The food processing industry is dogged by the problem of disposing wastewater heavy in organic matter. Anaerobic digestion using a series of ponds to hold the water over a period of time is inefficient and odorous. Current innovations using starch waste in anaerobic digestion and fermentation technologies have made wastewater treatment more effective. An added advantage is the additional energy in the form of biogas and the byproduct of the process, the effluent slurry, is a natural fertilizer. Oil mills, alcohol distilleries, flour mills, fruit and vegetable canning units, starch extraction plants and paper mills are potential beneficiaries of these technologies which translate into considerable savings on energy bills and safe disposal of wastewater.
The waste water generated during the extraction of starch from cassava roots in Brazil is put through a 2 stage anaerobic bio-digester to produce biogas. The biogas produced is used
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To supply the required heat for the generation of steam to process the cassava roots.
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To produce the heat to dry the starch extracted.
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To generate electricity to operate the plant, thereby contributing to lower energy bills.
The technology works equally effectively in tapioca starch production plants in Thailand and sugarcane bagasse from sugar factories in India.
For smaller units like canning centers or flour mills, compact biogas systems using waste starch such as worm infested grains unfit for human or animal consumption, flood damaged cereal crops, banana rhizomes, non-edible seeds, rotten fruit and spoilt fruit juice or oil-cake are practical. 2 lbs of waste starch slurry delivers the same amount of methane as 80 lbs of cattle dung. Moreover, the conversion from starch to gas takes place within 6-8 hours as opposed to 40 days for the cattle-dung-based units. Higher biogas yields have been reported from oilcake feedstock users. Combination feedstock that combines animal dung and starch powder slurry has been effective in improving biogas generation in conventional cattle-dung-based biogas plants, in addition to reducing production time dramatically.
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