Actual standing stock of E. crassipes and duckweeds has not been estimated yet. Since E. crassipesis actively propagating due to acceleration of eutrophication in various places of low latitudes particularly serious in Africa where large rivers are dammed by the plant, attractive biomass utilization is urgently required.

Standing stock of biomass of natural sea grass bed is 0.1-0.5 kgDW/m2 on average reaching to 2 kgDW/m2 in a dense community. Sea grass bed is decreasing due to environmental changes and land reclamation in the world, and then artificial maintenance and recovery techniques are under challenged. Assuming 0.3 kgDW/m2 of average density and 90% of water content of eel grass, it is expected more than a few 10 Mtons of eel grass biomass in the world.

According to the estimates based upon natural seaweed resources by Jensen (1978, after Indergaard, 1982), demand of alginic acid is 50,000 tons per year which requires 1.30 MtonsFW of seaweed. Yearly demands of carrageenan, agar, “nori, “wakame and kelp are 30,000, 20,000, 35,000, 30,000, 250,000 tons, respectively, and required seaweeds for respective those are 0.40, 0.50, 0.40, 0.20 and 2.00 MtonsFW. These are 1.1-3.0 times compared to the requirements made in the late 1970s. In addition, there are several M tonsFW to several 10 M tonsFW of seaweeds requested for seaweed meal, chemical industry, energy uses and high purity chemical industries, respectively. In order to meet with these large requirements of seaweed, a large increase of seaweed production is requested essentially in coastal areas as well as open seas in the future.

Further information

Hartog, C. den. Seagrasses of the world. North Holland, Amserdam. pp.275 (1970)

Indergaard, M. The aquatic resource. In Biomass utilization (ed. W. A. Cote) Plenum Press, New York, pp.137-168 (1982)

Mann, K. H. Ecology of coastal waters: a systems approach. Univ. Calif. Press, pp.322. (1982)

Roel, O. A.; Laurence, S.; Farmer, M. W.; Hemelryck, L. Van. The utilization of cold, nutrient-rich deep ocean water for energy and mariculture. Ocean Mangement, 5,199-210 (1979).

Slesser, M. and C. Lewis. Biological energy resources. E. & F. N. Spon Ltd., London (1979)