Sugar production

Sugar is mainly produced from beet (in Europe) or cane (in warmer climates). In the EC, sugar beet production generates more than 100 million tonnes per year of solid waste and around 0.5 m3 of wastewater per tonne of raw material; these wastes are generally spread on land. For every tonne of sugar beet, 140 kg of sugar is extracted, resulting in 86% waste. Beets are first flumed by water and separated from leaves, weeds, beet tails and soil. This represents around 100 kg of waste for a tonne of sugar beet and is used for animal feed or composting. Beets are then sliced and pressed, leading to sugar beet pulp (50 kg). This pulp can be dried and used as animal feed or as a raw material (rich in cellulose) for paper production (see Section 16.4.2). Pulp contains and can provide foodstuffs such as protein, prebiotic, cellulose, pectin or hemicellulose. Ferulic acid can also be extracted from pulp and bioconverted to vanillin (Thibault et al., 1998) (see Section 16.5.3). The juice obtained by pressing is purified by adding milk of lime and carbon dioxide. This process step generates 60 kg of carbona-tion lime that can be used as a soil improver or as absorbent material. Finally the crystallisation step separates sugar from molasses (38 kg). Molasses are used for animal feed, pharmaceuticals extraction (betaine, vitamins, etc.) or as a source of carbon in fermentation processes (e.g. production of ethanol and citric acid). The rest of the waste is the water initially contained in the beets. In the case of sugar cane, processing produces large quantities of bagasse, commonly used as fuel or as a source of arabinoxylans (Schieber et al., 2001).

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