A facile noncatalytic methyl ester production from waste chicken tallow using single step subcritical methanol: Optimization study

In this modern era, an increase in urbanization causes the escalating trend of fuel demand as well as environmental pollution problems. Various biofuels research with the respect of climate change and emission reduction recently intensifies, particularly in biodiesel. In Indonesia, diesel oil currently in use contains 20% of biodiesel. Utilizing waste‐based resources such as rendered chicken tallow as the feedstock could be the solution to both energy and environmental challenges. However, chicken tallow contains a significant amount of free fatty acid (FFA) which will obstruct the production yield of biodiesel. In this study, catalyst‐free subcritical methanol has been employed to convert waste chicken tallow (WCT) with high FFA into biodiesel. Design of experiment was conducted to study the effect of temperature, time, and the molar ratio of methanol to fats on the purity and recovery of fatty acid methyl esters (FAMEs). Based on the optimization study performed by response surface methodology (RSM), all three independent variables gave a significant effect on the recovery of FAME. From the experimental results, the maximum FAME yield obtained was 98.43 ± 0.22% with the optimum condition as follows: 167°C, 36.8 minutes, and 42.7:1 (methanol/WCT, mol/mol), while the predicted FAME yield obtained using RSM was 97.76%. The methyl ester composition of WCT‐based biodiesel ranges from C13 to C24.     

Biodiesel production from olive–pomace oil of steam-treated alperujo

Recently interest has been revived in the use of plant-derived waste oils as renewable replacements for fossil diesel fuel. Olive–pomace oil (OPO) extracted from alperujo (by-product of processed olives for olive oil extraction), and produced it in considerable quantities throughout the Mediterranean countries, can be used for biodiesel production. A steam treatment of alperujo is being implemented in OPO extraction industry. This steam treatment improves the solid–liquid separation by centrifugation and facilitates the drying for further extraction of OPO. It has been verified that the steam treatment of this by-product also increases the concentration of OPO in the resulting treated solid, a key factor from an economic point of view. In the present work, crude OPO from steam-treated alperujo was found to be good source for producing biodiesel. Oil enrichment, acidity, biodiesel yield and fatty acid methyl ester composition were evaluated and compared with the results of the untreated samples. Yields and some general physicochemical properties of the quality of biodiesel were also compared to those obtained with other oils commonly used in biodiesel production. As for biodiesel yield no differences were observed. A transesterification process which included two steps was used (acid esterification followed by alkali transesterification). The maximum biodiesel yield was obtained using molar ratio methanol/triglycerides 6:1 in presence of sodium hydroxide at a concentration of 1% (w/w), reaction temperature 60 °C and reaction time 80 min. Under these conditions the process gave yields of about 95%, of the same order as other feedstock using similar production conditions.     

Oxidation stability of biodiesel derived from high free fatty acid feedstock

At present, with fluctuating feedstock prices, the biodiesel manufacturing industries are facing some downfall. High free fatty acid (FFA) non-edible oil, which is a byproduct of vegetable oil refineries, is available at low price and in considerable quantities at vegetable oil refinery sites. This high FFA oil can be utilized as a potential low cost feedstock for biodiesel production. In the present work, high FFA (51.6%) oil was synthesized into biodiesel by a two-step process. Except oxidation stability, other fuel properties of the produced biodiesel were found to be comparable with that of biodiesel specifications. Oxidation stability was found to be only 2.1 h at 110°C as determined by the Rancimat apparatus.

In order to study and further improve the oxidation stability, the biodiesel (B100) was dosed with a suitable antioxidant (pyrogallol) and stored for 6 months. The acid value, peroxide value, and kinematic viscosity which are closely associated with oxidation behavior were studied. It was found that biodiesel dosed with an antioxidant showed the least increase in the acid value, peroxide value, and kinematic viscosity. Also, induction period was improved and found to be within the American Society for Testing and Materials limit . Thus, the high FFA oil-based biodiesel with a suitable antioxidant can be used as a potential feedstock to resolve the issue of the high cost of biodiesel production.     

Production and evaluation of biodiesel from mixed castor oil and waste chicken oil

Biodiesel was developed from an unconventional feedstock, i.e. an equivalent blend of castor bean and waste chicken oil through the alkaline-catalyzed transesterification with methanol. The process variables including the alkaline catalyst concentration, methanol to oil molar ratio, reaction temperature, reaction time, and the alkaline catalyst type were investigated. The highest yield of biodiesel (97.20 % ~ 96.98 % w/w ester content) was obtained under optimum conditions of 0.75 % w/w of oil, 8:1 methanol to oil molar ratio, 60°C temperature, and a duration of 30 min. Properties of the produced biodiesel satisfied those specified by the ASTM standards. The results thus indicated that the suggested blend oils are suitable feedstock for the production of biodiesel. The process was found to follow pseudo first-order kinetics, and the activation energy was found to be 8.85 KJ/mole.     

Pumpkin (Cucurbita pepo L.) seed oil as an alternative feedstock for the production of biodiesel in Greece

In recent years, the acceptance of fatty acid methyl esters (biodiesel) as a substitute to petroleum diesel has rapidly grown in Greece. The raw materials for biodiesel production in this country mainly include traditional seed oils (cotton seed oil, sunflower oil, soybean oil and rapeseed oil) and used frying oils. In the search for new low-cost alternative feedstocks for biodiesel production, this study emphasizes the evaluation of pumpkin seed oil. The experimental results showed that the oil content of pumpkin seeds was remarkably high (45%). The fatty acid profile of the oil showed that is composed primarily of linoleic, oleic, palmitic and stearic acids. The oil was chemically converted via an alkaline transesterification reaction with methanol to methyl esters, with a yield nearly 97.5 wt%. All of the measured properties of the produced biodiesel met the current quality requirements according to EN 14214. Although this study showed that pumpkin oil could be a promising feedstock for biodiesel production within the EU, it is rather difficult for this production to be achieved on a large scale.     

Biodiesel production by transesterification of duck tallow with methanol on alkali catalysts

Duck tallow was employed as a feedstock for the production of biodiesel by transesterification with methanol. The content of fatty acid methyl ester (FAME) was evaluated on various alkali catalysts during transesterification. The composition and chemical properties of the FAME were investigated in the raw duck tallow and the biodiesel products. The major constituent in the biodiesel product was oleic acid. The FAME content was 97% on KOH catalyst in the reaction. It was acceptable for the limit of European biodiesel qualities for BD100. Acid value, density, and kinematic viscosity of the biodiesel products also came up to the biodiesel qualities.     

High free fatty acid coconut oil as a potential feedstock for biodiesel production in Thailand

Coconut oil having 12.8% free fatty acid (FFA) was used as a feedstock to produce biodiesel by a two-step process. In the first step, FFA level of the coconut oil was reduced to 0.6% by acid-catalyzed esterification. In the second step, triglycerides in product from the first step were transesterified with methanol by using an alkaline catalyst to produce methyl esters and glycerol. Effect of parameters related to these processes was studied and optimized, including methanol-to-oil ratio, catalyst concentration, reaction temperature, and reaction time. Methyl ester content of the coconut biodiesel was determined by GC to be 98.4% under the optimum condition. The viscosity of coconut biodiesel product was very close to that of Thai petroleum diesel and other measured properties met the Thai biodiesel (B100) specification.     

Biodiesel production from swine manure via housefly larvae (Musca domestica L.)

Although biodiesel is a sustainable and renewable diesel fuel, the current feedstock predominantly from edible oils limits the economic feasibility of biodiesel production and thus the development of a cost-effective non-food feedstock is really essential. In this study, approximately 21.6% of crude grease was extracted from housefly (Musca domestica L.) larvae reared on swine manure, and the extracted grease was evaluated for biodiesel production concerning the variables affecting the yield of acid-catalyzed production of methyl esters and the properties of the housefly larvae-based biodiesel. The optimized process of 8:1 methanol/grease (mol/mol) with 2 vol% H₂SO₄ reacted at 70 °C for 2 h resulted in a 95.7% conversion rate from free fatty acid (FFA) into methyl esters. A 90.3% conversion rate of triglycerides (crude grease) to its esters was obtained from alkaline trans-esterification using sodium hydroxide as catalyst. The major fatty acid components of this larvae grease were palmitic (29.1%), oleic (23.3%), palmitoletic (17.4%) and linoleic (17.2%). The housefly larvae-based biodiesel has reached the ASTM D6751-10 standard in density (881 kg/m³), viscosity (5.64 mm²/s), ester content (96.8%), flash point (145 °C), and cetane number (52). These findings suggest that the grease derived from swine manure-grown housefly larvae can be a feasible non-food feedstock for biodiesel production.     

Free lipase-catalyzed biodiesel production from phospholipids-containing oils

Free lipase-catalyzed biodiesel has drawn more and more attentions in recent years because of its advantages of lower cost and faster reaction rate. Utilizing free lipase to convert low quality oils such as crude vegetable oils and microbial oils is beneficial to further reduce the cost of biodiesel production. However, these oils typically contain some amount of phospholipids. Phospholipids were found to affect the lipase-catalyzed process and further influence the enzyme's thermal stability in biodiesel production process. In this work, free lipase NS81006-mediated biodiesel production from oils containing phospholipids at varied temperature was investigated systematically. It was found that the presence of phospholipids at high temperature led to a decreased fatty acid methyl esters (FAME) yield and poor reuse stability of the lipase during NS81006-catalyzed biodiesel production process. The higher the temperature was, the greater negative effect was observed. This inhibitory effect was found to be mainly caused by the coexistence of phospholipids and methanol in the system. Based on this finding, a novel two-step enzyme-mediated process was further developed, with which the above-mentioned inhibitory effect was eliminated, and a FAME yield of 95.1% could be obtained with oils containing 10% phospholipids even at high temperature of 55 °C.     

Optimization of biodiesel production from camelina oil using orthogonal experiment

Camelina oil is a low-cost feedstock for biodiesel production that has received a great deal of attention in recent years. This paper describes an optimization study on the production of biodiesel from camelina seed oil using alkaline transesterification. The optimization was based on sixteen well-planned orthogonal experiments (OA₁₆ matrix). Four main process conditions in the transesterification reaction for obtaining the maximum biodiesel production yield (i.e. methanol quantity, reaction time, reaction temperature and catalyst concentration) were investigated. It was found that the order of significant factors for biodiesel production is catalyst concentration > reaction time > reaction temperature > methanol to oil ratio. Based on the results of the range analysis and analysis of variance (ANOVA), the maximum biodiesel yield was found at a molar ratio of methanol to oil of 8:1, a reaction time of 70 min, a reaction temperature of 50 °C, and a catalyst concentration of 1 wt.%. The product and FAME yields of biodiesel under optimal conditions reached 95.8% and 98.4%, respectively. The properties of the optimized biodiesel, including density, kinematic viscosity, acid value, etc., were determined and compared with those produced from other oil feedstocks. The optimized biodiesel from camelina oil meets the relevant ASTM D6571 and EN 14214 biodiesel standards and can be used as a qualified fuel for diesel engines.     

Effects of water on the esterification of free fatty acids by acid catalysts

To maximize the production of biodiesel from soybean soapstock, the effects of water on the esterification of high-FFA (free fatty acid) oils were investigated. Oleic acid and high acid acid oil (HAAO) were esterified by reaction with methanol in the presence of Amberlyst-15 as a heterogeneous catalyst or sulfuric acid as a homogeneous catalyst. The yield of fatty acid methyl ester (FAME) was studied at oil to methanol molar ratios of 1:3 and 1:6 and reaction temperatures of 60 and 80 °C. The rate of esterification of oleic acid significantly decreased as the initial water content increased to 20% of the oil. The activity of Amberlyst-15 decreased more rapidly than that of sulfuric acid, due to the direct poisoning of acid sites by water. Esterification using sulfuric acid was not affected by water until there was a 5% water addition at a 1:6 molar ratio of oil to methanol. FAME content of HAAO prepared from soapstock rapidly increased for the first 30 min of esterification. Following the 30-min mark, the rate of FAME production decreased significantly due to the accumulation of water. When methanol and Amberlyst-15 were removed from the HAAO after 30 min of esterification and fresh methanol and a catalyst were added, the time required to reach 85% FAME content was reduced from 6 h to 1.8 h.     

Biodiesel production using gel‐type cation exchange resin at different ionic forms

In this study, a strong acidic‐type cation exchange resin was used in the transesterification of corn oil to fatty acid methyl esters (FAME). The gel‐type cation exchange resin (Purolite‐PD206) was used in H⁺ and Na⁺ forms to utilize ion‐exchange resin as effective heterogeneous catalyst in the production of biodiesel. Effect of ionic forms of ion exchange resin on free fatty acid (FFA) conversion and composition was investigated by using different amounts of ion exchange resin (12, 16, and 20 wt%), various mole ratios of methanol to oil (1:6, 1:12, and 1:18 mol/mol), reaction temperatures (63, 65, and 67°C), and reaction time (24, 36, and 48 h) during transesterification reaction. The highest FFA conversions of 73.5% and 79.45% were obtained at conditions of 20 wt% of catalyst, 65°C of reaction temperature, 18:1 as methanol to oil ratio, and 48 h of reaction time for H⁺ and Na⁺ forms of ion exchange resin, respectively. These results were obtained from regression equations established by using analysis of variance (ANOVA) model according to the experimental results of selected parameters. Gas chromatography analysis revealed that FAME is mainly composed of C16:0 (palmitic), C18:1 (oleic), and C18:2 (linoleic) acids of methyl ester.     

Biodiesel production from oil-rich feedstock: A neural network modeling

Biodiesel produced from oil-rich feedstocks is known as a green replacement for conventional petroleum diesel. Transesterification is the common method used for biodiesel production. Hence, in this contribution, neural network modeling and least square support vector machine (LSSVM) modeling were used to predict the transesterification of castor oil with methanol to form biodiesel. Also, genetic algorithm was used for the optimization of predictive model. Input and output parameter of predictive models for the prediction of biodiesel production yield and estimation of the efficiency of biodiesel production are catalyst weight (C), methanol-to-oil molar ratio (MOR), time (S), temperature (T), and fatty acid methyl ester (FAME) yield, respectively. Proposed LSSVM modeling predicts biodiesel production yield or FAME yield within ±2% relative deviation with a high value of coefficient of determination (0.99583) and a low value of absolute deviation (1.27) in which the mentioned statistical parameters represent the accuracy and robustness of the model.     

Biodiesel production from mixture of mahua and simarouba oils with high free fatty acids

A suitable process comprising acid pretreatment followed by main base transesterification reaction was developed to produce biodiesel from mixture of Mahua (M) and Simarouba (S) oils with high free fatty acids (FFA). The acid pretreatment reduced the high FFAs of the mixture of oils to around 1% which were then transesterified with methanol and KOH as catalyst at a reaction temperature of 60 °C. A genetic algorithm coupled with artificial neural network (ANN-GA) model to obtain the best pretreatment process parameters for bringing down the FFA level of individual vegetable oils to around 1% was modified to include the wide range of oils and validated for mixtures of M and S oils. The quality of biodiesel produced was analyzed by gas chromatography (GC), which indicated above 90% ester conversion. The fuel properties of biodiesel were found to be comparable to diesel and were conforming to the latest biodiesel standards.     

Conversion of bio-solids (scum) from tannery effluent treatment plant into biodiesel

The search for a suitable low cost feedstock for the production of biodiesel has resulted in biodiesel being produced from bio-solids (scum) taken from the tannery effluent treatment facility. The effectively extracted oil was subjected to combined esterification and transesterification using an acid catalyst. The process was optimized for parameters like catalyst concentration, temperature, time, oil to methanol molar ratio and stirring rate. The result was the yield of 0.55 kg of biodiesel from 1 kg wet scum. The physicochemical properties of the produced biodiesel are in the acceptable range of fuel used in diesel engines. The paper also addresses the quality issues regarding minor components like heavy metals and aromatic contents.     

Biodiesel production from mahua (Madhuca indica) oil having high free fatty acids

A technique to produce biodiesel from mahua oil (Madhuca indica) having high free fatty acids (19% FFA) has been developed. The high FFA level of mahua oil was reduced to less than 1% by a two-step pretreatment process. Each step was carried out with 0.30–0.35 v/v methanol-to-oil ratio in the presence of 1% v/v H₂SO₄ as an acid catalyst in 1-hour reaction at 60°C. After the reaction, the mixture was allowed to settle for an hour and methanol–water mixture that separated at the top was removed. The second step product at the bottom was transesterified using 0.25 v/v methanol and 0.7% w/v KOH as alkaline catalyst to produce biodiesel. The fuel properties of mahua biodiesel were found to be comparable to those of diesel and conforming to both the American and European standards.     

The reuse of waste cooking oil and spent bleaching earth to produce biodiesel

Currently, semi-refined and refined vegetable oils are used as a feedstock in biodiesel production. However, criteria such as competition with conventional fossil fuel, economic reasons, shortage supply of food and its social impact on the global scale have somewhat slowed the development of the biodiesel industry. Spent bleaching earth is currently under-utilized by deposition in landfills with no attempt to recover the oil. In this study the waste oil adsorbed on spent bleaching earth, refined soybean oil, and waste cooking oil were evaluated as potential sources of biodiesel production in Iran. Different characteristics of the oil samples, such as fatty acid composition, peroxide, iodine, acid values, etc., were evaluated. A two-step esterification reaction using methanol was conducted to produce biofuel. Subsequently, physicochemical properties of produced biodiesel were analyzed. The oil content in spent bleaching earth was 19.3%, which was lowered to 3.7% using hexane as the solvent. Gas chromatography showed that palmitic, oleic, and linoleic acids were predominantly fatty acids, respectively, and the highest content of saturated acids belonged to waste cooking oil (24%). The acidity of 8.3% was obtained for the oil recovered from spent bleaching earth followed by waste cooking oil (3.6%) and refined soybean oil (0.1%). Totally, the specifications of all biodiesel produced were in the range defined by ASTM D6751 and EN 14214 standards. Since about 2000–3000 tones of spent bleaching earth residual oil is annually dumped and the amount of waste cooking oil produced yearly is 500,000 tones, there is a great potential for Iran to produce biodiesel from waste oils.     

Two-stage processes of homogenous catalysed transesterification of high free fatty acid crude oil of rubber seed

Biodiesel is a diesel replacement and renewable fuel that is manufactured from vegetable oils, animal fats or waste cooking oils. The production of biodiesel from edible oil is currently much more expensive than hydrocarbon-based fuel, due to the relatively high cost of edible oils. The cost of biodiesel can be reduced by using non-edible oils instead of edible oils. The purpose of the present study was to develop a method of esterification of non-edible oil like rubber seed oil (Hevea brasiliensis). The high free fatty acid content oil reacts quickly with alkaline catalysts to form soap, which prevents the separation of biodiesel and glycerol. A two-step process was used instead of the simple alkaline catalysed transesterification process. It consisted of an acid catalysed pre-processing followed by the usual alkaline catalysed process. The physical and chemical properties of biodiesel were analysed. The quantification of methyl esters were done by high-performance liquid chromatography.     

Biodiesel production from mixed soybean oil and rapeseed oil

The biodiesel (fatty acid methyl esters, FAME) was prepared by transesterification of the mixed oil (soybean oil and rapeseed oil) with sodium hydroxide (NaOH) as catalyst. The effects of mole ratio of methanol to oil, reaction temperature, catalyst amount and reaction time on the yield were studied. In order to decrease the operational temperature, a co-solvent (hexane) was added into the reactants and the conversion efficiency of the reaction was improved. The optimal reaction conditions were obtained by this experiment: methanol/oil mole ratio 5.0:1, reaction temperature 55 °C, catalyst amount 0.8 wt.% and reaction time 2.0 h. Under the optimum conditions, a 94% yield of methyl esters was reached ∼94%. The structure of the biodiesel was characterized by FT-IR spectroscopy. The sulfur content of biodiesel was determined by Inductively Coupled Plasma emission spectrometer (ICP), and the satisfied result was obtained. The properties of obtained biodiesel from mixed oil are close to commercial diesel fuel and is rated as a realistic fuel as an alternative to diesel. Production of biodiesel has positive impact on the utilization of agricultural and forestry products.     

Biodiesel production from residual oils recovered from spent bleaching earth

This work was to study technical and economic feasibilities of converting residual oils recovered from spent bleaching earth generated at soybean oil refineries into useable biodiesel. Experimental results showed that fatty acids in the SBE residual oil were hexadecenoic acid (58.19%), stearic acid (21.49%) and oleic acid (20.32%), which were similar to those of vegetable oils. The methyl ester conversion via a transesterification process gave a yield between 85 and 90%. The biodiesel qualities were in reasonable agreement with both EN 14214 and ASTM D6751 standards. A preliminary financial analysis showed that the production cost of biodiesel from SBE oils was significantly lower than the pre-tax price of fossil diesel or those made of vegetable oils or waste cooking oils. The effects of the crude oil price and the investment on the production cost and the investment return period were also conducted. The result showed that the investment would return faster at higher crude oil price.