E. crassipescontaining all essential amino acids supplies excellent livestock feed such as pig and chicken although heavy metals absorbed in the plant has to be eliminated for practical applications. For energy uses, 373 m3/tonFW bio-gas containing 60-80% methane and ca. 5,300 kcal/m3 for burning calorie was obtained by anoxic fermentation of E. crassipes. Since E. crassipes contains 3.2% of nitrogen, 0.7% of phosphorus and 2.8% of potassium in total DW, applications for fertilizer and soil amendment agent are now under considered.

Eeel-grass biomass is used as a part of feed of sea pig and manatee in aquaria. Technology of artificial cultivation of eel-grass has not been established yet.

Seaweed biomass has been widely used in the world (Table 2.10.1). Yearly harvesting of attractive seaweeds is ca. 1.3 M (million) tonsFW for brown algae and ca. 0.81 M tonsFW for red algae. Most of them are natural, and artificial cultivation has increased recently. Seaweeds have been used for dried feed, human food, fertilizers, soil amendment agent and so on. Useful materials contained in seaweeds such as unique polysaccharides, iodine and so on are used for raw materials for extracting the useful substances (Indergaard, 1982). Kelp contains alginic acid in 13-45% of DW which is used for producing foods, medicines, cosmetics, dyes, paints, paper manufacturing, interior finishing materials, lubricating oil and so on. Some red algae contain agar and agar-like carrageenan.

Micro-algae contain high percentages of protein reaching 50-70% of DW. Various utilizations of health care supplements, raw materials for extracting pigments such as carotenoids and phycobilins, and vitamins, and feed for aquatic organism are now in business for micro-algae. Due to micro-size and low biomass concentrations in natural, micro-algal biomass is prepared by artificial cultivation in tank, pool or channel on land in low or middle latitudes suitable for year round cultivation. A business model has been proposed to culture filter feeder sea shells fed micro-algae cultured by nutrient rich deep seawater (Roels et al., 1979).