Bioenergy is regarded as one of the key options to mitigate greenhouse gas (GHG) emissions and to substitute fossil fuels [1,2]. Although there are many renewable energy technologies emerging for large-scale electricity production with low or no GHG emissions, the transport sector is almost entirely based on fossil fuels, and has fewer alternatives.
Transportation represents some 27% of the world's secondary energy consumption (21% of primary), and is almost exclusively fueled by petroleum oil [3,4]. Biofuels can play an important role in addressing both the GHG emissions of transport and the dependency on petroleum oil.
A few main routes can be distinguished to produce biofuels: extraction of vegetable oils, fermentation of sugars to alcohol, gasification and chemical synthesis, and direct liquefaction. These can lead to a variety of fuels: methanol, ethanol, hydrogen, synthetic diesel, biodiesel, and bio-oil, all with very different properties, as described in .
With the exception of sugarcane ethanol, the traditional biofuels have a number of severe disadvantages that are related to the feedstock. The current costs of rapeseed biodiesel and ethanol from cereals or beets are much higher than the costs of gasoline and diesel, and substantial subsidies are needed to make them competitive. These high costs are a result of the low net energy yield of most annual crops (100-200 GJ/ha yr in the long term ), the high quality agricultural land required, and the intensive management. The lower productivity per hectare and high fertilizer requirement also limit the well-to-wheel reduction of fossil energy use, which limit the environmental benefits [5,6]. The net energy of perennial crops (220-550 GJ/ha yr), grasses (220-260 GJ/ha yr), and sugar cane (400500 GJ/ha yr) is considerably higher, and Brazil has been a world leader in promoting biofuels for 30 years under its Proálcool program.
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Your Alternative Fuel Solution for Saving Money, Reducing Oil Dependency, and Helping the Planet. Ethanol is an alternative to gasoline. The use of ethanol has been demonstrated to reduce greenhouse emissions slightly as compared to gasoline. Through this ebook, you are going to learn what you will need to know why choosing an alternative fuel may benefit you and your future.