Modern transportation almost exclusively depends on fossil fuels, mainly petroleum-based fuels such as gasoline, jet fuel, diesel, liquefied petroleum gas, and natural gas. Of particular concern are the liquid fuels used in cars, airplanes, and trucks because of the combination of rising oil prices, exhaustion of crude oil reserves, energy insecurity, climate change, and environmental pollution. These concerns have spurred research and development interests in biofuels (ethanol, higher alcohols, biodiesel, biogas, and Fisher-Tropsh liquids) from a variety of biomass. The world is on the verge of an unparalleled increase in the production and use of biofuels for transportation. First generation biofuels, namely grain-based ethanol and vegetable-oil-based biodiesel, have faced difficulties due to competition with food supplies, life cycle and energy balance assessments, and costs. One of the main research directions in biofuels, therefore, is the production of fuels from non-food resources such as algal and lignocellulosic biomass. Such biofuels would provide a “greener” alternative to fossil fuel energy because they are renewable, carbon neutral, and available in one form or another throughout the world.
Energy is essential for economic and social development but also poses an environmental challenge. In comparison to fossil fuels, biofuels have the advantages of being renewable, nontoxic, and biodegradable and have a much lower risk of contaminating the environment. Generally, the raw materials that are exploited commercially to produce biofuel consist of edible fatty oils derived from rapeseed, soybean, palm, sunflower, and other plants. However, biofuel from edible oils is controversial due to the increase in global food prices, depletion of ecological resources, and intensive agricultural practices in crop cultivation. The second generation biomass production and utilization minimizes these concerns because second generation biofuels are derived from non-food feedstock, such as algae.