TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: The method involves adding water and yeast to sweet potato residue, sealing and fermenting the raw material, stirring the raw material once a day, stopping stirring after 5 days, and distilling the obtained product after fermenting for 8-12 days, where fermentation of the raw material reduces the process of boiling the raw material, that can save consumed energy source for boiling. The method involves establishing sweet potato primary processing station, maintaining radiation radius within 10 km, such that the sweet potato with low additional value not suitable for being carried is not carried for a long distance, where the products of sweet potato is starch, potato residue and sweet potato vine powder, directly purchasing the potato residue from the existing potato processing factories, developing crude product ethanol producing station, arousing pig farm and allowing farmers to establish mash gas tanks (with the water level for culturing fish), allowing the scale of the mash gas tank to adapt to that of the pig farm to discharge pig excrement into the mash gas tank, providing mobile fermenting and distilling device, assigning technicians to guide the feeders to prepare fuel ethanol from sweet potato residue by fermentation, providing fermenting tank and distilling device, providing the potato residue and grain stillage, and establishing small-scale bean vermicelli and fish noodle processing workshop at the first sweet potato primary processing station to improve the additional value of starch, or establishing small-scale pig farm at the sweet potato primary processing station with water level to form an ecological circulating system, where the raw material starch and crude product ethanol are of high additional value and can be transported for a long distance, such that the radiation radius is more than 100 km, and the products are bean vermicelli, fish noodle, fuel ethanol, and pig feed containing potato residue and grain stillage.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Device: The distillation device using sweet potato residue to prepare fuel ethanol, comprises a heating and distilling system and a drying and storing chamber. The heating and distilling system comprises a double-heat source device including gas fuel oven, gas fuel heating chamber, solid fuel oven, solid fuel heating chamber, liquor brewing chamber, air condenser and rectifying column filled with stuffing. The gas fuel heating chamber is connected with the solid fuel heating chamber through a pipeline. A steam outlet at top portion of the liquor brewing chamber is connected to an air inlet at bottom of the rectifying column through a liquor steam tube. An air outlet at top end of the rectifying column is connected to an air inlet tube of a condensing tube. An outlet of the condensing tube is connected to a reflux ratio controller. A U-shaped tube is installed at middle portion of the branched pipe that is guided out from side face of reflux ratio controller. A spraying head is mounted at top end of the branched pipe stretching into the rectifying column. The bottom of the reflux ratio controller is connected to an ethanol outlet valve. The smoke discharging pipeline of the solid fuel oven, sweet potato residue supporting rack and exhaust fan are provided in the drying and storing chamber built above the air condenser.