Basically water hyacinth is a aquatic weed and it is very porous with air spaces in its stem and leaves. Therefore, the biomass available from hyacinth is very less even though we find lot much hyacinth in water. When you try to get a resource from it, it is always limited. The other part is you cannot cultivate hyacinth for your resource.
Basically it classified as weed with most of times as problems to the aquatic resources by various factors. besides it is used as a raw material for the production of various products and byproducts too; some of my friends used this to produce, bio-polymer, ethanol production, gasification process so on. i hope the contents of the plant is mostly a organic enriched resource if it is used as bio-manure; since it absorbs most of the nutrients from the water bodies for its nourishment.