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Eichornia crassipes (Mart.) Solms

Pontederiaceae
Waterhyacinth

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.

  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Toxicity
  5. Description
  6. Germplasm
  7. Distribution
  8. Ecology
  9. Cultivation
  10. Harvesting
  11. Yields and Economics
  12. Energy
  13. Biotic Factors
  14. References

Uses

An NAS report (1976) explores the potential conversion of water weeds to fertilizer, food, fuel, paper, fiber, and energy. Subsistence farmers in Bangladesh face disaster when rafts of water hyacinth weighing up to 300 MT/ha float over their rice paddies. As the floods recede, the weeds remain on the germinating rice, thus killing it. Bengalis have learned to use the enemy for fuel and fertilizer. Engineers have estimated that the Panama Canal would be impassable within three years without continuous aquatic weed control measures. Aquatic weeds may require absorbent materials such as dried industrial mill by-products to ferment good silage. In Florida, dried citrus pulp and molasses have been added to water hyacinth residues as sources of carbohydrate and absorbent. Byproducts of the rice, grain, and sugarcane milling industries and waste cassava are potential substitutes. Edible water spinach (Ipomoea aquatica) already occurs intermingled with water hyacinth in Panama (Curtis and Duke, 1982). Through an anaerobic fermentation process, polluted hyacinths can be converted to the natural gas methane--a costly process that may become more economical as supplies of underground natural gas are depleted. Dried and cleansed plants, can be used as fertilizer, poultry feed, additives to cattle-feed, and plant mulch. Eventually, living aquatic plants might serve aboard long-distance manned spacecraft, absorbing wastes and converting carbon dioxide to oxygen, then being themselves converted into food. "I fully intend to solve a major pollution problem, a major energy problem, a major food problem, and a major fertilizer problem," declares Wolverton (as quoted in BioScience Vol. 26, No. 3, March 1976). And lowly water hyacinths have given him a head start. Wolverton and McDonald (1981) note "cultivation of higher plants for use in wastewater treatment, and incorporation of these plants into a system where the biomass is harvested for fuel production is economically appealing at the present time. Since this biomass is a by-product of wastewater treatment, it has a positive environmental impact, and thus poses no threat as competitor to food, feed, or fiber-producing plants." The plant has been used for cigar wrappers and, as a mushroom growing medium (Holm et al., 1977) but seems unsatisfactory for paper and pulp. Said to be used as a carotene-rich table vegetable in Formosa. Javanese sometimes cook and eat the green parts and inflorescence. In Africa, fresh plants are used as cushions in canoes and to plug holes in charcoal sacks. Chinese cultivate the water hyacinth in fish ponds as pig fodder, the pig manure recycled into the fish pond. Fish taken from the manured pond are transferred to clean tanks and fed more wholesome food before human consumption. In India, where yields of 150 MT fodder/ha/yr are reported, the water hyacinth is fed to water buffalos (ca 7 kg/day fresh fodder) which are said to exhibit 10-15% milk increases (but the milk is more watery).

Folk Medicine

It is strange to me that this pantropical weed has acquired such a small medicinal folklore. In Kedah (Java), the flowers are used for medicating the skin of horses. Duke and Wain (1981) report only that the species is "tonic."

Chemistry

Fresh plant contains 95.5% moisture, 0.04% N, 1.0% ash, 0.06% P2O5, 0.20% K2O, 3.5% organic matter. On a zero-moisture basis, it is 75.8% organic matter, 1.5% N, and 24.2% ash. The ash contains 28.7% K2O, 1.8% Na2O, 12.8% CaO, 21.0% Cl, and 7.0% P2O5. The CP contains, per 100 g, 0.72 g methionine, 4.72 g phenylalanine, 4.32 g threonine, 5.34 g lysine, 4.32 g isoleucine, 0.27 g valine, and 7.2 g leucine (Matai and Bagchi, 1980). Water hyacinth roots naturally absorb pollutants, including such toxic chemicals as lead, mercury, and strontium 90 (as well as some organic compounds believed to be carcinogenic) in concentrations 10,000 times that in the surrounding water (BioScience 26(3): 224. 1976). Nutritive values are tabulated by Gohl (1981) in the following table:

As % of dry matter
DM CP CF Ash EE NFE Ca P
Fresh, green part, India5.9 13.1 18.215.3 1.3 52.1 2.16 0.41
Fresh, green part, Philippines 7.8 12.8 24.6 11.9 3.3 47.4
Hay, India 11.6 24.2 17.8 0.7 45.7 2.19 0.64
Silage, Philippines 10.1 9.9 19.7 19.0 1.5 49.9
Haylage, India 33.5 11.4 24.5 20.1 1.4 42.6 2.02 0.23
Haylage with 2% salt, India 46.8 13.9 17.4 18.9 1.5 48.3 1.70 0.21
Dried root, Sudan 92.7 5.8 20.5 3.7 0.9 69.1
Digestibility (%)
Animal CP CF EE NFE ME
Hay Zebu 37.9 62.1 53.4 60.4 1.76
Silage Sheep56.1 57.1 76.2 78.5 2.15

Toxicity

Eating the plant, reported to contain HCN, alkaloid, and triterpenoid, may induce itching (Perry, 1980). Fresh plants contain prickly crystals. Plants sprayed with 2,4-D may accumulate lethal doses of nitrates (Gohl, 1981).

Description

Perennial aquatic herb; rhizome and stems normally floating,rooting at the nodes, with long black pendant roots. Leaves usually with inflated spongy petioles, the leaf blades circular to reniform, 4-12 cm wide. Inflorescence a contracted panicle, 4-15 cm long, with several flowers; perianth lilac, bluish- purple, or white, the upper lobe bearing a violet blotch with a yellow center. Stamens 6; stalk of the inflorescence soon becoming goose-necked, forcing the dead flowers under the water; capsule dehiscent, surrounded by the perianth, membraneous, many-seeded (Reed, 1970). (Ag. Handbook 366)

Germplasm

Reported from the South American Center Of Diversity, waterhyacinth, or cvs thereof, is reported to tolerate grazing and waterlogging. (2n = 32)

Distribution

Native to Brazil, now growing in most tropical and subtropical countries. Holm et al (1979) list more than 50 countries in which waterhyacinth is weed.

Ecology

Estimated to range from Tropical Desert to Rain through Subtropical or Warm Temperate Desert to Rain Forest Life Zones, waterhyacinth is reported to tolerate annual precipitation of 8.2 to 27.0 dm (mean of 8 cases = 15.8), annual temperature of 21.1 to 27.2°C (mean of 5 cases = 24.9), and estimated pH of 5.0 to 7.5. Leaves are killed by frost, and plants cannot tolerate water temperatures >34°C.

Cultivation

Apparently harvesting is more critical than cultivation. Seeds can tolerate submersion or desication for 15 years and still germinate. Scarification, but not light, may be required for germination. Recently there has been interest in cultivating waterhyacinths for waste water treatment.

Harvesting

Rafts of waterhyacinth have been harvested manually, with specially equipped dredges, rakes, and have been mechanically piled by crushers, elevators, grapplers, rollers, sawboats, etc. Rafts have even been towed to sea; where the salt water kills it. Wilted water hyacinth, mixed with earth, cow dung, and woodashes in the Chinese compost fashion, can yield compost in two months.

Yields and Economics

Although yields are incredible, so are the costs of removal or attempted eradication of this water weed. Standing crops have been estimated to produce 100-120 MT/ha/yr. Under ideal conditions, each plant can produce 248 offspring in 90 days (Matai and Bagchi, 1980). Murry and Benemann (1981) compare various standing crops of waterhyacinth, rounded off to 13-15 MT/ha in Louisiana, 6-21 in Alabama, 30 in Iowa, 11 in Mississippi. Perhaps more meaningful were their productivity figures, ca 13-15 in Louisiana, 5-28 in Alabama, 4-29 in Iowa, 5-54 in Florida, up to 88 in Mississippi on sewage effluent. In Florida, an upper limit on the value was set at $6.42 per wet ton, when used in a compost blend. Mara (1976) doubted that the value of the waterhyacinth would cover the cost of transporting and spreading as a soil amendment. Further, if all the cattle in Florida were fed year round, that would require <3% of the hyacinth.

Energy

According to the phytomass files (Duke, 1981), annual productivity ranges from 15-30 MT/ha. Holm et al (1977) suggest that a floating mat of medium sized plants may contain 2,000,000 plants/ha weighing 270-400 MT wet (15-20 MT DM). Benemann (1981) concludes, however, that in Southern US, productivity should be 80 MT/ha DM compared to 40-60 for green algae and marsh plants. Comparing DM yields of more than 20 genera representing many life forms in Florida, Smith and Dowd (1981) gave the highest figure, 88 MT/ha/yr to waterhyacinth, followed by Hydrocotyle at 58, napier grass at 57, and sugarcane at 54. While not exactly representing head-on trials, the following Table, synthesized from several produced by Smith and Dowd (1981) suggests that waterhyacinth is more productive of biomass than other items tabulated.

DM MT/ha/yr
Azolla 10
Beta 4.4-11.7
Brassica 3-10
Casuarina equisetifolia 8.3
Cichorium intybus 5.5-7.9
Colocasi esculenta 9-19
Cynodon dactylon 23.5-24.6
Daucus carota 2.5-5.5
Eichornia crassipes 30-88
Elodea 3
Eucalyptus 5.6-20
Helianthus tuberosus 2.2-9.5
Hydrilia 15
Hydrocotyle umbellata 20-58
Ipomoea batatas 7-23
Lemna 12
Manihot esculenta 2-17
Melaleuca quinquenervia 28.5
Paspalum notatum 22.4
Pennisetum sp. (Napier) 57.3
Pinus clausa 9.0
Pinus elliottii 9.4
Saccharum 32-54
Sorghum 16-37
Sorghum 'Sordan' 22.4
Typha sp. 20-40
Once harvested and dried, the dry matter of the water hyacinth is roughly equivalent to the dry matter of our other species in terms of energy. Some might argue that the hydrocarbon plants have a higher energy value than a cellulosic plant per unit dry matter. But for our purposes, we can generally assume that 1 metric ton dry matter is approximately equivalent to 2.4 bbls of oil. Although estimates will vary in any given study, NAS (1976) suggests that one ha of water hyacinth can produce more than 70,000 m3 of biogas (70% methane, 30% CO2). Each kg of dry matter will yield 370 liters biogas with a heating value of 22,000 KJ/m3 (580 Btu/ft3) compared to pure methane (895 Btu/ft3) (Curtis and Duke, 1982). Wolverton and McDonald report only 0.2 m3 methane 7 per kg indicating requirements of 350 MT biomass/ha to attain the 70,000 m3 yield projected by NAS. Ueki and Kobayashi (1981) expect more than 200 MT/ha/yr. Reddy and Tucker (1983) report experimental maximum of more than a half ton a day. The liquid sludge is an organic fertilizer with soil conditioner as a byproduct (Curtis and Duke, 1982). Bengali farmers use dry water hyacinths as fuel, collecting and piling them up to dry at the onset of the cold season (C.S.I.R., 1948-1976). The ashes are then used as fertilizer. In India, a ton of dried water hyacinth yield ca 50 liters ethanol and 200 kg residual fiber (7,700 Btu). Bacterial fermentation of one ton yields 26,500 cu ft gas (600 Btu) with 51.6% methane, 25.4% hydrogen, 22.1% CO2, and 1.2% oxygen. Gasification of one ton dry matter by air and steam at high temperatures (800°) gives ca 40,000 ft3 (ca 1,100 m3) natural gas (143 Btu/cu ft?) containing 16.6% H3, 4.8% methane, 21.7% CO, 4.1% CO2, and 52.8% N. The high moisture content of water hyacinth, adding so much to handling costs, tends to limit commercial ventures. In arid climates with natural impoundments, cluttered with water hyacinth, the water might be viewed positively rather than negatively. Taking advantage of prevailing winds, collections and processors might be located on an impoundment (perhaps even a wastewater treatment system). The harvested biomass could be converted to ethanol, natural gas, even hydrogen and nitrogen (who needs gaseous N), fertilizer, the byproduct water and fertilizer used to irrigate nearby cropland. Since waterhyacinth is intolerant of salt, salinization might eventually jeopardize this venture. Waterhyacinths do not occur in water with average salanities greater than 15% that of sea water. In brackish water, its leaves show epinasty and chlorosis, eventually dying. Saltcedars (Tamarix) might be planted to mine the salts, themselves being used in the production of fuel and fertilizer (somewhat salty). I'm inclined to agree with Benemann (1981), "Development of aquatic plant systems for waste treatment and food-feed-fiber-fuel production may be a prudent investment with a large potential return...In case of microalgae and water hyacinth, a continuous, hydraulic production system can be designed. This allows better utilization of capital investments than in conventional agriculture, which is essentially a batch operation."

Biotic Factors

Azotobacter chroococcum, an N-fixing bacteria, may be concentrated around the bases of the petioles but doesn't fix N unless the plant is suffering extreme N-deficiency (Matai and Bagchi, 1980). Neochetinia eichhorniae, imported to Florida from Argentina in 1972, has caused "a substantial reduction in waterhyacinth production" (in Louisiana) in the form of reduced plant height, weight, root length, and fewer daughter plants (Goyer and Stark, 1981).

References

Complete list of references for Duke, Handbook of Energy Crops
last update July 9, 1996