Biodiesel

"Green diesel" redirects here. For dyed fuel, see Fuel dyes.
This article is about transesterified liquids. For hydrogenated alkane renewable diesel, see hydrotreated vegetable oil. For biomass and organic waste-to-fuel production, see Biomass to liquid. For unmodified vegetable oil used as motor fuel, see Vegetable oil fuel.
For broader coverage of this topic, see Biofuel.
Experimental French Régiolis Class train using biodiesel
Space-filling model of ethyl stearate, or stearic acid ethyl ester, an ethyl ester produced from soybean or canola oil and ethanol
Two general pathways for biodiesels from a fat. The process starts with hydrogenation of backbone double bonds. Fatty acid methyl esters can then be produced by transesterification. C16 and C18 diesel fuels arise by hydrogenolysis of the saturated fat.

Biodiesel is a renewable biofuel, a form of diesel fuel, derived from biological sources like vegetable oils, animal fats, or recycled greases, and consisting of long-chain fatty acid esters. It is typically made from fats.[1][2][3]

The roots of biodiesel as a fuel source can be traced back to when J. Patrick and E. Duffy first conducted transesterification of vegetable oil in 1853, predating Rudolf Diesel's development of the diesel engine.[4] Diesel's engine, initially designed for mineral oil, successfully ran on peanut oil at the 1900 Paris Exposition. This landmark event highlighted the potential of vegetable oils as an alternative fuel source. The interest in using vegetable oils as fuels resurfaced periodically, particularly during resource-constrained periods such as World War II. However, challenges such as high viscosity and resultant engine deposits were significant hurdles. The modern form of biodiesel emerged in the 1930s, when a method was found for transforming vegetable oils for fuel use, laying the groundwork for contemporary biodiesel production.

The physical and chemical properties of biodiesel vary depending on its source and production method. The US National Biodiesel Board defines "biodiesel" as a mono-alkyl ester.[5] It has been experimented with in railway locomotives and power generators. Generally characterized by a higher boiling point and flash point than petrodiesel, biodiesel is slightly miscible with water and has distinct lubricating properties. Its calorific value is approximately 9% lower than that of standard diesel, impacting fuel efficiency. Biodiesel production has evolved significantly, with early methods including the direct use of vegetable oils, to more advanced processes like transesterification, which reduces viscosity and improves combustion properties. Notably, biodiesel production generates glycerol as a by-product, which has its own commercial applications.

Biodiesel's primary application is in transport. There have been efforts to make it a drop-in biofuel, meaning compatible with existing diesel engines and distribution infrastructure. However, it is usually blended with petrodiesel, typically to less than 10%, since most engines cannot run on pure biodiesel without modification.[6][7] The blend percentage of biodiesel is indicated by a "B" factor. B100 represents pure biodiesel, while blends like B20 contain 20% of biodiesel, with the remainder being traditional petrodiesel. These blends offer a compromise between the environmental benefits of biodiesel and performance characteristics of standard diesel fuel. Biodiesel blends can be used as heating oil.

The environmental impact of biodiesel is complex and varies based on factors like feedstock type, land use changes, and production methods. While it can potentially reduce greenhouse gas emissions compared to fossil fuels, concerns about biodiesel include land use changes, deforestation, and the food vs. fuel debate. The debate centers on the impact of biodiesel production on food prices and availability, as well as its overall carbon footprint. Despite these challenges, biodiesel remains a key component in the global strategy to reduce reliance on fossil fuels and mitigate the impacts of climate change.

  1. ^ Murzin, Dmitry Yu.; Mäki-Arvela, Päivi; Simakova, Irina L. (2012). "Triglycerides and Oils for Biofuels". Kirk-Othmer Encyclopedia of Chemical Technology. pp. 1–14. doi:10.1002/0471238961.trigmurz.a01. ISBN 978-0-471-48494-3.
  2. ^ Paisley, Mark A. (2003). "Biomass Energy". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.0621051211120119.a01.pub2. ISBN 978-0-471-48494-3.
  3. ^ Huang, Daming; Zhou, Haining; Lin, Lin (2012). "Biodiesel: an Alternative to Conventional Fuel". Energy Procedia. 16 (Part C): 1874–1885. doi:10.1016/j.egypro.2012.01.287.
  4. ^ Demirbaş, Ayhan (2002-11-01). "Biodiesel from vegetable oils via transesterification in supercritical methanol". Energy Conversion and Management. 43 (17): 2349–2356. doi:10.1016/S0196-8904(01)00170-4. ISSN 0196-8904.
  5. ^ "Biodiesel Basics" (?). National Biodiesel Board. Archived from the original on 2014-08-04. Retrieved 2013-01-29.
  6. ^ Omidvarborna; et al. (December 2014). "Characterization of particulate matter emitted from transit buses fueled with B20 in idle modes". Journal of Environmental Chemical Engineering. 2 (4): 2335–2342. doi:10.1016/j.jece.2014.09.020.
  7. ^ "Nylund.N-O & Koponen.K. 2013. Fuel and Technology Alternatives for Buses. Overall Energy Efficiency and Emission Performance. IEA Bioenergy Task 46" (PDF). Archived (PDF) from the original on 2020-02-16. Retrieved 2021-04-18.