Biodiesel production from Jatropha oil by catalytic and non-catalytic approaches: an overview

Biodiesel (fatty acids alkyl esters) is a promising alternative fuel to replace petroleum-based diesel that is obtained from renewable sources such as vegetable oil, animal fat and waste cooking oil. Vegetable oils are more suitable source for biodiesel production compared to animal fats and waste cooking since they are renewable in nature. However, there is a concern that biodiesel production from vegetable oil would disturb the food market. Oil from Jatropha curcas is an acceptable choice for biodiesel production because it is non-edible and can be easily grown in a harsh environment. Moreover, alkyl esters of jatropha oil meet the standard of biodiesel in many countries. Thus, the present paper provides a review on the transesterification methods for biodiesel production using jatropha oil as feedstock.     

Biodiesel production from high acid value waste frying oil catalyzed by superacid heteropolyacid

Transesterification of waste cooking oil with high acid value and high water contents using heteropolyacid H3PW12O40 x 6H2O (PW12) as catalyst was investigated. The hexahydrate form of PW(12) was found to be the most promising catalyst which exhibited highest ester yield 87% for transesterification of waste cooking oil and ester yield 97% for esterification of long-chain palmitic acid, respectively. The PW12 acid catalyst shows higher activity under the optimized reaction conditions compared with conventional homogeneous catalyst sulfuric acid, and can easily be separated from the products by distillation of the excess methanol and can be reused more times. The most important feature of this catalyst is that the catalytic activity is not affected by the content of free fatty acids (FFAs) and the content of water in the waste cooking oil and the transesterification can occur at a lower temperature (65 degrees C), a lower methanol oil ratio (70:1) and be finished within a shorter time. The results illustrate that PW12 acid is an excellent water-tolerant and environmentally benign acid catalyst for production of biodiesel from waste cooking oil.     

Silica-bonded N-propyl sulfamic acid used as a heterogeneous catalyst for transesterification of soybean oil with methanol

The transesterification of soybean oil with methanol was carried out, to produce biodiesel, over silica-bonded N-propyl sulfamic acid in a heterogeneous manner. Results showed that a maximum conversion of 90.5% was achieved using a 1:20 M ratio of soybean oil to methanol and a catalyst amount of 7.5 wt.% at 423 K for 60 h. It was found that the free fatty acid (FFA) and water present in the feedstock had no significant influence on the catalytic activity to the transesterification reaction. Besides, the catalyst also showed activities towards the esterification reaction of FFAs, in terms of the FFA conversion of 95.6% at 423 K for 30 h. Furthermore, the catalyst could be recovered with a better reusability.     

Technical difficulties and solutions of direct transesterification process of microbial oil for biodiesel synthesis

Microbial oils are considered as alternative to vegetable oils or animal fats as biodiesel feedstock. Microalgae and oleaginous yeast are the main candidates of microbial oil producers’ community. However, biodiesel synthesis from these sources is associated with high cost and process complexity. The traditional transesterification method includes several steps such as biomass drying, cell disruption, oil extraction and solvent recovery. Therefore, direct transesterification or in situ transesterification, which combines all the steps in a single reactor, has been suggested to make the process cost effective. Nevertheless, the process is not applicable for large-scale biodiesel production having some difficulties such as high water content of biomass that makes the reaction rate slower and hurdles of cell disruption makes the efficiency of oil extraction lower. Additionally, it requires high heating energy in the solvent extraction and recovery stage. To resolve these difficulties, this review suggests the application of antimicrobial peptides and high electric fields to foster the microbial cell wall disruption.     

Biodiesel production from waste cooking oil: 1. Process design and technological assessment

Four different continuous process flowsheets for biodiesel production from virgin vegetable oil or waste cooking oil under alkaline or acidic conditions on a commercial scale were developed. Detailed operating conditions and equipment designs for each process were obtained. A technological assessment of these four processes was carried out to evaluate their technical benefits and limitations. Analysis showed that the alkali-catalyzed process using virgin vegetable oil as the raw material required the fewest and smallest process equipment units but at a higher raw material cost than the other processes. The use of waste cooking oil to produce biodiesel reduced the raw material cost. The acid-catalyzed process using waste cooking oil proved to be technically feasible with less complexity than the alkali-catalyzed process using waste cooking oil, thereby making it a competitive alternative to commercial biodiesel production by the alkali-catalyzed process.     

Enzyme catalyzed transesterification of waste cooking oil with dimethyl carbonate

The detrimental effects of waste cooking oil on sewer system attracted attention toward its proper management and reusing this waste oil for making biodiesel provides commercial and environmental advantage. In the present study, biodiesel has been successfully produced from waste cooking oil and dimethyl carbonate by transesterification, instead of the conventional alcohol. In this optimization study, the effect of various reaction conditions such as solvent, time and temperature, molar ratio of DMC to oil, enzyme loading and reusability, on the yield of fatty acid methyl ester (FAME) has been studied. The Maximum conversion of FAMEs achieved was 77.87% under optimum conditions (solvent free system, reaction time of 24 h, 60 °C, molar ratio of DMC to oil 6:1, catalyst amount 10% Novozym 435 (based on the oil weight)). Moreover, there was no obvious loss in the conversion after lipases were reused for 6 batches under optimized conditions.     

Optimization of a Novel Two-step Process Comprising Re-esterification and Transesterification in a Single Reactor for Biodiesel Production Using Waste Cooking Oil

Waste cooking oil (WCO) has attracted attention as a non-edible feedstock for biodiesel. Although an alkali catalyst has several advantages over an acid catalyst in biodiesel production, biodiesel conversion from WCO is only 5.2% when using an alkali catalyst (NaOH), owing to its high free fatty acid (FFA) content of 4.2%. In this study, a novel two-step process in a single reactor, comprised of re-esterification of the FFAs with crude glycerol, using a Tin (II) chloride (SnCl₂) catalyst, and subsequent transesterification with methanol, using an alkali catalyst, was adopted, and each step was optimized. This study revealed that the FFA content after re-esterification should be approximately 1.5%, not only to save glycerol and the catalyst involved in the re-esterification, but also to achieve high biodiesel conversion during the transesterification. An alkaline catalyst was successfully used to produce biodiesel in the second step, and a 92.8% conversion to biodiesel was achieved under the optimized conditions (0.6% catalyst relative to WCO, 0.2mL-methanol/WCO, 70ºC, 3 h). Overall, this novel two-step process achieved highly enhanced biodiesel conversion (4.0% to 92.8%) with significantly reduced reaction time (12 h to 4 h) and methanol requirements (15 mL/g-WCO to 0.2 mL/g-WCO).     

Membrane technology as a promising alternative in biodiesel production: A review

In recent years, environmental problems caused by the use of fossil fuels and the depletion of petroleum reserves have driven the world to adopt biodiesel as an alternative energy source to replace conventional petroleum-derived fuels because of biodiesel's clean and renewable nature. Biodiesel is conventionally produced in homogeneous, heterogeneous, and enzymatic catalysed processes, as well as by supercritical technology. All of these processes have their own limitations, such as wastewater generation and high energy consumption. In this context, the membrane reactor appears to be the perfect candidate to produce biodiesel because of its ability to overcome the limitations encountered by conventional production methods. Thus, the aim of this paper is to review the production of biodiesel with a membrane reactor by examining the fundamental concepts of the membrane reactor, its operating principles and the combination of membrane and catalyst in the catalytic membrane. In addition, the potential of functionalised carbon nanotubes to serve as catalysts while being incorporated into the membrane for transesterification is discussed. Furthermore, this paper will also discuss the effects of process parameters for transesterification in a membrane reactor and the advantages offered by membrane reactors for biodiesel production. This discussion is followed by some limitations faced in membrane technology. Nevertheless, based on the findings presented in this review, it is clear that the membrane reactor has the potential to be a breakthrough technology for the biodiesel industry.     

Biodiesel production from various feedstocks and their effects on the fuel properties

Biodiesel, which is a new, renewable and biological origin alternative diesel fuel, has been receiving more attention all over the world due to the energy needs and environmental consciousness. Biodiesel is usually produced from food-grade vegetable oils using transesterification process. Using food-grade vegetable oils is not economically feasible since they are more expensive than diesel fuel. Therefore, it is said that the main obstacle for commercialization of biodiesel is its high cost. Waste cooking oils, restaurant greases, soapstocks and animal fats are potential feedstocks for biodiesel production to lower the cost of biodiesel. However, to produce fuel-grade biodiesel, the characteristics of feedstock are very important during the initial research and production stage since the fuel properties mainly depend on the feedstock properties. This review paper presents both biodiesel productions from various feedstocks and their effects on the fuel properties. JIMB 2008: BioEnergy - Special issue.     

Lipase-catalyzed biodiesel production with methyl acetate as acyl acceptor

Biodiesel is an alternative diesel fuel made from renewable biological resources. During the process of biodiesel production, lipase-catalyzed transesterification is a crucial step. However, current techniques using methanol as acyl acceptor have lower enzymatic activity; this limits the application of such techniques in large-scale biodiesel production. Furthermore, the lipid feedstock of currently available techniques is limited. In this paper, the technique of lipase-catalyzed transesterification of five different oils for biodiesel production with methyl acetate as acyl acceptor was investigated, and the transesterification reaction conditions were optimized. The operation stability of lipase under the obtained optimal conditions was further examined. The results showed that under optimal transesterification conditions, both plant oils and animal fats led to high yields of methyl ester: cotton-seed oil, 98%; rapeseed oil, 95%; soybean oil, 91%; tea-seed oil, 92%; and lard, 95%. Crude and refined cottonseed oil or lard made no significant difference in yields of methyl ester. No loss of enzymatic activity was detected for lipase after being repeatedly used for 40 cycles (ca. 800 h), which indicates that the operational stability of lipase was fairly good under these conditions. Our results suggest that cotton-seed oil, rape-seed oil and lard might substitute soybean oil as suitable lipid feedstock for biodiesel production. Our results also show that our technique is fit for various lipid feedstocks both from plants and animals, and presents a very promising way for the large-scale biodiesel production.     

Catalytic Packed-Bed Reactor Configuration for Biodiesel Production Using Waste Oil as Feedstock

Pumice, a natural porous silica material, exchanged with potassium is an efficient heterogeneous particulate catalytic material for triglycerides and free fatty acids transesterification reaction from sunflower oil and waste frying oil at low temperature. In this work, a packed-bed catalytic configuration reactor using this catalytic material was developed for biodiesel fuel production from sunflower oil and frying oil feedstock. Reactor operation variables as methanol/oil molar ratio, catalyst amount, reaction time, and reaction temperature were studied. Results were compared with those obtained from the same transesterification reaction proceeding in a slurry batch reactor. The packed-bed catalytic reactor configuration can be useful in order to minimize catalyst mechanical damage occurring in the slurry reactor due to continuous stirring. The possibility of using a packed-bed reactor shows some advantages because the catalyst stays confined in the reactor bed and the reaction products can be easily separated, besides the mechanical stability of the catalyst particles is achieved.     

Microbial lipids from cellulolytic oleaginous fungus Penicillium citrinum PKB20 as a potential feedstock for biodiesel production

Microbial lipids derived from oleaginous fungi are considered as an alternative feedstock for biodiesel production. We attempt to isolate a cellulolytic oleaginous fungi as a potential feedstock for biodiesel production. The fungus was identified by 5.8 S-ITS rRNA gene sequencing. The extracellular enzyme activities were recorded after every 24 h for 7 days. Nile red staining and fluorescence microscopy was used to visualise the lipid bodies within the fungal hyphae. A renewable heterogeneous base catalyst derived from Musa balbisiana cola peels was used for the transesterification of Penicillium citrinum PKB20 derived oil into biodiesel. GC-MS analysis was used to analyse the fatty acid methyl esters (FAME) profile of the transesterified lipids. Penicillium citrinum PKB20 was isolated from detritus rich soil of Assam, India. The endoglucanase, xylanase and β-glucosidase enzyme activities were found to be 292.83 ± 0.29, 111.72 ± 0.45 and 6.54 ± 0.13 U/mg respectively. The specific enzyme activity for extracellular lipase was found to be 3.12 ± 0.16 U/mg. It could accumulate up to 60.61% of lipids in nitrogen-limited medium (7.34 ± 0.45 g/L biomass production). The extracted lipids were converted to biodiesel with 89.3% conversion efficiency. The predominant fatty acids were oleic acid (30.09%), palmitic acid (20.25%) and linoleic acid (33.14%) suggesting a balance between oxidative stability and cold flow properties for suitable biodiesel quality. Penicillium citrinum PKB20 was found to be a potential feedstock for biodiesel production with desirable fuel properties. The cellulolytic nature could be utilised for simultaneous lipid production directly on cellulosic substrates.     

Synthesis of fatty acid methyl ester from crude jatropha (Jatropha curcas Linnaeus) oil using aluminium oxide modified Mg-Zn heterogeneous catalyst

The synthesis of fatty acid methyl esters (FAME) as a substitute to petroleum diesel was investigated in this study from crude jatropha oil (CJO), a non-edible, low-cost alternative feedstock, using aluminium modified heterogeneous basic oxide (Mg-Zn) catalyst. The transesterification reaction with methanol to methyl esters yielded 94% in 6 h with methanol-oil ratio of 11:1, catalyst loading of 8.68 wt.% at 182 °C and the properties of CJO fuel produced were determine and found to be comparable to the standards according to ASTM. In the range of experimental parameters investigated, it showed that the catalyst is selective to production of methyl esters from oil with high free fatty acid (FFA) and water content of 7.23% and 3.28%, respectively in a single stage process. Thus, jatropha oil is a promising feedstock for methyl ester production and large scale cultivation will help to reduce the product cost.     

Biodiesel production from waste cooking oil: 2. Economic assessment and sensitivity analysis

The economic feasibilities of four continuous processes to produce biodiesel, including both alkali- and acid-catalyzed processes, using waste cooking oil and the ‘standard’ process using virgin vegetable oil as the raw material, were assessed. Although the alkali-catalyzed process using virgin vegetable oil had the lowest fixed capital cost, the acid-catalyzed process using waste cooking oil was more economically feasible overall, providing a lower total manufacturing cost, a more attractive after-tax rate of return and a lower biodiesel break-even price. On the basis of these economic calculations, sensitivity analyses for these processes were carried out. Plant capacity and prices of feedstock oils and biodiesel were found to be the most significant factors affecting the economic viability of biodiesel manufacture.     

Biodiesel production using heterogeneous catalysts

The production and use of biodiesel has seen a quantum jump in the recent past due to benefits associated with its ability to mitigate greenhouse gas (GHG). There are large number of commercial plants producing biodiesel by transesterification of vegetable oils and fats based on base catalyzed (caustic) homogeneous transesterification of oils. However, homogeneous process needs steps of glycerol separation, washings, very stringent and extremely low limits of Na, K, glycerides and moisture limits in biodiesel. Heterogeneous catalyzed production of biodiesel has emerged as a preferred route as it is environmentally benign needs no water washing and product separation is much easier. The present report is review of the progress made in development of heterogeneous catalysts suitable for biodiesel production. This review shall help in selection of suitable catalysts and the optimum conditions for biodiesel production.     

Continuous biosynthesis of biodiesel from waste cooking palm oil in a packed bed reactor: optimization using response surface methodology (RSM) and mass transfer studies

This study aimed to develop an optimal continuous procedure of lipase-catalyzes transesterification of waste cooking palm oil in a packed bed reactor to investigate the possibility of large scale production further. Response surface methodology (RSM) based on central composite rotatable design (CCRD) was used to optimize the two important reaction variables packed bed height (cm) and substrate flow rate(ml/min) for the transesterification of waste cooking palm oil in a continuous packed bed reactor. The optimum condition for the transesterification of waste cooking palm oil was as follows: 10.53 cm packed bed height and 0.57 ml/min substrate flow rate. The optimum predicted fatty acid methyl ester (FAME) yield was 80.3% and the actual value was 79%. The above results shows that the RSM study based on CCRD is adaptable for FAME yield studied for the current transesterification system. The effect of mass transfer in the packed bed reactor has also been studied. Models for FAME yield have been developed for cases of reaction control and mass transfer control. The results showed very good agreement compatibility between mass transfer model and the experimental results obtained from immobilized lipase packed bed reactor operation, showing that in this case the FAME yield was mass transfer controlled.     

Moringa oleifera oil: a possible source of biodiesel

Biodiesel is an alternative to petroleum-based conventional diesel fuel and is defined as the mono-alkyl esters of vegetable oils and animal fats. Biodiesel has been prepared from numerous vegetable oils, such as canola (rapeseed), cottonseed, palm, peanut, soybean and sunflower oils as well as a variety of less common oils. In this work, Moringa oleifera oil is evaluated for the first time as potential feedstock for biodiesel. After acid pre-treatment to reduce the acid value of the M. oleifera oil, biodiesel was obtained by a standard transesterification procedure with methanol and an alkali catalyst at 60 degrees C and alcohol/oil ratio of 6:1. M. oleifera oil has a high content of oleic acid (>70%) with saturated fatty acids comprising most of the remaining fatty acid profile. As a result, the methyl esters (biodiesel) obtained from this oil exhibit a high cetane number of approximately 67, one of the highest found for a biodiesel fuel. Other fuel properties of biodiesel derived from M. oleifera such as cloud point, kinematic viscosity and oxidative stability were also determined and are discussed in light of biodiesel standards such as ASTM D6751 and EN 14214. The (1)H NMR spectrum of M. oleifera methyl esters is reported. Overall, M. oleifera oil appears to be an acceptable feedstock for biodiesel.     

Acid-catalyzed esterification of Zanthoxylum bungeanum seed oil with high free fatty acids for biodiesel production

A technique to produce biodiesel from crude Zanthoxylum bungeanum seed oil (ZSO) with high free fatty acids (FFA) was developed. The acid value of ZSO was reduced to 1.16mg KOH/g from 45.51mg KOH/g by only one-step acid-catalyzed esterification with methanol-to-oil molar ratio 24:1, H(2)SO(4) 2%, temperature 60 degrees C and reaction time 80min, which was selected as optimum for the acid-catalyzed esterification. During the acid-catalyzed esterification, FFA was converted into fatty acid methyl esters, which was confirmed by (1)H NMR spectrum. Compared with the other two-step pretreatment procedure, this one-step pretreatment can reduce the production cost of ZSO biodiesel. Alkaline-catalyzed transesterification converted the pretreated ZSO into ZSO biodiesel. The yield of ZSO biodiesel was above 98% determined by (1)H NMR spectrum. This study supports the use of crude ZSO as a viable and valuable raw feedstock for biodiesel production.     

Biodiesel Production from Waste Cooking Oil Using Anion-Exchange Resin as Both Catalyst and Adsorbent

A novel production process of biodiesel fuel was developed using an expanded-bed reactor packed with an anion-exchange resin having catalytic and adsorption abilities. Waste cooking oil was used as a cheaper feedstock, and methanol was added at the stoichiometric molar ratio of 3:1. The main constituent of the feedstock, triglyceride was completely converted to the biodiesel by the resin??s catalytic ability. The impurities of the feedstock, free fatty acid, water, and dark brown pigment were removed from the product by the adsorption on the resin. In addition, the by-product glycerin was also removed from the product by the adsorption on the resin. The product eluted from the reactor was directly used for the standard tests of the biodiesel properties. The eluted product almost met the biodiesel quality standards (EN14214 in Europe and ASTM D6751 in North America). Thus, the proposed system permitted the simple production of biodiesel from the waste cooking oil without the upstream processing to remove the impurities (free fatty acid and water) and the downstream processing to remove the catalyst and by-products (glycerin and soap).     

Synthesis of fatty acid methyl ester from palm oil (Elaeis guineensis) with Ky(MgCa)2xO3 as heterogeneous catalyst

Fatty acid methyl esters (FAME) were produced from palm oil using eggshell modified with magnesium and potassium nitrates to form a composite, low-cost heterogeneous catalyst for transesterification. The catalyst, prepared by the combination of impregnation/co-precipitation was calcined at 830 °C for 4 h. Transesterification was conducted at a constant temperature of 65 °C in a batch reactor. Design of experiment (DOE) was used to optimize the reaction parameters, and the conditions that gave highest yield of FAME (85.8%) was 5.35 wt.% catalyst loading at 4.5 h with 16:1 methanol/oil molar ratio. The results revealed that eggshell, a solid waste, can be utilized as low-cost catalyst after modification with magnesium and potassium nitrates for biodiesel production.