melting points can also improve its cold flow properties. Enzymatic transesterification can remove monoacylglycerols from oil feedstock. Furthermore, combining natural antioxidants can slow lipid oxidation, especially when storing biodiesel in materials such as stainless steel, carbon steel, or aluminum. The study also recommends combining green diesel and biodiesel to improve stability, and co-producing green diesel at oil refineries with limited hydrogen supply.