Biodiesel Is Dead: Long Life to Advanced Biofuels—A Comprehensive Critical Review

Abstract

Many countries are immersed in several strategies to reduce the carbon dioxide (CO2) emissions of internal combustion engines. One option is the substitution of these engines by electric and/or hydrogen engines. However, apart from the strategic and logistical difficulties associated with this change, the application of electric or hydrogen engines in heavy transport, e.g., trucks, shipping, and aircrafts, also presents technological difficulties in the short-medium term. In addition, the replacement of the current car fleet will take decades. This is why the use of biofuels is presented as the only viable alternative to diminishing CO2 emissions in the very near future. Nowadays, it is assumed that vegetable oils will be the main raw material for replacing fossil fuels in diesel engines. In this context, it has also been assumed that the reduction in the viscosity of straight vegetable oils (SVO) must be performed through a transesterification reaction with methanol in order to obtain the mixture of fatty acid methyl esters (FAMEs) that constitute biodiesel. Nevertheless, the complexity in the industrial production of this biofuel, mainly due to the costs of eliminating the glycerol produced, has caused a significant delay in the energy transition. For this reason, several advanced biofuels that avoid the glycerol production and exhibit similar properties to fossil diesel have been developed. In this way, “green diesels” have emerged as products of different processes, such as the cracking or pyrolysis of vegetable oil, as well as catalytic (hydro)cracking. In addition, some biodiesel-like biofuels, such as Gliperol (DMC-Biod) or Ecodiesel, as well as straight vegetable oils, in blends with plant-based sources with low viscosity have been described as renewable biofuels capable of performing in combustion ignition engines. After evaluating the research carried out in the last decades, it can be concluded that green diesel and biodiesel-like biofuels could constitute the main alternative to addressing the energy transition, although green diesel will be the principal option in aviation fuel.

Performance analysis of a bio-diesel fired engine bottoming with micro-ORC

“…Biodiesel exhibits biodegradability, renewability, a high cetane number, a high flash point that make it suitable for storage and transportation [3], [4]. The main technology for the exploitation of the biodiesel is the compression ignition engine which does not require particular changes in the architecture [5]. This is confirmed by the research conducted on biodiesel in the last decades [6].…”

Engine Performance Using Blended Fuels of Biodiesel and Eco Diesel

“…However, biodiesel has several disadvantages, such as poor volatility and high viscosity that reduce the engine's performance [15,16]. Furthermore, Biodiesel from vegetable oils has energy content close to petro-diesel and is regarded as inexhaustible because of its renewable energy source [17,18]. Abdollahi et al [19] examined the effects of nano-emulsion biodiesel on engine efficiency, as well as the gas emission and combustion parameters of a single-cylinder air-cooled diesel engine.…”

Adaptive neuro-fuzzy inference system for forecasting corrosion rates of automotive parts in biodiesel environment

“…The dose and kind of catalyst used, the molar ratio, the temperature, and the time essential to produce the ester are all factors that affect (m)ethyl yield [ 4 ]. Owing to its enhanced cetane number, superior lubricity, lesser sulfur content, and advanced flash point, biodiesel has outperformed fossil fuels in admiration [ 5 ]. It has unwanted poor cold flow features, advanced viscosity, and volatility, and is more predisposed to corrosion or degradation of APs [ 2 ].…”