What are the sources which can produces biofuel?

A biofuel is a fuel that contains energy from geologically recent carbon fixation. These fuels are produced from living organisms. Examples of this carbon fixation occur in plants and microalgae. These fuels are made by a biomass conversion (biomass refers to recently living organisms, most often referring to plants or plant-derived materials). This biomass can be converted to convenient energy containing substances in three different ways: thermal conversion, chemical conversion, and biochemical conversion. This biomass conversion can result in fuel in solid, liquid, or gas form. This new biomass can be used for biofuels. Biofuels have increased in popularity because of rising oil prices and the need for energy security. However, according to the European Environment Agency, biofuels do not necessarily mitigate global warming.

Bioethanol is an alcohol made by fermentation, mostly from carbohydrates produced in sugar or starch crops such as corn or sugarcane. Cellulosic biomass, derived from non-food sources, such as trees and grasses, is also being developed as a feedstock for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Bioethanol is widely used in the USA and in Brazil. Current plant design does not provide for converting the lignin portion of plant raw materials to fuel components by fermentation.

Biodiesel is made from vegetable oils and animal fats. Biodiesel can be used as a fuel for vehicles in its pure form, but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles. Biodiesel is produced from oils or fats using transesterification and is the most common biofuel in Europe.

In2010, worldwide biofuel production reached105 billion liters (28 billion gallons US), up17% from2009, and biofuels provided2.7% of the world's fuels for road transport, a contribution largely made up of ethanol and biodiesel.[citation needed] Global ethanol fuel production reached86 billion liters (23 billion gallons US) in2010, with the United States and Brazil as the world's top producers, accounting together for90% of global production. The world's largest biodiesel producer is the European Union, accounting for53% of all biodiesel production in2010. As of2011, mandates for blending biofuels exist in31 countries at the national level and in29 states or provinces. The International Energy Agency has a goal for biofuels to meet more than a quarter of world demand for transportation fuels by2050 to reduce dependence on petroleum and coal.

In an effort to save money on fuel and reduce its carbon footprint, the city's school district is converting all of its1,700 buses to run on a special engine that runs on both biodiesel and recycled vegetable oil donated by local restaurants. In2009, the first bus, the Fryer Flyer, took to the road. Officials expect to save $400,000 each year by running its entire bus fleet on the biofuel [source: NPR].

For years, politicians, journalists and scientists have touted biofuels -- fuels made from plants -- as a way to decrease the world's consumption of fossil fuels, especially oil. These so-called "energy crops" include wheat, corn, soybeans and sugarcane [source: Walker]. Biofuels burn cleaner than fossil fuels, releasing fewer pollutants and greenhouse gases, such as carbon dioxide, into the atmosphere. They are sustainable, and energy companies often mix biofuels with gasoline. In other words, unlike oil, coal or natural gas, biofuels won't run out.

Biofuels fall into two main categories: bioalcohol and biodiesel. To create bioalcohol, such as ethanol, engineers use yeast and bacteria to break down the starch in corn and other plants. To create biodiesel, refineries use the oil already found in crops such as soybeans [source: Thomas]. These vegetable oils are treated with alcohol and turned into biodiesel.

There are, however, some drawbacks to these miracle fuels. Among other things, some energy crops compete with food crops for land, creating problems like higher food prices and deforestation. In addition, the costs of converting some energy crops, as well as retrofitting cars and power plants to run on biofuel, can be pricey [source: Brune]. Find out what else there is to consider about the top10 biofuel crops.