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Introduction

The obvious needs of environmental sustainability, energy and economic securities has made it necessary to source energy alternatives which transfuses environmental friendliness with renewability, biodegradability, reduced toxicity and less dependence on petroleum products (Lv et al., 2019).

Waste cooking oil causes severe pollution especially in water bodies, which eventually leads to serious environmental problems. According to Rodrigues et al (2020), the release of used cooking oil into the environment could have disastrous impacts. A large number of hotels and restaurants dispose of their waste cooking oil with various forms of solid waste straight to landfills where it undergoes anaerobic digestion processes into methane and decomposes into methane, a hazardous greenhouse gas (25 times more climate-damaging than CO2 ) (Abed et al., 2018). The waste oil affects water bodies by polluting the aquatic environment and drinking water resources. The oil after reaching the water sources increases the organic pollution load, forming layers on the water surface to prevent oxygen exchange thereby altering the ecosystem (Capuano et al., 2017). The oil dumping also causes problems in pipes, obstructing them and promoting odors, and also increasing the cost of waste water treatment (Danov et al., 2017).

A way of  promoting  environmentally friendly methods of minimizing food waste is to turn food waste into energy through biodiesel production from waste cooking oils (Balasubramanian et al., 2020). Biodiesel is an alternative fuel which is biodegradable, and can be manufactured from food waste with a low cost and sustainable supply (Nogueira, 2011). It is considered to be a viable sustainable replacement for fossil fuels, due to the fact that it is renewable and it reduces carbon emissions into the atmosphere (Rodrigues et al., 2019). Biodiesel burns cleaner than petroleum-based diesel (Rakopoulos et al., 2016). When waste cooking oil is recycled, tons of waste cooking oil can be diverted from municipal sewage pipes, improving the quality of the environment (Sonthalia and Kumar, 2019). Biodiesel’s main benefits can be seen to be biodegradability, renewability, little or no contribution to the greenhouse effect, safety, and non-toxicity (Huang et al., 2012).

In recent years, there have been a show of concern to the problem of carcinogenic gutter oil. Using waste cooking oil in the production of biodiesel provides a suitable and profitable way to eliminate various raw materials of gutter oil (Milano, 2016). This brings side benefits to the local market. Asl et al (2020) proposes that the economic feasibility of biodiesel production from waste cooking oil is conclusively viable.

Various forms of vegetable oil can be used as feedstock for biodiesel production e.g. castor oil, neem seed oil, palm kernel oil, jathropha seed oil, sunflower oil, groundnut oil e.t.c. A main component of all these plants’ oil is Glycerol (a combination of three Free Fatty Acids and glycerol gives triglycerides in the oil).  Naturally, all forms of oil could be considered as a form of independent fuel, but the presence of glycerol would solidify them in our combustion engines (Singh et al., 2020).  Hence, biodiesel production just entails the removal of glycerol by reacting the feedstock with an alcohol in the presence of a catalyst (the transesterification reaction). Biodiesel can also be called ‘FATTY ACID METHYL ESTER’ as it is a mono-alkyl ester (Ding et al., 2018).

The transesterification reaction is sensitive to the feedstock purity requiring usually some pre-treatment operations (Sarno and Iuliano, 2018). The refined vegetable oils do not need a pre-treatment for biodiesel production. However, waste oils and animal fats have a lot of impurities such as free fatty acids (FFA) and water that negatively affect the reaction performance (Gülüm et al., 2020).

FFA is only considered during base catalysis. They can reduce the reaction rate by orders of magnitude (Chanakaewsomboon et al., 2020).

Also, FFA cannot be converted into biodiesel, forming instead soap, which limits the mass transfer between phases, significantly reduces the rate of chemical reaction and the selectivity of the reaction towards biodiesel, and further complicating phase-separation after the reaction is completed (Sadaf et al., 2018).

Feedstock with FFA contents higher than 1%(w/w) must be pre-treated to either eliminate the FFA or convert the FFA to esters before the “biodiesel generation” reaction is carried out (Karmakar et al., 2018). Otherwise, the catalyst will react with the FFA to form soap and water, The soap formation reaction is very fast and it completes before any tangible esterification reaction occurs. Apart from consuming the said catalyst, the saponification reaction also promotes the formation of emulsions, which creates downstream problems and complicates the post-treatment processes and purification of biodiesel (Gaurav et al., 2019).

Problem Statement

Waste is inevitable. Although unwanted by the disposing end, it might be an invaluable resource to another party. In this case, instead of waste cooking oil being disposed off into the environment, it can be recycled as a form of material reuse into a renewable fuel that has a greener impact in the energy sector and on the environment compared to our known petroleum-based product (Ma and Liu, 2019).

This study intends to carry out an analysis on the synthesis of biodiesel from waste cooking oil and carry out a research on various modifications to the whole process to get better biodiesel (better yield and better performance ratings of the biodiesel) from the route. It also intends to perform an evaluation on the synthesis and purification of the by-product (glycerol), which could also be an important sub-process, as glycerol is a useful feedstock used in the production of soap and other cleansing agents (Brock et al., 2020).

Aim and Objectives

The aim of this project is to evaluate the synthesis of biodiesel and glycerol from waste cooking oils, with the following objectives;

• Objective 1: Optimizing the most feasible process route and its optimum arrangement to ensure optimum yield of the desired products (Eze et al., 2018).
• Objective 2:  Using the most suitable catalyst for the transesterification reaction taking into account the chosen  process route.
• Objective 3: Obtaining a maximum selectivity of the process reaction towards the production of biodiesel.
• Objective 4:  Obtaining an optimum yield of biodiesel from the process reaction considering the various process variables.
• Objective 5:  Ensuring an efficient and optimal separation between the different fluid phases after the occurred process reaction (Suthar et al., 2019).
• Objective 6:  Carrying out a sensitivity analysis on the entire process dynamics.

Research Questions

The identified research questions for this project are provided below:

• What is the best process route and its optimal arrangement for this desired synthesis?
• How would the feedstock be acquired?
• How do we determine the optimum catalyst for the desired transesterification reaction?
• How do we tackle the “free fatty acid” problem? (Kara et al., 2018)
• Taking into account various constraints, how do we attain optimal selectivity and maximum yield of the most desired product?
• What is the optimal duration for the completion of the process reaction?
• What is the optimum separation process required for the fluid phase separation?
• What is the optimal duration for the completion of the phase separation?
• How does a change in various process variables affect the overall process dynamics?
• How is result testing carried out?

Deliverables

The deliverables of these project are a project report, samples of the synthesized products and gotten results. The synthesized products would be tested according to industry standards and literature to see how they compare with required standards.  Also, the report should contain a complete documentation of how the laboratory experiment was carried out, how various process variables were gotten, how the desired products were synthesized and how the results were arrived at.

Relevance

This project mainly focuses on the optimal synthesis of biodiesel from the waste cooking oils, and the purification of the attained glycerol as its by-product.

Methodology

This project focuses on secondary research, laboratory experiments and process analysis, and they are discussed below:

Secondary research

The secondary research in this project will utilize a systematic approach (Johnson et al., 2016) to review the works of literature. The steps involved in the systematic review of the literature are provided below:

• Step 1: Identify the research questions that can be used for the project.
• Step 2: Identify the keywords that should be used to research the works of literature.
• Step 3: Extract the journals and books that are appropriate for this project.
• Step 4: Write the literature review chapter.

Laboratory experiments

The laboratory experiments would cover a large chunk of this project. They would be carried out in stages, and as such described below;

• Stage 1:  Sourcing for the required feedstock (waste cooking oils)
• Stage 2:  Sourcing for the desired process catalyst.
• Stage 3:  Developing an appropriate process route and optimal equipment arrangement for an efficient process setup (Photaworn et al., 2017)
• Stage 4:  Carrying out the transesterification reaction.
• Stage 5:  Analyzing the process reaction.
• Stage 6:  Carrying out the phase separation.
• Stage 7:  Purification of the attained by-product.
• Stage 8:  Results Testing.

Process Analysis

The totality of the process reaction would be analyzed and this would also occur in stages;

• Stage 1:  Process Testing
• Stage 2:  Process Control
• Stage 3:  Process Optimization

Evaluation

The risk assessment conducted for this project is provided in the table below:

Table 1:  Risk assessment