Biodiesel Production through the Transesterification of Non-Edible Plant Oils Using Glycerol Separation Technique with AC High Voltage

The primary energy source in the world today is fossil fuels. They are extensively utilized as raw quantifiable materials in the manufacturing of petrochemical goods and to serve a variety of industries, including transportation, agriculture, and household products [1]. The world may soon face an energy crisis based on the current energy situation. The rising global population and fast pace of economic development mean that energy consumption continues to rise, making the energy problem worse every day [2]. Frying oils, vegetable oils, animal fats, and oil created by microorganisms can all be used to make biodiesel [3,4]. However, there are a number of benefits to using second-generation biodiesel made from essential oil plants, such as its ability to facilitate high biofuel production and to lower greenhouse gas emissions [5]. The first stage in the manufacturing of biodiesel, however, is the selection of the feedstock, which requires the consideration of a number of attributes, including the composition, purity of the fuel, yield, and cost. The primary criteria for classifying biodiesel into edible, non-edible, and unused-based origins are obtainability and the kind of feedstock source used [6].

Oilseed plants called jatropha are grown in marginal semi-arid regions. Scrub can be harvested twice a year, is often disliked by cattle, and can continue to be productive for thirty to fifty years. Seeds can be obtained from the plant a year after planting, and productivity peaks after five years [7].

Pongamia (Pinnata (Karanja)) is a member of the Leguminaceae family. It is able to withstand severe weather and is widely distributed over marginal fields, riverbanks, and coastal regions. Flowering begins after 4–5 years. It is a semi-deciduous leguminous tree that fixes nitrogen and is resistant to drought [8]. The Karanja tree grows quickly, its fruits ripen 4–7 years after planting [9], and 9 to 90 kg of seeds can be produced over a period of 4 to 6 years [8].

The oil content of jatropha seeds ranges from 27 to 59% [10,11]. The major fatty acids found in the seed oil are linoleic, oleic, stearic, and palmitic acids, comprising 22.5% saturated fatty acids and 77.5% unsaturated fatty acids [12]. Amounts of 46% of oleic acid, 27% of linoleic acid, 6% of linolenic acid, and 0.1% of low-molecular-weight fatty acids, including lauric and capric acids, are found in pongamia seeds [13]. Because it can grow in a variety of soil types, pongamia possesses non-edible oil and tremendous potential for producing biodiesel [14]. The primary barriers to using vegetable oils directly as fuel are their higher molecular weights, higher viscosities, poor cold flow characteristics, low volatilities, and tendencies to form deposits due to poor combustion [15].

Since alkali catalysts require little reaction time, even at room temperature, they are frequently utilized for the transesterification of oils [16]. Bronsted acids, such as sulfonic acid and sulfuric acid, are another class of catalysts employed in transesterification. As explained in [17], transesterification is carried out using an acid catalyst if the amount of free fatty acids (FFAs) is greater than 1%. This reaction requires a lot of alcohol and the use of regulated conditions for a long time, including a high temperature of 100 °C and a pressure of 5 bar [18], lowering the triglycerides’ acid values as a result, and subsequently permitting transesterification catalyzed by alkali. Moreover, the yield is frequently greater than 95% when biodiesel is created by transesterifying triglycerides, the primary component of vegetable oils, with alcohol and an alkali catalyst at low temperatures and pressures [19]. After an ideal reaction period of 0.5–1.0 h, the separation of biodiesel from the glycerol by-product indicates a successful transesterification reaction [20,21,22]. Following transesterification processes, the biodiesel layer must be removed from the glycerol, and additional purification is required [23]. Since glycerol (1050 kg/m³) and biodiesel (approximately 880 kg/m³) have sufficiently different densities and are not mutually soluble, simple and straightforward separation techniques like centrifugation and gravitational settling can be applied [24,25]. Typically, there are traces of catalyst, glycerol, oil and its contaminants, and alcohol in the biodiesel layer [26]. Palm oil, a common raw material in the food sector, has been used to create biodiesel from fatty acids. With a molar ratio of 1:6, methyl alcohol is a solvent in which 1 weight percent of potassium hydroxide (KOH) can be used as a catalyst. A reactor chamber was used to prepare the 100 cc of substrate needed for the biodiesel synthesis reaction. The coaxial cylindrical electrode in a specially constructed chamber was made up of an outer tube electrode and an inner rod electrode. In order to compare the products with a control sample devoid of an electric field, exposure times of 5, 10, 15, and 20 min were chosen, and high voltage levels of 1.0, 2.5, and 5.0 kV were used. It was discovered that an electric field can significantly accelerate the reaction for the synthesis of biodiesel [27].

Low-quality fuel that has not been adequately purified causes serious engine issues, such as filter blockage, coking on injectors, high carbon deposits, extreme engine wear, engine banging, the thickening of lubricating oil, and the formation of lubricating oil deposits [6]. Numerous factors, including the quality of the raw materials, the composition of the fatty acids, the production process, the refining procedure, and the final production parameters, influence the fuel qualities of biodiesel. Biodiesel’s fuel qualities can be categorized using a variety of factors. The low-temperature properties (cloud point, pour point, cold filter plugging point, etc.); transport and storage properties (microbial contamination, induction period, oxidation and hydrolytic stability, flash point, temperature limit infiltration, etc.); and wear of engine parts (cleaning effect, lubrication, viscosity, compatibility with materials used in fuel system production, etc.) are the factors that have the greatest effects on engine events [28].

The three main facets of sustainability that are addressed by global biodiesel issues are social, environmental, and economic [29]. Profit maximization and reduced manufacturing costs are the main goals of economic sustainability. This calls for the development of new, ideally inedible raw materials and the application of waste- and energy-saving technology [29]. The reduced environmental burden is the main component of environmental sustainability. Employment and the utilization of local resources for the benefit of the community are the two main components of social sustainability. The studies that have been examined indicate that microalgae, fat, oils, and grease; various solid wastes; and other non-edible raw materials are viable and promising biodiesel substitutes [29]. Therefore, this study highlights biodiesel synthesis from non-edible plant oils such as pongamia and jatropha using a glycerol separation technique with an AC high voltage method through the transesterification reaction. Moreover, the objective of the experimental work presented in this paper was to evaluate and determine the ideal operating parameters for the transesterification of two non-food oils, pongamia and jatropha, as well as how these parameters affected the characteristics of the biodiesel that was produced. In addition, the study introduces how the created biodiesel fuel behaves when burned in a diesel engine.