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Back  (Sugar Industry Sector)   April 2007, Issue Number 2

 

  • Farming of sugar cane (farm level activity)

  
 

Sugarcane holds a prominent position as a cash crop in sugar producing region and therefore most of the farmers cultivate it to make a profit. In this sector, most of the farmers and the labourers are involved in activities, which are directly or indirectly related with sugar production. Sugarcane-crushing season is for six months and during this period most of the people are employed in harvesting, loading and transportation activity.

 
 
Almost all sugar mills depend for their supplies of sugar cane on large number of independent farmers. If the yield per hectare is improved, the benefit goes to the growers while if the cane is rich enough in sugar content; it becomes profitable to the mills. Therefore cane growing and milling are essentially a joint enterprise where grower and miller are equally benefited.
  
 

Production of sugar & by-product utilization

The second level starts when the collected sugarcane is conveyed to the cane leveler where it is cut and chipped. The cut cane blanket is then fed to tandem of mill, wherein it is crushed and the juice is extracted.

The sugarcane needs to be processed as soon as possible to avoid the sugar losses. Typically, cane is processed within 24 hours after harvesting. The various steps in the manufacturing of sugar are as follows:


  • Extraction of Juice - The cane from the field is brought in bullock carts, tractors, trollies, trucks etc., which is then unloaded in the cane carrier by manual labour or mechanical unloader. It is then conveyed to the cane leveler where it is cut and chipped. The cut cane blanket is then fed to tandem of mill, wherein it is crushed and the juice is extracted

  • Clarification - The extracted juices are then heated to 60-65oC in juice heater and passed to a reaction tank where the liming and sulphitation takes place. This limed and sulphited juice is pumped back to a ‘clarifier’ after heating to 100oC which remains there for about 3 hrs. During this stage in the clarifier, the heavy insoluble impurities, mostly soil and mud are precipitated which is then pumped to a vacuum filter which removes the liquid portion from the mud, while the solid muddy portion is taken out of the company building. This waste is used as manure or can serve as raw material for the extraction of crude wax.

  • Boiling - The raw juice is now clarified and is called the clarified juice.  It is then passed through a set of evaporator which boils the excess water under vacuum concentrating it gradually, as it passes from one evaporator to another. Finally concentrated juice called the sugar syrup is sent to the pan floor wherein the final crystallization takes place, under vacuum. The evaporation is carried out under vacuum.
  • Crystallization - A viscous solid mass consisting of sugar crystals and mother liquor is dropped in crystallizer and it then passes through the pug mills to centrifugals machines. Due to very high gravity factor, the viscous mother liquor passes through the opening in the liner and the sugar is retained on the screen and the sugar is then dropped into the hopper.



  • Grading & Packaging: -The sugar is then passed on to a unit called grader, which grades the sugar in different grades and in different sizes as per the Indian sugar standards. The sugar is bagged in the pre-stamped empty gunny bags, weighed; the grades and number marked on the bags and these bags are stored in godowns and are finally sold. The transportation of sugar from mill to market is mostly carried out by road. Though the Indian sugar industry is more concentrated in rural parts of India but it is well connected with most of the metropolitan cities of the country.




  • By- product utilization:-The waste and by-product generated from the production of sugar are sent to the by-product based industry. The fibrous cane material after the extraction of juice, called bagasse goes to the boiler, wherein the same is burnt producing steam and electricity that powers the mill to process sugar from cane juice and alcohol in distillery industry. The excess bagasse is baled and stored or can be sold to the paper industry as a substitute raw material to be used for paper production.

Molasses, generated from sugar manufacturing finds its way to the distillery industry where it is used as a raw material to produce various industrial chemicals, alcohol, power biofuels. Alcohol is an important basic feed stock for manufacture of various chemicals. It is a good substitute for petrochemicals and petrol based chemicals in India.Waste materials coming out of the sugar and distillery industry are press mud and spent wash. Press mud is used as a filler material for bio-composting and the compost manure is sold to the farmers.



Anaerobic digester is used to process left-over effluent i.e. spent wash and to clean the wastewater which makes up 80% of the cane stalk to produce biogas, food grade CO2, and fertilizer. Cleaned water is recycled for on-site use, sent back to the river or used to irrigate the cane-farms. 
Like wise the network revolves around the sugarcane farm and plays the important role in the rural economy of the area. Thus, if effectively managed from the environmental point of view, sugar network is a closed loop network, where all the waste from the production process is utilised for the byproduct manufacturing.

 
     
     
 
 
   
 
 
 

 
 

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