Biodiesel

Biodiesel is a diesel-equivalent alternative fuel derived from biological sources such as edible and nonedible oils, animal fats, and waste cooking oils through processing. In addition to being a transportation fuel, biodiesel is also used in some jurisdictions for electricity generation in engines and turbines. The world’s biodiesel supply grew from 3.9 billion liters in 2005 to 18.1 billion liters in 2010 and is expected to exceed 33 billion liters in 2016 and reach 41.4 billion liters in 2025, a 25% increase over 2016 levels. Biodiesel prices have been facing downward pressure due to low global petro-diesel prices, however, blending mandates have largely sheltered the biodiesel market by lending consistency to demand. International prices of biodiesel are expected to increase in nominal terms over the next 10 years driven by the recovery of crude oil markets and prices of biofuel feedstock. It should be mentioned that the majority of countries producing biodiesel feedstock also have a vibrant domestic market and most or all of their supply is used to meet domestic mandate-driven demand. This dual role, as both producer and consumer, partially explains the limited international trade in biodiesel feedstocks. Most of the limited biodiesel trade over the next 10 years is expected to be composed of Argentina’s exports to the US. While there is a debate on the sustainability of biodiesel, many studies using lifecycle assessment (LCA) have demonstrated that biodiesel results in 20–80% less greenhouse emissions when compared to petro-diesel. As crude oil becomes more energy intensive to extract and refine, expected efficiency gains in biodiesel feedstock production and refining, the commercialization of second-generation biodiesel using nonfood feedstocks, combined with the growing market share of biodiesel will result in further reduction of harmful climate-impacting emissions by replacing petro-diesel with biodiesel.

The dwindling of fossil resources has prompted producers of fuels, fine chemicals, and polymers to switch from fossil carbon sources and search for renewable feedstock. Biomass holds one of the keys to this transition to a circular economy. In this context, biodiesel obtained by transesterification of natural oils with alcohols is gaining importance in the fuel sector. Various reactor concepts have been developed for the transesterification reaction. Depending on the scale of the biodiesel production plant, reactors with varying designs are operated in the batch, semi-batch mode, or continuously. In this chapter, the optimal reactor technologies are analyzed with respect to the stages the chemical conversion runs through. The initial reaction mixture of natural oil and methanol, the most common alcohol in biodiesel production, is characterized by a liquid–liquid two-phase system. The high polarity difference of natural oil and methanol leads to a mixability gap and formation of a natural oil-rich phase and a methanol-rich phase. The mass transfer of the reagents across the phase boundary is slow relative to the chemical reaction, thereby resulting in diffusion limitations. Various mixing technologies, such as sonication, and the use of microreactors are explored to overcome these diffusion limitations. Once the reaction is 15–20% complete, the reaction mixture becomes homogeneous, reducing the need for intensive mixing. As the reaction continues and higher conversions are obtained, the fatty acid methyl ester separates from glycerin. The two phases are separated and purified. Recent technologies for process intensification aim at enhancing mass and heat transfer at all stages of the reaction.

Biodiesel is a renewable fuel, produced from waste cooking oils, animal fats, vegetable and algae oils. Its use is intended to replace diesel in conventional diesel engines, causing lower polluting emissions. To produce biodiesel, certain details must be carefully considered, namely feedstock composition, reaction parameters, process conditions, process equipment, purification processes, analysis of biodiesel properties, troubleshooting and storage. In what concerns feedstock composition, parameters such as acidity, insolubles, moisture, phospholipids, sulphur, polymerized triglycerides, impurities, etc., must be determined to decide about the pretreatment steps (washing, degumming, filtration, bleaching, deodorization, among others) to be implemented, and the need for esterification prior to transesterification. In what concerns the selection of process equipment some questions arise, namely the materials, heating methods and thermal insulation to use, alternatives to enhance the reaction, need for neutralization and process control system. The purification process includes biodiesel purification, methanol recovery and glycerine valorisation. The excess methanol must be recovered from biodiesel and glycerine by distillation and reused in the process while glycerine can be further purified and sold for application from the chemical to the pharmaceutical industry. The quality of biodiesel must be certified by the analyses performed according to the standards (e.g. EN 14214, ASTM D6751). Troubleshooting is needed in biodiesel production during start-up and under steady production of a facility; problems may arise regarding quality and appearance of biodiesel, reaction conditions, methanol removal, stirring in reactors, glycerine and biodiesel separation, as well as excess of water and other feedstock impurities. Biodiesel can be stored for up to 6 months; its storage poses challenges concerning degradation by contact with air and light, which cause oxidation. Some additives could extend the lifespan of biodiesel by increasing oxidation stability; other technique is the fractionation to remove the undesired fatty acid methyl ester (FAME).

Biodiesel purification is a crucial process in meeting fuel grade standard specifications. Inadequate purification results in a low-quality fuel and hampers engine performance. Conventional wet and dry washing along with membrane refining technologies are the most discussed methods in the literature for biodiesel purification. The conventional wet washing is performed using organic solvents, deionized water, or an acid solution. However, these methods result in a large quantity of wastewater, which creates a significant cost for wastewater treatment besides environmental impacts. Dry washing techniques were introduced to address this deficiency. In these methods, an appropriate adsorbent media such as Magnesol, an ion exchange resin, or active carbon is utilized to remove the impurities. The challenges associated with wet and dry techniques motivated scientists to seek more innovative techniques. Regarding biodiesel purification, organic and ceramic membrane technologies have received increasing attention. Biodiesel upgrading is an alternative route for producing diesel-like fuels with properties that can exceed conventional petroleum diesel. Since oxygenated moieties of biodiesel are the main reason for its poor fuel properties (e.g., high viscosity, low energy density, low chemical stability, and poor cold flow behavior), most of these upgrading techniques have focused on deoxygenation pathways. Hydrodeoxygenation using various catalytic systems have also been studied extensively to produce renewable diesel with high yields and high carbon efficiency. This chapter presents the basics and applied aspects of biodiesel purification and upgrading along with an overview on different techniques, challenges, and the overall trend of research.

This chapter reviews the applications of biodiesel by-products. The biodiesel production process is predominantly carried out through transesterification of triglycerides with methanol. Besides the desirable methyl esters, this process provides other products including oil cake/meal, crude glycerol, methanol, and biodiesel wash-water. Oil cake/meal are solid residues obtained after oil extraction from the seeds. The by-product of the transesterification step is crude glycerol. To remove the impurities, crude methyl esters will be washed out which result in the biodiesel wash-water that is another potential by-product. Many applications are known for the aforementioned by-products and also the unreacted methanol. This chapter starts with a brief introduction on biodiesel process. It will continue with reviewing applications of biodiesel process’s by-products and unreacted methanol.

In this chapter, the importance of risk assessment in biodiesel-based economy is first discussed. The importance of risk analysis to identify the most promising production schemes is also discussed from an economic point of view. Next, a systematic framework for economic risk assessment of biodiesel production processes and its associated by-products is presented. The application of the framework is highlighted through the production of 1,2-propanediol and 1,3-propanediol as value-added products from glycerol, which are critically assessed in terms of its techno-economic performance through the estimation of economic indicators, net present value (NPV), and minimum selling price (MSP). The Monte Carlo method with Latin Hypercube Sampling (LHS) is used to propagate the market price and technical uncertainties to the economic indicator calculations and to quantify the respective economic risk. In order to decrease the economic risk, the integrated production of the product as a module added to the biodiesel plant was tested as an alternative scenario. Using the integrated concept of utilizing the waste glycerol stream in biodiesel plants contributes to the diversification of the product portfolio for vegetable oil-based biorefineries, and in turn improves cost-competitiveness and robustness against market price fluctuations. The developed generic framework can be applied to other biodiesel by-products to assess the potentials of obtaining value-added products from them. Finally, future perspectives and other approaches toward economic production of biodiesel with lower risks are highlighted. The framework proposed in this work is to provide some detailed perspectives to facilitate the economic risk analysis of biodiesel production for any given technology.

The main aim of this chapter is to provide an overview of the technical and economical characteristics of biodiesel production plants. A literature review of various techno-economic feasibility studies of biodiesel production is conducted. Moreover, outcomes of these evaluations are reported to present potential commerciality and near-term technical viability of biodiesel plants from different regions. In this chapter, various technological possibilities and economic aspects involved in the production of biodiesel are outlined. Significant effort is made to ensure that common assumptions are used as the basis for the comparison among conversion technologies. In addition, this analysis constitutes of the input feedstock needed, environmental considerations, energy balances, and detailed economic assessment including the cost component structures for biodiesel. Conclusions made in this study are merely indicative of the expected performance of biodiesel production plants based on the current state of public knowledge. These findings can aid in conducting significant comparisons between different technologies for producing biodiesel and exploring scenarios with optimal biodiesel production configurations.

Like all energy carriers including renewable energies, the production to combustion cycle of biodiesel should also be assessed from the sustainability point of view. Life cycle assessment (LCA) is a promising approach capable of assisting decision makers to find the environmental consequences of the existing or future biodiesel production plans. For instance, for different feedstocks, production technologies, downstream processes implemented, etc., an LCA of biodiesel production cycles could result in different recommendations ranging from agricultural practices to production and combustion stages. Despite the fact that an ISO standard is available for conducting LCA studies, there are still many challenging issues faced when performing LCA studies concerning biodiesel production and consumption. These challenges include the functional unit, the choice of system boundaries, the impact categories to be assessed, the treatment of land use change, and biogenic carbon. The present chapter provides a systematic overview of the above-mentioned topics with the aim of shedding light on various aspects of LCA of biodiesel production and consumption cycle.

Sustainability has become a relevant issue for the biodiesel industry. As a consequence, increasingly advanced engineering methods and metrics are being applied to make decisions on biodiesel production and combustion systems in order to achieve the most thermodynamically, economically and environmentally sound synthesis pathways and conditions. Among the various approaches developed, exergy-based methods exhibit significant promise for the quantitative and qualitative evaluation of energy conversion and biofuel production processes. Exergy-based analyses provide valuable insights into the performance, costs and environmental impacts of biodiesel production and combustion systems. In this chapter, after briefly describing the exergy concept and its theoretical background, an overview is provided of the most important researches relating to the application of this approach and its extensions for analyzing biodiesel production and combustion systems. In general, quantifying exergy destruction rate and exergy efficiency is the greatest focus of researchers globally when applying exergy method in this domain. However, applications of extended exergy-based methods like exergoeconomic and exergoenvironmental analyses, as comprehensive decision-making paradigms for evaluating, optimizing, and retrofitting biodiesel production and combustion processes, are limited. Future research is needed into finding the most efficient, cost-effective, and environmental-friendly routes for biodiesel synthesis and its subsequent utilization, using exergoeconomic and exergoenvironmental approaches together with advanced knowledge- and evolutionary-based optimization techniques.