Sugar Cane

Sugarcane and its by-products

By Dr Ali Muhammad Khushk & Ashfaq Ahmed Pathan

Sugarcane today is considered as one of the best converters of solar energy into biomass and sugar. It is a rich source of food (sucrose, jaggery and syrup), fibre (cellulose), fodder (green leaves and tops of cane plant, bagasse, and molasses and to some extent press mud), fuel and chemical. The main by-products are bagasse, molasses and press mud.

The other products and their by-products of less commercial value are green leaves and tops, trash, boiler ash and effluent generated by sugar industry and distillery.

Many countries have thought of diversification and utilization of it’s by- products. In the case where economies entirely depend on sugar export earnings any fall in international rates shatter their economies. They find it wise to diversify the activities of this sector by setting up industries based on by-products.

Though many products can be made, production of few is financially viable.

Bagasse based industries: Bagasse is a fibrous residue left over after the sugarcane is crushed. The fibre content of bagasse (cellulose) is used in cellulose industries like the pulp, paper, particle boards, cattle-feed etc. This is valued as an important by-product and efforts are under way to save as much as possible to produce the value-added products.

Baggasse is traditionally used as captive fuel in sugar factory boiler for raising steam required for the generation of power and driving the prime movers.

In recent years, the technology for making different products such as papers, boards and chemicals are developed and many countries have introduced energy conservation measures to save as much as possible, even after using it as captive fuel. For setting up commercial plants, it should either be surplus or saved.

It is possible to pool the surplus from a number of factories for supporting a bagasse-based industry. Though the price of all grades of paper is very high at present, but still such plants are financially viable.

In the wake of a steep decline in wood supplies and the need to conserve forest resources, the country has set up bagasse-based particle board and fibre-board plants with and without decorated laminations to replace wood-based boards. Such boards are used for making office racks, cupboards, table tops, partition walls, and ceiling etc.

Production of cattle-feed is picking up in the Caribbean countries and Latin America. As the digestibility of bagasse by the animals is very low due to its lignin content, these countries have set up pre-hydrolysis treatment on commercial scale.

These plants pre-digest bagasse and admix it with usual ingredients of cattle feeds (like corn, oil-cakes, grain, millets, urea etc.,) and also add molasses as a binding agent to palletize this mixture for packing in the polythene bags and transporting it to dairy farms and owners of cattle.

Such type of technology is planned to be developed in future in the country.

Molasses-based industries: Molasses is the final mother liquor leftover after the crystallization of sugar. It is sent out of the factory as a waste product.

However, molasses contains about 30-35 per cent sugar and 15-20 per cent reducing sugars. Thus, the total sugar content of molasses is 45-55 per cent. It is by virtue of this total content that molasses is a valuable raw material for the production of many value-added products.

The main products that can be produced from it on commercial scale are ethyl alcohol, citric acid, lactic acid, cattle feed, oxalic acid, bakers yeast, mono sodium glutamate, torula yeast, lysine, acetone-butanol-alcohol.

In addition to this, many alcohol-based chemicals like acetic acid, acetic anhydride, acetone, ethyl acetate, ethyl benzene, styrene, poly-styrene, poly-ethylene and synthetic rubber are also produced using cane molasses.

Ethyl alcohol is used for potable purposes, as well as feed stocks for many alcohol-based chemicals. The production of ethyl alcohol by fermentation of molasses is the most commercially successful process. The alcohol obtained by this process is also more suitable for use as potable spirit. In this connection, work may be done in the country on commercial scale.

The production of citric acid from commercial sugar is a simple process but commercial sugar is very expensive and, therefore, many firms prefer to manufacture citric acid from the molasses.

For the manufacture of citric acid from molasses the UK has developed a process for submerged fermentation of cane molasses into citric acid. Citric acid is used in the manufacture of jams, jellies, fruit juice, confectionery and other food products.

Based on this phenomenon a plant may be installed in the country to meet the citric acid demand, as the cost of production of citric acid based on cane molasses would be the lowest when manufactured here.

Molasses are used by different cattle-feed manufacturers. In the US as much as four million tons is used in cattle feeds. There is a need to increase the molasses in cattle feed by developing technology for producing urea-molasses blocks (animal chocolates).

Molasses is the main raw material for the production of different types of yeast, including bakers yeast by fermentation.

Bakers yeast is mainly used in the manufacture of bread, but it is also used for fermentation of molasses into ethyl alcohol. There is demand for bakers? yeast and improved strains of distillers yeast and hence, there is a scope for setting up such few units.

In Nigeria, polishes are made from cane wax, paraffin wax, bees wax. The oil from sugarcane wax is used in special varnishes. Lipid or soft wax fraction of sugarcane wax is also used to develop grease. Cane wax emulsion is used for preservation of fruits, vegetables and cheese.

Oil from sugarcane wax is used for protection against corrosion, and crude sugarcane wax is used directly for the manufacture of carbon paper. It is also used in improving the low melting/release properties of toners used in multicolour photographic copiers and printers.

For this, in the core material 0.5 to 2 per cent of sugarcane wax (melting point: 60oC) is used. All the components of wax such as hard wax, oil and resin find their use as a plasticizer in tyre industry.

It was reported by Sung-Wu and Wen-Che, 1981 that the wax scrapped off from cane stalks and extracted in petroleum ether in the concentration of 0.1 to 1 mg/l in the nutrient agar-agar stimulated the growth of rice seedlings.

There are many industrial uses of sugarcane refined wax such as water proofing emulsion for particle board and textile treatment, hot melting glues, removers of a casting from fibreglass moulds and precision casting.

The oil fraction of sugarcane wax is used for making poultry feed and anti-foaming agents in extinguishing powders. The introduction of new and synthetic sweeteners from corn and other starchy crops has also affected the economic viability of the sugar industry. It is realized that more avenues to earn profits are to be established through proper and fuller utilization of sugar crops.

It is necessary that each mill unit be converted into an integrated complex to produce sugar, alcohol, paper and a host of value-added downstream products.

The country needs to introduce constructive and meaningful changes in the industry. It has become imperative and urgent to prepare a plan to explore sugarcane as a food-feed-fuel-fibre-fodder-fertilizer crop, a multiple product commodity, in service to all future generations.

As far as the bagasse-based industries are concerned there is a tremendous scope to set up plants to produce market pulp, newsprint, writing and printing papers, particle board, medium density fibreboards, cattle-feed, and chemicals like furfural etc., as there is a good demand for all these products in the country itself. The country has 27 operating sugar factories.

As far as the molasses-based industries are concerned, the ideal solution would be set up distilleries to produce industrial alcohol, extra neutral alcohol and potable spirits. Industrial alcohol can be used as the feedstock for producing many value-added products.

The molasses-based products can compete in the international market with the products produced in other countries, due to the fact, that the price of molasses here is the lowest.