The Choice of Biofuels to Mitigate Greenhouse Gas Emissions

Abstract

The tentatives to use biofuels can be traced back to the years around 1900 when Henry Ford and Rudolf Diesel used ethanol and vegetable oil in their Otto cycle and Diesel cycle engines, respectively. With the introduction of oil in the energy scenario as a very cheap option, the interest in biofuels dwindled down rapidly and the transport sector was fully dominated by gasoline and diesel. However, the idea did not die and biofuels came and went a few times; in the mid 1920s ethanol fuel was used in Brazil and in 1931 a Federal Law mandated the blending of 5% ethanol in all imported gasoline used in the country. Since then, several biofuels options have been produced and tentatively used in some countries: ethanol, methanol, higher alcohols, vegetable oils, fat acid methyl/ethyl esters, biogas and dimethyl ether (DME) just to mention the main ones. The driving forces behind the use of biofuels are many, but can be separated in four groups: environmental benefits (local and global), high oil prices, energy security and support to local agriculture. Different countries in different times were drawn by different motivations that changed in time in each case. Looking into the main biofuel programs today it can be seen that USA alcohol program was originally intended to mitigate local pollution problems due to vehicle tail pipe emissions but today is driven by the support to local agriculture, energy security and only very recently, with the Energy Independence and Security Act of 2007 (EISA 2007), it has shown some interest in global warming mitigation, with the introduction of minimum greenhouse gas (GHG) emission reduction limits for different alternative of biofuels (Renewable Fuel Standard – RFS2); ethanol dominates the first generation technologies (1G) with biodiesel playing a minor but important role. The Brazilian Alcohol Program launched in 1975 was aimed at reducing the oil imports (due to high oil prices and energy security), but also at improving the sugarcane industry conditions, badly hit by the low sugar prices and overproduction; after the decline in oil prices in the mid 1980s the focus became the reduction of local pollution in the large cities resulting from vehicle tail pipe emissions; more recently, in 2004,the National Biodiesel Production and Use Program was initiated in Brazil with a strong focus on social inclusion and support to small producers, but also