|
|
| Fig. 1: Jatropha Curcas Biodiesel. (Source: Wikimedia Commons) |
Fossil fuels play a major role in powering the transportation vehicles, machines, and power sources of the world. It is projected that global energy consumption will increase from 5.24 × 1017 Btu in 2010 to 6.3 × 1017 Btu in 2020 and 8.2 × 1017 Btu in 2040. [1] Growing concerns about the depletion of fossil fuel reserves, the impact of exhaust emissions on the environment, and an increasing global demand for energy have highlighted the importance of alternative fuel sources such as biodiesel. Vegetable oil is a viable alternative to fossil fuels; it is renewable, can be easily produced in rural areas that lack modern forms of energy production, and has a net zero carbon dioxide emission. [2] The use of non-edible oils as a source of biofuel eliminates the problem of depleting food supplies; these non-edible tree-based oil seeds have the potential to be transesterified to produce biodiesel. [3]
Biodiesel is a substitute for conventional diesel fuels that is chemically defined as the monoalkyl esters of long chain fatty acids derived from renewable vegetable oil and animal fat sources. [4] The impurities present in plant and animal oil prevent it from being used directly as fuel. Because of this, the oils must undergo chemical modification through the process of transesterification, where oils or fats are reacted with a monohydric alcohol through contact with a catalyst (a strong acid or base). [4] This process creates biodiesel that can be used in vehicles and machines that use compression ignition engines, which include many transportation vehicles and major machines used across the world.
Transesterification, also known as alcoholysis, is the process through which an alcohol is displaced from an ether by another alcohol; this process is similar to hydrolysis except that alcohol is used instead of water. [4] The process produces fatty acid alkyl esters and glycerol; the glycerol layer settles at the bottom of the container. [4] The reactions of the process are reversible, and the presence of a catalyst accelerates the conversion process. [4] The transesterification process is essential to the production of biodiesel, and the properties of the oil used impact the final fuel product.
One potential source of non-edible tree-based oil is the Jatropha curcas tree, a viable alternative to plants like soybeans and rapeseed often used in biodiesel production. Jatropha curcas is a tree belonging to the Euphorbiaceae family; it is native to the American tropics and grows in the tropical and subtropical regions of the world. [5] The plant grows in areas with poor soil and is drought resistant, requiring only 250 mm of rainfall to survive. [5] The Jatropha seed's oil content ranges from 30% to 50% in weight, containing about 14% free fatty acid (FFA); this oil content exceeds the limit of 1% FFA level that can be converted to biodiesel by a transesterification reaction using an alkaline catalyst. [2,3] The unsaturated fatty acids are classified as linoleic or oleic, and are composed of myristic, palmitic, stearic, arachidic, oleic and linoleic acids. [2] The fuel properties of Jatropha biodiesel (Fig. 1) are comparable to those of biodiesel, and are equivalent to the latest standards for biodiesel. [3] The high viscosity of Jatropha oil must be reduced or blended with diesel for use in engines. Based on its fuel properties, the use of Jatropha curcas as a biofuel plant has great potential, especially in underdeveloped nations.
The use of Jatropha biodiesel may present various
benefits, both to the environment and the economy. Burning vegetable
oil-based biofuels such as Jatropha biodiesel releases less carbon
dioxide into the air than burning fossil fuels, and large scale
production of the Jatropha plant could bring economic profits to
underdeveloped countries in South America and Africa where the plant
grows. Recent studies have shown that the use of other vegetable oils,
such as Moringa oleifera and
© Maya Navar. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] S. Bilgen, "Structure and Environmental Impact of Global Energy Consumption," Renew. Sust. Energ. Rev. 38, 890 (2014).
[2] K. Pramanik, "Properties and Use of Jatropha curcas Oil and Diesel Fuel Blends in Compression Ignition Engine," Renew. Energ. 28, 239 (2003).
[3] A. K. Tiwari, A. Kumar, and H. Raheman, "Biodiesel Production from Jatropha Oil (Jatropha curcas) with High Free Fatty Acids: An Optimized Process," Biomass Bioenerg. 31, 569 (2007).
[4] L. C. Meher, D. Vidya Sagar, and S. N. Naik, "Technical Aspects of Biodiesel Production by Transesterification - A Review," Renew. Sust. Energ. Rev. 10, 248 (2006).
[5] O. Kibazohi and R. S. Sangwan, "Vegetable Oil Production Potential from Jatropha curcas, Croton megalocarpus, Aleurites moluccana, Moringa oleifera and Pachira glabra: Assessment of Renewable Energy Resources for Bio-Energy Production in Africa," Biomass Bioenergy 35, 1352 (2011).
