Water hyacinth, a devil in disguise

Have you ever noticed a green layer of dense plants on freshwater water bodies such as rivers,  ponds, lakes in cities where you live? These are the commonly occurring water hyacinth (Eichhornia crassipes), a fast growing aquatic plant often found in freshwater ecosystems that normally provides shelter and feeding grounds for a range of aquatic species.

However, under conditions where water bodies are polluted with a high nutrient load, these free floating and highly invasive aquatic plants can proliferate even more rapidly thus posing a risk to the natural habitat [1] of the freshwater ecosystem where it grows. High growth of water hyacinth leads to a gradual deterioration of the freshwater body.

Water hyacinth has been listed among 100 most invasive species worldwide and can lead to massive destruction and deterioration of aquatic life in freshwater ecosystems. It is no surprise that it has spread to more than 80 countries over the past century with its remarkable ability to multiply [1]. For example, 10 water hyacinth plants can reproduce into 655,360 plants, covering approximately half a hectare in 8 months [2].

Water hyacinth can kill

Growing uncontrollably when freshwater bodies are loaded with nutrients, it not only obstructs sunlight penetration into the deeper regions of the water bodies but also inhibits the photosynthesis rate for the submerged plants, which has a negative effect on aquatic life, gradually leading to eutrophication, slowing down water currents and deposition of debris at the bottom of the freshwater body [1]. 

Massive growth of water hyacinth also triggers hypoxic conditions (conditions that lead to decrease in oxygen content in the waters, that is crucial for plants and especially animals surviving in the water), declines the dissolved nutrients, disrupts the cyclical nutrient flow, and increases turbidity of surface water bodies. Rampant growth of this fast-growing weed can also slow down water currents leading to stagnation leading to conducive conditions for mosquito breeding and spread of diseases such as malaria, encephalitis, filariasis etc [1]. 

Dense growth of the weed in water can cause massive water losses through transpiration, which can be three times higher than natural evaporation. Infestation with water hyacinth can also negatively affect irrigation facilities through decreasing water flows and also interfere with recreational activities such as swimming, fishing, and boating. During flood events, heavy floating mats of the weed can dislodge and cause significant damage to downstream infrastructures such as bridges and fences, and to crops and pastures [2].

The physical removal of the water hyacinth is a laborious task and subsequent disposal and decomposition also poses serious environmental health concerns. Water hyacinth needs a sustainable strategy for its uncontrolled growth and management and preventing sewage from entering into water bodies is the best and single most and permanent solution to prevent it from invading water bodies.

However, as an immediate solution, making best use of the plant rather than using unsustainable methods of destroying it and harming aquatic life in the water bodies such as chemical sprays is important. 

Water hyacinths can have multiple uses

But the same weed that destroys can help in support livelihoods because of its multiple uses. The plant's biomass is useful for bioremediation of hazardous pollutants and metals, for production of biogas and biofuel, as a feed for fish and animals, as a carbon source for microbial metabolism, in vermicomposting and compost production and in manufacture of medicines.

Phytoremediation

Phytoremediation uses plants for cleaning up of soil or water so that either is free from both organic and inorganic impurities. Water hyacinth can be a suitable candidate for bioremediation and under controlled growth conditions can be an efficient and economical substitute to conventional cleanup methods as it speeds up the extraction and absorption of industrial and agricultural effluents contaminated with organic, inorganic, and toxic metals. Water hyacinth is capable of treating wastewater containing heavy metals and dissolved ions. The leaves, roots, and bulb tissues of the plant exhibit hyperaccumulation abilities for heavy metals [3].

Vermicomposting

The process of using earthworms to transform organic biomass into nutrient-rich compost that mainly comprises earthworms with a mixture of decomposed organic matter is called vermicomposting. The resulting compost functions as a natural manure and soil stimulant. Vermicompost can be obtained from organic waste decomposed by microbes in the digestive tracts of earthworms, and water hyacinth has been found to be a very good vermicomposting raw material. 

Composting remains among the most efficient methods of producing biofertilizers from water hyacinth. The presence of inorganic compounds such as nitrogen (N) and phosphorus (P) in the roots of the plant makes it an appropriate raw material for inorganic fertilizers and compost manufacture. Composting can also help to largely reduce the application of chemical fertilizers on agricultural fields, thus providing an eco-friendly agricultural approach. 

Compost made from water hyacinth has been found to be of a better quality and can be greatly useful to prevent secondary pollution. Compost made of water hyacinth, cow dung, and sawdust in the ratio 6 : 3 : 1 in India led to an increase in all nutrients (N, P, Na, K, and Ca) tested and improved compost stability, indicating that water hyacinth is a good raw material for compost production [3].

Fish feed

Water hyacinth can be used as a raw material in formulating fish feed. This may increase the crude protein level of the feed (due to the high protein content in the leaves and roots of the plant) and possibly help in digesting the feed better [3].

Biofuel production

low lignin in water hyacinth makes it a great choice for biomass, as cellulose and hemicellulose are converted with ease to sugar that is fermentable, resulting in great quantities of biomass that can be exploited in the biofuel industry [3].

Animal Feed Production

Dried water hyacinth contains high protein and minerals making it a useful source of animal feed and roughage [3]. 

Biogas Production

Biogas is the product of fermentation of organic materials in the absence of oxygen using microorganisms. Water hyacinth can be useful in the production of biogas because it possesses a high amount of hemicellulose. Attention is now being drawn toward the production of biogas as a source of fuel due to its cleanliness and cost. About three liters of biogas was reported to be produced when 2.5 kg of dried biomass of water hyacinth was mixed with cow dung and poultry droppings in the ratio 2 : 2 : 1 when the potential of water hyacinth to produce biogas was studied [3].

Medicinal Functions

Water hyacinth has anti-inflammatory, antifungal, and antibacterial functions, is used to treat cholera, sore throat, and snake bites. Water hyacinth was reported to demonstrate anticancer ability due to the presence of some cancer-fighting compounds [3].

Potential Rural Socioeconomic Benefits

Ropes and yarn can be made from the stem of water hyacinth. This can be processed further into baskets, hats, mats, and even furniture. Production of paper and cardboard from the weed can also be considered. For better quality, water hyacinth fiber may be blended with up to 50 percent jute or waste paper. Inhabitants of communities occurring around water bodies where this plant grows can begin to process the plant into useful products for income. Additionally, fiberboards can be made from it by small-scale industries and this can be used for indoor partitioning of ceilings and walls [3].

Efforts made in India to use water hyacinth

While earlier measures to remove the hyacinth have mostly been either through chemical treatments or manual removal, they have proven extremely ineffective and expensive. However, in recent years, the uses of water hyacinth have been realised and scientists are coming up with innovative methods to derive economic benefits from the various uses of water hyacinth that can serve as livelihood opportunities for rural communities. 

For example, in 2011, an initiative around the Harike Wildlife Sanctuary in Punjab, undertaken by World Wide Fund for Nature-India (WWF-India) selected two villages near the sanctuary to promote handicrafts created from water hyacinth. other attempts include making compost out of water hyacinth from Kapra lake in Hyderabad through accelerated anaerobic composting (AAC) technology. The leaves, stems and roots of water hyacinth are converted into good quality organic fertiliser within a span of 28 days under the intiative [4].  

Cellulase enzyme has also been made from bacteria using common aquatic weeds such as water hyacinth and water moss (Salvinia molesta). Three such major technologies viz. mushroom cultivation on specially prepared ‘beds’ made from the aquatic weeds, modified biomass briquettes, pulp based products from water hyacinth and modified hydroponics or floating agriculture have also been developed using water hyacinth as raw material [4].

A range of products such as disposable plates, ready-to-plant biodegradable nursery pots, egg and fruit trays, cartoon models, toys, file boards, multi-purpose boards, special canvas for paintings etc have also been attempted to be made from water hyacinth [4] along with textile fibres [8]. Students in a school in Kerala have also tried to make sustainable period pads from water hyacinth [5]. Aquatic weed water hyacinth has also been utilised to make ecofriendly handicrafts  and support livelihoods of rural women in Assam and Bengal [6, 7]. 

While innovative means of making use of water hyacinth to make sustainable and ecofriendly products is an option, preventing growth of water hyacinth in the first place by preventing sewage from entering into water bodies is the only way forward to deal with this menace on a permanent basis.