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.     

Homogeneous,heterogeneous and enzymatic catalysis for transesterification of high free fatty acid oil (waste cooking oil) to biodiesel: A review

In the last few years, biodiesel has emerged as one of the most potential renewable energy to replace current petrol-derived diesel. It is a renewable, biodegradable and non-toxic fuel which can be easily produced through transesterification reaction. However, current commercial usage of refined vegetable oils for biodiesel production is impractical and uneconomical due to high feedstock cost and priority as food resources. Low-grade oil, typically waste cooking oil can be a better alternative; however, the high free fatty acids (FFA) content in waste cooking oil has become the main drawback for this potential feedstock. Therefore, this review paper is aimed to give an overview on the current status of biodiesel production and the potential of waste cooking oil as an alternative feedstock. Advantages and limitations of using homogeneous, heterogeneous and enzymatic transesterification on oil with high FFA (mostly waste cooking oil) are discussed in detail. It was found that using heterogeneous acid catalyst and enzyme are the best option to produce biodiesel from oil with high FFA as compared to the current commercial homogeneous base-catalyzed process. However, these heterogeneous acid and enzyme catalyze system still suffers from serious mass transfer limitation problems and therefore are not favorable for industrial application. Nevertheless, towards the end of this review paper, a few latest technological developments that have the potential to overcome the mass transfer limitation problem such as oscillatory flow reactor (OFR), ultrasonication, microwave reactor and co-solvent are reviewed. With proper research focus and development, waste cooking oil can indeed become the next ideal feedstock for biodiesel.     

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.     

Synthesis of fatty acid methyl ester from used vegetable cooking oil by solid reusable Mg 1-x Zn 1+x O2 catalyst

Fatty acid methyl ester was produced from used vegetable cooking oil using Mg_1−x Zn_1+xO₂ solid catalyst and the performance monitored in terms of ester content obtained. Used vegetable cooking oil was employed to reduce operation cost of biodiesel. The significant operating parameters which affect the overall yield of the process were studied. The highest ester content, 80%, was achieved with the catalyst during 4 h 15 min reaction at 188 °C with methanol to oil ratio of 9:1 and catalyst loading of 2.55 wt% oil. Also, transesterification of virgin oil gave higher yield with the heterogeneous catalyst and showed high selectivity towards ester production. The used vegetable cooking oil did not require any rigorous pretreatment. Catalyst stability was examined and there was no leaching of the active components, and its performance was as good at the fourth as at the first cycle.     

Assessment of four biodiesel production processes using HYSYS.Plant

Four continuous biodiesel processes were designed and simulated in HYSYS. The first two employed traditional homogeneous alkali and acid catalysts. The third and fourth processes used a heterogeneous acid catalyst and a supercritical method to convert a waste vegetable oil feedstock into biodiesel. While all four processes were capable of producing biodiesel at high purity, the heterogeneous and supercritical processes were the least complex and had the smallest number of unit operations. Material and energy flows, as well as sized unit operation blocks, were used to conduct an economic assessment of each process. Total capital investment, total manufacturing cost and after tax rate-of-return were calculated for each process. The heterogeneous acid catalyst process had the lowest total capital investment and manufacturing costs, and had the only positive after tax rate-of-return.     

The potential of restaurant waste lipids as biodiesel feedstocks

Biodiesel is usually produced from food-grade vegetable oils that are more expensive than diesel fuel. Therefore, biodiesel produced from food-grade vegetable oil is currently not economically feasible. Waste cooking oils, restaurant grease and animal fats are potential feedstocks for biodiesel. These inexpensive feedstocks represent one-third of the US total fats and oil production, but are currently devoted mostly to industrial uses and animal feed. The characteristics of feedstock are very important during the initial research and production stage. Free fatty acids and moisture reduce the efficiency of transesterification in converting these feedstocks into biodiesel. Hence, this study was conducted to determine the level of these contaminants in feedstock samples from a rendering plant. Levels of free fatty acids varied from 0.7% to 41.8%, and moisture from 0.01% to 55.38%. These wide ranges indicate that an efficient process for converting waste grease and animal fats must tolerate a wide range of feedstock properties.     

Process design and evaluation of value-added chemicals production from biomass

Three different biodiesel production processes were simulated using the SuperPro Designer program. The process for producing biodiesel from soybean oil and methanol was designed using commercial chemical catalysts. This chemical process was compared with the biological process catalyzed by immobilized enzymes. In addition, a hybrid process consisting of catalytic biodiesel production and enzymatic glycerol carbonate production was designed and simulated for the conversion of waste glycerol to value-added chemical. Finally, the economics and productivity of these processes were evaluated to determine economic feasibility.     

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.     

Upstream and downstream strategies to economize biodiesel production

In recent years biodiesel has drawn considerable amount of attention as a clean and renewable fuel. Biodiesel is produced from renewable sources such as vegetable oils and animal fat mainly through catalytic or non-catalytic transesterification method as well as supercritical method. However, as a consequence of disadvantages of these methods, the production cost increases dramatically. This article summarizes different biodiesel production methods with a focus on their advantages and disadvantages. The downstream and upstream strategies such as using waste cooking oils, application of non-edible plant oils, plant genetic engineering, using membrane separation technology for biodiesel production, separation and purification, application of crude glycerin as an energy supplement for ruminants, glycerin ultra-purification and their consequent roles in economizing the production process are fully discussed in this article.     

Biodiesel production—current state of the art and challenges

Biodiesel is a clean-burning fuel produced from grease, vegetable oils, or animal fats. Biodiesel is produced by transesterification of oils with short-chain alcohols or by the esterification of fatty acids. The transesterification reaction consists of transforming triglycerides into fatty acid alkyl esters, in the presence of an alcohol, such as methanol or ethanol, and a catalyst, such as an alkali or acid, with glycerol as a byproduct. Because of diminishing petroleum reserves and the deleterious environmental consequences of exhaust gases from petroleum diesel, biodiesel has attracted attention during the past few years as a renewable and environmentally friendly fuel. Since biodiesel is made entirely from vegetable oil or animal fats, it is renewable and biodegradable. The majority of biodiesel today is produced by alkali-catalyzed transesterification with methanol, which results in a relatively short reaction time. However, the vegetable oil and alcohol must be substantially anhydrous and have a low free fatty acid content, because the presence of water or free fatty acid or both promotes soap formation. In this article, we examine different biodiesel sources (edible and nonedible), virgin oil versus waste oil, algae-based biodiesel that is gaining increasing importance, role of different catalysts including enzyme catalysts, and the current state-of-the-art in biodiesel production. JIMB 2008: BioEnergy—special issue.     

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.     

Economic assessment of batch biodiesel production processes using homogeneous and heterogeneous alkali catalysts

An economic feasibility study on four batch processes for the production of biodiesel ranging from 1452 tonnes/year (5000 l/day) to 14,520 tonnes/year (50,000 l/day) is conducted. The four processes assessed are the (1) KOH-W process, characterized by a homogeneous KOH catalyst and hot water purification process; (2) KOH-D process, characterized by a homogeneous KOH catalyst and vacuum FAME distillation process; (3) CaO-W process, characterized by a heterogeneous CaO catalyst and hot water purification process; and (4) CaO-D process, characterized by a heterogeneous CaO catalyst and vacuum FAME distillation process. The costs of the waste cooking oil, fixed costs, and manufacturing costs for producing 7260 tonnes/year (25,000 l/day) of biodiesel by means of the four processes are estimated to be $248–256, $194–232, and $584–641 per tonne of biodiesel, respectively. Among the four processes, the manufacturing costs involved in the CaO-W process are the lowest, in the range from 1452 tonnes/year to 14,520 tonnes/year.     

An overview on the recent advances in the transesterification of vegetable oils for biodiesel production using chemical and biocatalysts

Biodiesel, chemically defined as monoalkyl esters of long chain fatty acids, are derived from renewable feed stocks like vegetable oils and animal fats. It is produced by both batch and continuous transesterification processes in which, oil or fat is reacted with a monohydric alcohol in the presence of a catalyst. The conventional method of producing biodiesel involves acid and base catalysts to form fatty acid alkyl esters. Downstream processing costs and environmental problems associated with biodiesel production and byproducts recovery have led to the search for alternative production methods and alternative substrates. Enzymatic reactions involving lipases can be an excellent alternative to produce biodiesel through a process commonly referred to as alcoholysis, a form of transesterification reaction or through an interesterification reaction. In order to increase the cost effectiveness of the process, the enzymes are immobilized using a suitable matrix. The use of immobilized lipases and whole cells may lower the overall cost, while presenting less downstream processing problems. Main focus of this paper is to discuss the important parameters that affect the biodiesel yield, various immobilization techniques employed, mechanisms and kinetics of transesterification reaction and the recent advances in continuous transesterification processes.     

Biodiesel from microalgae

Continued use of petroleum sourced fuels is now widely recognized as unsustainable because of depleting supplies and the contribution of these fuels to the accumulation of carbon dioxide in the environment. Renewable, carbon neutral, transport fuels are necessary for environmental and economic sustainability. Biodiesel derived from oil crops is a potential renewable and carbon neutral alternative to petroleum fuels. Unfortunately, biodiesel from oil crops, waste cooking oil and animal fat cannot realistically satisfy even a small fraction of the existing demand for transport fuels. As demonstrated here, microalgae appear to be the only source of renewable biodiesel that is capable of meeting the global demand for transport fuels. Like plants, microalgae use sunlight to produce oils but they do so more efficiently than crop plants. Oil productivity of many microalgae greatly exceeds the oil productivity of the best producing oil crops. Approaches for making microalgal biodiesel economically competitive with petrodiesel are discussed.     

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.     

Life cycle emissions and energy study of biodiesel derived from waste cooking oil and diesel in Singapore

Background, aim and scope  

Biodiesel derived from Waste Cooking Oil (WCO) is considered highly environmentally sustainable since WCO is a waste product from domestic and commercial cooking processes and then recycled to a transportation fuel in Singapore. In addition, it avoids the conversion of land use for crop production. This is a strong advantage for Singapore which has relatively smaller land space than other countries. The import of virgin oil as feedstock into Singapore is also avoided. Therefore, the more appropriate feedstock to produce biodiesel in Singapore context is WCO. According to the National Environment Agency, diesel vehicles in Singapore contribute 50% of the total particulate matter smaller than 2.5 μm (PM_0.25) emissions to air ambient. Hence, the aim of this life cycle assessment study was to compare the environmental performances of biodiesel derived from WCO and low sulphur diesel in terms of global warming potential, life cycle energy efficiency (LCEE) and fossil energy ratio (FER) using the life cycle inventory. The results of this study would serve as a reference for energy policy makers and environmental agencies.     

Effect of water on lipase NS81006-catalyzed alcoholysis for biodiesel production

Biodiesel production catalyzed by free lipase has been drawing attention for its lower cost and faster reaction rate compared to immobilized lipase. It has been found that free lipase NS81006 could efficiently catalyze alkyl esters production and a certain amount of water is demonstrated to be necessary for the catalytic process. The effect of water content on liquid lipase NS81006-mediated methanolysis and ethanolysis for biodiesel production was first explored respectively in this paper. It was found that with water content ranging from 3% to 10% (based on oil weight), there was no significant difference in the final alkyl ester yield either in NS81006-mediated methanolysis or ethanolysis process, while the quality of biodiesel varied obviously. The acid value as well as the contents of monoglyceride and diglyceride were much lower in the lower water-containing system. With the water content decreasing from 10% to 3%, the acid value reduced from 8.24 to 4.89 mg KOH/g oil, and the content of MAG and DAG dropped to 0.31 and 0.22, from 0.62 and 0.74, respectively. Lipase could maintain rather good stability with proper alcohol adding strategy and the gradual reduction in biodiesel yield in the repeated uses resulted from the accumulation of by-product glycerol. The continuous running of lipase-mediated methanolysis of waste cooking oil was successfully realized at 30L reactor and a final methyl ester yield of over 90% could be obtained.     

Biodiesel production by transesterification using immobilized lipase

Biodiesel can be produced by transesterification of vegetable or waste oil catalysed by lipases. Biodiesel is an alternative energy source to conventional fuel. It combines environmental friendliness with biodegradability, low toxicity and renewability. Biodiesel transesterification reactions can be broadly classified into two categories: chemical and enzymatic. The production of biodiesel using the enzymatic route eliminates the reactions catalysed under acid or alkali conditions by yielding product of very high purity. The modification of lipases can improve their stability, activity and tolerance to alcohol. The cost of lipases and the relatively slower reaction rate remain the major obstacles for enzymatic production of biodiesel. However, this problem can be solved by immobilizing the enzyme on a suitable matrix or support, which increases the chances of re-usability. The main factors affecting biodiesel production are composition of fatty acids, catalyst, solvents, molar ratio of alcohol and oil, temperature, water content, type of alcohol and reactor configuration. Optimization of these parameters is necessary to reduce the cost of biodiesel production.     

Integrated reactive absorption process for synthesis of fatty esters

Reactive separations using green catalysts offer great opportunities for manufacturing fatty esters, involved in specialty chemicals and biodiesel production. Integrating reaction and separation into one unit provides key benefits such as: simplified operation, no waste, reduced capital investment and low operating costs.This work presents a novel heat-integrated reactive absorption process that eliminates all conventional catalyst related operations, efficiently uses the raw materials and equipment, and considerably reduces the energy requirements for biodiesel production - 85% lower as compared to the base case. Rigorous simulations based on experimental results were carried out using Aspen Plus and Dynamics. Despite the high degree of integration, the process is well controllable using an efficient control structure proposed in this work. The main results are provided for a plant producing 10 ktpy fatty acid methyl esters from methanol and waste vegetable oil with high free fatty acids content, using sulfated zirconia as solid acid catalyst.     

Alternative Oils Tested as Feedstocks for Enzymatic FAMEs Synthesis: Toward a More Sustainable Process

Previously isolated and characterized Pseudomonas lipases were immobilized in a low‐cost MP‐1000 support by a re‐loading procedure that allowed a high activity per weight of support. Immobilized LipA, LipC, and LipCmut lipases, and commercial Novozym® 435 were tested for fatty acid methyl ester (FAMEs) synthesis using conventional and alternative feedstocks. Triolein and degummed soybean oils were used as model substrates, whereas waste cooking oil and M. circinelloides oil were assayed as alternative, low cost feedstocks, whose free fatty acid (FFA), and acylglyceride profile was characterized. The reaction conditions for FAMEs synthesis were initially established using degummed soybean oil, setting up the best water and methanol concentrations for optimum conversion. These conditions were further applied to the alternative feedstocks and the four lipases. The results revealed that Pseudomonas lipases were unable to use the FFAs, displaying a moderate FAMEs synthesis, whereas a 44% FAMEs production was obtained when M. circinelloides oil was used as a substrate in the reaction catalysed by Novozym® 435, used under the conditions established for degummed soybean oil. However, when Novozym® 435 was tested under previously described optimal conditions for this lipase, promising values of 85 and 76% FAMEs synthesis were obtained for waste cooking oil and M. circinelloides oil, respectively, which might result in promising, nonfood, alternative feedstocks for enzymatic biodiesel production. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1209–1217, 2017