Agriculture Reference
In-Depth Information
Now-a-days world's increasing attention is focusing on aquatic biomass residue
because the aquatic surface on earth is several times larger than the land available
and most of the dry land of whole globe and surfaces is in the process of being
exploited. The land available for terrestrial biomass growth is becoming limited. In
this endeavor, many aquatic plants multiply so fast and termed as weeds (Agrawal
and Gopal
2013
) can be utilized as important biomass resources for composting
process as well as in variety of applications compatible with the ecosystems. Aquat-
ic weeds have high biomass productivity in comparison to that of terrestrial plants
because they need not to be water stressed and can optimally supplied with nutrients
in solubilized form. Another interesting aspect is that the large cultivation of aquatic
plants and their degradation has been suggested to generate animal feed as well as
potential energy source (Benemann
1981
).
The concept of cultivation of aquatic plants/biomass for energy dates back 25
years when microalgae were suggested as renewable source of methane (Meier
1977
). A related study (Ashare
1978
) using a similar design concept and analysis
concluded that emergent aquatic plants would be favored over microalgae because
these do not be limited by availability of an enriched CO
2
source. Thus, aquatic
biomass seems to exhibit higher yield than that of land biomass. Hence, water-based
biomass considered to be most suitable for their diverse applications. According to
Benemann (
1981
), there are several advantages of aquatic biomass to that of terres-
trial plants as the former has continuous hydraulics production system, independent
of soil characteristics and short generation time. Besides, the plants do not weather
stressed resulting in higher productivity. Further, these can be grown in brackish
and waste water, contain low lignin and thus easily accessible for bioconversion of
cellulose components by microbial cellulases.
Interestingly, floating and submerged macrophytes supported considerably more
number of bacteria and fungi than emergent macrophytes. Bacteria were better
equipped than fungi to act under partial anaerobic environment of lakes indicated
that most of bacteria and fungi associated with decaying litter of macrophytes that
utilizes only leached dissolved organic matter and only a few of them are involved
in degradation of cell wall polymers of plant detritus (Gaur
1987
).
Thus, free-floating
Eichhornia crassipes
and rooted floating
Ipomoea aquatica
occur throughout year; referred to as macrophytes, constitute an important compo-
nent of aquatic ecosystem. Free-floating water hyacinth is the aquatic weed origi-
nated in the 23.15 % wetland area of North Eastern region of India. At an average
annual productivity of dry (ash-free)
E. crassipes
is 50 t ha
−1
year
−1
. Water hyacinth
is one of the most productive plants in the world attributing the weed to cover water
surfaces faster than most other plants.
4.2.1
Eichhornia crassipes
Eichhornia crassipes
(common name—water hyacinth), is a member of family Pon-
tederiaceae and is most widespread aquatic weed (Fig.
4.1
). It also withstands, under
considerable drought and grows as a land plant. The plant is perennial, floating in water
