328 Organic waste recycling: technology and management
Cattail is another weed that can be used as a source of pulp, paper and fiber.
Its leaves and stems are suitable for papermaking, and the paper obtained is
fairly strong but difficult to bleach. Bleaching is however not essential for the
production of wrapping paper which is in great demand nowadays. Cattail
leaves yield a soft fiber that can be used in mats, baskets, chair seats, and other
woven articles. Because they swell when wet, the leaves are good for caulking
cracks in houses, barrels, and boats. Studies in Mexico show that woven cattail
leaves coated with plastic resins have potential as place mats, building siding,
and roof tiles. The resulting product is as strong as fiberglass (NAS 1976).
At the University of Florida, U.S.A., attempts to make paper from water
hyacinth were carried out (Bagnall et al. 1974). Different pulping materials and
conditions were used, but it failed to produce suitable pulp. Reasons for the
failure were:
- Very low fiber yield
- Excessive shrinkage of the paper on drying, and subsequent
wrinkling - Brittleness of the paper
- Poor tear properties
Because of the low yield, it was felt that the use of water hyacinth for pulp
would not be profitable even if it were delivered to the pulp plant at no cost.
However, dried water hyacinth petioles (leaf stalks) are woven into baskets
and purses in Philippines (NAS 1976). In Thailand, water hyacinth leaves are
used as a cigar wrapper and for preparing plastic molded materials like
furniture, electric insulation board, radio cabinets, and biodegradable pots for
flower plants, etc.
Biogas and power alcohol
Chopped water hyacinth alone without dewatering or mixed with animal manure
or human waste can be anaerobically digested to produce methane gas (see
Table 4.7). Nutrients such as P and K are provided in adequate proportions by
water hyacinth. Digestion takes about 10-60 days and requires skilled
supervision. Table 7.3 shows the production of several volatile fatty acids
during anaerobic digestion of a mixture of cattle dung and water hyacinth. The
highest biogas production and methane content were achieved during the
digestion period of 30-60 days. It is estimated that water hyacinth harvested
from 1 ha will produce approximately 70,000 m^3 of biogas.
Each kg of water hyacinth (dry weight) yields about 370 L of biogas with an
average methane content of 61% and the fuel value was about 22,000 kJ/m^3.
Temperature has a marked effect on biogas production. The biogas was