A Review of the Emission, Performance, Combustion, and Optimization Parameters in the Production of Biodiesel from Waste Cooking Oil

Automotive Experiences Vol. 5 No. 3 (2022) pp. 371-388 p-ISSN: 2615-6202 e-ISSN: 2615-6636 A Review of the Emission, Performance, Combustion, and Optimization Parameters in the Production of Biodiesel from Waste Cooking Oil Dae Ho Park , Feyisola Idowu Nana, Haeng Muk Cho Department of Mechanical Engineering, Kongju National University, Republic of Korea https://doi.org/10.31603/ae.7005 Published by Automotive Laboratory of Universitas Muhammadiyah Magelang collaboration with Association of Indonesian Vocational Educators (AIVE) Abstract Article Info Submitted: 13/04/2022 Revised: 07/06/2022 Accepted: 07/06/2022 Online first: 20/06/2022 With the rising consumption of energy comes the challenge of the depletion of fossil fuels. Fossil fuels are non-renewable and finite energy sources with increasing energy demand as a result of the rise in human population and industrialization. This concern has led researchers to seek alternative energy sources that are both economically, technically viable, and environmentally beneficial. Biodiesel is considered an alternative source of energy supply. It is non-toxic, biodegradable, carbon-neutral, and ecologically friendly. However, the high cost of producing biodiesel from feedstocks impedes its commercialization. Hence, WCO used in the production of biodiesel helps to reduce the overall cost of production. The characteristics of the performance, emission, and combustion of the biodiesel produced from the transesterification of WCO are reviewed in this study. The molar ratio of methanol to oil, the concentration of the catalyst, reaction temperature, and time were used to investigate the optimization parameter required in the synthesis of biodiesel from WCO. The number of times the catalyst can be reused while maintaining a good catalytic activity in biodiesel production was also studied. The optimization models and techniques for the prediction of biodiesel yield were also studied. Keywords: Waste cooking oil; Catalyst; Optimization parameter; Emission; Performance; Combustion characteristics 1. Introduction The rapid rise of the human population, urbanization, industrialization, and transportation requirements have increased global energy demand. These energy demands and the rise in the global economy raise the concern of fossil fuel depletion [1]. The use of fossil fuels poses environmental risks such as greenhouse gas and pollution emissions [2]–[4]. These fossil fuels are finite, non-renewable, and with an increased cost have led researchers to an alternate energy source that is technically feasible, economically viable, and ecologically friendly. Biodiesel is a clean, safe, biodegradable, renewable, non-hazardous, carbon-neutral, and can be used as an alternative source of energy [5]. Biodiesel can be produced from either edible or non-edible feedstock. Examples of feedstock used in the production of biodiesel include karanja, palm, soybean, canola, sunflower, jatropha, rapeseed, etc [6]–[9]. Biodiesel can be produced via the transesterification process in which triglycerides from feedstocks react with alcohol in the presence of a catalyst [10]–[16]. Among the different types of alcohol used in the production of biodiesel, methanol is the most frequently used and it’s specially selected because of the physical and chemical advantage it possesses. The scheme showing the transesterification of the triglycerides with methanol for the production of methyl esters is shown in Figure 1 [17]. Biodiesel may also be used as a partial or complete replacement for diesel fuel in compression ignition engines for automotive locomotion or energy generation. The This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. Automotive Experiences 371 © Dae Ho Park, Feyisola Idowu Nana, Haeng Muk Cho Figure 1. Schematic of the transesterification process [17] diesel engine can be operated without any engine modification when using biodiesel either in its neat or blended form [18]–[21]. Biodiesel outperforms diesel fuel in terms of flashpoint, lubricity properties, and cetane number, with no discernible difference in heat of combustion. It also has kinematic viscosity and a specific gravity greater than diesel [13]–[14]. Biodiesel has also demonstrated a remarkable benefit in terms of reducing unburned hydrocarbon (UHC), smoke, carbon monoxide (CO), and particle matter (PM), but with the nitrogen oxide (NOx) emission slightly increasing [15]–[16]. Different types of catalyst have been used by many researchers and some of which has been discussed in this study. The transesterified catalysts can either be homogeneous or heterogeneous. The simplest approach is homogeneous transesterification; however, due to the homogeneity of the mixture and the existence of some difficulties in the product separation and purification steps involving the reactant, catalyst, and product; the heterogeneous transesterification process was preferred as it was cheaper with less difficult steps [26], [27]. A twostep trans-esterification process was used to remove the high FFA concentration and boost biodiesel production. Transition metal oxides, hydrotalcite, silica-based, and alkali-doped materials have all been used by different researchers in heterogeneous catalyst systems [27]–[29]. The most widely used alkali catalyst in the production of biodiesel is sodium hydroxide (NaOH) and potassium hydroxide (KOH); however, the alkali catalyst of KOH yielded better results [27], [30]. Several techniques such as central composite design (CCD) based on response surface methodology (RSM), Raman spectroscopy, Automotive Experiences thermogravimetric analysis (TGA), scanning electron microscope (SEM), x-ray diffraction (XRD), x-ray absorption near-edge spectroscopy (NEXAFS), Brunauer, Emmett and Teller (BET), Fourier transform infrared spectroscopy (FTIR) among others have been used to perform the analysis [24]–[25]. The brake specific fuel consumptions (BSFC), brake thermal efficiency (BTE), heat release rate (HRR), ignition delay, and cylinder pressure were obtained to analyze the performance and combustion characteristics of the WCO biodiesel operated on a diesel engine. Similarly, the exhaust gas emissions of CO, CO2, unburned HC, NOx, smoke, exhaust gas temperature (EGT), and particulate matter are also used to investigate the emission characteristics. The optimization parameters of molar ratio of methanol to oil, catalyst concentrations, reaction temperature and time as well as catalyst reusability in the production of biodiesel were also discussed in the study. 2. The WCO Cost Analysis Abdallah El-Gharbawy [32] studied the cost analysis of producing biodiesel from WCO. A biodiesel power plant with a capacity of 100,000 tons per year was used in the study. The study showed that the production of biodiesel at optimum conditions achieved a maximum 99% biodiesel conversion rate. The study revealed that the cost of producin (...truncated)