A substantial research programme conducted over the last twenty years in many countries has failed to identify a use for water hyacinth that can be applied on a large scale and is economically justifiable. Of the many experiments to utilize water hyacinth the making of briquettes from the dried ground plant appears to be most promising. However, more energy is expended in collecting and transporting the plant than is returned from its heat as a briquette. In a limited number of situations water hyacinth has been used to extract nutrients and heavy metals from water, but the plants have to be harvested, otherwise the extracted chemicals are recycled when the plant dies.
The two major obstacles with water hyacinth utilization are the high cost of harvesting and the low dry matter content of the plant - it is 95 percent water. In the St. Johns River, Florida, USA clearing water hyacinth from 1 ha has cost as much as US$ 3 000/year.
In Lake Edku the cost of harvesting, transporting to the shore and dumping (assuming 2 000 t net weight per hectare and a distance of 1 km on water) is calculated to be between LE 300 and 600. However, if the harvesting procedure is not rapid, the water hyacinth will multiply faster than its removal. This plant has an extraordinary capacity to multiply vegetatively. Under optimum conditions the rate is 2.7 daughter plants per week or 140 × 106 in six months. Theoretically 28 000 t of fresh weight can be produced from one plant over the course of a year.
After harvesting the plants, there is the further problem of spreading and drying the water hyacinth in the sum. Other uses for water hyacinth include its use as mulch, for the production of methane gas, for pulping into paper and for food for stock. None of these uses have proved economically successful, as shown by careful scrutiny of the most recent literature on the topic from Sudan and other countries where there has been an abundance of aquatic weeds.
This reed has been used by man down through the millenia and on a limited scale this practice continues. A small industry exists in Edku town where the reed is used for trellising, brooms, blinds, temporary shelters, decoration, fencing, wind-breaks and thatching.
There are several pulp manufacturing factories processing reed, situated in Romania, Sweden, Turkey and some other countries. In Egypt, the Rachta Pulp Mill has operated near Maadi since the 1940s. This mill used reeds in the past, but the practice has been discontinued and the present prime source of fibre is from rice straw. The pulp mill in Turkey was visited by the author prior to travelling to Egypt, for the purpose of assessing the feasibility and economics of such a venture.
The Seka Afyon Pulp Mill in central Turkey is a large mill built at great cost (estimated at more than US$ 20 million) in the late 1970s and it has a capacity of 120 000 t/year or 400 t/day. At present its throughput is 50 000 t. This is made up by a 60/40 mixture of Phragmites/cereal straw plus an additional large (50 percent) amount of wood (conifer) pulp. It is then rolled and dried with steam and bleached. The manager of the mill advised that making paper from straw and reeds is expensive compared with wood. The speed with which the pulp can be dried ultimately determines the profit (or loss) of the manufacturer. The parenchyma cells of reeds do not separate easily and require more processing than wood. The Seka mill obtained Phragmites from Lake Eber (126 km2) and Karamik (40 km2). Approximately 1 000 people are employed at the mill and 200 employed as manual cutters.
The reed is cut in the autumn and winter. In winter the lakes seldom freeze sufficiently to support wheeled machines and 30 percent of the reeds cannot be harvested as the ice is too thick to walk on. Large reed cutters developed by the Romanians in the reed beds of the Danube delta have been brought for use on Lakes Eber and Karamik. Although these machines have balloon tires, they have not been used as they are considered too heavy for the ice. It was noted that reeds are most efficiently harvested on thick ice. At this time the roots are not damaged, and the culms and leaves have achieved maximum dryness (25 percent water). Harvesting in water, as would be the case in Egypt, significantly increases the cost.
Effluent from the mill was of major concern. The process uses a lot of water and a pipe brought fresh water from Lake Karamik to the factory. The water, after use, has a very high BOD and is dirty brown in colour. Following some oxygenation the effluent water was returned to the other end of Lake Karamik (i.e., the most distant point from where the freshwater was taken). The manager said that this recycling process had been in operation for one year and already the water in Lake Karamik was turning brown. It was evident (although it was not possible to obtain figures on production cost) that the reeds did not provide a good economical source of pulp for paper when all factors were properly costed.
Research in Sweden has produced marginally promising results when the reeds are made into briquettes for heating and cooking.
In Sweden the dry (25 percent water) reeds are harvested from ice in the winter. The culms and leaves are then ground into powder and compressed into briquettes. The calorific value is 5 kWh/kg dry matter (18 000 kcal/kg), whereas oil for heating purposes has an energy content of about 12 kWh/kg. This gives an oil/reed quotient of 2.4:1. For practical purposes 1 m3 of oil equals 4 t dry reed. One m3 of oil at US$ 350 (Sweden) has to be compared with the cost of harvesting and briquetting 4 t of reed. To be competitive at that price each ton of reed briquettes cannot exceed US$ 90. The positive aspect of using reed briquettes is that when burnt they produce low levels of sulphur.
The economic utilization of Phragmites for energy depends on the cost of harvesting. As already mentioned, harvesting costs on ice are considerably less than harvesting costs on water as would be the case in Egypt. Also harvesting in water would probably damage the productivity of the Phragmites and leave open space for the invasion of water hyacinth.
In conclusion, at present a large-scale utilization of major aquatic plants of Lake Edku appears uneconomical and is therefore not recommended.
