Emad A. Shalaby

Additional information is available at the end of the chapter http://dx. doi. org/10.5772/51943

1. Introduction

Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Bio­fuels include fuels derived from biomass conversion (Figure 1, JICA, Okinawa, Japan), as well as solid biomass, liquid fuels and various biogases. Although fossil fuels have their origin in ancient carbon fixation, they are not considered biofuels by the generally accept­ed definition because they contain carbon that has been "out" of the carbon cycle for a very long time. Biofuels are gaining increased public and scientific attention, driven by factors such as oil price hikes, the need for increased energy security, concern over green­house gas emissions from fossil fuels, and support from government subsidies. Biofuel is considered carbon neutral, as the biomass absorbs roughly the same amount of carbon dioxide during growth, as when burnt. The chemical composition of different kinds of biomass was shown in Table 1.

Biodiesel as one from important biofuel types 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.

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.

Table 1. Average properties of biomass

In 2010 worldwide biofuel production reached 105 billion liters (28 billion gallons US), up 17% from 2009, and biofuels provided 2.7% of the world’s fuels for road transport, a contri­bution largely made up of ethanol and biodiesel. Global ethanol fuel production reached 86 billion liters (23 billion gallons US) in 2010, with the United States and Brazil as the world’s top producers, accounting together for 90% of global production. The world’s largest biodie­sel producer is the European Union, accounting for 53% of all biodiesel production in 2010. As of 2011, mandates for blending biofuels exist in 31 countries at the national level and in 29 states/provinces. According to the International Energy Agency, biofuels have the poten­tial to meet more than a quarter of world demand for transportation fuels by 2050.