An Overview of Bio/Renewable Fuels for Cars and Aeroplanes

Governmental agencies around the world have become increasingly interested pursuing the development of alternative energy sources and engines to replace the conventional gasoline-powered internal combustion agency. For example, the United States federal government has demanded that all vehicles will be able to achieve at least 54.5 miles per gallon by the year 20251. To meet this demand, numerous different fuel alternatives and their related automotive infrastructures have been introduced into the transportation market, some of which include:

  • Gas-electric hybrids
  • Plug-in Hybrids
  • Electric Vehicles (EVs)
  • Ethanol and Flex Fuel
  • Biodiesel
  • Propane
  • Liquified and compressed natural gas
  • Hydrogen-powered Fuel Cells
  • Solar
  • Steam

The Success of Biodiesel

Through a process known as esterification, biodiesel is originally derived from various agricultural resources including oils sourced from vegetables, soybeans, canola, sunflower and recycled cooking products, as well as animal fats. Through this process, an industrial alcohol, such as ethanol or methanol, combined with a catalyst are both used to convert the agricultural oil into a biodiesel that takes the form of a fatty-acid methyl-ester fuel. In its pure form, biodiesel is referred to as B100; however; biodiesels can also be combined with conventional diesels to form B5 and B20 fuels which are 5% and 20% biodiesel, respectively, with the remaining percentage being conventional diesel fuel2. What is particularly unique about biodiesels is that they can be used in conventional diesel engines without requiring any type of additional equipment to be implemented into the vehicle.

Some of the current applications of biodiesel include:

  • On-Road Vehicles:
    • Fleet vehicles
    • Heavy-duty trucks
    • School and urban transit buses
  • Off-Road Vehicles:
    • Marine vessels
    • Equipment for various industries, of which include:
      • Agriculture
      • Construction
      • Forestry
      • Mining
    • Trains
  • Stationary Applications:
    • Electricity generators
    • Furnaces3

Hydrogen Fuel for Transportation

Whether it is used as a fuel cell or within an internal combustion engine, hydrogen fuel can be applied in a wide variety of transportation vehicles to significantly reduce emissions while maintaining a quiet and efficient ride in the process. Both the European Commission and U.S. Department of Energy have determined that hydrogen is a critical alternative energy source that has the potential to meet the energy needs of a wide range of energy applications ranging from stationary equipment needs, transportation, industrial and residential purposes4. The main attraction of utilizing hydrogen fuel is attributed to the complete elimination of any emissions other than water, its ability to be produced from a wide variety of other energy sources and combine with fuel cells to further improve sustainable energy supplies.

Hydrogen fuel can be formed from a number of chemical processes, some of which include:

  • Steam methane reforming
  • Auto-thermal reforming of oil
  • Gasification of coal and other hydrocarbons
  • Electrolysis of water
  • Biomass conversion
  • Nuclear energy
  • Biological processes4

Natural Gas Sources

Although natural gas accounts for approximately 30% of the total energy currently used in the United States, only about two-tenths of 1% of transportation fuel utilizes natural gas, despite its reliability as an energy source for this industry. Compressed natural gas (CNG) has become a highly popular alternative automotive fuel in many countries around the world as a result of its ability to reduce CO2 emissions by as much as 25%. Furthermore, when combined with hydrogen, CNG is capable of achieving even a greater reduction in CO2 emissions5. Currently, CNG can be used for light-, medium- and heavy-duty applications, during which CNG is stored in a compressed gaseous state at a pressure of up to 3,600 pounds per square inch within the vehicle.

On the other hand, liquified natural gas (LNG), which is stored in vehicles in a liquid state, is produced as a result of natural gas purification, followed by a cooling period that brings the LNG fluid to -260 ºF until it is ultimately returned to a liquid state5. By cooling the liquid below its boiling point, most of the extraneous compounds are easily removed from the fuel to result in a product that contains primarily methane with small trace amounts of other hydrocarbon compounds. LNG is currently used as fuel for ships, trucks and buses that are equipped with specifically designed fuel tanks capable of utilizing this fuel source to power these transportation vehicles6.

References

  1. “10 alternatives to the gasoline-powered engine” – Fortune
  2. “Biodiesel” – EPA
  3. “Biodiesel – Applications” – Natural Resources Canada
  4. Singh, S., Jain, S., Venkateswaran, P. S., Tiwari, A. K., Nouni, M. R., Pandey, J. K., & Goel, S. (2015). Hydrogen: A sustainable fuel for future of the transport sector. Renewable and Sustainable Energy Reviews, 51; 623-633. DOI: 10.1016/j.rser.2015.06.040.
  5. “Natural Gas Fuel Basics” – U.S. Departmetn of Energy
  6. “Natural Gas Explained – Liquified Natural Gas” – U.S. Energy Information Administration

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