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This chapter includes some uses of aquatic plants not covered earlier in this handbook. There are probably many other uses which appear in the literature and have been overlooked, and many more, discovered by ingenious people in countries where every resource needs to be exploited, which have yet to be published.

The work of the U.S. National Academy of Sciences (1976) is helping to reveal and publish many of these uses. In their book there is a chapter on “Energy”, and another on “Aquatic plants for food and miscellaneous uses”. As the book is recent and readily available only brief reference is made herein to the wealth of information it contains.

Sculthorpe (1967) has included research into the classical literature for many useful and interesting references to the various uses to which aquatic plants were put in the past, many of which are relevant today.

1. Fuel

Casebow, A.J., 1967 Letter to the editor on the possibility of converting of water hyacinth to methane. PANS (C), 13(3):243–4

The author suggests that in Zaire water hyacinths would be suitable for methane generation by villagers living near the river. If mixed with goat or sheep manure hyacinth could be used, for example, in a type of methane generating apparatus developed in Kenya, known as the Hutchinson methane plant.

*India, Council of Scientific and Industrial Research, 1952 The wealth of India. Vol. 3. Raw materials. New Delhi, CSIR, pp. 130–4

Reviewing the uses of water hyacinth the article refers to its use for fuel.

“Many farmers in Bengal use dry hyacinth as fuel. The usual practice is to collect the plants at the beginning of the cold weather, leave them on high land to dry and use the dried material along with jute sticks as fuel. The ashes are subsequently used as manure.”

“The possibility of using the dried weed for the production of power gas and power alcohol has been considered. Three methods have been suggested, viz. saccharification by acid digestion and subsequent fermentation, gasification by air and steam with recovery of ammonia, and bacterial fermentation and utilization of the evolved gas for power production. Potassium chloride (0.1 ton of KCl per ton of dry hyacinth) is recovered in all the 3 processes. Starting from 1 ton of dried water hyacinth, 13 gallons of ethyl alcohol and 0.2 tons of residual fibre (7,700 B.t.u.) are obtained by the first process. Casification by air and steam at 800° gives, per ton of dried material, 82–116 lb. of ammonium sulphate and 40,000 cu. ft of gas (148.8 B.t.u.) containing hydrogen, 16.6; methane, 4.8; carbon monoxide, 21.7; carbon dioxide, 4.1; and nitrogen, 52.8. Bacterial fermentation gives per ton of material 26,500 cu. ft of gas (600 B.t.u.) containing: methane, 51.6; hydrogen, 25.4; carbon dioxide, 22.1; and oxygen, 1.2%. The commercial possibilities of the processes have not been proved.”

Mayberry, D.H., 1976 Fertilizer and fuel from tiny plants. Agric.Res., Wash., 25(1):7

The author describes the work of J.W. Newton, of the U.S. Department of Agriculture, with the blue-green alga Anabaena azollae. This nitrogen-fixing organism grows in a leaf cavity of the water fern Azolla.

If the fern is grown in the laboratory in water containing N fertilizer, or in an atmosphere free from N, or both, the N-fixing A. azolla, instead of fixing N, releases hydrogen. The amount of H released is comparable to the N-fixing activity of the alga. The author writes that although small-scale, and at a low rate, the laboratory production of hydrogen by the alga-fern system needs only water as a hydrogen source, and is not self-limiting. If hydrogen is to be considered as a fuel then the alga-fern symbiosis is particularly attractive as a system for biological production of gas.

U.S. National Academy of Sciences, National Research Council, 1976 Making aquatic weeds useful: some perspectives for developing countries. Washington, D.C. Agency for International Development, 175 p.

This book has an illustration (p.110) of an experimental biogas plant using water hyacinths. Details of optimum temperature (32–36°C), nutrient content (carbon to nitrogen ratio should be between 20:1 and 30:1), the need for regular stirring, control of acidity, and precautions to be taken are described. It is estimated that the amount of water hyacinth that can be grown in 1 ha of water could produce 70 000 m3 of methane gas valued, at the time of writing, at about US$5 000.

Other aquatic plants such as Lemna, Myriophyllum, Hydrilla, Alternanthera and algae have all shown promise for methane production, but research is needed to prove their value. Designs for small-scale biogas generators are needed to suit the water plants available and the particular conditions of different countries.

Wolverton, B.C. and R.C. McDonald, 1976 Don't waste waterweeds. New Sci., 71(1013):318–20

The authors describe the work being done to utilize water hyacinths to purify industrial and domestic wastes, and also report on the use of water hyacinths to produce biogas containing 60–80% methane, which is a promising substitute for natural gas. Research shows that 374 litres of biogas can be produced from 1 kg of dried water hyacinth. The fuel value of this gas is 21 000 BTU/m3 compared with 31 600 BTU/m3 for pure methane. A continuous supply of water hyacinths can be grown in domestic sewage lagoons where they perform an anti-pollution function. One hectare of water hyacinths fed on sewage nutrients can yield 0.9–1.8 tonnes of dry plant material/day. This biomass can produce 220–440 m3 of methane with a fuel value of 7–14 million BTU. In addition, the sludge that remains after fermentation is a useful fertilizer because it retains most of the N, all of the P and other minerals. Water hyacinths which clog water ways in many developing countries have a lower protein content than cultivated hyacinths. But they are still very useful for biogas production. The Sudanese Government (with the assistance of NASA through the U.S. Academy of Sciences) is experimenting with small-scale digesters to process the thousands of tons of water hyacinths mechanically harvested from the White Nile.

Wolverton, B.C., R.M. Barlow and R.C. McDonald, 1976 Application of vascular aquatic plants for pollution removal, energy and food production in a biological system. In Biological control of water pollution, edited by J. Tourbier and R.W. Pierson, Jr. Philadelphia, University of Pennsylvania Press, pp. 141–9

The authors describe and illustrate a proposed system for purifying industrial and domestic wastes by using the polluted water through a lagoon system. The last lagoon carries a crop of water hyacinth which extracts nutrients and other pollutants from the water. The system visualizes that the hyacinth is harvested regularly. The first process to which it is subjected is to be chopped into small pieces and then fed into a biogas converter. Then, after the yield of gas has been obtained, the residue of the hyacinths is processed to extract metals, for conversion to fertilizer, etc.

Wolverton, B.C., R.C. McDonald and J. Gordon, 1975a Bio-conversion of water hyacinths into methane gas. Part 1. NASA Tech.Memo., (TM-X-72725)

Laboratory experiments are described in which water hyacinths were fermented in anaerobic conditions and the yield of biogas and its content of methane measured. Biogas is the collective term for the mixture of gases evolved (mainly methane and carbon dioxide). It was found that preparation of the plant material, either as pieces 2.5 cm long, or macerated into a slurry, did not vary the amount of biogas evolved from a given sample. The temperature at which fermentation took place influenced the yield of biogas and the time lag before production began.

It was also found that if the water hyacinths had been grown in a solution containing nickel and cadmium the output of methane, and the proportion of methane in the biogas, were increased. The results are summarized in the following table:

Type of water hyacinth material (500 g fresh wt.)Temperature (°C) Time lag (days)Yield of methane/g fresh material (ml)Methane content in biogas (%)Yield of biogas over 65 days (ml/day)
Chopped (2.5 cm length)25±586.4–11.057.2–61.5-
Chopped with Ni+Cd*36111.391.187.5

* Concentrations in hyacinth: Ni = 9.95 ppm; Cd = 12.66 ppm

The authors conclude that sample preparation of water hyacinth, either chopped or blended, had no significant effect on biogas and/or methane production. Incubation of the experimental units at 36°C increased not only the rate of biogas production but also the methane content of the total biogas produced in these experiments. Pollution of the water hyacinths by two toxic heavy metals, nickel and cadmium, actually increased the rate of methane production and improved the methane content of the biogas evolved in the anaerobic decomposition of the contaminated plants.

2. Paper and Building Materials

Bakshi, T.S., 1964 Control of Vossia cuspidata. An aquatic weed of growing importance. Span, 7(1):37–9

Discussing the control and uses of the aquatic grass Vossia cuspidata in Sierra Leone, the author cites literature suggesting that the plant gives a low yield of short-fibred pulp of poor strength. Therefore paper made from it would be suitable for purposes for which high mechanical strength would be required (e.g. wrapping paper), but it could be used in the manufacture of printing and writing papers.

Chivu, A.I., 1968 Practical experiment in the cropping of reeds for the manufacture of pulp and paper - economic results. In pulp and paper development in Africa and the Near East. Rome, FAO, vol.2:877–99, FAO Access.No. 03953–68–MR

The author describes the harvesting and processing of the reeds (Phragmites communis) which occupy about 50% of the Danube delta. At the time of writing the cropping capacity was about 350 000 t/year. The capacity of the industry is 100 000 t of pulp per year. Chivu says that the pulp from the reeds is better and cheaper than the pulp derived from straw and bush, and has characteristics suitable for the manufacture of artificial fibres. The use of pulp from reeds in the proportion of 30–50% in the composition of printing and writing papers leads to qualitative improvements in the paper without involving any technical difficulties. The use of reeds has saved large amounts of timber which otherwise would have had to be used for paper.

Chivu also includes an economic and technical review of the processes of paper making with reeds.

*Gloor, A.M. and R.P. Gloor, 1950 Paper from water hyacinth. Australian patent 138, 426. August 21, 1950

Fresh leaf stalks (and optionally leaves) of Eichhornia crassipes are boiled about 25 minutes in aqueous KOH (5–10°Be') filtered, washed until neutral, filtered, sized with 20% solution of dammar resin in 90°EtOH, diluted to paper making concentration and formed into high-strength paper.

*India, Council of Scientific and Industrial Research, 1952 The wealth of India. Vol. 3. Raw materials. New Delhi, CSIR, pp. 130–4

Reviewing various uses for water hyacinth the article states: “Attempts have been made to utilize the plant as a raw material for paper, plastics and other commercial products, but so far no industry based on water hyacinth appears to have been established. The manufacture of paper from the dried weed has been attempted in Bengal. The fibrous stem, constituting about 40% of the whole plant, is suitable for paper making. The addition of jute or cotton fibres to the extent of 8–10% on the weight of the pulp is considered necessary as the paper prepared from the stems alone is translucent. The pulp may be pressed into boards and used for papier mache, or mixed with cement and whiting and moulded into tiles. A plastic material suitable for the production of moulded articles and boards has been prepared from water hyacinth.”

Nag, B., 1976 The destruction of water hyacinth by utilization. In Aquatic weeds in South East Asia, edited by C.K. Varshney and J. Rzoska. Proceedings of a Regional Seminar on noxious aquatic vegetation, New Delhi, 12–17 December, 1973. The Hague, Dr. W. Junk B.V. pp.383–5

The standard tests for artificial cellulose prepared from the non-cellulosic tissues of water hyacinth indicate that the weed could be used for manufacturing paper and other cellulosic materials such as artificial silk (rayon). (From Weed Abstracts)

Nolan, W.J. 1974 and D.W. Kirmse, The papermaking properties of waterhyacinth. Hyacinth Control J., 12:90–7

The authors subjected water hyacinth plants to processes which extracted the vascular bundles. The yield obtained of suitable raw material for pulp was a maximum of 20% of the original plant tissue. Pulping with sodium sulphite, and mixtures of sulphite and bisulphite, resulted in the highest yields - as high as 80–88% of material fed to the digesters. However at yields higher than 75% pulps were undercooked and could not be converted to papers of acceptable strength. The highly alkaline processes using sodium hydroxide and Kraft liquors resulted in pulps of much lower yields, mostly in the range of 40–50%.

Pulp yields of 65–75% resulted in paper handsheets of reasonably high strength. These apparently high yields, when converted to percentages of the original water hyacinth plant, were reduced to the very low values of 13–15%, since only a maximum of 20% of the whole plant was available to the pulping operation.

A serious defect in the hyacinth pulp was the extremely low “freeness”, or drainage rates, of the pulp compared to pine pulps. This would make the pulp unacceptable to the paper industry, even if fibre strength had been found superior to those of pine pulps. Additional disadvantages of hyacinth pulp were darkening and shrinking on drying. The shrinking led to erratic strength values and wrinkling of the dried sheets. All these findings led the authors to the conculsion that commercially acceptable paper pulps cannot be made from water hyacinths.

Steenberg, B., 1968 Papyrus: problems in its utilization for pulp and paper making. In Pulp and paper development in Africa and the Near East. Rome, FAO, vol.2: 865–76, FAO Accession No. 03952–68–MR

The author discusses the use of Cyperus papyrus and C. antiquorum for paper manufacture. He describes the ancient use of these plants for papyrus which was made by strips of the pith being laid together, overlapping, with a second series of strips applied at right angles to the first layer. On pressing and drying the strips adhered together to from the papyrus sheet.

The stem is the part concerned with paper making. It constitutes about 80% of the fresh weight of the aerial part of the plant, the remainder being the inflorescence. The inflorescence is about 33% of the dry weight of the plant in the case of C. antiquorum, and about 25% for C. papyrus. The pith of the stem weighs about 30% of the total weight of C. antiquorum but can amount to up to 80% of C. papyrus. When dry the cells collapse, making them useless for conventional paper making.

Although the stands of papyrus, as seen from the water, give an impression of covering large areas they do not normally extend from the water front for more than about 30 m. Beyond this range smaller water plants such as Vossia, Glyceria and other Cyperaceae take over.

A reasonable estimate of the yield of papyrus stands is given as 20 t of dry matter/ ha, though double this figure has been reported. From this 20–35% of pulp can be expected, which implies a yield of from 2–5% of the fresh weight.

The author cites the manufacture of building boards from papyrus in Uganda. Studies on the use of papyrus for hardboard have also been carried out.

Steenberg points out that papyrus is similar in value, for the production of pulp, to grasses and straw, the main question being whether supplies would be adequate. For a moderate-sized pulp mill producing 100 t/day, about 20 ha/day would have to be harvested. He concludes that the economic and technical problems of production of papyrus pulp seem overwhelming because of the difficulties of harvesting, the need for heavy machinery to separate the pith, and the lack of any valuable by-products apart from the pulp itself.

3. Medicinal

Sculthorpe, C.D., 1967 The biology of aquatic vascular plants. London, Edward Arnold, 610 p.

The author has searched the ancient literature for medicinal uses for aquatic plants (pp.517–520). The following summarizes his findings:

Acorus calamus, the sweet flag, a native of South-East Asia but naturalised in Europe, has had medicinal preparations made from the rhizome. These have been used for treatment of eye diseases, indigestion and colds. Even up to modern times it has been used as a general stimulant.

Pistia stratiotes was used in Egypt for healing skin diseases and wounds. In India it is used similarly after boiling the leaf juice in coconut oil. A preparation from the leaves in sugar and rosewater is taken for coughs and asthma. The roots provide a laxative and diuretic. Ringworm is treated by rubbing the ashes into the scalp.

Sculthorpe lists about 25 aquatic plants from which preparations have been made to treat a wide variety of complaints. Of these it is possible that some do actually contain active principles, about 15 different alkaloids having been isolated from members of the Nymphaeaceae. The long established use of the leaves of Nuphar as styptics, and infusions of the rooted parts as a lotion for skin ailments probably owes its success to the high concentration of tannic acid in these organs. Some species containing toxic substances can have unfortunate effects. For example, the acrid extracts of Alisma plantago-aquatica could cause complete paralysis. The use of Oenanthe aquatica for various complaints could cause narcotic poisoning.

Wasuwat, S., 1970 Extract of Ipomea pes-caprae (Convolvulaceae) antagonistic to histamine and jelly fish poison. Nature, Lond., 225:758

The uses of Ipomoea pes-caprae, abundant in Thailand close to the sea, are described. The author says that the leaves are used either boiled for external application as an anodyne, or powdered and used as an ointment against sores and ulcers. Thai fishermen use the plant as an antidote to jelly fish stings. Analysis has revealed that the plant does contain an active principle (IPA) that is antagonistic to jelly fish poison and is also mildly antihistaminic. The yield of IPA from leaves was about 0.05%. It is a volatile ester. Though it is less effective as an antihistamine compared with two recognized antihistamine drugs, it has about the same antagonistic effect against jelly fish poison.

Zafar, A.R., 1976 Economic significance of certain species of Scirpus sp. In Aquatic weeds in South East Asia, edited by C.K. Varshney and J. Rzeska. Proceedings of a Regional Seminar on noxious aquatic vegetation in tropics and sub-tropics, New Delhi, 12–17 December, 1973. The Hague, Dr. W. Junk, B.V. pp.387–91

The author cites evidence from the literature that the powdered underground parts of Scirpus grossus are useful in treating the human ailments dyspepsia and dysentery in India. It is possible that these parts accumulate benzenoid compounds.

4. Other

Moore, A.W., 1969 Azolla: biology and agronomic significance. Bot.Rev., 35(1):17–34

In a review of the literature on the water fern Azolla Moore cites a report (1926) that in central Africa certain tribes dried and burned water plants (Pistia, Lemna and Azolla) and by mixing fat with the ashes, rich in potassium, produced a crude soap.

Early in the century it was thought that Azolla could be useful for mosquito control when encouraged to form a dense mat over ponds. This gave the plant the name “mosquito fern”. This attribute has, however, not been established.

*Neogi, S. and K. Rajagopal, 1949 A method for the production of carotene concentrate from water hyacinth (Eichhornia crassipes). J.Sci.Ind.Res., India, 8B(7):119–21

The methods of production of carotene from fresh water hyacinths are described. Lots of 1 200 g of fresh leaves were dehydrated by several procedures. In one set of experiments the untreated leaves were dried at 60°C. In another set, leaves were chopped and blanched (immersion in boiling water for 3 minutes) and dried at 60° ±5°C. The carotene contents of samples treated by the two methods are as follows:

Carotene content(on dry basis)(mg/100 g)
UntreatedBlanched% Difference

Blanching hastens dehydration and raises the yield of carotene by about 42%.

Petroleum ether (b.p. 40–60°C) was used for Soxhlet extraction, and high-boiling petroleum ether (b.p. 80–100°C) was used for direct heating. The average yield of carotene is shown in the following table:

100 g of Dried leaves extracted for 6 hours

Moisture (%)Carotene content (mg)Petroleum ether (40–60°C)Petroleum ether 80–100°C)
Yield (mg)Recovery (%)Yield (mg)Recovery (%)

It is seen that a maximum yield of 85.3% is attainable when extractions are made by direct heating over a water bath employing high-boiling petroleum ether.

Soda ash is cheap and selective in adsorption. Of the adsorbed materials, the carotenoid pigments, being the least adsorbed constituents of the mixture, passed through, while the contaminants, chlorophylls and allied chromogens remained bound to the adsorbent. There was little decomposition of the pigments during the chromatographic analysis. Each tube was uniformly packed with well mixed soda ash and magnesia (6:1). Petroleum ether (40–60°C) was forced through the tubes until the columns were covered with the solvent. The process was continued until the washings began to show the brownish colour of chlorophylls.

The orange and light yellow bands were taken together as total carotenes.

To determine the yield of carotene obtainable, 3 kg of fresh, chopped leaves were blanched and dried at 60°C. The dried leaves were pulverized and extracted with petroleum ether (b.p. 80–100°C) and then separated chromatographically. The averaged results are given in the table below:

Extract from 3 kg of fresh leaves of water hyacinth

Moisture (%)Carotene content (mg)Yield (mg)Recovery (%)

Sculthorpe, C.D., 1967 The biology of aquatic vascular plants. London, Edward Arnold, 610 p.

Reviewing the literature, the author cites various uses for aquatic plants (pp.521– 522).

Nymphaea alba and Nuphar sp., because of their content of gallic or tannic acid, both of which have mordanting properties, have been employed in several European countries in dyeing and tanning, and also in brewing. Leaves of Menyanthes trifoliata have been used as a substitute for hops in brewing beer. In India Aeschynomene aspera provides a pith similar to balsa for various artifacts and for life jackets. The culms or leaves of Cyperus spp., Schoenoplectus spp. and Typha spp. are still in use in many parts of the world for weaving and basketry. The hairs of female Typha flowers were used to stuff pillows. The culms of Arundo donax have provided reeds for woodwind instuments for centuries. This plant has also been used to provide cellulose for rayon and has been considered for paper manufacture. It is also used for weaving, thatching and making walking sticks and fishing rods. Cyperus papyrus, in addition to being used for making papyrus, was made into ropes, canvas, and sails.

Sculthorpe refers to the Romanian industry based on Phragmites communis for pulp from which not only paper is made but cardboard, cellophane and various synthetic fibres. By-products include reed-blocks, fibre boards, furfural, alcohol and fuel, insulation material and fertilizer.

*Sheikh, N.M., S.A. Ahmed and S. Hedayetullah, 1964 The effect of root extraction of water hyacinth (Eichhornia crassipes) on the growth of microorganisms and mash kalai (Phaseolus mungo var. Roxburghii) and on alcoholic fermentation. Pak.J.Sci.Ind.Res., 7:96–102

The authors extracted substances from the roots of water hyacinths. They found that these substances, which were stable to heat up to 100°C, promoted the growth of fungi, yeasts and the roots of seedlings of Phaseolus mungo. By fractionation of the substances it was determined that organic compounds present were without effect and that therefore the growth promotion effects observed were due to inorganic compounds. The authors suggest that these inorganic substances extracted from water hyacinth could be used to promote yeast production and alcoholic fermentation.

*Sircar, S.M. and R. Chakraverty, 1962 The effect of gibberellic acid and growth substances from the root extract of water hyacinth, Eichhornia crassipes, on rice and gram. Indian J.Plant Physiol., 5:1–2

The authors' summary of their work with water hyacinth root extracts on the growth of rice is as follows:

“The effect of gibberellic acid (GA) and growth-regulating substances of the root extract of water hyacinth (RWH) on the growth and flowering behaviour of rice and gram were investigated. The treatments consisted of 100 ppm GA, root extract of water hyacinth in the concentration of 1:5 and 100 ppm GA plus the root extract mixed in the proportion of 1:1 (GA+RWH). The spraying commenced with 40-day-old plants and continued once a week till the time of flowering. All the treatments resulted in an increased height in both rice and gram plants. Death of the apical meristem after GA treatment in gram was noted. GA further decreased tillering in rice and lateral branches in gram, while RWH and GA+RWH increased their growth to a great extent. All the treatments induced flowering earlier than the control and the maximum earliness was noted with plants treated with GA. Although GA increased the length of the spike in rice it was associated with a low percentage of grain formation and the grain yield per plant was greatly reduced. Between the treatments RWH showed the best effect as the yield and percentage of grains was greater than with other treatments.”

*Sircar, S.M. and A. Ray, 1961 Growth substances separated from the root of water hyacinth by paper chromatography. Nature, Lond., 190(4782):1213–4

In this paper the authors describe the treatment in the laboratory of the roots of water hyacinth to extract substances which, they conclude, are additional to indole compounds or gibberellins.

*Villadolid, D.V. and D.M. Bunag, 1953 New uses for water hyacinths. Philipp.Fish.Yearb., 1953:80–1, 241–2

Discussing the various uses of the water hyacinth the authors state that during the war the plant was utilized for the manufacture of soft soap by burning the plant and getting the lye from the ash by leaching.

Fisherman setting net using water hyacinth as floats on Rawa Pening lake, Central Java, Indonesia

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