Starch materials are also potential resources for the bio­ethanol production. Starch molecules are polysaccharides made up of long chains of glucose units covalently linked. Before the fermentation process, the starchy materials are broken into simple glucose molecules after which the sim­ple sugar units are easily fermented by the microbes. Examples of starchy materials used for bioethanol produc­tion include cereal grains, potato, sweet potato, beans, cas­sava, maize, wheat and cereal grains. As these materials are also too expensive and included in the human food

chain, wastes are collected from places where they are crushed into flour or from industries where they are used for various products (Kahn et al., 2011).

Table 3.2 reports the use of starchy residues in ethanol production. As starch is an important component of the food chain, it is expected that the wastes of the process­ing be more used for ethylic fermentation (Moukamnerd et al., 2010). Another important point that can be observed is the predominant use of simultaneous saccharification and fermentation (SSF) in the use of starch for energy generation and in both cases hydroly­sis was achieved by enzymes (Hong and Yoon, 2011; Moukamnerd et al., 2010). Hashem and Darwish (2010) reported the use of potato starch residue stream pro­duced during chips manufacture and the authors have used separate hydrolysis and fermentation (SHF) and a very low acid hydrolysis of the starch to reduce the cost associated with this necessary treatment.