2.8.1 General scope of sugar and starch crops

Starch and sugar can be fermented to biofuel such as ethanol, but fibrous saccharides such as cellulose and hemicellulose in the residual waste cannot easily be hydrolized to fermentable carbohydrates such as glucose.

Primary starch crops are rice (Oryza sativa and Oryza glaberrima), potato (Solanum tuberosum L.), sweet potato (Ipomoea batatas (L.) Lam.), corn (maize; Zea mays L.), wheat (Triticum L.), barley (Hordeum spontaneum C. Koch (wild-type two-rowed barley); H. vulgare L. (six-rowed barley); H. distichum L. (two-rowed barley)), cassava (bitter cassava, cassava, manioc, manihot, sweet-potato tree, tapioca, tapioca plant, yuca; Manihot esculenta Crantz),
and sago palm (Metroxylon sagu Rottb.). As primary sugar crops, sugar cane (Saccharum officinarum L.) and sugar beet (Beta vulgaris var. altissima) are widely known.

Yields of three primary cereals (corn, wheat, and rice) are increasing up to 725, 6.33, and

6.6 million tons, respectively, with a sum of 1,963 million tons, which is about 86% of total cereal production of 22.74 million tons (2004), being realized by novel cultivars and development of cultivation technology (Fig. 2.8.1). However, due to limitations of the conventional technologies, further extension of cultivation area will require novel technology such as genetic modification to cold-, drought-, or halo-resistant cultivars. Production of sugar cane has been increasing up to 1,332 million tons (2004), while that of sugar beet has been around 200 million tons (Fig. 2.8.2). Total production of sugar and starch crops (4,572 million tons (2004)) contributes to the high nutritional intake (2,808 kcal/capita/day (2003)) for 6,370 million population in the world (2004). However, around 800 million people, mainly in population explosion area of Asia and Africa, are still suffering from starvation. Therefore, it should be morally criticized if the crops would be further used as “non-food” energy crops. We have to increase the amount of the foodstuffs by increasing the cultivation area and crop yields with novel technology such as genetic modification, while promoting cultivation of energy crops and developing new technology to convert crop wastes to biofuel.

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(ref. FAOSTAT: http://www. faostat. fao. org/default. aspx)