From SEG Wiki
Jump to: navigation, search

Biofuels are energy sources derived from plants and other living matter, known as biomass. Common types of biofuels include ethanol and biodiesel.[1] The goal of biofuels is to be carbon neutral, so that the amount of carbon released into the atmosphere when the fuel is burned is equal to or less than the carbon removed from the atmosphere as the fuel source grows.[2]

Sources for biofuel

Biofuels come from various sources. Depending on the source, the biofuels are often referred to as first, second, third, or fourth generation fuels.

  • First generation biofuels are the ones commonly used today; they are created from sugars and starches heavily processed to create fuels. A few examples of first generation biofuels are ethanol, biodiesel, and biogases.
  • Second generation biofuels are made from crops with high concentrations of cellulose, the tough material of plants’ cell walls that form the structure of most plants.[3]
  • Third generation biofuels are made from plants that grow quickly, such as algae.
  • Fourth generation biofuels use plants genetically engineered for specific traits, such as high energy yields and easy cell breakdown, which make them desirable for biofuel processing.[4]

Common biofuels

Not all generations of biofuels are widely available to use; most second, third, and fourth generation fuels are still being researched to find the best way to process them to get the most energy efficiency and easy widespread use. Currently, ethanol and biodiesel are the most common biofuels in use today.

  • Ethanol is a type of alcohol and is often made with similar methods: primarily through fermentation. The ethanol is also modified so it is undrinkable. Another method of creating ethanol is using gasification, a process that uses high-temperatures and low oxygen to create synthesis gas, which can then be turned into various biofuels.[5] Ethanol is usually mixed with petroleum in the conventional gas most cars use, but it can also be used exclusively in cars with specially designed engines.
  • Biodiesel is a combination of alcohol and some type of oil, fat, or grease, usually vegetable oil, animal fat, or recycled cooking grease. It can be blended with regular fuel to reduce certain emissions or used as an alternative diesel fuel.[6]

Biofuel issues

The basic premise of biofuels is that the process of growing the source plants will remove the carbon dioxide (CO2) that using the fuels releases. Also, plants can be considered an infinite source: they can be grown over and over again without being used up. However, as the use of biofuels has spread, debates have arisen questioning whether biofuels are as environmentally friendly as they appear. Two major issues are that the amount of energy used to create biofuel can be greater than the energy available from the biofuel and the amount of water used in biofuel production.

Energy debate

Biofuels are generally considered carbon neutral because even though biofuels still release some CO2 when used, the plants that source biofuels remove CO2 from the air when they grow. However, fossil fuels are used in many stages of making biofuels, which increases the energy and CO2 cost of biofuels (how much energy it takes to make biofuels and how much CO2 is released during biofuel production). The machines that plant and harvest the biofuel crop run on fossil fuels, the plants that process the biofuels use fossil fuels during production, and the trucks that transport the plants to processing and the biofuels from processing also use fossil fuels. Adding up all the energy in the form of fossil fuels used to create biofuels, research indicates that the energy input for biofuels can be greater that the energy output biofuels produce.[7][8] Fortunately, the energy deficit problem mostly arises from the use of corn as a fuel source. Other fuel sources, such as sugarcane, often have higher energy yields. Ongoing research is also searching for other effective sources for biofuels.

The water issue

Water is a precious commodity; without it, life would not be possible. A 2009 study found that water usage for corn ethanol doubled between 2005 and 2008. Much of this increased usage is from corn grown in areas with little rainfall. In these areas, increased irrigation is needed to produce a crop of corn. This increased usage in these areas could exacerbate the problems of declining aquifers and other water sources in the areas. One reason farmers are growing corn in these areas despite the often unsuitable soil and rainfall is because of the increased subsidies and higher corn prices from biofuel production.[9] As the country continues to strive towards more home-produced fuels, farmers may continue to move into drier areas, therefore using more and more water.

See Also


  1. System of Registries | US EPA. (n.d.). Retrieved July 9, 2015, from
  2. Green Choices - Renewable Energy - Biofuels - What are Biofuels? (n.d.). Retrieved July 8, 2015, from
  3. Biofuel Facts, Biofuel Information - National Geographic. (n.d.). Retrieved July 8, 2015, from
  5. NREL: Learning - Biofuels Basics. (n.d.). Retrieved July 8, 2015, from
  7. Biofuels - National Geographic Magazine. (n.d.). Retrieved July 8, 2015, from
  9. McKenna, P. (2009, April 14). Measuring Corn Ethanol’s Thirst for Water. Retrieved July 16, 2015, from

External links

find literature about