Natural gas and other alternative fuels for transportation purposes

Natural gas has been used as fuel for transportation for decades and, currently, about half a million vehicles of different types are running either on compressed natural gas (CNG) or on liquefied natural gas (LNG) in a number of countries, including Italy, New Zealand, the U.S.A., Australia, Iran and France. The country with the most developed program on utilization of natural gas as a transportation fuel is Italy, where almost 300,000 vehicles are running on CNG. Several other countries such as Brazil, Egypt, Canada, Bangladesh and the Soviet Union are implementing programs to use natural gas for domestic transportation needs. Natural gas is composed essentially of methane, which can be obtained also through anaerobic fermentation of different organic products yielding biogas (60% methane). The role of methane as a fuel has shown increasing importance due to the growth in digester construction all over the world, and especially in developing countries. Natural gas can also be used as raw material for the production of liquid fuels suitable for transportation purpose such as methanol, ammonia, gasoline, diesel oils, methyl esters of vegetable oils, and MTBE, a high-octane component of gasoline. In addition, natural gas liquids (propane/butane) can also be used as automotive fuels. This paper covers the technical-economic aspects of natural gas and methanol as fuels for transportation and presents a summary of worldwide experience with emphasis on the existing experience in a developing country such as Brazil, including its commercial large-scale experience with ethanol fuels.