Carbon dioxide utilization and seaweed production

Stronger growth in many plants stimulated by increased CO2 concentration should lead to greater biological productivity with an expected increase in the photosynthetic storage of carbon. Thus, the biosphere will serve as a sink for CO2, though it will also act as a source too, because of respiration. Normally net photosynthesis dominates in summer and removes CO2 from the atmosphere, whereas respiration dominates in winter and releases CO2 in the atmosphere. However in the tropics where day length is quite long with about 10+ or –2 hours throughout the year, net photosynthesis is expected to dominate. In this background utilization of CO2 as an industrial by-product for seaweed production holds great promise not only in acting as a significant sink, but also in meeting to some extent global food, fodder, fuel and pharmaceutical requirements, particularly in the tropics. It is interesting to note that 3.5 tons of alga production utilizes 1.27 tons of carbon and about 0.22 tons of nitrogen and 0.03 tons of phosphorus. CO2 can be utilized for stimulating the wild growth of seaweed in the sea or in culture on the shore and also possibilities exist for promoting growth of freshwater algae, fern and other submerged weed particularly Hydrilla, which is a choice feed for many fast growing fish. However, no such scientific studies have been done to evaluate this and quantify the degree of stimulation of growth and enhanced productivity through anthropogenic CO2. Culture and wild harvest of seaweed is commonly practiced in many countries in Japan, North and South Korea, China, Philippines, India and it is coming up in many Asian countries. The common seaweeds harvested and cultured are Porphyra, Undaria, Laminaria, Eucheuma and Gracilaria. Porphyra (purple laver) is the largest of the aquaculture billion-dollar industry in Japan. It is important that under the new initiative of the USA, pilot scale studies undertaken preferably at suitable institutions dealing with mariculture R&D, to evolve a package of practices to obtain optimal harvest of such aquatic weeds with anthropogenic CO2. Considering tropical settings, institutional infrastructure, scientific capabilities and cost effectiveness a network of the institution be selected in different countries and such work should be initiated.