Cassava roots can be used as the feedstock for bioethanol production. During the harvest season, roots are plenty and cheap. However, roots contain very high moisture contents and

are prone to spoilage over the storage time. Mostly, roots are transformed readily to a dried form called cassava chips nearby the plantation areas. To produce chips, harvested roots are cut into pieces manually or by small machine and then sun-dried. The dried chips contain low moisture contents (< 14%), are less bulky, less costly for transportation and can be stored for a year in the warehouse. In addition, dried cassava chips have comparable characteristics as corn grains and can be processed by adopting conversion technology of corn grains. Cares must be taken when storing dried chips as heat can be generated and accumulated inside the heap. Therefore, the warehouse should have a good air ventilation system to prevent overheating and burning of chips. When used, the chips have to be transferred, using the rule of first-in and first-out, to the process line. Dusts are produced, resulting in starch loss as well as severe air pollution. The major concern of using chips is soil and sand contamination, being introduced from roots and during drying on the floor. Sand and soil can cause machine corrosion and result in shorter machine shelf life. They have to be removed in the production process. In Thailand where chips are used for many applications including animal feed and bioethanol production, farmers are encouraged to produce a premium quality of chips that meets with the standard regulation announced by Ministry of Commerce (Table 5).

When cassava is used for bioethanol production, different forms including fresh roots, chips and starch can be used. Table 6 summarizes advantages and disadvantages of using different forms of cassava feedstock. The factory has to make and manage an effective feedstock plan as the feedstock cost can account upto 70%of total ethanol production cost. Types of feedstock used for bioethanol plants depend on many concerns including plant production capacity, plant location, nearby cassava growing areas, amount of feedstock available and processing technology. Ethanol plants that are not close to cassava farms prefer to use dried chips to reduce costs of transportation and storage, while those locating next to cassava fields can use chips and roots. When using both feedstocks, the plants have to somewhat adjust the process in particular feedstock preparation.