Bagasse & Co-generation of Renewable Energy

 

Bagasse is the fibrous matter that remains after sugarcane or sorghum stalks are crushed to extract their juice and is a by product generated in the process of manufacture of sugar. It can either be sold or be captively consumed for generation of steam. It is currently used as a biofuel and in the manufacture of pulp and paper products and building materials. The bagasse produced in a sugar factory is however used for generation of steam which in turn is used as a fuel source and the surplus generation is exported to the power grids of state governments.

For each 10 tonnes of sugarcane crushed, a sugar factory produces nearly 3 tonnes of wet bagasse. Since bagasse is a by-product of the cane sugar industry, the quantity of production in a country is in line with the quantity of sugarcane produced.

Bagasse when burned in quantity produces sufficient heat energy to supply all the needs of a typical sugar mill, with enough energy to spare. To this end, a secondary use for this waste product is in cogeneration, the use of a fuel source to provide both heat energy, used in the mill and the electricity which is typically sold on to the consumer through power grids.

The power produced through co-generation substitutes the conventional thermal alternative and reduces greenhouse gas emissions. In India, interest in high-efficiency bagasse based cogeneration started in the 1980s when electricity supply started falling short of demand. High-efficiency bagasse cogeneration was perceived as an attractive technology both in terms of its potential to produce carbon neutral electricity as well as its economic benefits to the sugar sector. In the present scenario, where fossil fuel prices are shooting up and there is a shortage and non-availability of coal, co-generation appears to be a promising development. The thrust on distributed generation and increasing awareness for cutting greenhouse gas emissions increases the need for cogeneration. Also it helps in controlling pollution from fossil fuels.

India’s 527 working sugar mills crush around 240 million tonnes of cane per year and generate 80 million tones of wet bagasse (50% moisture), of which they consume around 70 million for meeting captive requirements of power and steam. Thus, electricity production through cogeneration in sugar mills in India is an important avenue for supplying low-cost, non-conventional power. Presently, India has around 206 cogeneration units with a cumulative installed exportable capacity of 3,123 MW (peak season). Besides, India has a potential of generating 500 MW of power through bagasse and with modernization of the new and existing sugar mills India has potential to generate surplus power across all sugar factories in India to the extent of 5000 MW in the time to come.

About Molasses

Molasses, meaning honey like, is a thick dark syrup that is a by-product of sugar refining through repeated crystallization of sugar syrup obtained by crushing sugar cane. Molasses is sold both for human consumption, to be used in baking and in the brewing of ale, as also for industrial use. In India Molasses is used mainly in manufacture of industrial/ potable alcohol, yeast and cattle feed. Alcohol in turn is used to produce ethanol, rectified spirit and various value added chemicals. Ethanol is consumed by chemical industry and is also used in blending with petroleum to produce Ethanol Blended Petroleum (EBP). The yield of molasses per ton of sugar cane crushed varies in the range of 4.5% and 5%. Molasses and industrial alcohol-based industries were decontrolled in 1993 and are now being controlled by respective state government policies. Nearly 90% of molasses produced is consumed by industrial alcohol manufacturers and remaining 10% for various other uses like potable liquor.

In India Ethanol, a type of industrial alcohol, is produced directly from Molasses. The Government offers subsidized loans to sugar mills for setting up an ethanol producing unit, covering 40% of the project cost thus encouraging higher Ethanol production. Since sugarcane production in India is cyclical, ethanol production also varies, thus not assuring the optimum supply levels needed to meet the demand at a given time. Lower sugar molasses availability and consequent higher molasses prices affect cost of production of ethanol, thereby disrupting ethanol supply for the blending programme at pre-negotiated fixed level. Increased consumption of Ethanol for these uses is expected to harden the prices of Ethanol and growth of this by-product of sugar in a healthy and profitable manner.

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