[Problem] To carry out
processing of leaves, fallen leaves, stems, and bulbs of
useful plants such as rice husks and
bagasse, which is the residue from
processing sugarcane, into food or beverage, by using a commonly used technique that can be expected to be widespread. For ginger, turmeric,
Allium chinense, onion, garlic, and the like, only the bulbs thereof are used, but leaves and stems thereof are mostly not used. [Solution] A useful food / beverage product can be produced at low cost through extraction of components by directly parboiling, or by
drying, pulverizing,
roasting, and parboiling, as a
raw material, waste or unused parts including rice husks,
bagasse, which is the residue of sugarcane, dead leaves of guava or dead leaves of pine, unused parts (leaves, stems, skins, seeds, and the like) of ginger and citrus, and unused parts such as the
skin and seeds of fruits, which are all discarded in a large amount. The useful food / beverage product is also suitable for providing assistance to people who are unemployed or in need recently. Through the effective use of waste, the present invention makes a contribution in industrial development by increasing agricultural income and reducing the enormous capital, labor cost, and the like for disposal of the waste.