Production Waste Cooking Oil As Feedstock And Essay Example
Production Waste Cooking Oil As Feedstock And Essay Example

Production Waste Cooking Oil As Feedstock And Essay Example

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  • Pages: 10 (2684 words)
  • Published: August 26, 2018
  • Type: Essay
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According to C. C. Lai et al. (2005), the high cost of feedstock oil is a significant barrier for the commercialization of bio-diesel. However, research conducted by Sulaiman Al-Zuhair (2008) has demonstrated that waste-cooking oil (WCO) could be a viable alternative raw material for biodiesel production.

One way to reduce the cost of bio-diesel production is by using waste cooking oil (WCO). However, several factors must be considered for the transesterification process to be economically viable. These factors include choosing the right lipase, modifying enzymes, selecting feedstock and alcohol, using common solvents, pretreating the lipase, determining the molar ratio of alcohol to oil, considering water activity/content, and controlling reaction temperature. Optimizing these parameters is crucial in minimizing expenses associated with biodiesel production.

The utilization of low-cost or free waste materials such as WCO has environmental advantages


as it reduces pollution potential and produces an eco-friendly fuel. Additionally, converting WCO into bio-diesel significantly contributes to waste reduction and recycling efforts.

It should be noted that fresh vegetable oil and its waste differ significantly in water and free fatty acids (FFAs) content. Specifically, there is a difference of approximately 2000 ppm for water content and 10-15% for FFAs (C).

According to research conducted by C. Lai et al. in 2005 and Y. Zhang et al. in 2003, the traditional alkaline-catalyzed biodiesel production is considered unsuitable (Zhang et al., 2003; C. Lai et al., 2005).

Extensive research has been conducted on the use of lipase as a biocatalyst in the transesterification reaction for biodiesel production (2003). Lipase exists in all living organisms and can be utilized intracellularly or extracellularly. The comprehension of factors influencing this process and the significance of enzyme-catalyzed biodiesel productio

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is crucial for establishing an economically and environmentally sustainable method for producing biodiesel. The general equation for transesterification, representing R as a fatty acid group, R' as the acyl acceptor's length, and R'' as the remaining portion of the triglyceride molecule, is provided below:

Methanol is frequently employed in transesterification due to its cost-effectiveness compared to other alcohols.

Methanolysis is the use of methanol in a process. Biocatalysts from microorganisms, such as bacteria and fungi, are commonly employed in biotechnology and organic chemistry. Fungal lipases have been found to yield superior outcomes compared to those obtained from animals and plants. Microbial lipases are extensively commercialized and utilized in enzymatic biodiesel production because they can be mass-produced more easily than animal and plant lipases (Hasan et al., 2006; Akoh et al., 2007; Antczak et al., 2009).

One of the most common fungal lipases used for biodiesel production is Candida Antarctica lipase B (Novozyme CABL L) (Vasudevan and Briggs, 2008). Lipases, such as this one, can convert triglycerides from feed stocks into their respective fatty acids methyl esters (FAMEs). These enzymes specifically target the ester bonds of carboxylic acids and carry out their primary function of hydrolyzing fats (Joseph et al., 2008).

Enzyme immobilization is a crucial method that can enhance operation stability, activity, and selectivity. This approach enables the study of enzymes under harsh environmental conditions and allows for their separation from the reaction mixture without filtration in packed bed reactors (Fernandez-Lafuente et al., 1998; Bhushan et al., 2009; Gao et al., 2006). Ultimately, this process can result in more favorable economic benefits. Notably, the cost of lipase constitutes 90% of the total cost of enzymatic biodiesel production.

The high cost

of enzymatic biodiesel production is mainly due to the use of costly carrier or support materials (Dizge et al., 2009a). To lower expenses, scientists have been actively searching for cheaper support materials (Robles et al., 2009).

It is crucial to immobilize lipase so that it can be recovered and reused multiple times (D. S. Clark,1994;D. Cowan, 1996). Lipase immobilization involves either attaching the enzyme to a solid support or confining it in a specific area of space (Jegannathan et al.).

According to (Peilow and Misbah, 2001), when the lipase immobilization technology is implemented correctly, it can offer several significant advantages. These include the ability to reuse the enzyme, ease of separating the product from the enzyme, and the potential for continuous processes using packed-bed reactors. Various methods exist for immobilizing enzymes, including chemical and physical approaches. The most commonly used physical method is entrapment, in which the enzymes are trapped within a sol-gel matrix formed through the hydrolysis and polycondensation of precursors (Ko Woon Lee et al., 2008).

The enzyme CALB is often immobilized using the precursor TMOS in sol-gel processes. However, CALB is not stable and does not work well in reaction media with high methanol concentrations. Additionally, the enzyme is hindered by the by-product of glycerol. To solve these issues, a matrix with both hydrophilic and hydrophobic properties is created to immobilize the lipase (Ko Woon Lee, et al. 2010).

The utilization of solvents in the transesterification procedure is also taken into consideration. Solvents are employed to shield the enzyme from denaturation caused by alcohol by augmenting alcohol solubility (Kumari et al., 2009). Additionally, the solvent can boost the solubility of glycerol, which is advantageous as the

byproduct can coat the enzyme and impede its functionality (Royon et al., 2007). Implementing a shared solvent for both the reactants and products not only lessens enzyme inhibition but also ensures a homogeneous reaction mixture, diminishes the viscosity of the reaction mixture, and stabilizes the immobilized enzyme (Ranganathan et al., year).

, 2008; Fjerbaek et al., 2009). This has advantages such as reducing problems related to having multiple phases in the reaction mixture and improving mass transfer around the enzyme due to a lower viscosity (Fjerbaek et al., 2009).

According to Vasudevan and Briggs (2008), the use of solvents increases the reaction rate compared to systems without solvents. Additionally, Royon et al. (2007) found that adding tert-butanol to the system results in higher methanolysis conversion when utilizing Candida antarctica.

To counteract inhibition by methanol, a lower chain alcohol, tert-butyl was chosen as the solvent. The objective of this study is to economically produce biodiesel feedstocks, specifically waste-cooking oil, using Candida Antarctica Lipase B enzyme for catalyzing the transesterification reaction.

The Chrompack CP 9001 gas chromatograph from Holland is used for determining biodiesel yield.

Significance of the Study

Oil pollution is a significant problem, accounting for about 25% of all pollution incidents. The illegal disposal of oil in drainage systems, land, or waterways is considered a crime and has detrimental effects on river birds, fish, and other wildlife species. Even small amounts of oil can have severe negative impacts. In the UK alone, the catering industry generates an estimated 50 - 90 million liters of waste cooking oil every year.

If not disposed of properly, oil pollution can have devastating effects on the environment. The EPA

estimates that over 200 million gallons of used oil are improperly discarded and end up in the trash or water annually. This study aims to promote an affordable method of producing biodiesel using household waste materials such as waste cooking oil. By doing so, it seeks to address the expensive production costs of biodiesel and decrease environmental harm caused by excessive fossil fuel consumption. The results of this research will be crucial in meeting societal needs and addressing the economic challenges posed by high gasoline prices.

The benefits of lipases in biodiesel production are varied. They can operate in different types of systems, including biphasic and monophasic systems with hydrophilic or hydrophobic components (Am. J. Biochem. & Biotech., 6 (2): 54-76, 2010). Lipases are robust and versatile enzymes that can be easily produced on a large scale due to their extracellular nature in most production systems. Many lipases show significant activity in catalyzing transesterification with long or branched chain alcohols, which are difficult to convert into fatty acid esters using traditional alkaline catalysts. Furthermore, the separation of products and byproducts in downstream processes is much simpler. Immobilizing lipases on a carrier allows for their repeated use after removing them from the reaction mixture, and when lipase is used in a packed bed reactor for transesterification, there is no need for a separation step. Additionally, lipases have higher thermostability and tolerance towards short-chain alcohols, making them highly suitable for biodiesel production (Bacovsky et al.).

References to previous studies (Kato et al., 2007; Robles et al., 2009) suggest that the cost of using lipase is an important factor to consider in enzymatic biodiesel production. The limitations of employing lipases

in this process are outlined below:

  • The initial activity may be compromised due to the size of the oil molecule (Marchetti et al.).

Various challenges related to biodiesel production have been addressed in several studies. According to Robles et al. (2008) and Robles et al. (2009), the use of solvents does not fully protect the enzyme from the inhibitory effect of low chain alcohol, such as methanol. While high levels of free fatty acids (FFAs) in waste cooking oil do not affect lipase, the problem lies in the high water content (Robles et al., 2009). Moreover, Akoh et al. (2007) and Basha et al. (2008) emphasize that the regioselectivity of the enzyme limits biodiesel production using lipase to specific feedstocks.

Review of Related Literature

Biodiesel has proven its ability to meet the energy demands of various sectors including transportation, agriculture, commercial, and industrial sectors of the economy, according to Akoh et al. (2007) and Basha et al. (2008).

Several studies (Marchetti et al., 2009; Shafiee and Topal, 2009; Robles et al., 2009) estimate that the global annual diesel consumption is approximately 934 million tons. Canada contributes about 2.14% to this total, while the United States accounts for around 19.06%.

According to Xu and Wu (2003), Vasudevan and Briggs (2008), Robles et al. (2009), and Leung et al. (2010), biodiesel has become the main alternative fuel for compression ignition engines due to its environmentally friendly characteristics, renewable properties, and capability of being used with little or no adjustments. It is worth noting that the notion of biofuel is not a recent development.

In 1911, Rudolph Diesel was the first to use peanut oil in a diesel engine (Akoh et al., 2007;

Antczak et al., 2009). The substitution of biofuels for traditional fuels can help reduce global warming by decreasing emissions of sulfur, carbon oxides, and hydrocarbons (Fjerbaek et al., 2009). Biodiesel is often combined with diesel fuel at ratios of 2%, 5%, and 20% due to its economic advantages and higher power output (Vasudevan and Briggs, 2008).

According to research conducted by Fukuda et al. (2001) and Harding et al. (2007), increasing the ratio of biodiesel to diesel leads to a decrease in carbon dioxide emissions. The study found that when using a blend containing 20% biodiesel, there was a 15.66% reduction in net carbon dioxide emissions (Fukuda et al., 2001). Additionally, Vasudevan and Briggs (2008) discovered that pure biodiesel eliminates net carbon dioxide emissions.

Transesterification is the superior technique for mass production of biodiesel in terms of environmental impact, cost efficiency, and output yield when compared to alternative methods. The process involves a reversible series of steps wherein a triglyceride reacts with an alcohol to generate esters and glycerol. To facilitate ester formation, a slight surplus of alcohol is employed. Alcohol-based transesterification comprises three consecutive reversible reactions that first convert triglycerides into diglycerides.

The conversion process of triglycerides consists of three steps: the metamorphosis of diglycerides into monoglycerides, the transformation of monoglycerides into glycerin molecules. These transformations have been analyzed by Freedman et al. (1984), Noureddini and Zhu (1997), and Marchetti et al. (2008). According to Murugesan et al., each step generates a fatty acid alkyl ester (FAAE) molecule. Hence, three FAAEs are acquired from every triglyceride molecule.

Triglycerides are converted into diglycerides, which then transform into monoglycerides. In the process of biodiesel production, the transesterification reaction converts monoglycerides

into glycerin molecules (Bacovsky et al., 2009). To speed up this procedure, catalysts like alkaline compounds, acids, or enzymes are used.

Several studies have demonstrated that the selection of catalysts significantly affects the purity of the necessary feedstock, reaction rate, and post-reaction processing requirements (McNeff et al., 2008; 2007; Murugesan et al., 2009; et al., 2010).

Using heat is an ineffective and energy-intensive method to speed up the reaction. The inefficiency arises from the low yield of FAAE below 350°C and the risk of ester bonds breaking at temperatures above 400°C (Ranganathan et al., 2008). Typically, keeping the reaction mixture slightly above alcohol's boiling point (71-72°C) speeds up the process. The outcome of the reaction depends on factors like temperature, alcohol to oil ratio, catalyst concentration, and mixing intensity (Marchetti et al.).

The text mentions that alkalis, acids, or enzymes can be used as catalysts for the transesterification process. However, in commercial applications, sodium hydroxide (NaOH) is the preferred alkali catalyst.


  • Novozyme CABL L (LIPASE CABL) can be obtained from Novozyme (Denmark).
  • All other chemicals can be purchased from Sigma- Aldrich (St.

Louis, MO, USA). Grown in the laboratory, Candida appears as large, round, white or cream (albicans is from Latin meaning 'whitish') colonies with a yeasty odor on agar plates at room temperature.

Immobolization of Lipase

Sol – gel immobilization in an amphiphilic matrix was shown in figure below; mL of CABL (8. 2 mg/ml) is to be placed in a 50-ml Falcon tube with 1-mL of 0. 2 M phosphate buffer (pH 7).

To initiate the reaction, a catalyst of 1M sodium fluoride (50 microliters) is added to the mixture and stirred with a vortex mixer. Subsequently,

TMOS (2 mM) and the hydrophobic alkylsilanes listed below (8 mM) are introduced: methyltrimethoxysilanes (MTMS), ethyltrimethoxysilane (ETMS), propyltrimethoxysilanes (PTMS), and iso-butyltrimethoxysilane (iso-BTMS). Usually, gelation occurs within a few minutes as the reaction vessel is gently shaken. Once complete polymerization has transpired over 12 hours in a sealed Falcon tube, the gel is dried for 24 hours using an open Falcon tube. The gel is then subjected to successive washes of 10 mL each of distilled water, 99.8% iso-propanol, and 95% n-hexane.

The immobilized CALB needs to be filtered using filter paper. After that, it should be dried at 30 degrees Celsius for 36 hours and then ground with a mortar and pestle. Next, the particles should be sorted using 500 and 300 micrometer sieves. Finally, the particles should be stored at 4 degrees Celsius until they are ready to be used.

Enzyme Solution

The solution of immobilized P. cepacia lipase is prepared by adding 0. g of lipase to 1 ml of distilled water. It is then soaked in water for 30 minutes before being used.

This step is found experimentally essential to activate the enzymes.

Waste-Cooking Oil Preparation

In order to ensure consistency, waste cooking oil is simulated from the commercially available palm oil by heating 1 L of palm oil on a hot plate (Stuart, U. K.), set at its maximum heating power for two hours. The oil is then allowed to cool to room temperature and then 5 ml of water (around 5000 ppm) is to be added.

The sample is stored for a period of two weeks before being utilized. Fresh samples of Waste Cooking Oil (WCO) were prepared every two weeks. The

production of biodiesel using C. Antarctica Lipase will be carried out in a specifically designed reactor cell with a capacity of 150 ml, which is equipped with a jacket for temperature control. The cell will be placed on a magnetic stirrer from Velp Scientifica, Italy, to assist in stirring the mixture.

A temperature controlled water bath (Grant Instruments, UK) was used to circulate water through the jacket and maintain a constant temperature of 45 oC for the reaction media. This temperature was selected based on literature findings that identified it as the optimum (M. M. Soumanou, et al, 2003; H. Fukuda, et al, 2001). An appropriate agitation speed was chosen to ensure proper mixing without compromising the enzyme's activity.

At the start of each experiment, the working volume was 50 ml. This consisted of 5 g of WCO and varying volumes of methanol, ranging from 0.4 to 0.8 ml (equivalent to 0.57 to 1.

The experimental setup includes adding tert-butyl solution and 14 molar equivalents of ester bonds in the triglyceride chain to the total volume. The cell should be tightly covered to prevent evaporation. Once thermal equilibrium is reached, 1 ml of enzyme solution with 0.4% g of C is added.

The reaction is initiated by adding Antarctica lipase per g oil. At specific intervals, 1.5 ml samples are taken and placed in a capped vial. The vial is then immediately immersed in boiling water for at least 5 minutes to denature the enzyme and halt the reaction. The samples are subsequently sent for analysis. The Gas Chromatograph (Chrompack CP 9001, Holland) will be used to determine the quantities of FAMEs in the samples.

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