Human activity requires considerable amounts of energy distributed more or less evenly between three types of activity: industrial, residential and transportation. This is a typical 20th century development that resulted from the growth of road transportation. Until the end of the 19th century land transportation was based essentially on the use of horses and represented less than 10% of all energy consumption. Biomass in the form of hay for feeding horses has been the main ‘fuel’ sustaining transportation.

The development of internal combustion engines by Diesel and Otto, approximately 100 years ago was based on the use of biofuels, but with discovery of abundant petroleum reserves there was a dramatic shift in fuels. Transportation now accounts for more than 30% of all energy used in the world and consumes around 83 million barrels of oil per day.

The 20th century saw an explosion in the use of automobiles for personal use and trucks for the transportation of goods. There are already more than 600 million automobiles in the world and the number is increasing steadily since the use of the automobile is not only very convenient, but it is also intimately associated with our cultural values. In the United States there are almost 800 automobiles per 1000 people; in China and India this number is 10 times less but quantities are increasing rapidly.

Unfortunately this is a situation that cannot last for very long because the fuels used for present modes of transportation are almost exclusively from petroleum, of which remaining reserves are being depleted rapidly. In addition to that, such fuels are the main source of environmental problems ranging from bad air quality in large cities to regional pollution and the increase of the concentration of greenhouse gases in the atmosphere.

It is therefore urgent to find fuels that could replace petroleum products or develop other methods of propulsion if one wishes to preserve individual transportation.

Of the several technologies in development for that purpose only electrical motors and biofuels seem to be promising solutions. Electrical motors using batteries, where the energy is stored or produced by fuel cells, are making limited progress and in any case will require large additional amounts of electricity to be produced mainly from fossil fuels which are not renewable. One tends to forget

xxiv Foreword that an automobile usually requires 30 kilowatts of power which mean 18 billion kilowatts for an entire fleet. For comparison the total installed capacity for electricity generation in the world is around 4 billion kilowatts.

Biofuels are therefore the more promising option: they are renewable, contribute little to the production of greenhouse gases and do not have the impurities that petroleum derived fuels have. Biofuels already represent a small percentage of the transportation fuels in the world. The ‘automobile age’, which started with biofuels, seems to be returning to its origins.

The Handbook of biofuels production provides a comprehensive discussion of all the aspects of the problem ranging from the feedstocks and production chain to chemical and biochemical production as well as the thermal and thermo-chemical conversion process. Sustainability assessment and policies surrounding the issue are also discussed.

Professor Jose Goldemberg University of Sao Paulo Sao Paulo, Brazil