1.
Introduction
Currently, emphases have been shifted to the use of locally sourced materials for the production of renewable fuels. Biofuels are renewable energy sources produced from plant or animal materials. They are believed to be viable alternatives to fossil fuels (e.g. crude oil, coal and natural gas). For more than 150 years, fossil fuels have been fueling economies, and they now provide nearly 80% of the world's energy. Fossil fuels are well-known for releasing stored carbon and other greenhouse gases into the atmosphere when burned [1]; 73% of the CO2 emission is caused by the burning of fossil fuels [2]. The EIA-Energy Information Administration projects an almost 50% increase in global energy use by 2050, led by growth in renewables [3]. An increase in human population and industrialization means an increase in fossil fuel utilization and an increase in environmental waste generation. However, these challenges could be curbed if more transitions to renewable energy sources are observed [4]. Biodiesel is one of the most commonly produced biofuels and it is also referred to as fatty acid methyl ester (FAME). It is a clean-burning fuel made by transesterifying triglycerides, which are the major component of different feedstock oils like fresh and used vegetable oil including oil from algae and animal fat, with alcohol in the presence of a catalyst [5]. Biodiesel contains an energy content of 33 MJ/L [6] and it is used to power compression-ignition (diesel) engines, just like petroleum-based diesel. Biodiesel can be used in pure form (B100) or it can be mixed with petroleum fuel in any ratio such as B2 which represents 2% biodiesel and 98% petroleum diesel, B5 which denotes 5% biodiesel and 95% petroleum diesel, and most popular blend, B20 which is a blend comprising 20% biodiesel and 80% petroleum diesel [7]. In Nigeria, biodiesel production has the capacity to strengthen the nation's energy security and benefit local communities economically. The sector does, however, face some difficulties, such as technological constraints, financial viability and social and environmental implications [8].
The country has a large agricultural sector which validates its potential for biodiesel production. Despite this, the biodiesel industry remains underdeveloped, and there is a knowledge gap regarding its current situation. Comprehensive studies on the availability, viability and cost of different feedstocks, as well as the economic viability of biodiesel production, distribution and use in the nation are lacking. Furthermore, the challenges facing the industry such as issues with feedstock quality and processing, have not been thoroughly investigated, and the social and environmental impacts of biodiesel production and use in Nigeria have not been sufficiently evaluated [9,10]. To fully understand the potential of biodiesel in Nigeria and create effective policies and strategies to encourage its expansion, it is imperative to address these knowledge gaps. The goal of this literature study is to give an overview of the Nigerian biodiesel sector as it currently stands. The evaluation will examine the properties and benefits of biodiesel, prospective biodiesel feedstock, government regulations and incentives for the sector and the sustainability of the biodiesel industry. The evaluation will also look at the challenges the sector is now facing as well as the social and environmental effects of biodiesel use and production in the country.
2.
Properties of biodiesel
The characteristics of biodiesel give a clue as to whether or not it would be appropriate for the engine's performance, longevity and emissions [11]. Biodiesel's poor qualities at low temperatures and its low oxidation stability are the two main issues that need to be resolved in order to use it. These come about as a result of the physical and chemical characteristics of the principal biodiesel constituents, fatty acid methyl esters (FAME), as well as certain other minor constituents that form during the transesterification process. Cetane number, viscosity, cloud point, pour point, cold filter plugging point (CFPP), specific gravity, flash point, iodine value and heating value are important characteristics that are directly related to FAME and are some of the properties of biodiesel that distinguish it from petroleum-based diesel [12].
The cetane number is a measure of how well a fuel ignites. The higher the cetane number, the more efficiently a car's engine burns fuel. Viscosity is a measure of the thickness or resistance to flow of the liquid fuel. The lower the viscosity of the fuel the better to allow for better flow and combustion [13]. The cloud point is the temperature at which a fuel begins to solidify i.e. the temperature at which wax crystals begin to form in the fuel. The lower the better because a higher cloud point can result in clogging of fuel filters and poor cold weather performance. Pour point is the temperature at which fuel ceases to flow. A lower pour point allows the fuel to flow more easily in cold temperatures. CFPP is the lowest temperature at which the fuel will pass through a standardized filter. A lower CFPP gives an indication that the fuel can be used at lower temperatures without clogging the fuel system [14]. Specific gravity is the density of biodiesel compared to the density of water [15]. The flash point is an indicator of a fuel's combustibility or flammability. Simply put, flash point is the temperature at which a fuel will ignite when exposed to a spark or flame. Compared to petroleum-based diesel, biodiesel has a higher flash point which means it is less flammable [16]. The iodine value is an indicator to examine the degree of unsaturation or the number of double bonds in the fatty acid chains. A lower iodine value indicates that the fuel has higher oxidative stability, and hence, is better for storage and use [17]. Heating value is the amount of energy released when a fuel is burned. A higher heating value indicates a greater amount of energy available for use [18]. Some characteristics of biodiesel and No. 2 diesel fuels are given in Table 1.
3.
Benefits of biodiesel as a renewable energy
Governments in the majority of industrialized nations encourage the use of renewable resources and energies with the following key objectives: (i) to secure access to energy, (ii) to mitigate climate changes, (iii) to develop/maintain agricultural activities and (iv) to ensure food safety [20]. Table 2 highlights some of the advantages of biodiesel production and utilization.
4.
A brief on Nigeria's biodiesel industry
Nigeria's biodiesel sector is still in its early phases of development but has enormous growth potential. Nigeria currently has a small capacity for biodiesel production, but interest in the sector and investment have recently increased. The primary raw materials used to make biodiesel in Nigeria are palm oil, jatropha and other regionally cultivated crops. The most extensively utilized feedstock is palm oil because of its vast availability and moderate price. Jatropha has also drawn interest as a potential feedstock for biodiesel because of its high oil content and ability to grow in adverse conditions [24].
The growing interest in sustainable living and renewable energy is fueling an increase in the market demand for biodiesel in Nigeria. However, at the moment, Nigeria's demand for biodiesel is constrained by a lack of infrastructure, distribution methods and consumer knowledge and comprehension of the fuel's advantages. The government of Nigeria has put laws and incentives in place targeted at boosting biodiesel production and consumption in order to assist the industry's expansion in the country. In addition to rules aimed at boosting the use of biodiesel in the transportation sector, these policies also include tax credits and subsidies for the production of biodiesel [25]. Essentially, Nigeria's biodiesel industry is at present characterized by low production capacity, a wide range of feedstocks and rising consumer demand. Although there is the potential for significant future expansion, obstacles still need to be surmounted if Nigeria is to enable the emergence of a viable biodiesel industry [26].
5.
Potential biodiesel feedstock in Nigeria
Four categories of feedstocks can be used to produce biodiesel: first, second, third and fourth-generation feedstocks. Biofuels from second, third and fourth-generation feedstock are called advanced biofuels. Certain factors have been outlined to influence the deployment of advanced biofuels and these include (a) the accessibility/availability of feedstock (b) access to capital, particularly for investments in the development and testing of novel technologies (c) the impact of policy and regulation (d) support for advanced biofuels market adoption (e) consumer confidence and (f) investor confidence [27]. Figure 1 gives a flow diagram of biodiesel production from the four categories of feedstocks.
5.1. First-generation feedstocks
Crops that have been extensively farmed for food production, such as palm oil, coconut oil, soybean oil, sunflower oil and rapeseed (canola) oil are examples of first-generation feedstocks [29]. These feedstocks are widely accessible in Nigeria. However, their use for biodiesel production has been challenged. The concern about using first-generation feedstocks comes from the fear that they can lower the production of food for consumption, and not for biodiesel production; they can compete with food production for land and resources, which can lead to higher food prices and food insecurity in some regions. In addition, the use of first-generation feedstocks for biodiesel can have negative environmental impacts, such as deforestation, habitat destruction and increased greenhouse gas emissions [30]. The drawbacks associated with the utilization of first-generation feedstock for biodiesel production have led to a growing interest in the development of second, third and fourth-generation feedstocks. These feedstocks aim to address these drawbacks to provide a more sustainable source of renewable energy [31].
5.2. Second-generation feedstocks
Crops that are cultivated solely for the purpose of generating energy and not for food are considered second-generation feedstocks [32]. Castor, jatropha, mahua, yellow oleander, tung and pongamia are examples of second-generation feedstocks [33]. These feedstocks have the benefit of having a low environmental effect and not competing with food crops, but farmers have several concerns growing them such as; the availability of land, dedicating land to a single crop for an extended period of time, the impact of energy crops on the quality of the land, relative financial return and cash-flow considerations and knowledge of or familiarity with the crop, etc [34]. Also, they are less accessible than first-generation feedstocks.
5.3. Third-generation feedstocks
Microalgae are considered the potential feedstock for the production of third-generation biodiesel. Microalgae have the potential to produce more oil per hectare of cultivated area compared to conventional biodiesel crops. Microalgae are unicellular organisms that can produce high quantities of lipids (oils) under the right conditions, such as high light intensity, temperature and the availability of nutrients like nitrogen and phosphorus. Some species of microalgae can produce oil content of up to 50% or more of their dry weight. The possession of high lipid content makes them one of the most promising feedstocks for biodiesel production [35]. Table 3 gives the yield of some feedstock considered for biodiesel production. Conventional biodiesel crops, such as soybean and rapeseed, typically have oil contents of about 20–42% of their dry weight [36–38]. This means that it would take more land to produce the same amount of oil compared to microalgae. Microalgae have the added advantage of being able to grow in a wide range of environments, including brackish water and wastewater, which are not suitable for conventional crops. This means that microalgae can be grown on non-arable land, avoiding competition with food crops. Nevertheless, for microalgae to be a viable and sustainable source of renewable energy, there are many technical and economic challenges that need to be addressed [39].
5.4. Fourth-generation feedstocks
Fourth-generation feedstocks for biodiesel production are the most advanced but not yet widely adopted or commercialized as they are still in the development and experimental stages. They include genetically modified microorganisms such as microalgae and cyanobacteria [42]. These microorganisms utilize solar energy, water and CO2 to produce biofuels. The number of steps required to absorb and convert solar energy into biofuels is reduced by genetically and metabolically modifying the microorganisms that can produce them. Genetic modification can also be used to increase the capture of CO2 (thus decreasing emissions into the environment) and improve lipid production [43]. Biofuels from this category of feedstock are anticipated to have a significantly higher photon-to-fuel conversion efficiency in relation to other feedstock categories [32]. Presently, there are limited studies and research on the use of fourth-generation feedstocks for biodiesel production in Nigeria, and their viability and environmental impact are still being evaluated.
6.
Assessment of availability, sustainability and cost of feedstock for biodiesel production
6.1. Availability
First-generation feedstocks like palm oil are readily available in Nigeria whereas second-generation feedstocks such as jatropha are still being developed and are not as widely grown. Third-generation feedstocks are also in the early phases of development. There are surprisingly few reports on the cultivation of microalgae in Nigeria. However, many of these microalgae species thrive in abundance in Nigeria's natural aquatic settings, particularly during the rainy season, in gutters, ditches, ponds, puddles, rivers, seas and oceans. In both wet and dry conditions in Nigeria, these organisms have been seen to spontaneously flourish. Furthermore, there have been some attempts to examine the potential of algae as a feedstock for the nation's biodiesel production and the outcomes thus far have been encouraging [44].
6.2. Sustainability
Second-generation feedstocks are thought to be more sustainable since they have a lesser environmental impact than first-generation feedstocks, which have been criticized for their negative effects on the environment, such as deforestation and biodiversity loss. Though second-generation feedstock and biodiesel production methods from these feedstocks are effective, if they compete with food crops for limited land, their production can become unsustainable. Therefore, the sustainability of their products will depend on how well producers adhere to requirements such as minimum lifecycle GHG reductions, including land use modification and social norms [45]. Of all, third-generation feedstocks are considered to be the most environmentally friendly option for biodiesel production as they have a low carbon footprint and do not compete with food crops for land and resources. Algae, for example, can be grown in open ponds or closed photobioreactors, which can be located on non-arable land, reducing the impact on agricultural land and wildlife [46].
6.3. Cost
In terms of cost, third-generation feedstocks are currently more expensive to produce when compared to first and second-generation feedstocks, as the technology and processes involved are still in the development stage. However, as technology improves and production processes become more efficient, it is expected that the cost of producing third-generation feedstocks will decrease [47].
In addition to the above, fourth-generation feedstock possibly have the potential for higher productivity than aforementioned generations. Nevertheless, the cost of production and their scalability may be a challenge, and their sustainability will depend on factors such as energy and resource inputs.
7.
Government policies and incentives for biodiesel in Nigeria
The government has set various policies and incentives to aid in the development of the biodiesel sector, however, these policies are still not well established and not often effectively implemented. Government subsidies that aim to lower the cost of biodiesel production and stimulate the use of this renewable fuel, are one of the key motivations for the production and use of this fuel in Nigeria. These subsidies can take the form of financial assistance or tax credits for biodiesel producers, or direct subsidies to the end-users of biodiesel, such as transportation companies or farmers [48].
In addition to providing subsidies, the Nigerian government has also developed rules and specifications for the production and use of biodiesel. These rules seek to provide fair play for all biodiesel producers while also guaranteeing that the quality of biodiesel produced in the nation matches international standards. The Nigerian biodiesel sector is still in its infancy and hasn't yet reached its full potential despite these regulations and incentives. The industry is faced with some obstacles, such as a lack of investment and infrastructure, a lack of knowledge and understanding of the advantages of biodiesel, and a lack of loan availability for small and medium-sized biodiesel producers [49]. Nevertheless, there is tremendous room for expansion. The government should step up by creating successful policies and incentives in order to realize this potential. This entails working with industry stakeholders to address the issues preventing the sector's expansion and advancing the study and creation of environmentally friendly, sustainable biofuel technologies. The government should promote the use of biodiesel in transportation and other industries, as well as support private sector investment, to help the biodiesel industry grow even further. Easy availability to fuel will increase demand and open up business opportunities for farmers and entrepreneurs who can provide the raw materials for biodiesel production. This will be made possible by a well-established distribution network [50].
The biodiesel industry can as well benefit greatly from the support of private companies. They may aid in the development of the sector by making investments in cutting-edge technology and teaching people about the advantages of biodiesel and the necessity for sustainability in the energy industry [51]. In general, the interaction of governmental regulations and incentives, private sector investment and the creation of new technology will determine the success of the biodiesel industry in Nigeria; the biodiesel industry can expand and have a big impact on the nation's energy security and economic growth with the appropriate confluence of these factors.
8.
Economic viability of biodiesel
The cost of production, distribution and use, as well as the availability of government subsidies and tax credits, are important considerations for determining the economic sustainability of biodiesel production and use in Nigeria [52].
(a) The cost of feedstocks, which can vary based on the type of feedstock and its availability, is one of the main factors determining the economic sustainability of biodiesel production. Feedstock like Jatropha can demand greater investment in terms of land and water resources, whilst feedstocks like palm oil, are easily accessible and relatively inexpensive.
(b) Another crucial element is the cost of production, which influences both the overall cost of biodiesel and its ability to compete with alternative fuels. The technology employed, the accessibility of production facilities and the price of raw materials can all have an impact on production costs.
(c) Regarding distribution, the cost of moving biodiesel from production facilities to end-users can have a substantial impact on the industry's overall economic viability. The creation of a strong distribution network becomes essential in expanding access to biodiesel and lowering transportation costs.
(d) The potential of government subsidies and tax breaks can affect how economically viable biodiesel production and use in Nigeria are. The use of tax credits and government subsidies, for instance, can encourage investment in the sector and increase the use of biodiesel as a fuel source while also helping to offset production costs and increase biodiesel's competitiveness with other fuels.
For the biodiesel sector in Nigeria to be successful over a long term, it is essential to conduct a detailed analysis of the costs and benefits of production and use [53].
9.
Challenges for biodiesel development
Biodiesel development faces difficulties everywhere in the world. In developing nations, these difficulties are far more pronounced. The quality of feedstock is one of the challenges the biodiesel sector in Nigeria faces. The composition of the feedstock, the amount of free fatty acids and the water concentration have all been found to have an impact on the yield and quality of biodiesel. However, the production methods employed determine how much of an impact this effect has [54]. In essence, the effectiveness of processing and the general quality of the finished product can both be impacted by the quality of the raw materials. To overcome these challenges, it is crucial to make investments in the research and development of feedstock production technologies as well as establish quality control procedures to guarantee feedstocks adhere to the requirements for the production of biodiesel.
The effectiveness of processing is another significant issue the Nigerian biodiesel company is confronted with. There may be production bottlenecks that affect the overall efficiency and cost-effectiveness of biodiesel production. The processing of feedstocks into biodiesel requires specialized equipment and technical know-how. It is crucial to make investments in new processing technologies and to collaborate with stakeholders to develop more efficient production methods in order to overcome these obstacles [55]. Broader environmental and sustainability concerns should also be addressed when considering the development of the biodiesel industry in Nigeria. For instance, using first-generation feedstock may have negative impacts on the environment and biodiversity, raising questions about the long-term viability of these resources [56]. The lack of adequate manpower and expertise in the biodiesel industry in Nigeria has been identified as a factor also limiting its development. This can impact the quality of feedstock, processing and production and hinder the growth of the industry. In order to overcome these challenges, it is important to invest in human capital development, provide training and education to workers, and encourage the development of local expertise in the field. Additionally, collaboration with international organizations and institutions could also help to bring in the necessary technical knowledge and expertise to help the industry overcome these challenges and achieve sustainable growth in the future [57].
Other competing economic difficulties facing the developing countries as well as lack of political will on the side of the government and policymakers are also recognized obstacles to the rapid development of biodiesel in the country [58].
10.
Social and environmental impact of biodiesel
When assessing the feasibility of the industry, it is crucial to take into account the social and environmental effects of biodiesel production and use. Impacts on land use are one of the key issues since growing feedstocks for biodiesel production might displace other crops and cause deforestation. This could affect local communities by causing a loss of resources and land, as well as lead to the extinction of species and other environmental problems [59]. The effect of biodiesel production on greenhouse gas emissions should also be taken into account. Although biodiesel is promoted as a more environmentally friendly substitute for fossil fuels, the production can nevertheless cause greenhouse gas emissions through the cultivation and processing of the feedstocks. It is crucial to carefully analyze the lifecycle emissions of biodiesel and to take action to reduce these emissions, such as choosing sustainable feedstocks and enhancing production process efficiency [60].
To minimize the social and environmental negative impacts of biodiesel production and use in a country, it is important to implement sustainable and responsible production practices. This could entail working with local communities to ensure that their rights and interests are protected and taking steps to minimize the environmental impact of biodiesel production, such as using sustainable feedstocks and reducing greenhouse gas emissions. When these steps are taken, the biodiesel industry in Nigeria can contribute to a more sustainable future for the country and its populace.
11.
Life cycle assessment of biodiesel production
A life cycle assessment (LCA) of biodiesel production from the four generations of feedstock involves analyzing the environmental impacts of the entire life cycle of the production process, from feedstock cultivation to biodiesel use. This includes evaluating parameters like water consumption, land use changes, energy use and greenhouse gas emissions. Comparing the LCAs of the four generations of feedstock could help to determine the most sustainable and environmentally friendly options for biodiesel production [61]. First-generation feedstocks have been associated with negative impacts on food security, deforestation and biodiversity loss. Second-generation feedstocks have lower impacts on food security but still require significant inputs of energy and chemicals during cultivation and processing. Third-generation feedstocks have the potential to reduce environmental impacts and increase yields per hectare but their cultivation and processing technologies heavily rely on water and they are still in the early stages of development [62]. Fourth-generation feedstocks aim to overcome some of the limitations of preceding generations by increasing yields, reducing inputs and minimizing land use change and other negative impacts. However, their potential environmental impacts and social implications are still uncertain and need to be carefully evaluated before widespread adoption [63,64].
12.
Conclusions
This study shows that the biodiesel industry in Nigeria has potential for growth especially when there is proper support from the government and private sector. The economic viability of biodiesel must be considered in terms of production and distribution costs, as well as government subsidies and tax credits. There are technological challenges that need to be addressed, such as feedstock quality and processing. Additionally, there are social and environmental impacts to consider, including land use changes and impacts on local communities. The future of the biodiesel industry in Nigeria looks promising with potential for further research and development, technological advancements and increasing demand for sustainable fuels. Future works should concentrate on developing effective and affordable biodiesel production processes, investigating the possibilities of new feedstocks like microalgae and enhancing the sustainability of current feedstocks through improved land-use management techniques. Furthermore, incentives should be offered and a supportive environment created by policymakers and the private sector to promote the expansion of Nigeria's biodiesel industry. The focus of this study is on Nigerian biodiesel production which may limit the generalizability of the findings to other geographical areas. Also, the estimate of the economic viability of biodiesel production is based on the current market condition and might not be applicable in the future. Notwithstanding these drawbacks, this study offers insightful information about the difficulties and prospects of Nigerian biodiesel production and emphasizes the need for additional research and development in this field.
Acknowledgments
The author thanks the anonymous reviewers in particular for their suggestions to enhance the work.
Conflict of interest
The author declares no conflicts of interest.
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