Most of the fuel ethanol produced in the world is currently sourced from starchy biomass or sucrose (molasses or cane juice), but the technology for ethanol pro­duction from nonfood plant sources is being developed rapidly so that large-scale production will be a reality in the coming years (Cardona Alzate, 2008; Lin, 2006). Moreover, when using nonfood raw materials, food security is not affected by this industry and improves ethanol’s social and environmental impacts. The negatives of lignocellulosic biomass are the access (including transport costs), pretreatment cost for breaking its complex structure, and the production of nonde­sired products that can inhibit the enzymes and microorganism activities during hydrolysis and fermentation steps.

The importance of a particular type of biomass depends on the chemical and physical properties of the large molecules from which it is made. The chemical structure and major organic components in biomass are important in the devel­opment of processes for producing fuel and chemicals derived from it. Biomass contains varying amounts of cellulose, hemicellulose, and lignin, and a small amount of extractive (Bridgewater, 1999).

Worldwide generation of lignocellulosic residues is estimated to be more than about 4 billion tons each year. However, there are concerns about the importance of harvest residues in maintaining soil quality. Adding harvest residues to soils is very important in the provision of plant nutrients and for the water binding capacity of soils. Low levels of soil organic carbon contribute much to poor agricultural yields in large parts of sub-Saharan Africa and the tropical and subtropical areas of Asia. If this practice is not controlled, use for bioethanol of crop residues will exacerbate soil degradation and aggravate food insecurity (Lal, 2008; Reijnders, 2008).

Kim and Dale (2004) analyzed the size of the bioethanol feedstock resource at global and regional levels taking into consideration wasted crops (crops lost in distribution) and lignocellulosic biomass (crop residues and sugar cane bagasse). These authors estimate that the global potential ethanol production from these feedstocks accounts for 491 gallons/year, which is 16 times higher than current ethanol production and which could replace 32% of the global gasoline consump­tion. Rice straw is the feedstock that potentially could produce the largest amounts of ethanol, followed by wheat straw. In general, the total volume of energy from agricultural residues is estimated at 12 EJ (ExaJoule = 1018 J), as shown in Hall et al. (1993).