Biodiesel Production from Rubber Seed Oil by Transesterification Using a Co‐solvent of Fatty Acid Methyl Esters

Rubber seed oil (RSO) is a high‐potential feedstock for the production of biodiesel fuel (BDF) in Asia. Transesterification using fatty acid methyl esters (FAMEs) as co‐solvents was developed for BDF production from RSO with high content of free fatty acids (FFAs). The homogeneous system (FAMEs/triglyceride/methanol) was attained when the FAME content was more than 30 wt %. After esterification of RSO, the crude RSO obtained was transesterified with FAMEs as a co‐solvent. The quality of BDF with high FAME content satisfied the criteria of the EN 14214/JIS K2390 standards. These results suggest that FAMEs converted from FFAs can be applied as a co‐solvent and, thus, reused for BDF production.     

Methyl Esters (Biodiesel) from and Fatty Acid Profile of Gliricidia sepium Seed Oil

Increasing the supply of biodiesel by defining and developing additional feedstocks is important to overcome the still limited amounts available of this alternative fuel. In this connection, the methyl esters of the seed oil of Gliricidia sepium were synthesized and the significant fuel‐related properties were determined. The fatty acid profile was also determined with saturated fatty acids comprising slightly more than 35 %, 16.5 % palmitic, 14.5 % stearic, as well as lesser amounts of even longer‐chain fatty acids. Linoleic acid is the most prominent acid at about 49 %. Corresponding to the high content of saturated fatty acid methyl esters, cold flow is the most problematic property as shown by a high cloud point of slightly >20 °C. Otherwise, the properties of G. sepium methyl esters are acceptable for biodiesel use when comparing them to specifications in biodiesel standards but the problematic cold flow properties would need to be observed. The ¹H‐ and ¹³C‐NMR spectra of G. sepium methyl esters are reported.     

Comparison of Fatty Acid Methyl and Ethyl Esters as Biodiesel Base Stock: a Review on Processing and Production Requirements

Fatty acid methyl esters (FAME) were the first fatty acid esters to be introduced for use as biodiesel. However, there is a growing interest in the use of fatty acid ethyl esters (FAEE) in biodiesel. Both FAME and FAEE have their own unique advantages and disadvantages. These differences are ultimately attributable to the structural differences imparted by the alcohols used in their production. Sources of reactants as well as their safety issues, are a focus of this review. Also reviewed are the comparative characteristics and properties of both biodiesel types in terms of physicochemical features and performance. Processing requirements, reaction times and molar ratios of alcohol to oil, together with problems and drawbacks, are discussed. Recent developments on improving the yield of biodiesel, include mixing methanol and ethanol in the same reaction with ethanol acting as a co-solvent, and enzymatic methanolysis and ethanolysis are also highlighted.     

An Empirical Equation for Estimation of Kinematic Viscosity of Fatty Acid Methyl Esters and Biodiesel

Kinematic viscosity (µ) is an important physical property of fatty acid methyl esters (FAME) and biodiesel. In this work, the Martin's rule of free energy additivity is extended to cover the kinematic viscosity of saturated and unsaturated FAME commonly found in nature. The proposed model can also be extended to estimate kinematic viscosity of biodiesel. The kinematic viscosity of a FAME or a biodiesel can be easily estimated from its carbon number (z), number of double bonds (n_d) at different temperatures (T) without a prior knowledge of the viscosity of individual FAME. Both z_ave and n_d(ave) can be derived from its fatty acid composition. Thus, kinematic viscosity of biodiesel at temperatures between 20 and 100 °C and at atmospheric pressure can be estimated. The average absolute deviation (AAD) estimated at 20–100 °C for saturated, unsaturated FAME, biodiesels and biodiesel blends are 4.15, 3.25, 6.95 and 2.79 %, respectively. The biodiesels collected in this study (191 data points) have the z_ave and n_d(ave) between 14.10 and 17.96 and 0.21–1.54, respectively. The standard deviation was 0.249. The proposed model would be good for estimation of viscosity of biodiesel containing normal fatty acids, generally found in biodiesel feed stocks.     

A Predictive Correlation for Dynamic Viscosity of Fatty Acid Methyl Esters and Biodiesel

The viscosity of biodiesel, which is a mixture of fatty acid methyl esters (FAME), is an important physical property in the injection and efficient combustion. In this study, a simple correlation, with only one adjustable parameter, is proposed for predicting the viscosity of FAME and their mixtures (biodiesel) as a function of temperature. First, the adjustable parameter of the correlation is calculated for various FAME. The average absolute relative deviation (AARD) is obtained to be 0.97% for 226 data points. Second, the adjustable parameter of FAME is connected to the number of carbon atoms and the number of double bonds to build a predictive correlation for the calculation of viscosity. The AARD for 226 data points is obtained to be 2.28%. Third, the proposed model is employed to predict the viscosity of biodiesel without introducing any new adjustable parameter. To predict the viscosity of biodiesel, the average of the adjustable parameter is applied to the correlation. The AARD of 2.96% is obtained for 185 data points comprised of 23 different biodiesels. To better understand the ability of the correlation in the estimation of the viscosity of biodiesel and FAME, a comparison is made between the present correlation and a number of correlations available in the literature.     

Ultrasonic Pretreatment Transesterification for Solid Basic-Catalyzed Synthesis of Fatty Acid Methyl Esters

Generally, ultrasound irradiation is required throughout the reaction for fatty acid methyl esters (FAME, namely, biodiesel) production, which is energy-consuming and difficult to scale-up. In order to improve the industrial application of ultrasonic technology, a systematic study of ultrasonic pretreatment solid basic (Na₂SiO₃)-catalyzed transesterification for FAME production from cottonseed oil was carried out, and the effect of ultrasonic waves on the properties of Na₂SiO₃ catalyst was assessed by X-ray diffraction (XRD), Fourier transform Infrared (FTIR) and scanning electron microscopy (SEM) characterization of fresh and collected catalysts. An ultrasonic frequency of 30 kHz, ultrasonic power of 200 W and ultrasonic pretreatment irradiation time of 30 min was determined to guarantee a satisfactory degree of transesterification. The optimum production was achieved in the reaction system at 45 °C with methanol/cottonseed oil molar ratio 5:1, catalyst dosage 3% and stirring speed 350 rpm resulting in a FAME yield of above 97% after 60 min of reaction under mechanical stirring with the ultrasonic pretreatment process. The new process has a shorter reaction time, a more moderate reaction temperature, a less amount of methanol and catalyst than only the mechanical stirring process without essential damage to activity and the structure of catalyst. These results are of great significance for applying the ultrasonic pretreatment method to produce FAME.     

Branched‐Chain Fatty Acid Methyl Esters as Cold Flow Improvers for Biodiesel

Biodiesel is an alternative diesel fuel derived mainly from the transesterification of plant oils with methanol or ethanol. This fuel is generally made from commodity oils such as canola, palm or soybean and has a number of properties that make it compatible in compression‐ignition engines. Despite its many advantages, biodiesel has poor cold flow properties that may impact its deployment during cooler months in moderate temperature climates. This work is a study on the use of skeletally branched‐chain‐fatty acid methyl esters (BC‐FAME) as additives and diluents to decrease the cloud point (CP) and pour point (PP) of biodiesel. Two BC‐FAME, methyl iso‐oleate and methyl iso‐stearate isomers (Me iso‐C_18:1 and Me iso‐C_18:0), were tested in mixtures with fatty acid methyl esters (FAME) of canola, palm and soybean oil (CaME, PME and SME). Results showed that mixing linear FAME with up to 2 mass% BC‐FAME did not greatly affect CP, PP or kinematic viscosity (ν) relative to the unmixed biodiesel fuels. In contrast, higher concentrations of BC‐FAME, namely between 17 and 39 mass%, significantly improved CP and PP without raising ν in excess of limits in the biodiesel fuel standard specification ASTM D 6751. Furthermore, it is shown that biodiesel/Me iso‐C_18:0 mixtures matched or exceeded the performance of biodiesel/Me iso‐C_18:1 mixtures in terms of decreasing CP and PP under certain conditions. This was taken as evidence that additives or diluents with chemical structures based on long‐chain saturated chains may be more effective at reducing the cold flow properties of mixtures with biodiesel than structures based on long‐chain unsaturated chains.     

The Influence of Tocopherols on the Oxidation Stability of Methyl Esters

Tocopherols were found to be the principal natural antioxidants in biodiesel grade fatty acid methyl esters. The stabilising effect of α-, γ- and δ- tocopherols from 250 to 2,000 mg/kg was evaluated by thermal and accelerated storage induction times based on rapid viscosity increase, in sunflower (SME), recycled vegetable oil (RVOME), rapeseed (RME) and tallow (TME) methyl esters. Both induction times showed that stabilising effect is of the order of δ- > γ- > α-tocopherol, and that the stabilising effect increased with concentration. The correlation between the two induction times however was poor, which is probably due to the fact that the time they correspond to two different stages of oxidation. Tocopherols were found to stabilise methyl esters by reducing the rate of peroxide formation while present. The deactivation rates of tocopherols increased with unsaturation of the particular methyl ester and in the present work they were of the order of SME > RME > RVOME > TME. While α-tocopherol was found to be a relatively weak antioxidants, both γ- and δ- tocopherols increased induction times significantly and should be added to methyl esters without natural antioxidants.     

Esterification of Fatty Acids in Greases to Fatty Acid Methyl Esters with Highly Active Diphenylamine Salts

Diphenylamine sulfate (DPAS) and diphenylamine hydrochloride (DPACl) salts were found to be highly active catalysts for esterification and substantial transesterification of inexpensive greases to fatty acid methyl esters (FAME). In the presence of catalytic amounts of DPAS or DPACl and excess methanol, the free fatty acids as well as the acylglycerols in waste greases were converted to FAME at 125 °C within 1 h. Although the DPAS and DPACl catalysts were found to have similar catalytic activities to their parent liquid acids (i.e., sulfuric and hydrochloric acids) the diphenylammonium salts are much easier to work with than concentrated liquid acids.     

A Novel Method for the Production of Biodiesel from the Whole Stillage-Extracted Corn Oil

The extraction of corn oil from whole stillage and condensed distillers’ solubles (CDS) with hexane and its conversion to biodiesel were investigated. The analysis of the extracted oil showed 6–8 wt.% free fatty acid (FFA) in this oil. Acid, base, acid–base, and acid–base catalyzed transesterifications with intermediate neutralization with anion exchange resin were investigated. Experiments were performed with model corn oil substrates which contained 1.0–6.0 wt.% FFA. The effect of catalyst at 0.50–1.25 wt.% was studied at a 1:8 oil/methanol molar ratio. At 6.0 wt.% FFA concentration, the acid-catalyzed scheme was slow and resulted in less than 20% yield after 4 h, while the base-catalyzed was mostly consumed by the FFA and very little conversion was achieved. The acid–base catalyzed scheme succeeded in reducing the FFA content of the oil through the acid-catalyzed stage, and yields in excess of 85% were achieved after the second stage of the reaction with a base catalyst. However, formation of water and soap prevented the separation of product phases. An alternative acid–base catalyzed scheme was examined which made use of a strong anion exchange resin to neutralize the substrate after the initial acid-catalyzed stage. This scheme resulted in the effective removal of the acid catalyst as well as the residual FFA prior to the base-catalyzed stage. The subsequent base-catalyzed stage resulted in yields in excess of 98% for a 7.0 wt.% FFA corn oil and for the corn oil extracted from CDS.     

Removal and Degradation of Phorbol Esters during Pre-treatment and Transesterification of <Emphasis Type="Italic">Jatropha curcas</Emphasis> Oil

Phorbol esters present in Jatropha curcas oil are toxic when consumed and are co-carcinogens. These could be a potential constraint in the widespread acceptance of Jatropha oil as a source of biodiesel. Phorbol esters were quantified in the fractions obtained at different stages of oil pre-treatment and biodiesel production. During degumming some phorbol esters were removed in the acid gums and wash water. This implies that the use of these acid gums in animal feed is not possible and care should be taken when disposing the wash water into the environment. Silica treatment did not decrease the phorbol esters, while stripping/deodorization at 260 °C at 3 mbar pressure with 1% steam injection completely degraded phorbol esters. Phorbol esters were not detected in stripped oil, fatty acid distillate, transesterified oil (biodiesel) and glycerine. The presence of possibly toxic phorbol ester degradation products in these fractions could not be ruled out.     

Canola Quality Indian Mustard Oil (<Emphasis Type="Italic">Brassica juncea</Emphasis>) is More Stable to Oxidation than Conventional Canola Oil (<Emphasis Type="Italic">Brassica napus</Emphasis>)

Canola-quality Indian mustard (Brassica juncea) is being developed as a complimentary oilseed crop to canola (Brassica napus) for cultivation in hot and low-rainfall areas, where canola does not perform well. In Australia, several B. juncea breeding lines have been developed for commercial cultivation and for eventual processing as canola oil. However, there still are significant species-based differences in the fatty acid composition with B. juncea containing lower levels of linoleic acid and higher levels of oleic and linolenic acids compared with B. napus. This has raised concern about possible oxidative stability differences between the oils. Oils (unrefined) extracted from different breeding lines of each species were subjected to accelerated autoxidation, and development of oxidative rancidity was assessed by four separate techniques: depletion of polyunsaturated fatty acids, depletion of tocopherol, development of primary oxidation products, and development of secondary oxidation products (propanal and hexanal). All the tests showed that the newly developed B. juncea oils are more stable to autoxidation than conventional canola (B. napus) oil, despite containing marginally higher linolenic levels. Oxidative stability does not appear to be a barrier to using oils from these emerging lines of B. juncea for partial or full replacement of conventional canola oil.     

Solubilization of Acyl-CoA elongases from developing rapeseed (Brassica napus L.)

Acyl-CoA elongases are important in producing high-erucic acid rapeseed. The effects of Triton X-100,N-octyl-β-D-glucopyranoside and deoxycholate on the C18:1-CoA and C20:1-CoA elongase(s) have been studied by using a 15,000 ×g pellet from developing rapeseed. The synthesis of very long chain monounsaturated fatty acids (VLCMFA) and, in particular, that of erucic acid were stimulated by Triton X-100, whatever the substrate used. In the presence ofN-octyl-β-D-glucopyranoside, the elongase activity was practically unchanged, whereas deoxycholate strongly inhibited VLCMFA synthesis. Triton X-100 was chosen for the solubilization, at an optimal Triton X-100/protein (w/w) ratio of 2.5. Acyl-CoAs were the major products synthesized by the solubilized acyl-CoA elongase(s). The analysis of the reaction intermediates showed that the entire elongation complex has been solubilized and was still functional.     

Glucosinolate levels in cotyledons of mustard,Brassica juncea L. and rape,B. napus L. do not determine feeding rates of flea beetle,Phyllotreta cruciferae (Goeze)

Sinigrin (allyl glucosinolate), the major glucosinolate in the cotyledons ofBrassica juncea cv. Cutlass, occurred in the highest concentration and amount at seedling emergence and declined during growth. Glucobrassicin (3-indolylmethyl glucosinolate), the major glucosinolate in the cotyledons ofB. napus cv. Westar, occurred in the lowest concentration and amount at seedling emergence. The amount of glucobrassicin per cotyledon pair increased about fourfold during 14 days of growth, but its concentration remained relatively unchanged because of dilution by increasing cotyledon biomass. These different glucosinolate profiles indicate a different metabolic control and different biological function for sinigrin and glucobrassicin. The flea beetle,Phyllotreta cruciferae Goeze, does not discriminate between cotyledons having sinigrin or glucobrassicin since the two crucifers were fed upon equally in choice tests. Restricting the concentration of sulfur in the nutrient medium accelerated the decline of sinigrin inB. juncea cv. Cutlass but did not alter the feeding rate ofP. cruciferae compared to controls. Sulfur restriction reduced glucobrassicin inB. napus cv. Westar to undetectable levels and somewhat reduced the feeding rate of P.Cruciferae. Nevertheless,P. cruciferae still fed actively on cotyledons ofB. napus cv. Westar depleted of glucosinolates and severely damaged many of them. Since glucosinolate type and concentration had little effect on feeding response, reduction or elimination of foliar glucosinolates alone would not seem a useful strategy for protecting seedlings of these two crucifers from flea beetle damage.     

Variation in Fatty Acid Compositions, Oil Content and Oil Yield in a Germplasm Collection of Sesame (Sesamum indicum L.)

The variation in oil content, oil yield and fatty acid compositions of 103 sesame landraces was investigated. The landraces varied widely in their oil quantity and quality. The oil content varied between 41.3 and 62.7%, the average being 53.3%. The percentage content of linoleic, oleic, palmitic and stearic acids in the seed oil ranged between 40.7–49.3, 29.3–41.4, 8.0–10.3 and 2.1–4.8%, respectively. Linolenic and arachidic acids were the minor constituents of the sesame oil. Linoleic and oleic acids were the major fatty acids of sesame with average values of 45.7 and 37.2%, respectively. The total means of oleic and linoleic acids as unsaturated fatty acids of sesame were about 83% which increases the suitability of the sesame oil for human consumption. The superiority of the collection was observed in oil content. The oil content of a few accessions was above 60%, proving claims that some varieties of sesame can reach up to 63% in oil content. The accessions with the highest oil content were relatively richer in the linoleic acid content while there were some landraces in which linoleic and oleic acid contents were in a proportion of almost 1:1. The results obtained in this study provide useful background information for developing new cultivars with a high oil content and different fatty acid compositions. Several accessions could be used as parental lines in breeding programmes aiming to increase sesame oil quantity and quality.     

Within-plant variation in concentrations of amino acids,sugar, and sinigrin in phloem sap of black mustard,Brassica nigra (L.) Koch (Cruciferae)

Although within-plant variation in the nutrient and allelochemical composition of phloem sap has been invoked to explain patterns of host use by phloem-feeding insects, little is known about within-plant variation in phloem chemistry. Here I describe a new technique in which I use the green peach aphid,Myzus persicae Sulz., to investigate within-plant variation in the concentrations of chemicals in the phloem sap of black mustard,Brassica nigra (L.) Koch (Cruciferae). Relationships between the concentrations of chemicals in aphid diets and honeydew were established using honeydew from aphids fed on artificial diets with known concentrations of amino acids, sucrose, and sinigrin. These relationships were applied to honeydew from aphids fed on different aged leaves of black mustard to estimate the concentrations of the chemicals in phloem sap. Sinigrin concentration was estimated to be high (>10 mM) in phloem sap in young leaves, calling into question the prevailing opinion that phloem sap contains only low concentrations of allelochemicals. High concentrations may function as defenses against sap-feeding herbivores. Within-plant variation in phloem sap composition was high: (1) young leaves had high concentrations of nutrients (216 mM amino acids, 26% sugar) and sinigrin (>10 mM); (2) mature and presenescent leaves had lower concentrations of nutrients (77–83 mM amino acids, 19–20% sugar) and low concentrations of sinigrin (1–2 mM); and (3) senescing leaves had high concentrations of nutrients (199 mM amino acids, 25% sugar) and low concentrations of sinigrin (3 mM).     

The effect of freezing on the analysis of chlorophyll content of canola seed (Brassica napus L.)

High levels of chlorophyll in harvested canola seed result in loss of revenue to producers and problems for processors. Studies on chlorophyll degradation often require plant material to be stored for some time prior to measuring the chlorophyll content. Storage of unripe canola seed in a freezer for up to one month prior to measuring the chlorophyll content did not alter the chlorophyll level in the seed. Seeds were frozen while still in the pods as well as after removal with no change in chlorophyll content over time.     

Characterization of yam bean (Pachyrhizus spp.) Seeds as potential sources of high palmitic acid oil

Seeds from 22 accessions of the yam bean species Pachyrhizus ahipa (14 accessions), P. erosus (5), and P. tuberosus (3) were investigated for oil and protein contents, fatty acid composition of the seed oil, and the total tocopherol content and composition. Plants from the accessions were grown under greenhouse conditions during one (P. erosus and P. tuberosus) or two years (P. ahipa). The pattern of the investigated seed quality traits was very similar in the three species. Yam bean seeds were characterized by high oil (from about 20 to 28% in one environment) and protein contents (from about 23 to 34%). Seed oil contained high concentrations of palmitic (from about 25 to 30% of the total fatty acids), oleic (21 to 29%), and linoleic acids (35 to 40%). Levels of linolenic acid were very low, from about 1.0 to 2.5%. Total tocopherol content was relatively low in P. erosus (from 249 to 585 mg kg⁻¹ oil) and P. tuberosus (from 260 to 312 mg kg⁻¹ oil) compared with the levels found in P. ahipa grown under identical conditions (508 to 858 mg kg⁻¹ oil). In all the samples, γ-tocopherol was predominant, accounting for more than 90% of the total tocopherol content. The combination of high oil and protein contents, together with high palmitic acid, low linolenic acid, and high γ-tocopherol concentration, makes these crops an interesting alternative as sources of high palmitic acid oil for the food industry.