Eichhornia Crassipes Make Biogas

Eichhornia Crassipes

Eichhornia crassipes, commonly known as Common Water Hyacinth, is an aquatic plant native to the Amazon basin, and is often considered a highly problematic invasive species outside its native range.

Its habitat ranges from tropical desert to subtropical or warm temperate desert to rainforest zones. It tolerates annual precipitations of 8.2 dm to 27.0 dm (mean of 8 cases = 15.8 dm), annual temperatures from 21.1°C to 27.2°C (mean of 5 cases = 24.9°C), and its pH tolerance is estimated at 5.0 to 7.5. It does not tolerate water temperatures >34°C. Leaves are killed by frost and salt water, the latter trait being used to kill some of it by floating rafts of the cut weed to the sea. 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.

Because of its extremely high rate of development, Eichhornia crassipes is an excellent source of biomass. One hectare of standing crop can 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 (895 Btu/ft3)

Wolverton and McDonald report only 0.2 m3 methane per kg, indicating requirements of 350 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 (800°) gives circa 40,000 ft3 (circa 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., 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.,