INFORM April 2025

inform April 2025, Vol. 36 (4) • 31

in the HDO of fatty biomass as well as the use of aqueous solutions in the HDO of waste cooking and algae oils containing appreciable amounts of water, are reviewed for the first time. Suggestions for future research in the field are formulated through critical comments at the end of the article.

Biodiesel

Purification Process

Ryan J. Stoklosa is a research chemical engineer and lead scientist for the USDA, Agricultural Research Service located in Wyndmoor, Pennsylvania. His research focuses on technologies to convert plant biomass into fuels and high value chemicals.

Equilibrium Based

Affinity Based

Membrane Based

Reaction Based

Bulk Liquid Membrane

Emulsion Liquid Membrane

Supported Liquid Membrane

Solvent Extraction Distillation

Supercritical Extraction

Ion Exchange

Reactive Distillation

Membrane Bioreactor

Adsorption

Ionic Liquids & DES

Water Washing

Organic Solvents

Silica Base

Carbon Base

Bio Base

of wastewater discharges. This paper reviews the conventional and emerging liquid membrane technologies such as the emulsion liq uid membranes and the bulk liquid membranes for biodiesel puri fication, highlighting their technical merits and environmental benefits. Over and above that, liquid membrane technology offers a promising solution for the efficient purification of crude biodiesel while minimizing the environmental impacts. Clean and sustainable methods to remove free fatty acids from biodiesel produced from used cooking oil through enzymatic ethanolysis Aljawish, A., et al. , Biomass and Bioenergy , 194, 107611, 2025. https://doi.org/10.1016/j.biombioe.2025.107611 The enzymatic transformation of used cooking oil (UCO) into biodiesel was conducted using liquid lipase from Thermomyces lang inosus in the presence of ethanol as a co-substrate at 40 °C without any prior refinement. High Performance Liquid Chromatography (HPLC), Gas Chromatography (GC), and acid value measurements were employed to monitor the transformation of triglycerides (TGs) into fatty acid ethyl esters (FAEEs) and intermediary products such as free fatty acids (FFAs), monoglycerides (MGs), diglycerides (DGs). According to the applied enzymatic process, the FAEE yield was almost 96 % with residual FFAs at 3 wt%. Three approaches (enzymatic, physical, and chemical) were tested to reduce residual FFAs to below 0.25 % according to the European standard EN 14214. From an environmental and economic standpoint, the treatment using the anion exchange resin Amberlyst® A26OH is recommended as a clean and sustainable process, given its ability to regenerate and reuse the resin several times without any loss of efficiency. Therefore, the novel low-cost resin Seplite® BD130 could remove all traces of impurities at the end of the biodiesel production process. After the purification process with Seplite® BD130, the biodiesel met the requirements of the European standard EN 14214. This process represents a positive step towards more sustainable biodiesel production.

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Biodiesel produced from plant-based oils continues to be a viable option to replace petroleum-based diesel. Transformation of plant oils to biodiesel is a well-established process. However, improve ments in fuel purity are still needed during biodiesel processing. The first article reviews conventional and novel liquid membrane separa tion technologies that improve the overall purity of biodiesel blends with a focus on technical merits and environmental benefits. The sec ond article discusses a novel purification process for biodiesel pro duced from waste cooking oils. In this work free fatty acid content of the biodiesel was reduced to meet acceptable levels using enzymatic processing with a liquid lipase from Thermomyces langinosus . The last article investigates the distillation of diesel-biodiesel blends and develops correlative models for each blend to meet specific proper ties (e.g. density, viscosity, etc.) as set forth by ASTM. Superiority of liquid membrane-based purification techniques in biodiesel downstream processing Abed, K.M., et al. , Renewable and Sustainable Energy Reviews , 207, 114911, 2025. https://doi.org/10.1016/j.rser.2024.114911 Biodiesel, a biodegradable and non-toxic diesel alternative from the esterification and transesterification processes, is a viable bioenergy option. However, the presence of impurities in crude bio diesel necessitates purification to meet the standard specifications for high engine performance. Several techniques for biodiesel puri fication have been proposed, and they can be conveniently catego rized based on the following: equilibrium, affinity, membrane, and reaction. Dry-washing methods have proven to be effective, though they generate a significant amount of waste. Additionally, water based purification methods generate a large volume of wastewater with adverse environmental effects. The oxygen content in bio diesel has led to problems such as moisture absorption, corrosion and high viscosity. More recent research works focusing on mem brane-based biodiesel purification techniques appear to be a prom ising alternative that offers high-quality fuel with lower volumes