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.

Solid concentration is considered as one of the most important parameters governing the anaerobic digestion process. In this present study, four solid concentration levels (10%, 15%, 20% and 25% of total solids), were tested to evaluate the effect on biogas production from rapeseed oil cake. Four laboratory scale batch reactors with 2 L volume were used for this study with a retention period of 30 days. The performance of reactors was assessed by quantifying the daily biogas production, cumulative biogas production and the degradation of total solids, volatile solids and COD. Biogas production was found to be maximum at a solid concentration of 20%, followed by 25%, 15% and 10%. The results obtained from the study were evaluated using Gompertz, modified Gompertz and Logistic models to determine the kinetic constants of the process. There were smaller differences between measured and predicted biogas production for rapeseed oil cake when using a modified Gompertz model compared with the other two models.

The present study aims at understanding the effects of fuel preheating on engine characteristics of waste animal fat-oil (WAF-O) biodiesel in a single-cylinder CI engine, with the preheating technique proposed as an effective means for enhancing the fuel properties. To understand the effects of the preheated fuel, the WAF-O biodiesel was preheated at 60, 80, 100 and 120 °C and tested along with neat diesel and unheated WAF-O biodiesel. For this purpose, biodiesel was produced from different animal wastes by means of KOH-assisted ethanol-based transesterification, reporting its maximum yield as 96.37 ± 1.8%, with significant distribution of unsaturated oleic acid, saturated palmitic acid and stearic acid. Upon evaluating its fuel characteristics as per ASTM D6751 standards, a rise in preheating temperature by 1 °C reduced the density and kinematic viscosity of WAF-O biodiesel by 0.383 kg/m³ and 0.025 mm²/s, respectively, and was explained by the weakening of intermolecular forces between its fatty acid ester molecules. Preheated samples reported superior combustion characteristics by exhibiting increased in-cylinder pressure (2.24%, on average) and heat release rates in addition to their shortened ignition delay (1–4 °CA). Furthermore, preheating of WAF-O biodiesel reduced its specific fuel consumption and increased its brake thermal efficiency by 7.86% (on average) and 9.23% (on average), respectively. However, higher preheating temperatures (>120 °C) resulted in increased fuel consumption owing to its varied flow characteristics. In addition to the changes in combustion characteristics, preheating WAF-O bio-diesel also resulted in reduced carbon monoxide, nitrous oxide and hydrocarbon emission by 13.88%, 7.21% and 26.94%, respectively, and increased carbon dioxide emission by 7.58%. Summing up, the enhancements in overall engine characteristics of preheated samples were accounted for by their improvised fuel injection characteristics due to their reduced density and viscosity, which ensured for their effective combustion.

Biodiesel is regarded as the most promising renewable biofuel which can satisfy the worldwide energy demand through its robust net energy output with less impact on environment and also an effective alternative or supplement for existing diesel fuel for powering Compression Ignition engines. This present study aims to compare the performance, combustion and emission characteristics of beef tallow biodiesel with its dominant fatty acid esters and their influence on these characteristics. Ethyl stearate, ethyl palmitate and ethyl oleate were identified as dominant fatty acid esters available in a composition of 14.78, 37.36 and 25.17%, respectively. Two set of samples were prepared for testing purpose and were classified as (i) blend samples and (ii) ester samples, with plain diesel as base fuel. The maximum cylinder pressure was found to be in the range between 67 and 71 bar for all the samples and heat release rate was found to be highest for B20 blend. Slight decrease in efficiency along with marginal increase in fuel consumption was a result of long chained fatty acid esters (stearate and oleate esters) whereas increase in CO₂ emission and decrease in NO_X emission were because of higher oxygen content, cetane number and degree of unsaturation in the ester molecule.

Reducing fossil fuel reliance is considered a great challenge for several progressive emerging economies. The development of alternative renewable fuels tends to improve energy security as well as diminish fuel supply vulnerability. This paper details an enhanced protocol intended for the manufacture of hemp biodiesel over two-stage base catalyzed transesterification from crude hemp oil (CHO). The estimation of fuel properties, along with the various spectrometric techniques like Gas Chromatography and Mass Spectrometry (GC-MS), Fourier Transform Infra-Red Spectrometry (FTIR), and Thermo Gravimetry-Differential Scanning Calorimetry/Derivative Thermogravimetry (TG-DSC/DTG) methodologies were used to properly assess the quality and quantity of hemp (Cannabis Sativa L.) biodiesel (HB). The density, kinematic viscosity, and cetane number of HB were found to be 876 kg/m³, 3.91 cSt, and 50, respectively. Since the estimated fuel properties fall well within the range of American Society for Testing and Materials (ASTM) standards, HB could be considered as a sustainable fuel alternative to conventional diesel. GC-MS results demonstrate that the HB contains unsaturated long-chain fatty acids like 9,15-Octadecadienoic acid methyl ester as dominant in the mixture. The FTIR spectrum of crude hemp oil and the synthesized biodiesel confirm the conversion of triglycerides in the CHO into methyl esters in the HB. The findings obtained from TG-DSC/DTG are in near agreement with the results of GC-MS and FTIR. It is therefore proven the hemp oil has abundant potential to be used as an inedible source for the manufacture of bio-diesel.