S. PINZI and M. P. DORADO, University of Cordoba, Spain

Abstract: This chapter presents the most frequent vegetable-based feedstocks to biodiesel and bioethanol production. The chapter focuses on first — and second-generation biofuels with special emphasis on low-cost feedstocks. Finally, raw materials for developing technologies, including anaerobic digestion to produce biogas, Fischer-Tropsch from biomass, pyrolysis and biological production of bio-hydrogen are discussed.

Key words: first-generation biofuels, second-generation biofuels, third-generation biofuels, low-cost biofuels, biomass.

4.1 Introduction

Main differences between generations of biofuels lie in both conversion technology and raw materials. First-generation biofuels are made using conventional chemical technology to convert mainly oilseeds and grains into biodiesel and bioalcohol, respectively. In many cases, same feedstocks could be used for animal or human feeding purposes, thus suffering criticism from organisations that point at biofuels as the leading factor of food price rises and even deforestation in the Amazon or Indonesia. Although arguments against these assumptions are exposed, second-generation biofuels are based on non-food crops (i. e. Miscanthus) and biomass residues (from crops and forests), thus providing a socially accepted alternative. However, conversion technologies to produce biohydrogen, biodimethyether (Bio-DME), Fischer-Tropsch (FT) diesel, etc., are still under development.

There is also a third-generation emerging consisting of biofuels from algae and even an incipient fourth-generation based on the conversion of biodiesel into gasoline or on the recycling of carbon dioxide back into gasoline. Some companies claim that they can produce economically-sounded petroleum from microorganisms having the ability to efficiently convert renewable feedstocks into hydrocarbon-based fuels (Du, Li, et al, 2008). Although there is a wide variety of feedstocks and biofuels, this chapter is mainly focused on the most frequent vegetable-origin feedstocks to biodiesel and bioethanol production.