Biodiesel is an environmentally friendly fuel used in diesel engines. It is produced through the chemical processing of vegetable or animal fats, in addition to the products of the transesterification process.
This type of fuel is renewable and biodegradable, and is made from many natural sources, including vegetable oils such as soybean oil, rapeseed oil and palm oil, or animal fats, or recycled restaurant grease, which contributes to reducing organic waste.
Chemically, this fuel is a mixture of mono-alkyl esters of fatty acids, often of the methyl or ethyl type, and can be used either in its pure form or mixed with conventional petroleum diesel fuel in varying proportions.
Biodiesel can be used in most standard diesel engines without radical modifications, either in its pure form known as "P100", or more commonly as a mixture with petroleum diesel, such as the two types "P5" which contains 5 percent biodiesel, and "P20" which contains 20 percent. In addition, biodiesel improves the lubrication properties of the injection system, which helps to reduce wear on internal engine parts and extend their service life.
It is worth noting that the first engine that runs on biodiesel was launched on August 10, 1893, and therefore this date is considered World Biodiesel Day in commemoration of this achievement.
The next important development took place in 1897, when Rudolf Diesel, the inventor of the diesel engine, displayed an engine powered by peanut oil at the International Exhibition in Paris, indicating at that early stage that vegetable oils might eventually become as important as fossil fuels, and perhaps even surpass them in some future applications.
However, due to the low prices of crude oil and its extraction in large quantities, interest in biofuels declined rapidly during the early decades of the twentieth century, and this interest was revived only during periods of energy crises and wars, as was the case during and after World War II when oil supplies were scarce, while the production of biodiesel began to grow at a remarkable rate in the seventies of the twentieth century following the global oil crisis.
Biodiesel has several key advantages compared to conventional petroleum diesel, the first of which is that it is renewable, as raw materials such as oilseed plants and olive trees can be replanted in relatively short agricultural cycles, unlike limited and depletable petroleum reserves that take millions of years to form.
This unconventional fuel is environmentally friendly and burns cleaner, significantly reducing harmful emissions. Studies indicate that biodiesel can reduce greenhouse gas emissions by up to 86 percent over its lifecycle and carcinogenic compounds by up to 94 percent compared to petroleum diesel. Furthermore, it is virtually sulfur-free, minimizing sulfur oxide emissions that contribute to acid rain. It is also non-toxic and biodegradable, reducing the risk of soil and groundwater contamination in the event of an accidental spill during transport or storage.
Biofuels also have a higher flash point, at around 150 degrees Celsius compared to around 55 degrees Celsius for petroleum diesel, making them safer to handle and store, and reducing the risk of unintended ignition.
Despite these obvious advantages, biodiesel has disadvantages that limit its spread, most notably its relatively high cost, as its production is often more expensive than traditional fuels due to the costs of cultivating, harvesting, transporting and processing the raw materials, in addition to the energy consumption in the esterification and purification process.
One of its drawbacks is that it competes with the food industry. If the raw materials used are food crops such as rapeseed, soybeans, or corn, the increased demand for them may lead to higher food prices, raising ethical and economic problems in poor areas.
One of its technical drawbacks is that it freezes or becomes more viscous in cold weather. At sub-zero temperatures, its viscosity increases significantly, making it difficult for it to flow within the injection system and hindering engine operation, especially in cold regions.
Fuel also decomposes over time as a result of the biological activity of bacteria and fungi, especially if it contains a percentage of water, which leads to the formation of deposits and acidity that may damage the metallic components. In addition, it has a harmful effect on some materials such as rubber and paints used in fuel hoses and non-metallic parts, which necessitates the use of resistant materials in the design of engines.
For all these reasons, biodiesel is an important step towards achieving a more sustainable and diversified energy mix, but its widespread adoption is subject to addressing a number of technical, economic and social challenges. Nevertheless, experts believe that in the future it will be one of the main sources of renewable energy, especially with the development of second and third generation technologies that rely on non-food biomass and algae.
Until 2022, the member states of the European Union, Indonesia, the United States, Brazil and Argentina were among the world’s leading producers of biodiesel, having enacted supportive policies and tax incentives to encourage its production and consumption.
Interestingly, in recent years, interest in biodiesel has declined somewhat in the United States, the European Union, and Brazil, with the focus shifting towards bioethanol derived from corn and sugarcane, which is used more in gasoline. However, biodiesel retains its place in the heavy transport, shipping, and agriculture sectors, where it is difficult to replace easily.
