Water hyacinth is a free-floating perennial aquatic plant native to tropical and sub-tropical South America. With broad, thick, glossy, ovate leaves, water hyacinth may rise above the surface of the water as much as 1 meter in height. The leaves are 10ââ¬â20 cm across, and float above the water surface. They have long, spongy and bulbous stalks. The feathery, freely hanging roots are purple-black. An erect stalk supports a single spike of 8-15 conspicuously attractive flowers, mostly lavender to pink in colour with six petals.
One of the fastest growing plants known, water hyacinth reproduces primarily by way of runners or stolons, which eventually form daughter plants. Each plant can produce thousands of seeds each year, and these seeds can remain viable for more than 28 years The common water hyacinth are vigorous growers known to double their population in two weeks.
Its habitat ranges from tropical desert to subtropical or warm temperate desert to rainforest zones. The temperature tolerance of the water hyacinth is the following; its minimum growth temperature is 12ðC; its optimum growth temperature is 25-30ðC; its maximum growth temperature is 33-35ðC, and its pH tolerance is estimated at 5.0 to 7.5. It does not tolerate water temperatures >35ðC. Leaves are killed by frost and salt water. Water hyacinths do not grow when the average salinity is greater than 15% that of sea water. In brackish water, its leaves show epinasty and chlorosis, and eventually die.
Azotobacter chroococcum, an N-fixing bacteria, is probably concentrated around the bases of the petioles. But the bacteria do not fix nitrogen unless the plant is suffering extreme N-deficiency.
Fresh plants contain prickly crystals. This plant is reported to contain HCN, alkaloid, and triterpenoid, and may induce itching.
Because of its extremely high rate of development, water hyacinth is an excellent source of biomass. One hectare of standing crop thus produce more than 70,000 m3 of biogas. According to Curtis and Duke, one kg of dry matter can yield 370 liters of biogas, giving a heating value of 22,000 kJ/m3 (580 Btu/ft3) compared to pure methane (33,950 kJ/m3).
Wolverton and McDonald report only 0.2 m3 methane per kg, indicating requirements of 6000 MT biomass/ha to attain the 70,000 m3 yield projected by the National Academy of Sciences (Washington). Ueki and Kobayashi mention more than 200 MT/ha/yr. Reddy and Tucker found an experimental maximum of more than a half ton per day. Bengali farmers collect and pile up these plants to dry at the onset of the cold season; they then use the dry water hyacinths as fuel. They then use the ashes as fertilizer. In India, a ton of dried water hyacinth yield circa 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 (800ð) gives circa 40,000 ft3 (circa 1,100 m3) natural gas (143 Btu/cu ft) containing 16.6% hydrogen, 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. A continuous, hydraulic production system could be designed, which would provide a better utilization of capital investments than in conventional agriculture, which is essentially a batch operation.
The labour involved in harvesting water hyacinth can be greatly reduced by locating collection sites and processors on impoundments that take advantage of prevailing winds. Wastewater treatment systems could also favourably be added to this operation. The harvested biomass would then be converted to ethanol, natural gas, hydrogen and/or gaseous nitrogen, and fertilizer. The resulting byproducts of water and fertilizer can both be used to irrigate nearby cropland.
The roots of Eichhornia crassipes naturally absorb pollutants, including 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. Water hyacinths can be cultivated for waste water treatment.
Water hyacinth is reported for its efficiency to remove about 60ââ¬â80 % nitrogen (Fox et al. 2008) and about 69% of potassium from water (Zhou et al. 2007). The roots of water hyacinth were found to remove particulate matter and nitrogen in a natural shallow eutrophicated wetland (Billore et al. 1998).
The plant is used as a carotene-rich table vegetable in Taiwan. Javanese sometimes cook and eat the green parts and inflorescence.
In East Africa, water hyacinths from Lake Victoria are used to make furniture, handbags and rope. The plant is also used as animal feed and organic fertilizer although there is controversy stemming from the high alkaline pH value of the fertilizer. Though a study found water hyacinths of very limited use for paper production, they are nonetheless being used for paper production on a small scale.
One of the fastest growing plants known, water hyacinth reproduces primarily by way of runners or stolons, which eventually form daughter plants. Each plant can produce thousands of seeds each year, and these seeds can remain viable for more than 28 years The common water hyacinth are vigorous growers known to double their population in two weeks.
Its habitat ranges from tropical desert to subtropical or warm temperate desert to rainforest zones. The temperature tolerance of the water hyacinth is the following; its minimum growth temperature is 12ðC; its optimum growth temperature is 25-30ðC; its maximum growth temperature is 33-35ðC, and its pH tolerance is estimated at 5.0 to 7.5. It does not tolerate water temperatures >35ðC. Leaves are killed by frost and salt water. Water hyacinths do not grow when the average salinity is greater than 15% that of sea water. In brackish water, its leaves show epinasty and chlorosis, and eventually die.
Azotobacter chroococcum, an N-fixing bacteria, is probably concentrated around the bases of the petioles. But the bacteria do not fix nitrogen unless the plant is suffering extreme N-deficiency.
Fresh plants contain prickly crystals. This plant is reported to contain HCN, alkaloid, and triterpenoid, and may induce itching.
Because of its extremely high rate of development, water hyacinth is an excellent source of biomass. One hectare of standing crop thus produce more than 70,000 m3 of biogas. According to Curtis and Duke, one kg of dry matter can yield 370 liters of biogas, giving a heating value of 22,000 kJ/m3 (580 Btu/ft3) compared to pure methane (33,950 kJ/m3).
Wolverton and McDonald report only 0.2 m3 methane per kg, indicating requirements of 6000 MT biomass/ha to attain the 70,000 m3 yield projected by the National Academy of Sciences (Washington). Ueki and Kobayashi mention more than 200 MT/ha/yr. Reddy and Tucker found an experimental maximum of more than a half ton per day. Bengali farmers collect and pile up these plants to dry at the onset of the cold season; they then use the dry water hyacinths as fuel. They then use the ashes as fertilizer. In India, a ton of dried water hyacinth yield circa 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 (800ð) gives circa 40,000 ft3 (circa 1,100 m3) natural gas (143 Btu/cu ft) containing 16.6% hydrogen, 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. A continuous, hydraulic production system could be designed, which would provide a better utilization of capital investments than in conventional agriculture, which is essentially a batch operation.
The labour involved in harvesting water hyacinth can be greatly reduced by locating collection sites and processors on impoundments that take advantage of prevailing winds. Wastewater treatment systems could also favourably be added to this operation. The harvested biomass would then be converted to ethanol, natural gas, hydrogen and/or gaseous nitrogen, and fertilizer. The resulting byproducts of water and fertilizer can both be used to irrigate nearby cropland.
The roots of Eichhornia crassipes naturally absorb pollutants, including 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. Water hyacinths can be cultivated for waste water treatment.
Water hyacinth is reported for its efficiency to remove about 60ââ¬â80 % nitrogen (Fox et al. 2008) and about 69% of potassium from water (Zhou et al. 2007). The roots of water hyacinth were found to remove particulate matter and nitrogen in a natural shallow eutrophicated wetland (Billore et al. 1998).
The plant is used as a carotene-rich table vegetable in Taiwan. Javanese sometimes cook and eat the green parts and inflorescence.
In East Africa, water hyacinths from Lake Victoria are used to make furniture, handbags and rope. The plant is also used as animal feed and organic fertilizer although there is controversy stemming from the high alkaline pH value of the fertilizer. Though a study found water hyacinths of very limited use for paper production, they are nonetheless being used for paper production on a small scale.