Weeding out a menace

the Kerala government has drawn up an ambitious plan to use the menacing water hyacinth to manufacture cellulase -- an industrially important enzyme. The Kerala Bureau of Industrial Promotion (k-bip), in collaboration with the Union government's department of science and technology and Nagpur-based National Environmental Engineering Research Institute (neeri), plans to set up a demonstration plant that will utilise 4,000 kilogrammes of water hyacinth every day.

The development is significant, as India is spending huge sums of money to import cellulase. The enzyme is used for numerous industrial applications, such as breaking down cellulose/insoluble materials of fruit pulp, improving the quality (smoothness) of cotton textiles and increasing the tensile strength of paper and pulp. The animal feed industry uses it to convert fibres in waste sludge into sugars, and 'clarify' the sludge to improve the efficiency of anaerobic wastewater treatment. Currently, the world market for cellulase is estimated to be us $500 million.

Many countries like the us and Germany use expensive biotech means to produce cellulase. The enzyme, which breaks down cellulose (the primary plant material), is found in all plants. But only a few like the water hyacinth contain amounts sufficient for commercial exploitation.

Apart from providing cheap raw material, the cellulase-extracting technique can help eradicate an ecoproblem -- many lakes, ponds and rivers of the tropical countries are beset by the fast-proliferating weed. A single plant can produce 3,000 of its kind within 50 days. The weed uses 13 times more water than an ordinary aquatic plant to grow. It removes oxygen from the water, thereby increasing its acidity. It also impacts biodiversity by displacing many aquatic grasses. It has disrupted drinking water supply, hydropower generation and fishing activities in many areas. Kerala is spending crores of rupees every year to remove the weed, as it has clogged inland waterways used for transportation.
The process Scientists of neeri perfected the technology to produce cellulase way back in 1996. Their process is simple. The stem and leaves are fermented and converted into pulp. Once it is semi-dried, the pulp is passed through an oven and subsequently mixed with water to make a slurry, which is inoculated with the pores of the fungus Trichoderma reesei. The slurry is subsequently kept in controlled conditions for 10 days. Thereafter, cellulase is precipitated and purified using chemicals like acetone and calcium chloride. The roots of the weed are also used to produce vermicompost or to generate electricity through biomass gassification.

The demonstration plant, which is expected to get clearance soon, will be set up at Akkulam, a suburb of Thiruvananthapuram city. According to Ajith Kumar, a k-bip official, Akkulam was chosen because the weed covers 95 per cent of the surface of its Veli-Akkulam freshwater lake. Even without regeneration, raw material will be available for five to seven years.

The k-bip officials have worked out the capital cost of the plant to be Rs 13 crore. "This may be less than anticipated, as the hyacinth will also be used for generating electricity," claims Kumar. The operational cost is estimated to be Rs 4.5 crore per year. As per experts, the benfits of the technology far outweigh its expenses.

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