Additional information is available at the end of the chapter http://dx. doi. org/10.5772/53827

1. Introduction

1.1. Current sources of biofuels

The United States, as well as numerous other countries throughout the world, is seeing a rapid rise in the amount of power and fuel required to maintain the current and future life­styles of its citizens. With the rapid increase in global consumerism and travel seen over the recent decades due to improvements in technology and the increase in international interac­tions, the demand for fuel is rapidly growing, as can be seen in Figure 1. Due to the world­wide demand for fuel, which currently is primarily fossil-derived, supplies are being strained and costs are rapidly rising. In order to satiate this rapid increase in demand and stem the shrinking supply, new alternative sources of fuel must be brought to the market that can be used to replace standard petroleum based fuels.

Currently, there are several sources of alternative fuels that can be used to replace or supple­ment traditional petroleum based fuels. Some of these sources include alternative fossil-de­rived sources such as coal, natural gas, and hydrogen derived from hydrocracking, while other sources come from more renewable sources such as biomass. Biomass has several ad­vantages when it comes to fuels in that there are numerous sources such as terrestrially grown starch based or cellulosic material, waste derived material, or aquatic and marine based organisms, each of which has unique components and characteristics useful for fuel production.

Due to the structural variability of the various types of biomass available, a wide range of technologies can be used to convert the organic molecules into a useable form of fuel. As food substrates (such as carbon dioxide in autotrophic organisms or sugars in heterotrophic organisms) are metabolized, a range of cellular components are assembled to perform nu­merous duties to keep organisms alive and reproducing. Starches and celluloses are assem­bled from carbohydrates to provide rigid structural support in many woody biomasses as

well as acting as a sugar storage method for quick conversion to a food source in times of famine. Proteins and amino acids are the building blocks of DNA structures and additional biomass. Lipids provide a highly energy dense storage system while also serving as a trans­port mechanism for several nutrients vital to metabolic activity. However, when broken down to the most basic levels, these organic compounds all contain energy which can be ex­tracted through several methods. Table 1 shows a breakdown of some common algal bio­mass cellular components.

Sources of biofuel currently being produced range in production rate from the laboratory scale through full scale implementation. Technologies to break down starches and cellulosic materials into sugars for subsequent conversion to bioalcohols has been extensively devel­oped and scaled to produce billions of gallons per year to add into petroleum derived gaso­line. Other structural components such as lipids have a high energy content to them and have characteristics that closely mimic petroleum diesel and kerosene, and thus, only re­quire simple chemical reaction (i. e., transesterification) for use as a biofuel, and have been developed up to a quasi-large scale of volumetric output that can be seen in some regional market places, as well as in home production for personal use.