Comprehensive Study on Biodiesel Produced from Waste Animal Fats-A Review

This present study focus on the process optimization and characteristic assessment of waste animal fat (WAF) biodiesel based on the influence of fatty acids characterized in it. WAFs were rendered from leather fleshing (subcutaneous fat, 85.64%) and slaughterhouse (intramuscular fat, 8.46%) wastes using dry rendering technique, wherein the maximum renderable fat content was found to be 75.77% and 5.89%, respectively. Ethyl esters of oleic acid, palmitic acid, and stearic acid were characterized as dominant fatty acid esters (FAEs) in WAF biodiesel. Optimized transesterification on waste fats using ethanol and synthesized D-valine amido ethyl methyl imidazolium chloride ([D-Vaemim]Cl) as novel ionic liquid (IL) catalyst yielded 97.36% of biodiesel. High molar ratio (WAF to ethanol:6) and reaction temperature (75°C) were accounted by the long-chain fatty acids in triglyceride molecules and their higher degree of saturation, respectively, meanwhile, [D-Vaemim]Cl exhibited high conversion yield beyond 10% and was effective up to 10 cycles. Similarly, biodiesel properties were evaluated as per ASTM D6751 standards, were found to be in acceptable range, and were deeply influenced by carbon chain length and degree of unsaturation in FAE molecules. Also, the presence of long-chain saturated FAEs along with fuel bound oxygen induced superior combustion characteristics and controlled emission concentrations. However, slight reduction in engine performance was due to high viscosity and reduced calorific value of biodiesel which was reflected from its FAE molecules.

This work reports the potential of novel non-edible seed oil of Lepidium perfoliatum Linn. (LSO) for accessing its potential to synthesize biodiesel using zirconium-modified montmorillonite clay catalyst. The newly synthesized zirconium-modified clay catalyst (ZrO-Mmt) was characterized using by X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray Spectroscopy (EDX), and Fourier transfer Infrared spectroscopy (FT-IR) spectroscopy. Response surface methodology (RSM) was used to optimize the Lepidium biodiesel (LBD) yield. Maximum biodiesel yield (88%) achieved under optimized reaction conditions were 1:15 oil: methanol, 3.5% catalyst amount at135°C for 4h respectively. Different techniques like FTIR, GC/MS, ¹H-NMR, and ¹³C-NMR were used for characterizing LBD. Additionally, major fuel properties of LBD for instance kinematic viscosity (4.10 mm²/s), density (0.8212kg/L), cloud point (−8 °C), flash point (74°C), and pour point (−9°C) agree well with the international biodiesel standards. Overall, Lepidium perfoliatum Linn. seed oil and ZrO-Mmt clay catalysts appear to be cheap, stable, and highly active contenders for the biodiesel industry.